JP2011209352A - Optical system and lens positioning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system which easily and accurately adjusts the position of a lens even if a lens is arranged between two lenses with position reference marks formed thereon.SOLUTION: The optical system includes: a first mark lens L2 and a second mark lens L5 with position reference marks M1, M2 formed thereon; and an intermediate lens group LG2 which is arranged between the first mark lens L2 and the second mark lens L5 and comprises at least one lens. In this case, the intermediate lens group LG2 satisfies the following inequality: 0.1<fm/f<2, wherein fm represents the focus distance of the intermediate lens group, and f represents the focus distance of the whole optical system.

Description

  The present invention relates to an optical system and a lens position adjusting method, and more particularly to a technique suitably used for an imaging optical system that forms an object on an imaging surface of a solid-state imaging device.

  In recent years, small-sized imaging devices using solid-state imaging devices such as CCD (Charge Coupled Device) type image sensors and CMOS (Complementary Metal-Oxide Semiconductor) type image sensors have become mobile phones, PDAs (Personal Digital Assistants), etc. On mobile devices.

  In such a small image pickup apparatus, an image pickup optical system including, for example, three to five lenses is used due to a demand for high performance and the like. Here, the imaging optical system is an optical system that forms an image of a subject on the imaging surface of the solid-state imaging device. In such an imaging optical system, for example, as disclosed in Patent Document 1, so-called inner focus type focus adjustment is performed so that an increase in the size of the imaging optical system can be suppressed. There is something.

  Note that an inner focus type imaging optical system disclosed in Patent Document 1 is disposed between a front group (lens group), a rear group (lens group), and a front group and a rear group, and is used for light adjustment for focus adjustment. And a focusing lens that moves on an axis.

  By the way, in such an optical system including a plurality of lenses, alignment is generally performed so that the relative positions between the lenses have a desired positional relationship. As a method for adjusting the relative position between lenses, for example, as shown in Patent Document 2, a method of providing a position reference mark on each lens is known.

  In addition, the position adjustment method in Patent Document 2 is as follows. First, the position reference mark of each lens is optically observed as a feature point. Then, the position of each lens in the observation coordinate system is detected by image processing using a weighted average or the like. Thereafter, at least one of the lenses is moved so that the coordinates of the lenses match, and the relative position between the lenses is adjusted.

JP 2008-76953 A JP 2006-146043 A

  When an imaging optical system as shown in Patent Document 1 is configured, it is conceivable that the front group, the rear group, and the focusing lens are held by separate mechanical components in consideration of, for example, ease of assembly. When an optical system is configured using a plurality of mechanical parts in this way, the relative positional relationship between the lens constituting the front group and the lens constituting the rear group is greatly shifted (according to the optical axis) due to the accumulation of component errors. (The deviation in the vertical direction) is likely to occur. For this reason, it is preferable to perform position adjustment for correcting the shift of the relative position between the lens constituting the front group and the lens constituting the rear group.

  As a method for adjusting the position between the lens constituting the front group and the lens constituting the rear group, a method using the above-described position reference mark is conceivable. However, a focusing lens is disposed between the front group and the rear group. If so, the following problems arise. That is, if the center position of the focusing lens arranged between the front group and the rear group is shifted (eccentric) in a direction perpendicular to the optical axis, this eccentricity is the cause. An image of the position reference mark observed through the focusing lens may be observed with a large deviation from the original position. Even if position adjustment is performed using the position reference mark in such a state, the lens constituting the front group and the lens constituting the rear group cannot be set to the correct relative positions.

  If the relative position between the focusing lens and the lens constituting the front group or the lens constituting the rear group is adjusted first, the occurrence of the above-described problem can be suppressed. However, it is troublesome to adjust the relative positions of all the lenses constituting the optical system, and it may cause a complicated configuration of the imaging optical system, which is not necessarily a preferable method.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical system and a lens position adjusting method capable of easily and accurately adjusting a lens position even when a lens is further arranged between two lenses provided with a position reference mark. That is.

In order to achieve the above object, an optical system according to the present invention includes a first mark lens and a second mark lens having a lens surface provided with a position reference mark, the first mark lens, and the second mark. And an intermediate lens group including at least one lens disposed between the lenses, wherein the intermediate lens group satisfies the following conditional expression.
0.1 <fm / f <2
Here, fm is the focal length of the intermediate lens group, and f is the focal length of the entire optical system.

  In this configuration, the focal length fm of the intermediate lens group disposed between the two lenses provided with the position reference marks is appropriately set according to a predetermined conditional expression. That is, by falling below the upper limit of the conditional expression, the refractive power of the intermediate lens group is appropriately maintained without becoming too weak, and the total length of the optical system can be shortened (downsized). Further, by exceeding the lower limit of the conditional expression, the refractive power of the intermediate lens group does not become too strong, and the above-described image shift of the position reference mark caused by the eccentricity of the intermediate lens group can be suppressed to a small value. Therefore, according to this configuration, the relative position between the two marked lenses can be adjusted easily and accurately even though a lens is further arranged between the two lenses marked with the position reference mark. In addition, it is possible to satisfy the demand for miniaturization of the optical system.

In addition, it is more preferable that the focal length fm of the intermediate lens group satisfies the following conditional expression.
0.5 <fm / f <1.5
Here, fm is the focal length of the intermediate lens group, and f is the focal length of the entire optical system.

  The optical system configured as described above is used as an imaging optical system that forms an image of a subject on an imaging surface of a solid-state imaging device, and is composed of at least one lens in order from the object side to the image side. , A second lens group, a third lens group, the first lens group includes the first mark lens, the second lens group is the intermediate lens group, and the third lens group is the second lens group. The mark lens may be included.

  According to this configuration, there is provided an imaging optical system that is a small and high-performance imaging optical system that can quickly incorporate the lens into the correct relative position using a lens that is provided with a position reference mark during assembly. Is possible.

  In the optical system configured as described above, the first lens group and the third lens group may be fixed with respect to the imaging surface, and the second lens group may be movable in the optical axis direction.

  According to this configuration, a so-called inner focus type imaging optical system, which is a compact imaging optical system capable of quickly incorporating a lens at a correct relative position using a lens with a position reference mark at the time of assembly. Can be provided.

  In the optical system having the above-described configuration, the position reference mark may be provided on a lens center, or the position reference mark may be provided on an edge portion formed on the outer periphery of the lens.

  Generally, if a position reference mark is provided at the lens center, the mark tends to be easily observed. However, there may be a case where it is not desired to provide the position reference mark at the lens center. In such a case, the position reference mark is provided at the edge portion (referring to a portion provided around the effective portion of the lens). Also good.

  In order to achieve the above object, a lens position adjusting method according to the present invention is a lens position adjusting method in the optical system having the above-described configuration, wherein the first mark lens and the second mark lens are aligned along the optical axis direction. The position adjustment is performed so that both the position reference marks coincide with each other.

  According to this configuration, since it is possible to adjust the lens position using the position reference mark while suppressing the influence due to the eccentricity of the intermediate lens group disposed between the first lens mark and the second lens mark, It is possible to efficiently adjust the lens position in the optical system.

  According to the present invention, the position of the two lenses can be easily and accurately adjusted despite the fact that a lens is further disposed between the two lenses that are marked for position adjustment. Moreover, in obtaining such a configuration, the demand for downsizing of the optical system can be satisfied.

Schematic perspective view showing a configuration of an optical unit including the imaging optical system of the present embodiment Schematic exploded perspective view showing the configuration of an optical unit including the imaging optical system of the present embodiment Schematic sectional view of an optical unit including the imaging optical system of the present embodiment The flowchart which shows the assembly procedure of the imaging optical system of this embodiment Schematic sectional view showing a state (first state) during assembly of the imaging optical system of the present embodiment Schematic sectional view showing a state (second state) during assembly of the imaging optical system of the present embodiment FIG. 5 is a schematic cross-sectional view showing a state during the assembly of the imaging optical system of the present embodiment, and is a diagram for explaining a first lens alignment process; The top view of the 1st lens holder of this embodiment when it sees from the top, and the figure showing the state where the 1st lens was inserted in the holder Configuration diagram of the imaging optical system of Example 1 Configuration diagram of the imaging optical system of Example 2 Configuration diagram of the imaging optical system of Example 3 Configuration diagram of the imaging optical system of Example 4 Configuration diagram of image pickup optical system of Embodiment 5 Configuration diagram of the imaging optical system of Example 6 Configuration diagram of the imaging optical system of Example 7 Configuration diagram of imaging optical system of embodiment 8 Aberration diagram of Example 1 at infinity object distance Aberration diagram of Example 2 at object distance at infinity Aberration diagram of Example 3 at infinity object distance Aberration diagram of Example 4 at infinity object distance Aberration diagram of Example 5 at infinity object distance Aberration diagram of Example 6 at infinity object distance Aberration diagram of Example 7 at infinity object distance Aberration diagram of Example 8 at infinity object distance

  Hereinafter, embodiments of an optical system and a lens position adjusting method of the present invention will be described in detail with reference to the drawings. In the following, the case where the present invention is applied to a single-focus imaging optical system that forms an image of a subject on the imaging surface of a solid-state imaging device will be described as an example.

(Configuration of imaging optical system)
First, the configuration of the imaging optical system of the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic perspective view illustrating a configuration of an optical unit including an imaging optical system according to the present embodiment. FIG. 2 is a schematic exploded perspective view showing a configuration of an optical unit including the imaging optical system of the present embodiment. FIG. 3 is a schematic cross-sectional view of an optical unit including the imaging optical system of the present embodiment.

  As shown in FIG. 2, the optical unit 10 including the imaging optical system 1 (see FIGS. 1 and 3) of the present embodiment is roughly divided into a first group unit G1, a second group unit G2, and a third group unit G3. The actuator unit A1 is provided.

  The first unit G1, in order from the object side to the image side, includes a first light shielding plate 11 made of a donut-shaped disk component, a first lens L1, and a second light shielding plate 12 made of a donut-shaped disk component. , And the second lens L2, which are held by a first lens holder (holding member) 13. That is, in the present embodiment, the first lens group LG1 is formed by the first lens L1 and the second lens L2. The first lens holder 13, which is a bottomed plate-shaped member having a substantially disk shape in plan view, has a lens holding space 13a for holding the first lens group LG1 in the thickness direction. In addition, an opening 13 b for allowing light to pass through is formed at the bottom of the first lens holder 13.

  The first group unit G1 (first lens group LG1) is an imaging surface 70a of a solid-state imaging device 70 (for example, a CCD type image sensor, a CMOS type image sensor, etc .; indicated by a broken line in FIG. 3) attached to the optical unit 10. It is fixed so as not to move. The first lens L1 is a positive lens, the second lens is a negative lens, and the first lens group LG1 including the first lens L1 and the second lens L2 has a positive refractive power as a whole.

  The number of lenses and the refractive power (power) constituting the first lens group LG1 (lens group provided in the first group unit G1) are merely examples, and may be changed as appropriate. However, the lens on the most object side is preferably a positive lens, and the first lens group LG1 (which may be a single lens) preferably has a positive refractive power as a whole. In order to effectively correct the spherical aberration and the axial chromatic aberration, it is preferable that the first lens group LG1 includes at least one positive lens and at least one negative lens.

  A position reference mark M1 is formed at a substantially central portion of the object-side surface of the second lens L2 included in the first lens group LG1, as shown in an enlarged view in FIG. That is, the second lens L2 is a mark lens provided with a position reference mark, and is an embodiment of the first mark lens of the present invention. In the present embodiment, the position reference mark M1 is obtained by providing a depression (recess) on the lens surface. Such a position reference mark M1 may be obtained, for example, by cutting the lens surface, or may be obtained by providing a protrusion on a mold for manufacturing the lens.

  The configuration of the position reference mark M1 is not limited to the configuration of the present embodiment. For example, the position reference mark M1 may be obtained by providing a convex portion on the lens surface, or may be a dot obtained by using an inkjet or the like. There may be. In the present embodiment, the position reference mark M1 is provided on the object side surface, but may be provided on the image side surface. In addition, the position reference mark M1 is preferably formed as small as possible so as not to affect the optical performance of the imaging optical system 1 within a range in which the function as a marker is exhibited.

  The second group unit G2 includes, in order from the object side to the image side, a third lens L3, a third light-shielding plate 21 made of a donut-shaped disk component, and a fourth lens L4, which are a second lens holder. (Holding member) 22 is configured to be held. That is, in the present embodiment, the second lens group LG2 is formed by the third lens L3 and the fourth lens L4. The second lens group LG2 corresponds to an embodiment of the intermediate lens group of the present invention. The second lens holder 22 has a cylindrical through space 22a, and the second lens group LG2 is held in the through space 22a.

  The second group unit G2 (second lens group LG2) can be moved in the optical axis direction (reference numeral AX in FIG. 3 is the optical axis) by an actuator unit A1 described later in detail. That is, the imaging optical system 1 of the present embodiment employs a so-called inner focus method. The second lens group LG2 (lens group provided in the second group unit G2) is configured to have a positive refractive power as a whole.

  The number of lenses constituting the second lens group LG2 is not limited to the configuration (two) in the present embodiment, and may be one or three or more. When the second lens group LG2 is composed of two lenses, for example, the third lens L3 and the fourth lens L4 are both positive lenses, the third lens L3 is a negative lens, and the fourth lens L4 is a positive lens. It's okay.

  The third group unit G3 includes, in order from the object side to the image side, a fifth lens L5, for example, a filter member 42 made of a parallel plate such as an IR cut filter or an optical low-pass filter, and these are the first frame (holding). Member) 41. The first frame 41 has a space 41a penetrating in the thickness direction so that light can pass in the thickness direction. The third group unit G3 (the third lens group LG3 including the fifth lens L3) is fixed so as not to move with respect to the imaging surface 70a of the solid-state imaging device 70 attached to the optical unit 10, similarly to the first group unit G1. State.

  In the present embodiment, the third lens group LG3 is formed only by the fifth lens L5, which is a negative lens, but the present invention is not limited to this. That is, the third lens group LG3 may be composed of a plurality of lenses, and may have a positive refractive power or a negative refractive power as a whole. However, it is preferable that the third lens group LG3 includes a negative lens, thereby obtaining a so-called telephoto type configuration and shortening the overall length of the imaging optical system 10 (a reduction in size and height). .

  A position reference mark M2 is formed at a substantially central portion of the object-side surface of the fifth lens L5 included in the third lens group LG3 as shown in an enlarged view in FIG. That is, the fifth lens L5 is a mark lens provided with a position reference mark, and is an embodiment of the second mark lens of the present invention. In the present embodiment, the position reference mark M2 provided on the fifth lens L5 is obtained by providing a recess (concave portion) on the lens surface. The method of forming the position reference mark M2 and the points to be noted are the same as those of the position reference mark M1 provided on the second lens L2. Further, the position reference mark M2 provided on the fifth lens L5 may be changed to another configuration (such as a convex portion or a dot) as in the case of the position reference mark M1 provided on the second lens L2.

  The actuator unit A1 is a drive mechanism that allows the second group unit G2 (second lens group LG2) to move in the optical axis direction so that the imaging optical system 1 is an inner focus type. The actuator unit A1 is configured using an ultrasonic linear actuator called a SIDM (Smooth Impact Drive Mechanism; registered trademark) actuator 31, which is suitable for miniaturization. For example, the present applicant has previously proposed this actuator in Japanese Patent Application Laid-Open No. 2001-268951.

  As shown in FIG. 3, the SIDM actuator 31 is bonded and fixed to one end of the SIDM shaft 31a and the SIDM shaft 31a arranged so that the axial direction is parallel to the optical axis direction, and expands and contracts in the axial direction of the SIDM shaft 31a. And a weight 31c that is bonded and fixed to the end of the piezoelectric element 31b opposite to the side to which the SIDM shaft 31a is bonded and fixed. As shown in FIG. 2, a lead wire 32 and a terminal 33 for driving the piezoelectric element 31b are attached to the SIDM actuator 31 by soldering.

  When the SIDM actuator 31 is driven, a drive signal is given to the piezoelectric element 31 b via the terminal 33 and the lead wire 32. When a drive signal is applied, the piezoelectric element 31b expands and contracts, and the SIDM shaft 31a vibrates in the axial direction due to the expansion and contraction. By appropriately controlling the vibration waveform at this time, the second lens holder 22 that is frictionally engaged with the SIDM shaft 31a (this engagement is realized by the leaf spring 23) is moved in the target direction (FIG. 3). (Upward direction or downward direction). For this reason, the SIDM actuator 31 can move the second lens group LG2 in the optical axis direction. The weight 31c is provided for the purpose of generating displacement due to expansion and contraction of the piezoelectric element 31b only on the side of the SIDM shaft 31a.

  By combining the first group unit G1, the second group unit G2, the third group unit G3, and the actuator unit A1 in combination with the second frame 50 and the cover 60, the single focus / inner focus type imaging of the present embodiment is performed. The optical system 1 (optical unit 10) is obtained. Details of the assembly of the imaging optical system 1 (optical unit 10) will be described later.

  In the present embodiment, the five lenses L1 to L5 constituting the imaging optical system 1 are all made of a plastic material. Of course, you may comprise these lenses L1-L5 with glass. However, in the imaging optical system 1 of the present embodiment, considering that the curvature radii and outer diameters of the lenses L1 to L5 are considerably small and are not suitable for mass production if glass lenses are used, the lenses are made of plastic. It is made of material.

  Here, points to be noted when the lens constituting the imaging optical system 1 is formed of a plastic material will be described. Since the plastic material has a large refractive index change at the time of temperature change, if all the lenses are made of plastic lenses as in this embodiment, the image point position of the imaging optical system 1 fluctuates when the ambient temperature changes. It will have a problem of end. Recently, however, it has been found that mixing inorganic fine particles in a plastic material can reduce the effect of temperature changes on the plastic material.

More specifically, mixing fine particles with a transparent plastic material generally causes scattering of light and lowers the transmittance, making it difficult to use as an optical material. By making the wavelength smaller than this, scattering can be substantially prevented from occurring. In addition, the refractive index of the plastic material decreases as the temperature increases, but the refractive index of the inorganic particles increases as the temperature increases. Therefore, it is possible to make almost no change in the refractive index by using these temperature dependencies so as to cancel each other. Specifically, by dispersing inorganic particles having a maximum length of 20 nanometers or less in a plastic material as a base material, a plastic material with extremely low temperature dependency of the refractive index can be obtained. For example, by dispersing fine particles of niobium oxide (Nb ₂ O ₅ ) in an acrylic resin, a change in refractive index due to a temperature change can be reduced.

  In the imaging optical system 1, the temperature of the imaging optical system 1 is obtained by using a plastic material in which such inorganic particles are dispersed in a positive lens (for example, the first lens L1) having a relatively large refractive power or all the lenses. It is possible to suppress the image point position fluctuation at the time of change to be small.

By the way, in this embodiment, the imaging optical system 1 is comprised so that the following conditional expression (1) may be satisfy | filled.
0.1 <fg2 / f <2 (1)
Here, fg2 is the focal length of the second lens group LG2, and f is the focal length of the entire imaging optical system 1.

In the present embodiment, as a desirable mode, the imaging optical system 1 is configured to satisfy the following conditional expression (2).
0.1 <f1 / fg2 <2 (2)
Here, f1 is the focal length of the first lens L1 (the most object side positive lens).

  As described above, the configuration satisfying the conditional expressions (1) and (2) corrects the eccentricity (shift in the direction perpendicular to the optical axis AX) generated in the lenses L1 to L5 constituting the imaging optical system 1. This is a device for facilitating the adjustment work for obtaining (obtaining good optical characteristics). Details of this will be described in a method for assembling the imaging optical system 1 (optical unit 10) described below.

(Assembly method of imaging optical system)
Next, a method for assembling the imaging optical system 1 (optical unit 10) including the lens position adjusting method of the present invention will be described in detail. FIG. 4 is a flowchart showing an assembling procedure of the imaging optical system of the present embodiment. Hereinafter, assembly of the imaging optical system 1 will be described with reference to FIG.

  First, the first group unit G1 is assembled (step S1). Specifically, the second lens L2 and the second light shielding plate 12 are incorporated in the first lens holder 13 in this order. At this time, the second lens L2 is bonded and fixed to the first lens holder 13. At this stage, the first lens L1 and the first light shielding plate 11 are not incorporated into the first lens holder 13.

  Next, the second group unit G2 is assembled (step S2). Specifically, the fourth lens L4, the third light shielding plate 21, and the third lens L3 are incorporated in the second lens holder 22 in this order. At this time, by applying an adhesive 80 between the third lens L3 and the second lens holder 22, the fourth lens L4, the third light-shielding plate 21, and the third lens L3 are collectively put into the second lens L3. The lens holder 22 is fixed.

  Next, the third group unit G3 is assembled (step S3). Specifically, the fifth lens L5 and the filter member 42 are incorporated in the first frame 41. The fifth lens L5 and the filter member 42 are assembled into the first frame 41 from different directions (for example, from the top and bottom in FIG. 3). These incorporated members are each bonded and fixed to the first frame 41 with an adhesive 80.

  Next, assembly of the actuator unit A1 is performed (step S4). More specifically, one end of the SIDM shaft 31a and one end of the piezoelectric element 31b are bonded and fixed, and the other end of the piezoelectric element 31b and one end of the weight 31c are bonded and thereby the SIDM actuator 31 is formed. One end of a lead wire 32 is soldered to each of a pair of electrodes provided on the piezoelectric element 31 b, and a terminal 33 is soldered to the other end of each lead wire 32.

  Note that the assembly process of steps S1 to S4 is not limited to the order shown here, and may be performed in a different order, or steps S1 to S4 may be performed simultaneously in parallel.

  Next, the actuator unit A1 is attached to the third group unit G3 (step S5). Specifically, the lead wire 32 is wound around the fifth lens L5 mounted on the first frame 41, and the terminal 32 is clipped to a predetermined position (see FIG. 1) of the first frame 41. It is almost fixed by the method. At this point, the SIDM actuator 31 is provided in the vicinity of one of the four corners of the first frame 41 provided in a substantially rectangular shape in plan view. However, it is not fixed yet, although it is arranged so that its axial direction is substantially parallel to the optical axis AX.

  Next, the second group unit G2 is engaged with the actuator unit A1 (step S6). Specifically, the second group unit G2 is provided in the vicinity of one corner of the second lens holder 22 constituting the second group unit G2 (in the vicinity of the corner substantially above the actuator support portion 41b) and in a substantially square shape. The plate spring member 23 is disposed so as to sandwich the SIDM shaft 32a with the tip of one side. Here, the leaf spring member 23 is attached to a boss 22b (see FIG. 2) provided on the second lens holder 22 so that a bending point of a substantially U-shape corresponding to the substantially central portion of the leaf spring member 23 is swingable. It is attached so that the tip of the other side of the letter A comes into contact with the second lens holder 22. Thus, the second group unit G2 is engaged with the SIDM shaft 31a with a predetermined frictional force and is movable in the axial direction.

  Next, the second frame 50 is attached to the first frame 41 (step S7). Specifically, the second frame 50 having a box shape (however, an opening 50a for allowing light to pass through is provided on the upper surface) is configured to be covered with the actuator unit A1 and the second group unit G2. It is attached to the first frame 41. A snap fit mechanism is provided between the first frame 41 and the second frame 50, and the relative position in the optical axis direction of both is fixed without using an adhesive. The relative position in the direction perpendicular to the optical axis AX is fixed by a positioning pin and a positioning hole engaged therewith. Further, by attaching the second frame 50, the terminal 33 of the actuator unit A1 is sandwiched between the first frame 41 and the second frame 50 and completely fixed. FIG. 5 (cross-sectional view) shows the state (first state) at the end of step S7.

  When the second frame 50 is attached to the first frame 41, the tip of the SIDM shaft 31a of the actuator unit A1 is fitted in a fitting hole 50b provided on the upper surface of the second frame 50. . At this time, the weight 31c is not bonded and fixed.

  Next, the inclination of the second lens group LG2 (second group unit G2) is adjusted (step S8). Specifically, the inclination of the second lens group LG2 is adjusted by adjusting the position of the weight 31c in a plane perpendicular to the optical axis AX. More specifically, for example, the imaging surface 70a of the solid-state imaging device 70 is arranged in parallel with the imaging surface 70a (the solid-state imaging device 70 is not attached at this stage, and is assumed to be attached). Inclination is adjusted using, for example, an autocollimator or the like so that the reference surface and the edge surface outside the effective surface of the third lens L3 are parallel to each other. At the stage where this tilt adjustment is performed, the weight 31 c is bonded and fixed to the first frame 41 with the adhesive 80.

  Next, the first group unit G1 (the first lens L1 is not incorporated) is attached to the second frame 50 (step S9). Specifically, the position reference mark M1 applied to the second lens L2 and the position reference mark M2 applied to the fifth lens L5 coincide with each other in the position of the first lens holder 13 constituting the first group unit G1. After the adjustment (corresponding to the lens position adjustment of the present invention) as described above, the first lens holder 13 is bonded and fixed to the second frame 50. A state (second state) at the end of step S9 is shown in FIG. 6 (cross-sectional view).

  The lens position adjustment performed so that the position reference mark M1 and the position reference mark M2 coincide may be performed while simultaneously observing the two marks M1 and M2 along the optical axis direction, for example. Also, for example, by observing the two position reference marks M1 and M2 separately along the optical axis direction, the positions of the marks M1 and M2 in the observation coordinate system are obtained separately, and based on the obtained coordinate positions. Then, the position of the second lens L5 (the position of the first lens holder 13) may be moved so that the positions of the two coincide.

  By the way, as described above, in the imaging optical system 1 of the present embodiment, the first lens group LG1, the second lens group LG2, and the third lens group LG3 are mounted on separate mechanical components. In the case of such a configuration, a large shift (shift in a direction perpendicular to the optical axis AX) easily occurs in the relative positional relationship between the first lens group LG1 and the third lens group LG3 due to the accumulation of component errors. . Such misalignment may make it difficult to obtain good optical characteristics during the final optical adjustment of the imaging optical system 1 (optical adjustment using a solid-state imaging device). For this reason, it is desirable to eliminate the shift of the relative position due to the accumulation of component errors. For this reason, in this embodiment, lens position adjustment is performed using the position reference marks M1 and M2 so that the second lens L2 and the fifth lens L5 are in the correct relative positions.

  Here, in the configuration of the present embodiment in which the second lens group LG2 exists between the second lens L2 and the fifth lens L5, if the second lens group LG2 is decentered, An image of the position reference mark M2 observed through the two lens group LG2 (a virtual image in this embodiment, but may be a real image in a different configuration) may be observed with a large deviation from the original position. . In such a state, even if the lens position adjustment using the position reference marks M1 and M2 is performed, the lens cannot be in the correct relative position. For this reason, in the present embodiment, the imaging optical system 1 is configured to satisfy the conditional expression (1) so that the second lens group LG2 is hardly affected even when the second lens group LG2 is in an eccentric state. It is doing.

  Specifically, by configuring so as to exceed the lower limit of conditional expression (1), the refractive power of the second lens group LG2 does not become too strong, and the above-described position reference mark caused by the eccentricity of the second lens group LG2 The image shift of M2 can be suppressed small. The reason why the lower limit of the conditional expression (1) is satisfied is that the refractive power of the second lens group LG2 is appropriately maintained without becoming too weak, thereby shortening the total length of the imaging optical system 1. This is the purpose.

The imaging optical system 1 is more preferably configured to satisfy the following conditional expression (1) ′.
0.5 <fg2 / f <1.5 (1) ′

  Returning to FIG. 4, when step S <b> 9 is completed, the first lens L <b> 1 (the positive lens disposed on the most object side) is fixed to the first lens holder 13 (step S <b> 10). The first lens L1 is moved in a direction perpendicular to the optical axis AX before being fixed to the first lens holder 13, and its position is adjusted for optical adjustment (alignment process). Hereinafter, this alignment step will be described with reference to FIG. FIG. 7 is a schematic cross-sectional view showing a state during the assembly of the imaging optical system of the present embodiment, and is a view for explaining the alignment process of the first lens.

  Prior to the alignment step, as shown in FIG. 7, the solid-state imaging device 70 is disposed behind the first frame 41. The solid-state imaging device 70 may be an adjustment device prepared for optical adjustment or may be used as a product. When used as a product, the solid-state image sensor 70 may be fixed to the first frame 41 at this stage.

  When the solid-state image sensor 70 is arranged, the first lens L1 held by the jig is replaced with the lens holding space 13a of the first lens holder 13 in which the second lens L2 and the second light shielding plate 12 are incorporated (see FIG. 2). ) To be pressed against the previously incorporated member. Then, while monitoring the optical characteristics obtained by the solid-state imaging device 70, the first lens L1 is moved in a direction perpendicular to the optical axis AX, and alignment is performed so that preferable optical characteristics are obtained. When a position where favorable optical characteristics can be obtained is found, the adhesive 80 is cured by ultraviolet irradiation, and the first lens L1 is fixed in the first lens holder 13.

  Here, the configuration of the first lens holder 13 will be additionally described with reference to FIG. FIG. 8 is a schematic plan view of the first lens holder according to the present embodiment as viewed from above. The first lens is inserted into the holder (lens holding space 13a (see FIG. 2)). Show.

  As shown in FIG. 8, on the outer peripheral side of the first lens holder 13, there are three adhesive filling portions 13c filled with an adhesive for adhering the first lens L1 from the side surface at equal intervals in the circumferential direction. Is provided. Further, three space portions 13d are provided at equal intervals in the circumferential direction so as to sandwich the adhesive filling portion 13c. By this space portion 13d, the first lens L1 inserted into the lens holding space 13a can be held by a jig. The diameter of the lens holding space 13a (size in the direction perpendicular to the optical axis AX) is larger than the diameter of the first lens L1. For this reason, a gap SP is formed in a state where the first lens L1 is inserted into the lens holding space 13a, and the first lens L1 can be moved in a direction perpendicular to the optical axis AX.

  Incidentally, as described above, the imaging optical system 1 of the present embodiment employs the inner focus method. In the imaging optical system 1 that employs the inner focus method, a mechanism that moves in the optical axis direction for focus adjustment is provided, so that the number of mechanical parts increases, and the center position of the lens is in a direction perpendicular to the optical axis. The eccentricity is likely to occur. An imaging optical system configured to satisfy the demands for miniaturization and high performance is susceptible to an adverse effect (for example, one-sided blur) due to eccentricity generated during manufacturing. For this reason, when the imaging optical system 1 is assembled, alignment (optical adjustment) is performed in order to correct the influence of eccentricity. Although correction of the relative arrangement of the lenses is performed by the lens position adjustment (see step S9), it is not always perfect, and it is preferable to perform alignment in order to obtain stable quality.

  The alignment can be performed by moving a plurality of lenses. However, in order to perform the alignment efficiently, in the present embodiment, only the first lens L1 (the positive lens arranged on the most object side) is moved. It is configured. In consideration of the fact that alignment can be performed accurately and efficiently, the imaging optical system 1 is configured to satisfy the conditional expression (2).

  Specifically, by configuring so as to exceed the lower limit of conditional expression (2), it is possible to prevent the focal length of the first lens L1 relative to the second lens group LG2 from becoming too short. Thereby, it is possible to prevent the adjustment accuracy from deteriorating due to the sensitivity of the change in the optical performance with respect to the movement of the first lens L1 (movement for alignment). Further, by falling below the upper limit of conditional expression (2), the focal point of the first lens L1 with respect to the second lens group LG2 is prevented from becoming too long. As a result, it is possible to prevent the amount of movement of the first lens L1 from being too large in order to correct the eccentricity of the second lens group LG2 (for alignment), and the adjustment operation can be performed quickly. Further, by making the value lower than the upper limit of the conditional expression (2), it is possible to prevent the imaging optical system 1 from being enlarged in the lens radial direction (direction perpendicular to the optical axis direction).

  Note that when the first lens L1 is attached (when the alignment process is performed), the position of the first lens L1 in the optical axis direction may be adjusted together. Thereby, it is possible to improve performance not only for one-sided blur but also for field curvature. In addition, after the first lens L1 is attached (after the alignment process), the first lens holder 13 (that is, the first lens group LG1) is moved in the optical axis direction, so that not only one blur but also the field curvature You may make it aim at improvement. In this case, in step S9, the first lens holder 13 should not be bonded and fixed, and the first lens holder 13 must be held with the adjusting jig.

  Returning to FIG. 4 again, when step S10 is completed, the first light shielding plate 11 is attached to the first lens L1. Further, the cover 60 is placed on the first frame 41 from above to serve also as a countermeasure for electromagnetic wave leakage (step S11). A snap-fit mechanism is provided between the cover 60 and the first frame 41, and the cover 60 is attached to the first frame 41 without being bonded and fixed.

  As described above, the imaging optical system 1 (optical unit 10) of the present embodiment is obtained. Next, a preferred embodiment of the imaging optical system 1 will be described.

(Example)
Hereinafter, a preferred embodiment of the imaging optical system 1 will be specifically described with reference to construction data and the like. The configuration (lens configuration) of the imaging optical system of Examples 1 to 8 (EX1 to 8) is shown in FIGS. 9 to 16 are optical cross-sectional views when the imaging optical system 1 is in an infinitely focused state. Further, the movement of the focus group (second lens group LG2) during focusing from infinity to the closest distance is indicated by an arrow mF.

  In Examples 1 to 8, the position reference mark M1 is provided on the second lens L2, and in Examples 1 to 5 and 8 (5 lenses), the position reference mark M2 is provided on the fifth lens L5. For 7 (four lenses), the fourth lens L4 is provided with a position reference mark M2 on the lens surface. These marks are provided so that the influence on the optical performance can be almost ignored. The presence of the mark is not taken into consideration in the lens configuration.

In the construction data of each embodiment, as surface data, in order from the left column, the surface number, the radius of curvature r (mm), the shaft upper surface distance d (mm), and the variable distance at the time of focusing are the closest object distance (object The distance between axis top surfaces dm (mm) at a distance of 10 cm, the refractive index nd with respect to the d line (wavelength: 587.56 nm), the Abbe number vd with respect to the d line, and the effective radius (mm) are shown. The surface with * in the surface number is an aspherical surface, and the surface shape is defined by the following formula (AS) using a local orthogonal coordinate system (X, Y, Z) with the surface vertex as the origin. . As aspheric data, an aspheric coefficient or the like is shown. It should be noted that the coefficient of the term not described in the aspherical data of each example is 0, and E−n = × 10 ⁻ⁿ for all data.

…(AS)

… (AS)

However,
h: height in the direction perpendicular to the X axis (optical axis AX) (h ² = Y ² + Z ² ),
X: sag amount in the direction of the optical axis AX at the position of height h (based on the surface vertex),
R: Reference radius of curvature (corresponding to the radius of curvature r),
K: conic constant,
Ai: i-th order aspheric coefficient,
It is.

  As various data, the focal length (f, mm), F number (Fno.), Half angle of view (ω, °) of the entire system (whole optical system), diagonal length (2Y ′, mm; Y ′: maximum image height), back focus (fB, mm), entrance pupil position (ENTP, distance from first surface to entrance pupil position, mm), exit pupil position (EXTP, exit pupil from imaging surface 70a) Distance to position, mm), front principal point position (H1, distance from first surface to front principal point position, mm), rear principal point position (H2, distance from final surface to rear principal point position, mm). Regarding the focal length and F number of the entire system, values in both the focus state at the infinity object distance (object distance: ∞) and the closest object distance (object distance: 10 cm) are shown. The back focus fB represents the distance from the image side surface of the parallel plate PT (same as the filter member 42) to the image plane IM (same as the imaging surface 70a). Furthermore, the focal length of each lens and each lens group is shown as single lens data and lens group data. Table 1 shows values of the examples corresponding to the respective conditional expressions (conditional expressions (1) and (2)).

  FIGS. 17 to 24 are aberration diagrams of Examples 1 to 8 (EX1 to 8) at an infinite object distance (object distance: ∞). 17A to 24B, (A) is a spherical aberration diagram, (B) is an astigmatism diagram, and (C) is a distortion diagram. The spherical aberration diagram shows the amount of spherical aberration for the d-line (wavelength 587.56 nm) indicated by the solid line and the amount of spherical aberration for the g-line (wavelength 435.84 nm) indicated by the broken line in the optical axis AX direction from the paraxial image plane. The amount of deviation (unit: mm) is represented, and the vertical axis represents a value obtained by normalizing the incident height to the pupil by the maximum height (that is, relative pupil height). In the astigmatism diagram, the broken line T represents the tangential image surface with respect to the d line, and the solid line S represents the sagittal image surface with respect to the d line, expressed as a deviation amount (unit: mm) in the optical axis AX direction from the paraxial image surface. The vertical axis represents the image height (IMG HT, unit: mm). In the distortion diagrams, the horizontal axis represents distortion (unit:%) with respect to the d-line, and the vertical axis represents image height (IMG HT, unit: mm). Note that the maximum value of the image height IMG HT corresponds to the maximum image height Y ′ on the image plane IM (half the diagonal length of the imaging surface 70a of the solid-state imaging device 70).

  The imaging optical system 1 of Embodiment 1 (see FIG. 9) includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a positive third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When each lens is viewed with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is on the object side. The fourth lens L4 is a positive meniscus lens convex to the image side, and the fifth lens L5 is a negative meniscus lens concave to the image side. In addition, the first lens L1 and the second lens L3 have a positive refractive power as a whole, the first lens group LG1, and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole, a second lens group LG2. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.

  The imaging optical system 1 of Embodiment 2 (see FIG. 10) includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a positive third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When each lens is viewed with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is on the object side. The fourth lens L4 is a positive meniscus lens convex to the image side, and the fifth lens L5 is a negative meniscus lens concave to the image side. In addition, the first lens L1 and the second lens L3 have a positive refractive power as a whole, the first lens group LG1, and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole, a second lens group LG2. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.

  The imaging optical system 1 (see FIG. 11) of Example 3 includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a positive third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When each lens is viewed with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is on the object side. The fourth lens L4 is a positive meniscus lens convex to the image side, and the fifth lens L5 is a negative meniscus lens concave to the image side. In addition, the first lens L1 and the second lens L3 have a positive refractive power as a whole, the first lens group LG1, and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole, a second lens group LG2. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.

  The imaging optical system 1 (see FIG. 12) of Example 4 includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a negative third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When viewing each lens with a paraxial surface shape, the first lens L1 is a positive meniscus lens convex on the object side, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is The negative meniscus lens is concave on the image side, the fourth lens L4 is a positive meniscus lens convex on the image side, and the fifth lens L5 is a negative meniscus lens concave on the image side. In addition, the first lens L1 and the second lens L3 have a positive refractive power as a whole, the first lens group LG1, and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole, a second lens group LG2. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.

  The imaging optical system 1 of Embodiment 5 (see FIG. 13) includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a negative third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When each lens is viewed with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is on the image side. A concave negative meniscus lens, the fourth lens L4 is a biconvex positive lens, and the fifth lens L5 is a negative meniscus lens concave on the image side. In addition, the first lens L1 and the second lens L3 have a positive refractive power as a whole, the first lens group LG1, and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole, a second lens group LG2. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.

  The imaging optical system 1 (see FIG. 14) of Example 6 includes, in order from the object side, an aperture stop ST, a positive first lens L1, a negative second lens L2, a positive third lens L3, and a negative 4th lens L4, and all the lens surfaces are aspherical surfaces. When viewing each lens with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is biconvex. The fourth lens L4 is a negative meniscus lens that is concave on the image side. The first lens L1 and the second lens L3 as a whole have a first lens group LG1 having a positive refractive power, the third lens L3 has a second lens group LG2 as a whole having a positive refractive power, and a fourth lens. L4 constitutes a third lens group LG3 having a negative refractive power as a whole.

  The imaging optical system 1 according to the seventh embodiment (see FIG. 15) includes, in order from the object side, an aperture stop ST, a positive first lens L1, a negative second lens L2, a positive third lens L3, and a negative 4th lens L4, and all the lens surfaces are aspherical surfaces. When each lens is viewed with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is on the image side. The fourth lens L4 is a negative meniscus lens that is concave on the image side. The first lens L1 and the second lens L3 as a whole have a first lens group LG1 having a positive refractive power, the third lens L3 has a second lens group LG2 as a whole having a positive refractive power, and a fourth lens. L4 constitutes a third lens group LG3 having a negative refractive power as a whole.

  The imaging optical system 1 of Embodiment 8 (see FIG. 16) includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a positive third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When viewing each lens with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is biconvex. The fourth lens L4 is a positive meniscus lens convex on the image side, and the fifth lens L5 is a negative meniscus lens concave on the image side. In addition, the first lens L1 and the second lens L3 have a positive refractive power as a whole, the first lens group LG1, and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole, a second lens group LG2. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.

Example 1
Unit: mm
Surface data surface number rd dm nd vd Effective radius
1 * 1.919 0.709 1.54470 56.2 1.11
2 * -13.675 0.030 0.87
3 (Aperture) ∞ 0.020 0.80
4 * 4.123 0.300 1.63200 23.4 0.82
5 * 1.652 0.726 0.566 0.87
6 * 3.731 0.523 1.53050 55.7 1.43
7 * 3.720 0.247 1.64
8 * -55.999 0.768 1.54470 56.2 1.68
9 * -2.045 0.541 0.701 1.83
10 * 3.866 0.450 1.53050 55.7 2.16
11 * 1.208 0.490 2.58
12 ∞ 0.145 1.51630 64.1 2.87
13 ∞ 2.90

Aspheric data 1st surface
K = 0.41896E-01
A4 = -0.35926E-03
A6 = -0.70430E-02
A8 = 0.70704E-02
A10 = -0.38897E-02

Second side
K = -0.84487E + 01
A4 = 0.28585E-01
A6 = 0.23500E-01
A8 = -0.49866E-01
A10 = 0.22567E-01

4th page
K = -0.29234E + 02
A4 = -0.68765E-02
A6 = 0.98390E-01
A8 = -0.15680E + 00
A10 = 0.13102E + 00
A12 = -0.51129E-01

5th page
K = -0.45194E + 01
A4 = 0.25276E-01
A6 = 0.64564E-01
A8 = -0.44051E-01
A10 = -0.15027E-02
A12 = 0.13804E-01

6th page
K = -0.21242E + 02
A4 = -0.11219E-02
A6 = -0.88735E-02
A8 = 0.55257E-02
A10 = -0.23109E-02
A12 = 0.10780E-03

7th page
K = -0.22232E + 02
A4 = -0.56494E-02
A6 = -0.76307E-02
A8 = 0.19503E-02
A10 = -0.96862E-03
A12 = -0.29481E-04

8th page
K = -0.42418E + 05
A4 = -0.35840E-01
A6 = 0.64695E-02
A8 = 0.18540E-02
A10 = -0.11067E-02
A12 = 0.12493E-03

9th page
K = -0.64254E + 01
A4 = -0.91029E-01
A6 = 0.50074E-01
A8 = -0.24836E-01
A10 = 0.12241E-01
A12 = -0.25207E-02
A14 = 0.23437E-04
A16 = 0.32363E-04

10th page
K = -0.11861E + 03
A4 = -0.20365E + 00
A6 = 0.83889E-01
A8 = -0.14189E-01
A10 = 0.28182E-03
A12 = 0.17663E-03
A14 = -0.12455E-04

11th page
K = -0.72109E + 01
A4 = -0.80466E-01
A6 = 0.28408E-01
A8 = -0.72168E-02
A10 = 0.11783E-02
A12 = -0.11781E-03
A14 = 0.53062E-05

Various data
f 4.3 (object distance ∞)
Fno. 2.40 (object distance ∞)
f 4.050 (object distance 10cm)
Fno. 2.42 (object distance 10cm)
ω 33.2
2Y '5.712
fB 0.3
ENTP 0.57
EXTP -2.47
H1 -1.8
H2 -4

Single lens Data lens Start surface Focal length
1 1 3.140
2 4 -4.578
3 6 153.475
4 8 3.877
5 10 -3.518

Lens group Data Lens group Start surface Focal length
1 1 6.479
2 6 3.989
3 10 -3.518

Example 2
Unit: mm
Surface data surface number rd dm nd vd Effective radius
1 * 1.950 0.535 1.54470 56.2 0.99
2 * -38.523 0.000 0.83
3 (Aperture) ∞ 0.100 0.80
4 * 2.499 0.230 1.63200 23.4 0.85
5 * 1.392 0.726 0.562 0.88
6 * 2.405 0.396 1.54470 56.2 1.47
7 * 2.468 0.408 1.65
8 * -5.418 0.645 1.54470 56.2 1.71
9 * -1.760 0.250 0.414 1.82
10 * 1.536 0.474 1.53050 55.7 2.45
11 * 0.919 0.735 2.60
12 ∞ 0.300 1.51630 64.1 2.85
13 ∞ 2.91

Aspheric data 1st surface
K = -0.30243E + 00
A4 = -0.28002E-02
A6 = -0.29517E-01
A8 = 0.34971E-01
A10 = -0.33248E-01

Second side
K = -0.14013E + 02
A4 = -0.55230E-01
A6 = 0.14702E + 00
A8 = -0.19517E + 00
A10 = 0.71396E-01

4th page
K = -0.20622E + 02
A4 = -0.27472E-01
A6 = 0.19885E + 00
A8 = -0.23760E + 00
A10 = 0.10061E + 00
A12 = -0.68691E-02

5th page
K = -0.56420E + 01
A4 = 0.58302E-01
A6 = 0.84456E-01
A8 = -0.50109E-01
A10 = -0.53197E-01
A12 = 0.49364E-01

6th page
K = -0.62762E + 01
A4 = -0.31708E-01
A6 = 0.61870E-02
A8 = -0.14411E-03
A10 = -0.53252E-03
A12 = -0.16564E-03

7th page
K = -0.48687E + 01
A4 = -0.25130E-01
A6 = -0.10666E-01
A8 = 0.10673E-01
A10 = -0.58414E-02
A12 = 0.95948E-03

8th page
K = -0.20000E + 03
A4 = -0.53315E-01
A6 = 0.38504E-01
A8 = -0.17963E-01
A10 = 0.41318E-02
A12 = -0.26521E-03

9th page
K = -0.17424E + 01
A4 = -0.37902E-01
A6 = 0.36037E-01
A8 = -0.17731E-01
A10 = 0.10871E-01
A12 = -0.26589E-02
A14 = 0.14780E-04
A16 = 0.45854E-04

10th page
K = -0.10849E + 02
A4 = -0.15806E + 00
A6 = 0.64023E-01
A8 = -0.10627E-01
A10 = 0.36323E-03
A12 = 0.89482E-04
A14 = -0.72474E-05

11th page
K = -0.43003E + 01
A4 = -0.95804E-01
A6 = 0.36222E-01
A8 = -0.10191E-01
A10 = 0.18946E-02
A12 = -0.20474E-03
A14 = 0.94721E-05

Various data
f 4.09 (object distance ∞)
Fno. 2.40 (object distance ∞)
f 3.923 (object distance 10cm)
Fno. 2.44 (object distance 10cm)
ω 34.5
2Y '5.712
fB 0.3
ENTP 0.38
EXTP -3.01
H1 -0.58
H2 -3.79

Single lens Data lens Start surface Focal length
1 1 3.424
2 4 -5.406
3 6 53.649
4 8 4.505
5 10 -5.875

Lens group Data Lens group Start surface Focal length
1 1 6.707
2 6 4.471
3 10 -5.875

Example 3
Unit: mm
Surface data surface number rd dm nd vd Effective radius
1 * 1.949 0.538 1.54470 56.2 0.99
2 * -21.407 -0.004 0.82
3 (Aperture) ∞ 0.054 0.80
4 * 2.864 0.280 1.63200 23.4 0.85
5 * 1.463 0.736 0.573 0.89
6 * 2.489 0.345 1.54470 56.2 1.47
7 * 2.580 0.379 1.66
8 * -5.438 0.724 1.54470 56.2 1.78
9 * -1.782 0.250 0.413 1.85
10 * 1.738 0.535 1.53050 55.7 2.46
11 * 0.991 0.817 2.64
12 ∞ 0.145 1.51630 64.1 2.89
13 ∞ 2.92

Aspheric data 1st surface
K = -0.25694E + 00
A4 = -0.21741E-02
A6 = -0.24708E-01
A8 = 0.29221E-01
A10 = -0.27185E-01

Second side
K = 0.59165E + 01
A4 = -0.41147E-01
A6 = 0.15575E + 00
A8 = -0.21832E + 00
A10 = 0.88889E-01

4th page
K = -0.18964E + 02
A4 = -0.30203E-01
A6 = 0.19745E + 00
A8 = -0.23573E + 00
A10 = 0.95328E-01
A12 = 0.23082E-02

5th page
K = -0.43391E + 01
A4 = 0.34655E-01
A6 = 0.80831E-01
A8 = -0.33235E-01
A10 = -0.53639E-01
A12 = 0.46311E-01

6th page
K = -0.67503E + 01
A4 = -0.29400E-01
A6 = 0.37572E-02
A8 = 0.34474E-03
A10 = -0.11997E-02
A12 = -0.62985E-04

7th page
K = -0.47028E + 01
A4 = -0.25983E-01
A6 = -0.87050E-02
A8 = 0.10541E-01
A10 = -0.61926E-02
A12 = 0.10508E-02

8th page
K = -0.20000E + 03
A4 = -0.57196E-01
A6 = 0.39909E-01
A8 = -0.14143E-01
A10 = 0.27279E-02
A12 = -0.14220E-03

9th page
K = -0.20433E + 01
A4 = -0.53943E-01
A6 = 0.37190E-01
A8 = -0.16392E-01
A10 = 0.10740E-01
A12 = -0.26841E-02
A14 = 0.37312E-05
A16 = 0.49116E-04

10th page
K = -0.11418E + 02
A4 = -0.16320E + 00
A6 = 0.65582E-01
A8 = -0.10699E-01
A10 = 0.34782E-03
A12 = 0.91631E-04
A14 = -0.73929E-05

11th page
K = -0.43023E + 01
A4 = -0.94709E-01
A6 = 0.35974E-01
A8 = -0.10185E-01
A10 = 0.18927E-02
A12 = -0.20107E-03
A14 = 0.90241E-05

Various data
f 4.09 (object distance ∞)
Fno. 2.40 (object distance ∞)
f 3.922 (object distance 10cm)
Fno. 2.42 (object distance 10cm)
ω 34.5
2Y '5.712
fB 0.29
ENTP 0.38
EXTP -3
H1 -0.6
H2 -3.79

Single lens Data lens Start surface Focal length
1 1 3.306
2 4 -5.132
3 6 55.314
4 8 4.549
5 10 -5.786

Lens group Data Lens group Start surface Focal length
1 1 6.582
2 6 4.484
3 10 -5.786

Example 4
Unit: mm
Surface data surface number rd dm nd vd Effective radius
1 * 1.551 0.433 1.54470 56.2 0.88
2 * 48.237 0.048 0.74
3 (Aperture) ∞ 0.002 0.69
4 * 2.606 0.183 1.63200 23.4 0.71
5 * 1.411 0.792 0.653 0.74
6 * 5.418 0.325 1.58300 30.0 1.17
7 * 2.920 0.117 1.49
8 * -232.117 0.883 1.54470 56.2 1.70
9 * -1.563 0.552 0.691 1.74
10 * 2.244 0.430 1.53050 55.7 2.35
11 * 0.977 0.500 2.64
12 ∞ 0.145 1.51630 64.1 2.80
13 ∞ 2.84

Aspheric data 1st surface
K = 0.41415E + 00
A4 = -0.37689E-02
A6 = 0.17668E-01
A8 = -0.23233E-01
A10 = 0.33420E-02
A12 = 0.45468E-01

Second side
K = 0.50000E + 02
A4 = 0.56716E-01
A6 = -0.23292E-01
A8 = 0.21713E-01
A10 = -0.15444E-01
A12 = 0.64215E-01

4th page
K = -0.11747E + 02
A4 = 0.59161E-02
A6 = 0.38159E-01
A8 = -0.45582E-01
A10 = 0.24607E-02
A12 = 0.17962E-01

5th page
K = -0.39137E + 01
A4 = 0.50498E-01
A6 = 0.84768E-01
A8 = -0.61733E-01
A10 = -0.44361E-02
A12 = 0.59071E-01

6th page
K = 0.80090E + 01
A4 = -0.13885E + 00
A6 = 0.17173E-01
A8 = -0.12066E-01
A10 = 0.13749E-01
A12 = -0.12510E-01

7th page
K = -0.14055E + 02
A4 = -0.59943E-01
A6 = -0.25211E-02
A8 = 0.48573E-02
A10 = -0.25635E-02
A12 = -0.53913E-04

8th page
K = 0.94435E + 04
A4 = -0.26923E-01
A6 = -0.69462E-02
A8 = 0.55880E-02
A10 = 0.20439E-02
A12 = -0.65770E-03

9th page
K = -0.21964E + 01
A4 = -0.68710E-01
A6 = 0.39030E-01
A8 = -0.34380E-01
A10 = 0.18717E-01
A12 = -0.29798E-02
A14 = 0.23194E-04

10th page
K = -0.26589E + 02
A4 = -0.18864E + 00
A6 = 0.75124E-01
A8 = -0.10881E-01
A10 = -0.20196E-03
A12 = 0.21077E-03
A14 = -0.15301E-04

11th page
K = -0.48047E + 01
A4 = -0.91556E-01
A6 = 0.36408E-01
A8 = -0.10524E-01
A10 = 0.19471E-02
A12 = -0.19775E-03
A14 = 0.82707E-05

Various data
f 3.68 (object distance ∞)
Fno. 2.45 (object distance ∞)
f 3.500 (object distance 10cm)
Fno. 2.45 (object distance 10cm)
ω 36.7
2Y '5.53
fB 0.29
ENTP 0.37
EXTP -2.48
H1 -0.84
H2 -3.4

Single lens Data lens Start surface Focal length
1 1 2.933
2 4 -5.172
3 6 -11.406
4 8 2.884
5 10 -3.698

Lens group Data Lens group Start surface Focal length
1 1 5.346
2 6 3.671
3 10 -3.698

Example 5
Unit: mm
Surface data surface number rd dm nd vd Effective radius
1 * 2.320 0.528 1.54470 56.2 0.99
2 * -7.843 0.030 0.84
3 (Aperture) ∞ 0.041 0.71
4 * 3.252 0.300 1.63200 23.4 0.74
5 * 1.583 0.661 0.557 0.81
6 * 3.025 0.300 1.63200 23.4 1.25
7 * 2.080 0.120 1.53
8 * 5.788 1.391 1.54470 56.2 1.85
9 * -1.647 0.334 0.438 1.93
10 * 1.946 0.490 1.54470 56.2 2.22
11 * 0.869 0.700 2.64
12 ∞ 0.145 1.51630 64.1 2.82
13 ∞ 2.86

Aspheric data 1st surface
K = -0.22138E + 00
A3 = -0.88351E-03
A4 = -0.10849E-01
A5 = 0.14624E-02
A6 = -0.14871E-01
A7 = -0.41092E-03
A8 = 0.48040E-02
A9 = -0.64370E-03
A10 = -0.19742E-01
A11 = 0.12559E-03
A12 = 0.60011E-03
A13 = 0.98700E-03
A14 = 0.11988E-02
A15 = 0.11831E-02
A16 = 0.90388E-03
A17 = 0.33871E-03
A18 = -0.22374E-03
A19 = -0.13311E-02
A20 = -0.27597E-02

Second side
K = 0.22795E + 02
A3 = 0.45994E-04
A4 = 0.30168E-01
A5 = -0.80161E-04
A6 = 0.17934E-02
A7 = 0.12282E-02
A8 = -0.96301E-01
A9 = 0.16603E-02
A10 = 0.57783E-01
A11 = 0.16529E-02
A12 = 0.92740E-03
A13 = -0.10158E-03
A14 = -0.14652E-02
A15 = -0.32314E-02
A16 = -0.50850E-02
A17 = -0.65290E-02
A18 = -0.56432E-02
A19 = -0.15566E-02
A20 = 0.62102E-02

4th page
K = -0.14011E + 02
A3 = -0.36399E-02
A4 = 0.10521E-01
A5 = -0.25313E-02
A6 = 0.10730E + 00
A7 = -0.16455E-02
A8 = -0.23026E + 00
A9 = 0.28841E-02
A10 = 0.15760E + 00
A11 = 0.52014E-02
A12 = -0.11583E-01
A13 = 0.25475E-02
A14 = -0.74236E-03
A15 = -0.47662E-02
A16 = -0.88055E-02
A17 = -0.11590E-01
A18 = -0.10920E-01
A19 = -0.34846E-02
A20 = 0.15057E-01

5th page
K = -0.44390E + 01
A3 = -0.17662E-02
A4 = 0.24441E-01
A5 = -0.10978E-02
A6 = 0.79540E-01
A7 = -0.14890E-02
A8 = -0.82277E-01
A9 = 0.15812E-02
A10 = -0.29836E-01
A11 = 0.34186E-02
A12 = 0.63641E-01
A13 = 0.67654E-03
A14 = -0.24643E-02
A15 = -0.59742E-02
A16 = -0.87544E-02
A17 = -0.89122E-02
A18 = -0.47722E-02
A19 = 0.81122E-02
A20 = 0.32854E-01

6th page
K = -0.25309E + 02
A3 = -0.27600E-02
A4 = -0.50027E-01
A5 = 0.40529E-03
A6 = -0.15959E-01
A7 = 0.65393E-04
A8 = 0.36509E-02
A9 = -0.27129E-03
A10 = 0.66114E-02
A11 = -0.84400E-04
A12 = -0.52711E-02
A13 = 0.62713E-04
A14 = 0.67589E-04
A15 = 0.49187E-04
A16 = 0.23528E-04
A17 = 0.35196E-05
A18 = -0.80046E-05
A19 = -0.88937E-05
A20 = -0.23669E-05

7th page
K = -0.12888E + 02
A3 = 0.35829E-03
A4 = -0.31911E-01
A5 = -0.25577E-03
A6 = -0.11048E-01
A7 = 0.46714E-04
A8 = 0.52643E-02
A9 = 0.60807E-04
A10 = -0.48379E-03
A11 = -0.85321E-05
A12 = -0.47485E-03
A13 = -0.50193E-05
A14 = 0.10985E-05
A15 = 0.37818E-05
A16 = 0.41821E-05
A17 = 0.29767E-05
A18 = 0.13539E-05
A19 = -0.79265E-07
A20 = -0.10930E-05

8th page
K = -0.27859E + 02
A3 = -0.72094E-03
A4 = -0.17807E-01
A5 = 0.13927E-03
A6 = 0.78236E-02
A7 = 0.15930E-03
A8 = 0.17687E-02
A9 = 0.28790E-04
A10 = -0.81274E-03
A11 = -0.20335E-05
A12 = 0.55026E-04
A13 = -0.21807E-05
A14 = -0.11154E-05
A15 = -0.39576E-06
A16 = -0.23177E-07
A17 = 0.73803E-07
A18 = 0.80081E-07
A19 = 0.52432E-07
A20 = 0.26497E-07

9th page
K = -0.14772E + 01
A3 = -0.26748E-02
A4 = -0.38633E-01
A5 = 0.26239E-03
A6 = 0.44326E-01
A7 = 0.20371E-04
A8 = -0.37178E-01
A9 = 0.22525E-04
A10 = 0.17661E-01
A11 = 0.75572E-05
A12 = -0.30949E-02
A13 = 0.98269E-06
A14 = 0.10378E-04
A15 = -0.17678E-06
A16 = 0.31387E-04
A17 = -0.69780E-07
A18 = -0.25511E-07
A19 = 0.14334E-08
A20 = 0.11049E-07

10th page
K = -0.17853E + 02
A3 = -0.56622E-02
A4 = -0.18458E + 00
A5 = 0.99443E-03
A6 = 0.60900E-01
A7 = 0.19682E-04
A8 = -0.74261E-02
A9 = -0.18022E-04
A10 = 0.38630E-03
A11 = -0.20844E-05
A12 = -0.10005E-03
A13 = 0.80533E-06
A14 = 0.15281E-04
A15 = 0.19233E-06
A16 = 0.71169E-07
A17 = 0.16057E-07
A18 = -0.91132E-08
A19 = -0.87933E-08
A20 = -0.64079E-08

11th page
K = -0.37528E + 01
A3 = -0.93591E-02
A4 = -0.91891E-01
A5 = 0.55940E-02
A6 = 0.34040E-01
A7 = -0.49685E-03
A8 = -0.93912E-02
A9 = 0.37605E-04
A10 = 0.15533E-02
A11 = 0.51139E-05
A12 = -0.14004E-03
A13 = 0.37474E-06
A14 = 0.52567E-05
A15 = -0.85652E-07
A16 = -0.31453E-07
A17 = -0.10484E-07
A18 = -0.23880E-08
A19 = 0.12900E-08
A20 = 0.62972E-09

Various data
f 3.63 (object distance ∞)
Fno. 2.40 (object distance ∞)
f 3.476 (object distance 10cm)
Fno. 2.40 (object distance 10cm)
ω 36.9
2Y '5.53
fB 0.13
ENTP 0.41
EXTP -2.82
H1 -0.43
H2 -3.5

Single lens Data lens Start surface Focal length
1 1 3.348
2 4 -5.249
3 6 -12.023
4 8 2.521
5 10 -3.434

Lens group Data Lens group Start surface Focal length
1 1 6.694
2 6 3.058
3 10 -3.434

Example 6
Unit: mm
Surface data surface number rd dm nd vd Effective radius
1 (Aperture) ∞ 0.000 0.85
2 * 2.063 0.593 1.54470 56.2 1.15
3 * -13.004 0.050 1.14
4 * 2.569 0.288 1.63200 23.4 1.16
5 * 1.324 0.964 0.814 1.16
6 * 79.139 0.899 1.54470 56.2 1.82
7 * -2.581 0.592 0.742 1.86
8 * 1.758 0.510 1.54470 56.2 2.26
9 * 1.032 0.700 2.61
10 ∞ 0.145 1.51630 64.1 2.83
11 ∞ 2.86

Aspheric data 2nd surface
K = 0.35079E + 00
A4 = 0.54384E-02
A6 = -0.93758E-02
A8 = 0.67299E-02
A10 = 0.33136E-02

Third side
K = 0.72675E + 01
A4 = 0.45938E-01
A6 = -0.70962E-01
A8 = 0.91426E-01
A10 = -0.24161E-01

4th page
K = -0.74930E + 01
A4 = -0.44538E-01
A6 = -0.41307E-01
A8 = 0.75935E-01
A10 = -0.86915E-03
A12 = -0.15540E-01

5th page
K = -0.29139E + 01
A4 = -0.17640E-01
A6 = 0.26285E-01
A8 = -0.25742E-01
A10 = 0.45900E-01
A12 = -0.19641E-01

6th page
K = -0.68981E + 04
A4 = 0.20614E-01
A6 = -0.15379E-01
A8 = 0.12847E-01
A10 = -0.40650E-02
A12 = 0.46243E-03

7th page
K = -0.57775E + 01
A4 = -0.66796E-01
A6 = 0.56108E-01
A8 = -0.35663E-01
A10 = 0.16470E-01
A12 = -0.32403E-02
A14 = 0.48988E-04
A16 = 0.38618E-04

8th page
K = -0.92343E + 01
A4 = -0.13915E + 00
A6 = 0.32207E-01
A8 = -0.29637E-02
A10 = 0.55955E-03
A12 = -0.15757E-03
A14 = 0.14149E-04

9th page
K = -0.39719E + 01
A4 = -0.86033E-01
A6 = 0.28001E-01
A8 = -0.74526E-02
A10 = 0.13072E-02
A12 = -0.12455E-03
A14 = 0.47834E-05

Various data
f 4.09 (object distance ∞)
Fno. 2.40 (object distance ∞)
f 3.942 (object distance 10cm)
Fno. 2.43 (object distance 10cm)
ω 34.5
2Y '5.712
fB 0.36
ENTP 0
EXTP -3.02
H1 -0.86
H2 -3.72

Single lens Data lens Start surface Focal length
1 2 3.315
2 4 -4.747
3 6 4.606
4 8 -6.104

Lens group Data Lens group Start surface Focal length
1 1 7.096
2 6 4.606
3 8 -6.104

Example 7
Unit: mm
Surface data surface number rd dm nd vd Effective radius
1 (Aperture) ∞ -0.032 0.85
2 * 1.951 0.566 1.54470 56.2 1.05
3 * -17.056 0.050 1.05
4 * 2.894 0.254 1.63200 23.4 1.08
5 * 1.455 1.065 0.914 1.07
6 * -120.951 0.902 1.54470 56.2 1.48
7 * -2.489 0.510 0.660 1.63
8 * 1.852 0.547 1.54470 56.2 1.89
9 * 1.027 0.700 2.26
10 ∞ 0.145 1.51630 64.1 2.43
11 ∞ 2.47

Aspheric data 2nd surface
K = 0.37954E + 00
A4 = 0.42487E-03
A6 = -0.58565E-02
A8 = 0.29946E-02
A10 = 0.40040E-02

Third side
K = 0.50000E + 02
A4 = 0.36810E-01
A6 = -0.68088E-01
A8 = 0.99686E-01
A10 = -0.30795E-01

4th page
K = -0.98054E + 01
A4 = -0.38873E-01
A6 = -0.41122E-01
A8 = 0.79571E-01
A10 = 0.71123E-02
A12 = -0.23859E-01

5th page
K = -0.27418E + 01
A4 = -0.21715E-01
A6 = 0.27806E-01
A8 = -0.16153E-01
A10 = 0.48907E-01
A12 = -0.25155E-01

6th page
K = 0.55129E + 04
A4 = 0.88868E-02
A6 = -0.13257E-01
A8 = 0.11592E-01
A10 = -0.41505E-02
A12 = 0.42410E-03

7th page
K = -0.54244E + 01
A4 = -0.77850E-01
A6 = 0.56741E-01
A8 = -0.35018E-01
A10 = 0.16195E-01
A12 = -0.33737E-02
A14 = 0.38167E-04
A16 = 0.47113E-04

8th page
K = -0.10923E + 02
A4 = -0.15245E + 00
A6 = 0.38133E-01
A8 = -0.29435E-02
A10 = 0.44349E-03
A12 = -0.20516E-03
A14 = 0.22549E-04

9th page
K = -0.42062E + 01
A4 = -0.80572E-01
A6 = 0.25434E-01
A8 = -0.67765E-02
A10 = 0.12331E-02
A12 = -0.12285E-03
A14 = 0.48562E-05

Various data
f 4.09 (object distance ∞)
Fno. 2.40 (object distance ∞)
f 3.942 (object distance 10cm)
Fno. 2.43 (object distance 10cm)
ω 34.5
2Y '5.712
fB 0.35
ENTP 0
EXTP -2.96
H1 -0.96
H2 -3.74

Single lens Data lens Start surface Focal length
1 2 3.249
2 4 -4.968
3 6 4.653
4 8 -5.518

Lens group Data Lens group Start surface Focal length
1 1 6.620
2 6 4.653
3 8 -5.518

Example 8
Unit: mm
Surface data surface number rd dm nd vd Effective radius
1 * 2.794 0.60 1.54470 56.2 0.96
2 * -15.241 0.03 0.69
3 (Aperture) ∞ 0.06 0.63
4 * 2.060 0.30 1.63200 23.4 0.69
5 * 1.292 0.60 0.507 0.77
6 * 5.256 1.08 1.54470 56.2 1.31
7 * -2.528 0.22 1.53
8 * -1.234 0.45 1.63200 23.4 1.64
9 * -1.133 0.41 0.504 1.72
10 * 7.226 0.65 1.63200 23.4 1.89
11 * 1.418 0.50 2.51
12 ∞ 0.30 1.51630 64.1 2.79
13 ∞ 2.87

Aspheric data 1st surface
K = 0.69209E + 00
A4 = 0.52106E-02
A6 = 0.14389E-01
A8 = -0.47556E-01
A10 = 0.10714E + 00
A12 = -0.92454E-01
A14 = 0.32977E-01

Second side
K = 0.12110E + 02
A4 = -0.29709E-01
A6 = 0.23913E + 00
A8 = -0.42925E + 00
A10 = 0.64063E + 00
A12 = -0.64759E + 00
A14 = 0.34145E + 00

4th page
K = -0.97334E + 01
A4 = -0.79196E-01
A6 = 0.18988E + 00
A8 = -0.76588E-01
A10 = -0.37412E + 00
A12 = 0.75641E + 00
A14 = -0.43044E + 00

5th page
K = -0.37509E + 01
A4 = -0.43905E-01
A6 = 0.78331E-01
A8 = 0.15738E-02
A10 = -0.15496E + 00
A12 = 0.22392E + 00
A14 = -0.10266E + 00

6th page
K = 0.12084E + 02
A4 = -0.18387E-01
A6 = -0.21808E-01
A8 = 0.27119E-01
A10 = -0.26987E-01
A12 = 0.95160E-02
A14 = -0.11120E-02

7th page
K = -0.50031E + 00
A4 = -0.13089E-01
A6 = 0.16455E-01
A8 = -0.19307E-01
A10 = 0.10697E-01
A12 = -0.39845E-02
A14 = 0.66084E-03

8th page
K = -0.57182E + 00
A4 = 0.48335E-01
A6 = 0.47253E-01
A8 = -0.32998E-02
A10 = -0.31320E-02
A12 = 0.11277E-02
A14 = -0.12406E-03

9th page
K = -0.25945E + 01
A4 = -0.76929E-01
A6 = 0.54855E-01
A8 = -0.51051E-02
A10 = 0.16342E-02
A12 = -0.10678E-02
A14 = 0.13050E-03

10th page
K = -0.30000E + 02
A4 = -0.13156E + 00
A6 = 0.32407E-01
A8 = -0.22211E-02
A10 = -0.90932E-03
A12 = 0.16975E-03
A14 = -0.63405E-06

11th page
K = -0.57247E + 01
A4 = -0.70789E-01
A6 = 0.22784E-01
A8 = -0.57758E-02
A10 = 0.92623E-03
A12 = -0.87481E-04
A14 = 0.36677E-05

Various data
f 3.83 (object distance ∞)
Fno. 2.81 (object distance ∞)
f 3.649 (object distance 10cm)
Fno. 2.81 (object distance 10cm)
ω 37.6
2Y '5.96
fB 0.25
ENTP 0.46
EXTP -2.69
H1 -0.7
H2 -3.57

Single lens Data lens Start surface Focal length
1 1 4.387
2 4 -6.471
3 6 3.294
4 8 8.010
5 10 -2.919

Lens group Data Lens group Start surface Focal length
1 1 9.189
2 6 2.747
3 10 -2.919

  As shown in FIGS. 17 to 24, the imaging optical systems of Examples 1 to 8 show good aberration characteristics. Moreover, all of Examples 1 to 8 satisfy the conditional expressions (1) and (2). That is, according to the present invention, an imaging optical system having good optical characteristics can be obtained with high accuracy and efficiency.

  By the way, in the above-described embodiment, the principal ray incident angle of the light beam incident on the imaging surface 70a of the solid-state imaging device 70 is not necessarily designed to be sufficiently small in the periphery of the imaging surface 70a. However, with recent technology, it has become possible to reduce shading by reviewing the arrangement of the color filters of the solid-state imaging device and the on-chip microlens array. Specifically, if the pitch of the arrangement of the color filters and the on-chip microlens array is set slightly smaller than the pixel pitch of the imaging surface of the solid-state imaging device, the color for each pixel increases toward the periphery of the imaging surface. Since the filter and the on-chip microlens array shift to the optical axis side of the imaging optical system (imaging lens), the obliquely incident light beam can be efficiently guided to the light receiving portion of each pixel. Thereby, the shading which generate | occur | produces with a solid-state image sensor can be restrained small. In consideration of this point, each of the above-described embodiments is a design example aimed at further miniaturization.

(Other)
In addition, this invention is not limited to the structure of embodiment shown in the above and an Example. That is, various modifications can be made without departing from the object of the present invention.

  In the above, the case where the present invention is applied to a single-focus imaging optical system has been described. However, the present invention is not limited to a single-focus imaging optical system and can be widely applied to imaging optical systems. The present invention can also be applied to an optical system (for example, an optical system constituting an optical pick-up). That is, the present invention can be widely applied to an optical system having a configuration in which a lens is further disposed between two lenses provided with position reference marks.

  In the above description, the position reference mark is provided in the lens center. However, the position where the position reference mark is provided is not limited to this position. For example, it is of course possible to adopt a configuration provided in the edge portion around the lens (a portion provided around the effective portion of the lens; for example, see L2A and L5A in FIG. 2). In this case, the position reference mark may have the configuration shown in the present embodiment, or may have a ring shape or the like.

  The present invention is suitable for an imaging optical system that forms an image of a subject on the imaging surface of a solid-state imaging device.

DESCRIPTION OF SYMBOLS 1 Imaging optical system 70 Solid-state image sensor 70a Imaging surface L1 1st lens L2 2nd lens (1st mark lens)
L3 Third lens L4 Fourth lens (may be second mark lens)
L5 5th lens (may be 2nd mark lens)
LG1 First lens group LG2 Second lens group (intermediate lens group)
LG3 Third lens group M1, M2 Position reference mark L2A, L5A Edge

Claims (6)

A first mark lens and a second mark lens having a position reference mark on the surface of the lens;
An intermediate lens group composed of at least one lens disposed between the first mark lens and the second mark lens;
An optical system comprising:
An optical system in which the intermediate lens group satisfies the following conditional expression.
0.1 <fm / f <2
However,
fm: focal length of the intermediate lens group f: focal length of the entire optical system Used as an imaging optical system for imaging a subject on the imaging surface of a solid-state imaging device,
A first lens group, a second lens group, and a third lens group, each including at least one lens in order from the object side to the image side,
2. The first lens group includes the first mark lens, the second lens group is the intermediate lens group, and the third lens group includes the second mark lens. The optical system described in 1. The first lens group and the third lens group are fixed to the imaging surface;
The optical system according to claim 2, wherein the second lens group is movable in the optical axis direction.   The optical system according to claim 1, wherein the position reference mark is provided at a lens center.   The optical system according to any one of claims 1 to 3, wherein the position reference mark is provided on an edge portion formed on an outer periphery of the lens. A lens position adjusting method in an optical system according to any one of claims 1 to 5,
A lens position adjustment method comprising: observing the first mark lens and the second mark lens along an optical axis direction and performing position adjustment so that the position reference marks of both coincide with each other.

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