JPS6021432A - Apparatus for evaluating composite optical system - Google Patents

Abstract

PURPOSE:To enable to measure optical transmitting functions and optical intensities in the longitudinal and lateral directions, by arranging a rotary disk, which has a plurality of lattices extending radially toward an outer periphery part at a specified position. CONSTITUTION:With regard to the measurememt in the logitudinal direction, slits on the side of a body 31 are provided at the rear stage of a diffusing plate 18. A disk 32 has a plurality of lattices extending radially toward the outer periphery, which become parallel with the slit 31 when each lattice comes to a measuring position 34, and has a rotary center Mv. The disk 32 is arranged so that it is positioned on the surface of a composite optical system 100. With respect to the measurement in the lateral direction, the disk 32 is arranged so that it is aligned with the longitudinal direction of the composite optical system 100 when the lattice comes to a measuring position 35. A slit on the side of a body 33, which is the same as the slit on the side of the body 31, are provided at the rear stage of the diffusing plate 18. In this constitution, the optical transmitting functions and the optical intensities in the longitudinal and lateral directions can be measured.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to the longitudinal and lateral optical transfer functions (M
The present invention relates to a collective optical system evaluation device capable of measuring changes in light intensity (TF) and light intensity.

[Prior art]

As a conventional optical system evaluation device, there is one shown in FIG. 1, for example. This optical system evaluation device includes a condenser lens 2 that condenses light from a light source 1, an object-side slit 3 that has a thin groove cut in the vertical direction and allows a part of the light from the condenser lens 2 to pass through, and the slit. 3 to form an image at a predetermined position (this is a lens to be evaluated as described later); and an image side slit 5 which is disposed at the position where the lens 4 forms an image and has a thin groove cut in the horizontal direction. , a relay lens 6 that forms the image projected onto the slit 5 at a predetermined position, and a transparent portion and an opaque portion arranged at a predetermined interval (for example, the width ratio thereof is 1).
= 1), which are arranged alternately at the focal position of the image side slit 5 and scanned in the arrow direction Sl, and the grating of the slit 7 and the image of the relay lens 6. A condenser lens 8 that forms superimposed images at a predetermined position, and a light receiver 9 that has a light receiving surface disposed at the image forming position of the lens 8 and converts a light intensity signal into an electrical signal.
, an arithmetic circuit 10 that performs predetermined arithmetic operations based on the output signal of the light receiver 9, and a display section 11 that displays the MTF calculation result, which will be described later, by the arithmetic circuit 10.

In the above configuration, MTF (Modulatton
As is well-known, the transfer function (optical transfer function) is a curve that shows the resolution as a frequency characteristic. is irradiated onto the object-side slit 3 via the condenser lens 2. As shown in FIG. 2, in the object side slit 3, an image 12 of the light source is formed in a range of a width Ws that is sufficiently larger than the width of the narrow groove, Wo. The image formed on the object side slit 3 is projected onto the image side slit 5 via the lens 4. This projected image is the third
The width of the image 13 shown in the figure is Wi.

If the width of the narrow groove is ΔW and the length of the image 13 is L, then Li)
Due to the relationship between W and ΔW, the image information is on the image side, □
) i5, it is treated as one-dimensional information that spreads in the X-axis (Fig. 1) direction. The dimensional information is projected by a condenser lens 6 onto the lattice portion of the Schiffurier deflection slit 7. The slit 7 is scanned in the arrow direction S1 in the figure, and optical Fourier transformation is performed (a sine wave grating is used as the grating of the slit 7). The converted light intensity information is converted into an electrical signal by the light receiver 9 and sent to the arithmetic circuit 10.

The image plane formed by the lens 4 is a continuous curved image 14, as shown in FIG. So Po
, Pa, Pb, Pc, Pd), its characteristics can be known.

However, if the lens 4 is replaced by a normal lens and a collective optical system is used, the result will be as shown in FIG. That is, the image range of each lens 100 is QI Q2, and its scanning direction (for example, when applied to a copying machine) is Sdl.
Then, one point Q (not shown) is Q'r + Qo +
Like QIB, the light is continuously projected onto the photosensitive material (photosensitive member surface) to form a single point Q'. At this time, Q'l * Qlo
Since rQS is not projected linearly but as a curved line, the point Q' is formed by the average value of different MTFs. Therefore, in the case of a collective optical system, S
Changes in the d1 direction cannot be ignored. This is the T of a normal lens.
This is due to the fact that c1 is about 700m+, whereas it is small at about 1/1o.

Next, projection errors will be explained. As shown in FIG. 6, an image 17 at a position ZOK is projected onto the information 16 (on which two periods of a sine wave are drawn) of the original 15 by the lens 4. For some reason, the projection surface is different from Zo.
If the length of the image 17' when projected at position 2, which is separated by Z, is X, then the variation in magnification is given by (xX, )/,, and this value results in the velocity of the photosensitive material and image stones that cause differences and degrade the contrast of the image. This magnification change, dynamic (Am)
can also be approximately given as ΔZ/Tc/2.

If ΔZ is constant, the magnification fluctuation increases in inverse proportion to Tc. That is, the smaller Tc is, the larger the magnification fluctuation is, and the more the contrast deterioration of the image is. Therefore, due to the difference in conjugate length, the collective optical system suffers from deterioration of image contrast due to defocus compared to a normal lens.

As described above, MTF measurement of a collective optical system differs greatly from that of a normal lens in the following three points.

(1) The MTF in the scanning direction of the copying machine changes greatly depending on the width of the exposure slit.

(2) Image deterioration due to speed errors caused by defocus is significant.

(3) It has multiple optical axes.

For this reason, (al) the integrated MTF within the exposure slit width is the same, (b) the MTF including the speed error can be measured, (c) the measurement can be performed continuously in the direction perpendicular to the scanning direction, etc. The seventh example shows an example of a conventional collective optical system evaluation device designed to meet these requirements.
It is a diagram.

In FIG. 7, the same parts as shown in FIG. 1 are indicated by the same reference numerals, so redundant explanation will be omitted.
an object-side slit 19 arranged after the diffusion plate 18;
Collective optical system 10 arranged after the object side slit 19
0, a detection slit 20 provided with a narrow groove matching the grid of the object-side slit 19 and disposed at the rear of the collective optical system 100, and a diffuser plate 21 disposed at the rear of the detection slit 20. The other configurations are the same as in FIG. 1.

In the above configuration, under a state in which the object-side slit 19 is illuminated with light from the light source 1 almost uniformly by the diffuser plate 18,
The object side slit 19 and the collective optical system ioo both move at the same speed in the direction of the arrow. As a result, an image of the grating is projected onto the detection slit 20 by the collective optical system, and in this projection process, it is optically Fourier transformed, and the optical signal is transmitted to the diffuser plate 20.
1, the light is received by the light receiver 9 and converted into an electrical signal, and thereafter the same processing as in the case of FIG. 1 is performed.

In this way, the MTF for the grating parallel to the longitudinal direction of collective optical system 100 can be measured.

However, since the conventional collective optical system evaluation apparatus has a structure in which a large number of collective lenses are arranged in the longitudinal direction, it is inconvenient that it cannot measure the MTF in the direction perpendicular to the moving direction Sl. For example, in a copying machine, the contrast of horizontal lines tends to deteriorate due to the vibration of the scanning system, making MTF measurement of horizontal grids essential. In this case, it is desirable to be able to continuously measure the lens group in the horizontal direction, similar to the measurement in the vertical direction shown in FIG.

[Object and structure of the invention]

The present invention has been made in view of the above, and in order to be able to measure B (TF) and light intensity in both the vertical and horizontal directions, a radially extending grating is provided at the outer edge of the disk. The object of the present invention is to provide a collective optical system evaluation device in which a grating portion formed by the above-described method is positioned in a direction perpendicular to and parallel to a reference direction of the collective optical system by rotating the disk.

〔Example〕

Hereinafter, the collective optical system evaluation apparatus according to the present invention will be explained in detail.

8 and 9 show one embodiment of the present invention, and the same parts as in FIG. As shown in the figure, an object side slit 31 (having a narrow groove in a direction perpendicular to the longitudinal direction of the collective optical system 100) is provided at the rear stage of the diffuser plate 18, and a plurality of gratings extending radially on the outer edge are provided. and a rotating disk 3 having a rotation center Mv that is parallel to the slit 31 when each grating reaches the measurement position 34.
2 is placed on the surface of the collective optical system 100.

Regarding measurements in the lateral direction, the disk 32 is arranged so that when the grating reaches the measurement position 35, it coincides with the longitudinal direction of the collective optical system. An object-side slit 33, which is the same as the object-side slit 31 (FIG. 8), is arranged after the diffuser plate 18.

The disk 32 is a transparent disk made of glass or the like, and a lattice is formed around the circumference by arranging transparent parts and opaque parts radially with respect to the center of the circle. The transmission density is determined in consideration of measurement accuracy, and usually requires an optical density of 0.02 or less in transparent parts and 2 or more in opaque parts.

In the above configuration, when the disk 32 rotates in the direction of the arrow with My as the rotation center, the grating at the measurement position 34 moves linearly (same direction as the moving direction of the collective optical system 100), and the lattice is moved linearly with respect to the projected image by the slit 31. A superposition, ie an optical Fourier transform, is achieved. In the embodiment of FIG. 9, measurement position 3
5 is a position rotated by 90 degrees relative to 34. In this case, the rotational movement of the grating at the measurement position can be treated as a nearly straight line, and its direction is the Y-axis direction, which is perpendicular to the embodiment of sb Fig. 8, and circular as in the case of Fig. 8. The grid of the plate 32 and the projected image of the slit 330 are superimposed at the measurement position 35, and Fourier transformation is performed optically.

In this way, the disk 32 on which a lattice with a constant period is drawn around the periphery is rotated about the two rotation center axes Mv and MH,
Furthermore, by measuring at the measurement position 34 on the X-axis and the measurement position 35 on the X-axis, it is possible to measure each MTF in the vertical direction and the horizontal direction. This disk 3
If the collective optical system 100 is moved in the direction 81 shown in the figure during 20 rotations, the 1/lens group can be continuously measured.

Fig. F, 4110 shows another embodiment of the present invention, in which the embodiments shown in Figs. 8 and 9 are integrated, and the MTF in the vertical and horizontal directions can be measured simultaneously. It is.

The center of rotation IIllIMv is on the outer periphery of a common single circle 36
, MH.

The disks 32a and 32b are arranged so that the grids 32b are perpendicular to each other at the measurement position 37, and each disk is driven by a motor (not shown) provided in Mo via a timing belt or the like.

In the above configuration, the gratings arranged at right angles to each other at the measurement position 37 intersect, and the image projected by the slit 31 is projected onto the rotating disk 32a at the measurement position 37.
is superimposed on the lattice of the rotary disk 32b, and is further superimposed on the lattice of the rotating disk 32b, and optically Fourier transform is performed sequentially.

FIG. 11 shows an example of application of the present invention, and the same parts as in FIG. 8 are indicated by the same reference numerals, so redundant explanation will be omitted, but the object side slit 31 shown in FIG. A slit 40 having a narrow groove with a width ΔWu and a length lu is removed.
The structure differs from that shown in FIG. 8 in that it is provided between the collective optical system 100 and the disk 32.

In the above configuration, the light exiting the collective optical system 100 is transmitted through the slit 40, and the slit image is superimposed on the grating of the rotary plate 32, so that changes in light intensity can be measured.

The inventors carried out Examples of the present invention under the conditions shown below.

Spatial frequency 41p/wM Diameter of disk 32 300 Half rotation speed of the center circle of the ring 1/2 rotation/sec Output signal frequency 170Hz Lens movement (Sl) speed 5mm/sec Vertical slit width 40μm Vertical and horizontal slit length 16 ends Horizontal sleeve narrow width Width of slit for light intensity detection 0.1 am receiver
The measurement accuracy under the conditions of photomultiplier tube lamp power of 250 W or more was as follows: For MTF = 5 cm or less Light intensity change: 1% or less, and good measurement results were obtained.

〔Effect of the invention〕

As described above, according to the collective optical system evaluation apparatus of the present invention, a disk having a radially extending grating formed at predetermined intervals around the periphery is rotated, and a direction perpendicular to the reference direction of the grating collective optical system and a Because they are positioned in parallel directions,
It is possible to measure the MTF and light intensity of the collective optical system in both the vertical and horizontal directions.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a conventional optical system evaluation device, FIG. 2 is an explanatory diagram of a projected image formed in the slit 3 of FIG. 1, and FIG.
The figure is an explanatory diagram of a projected image formed in the slit 5 of FIG.
Fig. 4 is an explanatory diagram of image plane formation by a normal lens, Fig. 5 is an explanatory diagram of image plane formation by a collective optical system lens, Fig. 6 is an explanatory diagram of projection error occurrence, and Fig. 7 is an explanatory diagram of a conventional collective optical system. 8 and 9 are perspective views showing one embodiment of the present invention, FIG. 10 is a perspective view showing another embodiment of the present invention, and FIG. 11 is an application of the present invention. A perspective view showing an example. Explanation of symbols 1... Light source, 2... Condenser lens, 9... Light receiver, 10... Arithmetic circuit, 11... Display unit, 18...
...Diffusion plate, 31.33...Object side slit, 32.
32a, 32b--disc, 40--slit, 10
0... Collective optical system. Patent Applicant: Fuji Xerox Co., Ltd. Agent Nobuyuki Matsuhara, Patent Attorney: Tsuji Muraki, Patent Attorney: Taira 1) Yudo Tadashi, Patent Attorney: Atsushi Ueshima - Patent Attorney: Hitoshi Suzuki Figures 4 and 5 Figure 6 Figure 1O Figure 1I Figure 1゜

Claims (1)

[Claims] A collective optical system to be evaluated which is disposed in a light passage path, and a movable unit which has a grating in which transparent portions and opaque portions are alternately arranged at predetermined intervals and is provided at the rear or front stage of the optical system. In the collective optical system evaluation apparatus, the collective optical system evaluation apparatus is provided with a slit and a fixed slit provided with a narrow cutout groove and provided at the front stage or the rear stage of the optical system, and in which optical Fourier transformation is performed by superimposing the integral images from both the slits. The moving slit is formed by a grating extending radially on the outer edge of the disk, and the grating is positioned in a direction perpendicular and parallel to the reference direction of the collective optical system depending on the position of the rotation center axis of the disk. A collective optical system evaluation device characterized by: