JP2007065555A - Imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging device capable of controlling light quantity on an imaging surface without deteriorating resolution. <P>SOLUTION: The imaging device comprises: a luminous flux splitting means 103 which is disposed between a photographing optical system and the imaging surface and splits luminous flux passing through the photographing optical system and proceeding to the imaging surface in accordance with deflection directions; a focus detection means 112 which outputs a focus state signal based on the luminous flux split by the luminous flux splitting means; and an extinction means 116 which is disposed between the photographing optical system and the imaging surface and eliminates a prescribed deflection component, wherein the extinction means can relatively rotate with respect to the luminous flux splitting means and can control the light quantity on the imaging surface in accordance with the rotation positions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus such as a camera, and more particularly to an imaging apparatus having a light beam splitting unit that splits a light beam taken through a photographing optical system into an imaging surface and a focus detection unit.

  In recent years, miniaturization of cameras has progressed, and along with this, miniaturization of photographing optical systems has also progressed. For this reason, the use of a diaphragm that has been widely used for adjusting the amount of light of a conventional camera has led to a drawback that the resolution is lowered by diffraction and the image is deteriorated in quality. In order to improve this drawback, as shown in Patent Document 1, a technique using a plurality of polarizing plates has been proposed. According to the technique disclosed in Patent Document 1, it is possible to continuously adjust the amount of light while preventing a decrease in resolution by relatively rotating two polarizing plates.

  Conventional focus detection methods used for cameras include a triangulation method used for lens shutter cameras, a contrast detection method used for video cameras, and a pupil division method used for single-lens reflex cameras. . Among these, the focus detection method of the pupil division method is disclosed in Patent Document 2, and the focus state of the photographic lens is determined by correlating two images generated by the light beams transmitted through different pupil regions of the photographic lens. It is to detect.

  In Patent Document 3, a part of a diaphragm is configured by a polarizing plate, and a beam splitter that guides a part of a light beam to the outside of an optical path for AF (autofocus) between the diaphragm and the image sensor, and the beam splitter and the image sensor An optical device including a polarizing plate is disclosed. In this optical device, even when the aperture blade is closed, the light beam transmitted from the portion formed by the polarizing plate reaches the AF sensor and can perform AF. Furthermore, since the light beam is blocked by the polarizing plate provided between the beam splitter and the image pickup device, the closed state is maintained on the image pickup surface. As another embodiment, Patent Document 3 discloses an example in which the entire light beam is covered with a polarizing beam splitter, and the polarizing plate and the beam splitter are configured by the same component, and the same effect can be obtained even in this configuration. .

Patent Document 4 discloses a camera that forms a primary object image formed by a photographing optical system on a two-dimensional light receiving sensor such as a CMOS light receiving sensor and photoelectrically converts the optical image to obtain an image output related to the object. It is disclosed. A digital single-lens reflex camera, which is one of optical devices, incorporates a beam splitter that splits light in a wavelength region near the infrared region without reducing the amount of light in the visible wavelength region. The light beam in the wavelength region near the infrared region divided by the beam splitter is used for focus detection, and the light that travels straight is used for imaging. The beam splitter is made thin by limiting the light splitting action surface of the beam splitter to the range through which the focus detection light beam passes. A beam splitter can be arranged in a small space between the photographing optical system and the mirror that deflects the optical path to the finder optical system without increasing the size of the camera. In addition, by setting the spectral transmittance characteristics of the beam splitter to almost 100% in the visible wavelength range, it is possible to obtain a bright and high-quality image without reducing the amount of light in the visible wavelength range required for imaging object images. ing.
Japanese Patent Laid-Open No. 05-207384 JP 63-18313 A Japanese Patent Laid-Open No. 06-175010 JP 2003-140246 A

  FIG. 20 shows a schematic configuration of the optical device disclosed in Patent Document 1. In the figure, reference numerals 901 and 902 denote polarizing plates that are relatively rotatable. A diaphragm unit 903 composed of polarizing plates 901 and 902 is disposed between an imaging optical system (not shown) and an imaging surface. The amount of light on the imaging surface can be continuously adjusted by relatively rotating the polarizing plates 901 and 902.

  FIG. 21 schematically shows how the light amount is adjusted. In the region 911, all the light beams that have passed through the photographing optical system have passed, and in the region 912, approximately 50% of the light flux that has passed through the photographing optical system has passed through the polarizing plate 901. In the region 913, approximately 0% to approximately 50% of the light beam transmitted through the photographing optical system depending on the relative angle between the polarizing plates 901 and 902 passes. The amount of light that passes through the region 913 and reaches the imaging surface 914 can be continuously controlled between approximately 0% and approximately 50% depending on the relative angle between the polarizing plates 901 and 902.

  However, although the amount of light on the imaging surface can be controlled with the technique of Patent Document 1, 50% of the amount of light is always absorbed by the polarizing plate 901.

  Next, the principle of the focus detection means disclosed in Patent Document 2 is shown in FIG. A field lens 922 is arranged in the same optical axis as the photographing lens 921 for which focus is detected. Two secondary imaging lenses 924a and 924b are arranged at the rear side and symmetrical with respect to the optical axis. The secondary imaging lenses 924a and 924b are often integrally formed and are generally called eyeglass lenses. Sensor arrays 925a and 925b are arranged further rearward of the secondary imaging lenses 924a and 924b. Apertures 923a and 923b are provided in the vicinity of the secondary imaging lenses 924a and 924b.

  The field lens 922 substantially forms an image of the exit pupil of the photographing lens 921 on the pupil planes of the two secondary imaging lenses 924a and 924b. As a result, the light beams incident on the secondary imaging lenses 924a and 924b are emitted from regions of equal areas that do not overlap with each other on the exit pupil plane of the photographing lens 921 and correspond to the secondary imaging lenses 924a and 924b. The luminous flux can be made. The image formed in the vicinity of the field lens 922 is re-imaged on the sensor arrays 925a and 925b by the secondary imaging lenses 924a and 924b. Accordingly, the images on the sensor arrays 925a and 925b are displaced based on the displacement in the optical axis direction of the image formed in the vicinity of the field lens 922. Therefore, it is possible to know the focus state of the photographic lens 921 by detecting the relative positions of the images in the sensor rows 925a and 925b.

を定義して、Ｘ（ｋ）が極小値となるｋを得る方法がある。ここで,ｍａｘ｛ａ，ｂ｝なる演算子はａ，ｂのうち大なるものを抽出すること示す。あるいは

を定義して、Ｙ（ｋ）が極大値となるｋを得る方法がある。ここで、ｍｉｎ｛ａ，ｂ｝なる演算子はａ，ｂのうち小なるものを抽出することを示す。 Various methods for obtaining the focus state of the taking lens 921 from the signals output from the sensor arrays 925a and 925b have already been proposed. Specific examples are shown below. FIG. 23 is a schematic diagram showing signals obtained from the sensor arrays 925a and 925b. In FIG. 23, the horizontal axis represents the pixels forming the sensor array, and the vertical axis represents the amount of light input to the sensor at that point. The sensor columns 925a and 925b are composed of N columns of pixels, and signals from i-th (i = 0, 1,... N−1) of the sensor columns 925a and 925b are respectively A (i) and B (i). And At this time

There is a method for obtaining k where X (k) is a minimum value. Here, the operator max {a, b} indicates that a larger one of a and b is extracted. Or

There is a method of obtaining k where Y (k) is a maximum value. Here, the operator min {a, b} indicates that a smaller one of a and b is extracted.

  Although it is possible to detect the focus state of the target photographing lens by the above-described method, it is needless to say that an appropriate light beam needs to be guided to the focus detection sensor array. Many methods for guiding a light beam to a sensor array for focus detection have been proposed, and an example thereof is Patent Document 3 below.

  A schematic configuration of the optical device disclosed in Patent Document 3 is shown in FIG. In the figure, reference numeral 941 denotes a photographing optical system, 942 denotes a photographic film, a CCD sensor, etc., a light receiving portion having sensitivity only to visible light, and 943 a beam splitter. The image captured by the light receiving unit 942 is developed into a photographic original if it is a film camera, and is displayed on an electronic viewfinder (EVF), recorded in a memory, or output to a printer if it is a digital color camera. Or A dielectric multilayer film is formed on the light splitting functional surface 943a of the beam splitter 943, and approximately 50% of the visible light component of the object light emitted from the photographing optical system 941 is reflected, and the remaining approximately 50% is reflected. To Penetrate. The light reflected by the light splitting function surface 943a is totally reflected by the surface 943b of the beam splitter 943, and is emitted to the outside of the beam splitter 943 through the surface 943c. In this optical apparatus, the beam splitter can be downsized because only the light beam necessary for focus detection is guided to the AF sensor.

  However, in Patent Document 3 described above, if the size of the light splitting functional surface 943a is not large enough to cover the entire imaging light flux, luminance unevenness occurs in an image captured using straight light, and the quality is significantly impaired. . Further, if the beam splitter 943 is arranged in the vicinity of the pupil plane of the photographing optical system, luminance unevenness is unlikely to occur, but the amount of light passing through the central portion of the pupil is reduced, which is not preferable because the contrast of the image is lowered. .

  Further, the visible light that has passed through the light splitting function surface 943a is attenuated to ½ as described above. Therefore, assuming that the object to be imaged is a uniform luminance surface, the image captured by the light receiving unit 942 has bright areas 952 and 953 above and below the dark area 951 at the center as shown in FIG. The formed image 950 is obtained. Such a phenomenon is not preferable because an unnatural brightness difference is conspicuous in a portion that should have a uniform brightness particularly when a blue sky or a white wall of a building is photographed, resulting in an image with very poor quality.

  In another embodiment of the optical device disclosed in Patent Document 3, the polarization beam splitter is enlarged to cover the entire light beam with the polarization beam splitter, and as a result, the dimension between the optical lens group and the image sensor is reduced. It is difficult to reduce the size of the apparatus.

  Next, the technique disclosed in Patent Document 4 will be described. In general, in an optical structure in which an optical path of a light beam taken through a photographing optical system is divided into a plurality of parts and guided to a light receiving unit, the wavelength characteristics of the plurality of divided light beams are often substantially the same. If you will produce benefits.

  However, in the camera of Patent Document 4, a light beam in the near-infrared wavelength region divided by the beam splitter is used for focus detection. Therefore, in order to make the focus detection function correctly, aberration correction of the photographing optical system is also performed in this wavelength region. Need to be. When aberration correction is insufficient, it is impossible to strictly focus the visible wavelength range using light in the infrared range. On the other hand, if aberration correction is to be performed near the infrared region in addition to the visible wavelength region, it is necessary to take measures such as using special glass or increasing the number of lenses constituting the photographing optical system. Therefore, it causes an increase in cost and size, which is not preferable. In particular, if the photographic optical system is interchangeable like a single-lens reflex camera and has a large-scale interchangeable lens system, the entire interchangeable lens system needs to be compatible with such a focus detection system. It can be said that it is extremely difficult.

  A phenomenon similar to focus detection also occurs when the object luminance is measured using the light beam divided by the beam splitter and the imaging exposure amount is determined. That is, if the wavelength range for luminance measurement deviates from the wavelength range for imaging, the light energy included in the wavelength range for exposure can be estimated from the amount of light energy included in the wavelength range for luminance measurement. Strictly not. Due to this, even if the exposure amount is determined based on the measurement of the object luminance and imaging is performed, an underexposed or overexposed imaging result may occur.

(Object of invention)
An object of the present invention is to provide an imaging apparatus capable of controlling the amount of light on the imaging surface without reducing the resolution.

  It is another object of the present invention to provide an imaging apparatus capable of performing focus detection with a sufficient divided light beam.

  Furthermore, an object of the present invention is to provide an image pickup apparatus capable of reducing the size of the light beam splitting means.

  In order to achieve the above object, the invention according to claim 1 is a light beam splitting device that is arranged between a photographing optical system and an imaging surface, and that splits a light beam that passes through the photographing optical system and travels toward the imaging surface according to a deflection direction. Means, focus detection means for outputting a focus state signal based on the light beam split by the light beam splitting means, and dimming means disposed between the photographing optical yarn and the imaging surface to remove a predetermined deflection component The dimming means is rotatable relative to the light beam splitting means, and the amount of light on the imaging surface can be adjusted by the rotational position.

  According to a second aspect of the present invention, there is provided the first position where the dimming unit absorbs the same deflection component as the deflection component of the beam guided to the focus detection unit by the beam splitting unit, and the beam splitting. 2. The imaging apparatus according to claim 1, wherein the imaging apparatus is rotatable between a second position that absorbs the same deflection component as the deflection component of the light beam transmitted through the means.

  According to a third aspect of the present invention, the focus detection is performed by the beam splitting unit between one or both of the beam splitting unit and the photographing optical system and between the beam splitting unit and the dimming unit. The imaging apparatus according to claim 1, further comprising a second dimming unit that absorbs the same polarization component as the polarization component of the light beam guided to the unit.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device which can control the light quantity on an imaging surface can be provided, without reducing the resolution.

  The best mode for carrying out the present invention is as shown in Examples 1 to 3 below.

  A digital camera which is an image pickup apparatus according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a digital camera and shows a state in which an image for EVF (Electronic View Finder) is captured by performing focus adjustment. In the figure, reference numeral 101 denotes a digital camera body, 102 denotes a photographing optical system for forming an object image, 104 denotes an optical axis of the photographing optical system 102, and 105 denotes a lens barrel that houses the photographing optical system 102. The imaging optical system 102 can adjust the imaging position in the direction of the optical axis 104 by an energy source (not shown) and a driving mechanism (not shown). The focusing lens can be composed of a flexible transparent elastic member or a liquid lens, and the object can be focused by changing the refractive power by changing the interface shape. The photographing optical system 102 may be a single focus lens, a zoom lens, a shift lens, or the like. Further, it may be replaceable with a photographing optical system having various characteristics (F number, focal length, etc.).

  Reference numeral 103 denotes a beam splitter, 111 denotes a shutter release button, and 107 denotes a display device. Reference numeral 108 denotes a memory for storing image data, 109 denotes an eyepiece of an optical viewfinder, and 110 denotes a communication device that performs data communication with a printer or the like. 106 is a two-dimensional CMOS light receiving sensor, 112 is a focus detection sensor, and 113 is an optical low-pass filter.

  A dimming means 116 is provided between the beam splitter 103 and the optical low-pass filter 113. The dimming means 116 engages with a mechanical drive means (not shown), rotates relative to the beam splitter 103 based on a signal from a photometric sensor or image sensor 106 (not shown), and is controlled to an appropriate position. The When the EVF image is captured, the light beam that has passed through the beam splitter 103 is projected onto the CMOS light receiving sensor 106.

  The display device 107 is attached to the back of the camera, and an object image captured by the CMOS light receiving sensor 106 is displayed on the display device 107. The user can observe this directly as EVF.

  The CMOS light receiving sensor 106 is a CMOS process compatible sensor which is one of the amplification type solid-state imaging devices. The CMOS light receiving sensor 106 can form peripheral circuits such as a MOS transistor of the area sensor unit, an image sensor driving circuit, an AD conversion circuit, and an image processing circuit in the same process. For this reason, there is an advantage that the number of masks and process steps can be greatly reduced as compared with the CCD. In addition, there is a feature that random access to an arbitrary pixel is possible. When readout is performed by thinning out pixels, an image can be displayed in real time at a high display rate. Using this feature, the CMOS light receiving sensor 106 performs an EVF image output operation by thinning readout and a high-definition image output operation for reading all pixels.

  FIG. 2 is a block diagram showing an electrical configuration of the digital camera. First, an explanation will be given from the part related to the imaging and recording of object images.

  The digital camera has an imaging system, an image processing system, a recording / reproducing system, and a control system. The imaging system includes a photographing optical system 102 and a CMOS light receiving sensor 106, and the image processing system includes an A / D converter 130, an RGB image processing circuit 131, and a YC processing circuit 132. The recording / reproducing system includes a recording processing circuit 133 and a reproduction processing circuit 134. The control system includes a camera system control circuit 135, an operation detection circuit 136, and a CMOS light receiving sensor drive circuit 137. Reference numeral 138 denotes a standardized connection terminal for connecting to an external computer or the like to transmit / receive data. These electric circuits are driven by a small fuel cell (not shown).

  The imaging system is an optical processing system that forms an image of light from an object on the imaging surface of the CMOS light receiving sensor 106 via the imaging optical system 102, and adjusts the relative angle between the beam splitter 103 and the dimming means 116 to appropriately A large amount of object light is exposed to the CMOS light receiving sensor 106. This operation will be described in detail later. The CMOS light receiving sensor 106 is a light receiving element in which 3700 square pixels are arranged in the long side direction and 2800 in the short side direction, and the total number of pixels is about 10 million. Then, R (red), G (green), and B (blue) color filters are alternately arranged in each pixel to form a so-called Bayer array in which four pixels are a set.

  The RGB image processing circuit 131 processes an image signal of the number of pixels of the light receiving sensor received from the CMOS light receiving sensor 106 via the A / D converter 130. It has an interpolation operation circuit that performs resolution. The YC processing circuit 132 is a signal processing circuit that generates a luminance signal Y and color difference signals RY and BY. The circuit includes a circuit that generates a high-frequency luminance signal YH, a circuit that generates a low-frequency luminance signal YL, and a circuit that generates color difference signals RY and BY. The luminance signal Y is formed by combining the high frequency luminance signal YH and the low frequency luminance signal YL.

  The recording / reproducing system is a processing system that outputs an image signal to the memory and an image signal to the display device 107, and the recording processing circuit 133 performs a writing process and a reading process of the image signal to the memory. Further, the reproduction processing circuit 134 reproduces the image signal read from the memory and outputs it to the display device 107.

  The recording processing circuit 133 includes a compression / expansion circuit that compresses YC signals representing still images and moving images in a predetermined compression format and expands the compressed data when it is read out. This compression / decompression circuit includes a frame memory for signal processing and the like, accumulates YC signals from the image processing system for each image in the frame memory, reads out each of the plurality of blocks, and performs compression encoding. The compression encoding is performed, for example, by subjecting the image signal for each block to two-dimensional orthogonal transformation, normalization, and Huffman encoding.

  The reproduction processing circuit 134 is a circuit that performs matrix conversion on the luminance signal Y and the color difference signals RY and BY, for example, into RGB signals. The signal converted by the reproduction processing circuit 134 is output to the display device 107, and a visible image is displayed and reproduced. The reproduction processing circuit 134 and the display device 107 or the printer may be connected via wireless communication means such as Bluetooth. If comprised in this way, it will become possible to monitor the image imaged with this digital camera from a remote place, and to print the imaged image without going through a personal computer.

  The control system includes an operation detection circuit 136 that detects an operation of the shutter release button 111 and the like, and a camera system control circuit 135 that controls each unit in response to the detection signal and generates and outputs a timing signal at the time of imaging. including. Also included is a CMOS light receiving sensor driving circuit 137 that generates a driving signal for driving the CMOS light receiving sensor 106 under the control of the camera system control circuit 135. Furthermore, an information display circuit 142 for controlling the information display device in the optical viewfinder and the information display device on the outer surface of the camera is also included.

  The control system controls an imaging system, an image processing system, and a recording / reproducing system in response to an external operation. For example, pressing of the shutter release button 111 is detected to control the driving of the CMOS light receiving sensor 106, the operation of the RGB image processing circuit 131, the compression processing of the recording processing circuit 133, and the like. Further, the information display circuit 142 controls the state of each segment of the information display device that displays information on an optical finder or the like.

  An AF control circuit 140 and a lens system control circuit 141 are further connected to the camera system control circuit 135. These communicate with each other data necessary for each processing, centering on the camera system control circuit 135.

  The AF control circuit 140 obtains the signal output of the focus detection field of the focus detection sensor 112 set corresponding to a predetermined position on the shooting screen, generates a focus detection signal, and changes the imaging state of the shooting optical system 102. To detect. When the defocus amount is detected, this is converted into a driving amount of a focusing lens which is a part of the photographing optical system 102, and is transmitted to the lens system control circuit 141 via the camera system control circuit 135. For a moving object, the focusing lens drive amount is instructed by predicting an appropriate lens position in consideration of a time lag from when the shutter release button 111 is pressed until actual imaging control is started. When it is determined that the brightness of the object is low and sufficient focus detection accuracy cannot be obtained, the object is illuminated by a flash light emitting device (not shown) or a white LED or fluorescent tube (not shown) to compensate for the insufficient brightness. When receiving the driving amount of the focusing lens, the lens system control circuit 141 moves the focusing lens in the photographing optical system 102 in the direction of the optical axis 104 by a driving mechanism (not shown) to focus on the object.

  As a result of a series of focus adjustment operations, when the AF control circuit 140 detects that the object is in focus, this information is transmitted to the camera system control circuit 135. At this time, if the shutter release button 111 is pressed down to the second level, the imaging control by the imaging system, the image processing system, and the recording / reproducing system is performed as described above.

  FIG. 3 is a cross-sectional view of the lens barrel 105 portion of the digital camera 101. FIG. 4 is a schematic diagram of a functional unit 118 including the beam splitter 103, the dimming unit 116, the condenser lens 114, the spectacle lens 117, and the focus detection sensor 112. The functional unit 118 and its peripheral part will be described in detail with reference to these drawings.

  The beam splitter 103 is located between lenses 102a and 102b (not shown) constituting the photographing optical system 102. The lens 102a is a focusing lens, and performs focus adjustment by moving in the direction of the optical axis 104, for example. The CMOS light receiving sensor 106 is disposed on the planned imaging surface of the photographing optical system 102, and the cover glass 106 a of the CMOS light receiving sensor 106 is fixed via a sealing member 115. By adopting such a configuration, there is no possibility of dust adhering to the cover glass 106a of the CMOS light receiving sensor 106. If there is a possibility of dust adhering, it becomes the incident surface of the lens 102b. Since the distance from the light receiving surface of the CMOS light receiving sensor 106 to the position of the dust is sufficiently long, the dust attached to the incident surface of the lens 102b (not shown) hardly appears on the screen.

  The schematic imaging sequence is performed as in the example shown in FIG. That is, the digital camera waits for the shutter release button 111 to be operated by turning on the power, and performs autofocus operation when the switch SW1 (not shown) is turned on (# 101) by pressing the first release button (# 101). 102- # 105). Then, when the switch SW2 (not shown) is turned on by pressing the shutter release button 111 in the second step (# 106), image capturing and information storage in the memory 108 are performed (# 108, # 109). After that, it returns to the state of waiting for the switch SW1 to be turned on again.

  Next, light beam splitting will be described. As shown in FIG. 4, the beam splitter 103 has a light splitting function surface 103a that can split a light beam according to the polarization direction. The schematic diagram of the functional unit 118 shown in FIG. 4 shows an example in which the light splitting functional surface 103a is formed as a polarization beam splitter formed of a dielectric multilayer film or the like. The light incident surface of the beam splitter 103 is constituted by a surface 103b, and the exit surface of the straight light is constituted by a surface 103d. The surface 103b and the surface 103d are substantially parallel. Further, the beam splitter 103 is provided so as to cover all the light fluxes directed to the CMOS light receiving sensor 106. By doing so, the beam splitter 103 functions as a parallel plate for light traveling straight. Further, a luminance distribution such as a part of the image becomes dark in order to cover all the light fluxes directed to the CMOS light receiving sensor 106 does not occur, and a high-quality image can be obtained.

  Desirable optical characteristics of the light splitting functional surface 103a are, for example, as shown in FIG. 6, and have high transmittance in the visible light region for P-polarized light and high reflectance for S-polarized light. With this configuration, of the light beam incident on the beam splitter 103, the S-polarized light component is reflected by the light splitting function surface 103a and emitted downward from the surface 103c in the drawing. A condenser lens 114 that functions to collect a light beam used for focus detection is disposed at a position facing the surface 103c. Then, the light transmitted through the condenser lens 114 is incident on the focus detection sensor 112 via the eyeglass lens 117, and the focus detection function by the pupil division method is thereby operated. That is, it is possible to grasp the focus state of the photographing optical system 102 from the light beam incident on the focus detection sensor 112.

  The optical characteristics of the light splitting function surface 103a are as described above, and the spectral characteristics of the light beam split by the beam splitter 103 are made substantially the same as those of the straight traveling light, and the focus detection function is operated by this light beam. The spectral characteristic incident on the focus detection sensor 112 is dominated by the spectral characteristic of the reflectance of the S-polarized light on the light splitter surface 103a. However, as shown in FIG. 6, by using the light splitting function surface 103a having a high reflectance regardless of the wavelength, a sufficient amount of light and a substantially same light flux as the light incident on the imaging surface can be obtained. High-precision focus detection is possible.

  Between the beam splitter 103 and the CMOS light receiving sensor 106, a dimming means 116 which is a so-called polarization filter is disposed. The dimming means 116 is between a first position where the S-polarized light is absorbed (blocked) in the beam splitter 103 and a second position where the P-polarized light is absorbed (blocked) in the beam splitter 103 by a driving means (not shown). It is configured to be movable.

  FIG. 7 shows a preferable spectral transmittance characteristic of the light reducing means 116 formed of a polarizing filter. As a suitable characteristic of a polarizing filter used for an LCD or the like, an extinction ratio in a so-called crossed Nicol state is important. For this reason, it is common to select a high transmittance within a range where the extinction ratio can take a desired value. However, in this embodiment, an extinction ratio of about 50: 1 is sufficient. On the other hand, spectral characteristics and transmittance are more important characteristics in order not to deteriorate the color and brightness of the image on the CMOS light receiving sensor 106.

  Next, the functional unit 118, which is the main configuration of the present embodiment, will be described with reference to FIGS. FIG. 8 is a diagram for explaining the division of the light flux and the amount of light in the functional unit 118. FIG. 9 is a diagram for explaining the relationship between the light amount at the CMOS sensor 106 and the relative position between the light reducing means 116 and the beam splitter 103.

  In FIG. 8, reference numeral 150 denotes a light beam that has passed through the photographing optical system 102. Reference numeral 151 denotes a light beam that is split by the light splitting function surface 103 a and guided to the focus detection sensor 112. Reference numeral 152 denotes a light flux that passes through the light splitting functional surface 103a and travels to the light reducing means 116. Reference numeral 153 denotes a light flux that passes through the dimming means 116 and travels toward the CMOS light receiving sensor 106.

  In FIG. 9, only the central light beam is indicated by a line. In FIG. 9, 116 a indicates the polarization azimuth angle of the dimming means 116. FIG. 9A shows a first position of the dimming means 116 that absorbs the same polarization component as the polarization component guided to the focus detection sensor 112 by the light splitting function surface 103a. FIG. 9C shows a second position of the dimming means 116 that absorbs the same polarization component as the polarization component transmitted through the light splitting function surface 103a. FIG. 9B shows a state in which the dimming means 116 is between the first position and the second position.

  As schematically shown in FIG. 8, the light beam guided to the focus detection sensor 112 may be only the light beam necessary for the focus detection operation. Therefore, in this embodiment, the light splitting functional surface 103a exists so as to cover all the light fluxes 150 that have passed through the photographing optical system 102, but some of them do not reach the focus detection sensor 112 but pass through.

  When the dimming means 116 is in the first position shown in FIG. 9A, the light amount of the light beam 150 that has passed through the photographing optical system 102 is 100, and the characteristics of the light splitting functional surface 103a are as shown in FIG. To do. In this case, the light flux 151 of the light flux 151 guided to the focus detection sensor 112 is 45 or more, the light flux 152 of the light flux 152 going to the dimming means 116 is 45 or more, and the light flux of the light flux 153 going to the CMOS light receiving sensor 106 is 40.5. That's it.

  Further, when the dimming means 116 is in the second position shown in FIG. 9C, the luminous flux 151 of the luminous flux 151 guided to the focus detection sensor 112 is 45 or more, and the luminous flux 152 directed to the dimming means 116. The amount is 45 or more, and the amount of the light beam 153 directed to the CMOS light receiving sensor 106 is about 2. 9B, the light amount can be continuously changed by the polarization azimuth angle 116a of the dimming means 116.

  That is, the amount of light at the CMOS light receiving sensor 106 can be controlled by the polarization azimuth angle 116 a of the light reducing means 116, and can be used as an aperture of the photographing apparatus as disclosed in Patent Document 1. In addition, unlike a conventional mechanical aperture, even when the apparatus is downsized, there is no problem of a reduction in resolution due to a diffraction phenomenon.

The first embodiment has the following effects.
(1) The dimming means 116 is rotatable relative to the beam splitter 103 which is a light beam splitting means. That is, as shown in FIG. 9, the dimming means 116 is rotatable between the first position (position of FIG. 9 (a)) and the second position ((position of FIG. 9 (c)). Since the polarization azimuth angle 116a is variable, the amount of light on the CMOS light receiving sensor 106 can be continuously changed without causing a decrease in resolution due to a diffraction phenomenon.
(2) The beam splitter 103 is provided so as to cover all the light beams traveling toward the CMOS light receiving sensor 106. Therefore, as shown in FIG. 25, a luminance distribution such as a part of the image on the CMOS light receiving sensor 106 becomes dark does not occur. Therefore, an image of the beam splitter 103 is not captured on the CMOS light receiving sensor 106, and a high-quality image can be obtained.
(3) Of the light beam incident on the beam splitter 103, the P-polarized component is transmitted and the S-polarized component is reflected by the light splitting function surface 103a. Therefore, focus detection can be performed with substantially the same light beam as the light beam guided to the CMOS light receiving sensor 106.

  As described above, many effects can be obtained with a simple configuration, and it can be said that the effect of using the beam splitter 103 that covers the entire light beam toward the CMOS light receiving sensor 106 and the dimming means 116 using the polarized light is extremely great.

  Next, a digital camera that is an image pickup apparatus according to the second embodiment of the present invention will be described with reference to FIGS.

  10 and 11 are cross-sectional views of the digital camera. In FIG. 10, 201 is a digital camera body, and 202 is a photographing optical system for forming an object image. Reference numeral 204 denotes an optical axis of the photographing optical system 202, and 205 denotes a lens barrel that houses the photographing optical system 202. A beam splitter 203, a shutter release button 211, a display device 207, and a memory 208 store image data. Reference numeral 209 denotes an eyepiece of an optical viewfinder, and 210 denotes a wireless communication device that performs data communication with a printer or the like. 206 is a two-dimensional CMOS light receiving sensor, 212 is a focus detection sensor, 213 is an optical low-pass filter, 214 is a condenser lens, 216 is a dimming means, and 217 is a spectacle lens. Since each function is the same as that of the first embodiment, description thereof is omitted. The electrical circuit configuration is the same as that shown in FIG.

  Reference numeral 219 denotes a quarter-wave plate that converts the linearly polarized light transmitted through the dimming means 216 into circularly polarized light. The quarter-wave plate 219 is positioned with respect to the dimming means 216 in order to have the above function, and operates as a unit. 220a is a second dimming means. A functional unit 218 includes a beam splitter 203, a dimming unit 216, a condenser lens 214, a spectacle lens 217, a focus detection sensor 212, a quarter wavelength plate 219, and a second dimming unit 220a.

  As shown in FIG. 11, the functional unit 218 can be retracted from the optical path from the photographing optical system 202 to the CMOS light receiving sensor 206 by a driving unit (not shown). This evacuation operation is performed when it is determined that a decrease in the amount of light by the functional unit 218 is a problem.

  Detailed examples of the functional unit 218 in the second embodiment are shown in FIGS. 12 (a) to 12 (c).

  12A to 12C, the incident surface of the beam splitter 203 is constituted by two coincident surfaces 203b and 203c, and the exit surface is constituted by two coincident surfaces 203e and 203f. By doing so, the beam splitter 203 functions as a parallel plate for light traveling straight. The light splitting function surface 203a is arranged so as to cover only the area necessary for focus detection out of the light flux that has passed through the photographing optical system 202. A light beam divided by the light dividing function surface 203a and directed to the focus detection sensor 212 is emitted from the surface 203d. A condenser lens 214 that collects a light beam used for focus detection is disposed at a position facing the surface 203d. The light transmitted through the condenser lens 214 is incident on the focus detection sensor 212 via the eyeglass lens 217, and the focus detection function by the pupil division method is thereby operated. That is, it is possible to grasp the focus state of the photographing optical system 202 from the light flux incident on the focus detection sensor 212.

  As is apparent from FIG. 12, by providing the light splitting function surface 203a only in the area necessary for focus detection, the beam splitter 203 can be made thinner in the optical axis direction than in the first embodiment. .

  FIG. 12A shows an example in which the second dimming means 220 a is disposed between the photographing optical system 202 and the beam splitter 203.

  The second dimming means 220a arranged above and below is constituted by a polarizing filter in the same manner as the first dimming means 216, and the characteristics thereof are as shown in FIG. At this time, the second dimming means 220a is provided in the direction of absorbing (blocking) the P-polarized light on the light splitting function surface 203a of the beam splitter 203. Further, the second dimming means 220a is provided with an opening 220c, and the opening 220c is opened at the portion of the light splitting functional surface 203a of the beam splitter 203 when viewed from the object side along the optical axis. It is provided as it is. The second dimming means 220a disposed at the above position is positioned and fixed with respect to the beam splitter 203.

  By providing the opening 220c under the above conditions, when the photographing optical system 202 is close to a telecentric optical system, the light beam incident on the functional unit 209 through the photographing optical system 202 is reflected by the second dimming means 220a and the light splitting. The light passes through only one of the functional surfaces 203a toward the first dimming means 216.

  Further, the first dimming means 216 absorbs and cuts off S-polarized light on the light splitting function surface 203a by the driving means (not shown) with the optical axis as the center with respect to the second dimming means 220a and the beam splitter 203. And a second position that absorbs P-polarized light on the light splitting function surface 203a. By appropriately moving the first dimming means 216, as disclosed in Patent Document 1, it is possible to obtain a desired light amount on the imaging surface.

  FIG. 13A shows a schematic diagram for explaining the light quantity of the example shown in FIG. In FIG. 13A, reference numerals 250a, 250b, and 250c denote light beams that have passed through the photographing optical system 202. Reference numerals 251a and 251c denote light beams that pass through the second dimming means 220a and travel toward the dimming means 216. Reference numeral 251b denotes a light flux that passes through the opening 220c provided in the second dimming means 220a and travels toward the light splitting functional surface 203a. Reference numeral 251d denotes a light flux that passes through the light splitting function surface 203a and travels toward the light reducing means 216. Reference numerals 252a, 252b, and 252c denote light beams that pass through the first dimming means 216 and travel toward the CMOS light receiving sensor 206. Reference numeral 253 denotes a light beam that is split by the light splitting function surface 203 a and guided to the focus detection sensor 212.

  In FIG. 13A, the amount of light beams 250a, 250b, 250c that have passed through the photographing optical system 202 is set to 100, and the characteristics of the light splitting functional surface 203a are the same as those shown in FIG. The characteristics of the second dimming means 220a are as shown in FIG. In this case, the amount of the light beam 253 guided to the focus detection sensor 212 is 45 or more, and the light beams 251a and 251c that pass through the second dimming means 220a or the light splitting function surface 203a and go to the first dimming means 216. , 251d are 45 or more. The light beams 252a, 252b, and 252c transmitted through the first dimming means 216 are all the same, and are approximately 0 to approximately 40 depending on the relative angle between the first dimming means 216 and the light splitting function surface 203a. It is variable. That is, the entire surface is uniform and the light quantity is variable.

  The functional unit 218 includes a quarter-wave plate 219 between the first dimming means 216 and the optical low-pass filter 213 (see FIG. 10) not shown in FIG. The linearly polarized light that has passed through the first dimming means 216 is converted into circularly polarized light. When the optical low-pass filter 213 using birefringence is used, when linearly polarized light is incident, the optical low-pass filter 213 may not work properly and may generate a false color. By disposing the quarter wavelength plate 219 between the first dimming means 216 and the optical low-pass filter 213, the above problem is eliminated. The quarter wavelength plate 219 may be arranged as a so-called circular polarization filter integrated with the first dimming means 216.

  In FIG. 12B, the second dimming means 220a and the second dimming means 220b are arranged between the imaging optical system 202 and the beam splitter 203, and both the beam splitter 203 and the first dimming means 216. This is an example of arrangement.

  The second light attenuating means 220a and 220b are configured by a polarizing filter in the same manner as the first light attenuating means 216, and the characteristics thereof are as shown in FIG. The first dimming means 216 is constituted by a circularly polarizing filter integrally provided with a quarter wavelength plate. At this time, the second dimming means 220a is provided in the direction of absorbing (blocking) the P-polarized light on the light splitting function surface 203a of the beam splitter 203. The second dimming means 220a is provided so as to cover one portion where the light splitting functional surface 203a does not exist when viewed from the optical axis direction, and the second dimming means 220b covers the other side. It is provided as follows. The second dimming means 220a and 220b arranged at the above positions are positioned and fixed with respect to the beam splitter 203.

  By providing the dimming means by dividing under the above conditions, the light beam incident on the functional unit 218 through the photographing optical system 202 is only one of the second dimming means 220a and 220b and the light dividing functional surface 203a. To the first dimming means 216.

  Compared to the example shown in FIG. 13A, the light beam that passes through the photographing optical system 202 and travels toward the CMOS light receiving sensor 206 has a large angle with respect to the optical axis. Uniform luminance can be obtained.

  Further, the first dimming means 216 is driven around the optical axis with respect to the second dimming means 220a and the beam splitter 203. Specifically, it is possible to move between a first position that absorbs S-polarized light on the light splitting functional surface 203a and a second position that absorbs P-polarized light on the light splitting functional surface 203a by driving means (not shown). By appropriately moving the first dimming means 216, a desired amount of light can be obtained on the imaging surface as disclosed in Patent Document 1.

  FIG. 12C shows an example in which the second dimming means 220 a is disposed between the beam splitter 203 and the first dimming means 216.

  The second dimming means 220a is disposed so as to cover all the light beams that pass through the photographing optical system 202 and go to the CMOS light receiving sensor 206. Similar to the first dimming means 216, the second dimming means 220a is composed of a polarizing filter, and the characteristics thereof are as shown in FIG. The first dimming means 216 is composed of a circularly polarizing filter integrally provided with a quarter wavelength plate. At this time, the second dimming means 220a is provided in the direction of absorbing (blocking) P-polarized light on the light splitting function surface 203a of the beam splitter 203. The second dimming means 220a disposed at the position is positioned and fixed with respect to the beam splitter 203.

  Further, the first dimming means 216 is driven around the optical axis with respect to the second dimming means 220a and the beam splitter 203. Specifically, it is possible to move between a first position that absorbs S-polarized light on the light splitting functional surface 203a and a second position that absorbs P-polarized light on the light splitting functional surface 203a by a driving unit (not shown). By appropriately moving the first dimming means 216, a desired amount of light can be obtained on the imaging surface as disclosed in Japanese Patent Laid-Open No. 05-207384.

  FIG. 13B shows a schematic diagram for explaining the light quantity of the example shown in FIG. In FIG. 13B, 260a, 260b, and 260c indicate light beams that have passed through the photographing optical system 202. Reference numeral 261a denotes a light flux that passes through the light splitting function surface 203a and travels toward the second dimming means 220a. Reference numerals 262a, 262b, and 262c denote light beams that pass through the second dimming unit 220a and travel toward the first dimming unit 216. Reference numerals 263a, 263b, and 263c denote light beams that pass through the first dimming means 216 and travel toward the CMOS light receiving sensor 206. Reference numeral 264 denotes a light beam that is split by the light splitting function surface 203 a and guided to the focus detection sensor 212. At this time, desirable characteristics of the light splitting function surface 203a are as shown in FIG. 14, for example. Since the transmittance of P-polarized light is high and S-polarized light is absorbed by the second dimming means 220a, it is not strictly regulated.

  In FIG. 13A, the amount of light fluxes 250a, 250b, 250c that have passed through the photographing optical system 202 is 100, and the characteristics of the light splitting functional surface 203a are those shown in FIG. 14, the first dimming means 216, and The characteristics of the second dimming means 220a are as shown in FIG. In this case, the amount of the light beam 253 guided to the focus detection sensor 212 is 42 or more, and the amount of the light beam 261a passing through the second dimming means 220a or the light splitting function surface 203a to the second dimming means 220a is 47. That's it. The luminous fluxes 262a and 262c transmitted through the second dimming means 220a are 45 or more, and the luminous flux 262b is 43 or more. That is, by increasing the transmittance of the P-polarized light on the light splitting function surface 203a, the light beams 262a, 262b, and 262c can all have substantially the same light beam amount. As a result, the light beams 263a, 263b, 263c transmitted through the first dimming means 216 are all the same, and are approximately 0 to approximately 40 depending on the relative angle between the first dimming means 216 and the light splitting function surface 203a. It is variable. That is, the entire surface is uniform and the light quantity is variable.

  Next, the rotation operation of the functional unit 218 will be described with reference to FIG. FIG. 15 is a view of the camera including the functional unit 218 as viewed from the front. For explanation, the X and Y axes are set as shown in FIG.

  The functional unit 218 is disposed so as to be capable of rotating 90 degrees or more around the optical axis at the position inserted in the optical path. As an example, when the focus detection sensor 212 is in the Y direction as shown in FIG. 15A, the focus detection sensor 212 is in the X direction as shown in FIG. 15B. Let the case be the position of the second position. The first position and the second position do not necessarily need to be set as described above as long as they can be rotated by 90 degrees or more.

  In the second embodiment, the second dimming means 220a and the light splitting function surface 203a selectively perform dimming and splitting according to the polarization direction. Therefore, the camera can be used as a so-called polarizing filter by being rotated around the optical axis as a unit with the functional unit 218. Specifically, at the position shown in FIG. 15A, the X-axis direction is the S-polarized light of the light splitting function surface 203a, so that polarized light having an electric field vector in the X-axis direction does not reach the CMOS light receiving sensor 206. Only polarized light having an electric field vector in the Y-axis direction reaches the CMOS light receiving sensor 206. The opposite is true in FIG.

  The polarizing filter is controlled appropriately by means disclosed in, for example, Japanese Patent Laid-Open No. 2001-1000028, or manually by a user. By utilizing a polarizing filter, a desired image can be obtained even in a scene such as night scene photography through glass where it is desired to remove specular reflection light.

  The quarter wavelength plate 219 is effective even when used in the above-described first embodiment.

According to the second embodiment, the following effects can be obtained.
(1) An image of the beam splitter 203 is not captured on the CMOS light receiving sensor 206, and a high-quality image can be obtained.
(2) Focus detection can be performed with substantially the same light beam as the light beam guided to the CMOS light receiving sensor 206.
(3) The amount of light on the CMOS light receiving sensor 206 can be continuously changed without causing a reduction in resolution.
(4) The beam splitter 203 can be downsized, and the apparatus can be downsized.
(5) Appropriate imaging can be performed even for low-luminance subjects.
(6) Even an imaging system having an optical LPF (low-pass filter) using birefringence does not generate false colors.
(7) Shooting is possible by utilizing the built-in polarizing filter.

  As described above, many effects can be obtained with a simple configuration, and the polarization beam splitter 203 that covers the range necessary for focus detection out of the light flux directed to the CMOS light receiving sensor 206 and the dimming means (220a) using polarized light. , 220b, 216), the effect that the functional unit 218 can be retracted out of the optical path, and the effect that the functional unit 218 can be rotated are extremely large.

  Next, a digital camera which is an image pickup apparatus according to Embodiment 3 of the present invention will be described with reference to FIGS.

  16 and 17 are cross-sectional views of the digital camera. In the figure, reference numeral 301 denotes a digital camera body, 302 denotes a photographing optical system for forming an object image, 304 denotes an optical axis of the photographing optical system 302, and 305 denotes a lens barrel that houses the photographing optical system 302. Reference numeral 303 denotes a beam splitter, 311 denotes a shutter release button, 307 denotes a display device, and 308 denotes a memory for storing image data. Reference numeral 309 denotes an eyepiece of an optical viewfinder, and 310 denotes a wireless communication device that performs data communication with a printer or the like. Reference numeral 306 denotes a two-dimensional CMOS light receiving sensor, 312 denotes a focus detection sensor, 313 denotes an optical low-pass filter, 314 denotes a condenser lens, 316 denotes first dimming means, and 317 denotes a spectacle lens. Since the respective functions are the same as those in the first embodiment, the description thereof is omitted. The electrical configuration is the configuration shown in FIG.

  Reference numeral 330 denotes a film-like second dimming means. A functional unit 318 includes a beam splitter 303, a first dimming unit 316, a condenser lens 314, a spectacle lens 317, a focus detection sensor 312, and a second dimming unit 330.

  As shown in FIG. 17, the functional unit 318 can be retracted from the optical path from the photographing optical system 302 to the CMOS light receiving sensor 306 by a driving unit (not shown). This evacuation operation is performed when it is determined that a decrease in the amount of light by the functional unit 318 is a problem.

  The functional unit 318 in the third embodiment will be described with reference to FIGS. 18 and 19. 18 is a detailed diagram of the functional unit 318, and FIG. 19 is a diagram illustrating an example of a method of creating the beam splitter 303.

  In FIG. 18, the film-like second dimming means 330 has a function of splitting a light beam according to the polarization direction at the incident angle of the characteristic and transmitting substantially half of the light beam at the time of vertical incidence. For example, a dielectric multilayer film that functions as a polarizing beam splitter when incident from an optical plastic is deposited on a film.

  The beam splitter 303 is integrated with the second dimming unit 330 as shown in FIG. As shown in FIG. 19A, the beam splitter 303 includes two prisms 303a and 303b. After inserting the film-like second dimming means 330 between the prism 303a and the prism 303b, as shown in FIG. 19B, the two prisms 303a and prism 303b is fixed. Further, the end portion of the film-like light reducing means 330 is appropriately processed to form an integrated prism 330 as shown in FIG.

  According to the third embodiment, since the dimming surface is integrally formed, the discontinuity of the dimming surface does not affect the image, and a high-quality image can be obtained. For example, duplication and gaps between a plurality of dimming means tend to affect the image. Even when the functional unit 318 is disposed in the vicinity of the CMOS light receiving sensor 306, a high-quality image can be obtained. Further, since the dimming means is integrally formed, the cost can be reduced.

  According to the third embodiment, the cost of the apparatus can be reduced without impairing the effects of the first and second embodiments.

  According to the first to third embodiments described above, the light beam splitting unit is configured by the beam splitter (103, 203, 303) capable of splitting the light beam according to the so-called polarization direction. The light receiving means (116, 216, 220a, 220b, 316, 330) are provided between the CMOS light receiving sensors (106, 206, 306). The dimming means absorbs the same polarization component as the polarization component guided in the direction toward the focus detection sensor 112 by the beam splitter, and the same polarization as the polarization component transmitted through the beam splitter. It is movable to a second position that absorbs the component. The first position and the second position can be rotated continuously or intermittently by driving means (not shown).

  The dimming means is rotatable relative to the beam splitter, which is a beam splitting means, around the optical axis.

  Further, the beam splitter which is the light reducing means and the light beam splitting means is integrally configured, and is movable between a position inserted in the optical path and a position retracted from the optical path. Then, using a drive source that inserts them into the optical path and retracts them out of the optical path, the dimming means and the beam splitter beam splitting means are rotated relative to each other to prevent the apparatus from becoming large. Can do.

  Further, according to the example provided with the second dimming means, it is possible to reduce the size of the apparatus including the beam splitter, and as a result, contribute to the downsizing of the entire apparatus.

  Further, by providing the quarter-wave plate 219 between the beam splitter and the imaging surface, it is possible to perform shooting without generating false colors even in a camera including an optical LPF using birefringence. Furthermore, by providing the quarter-wave plate 219 between the beam splitter and the photographing optical system, it is possible to perform appropriate distance measurement and photographing even for a subject that includes a large amount of specific polarized light.

According to the above embodiments,
(1) When the light beam from the photographing optical system is split by the beam splitter, the spectral characteristic of the split light beam is made substantially the same as that of the straight light, and the AF (and AE) function is operated. (3) Do not increase the size of the camera by the light splitting structure (4) Obtain a high-quality image based on the light traveling straight through the beam splitter (5) It is to improve the light use efficiency and simultaneously realize the separation of the AF light flux simultaneously with the light amount adjustment.

It is sectional drawing which shows the digital camera concerning Example 1 of this invention. It is a block diagram which shows the electric constitution of the digital camera of FIG. It is sectional drawing which shows the lens barrel of the digital camera of FIG. It is a schematic diagram which shows a functional unit in Example 1 of this invention. It is a flowchart which shows the imaging sequence of the digital camera of FIG. FIG. 6 shows desirable spectral characteristics of the light splitting function surface in Example 1 of the present invention. FIG. It is a figure which shows the desirable spectral characteristic of a light reduction means in Example 1 of this invention. It is a figure which shows the light beam in the functional unit in Example 1 of this invention. It is a figure which shows the relationship between the relative position of a light reduction means and a beam splitter, and light quantity in Example 1 of this invention. It is sectional drawing which shows the digital camera concerning Example 2 of this invention. It is sectional drawing which shows the state which the functional unit of the digital camera of FIG. 10 evacuated out of the optical path. It is a figure which shows the structural example of the functional unit of the digital camera of FIG. It is a figure which shows the light beam in the functional unit of the digital camera of FIG. It is a figure which shows the desired spectral characteristic of the light division functional surface in Example 2 of this invention. It is a figure explaining rotation operation of a functional unit in Example 2 of the present invention. It is sectional drawing which shows the digital camera concerning Example 3 of this invention. 16 is a cross-sectional view showing a state in which the functional unit of the digital camera is retracted out of the optical path. It is a figure which shows the structural example of the functional unit in Example 3 of this invention. It is a figure which shows the production method of the beam splitter in Example 3 of this invention. It is a schematic diagram which shows the light quantity adjustment apparatus using the conventional polarizing plate. It is function explanatory drawing of the light quantity adjustment apparatus using the conventional polarizing plate. It is explanatory drawing of the focus detection operation | movement by general pupil division. It is a figure which shows the signal example of the focus detection operation | movement by general pupil division. It is a schematic diagram which shows the focus detection apparatus using the conventional beam splitter. It is a schematic diagram which shows the brightness nonuniformity in the focus detection apparatus using the conventional beam splitter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Digital camera body 102 Shooting optical system 102a Focusing lens 103 Beam splitter 103a Light splitting functional surface 104 Optical axis 106 CMOS light receiving sensor 112 Focus detection sensor 113 Optical low-pass filter 116 Light attenuation means 116a Polarization azimuth angle 118 of light reduction means Functional unit 203a light splitting functional surface 216 first dimming means 218 functional unit 203 beam splitter 219 quarter wave plate 220a second dimming means 220b second dimming means 220c opening provided in the second dimming means 303 Beam splitter 303a Prism forming beam splitter 303b Prism forming beam splitter 316 First dimming means 318 Functional unit 330 Film-like second dimming means

Claims (4)

A light beam splitting unit that is disposed between the imaging optical system and the imaging surface and splits a light beam that passes through the imaging optical system and travels toward the imaging surface according to a deflection direction;
Focus detection means for outputting a focus state signal based on the light beam split by the light beam splitting means;
A dimming means disposed between the photographic optical thread and the imaging surface to remove a predetermined deflection component;
Have
The imaging apparatus according to claim 1, wherein the dimming means is rotatable relative to the light beam splitting means, and the amount of light on the imaging surface can be adjusted by the rotational position.   The dimming means has a first position that absorbs the same deflection component as the deflection component of the beam guided to the focus detection means by the beam splitting means, and the same deflection component of the beam that passes through the beam splitting means. The imaging apparatus according to claim 1, wherein the imaging apparatus is rotatable between a second position where the deflection component is absorbed.   The same polarization component of the light beam guided to the focus detection means by the light beam splitting means between one or both of the light beam splitting means and the photographing optical system and between the light flux splitting means and the dimming means. The imaging apparatus according to claim 1, further comprising a second dimming unit that absorbs a polarization component. The imaging apparatus according to claim 1, further comprising a quarter-wave plate between the dimming unit and the imaging surface.

Images