JP2007101965A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an imaging apparatus, equipped with a compact optical member for separating luminous flux and provided with a plurality of focus detection areas inside a photographic image plane. <P>SOLUTION: The imaging apparatus 101 has an imaging device 106 for photoelectrically converting a subject image; a focus detection means 112 detecting focus by using luminous flux from a subject; and the optical member 103, provided with a luminous flux separation surface 103a for separating the luminous flux from the subject to luminous flux directed toward the imaging device and luminous flux guided to the focus detection means. The optical member can be moved to a plurality of positions, where focus detection field of vision by the focus detection means is made to differ from each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus such as a digital still camera, and more particularly to an imaging apparatus that uses a light beam taken through a photographing optical system for focus detection.

  Conventionally, various devices have been proposed as an imaging device that performs focus detection using a part of a light beam taken through a photographing optical system.

  Patent Document 1 discloses a digital single-lens reflex camera that forms a primary object image formed by a photographing optical system on a two-dimensional light receiving sensor and photoelectrically converts the object image to obtain an image output related to the object. .

  Patent Document 2 discloses a camera equipped with a zoom lens in which a part of a light beam is separated in the middle of an optical path in the zoom lens, and focus detection is performed using the separated light beam.

In the cameras proposed in Patent Documents 1 and 2, the light beam from the photographing lens is separated into two by a separation surface (reflection / transmission surface) formed on a light beam separation member such as a beam splitter, and one light beam is used for photographing. The remaining light flux is guided to the light receiving sensor for focus detection.
JP-A-63-195630 (page 3, upper right column, line 20 to same page, lower left column, line 7, line 1, etc.) Japanese Patent Laying-Open No. 2003-140246 (paragraphs 0019 to 0023, FIG. 1, etc.)

  However, when the light beam separating member such as a beam splitter separates the light beam for photographing and the light beam for focus detection as described above, the amount of light incident on the image sensor decreases. Therefore, if the image is taken as it is, the photographed image becomes dark.

  As a countermeasure, a configuration in which the light beam separating member is arranged in the photographing optical path at the time of focus detection, while the light beam separating member is retracted outside the photographing optical path at the time of photographing so that all effective light beams from the photographing lens are incident on the imaging element. Conceivable.

  However, in this method, since the optical path length difference is optically generated between the focus detection when the light beam passes through the light beam separation member and the photographing without passing through the light beam separation member, it is necessary to correct the focus surface.

  Further, in the cameras disclosed in Patent Documents 1 and 2, the position of the light beam separating member in the photographing optical path is fixed to one. For this reason, when focus detection is to be selectively performed in a plurality of areas in the photographing screen, it is necessary to form a separation surface on the light beam separating member having a size that can cover the plurality of focus detection areas.

  However, due to this, the separation surface of the light beam separating member, and hence the light beam separating member, is increased in size particularly in the direction of the photographing optical axis. In order to move the light beam separating member within the camera, it is inevitable that the camera is increased in size. In addition, it is possible to make the light beam separating member smaller (thinner) by reducing the separation surface, but in this case, only focus detection in a fixed narrow region such as the central region in the photographing screen can be performed. Can not.

  Another object of the present invention is to provide an imaging technique that includes a small light beam separating member (optical member) and that can provide a plurality of focus detection areas in a photographing screen.

  In addition, the present invention eliminates the need for focus surface correction processing at the time of focus detection and at the time of shooting, while being provided with a movable light beam separating member (optical member), so that a shot image with good image quality can be acquired. One of the purposes is to provide such an imaging technique.

  An image pickup apparatus (first image pickup technique) as one aspect of the present invention picks up an image pickup element that performs photoelectric conversion of a subject image, focus detection means that performs focus detection using a light flux from the subject, and picks up a light flux from the subject. And an optical member provided with a light beam separation surface for separating the light beam toward the element and the light beam guided to the focus detection means. The optical member is characterized in that it can be moved to a plurality of positions that make the focus detection field of view by the focus detection means different from each other.

  An image pickup apparatus (second image pickup technology) as another aspect of the present invention includes an image pickup device that performs photoelectric conversion on a subject image, a light flux from the subject toward the image pickup device, and a light flux that is guided to a focus detection unit. And an optical member provided with a light beam separation surface for separating the light beam. The optical member is movable to a first position where the light beam separation surface is disposed in the optical path to the image sensor and a second position where the light beam separation surface is disposed outside the optical path. The optical member is characterized in that the entire light beam in the optical path is incident at each of the first and second positions.

  Furthermore, an imaging apparatus (third imaging technique) as another aspect of the present invention includes an imaging device that performs photoelectric conversion of a subject image, focus detection means that performs focus detection using a light beam from the subject, And an optical member provided with a light beam separation surface that separates the light beam into the light beam directed to the image sensor and the light beam guided to the focus detection unit. The optical member has a first position where the light beam separation surface is disposed in the optical path to the image sensor, and the light beam separation surface is disposed outside the light path, and the light beam from the subject is placed on a portion other than the light beam separation surface. It is possible to move to a second position that passes through the imaging element.

According to the first imaging technique, it is possible to select a plurality of positions of the light beam separation surface in the optical path to the image pickup device, so that a plurality of focus detections can be performed using a small light beam separation surface, that is, a small optical member. A region can be provided.
Further, according to the second and third imaging techniques, the entire light beam in the optical path is used as the optical member in both the state where the light beam separation surface is located in the optical path to the image sensor and the state where the light beam separation surface is located outside the optical path. Since the light is incident, there is almost no difference in optical path length between the light beams traveling toward the image sensor in both states. For this reason, it is not necessary to perform focus surface correction processing in both states, and an image with good image quality with little light loss can be acquired.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a configuration of a digital still camera (second imaging technique) as an imaging apparatus that is Embodiment 1 of the present invention. In FIG. 1A, a subject image acquired by an image sensor, which will be described later, is observed through the display 107 before shooting, or a shooting preparation operation including focus adjustment and photometry using a focus detection sensor described later is performed immediately before shooting. It shows the state when A display 107 provided on the back surface of the camera can display an image having an angle of view substantially the same as the shooting angle of view, and has a role of a so-called electronic viewfinder (EVF). FIG. 1B shows a state at the time of photographing. After shooting, the display 107 has a function of displaying the shot image for a predetermined time and confirming the shot image. This state is also obtained when performing focus adjustment by so-called TV-AF alone.

  The display 107 is composed of an organic EL spatial modulation element, a liquid crystal spatial modulation element, a spatial modulation element using electrophoresis of fine particles, and the like. These are low in power consumption and thin, and are effective for miniaturization of the camera.

  In FIG. 1, reference numeral 101 denotes a digital camera body, and reference numeral 102 denotes an imaging optical system (shooting optical system) for forming an object image. Reference numeral 104 denotes an optical axis of the imaging optical system 101, and 105 denotes a lens barrel that houses the imaging optical system 102.

  The imaging optical system 102 can adjust the imaging position in the direction of the optical axis 104 by an actuator (not shown) and a driving mechanism (not shown). The imaging optical system 102 can be configured by a single focus lens, a zoom lens, a shift lens, or the like.

  Reference numeral 103 denotes a beam splitter as an optical member having a light beam separation function surface 103a. Reference numeral 110 denotes an optical axis in the beam splitter 103. 111 is a release button, 108 is a recording medium for storing image data, and a semiconductor memory, an optical disk or the like is used.

  Reference numeral 109 denotes an eyepiece of an optical viewfinder, and reference numeral 106 denotes an imaging device which is a two-dimensional CCD sensor or a CMOS sensor. Reference numeral 112 denotes a focus detection sensor that is a light receiving element for distance measurement, and 113 denotes an optical low-pass filter.

  The state shown in FIG. 1A is hereinafter referred to as a first mode, and the position of the beam splitter 103 at this time is hereinafter referred to as a first mode position. In the first mode position, the light beam separation function surface 103 a of the beam splitter 103 is disposed in the optical path from the imaging optical system 102 toward the image sensor 106. Therefore, a part of the light beam in the optical path is separated into an AF light beam toward the focus detection sensor 112 and an image display light beam toward the image sensor 106 by the light beam separation function surface 103a. Further, the light beam that does not pass through the light beam separation function surface 103 a passes through the beam splitter 103 and travels toward the image sensor 106. Details of the beam splitter 103 and the light beam separation function surface 103a will be described later.

  On the other hand, the state shown in FIG. 1B is hereinafter referred to as a second mode, and the position of the beam splitter 103 at this time is hereinafter referred to as a second mode position. In the second mode position, the light beam separation function surface 103 a of the beam splitter 103 is disposed outside the optical path from the imaging optical system 102 toward the image sensor 106. For this reason, of the light beams from the imaging optical system 102, a light beam effective for photographing toward the image sensor 106 passes through the beam splitter 303 and reaches the image sensor 106 without passing through the light beam separation function surface 103a.

  The charge accumulated by photoelectric conversion in the image sensor 106 is thinned out and read at a certain rate when a display image on the display 107 is generated. At the time of shooting, the accumulated charges from all the pixels are read out and used to generate a high-definition image.

  FIG. 2 shows an electrical configuration of the digital camera of this embodiment. First, a description will be given of the part relating to the photographing and recording of object images.

  The camera has an imaging system, an image processing system, a recording / reproducing system, and a control system. The imaging system includes an imaging optical system 102 and an imaging element 106. 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 an image sensor driving circuit 137.

  A standardized connection terminal 138 is connected to an external device such as a personal computer to transmit and receive data. These electric circuits are driven by electric power from a power source such as a secondary battery or a fuel cell (not shown).

  The imaging system is an optical processing system that forms an image of a light beam from an object on the light receiving surface of the imaging element 106 via the imaging optical system 102. This imaging system adjusts a diaphragm and a mechanical shutter (not shown) of the imaging optical system 102 to expose the imaging element 106 with an object light beam having an appropriate amount of light.

  The image sensor 106 has, for example, a total of about 8 million pixels in which 3264 square pixels are arranged in the long side direction and 2448 in the short side direction. Each pixel is provided with a color filter of any one of R (red), G (green), and B (blue) to form a so-called Bayer array in which four pixels are combined.

  In the Bayer array, the overall image performance is improved by arranging more G pixels that are easily felt when an observer views the image than the R and B pixels.

  In general, in image processing using this type of image sensor, a large portion of a luminance signal is generated from G, and a color signal is generated from R, G, and B.

  The image signal read from the image sensor 106 is supplied to the image processing system via the A / D converter 130.

  The A / D converter 130 converts the signal (accumulated charge) read from each pixel into, for example, a 12-bit digital signal corresponding to the amplitude and outputs the digital signal. The subsequent signal processing is executed by digital processing.

  The image processing system obtains an image signal of a desired format from R, G, B digital signals. This image processing system converts R, G, and B color signals into a luminance signal Y and YC signals represented by color difference signals (RY) and (BY).

  The RGB image processing circuit 131 processes a signal for 3264 × 2448 pixels received from the image sensor 106 via the A / D converter 130. The RGB image processing circuit 131 includes a white balance circuit and a gamma correction circuit, and further includes an interpolation calculation circuit that performs high resolution by interpolation calculation.

  The YC processing circuit 132 generates a luminance signal Y and color difference signals (R−Y) and (B−Y). The YC processing circuit 132 includes a low-frequency luminance signal generation circuit that generates a low-frequency luminance signal YL, a high-frequency luminance signal generation circuit that generates a high-frequency luminance signal YH, and color difference signals (RY) and (BY). It consists of a color difference signal generation circuit to be generated. The luminance signal Y is formed by combining the low-frequency luminance signal YL and the high-frequency luminance signal YH.

  The recording / reproducing system outputs the image signal to the above-described recording medium and outputs the image signal to the display 107. The recording processing circuit 133 performs image signal writing processing and reading processing on the recording medium. The reproduction processing circuit 134 reproduces the image signal read from the recording medium and outputs it to the display 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 reading the compressed data. The compression / decompression circuit includes a frame memory for signal processing and the like, and accumulates YC signals from the image processing system for each image in the frame memory. Then, the YC signal is read and compressed and encoded for each of a plurality of blocks. The compression coding is performed by, for example, performing two-dimensional orthogonal transformation, normalization, and Huffman coding on the image signal for each block.

  The reproduction processing circuit 134 is a circuit that performs matrix conversion of the luminance signal Y and the color difference signals (R−Y) and (B−Y), for example, into RGB signals. The signal converted by the reproduction processing circuit 134 is output to the display 107. Thereby, the visible image is displayed and reproduced.

  The control system includes an operation detection circuit 136 that detects operations of various operation members such as the release button 111. In addition, a camera system control circuit 135 that controls each unit in accordance with the detection signal and generates and outputs a timing signal at the time of shooting is included. Furthermore, an image sensor drive circuit 137 that generates a drive signal for driving the image sensor 106 under the control of the camera system control circuit 135, an information display device in the optical viewfinder, and an information display device provided on the outer surface of the camera Includes an information display circuit 142 for controlling.

  The control system controls the imaging system, the image processing system, and the recording / reproducing system according to the operation of the operation member. For example, the operation of the release button 111 is detected to control the driving of the image 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 control system controls the state of each segment provided in the information display device in the optical viewfinder by the information display circuit 142.

  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.

  In the first mode, the AF control circuit 140 obtains a signal output from the focus detection sensor 112 provided corresponding to a predetermined position on the shooting screen and generates a focus detection signal. The focus detection signal is a signal indicating a phase difference between a plurality of images formed by a light beam from the imaging optical system 102, and the phase difference indicates an imaging state of the imaging optical system 102. When the phase difference is a predetermined value, the imaging optical system 102 is in a focused state, and when the phase difference is other than the predetermined value, the imaging optical system 102 is in a defocused state.

  When the defocus is detected, the AF control circuit 140 converts this into a driving amount of a focusing lens (see FIGS. 3 and 4) included in the imaging optical system 102. Then, the drive amount information is transmitted to the lens system control circuit 141 via the camera system control circuit 135. This AF is hereinafter referred to as phase difference AF.

  In the present embodiment, a TV-AF that evaluates the contrast on the image sensor 106 and detects the imaging state of the imaging optical system 102 can be used following or independently of the phase difference AF. When performing the TV-AF following the phase difference AF, a display image signal obtained by thinning out reading from the image sensor 106 is used while the beam splitter 103 is disposed at the first mode position. Specifically, the contrast evaluation value of the image on the image sensor 106 is generated while driving the focusing lens, and the position with the highest contrast is determined as the in-focus position. In this embodiment, after the focusing lens is driven to a predetermined focusing range by phase difference AF, high-precision focusing is performed by TV-AF.

  In this way, by using phase difference AF and TV-AF together, the direction in which the focusing lens in TV-AF should be driven can be determined in advance from the result of phase difference AF, so that the speed of AF operation as a whole is increased. And high accuracy.

  Note that the detection accuracy by phase difference AF is lowered for a subject with low contrast, but even in such a case, there is a case where reliable focus adjustment can be performed by using TV-AF. In such a case, the photographer can select the TV-AF mode from the beginning. In this case, the beam splitter 103 is moved to the second mode position to perform TV-AF.

  When the lens system control circuit 141 receives the information on the driving amount of the focusing lens from the AF control circuit 140, the lens system control circuit 141 moves the focusing lens in the imaging optical system 102 in the direction of the optical axis 104 by an unillustrated driving mechanism, Adjust the focus.

  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, when the release button 111 is operated up to the second stage, the beam splitter 103 is driven by a driving mechanism described later, and the transmission unit 103-2 of the beam splitter 103 covers the entire surface of the image sensor 106 from the first mode. Switch to the second mode. Thereby, the subject image is formed by the light flux that has passed through the optical low-pass filter 113. Then, photographing control is performed by the above-described imaging system, image processing system, and recording / reproducing system.

  As shown in FIGS. 3 and 4, in the beam splitter 103 arranged at any mode position, the light flux in the optical path from the imaging optical system 102 toward the image sensor 106 (light flux effective for image display and photographing) is as follows. All enter the beam splitter 103. Specifically, at the first mode position, all the light beams in the upper and lower regions (first prism 103-1 and second prism 103-2 described later) of the beam splitter 103 with the light beam separation function surface 103a interposed therebetween. Is incident. Further, at the second mode position, all the light beams are incident on a region (second prism 103-2) below the light beam separation function surface 103a.

  For this reason, the spatial optical path length from the imaging optical system 102 to the image sensor 106 (also referred to as air-converted optical path length; hereinafter simply referred to as optical path length) does not vary between the first mode and the second mode. Therefore, it is not necessary to correct the focus position depending on the mode.

  Further, even during the switching between the first mode and the second mode, all the light beams in the optical path are incident on the beam splitter 103 and the optical path length does not vary. It becomes possible. For this reason, the photographer can confirm the photographed image without dropping frames until immediately before the photographing is started. Therefore, a short release time lag can be realized without impairing the high-speed focus detection operation.

  FIG. 3 shows the configuration of the lens barrel 105 in the first mode in the digital camera 101 of this embodiment. FIG. 4 shows the configuration of the lens barrel 105 in the second mode. Further, FIG. 5 shows a detailed configuration of the beam splitter 103. Hereinafter, the beam splitter 103 and its peripheral part will be described in detail with reference to these drawings.

  The beam splitter 103 is disposed between the rear end of the lens elements constituting the imaging optical system 102 and the image sensor 106. The lens 102 a is a focusing lens, and performs focus adjustment by moving in the direction of the optical axis 104.

The image sensor 106 is positioned with respect to a fixed ground plate (not shown) of the lens barrel 105. The beam splitter 103 is held by a holding member (see FIG. 22).
The still image shooting sequence in the camera of the present embodiment is generally performed in the following procedure under the control of the camera system control circuit 135 according to the computer program.

Step 1.
When the TV-AF mode is selected, the beam splitter 103 is set to the second mode position (FIG. 4), and the above-described TV-AF operation is performed. If the normal AF mode in which phase difference AF is performed is selected, the process proceeds to step 3.

Step 2.
When the first operation of the release button 111 is detected, the image sensor 106 is driven, and an image of the object image formed by the light beam transmitted through the transmission unit 103-2 of the beam splitter 103 is repeatedly generated at a predetermined period. In 107, the object image is displayed in real time.

Step 3.
The focus detection for phase difference AF by the focus detection sensor 112 is performed by the one light beam separated by the beam splitter 103.

Step 4.
When a defocus of a predetermined amount or more is detected by the focus detection sensor 112, the driving amount of the focusing lens 102a is calculated, and the focusing lens 102a is moved by that amount to adjust the focus.

Step 5.
After the focus adjustment is completed, the focus detection sensor 112 is performed again, and when it is confirmed that the defocus amount is within a predetermined focus range including the focus position, the process proceeds to step 6.

Step 6.
TV-AF is performed, and the focusing lens 102a is moved to a more accurate in-focus position.

Step 7.
When the second stage operation of the release button 111 is detected, the beam splitter 103 is switched from the first mode position to the second mode position by a drive mechanism described later (FIG. 4).

Step 8.
The image sensor 106 is driven to capture a high-definition still image.

Step 9.
After the photographing is completed, the beam splitter 103 is returned from the second mode position to the first mode position (FIG. 3).

Step 10.
Write the captured image data to the recording media. And it returns to step 1.

  Next, the light beam separation function of the beam splitter 103 will be described. As shown in FIG. 5A, the beam splitter 103 is formed by bonding a first prism 103-1 and a second prism 103-2 made of a transparent body with surfaces 103-1a and 103-2a. Produced. The incident surface 103b of the beam splitter 103 shown in FIG. 5B is composed of a surface 103-1b of the first prism 103-1, and a surface 103-2b of the second prism 103-2.

  Further, the exit surface 103d of the straight light from the incident surface 103b is composed of a surface 103-1d of the first prism 103-1, and a surface 103-2d of the second prism 103-2.

  Each of the prisms 103-1 and 103-2 is made of a ring-opening metathesis polymer polymer (HROP; refractive index 1.53) made of a plastic material having a small birefringence. Further, the surfaces 103-1b and 103-1d of the first prism 103-1, and the surfaces 103-2b and 103-2d of the second prism 103-2 are parallel to each other and spaced apart from each other.

  Further, two angles formed by the surface 103-1a of the first prism 103-1 with respect to the surface 103-1b and the surface 103-1d are such that the surface 103-2a of the second prism 103-2 is the surface 103-1d. And two angles formed with respect to the surface 103-1b. Therefore, when the first prism 103-1 and the second prism 103-2 are joined by the surfaces 103-1 a and 103-2 a (the surface after joining is denoted by 103 a), the joined beam splitter 103 is Optically, it exhibits the same characteristics as a parallel plate. Therefore, no matter which region of the incident surface 103b the light beam enters, it passes through the same wavefront, so that no change in aberration occurs regardless of the incident position.

  A dielectric multilayer film is formed on the surface 103-2a of the second prism 103-2 so that the surface 103a of the beam splitter 103 has a light beam separating function. Then, the second prism 103-2 is bonded to the first prism 103-1, using an optical adhesive having index matching.

  Since the dielectric multilayer film can reduce the light absorption to a level that can be almost ignored, the incident light is divided in either direction of the image sensor 106 and the focus detection sensor 112 on the light beam separation function surface 103a. That is, the light beam separation functional surface 103-a reflects a part of incident light in a predetermined wavelength region and transmits the other part.

  The optical characteristics of the light beam separation function surface 103-a thus formed are shown in FIG. The spectral transmittance characteristics from a wavelength of 400 nm to 1000 nm are valley-shaped having a minimum value near 500 nm. On the other hand, the spectral reflectance characteristic is a mountain shape having a maximum value in the vicinity of 500 nm. Here, in the visible region from 450 nm to 650 nm, the spectral transmittance characteristic is constant at approximately 45%. In a camera that shoots a color image, the sensitivity range of the image sensor 106 is matched with the visibility range. Therefore, it can be said that the light beam separation function surface 103-a has a flat spectral reflectance characteristic in the sensitivity wavelength range of the image sensor 106. .

Further, an antireflection coating AR is formed on the entrance surface 103b of the beam splitter 103 and the AF exit surface 103c formed on the upper end of the second prism 103-2. The antireflection coating is formed by laminating a thin film having a different refractive index on the lens base material with SiO ₂ , TiO ₂ , ZnO ₂ or the like at a quarter wavelength thickness (for example, 0.1 to 0.3 μm), thereby reflecting the surface. The rate can be kept low. The characteristics of the antireflection coating are shown in FIG.

  Further, an infrared (IR) cut filter film 103e is formed on the exit surface 103d of the beam splitter 103. With this filter film 103e, only the visible region wavelength can be guided to the image sensor 106, and a camera with good color reproducibility can be constructed.

  On the other hand, the light beam reflected by the light beam separation function surface 103a among the light beams incident on the inside from the incident surface 103b of the beam splitter 103 is internally reflected (total internal reflection) on the incident surface 103b of the beam splitter 103, and is reflected from the AF exit surface 103c. The light is emitted and guided to the focus detection sensor 112.

  In this way, by guiding the light beam reflected by the light beam separation function surface 103a to the focus detection sensor 112 using internal reflection, the light beam separation function surface 103a is caused to emit light from the imaging optical system 102 to the image sensor 106. Can stand more than 45 ° with respect to the axis. Therefore, the thickness of the beam splitter 103 in the optical axis direction can be reduced as compared with the case where the light beam separation function surface is disposed at an angle of 45 ° with respect to the optical axis. For this reason, the beam splitter 103 and the driving mechanism described later can be accommodated even in a narrow space from the rear end of the imaging optical system 102 to the image sensor 106.

  Since the light beam reaching the focus detection sensor 112 does not pass through the IR cut filter film 103e, it includes infrared light. For this reason, the luminous flux has higher luminance than the light transmitted through the IR cut filter film, and the AF performance in a dark scene can be improved.

  Since the spectral reflectance characteristic of the visible region wavelength at the light beam separation function surface 103a is about 55% and about 30% at the infrared region wavelength, high-precision focus detection is possible with a sufficient amount of light.

  Next, the focus detection sensor 112 will be described. FIG. 8 shows a focus detection field of the focus detection sensor 112.

  In FIG. 8, reference numeral 120 denotes a finder field as an imaging range (observation range), and 121-1 to 121-9 denote focus detection fields.

  If the focus detection field is basically set near the center of the finder field 120, it is easy to use.

  Since the focus detection visual field formed by the pixel columns extending in the vertical direction is sensitive to the luminance distribution in the vertical direction, for example, focus detection can be performed on horizontal lines. On the other hand, since the focus detection visual field formed by the pixel rows extending in the horizontal direction is sensitive to the luminance distribution in the horizontal direction, for example, focus detection for vertical lines is possible.

  The actual focus detection sensor 112 is configured as shown in FIG. FIG. 9 is a view of the focus detection sensor 112 when viewed from the optical axis direction of the sensor. Reference numerals 112-1 to 112-9 denote pixel columns constituting the focus detection visual fields 121-1 to 121-9.

  FIG. 10 is a cross-sectional view of the pixel portion of the focus detection field of view (for example, 112-1) of the focus detection sensor 112. 11A is a plan view showing a photoelectric conversion unit of one pixel of the focus detection sensor 112, and FIG. 11B is a plan view of one pixel of the focus detection sensor 112.

  In FIG. 10, light enters the focus detection sensor 112 from above, and in FIGS. 11A and 11B, the light enters the focus detection sensor 112 from above perpendicular to the paper surface. The focus detection sensor 112 is a CMOS type sensor having an on-chip type microlens, and the F number of the focus detection light beam can be defined by the action of the microlens.

  In FIG. 10, reference numeral 151 denotes a silicon substrate, and 152A and 152B denote photoelectric conversion portions of embedded photodiodes. Reference numeral 154 denotes a light-shielding first wiring layer made of aluminum or copper. Reference numeral 155 denotes a second wiring layer using aluminum or copper. Reference numeral 156 denotes an interlayer insulating film and a passivation film made of silicon oxide film, hydrophobic porous silica, silicon oxynitride film, or silicon nitride film. Reference numeral 158 denotes a microlens, and 157 denotes a flattening layer for setting the distance from the second wiring layer 155 to the microlens 158 with high accuracy. The first wiring layer 154 and the second wiring layer 155 are metal films having openings provided discretely and do not transmit visible light except for the openings.

  The first wiring layer 154 and the second wiring layer 155 have both an electrical function for operating the focus detection sensor 112 and an optical function for controlling the angle characteristics of the received light flux.

  The flattening layer 157 is formed by a method of curing a thermosetting resin or an ultraviolet curable resin after spin coating or adhering a resin film.

  As shown in FIG. 11A, the photoelectric conversion units 152A and 152B are formed in a zigzag shape, and circuit portions 159A and 159B are connected to both ends thereof. In the circuit portions 159A and 159B, a transfer MOS transistor serving as a transfer switch and a reset MOS transistor for supplying a reset potential are provided. A source follower amplifier MOS transistor, a selection MOS transistor for selectively outputting a signal from the source follower amplifier MOS transistor, and the like are also provided.

  On the photoelectric conversion unit 152, as shown in FIG. 11B, five microlenses 158 are provided in a zigzag manner for one pixel.

Here, the microlens 158 is formed of resin, SiO ₂ , TiO ₂ , Si ₃ N ₄ or the like. Since the microlens 158 is used not only for condensing but also for imaging, the microlens 158 is configured by an axially symmetric spherical lens or an axially symmetric aspherical lens.

  Since the microlens 158 has a shape having the symmetry axis 160, the microlens 158 is circular when viewed in a plan view. However, by providing a plurality of microlenses 158 in one pixel, the pixel pitch can be reduced while reducing the pixel pitch. The light receiving area can be increased. Therefore, a sufficient focus detection output can be obtained even for a low-luminance object. Further, a shape that does not have an axis of symmetry such as a semi-cylindrical type is not suitable for the focus detection sensor 112 because there is no imaging effect as a lens.

  In addition, in order to suppress the surface reflection of light at the microlens 158, a thin film having a low refractive index or a fine structure (so-called sub-wavelength structure) below the wavelength of visible light is formed on the surface of the microlens 158. Also good.

  The light beam emitted from the beam splitter 103 enters the microlens 158 of the focus detection sensor 112. Among these components, the component passing through the opening 155A provided in the second wiring layer 155 and the opening 154A provided in the first wiring layer 154 enters the photoelectric conversion unit 152A. In addition, a component passing through the opening 155A provided in the second wiring layer 155 and the opening 154B provided in the first wiring layer 154 enters the photoelectric conversion unit 152B. The light beams incident on the photoelectric conversion units 152A and 152B are converted into electric signals.

  Since the light shielding layer for forming the opening is also used as the first wiring layer 154 and the second wiring layer 155, there is no need to provide a light shielding layer for the opening, and the configuration of the focus detection sensor 112 is simplified. Can do.

  FIGS. 12 and 13 are a plan view and a perspective view, respectively, showing a state in which the pixels shown in FIG. 11 are connected to form a pixel row for use in focus detection.

  In FIG. 12, illustration of the microlenses 158 at both ends is omitted so that the photoelectric conversion units 152A and 152B can be seen so that the positional relationship between the photoelectric conversion units 152A and 152B and the microlens 158 can be understood.

  In FIG. 13, the photoelectric conversion units 152A and 152B, the first wiring layer 154, the second wiring layer 155, and the microlens 158 are extracted from the constituent elements and are shown in the vertical direction. Further, in order to make the boundary of one pixel easy to understand, the zigzag shape of the photoelectric conversion unit is projected on the first wiring layer 154 and the second wiring layer 155 and indicated by a broken line.

  In FIG. 12, five microlenses 158a with hatching constitute one pixel. A large number of such pixels are arranged in the horizontal direction to form the pixel columns 112-1 to 112-9 shown in FIG.

  Since the microlenses 158 arranged in a zigzag form a space between the adjacent microlenses 158, the microlenses 158 are densely arranged on the pixel array. Therefore, the amount of light that is not used without entering the microlens 158 is small enough to be ignored.

  In addition, since the microlenses 158 are arranged in a zigzag manner, the frequency response of pixels near the Nyquist frequency can be lowered. As a result, even if an object image including a spatial frequency component higher than the Nyquist frequency is projected, aliasing distortion hardly occurs, and phase difference detection between output signal waveforms of the focus detection sensor 112 described later can be performed with high accuracy.

  Further, a micro lens 158b that is not disposed on the photoelectric conversion units 152A and 152B and does not contribute to photoelectric conversion is formed around the pixel column. This is because the microlens 158 can be manufactured with high accuracy by arranging the microlenses 158 as uniformly as possible.

  The first wiring layer 154 shown in FIG. 13 has a large number of rhombus-like openings 154A and 154B. As shown in FIG. 14 which is a plan view, the openings 154A and 154B are provided in pairs corresponding to each of the microlenses 158, and are formed in the vicinity of the focal position of the microlens 158.

  With such a configuration, the openings 154A and 154B are back-projected onto the exit pupil of the imaging optical system 102 by the microlens 158. For this reason, it is possible to determine the light receiving angle characteristic of the light beam taken in by the pixel depending on the shapes of the openings 154A and 154B.

  The opening 155A provided in the second wiring layer 155 is a stop for preventing light from entering the openings other than the openings 154A and 154B of the first wiring layer. As a result, only the light beams incident on the openings 154A and 154B enter the photoelectric conversion units 152A and 152B, respectively.

  Here, in order not to cause nonuniformity in the output signal output from each pixel row of the focus detection sensor 112, the shapes of the openings 154A and 154B are constant for the pixel row forming one focus detection field.

  15 and 16 are partial cross-sectional views of the focus detection visual field 112-1 shown in FIG. Each microlens 158 back-projects the openings 154A and 154B of the first wiring layer 154 onto the exit pupil of the imaging optical system 102. Accordingly, as shown in FIG. 15, the passage of the light beam 132A through the opening 154A is equivalent to the emission of the light beam 132A from the back-projected image of the opening 154A of the first wiring layer 154.

  Similarly, as shown in FIG. 16, the fact that the light beam 132B can pass through the opening 154B is equivalent to the light beam 132B being emitted from the back projection image of the opening 154B of the first wiring layer 154.

  Therefore, light rays incident on the focus detection sensor 112 from other than the back-projected images of the openings 154A and 154B are always blocked by the first wiring layer 154 or the second wiring layer 155 and cannot reach the photoelectric conversion units 152A and 152B. There is no conversion.

  An output signal waveform obtained by arranging the output signals from the photoelectric conversion unit 152A and an output signal waveform obtained by arranging the output signals from the photoelectric conversion unit 152B for a pixel row constituting one focus detection field of view. There is the following relationship between them. That is, a relatively laterally shifted state is observed between them depending on the imaging state of the object image formed by the imaging optical system 102 on the focus detection field.

  This is because the region through which the light beam passes on the exit pupil of the imaging optical system 102 arranges the output signal waveform obtained by arranging the output signals from the photoelectric conversion unit 152A and the output signal from the photoelectric conversion unit 152B. This is because the output signal waveform obtained in this way is different.

  The shift direction of the output signal waveform is reversed between the front pin and the rear pin, and the principle of focus detection is to detect this phase difference (shift amount) including the direction using a technique such as correlation calculation.

  17 and 18 show output signal waveforms of the focus detection sensor 112 input to the AF control circuit 140. FIG. The horizontal axis represents the pixel arrangement, and the vertical axis represents the output value. FIG. 17 shows an output signal waveform when the object image is not in focus, and FIG. 18 shows an output signal waveform when the object image is in focus.

  In this way, focus detection can be performed by first determining the identity of a set of signals. Furthermore, the defocus amount can be obtained by detecting the phase difference using a known method using correlation calculation, for example, a method disclosed in Japanese Patent Publication No. 5-88445.

  If the obtained defocus amount is converted into an amount to drive the focusing lens 102a of the imaging optical system 102, automatic focus adjustment is possible. Since the amount by which the focusing lens 102a is to be driven is known in advance, the lens is normally driven only once up to the in-focus position, and extremely fast focus adjustment can be performed.

  Here, the focus detection light beam will be described. In the focus detection sensor 112, the F-number (Fno) of the focus detection light beam is different for each focus detection field by controlling the light receiving angle characteristic for each focus detection field. The size of the region through which the light beam passes on the exit pupil of the imaging optical system 102 is large in the central focus detection field 112-1 and small in the peripheral focus detection field (for example, 112-4).

  FIG. 19 shows the luminance of an object imaged by the image sensor 106. FIG. 19A shows an image at Fno 2.8, FIG. 19B shows an image at Fno 4, and FIG. 19C shows an image at Fno 8. The shaded portion in the image is an image portion formed by the light beam transmitted through the light beam separation function surface 103a.

  As shown in FIG. 19, the spread of luminance unevenness at the edge portion of the light beam separation function surface 103a differs depending on Fno. However, the spectral characteristics are substantially the same regardless of the image height and Fno. Therefore, at the time of playback processing on the display 107, appropriate brightness correction parameters corresponding to Fno are stored in advance, and the playback processing is controlled by the camera system control circuit 135 shown in FIG. 2 based on the Fno information. To do. As a result, it is possible to display a reproduced image without a sense of incongruity. The luminance correction parameter is information corresponding to the light amount difference (luminance difference) between the light beam that has passed through the light beam separation function surface and the light beam that has not passed.

  The state of uneven brightness as shown in FIG. 19 shows different characteristics depending on the manufacturing method of the beam splitter 103 and the film characteristics of each optical surface. However, by measuring and storing the luminance unevenness information for each Fno as initial data in advance during the manufacturing process or the like, individual differences in the luminance unevenness correction parameters can be absorbed.

  FIG. 20 shows a drive mechanism of the beam splitter 103. In this figure, the holding structure of the beam splitter 103 as seen from the imaging optical system 102 side is shown. FIG. 20A shows the state of the beam splitter 103 at the first mode position, and FIG. 20B shows the state of the beam splitter 103 at the second mode position. Further, the image pickup element 106 is shown through the beam splitter 103 and its position is indicated by a chain line.

  The beam splitter 103 and the focus detection sensor 112 are fixed in advance with an adhesive, and both of them are held by the splitter frame 201. 202 is a guide rod for guiding the splitter frame 201 in the vertical direction, 203 is a microstepping motor shown in FIG. 1, and 204 is a lead screw that is rotationally driven by the microstepping motor 203.

  When the beam splitter 103 is moved to a predetermined position, a predetermined number of pulse signals are input to the microstepping motor 203. As a result, the lead screw 204 rotates, and the splitter frame 201 moves in the vertical direction along the guide rod 202 due to the engagement between the screw portion formed on the splitter frame 201 and the lead screw 204. For this reason, the vertical position of the beam splitter 103 can be changed while suppressing the surface shake. Further, the holding at a predetermined position may be a method in which an electric current is passed through the microstepping motor 203, but a method in which the electric current is not supplied by setting the cogging torque and the friction with the lead screw 204 appropriately is adopted. You can also.

  FIG. 21 is a flowchart for explaining the control of the drive mechanism of FIG. 20 along the imaging sequence of the camera. This flow starts when the camera is turned on and ends when the power is turned off. This control is executed by the camera system control circuit 135, the lens system control circuit 141, the AF control circuit 140, and the like according to a computer program.

  It should be noted that here, operations of components not directly related to the present invention and detailed operations at each step (for example, confirmation after operation and standby operation by a timer) are omitted.

  In step (abbreviated as S in the figure) 1001, the photographer selects either the normal AF mode or the TV-AF mode. When the normal AF mode is selected, the process proceeds to step 1002, and the beam splitter 103 is moved to the first mode position shown in FIG. 20A in order to perform focus detection by the focus detection sensor 112. If the TV-AF mode is selected, the process proceeds to step 1011 and the beam splitter 103 is moved to the second mode position shown in FIG.

  In the normal AF mode, in step 1003, the image sensor 106 is driven to photoelectrically convert the subject image. Then, the RGB processing circuit 131 and the YC processing circuit 132 perform various processes and output image data to the display 107. Thereby, the photographer can check the subject image through the display 107.

  In addition, in the series of processes, the aperture in the lens barrel 105 is adjusted according to the brightness of the subject, or the gain of the signal of the image sensor 106 is adjusted to obtain an appropriate brightness for the display 107. The subject image is displayed.

  In step 1004, it is determined whether or not the first-stage operation SW1 of the release button 111 has been performed. If not, the process returns to step 1003. If the first stage operation SW1 has been performed, the process proceeds to step 1005.

  In step 1005, the focus detection sensor 112 performs photoelectric conversion on the subject image formed by the light beam incident through the beam splitter 103. Based on the output from the focus detection sensor 112, the defocus amount and the drive amount and drive direction of the focusing lens 102a corresponding to the defocus amount are calculated by the method described above. That is, the phase difference AF is performed in this step and the next step 1006.

  Next, in step 1006, the focusing lens 102a is driven in the calculated driving direction by the driving amount calculated in step 1005. Thereby, the imaging optical system 102 is substantially focused on the subject.

  In step 1007-1, the subject image formed by the light beam incident through the beam splitter 103 is photoelectrically converted by the focus detection sensor 112 again. Then, based on the output from the focus detection sensor 112, it is confirmed whether or not focus is achieved. If the subject is in focus, a sound or light is emitted to notify the photographer of the in-focus state, and the process proceeds to step 1007-2.

  Although not shown in this flow, if it is determined that the subject is out of focus, the focusing lens 102a is driven again based on the defocus detection result. In step 1007-1, the focus is confirmed again. If in-focus confirmation cannot be performed even after repeating this operation a plurality of times, it is displayed that the in-focus state is impossible, and the mode is switched to TV-AF.

  In step 1007-2, the focusing lens 102a is driven and in-focus confirmed by TV-AF.

  In step 1008, it is determined whether or not the second-stage operation SW2 of the release button 111 has been performed. If not, the process returns to step 1004. If the second-stage operation SW2 has been performed, the process proceeds to step 1009.

  In step 1009, the beam splitter 103 is moved to the second mode position shown in FIG. Immediately thereafter, in step 1010, the image sensor 106 is exposed (photographed).

  In the flow of FIG. 21, the flow does not proceed to step 1008 unless the operation from step 1005 to step 1007-2 is completed. However, the flow is not limited to this, and the flow proceeds to step 1008 even when the focusing operation is not completed. It may be configured to be able to. That is, even when the focus is not in focus, the second step SW2 of the release button 111 may be used for exposure.

  Here, the exposure in step 1010 resets the electric charge accumulated in the image sensor 106, and after the accumulation time corresponding to the brightness of the subject has elapsed, the light receiving surface of the image sensor 106 is shielded by the shutter, and the accumulated charge is accumulated. Is an operation of reading out. In step 1010, the captured image data is recorded on the recording medium 108.

  After the exposure is completed, although not shown in this flow, if the first and second stage operations SW1 and SW2 of the release button 111 are continued, the captured image is displayed by staying at step 1010. The display continues to 107. When the operation of the release button 111 is released, the shutter is opened again and the process returns to step 1001.

  Next, a case where the photographer selects the TV-AF mode in step 1001 will be described.

  In Step 1011, the beam splitter 103 is moved to the second mode position shown in FIG.

  In step 1012, as in step 1003, the image sensor 106 is driven to photoelectrically convert the subject image. Then, the RGB processing circuit 131 and the YC processing circuit 132 perform various processes and output image data to the display 107.

  In step 1013. It is determined whether or not the first-stage operation SW1 of the release button 111 has been performed. If not, the process returns to step 1012. If the first stage operation SW1 has been performed, the process proceeds to step 1014.

  In step 1014, the focusing lens 102a is step-driven by a predetermined driving amount to calculate a contrast evaluation value, and based on the result, the focusing lens 102a reaches the in-focus position.

  In this flow, TV-AF is not performed unless the first-stage operation SW1 of the release button 111 is performed. However, even if the first-stage operation SW1 is not performed, TV-AF is performed at any time. The occurrence of a so-called blurred state may be avoided. As a result, the subsequent TV-AF can be speeded up.

  In step 1015, it is confirmed that the contrast evaluation value is at a peak (in-focus position), and the photographer is notified of the focus by sound or light.

  In step 1016, it is determined whether or not the second-stage operation SW2 of the release button 111 has been performed. If not, the process returns to step 1013. When the second-stage operation SW2 is performed, the process proceeds to step 1010, and the image sensor 106 is exposed.

  As described above, according to this embodiment, even if the beam splitter 103 is moved to the first mode position and the second mode position, the optical path from the imaging optical system 102 to the image sensor 106 before and after the movement. There is virtually no change in length. Therefore, even when switching between the first mode position and the second mode position, it is not necessary to perform the focus surface correction process. Further, the subject image can be displayed on the display 107 even during the switching from the first mode position to the second mode position, that is, immediately before reaching the second mode position.

  Furthermore, since the distance between the first mode position and the second mode position of the beam splitter 103 is short and parallel movement in one axial direction, it is possible to select an actuator with a small driving force. It becomes. For this reason, a small actuator such as a microstepping motor and a simple drive mechanism can be employed, and an increase in the size of the camera can be suppressed.

  Further, since the light beam reaching the image sensor 106 at the time of photographing does not pass through the light beam separation function surface 103a, it is not affected by the light amount reduction on the light beam separation function surface 103a. Therefore, it is possible to acquire a captured image with good image quality with little light loss.

  FIG. 22 shows the configuration of a lens barrel of a digital still camera (second imaging technique) that is Embodiment 2 of the present invention. In the present embodiment, components common to the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  FIG. 22A shows a configuration in the first mode in which focus detection is performed by the focus detection sensor 112. At the first mode position, the light beam separation function surface 303 a of the beam splitter 303 is disposed in the optical path from the imaging optical system 102 toward the image sensor 106. Therefore, a part of the light beam in the optical path is separated into an AF light beam toward the focus detection sensor 112 and an image display light beam toward the image sensor 106 by the light beam separation function surface 303a. Further, the light beam that does not pass through the light beam separation function surface 303 a passes through the beam splitter 303 and travels toward the image sensor 106.

  On the other hand, FIG. 22B shows a configuration in the second mode in which shooting and independent TV-AF are performed. In the second mode position, the light beam separation function surface 303 a of the beam splitter 303 is disposed outside the optical path from the imaging optical system 102 toward the image sensor 106. For this reason, of the light beams from the imaging optical system 102, a light beam effective for photographing toward the image sensor 106 passes through the beam splitter 303 without reaching the light beam separation function surface 303 a and reaches the image sensor 106.

  In the first embodiment, the case where the beam splitter and the focus detection sensor move integrally has been described. However, in this embodiment, the focus detection sensor 112 is fixed at a predetermined position, and only the beam splitter 303 is the first and second. Move up and down between mode positions.

  Further, as shown in FIGS. 22A and 22B, in the beam splitter 103 arranged at any mode position, the light flux (image display or photographing) in the optical path from the imaging optical system 102 toward the image sensor 106 is also obtained. All of the light beams effective for the light are incident on the beam splitter 103. Specifically, at the first mode position, all the light beams in the upper and lower regions (first prism 303-1 and second prism 303-2 described later) of the beam splitter 303 sandwiching the light beam separation function surface 303a. Is incident. Further, at the second mode position, all the light beams are incident on a region (second prism 303-2) below the light beam separation function surface 303a.

  For this reason, the optical path length from the imaging optical system 102 to the image sensor 106 does not vary between the first mode and the second mode. Therefore, it is not necessary to correct the focus position depending on the mode.

  Further, since the optical path length does not change even during the switching between the first mode and the second mode, it is possible to check the image fluctuation state on the display 107, and frames are dropped until just before shooting is started. The photographer can check the photographed image. Therefore, a short release time lag can be realized without impairing the high-speed focus detection operation.

  23A and 23B show the configuration of the beam splitter 303 in detail. Similar to the first embodiment, the beam splitter 303 of the present embodiment is also manufactured by bonding the first and second prisms 303-1 and 303-2 with the surfaces 303-1a and 303-2a. The incident surface 303b of the beam splitter 303 includes a surface 303-1b of the first prism 303-1 and a surface 303-2b of the second prism 303-2. However, the region formed above the surface 303-2b functions as the AF exit surface 303f.

  Further, the exit surface 303d of the straight light from the incident surface 303b is composed of a surface 303-1d of the first prism 303-1 and a surface 303-2d of the second prism 303-2.

  Both the prisms 303-1 and 303-2 are formed of the materials described in the first embodiment. Further, the surfaces 303-1b and 303-1d of the first prism 303-1 and the surfaces 303-2b and 303-2d of the second prism 303-2 are parallel to each other and spaced apart from each other.

  Further, the two angles formed by the surface 303-1a of the first prism 303-1 with respect to the surfaces 303-1b and 303-1d are such that the surface 303-2a of the second prism 303-2 is the surface 303-1d. And two angles formed with respect to the surface 303-1b. Therefore, when the first prism 303-1 and the second prism 303-2 are joined by the surfaces 303-1a and 303-2a (the joined surface is denoted as 303a), the joined beam splitter 303 is Optically, it exhibits the same characteristics as a parallel plate. Therefore, no matter what region of the incident surface 303b the light beam enters, it transmits through the same wavefront, so that no aberration changes regardless of the incident position.

  In the second prism 303-2, as shown in FIG. 23A, the angle formed between the surface 303-2a and the surface 303-2b is the same as the angle formed between the surface 303-2c and the surface 303-2b. It has substantially the same trapezoidal cross section.

  A dielectric multilayer film similar to that of the first embodiment is formed on the surface 303-2a of the second prism 303-2 in order to provide the surface 303a of the beam splitter 303 with a light beam separation function. Then, the second prism 303-2 is bonded to the first prism 303-1 using an optical adhesive having index matching.

  The optical characteristics of the light beam separation function surface 303a are as shown in FIG. An antireflection coating AR is formed on the incident surface 303b of the beam splitter 303, and its characteristics are as shown in FIG.

  In addition, an infrared (IR) cut filter film 303 e is formed on the exit surface 303 d of the beam splitter 303. By this IR cut filter film 303e, only the visible region wavelength can reach the image sensor 106, and a camera with good color reproducibility can be constructed.

  Further, a reflection mirror coating with a metal film is applied to a surface 303-2c (reflection surface 303c of the beam splitter 303) formed on the upper portion of the second prism 303-2. Of the light beams incident on the inside from the incident surface 303b of the beam splitter 303, the light beam reflected by the light beam separation function surface 303a is internally reflected (total internal reflection) by the incident surface 303b of the beam splitter 303. Further, the light is reflected by the mirror-coated reflective surface 303 c, emitted from the AF exit surface 303 f, and guided to the focus detection sensor 112.

  24A and 24B show the state of the light beam guided to the focus detection sensor 112 by the beam splitter 303. FIG. In FIG. 24A, the optical axis 110a goes straight, and instead, the second prism 303-2 is folded back on each reflecting surface, and the light beam travels in the second prism 303-2. Is shown. FIG. 24B shows a state in which the light beam in FIG. 24A is folded again and developed in the second prism 303-2.

  As shown in FIG. 24A, the entrance surface 303-2b and the exit surface 303-2b are equivalent to optically flat surfaces, and even if the beam splitter 303 is displaced in the vertical direction, the optical path length is It does not change. 110b indicates the optical axis when the beam splitter 303 is displaced in the vertical direction. However, if the beam splitter 303 is displaced in the direction of the optical axis, the optical path length is changed by twice the amount of displacement as in the case of a general mirror system. In the present embodiment, the shift in the optical axis direction can be suppressed by employing the holding structure and the drive mechanism as shown in FIG. 20 of the first embodiment. In this embodiment, only the beam splitter 303 is held by the splitter frame.

  Furthermore, the deviation of the beam splitter 303 in the optical axis direction can be suppressed by a method of urging the splitter frame to one side in the optical axis direction with a spring to eliminate the engagement play with the guide rod.

  In this embodiment, since the focus detection sensor 122 is fixed and only the beam splitter 303 needs to be moved, the size in the vertical direction can be reduced, and the degree of design freedom in the lens barrel can be increased. it can.

  FIG. 25 shows the configuration of a lens barrel of a digital still camera (second imaging technology) that is Embodiment 3 of the present invention. In the present embodiment, components common to the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  FIG. 25A shows a configuration in the first mode in which focus detection is performed by the focus detection sensor 112. In the first mode position, the light beam separation function surface 403 a of the beam splitter 403 is disposed in the optical path from the imaging optical system 102 toward the image sensor 106. Therefore, a part of the light beam in the optical path is separated into an AF light beam toward the focus detection sensor 112 and an image display light beam toward the image sensor 106 by the light beam separation function surface 403a. Further, the light beam that does not pass through the light beam separation function surface 403 a passes through the beam splitter 403 and travels toward the image sensor 106.

  FIGS. 25B and 25C show the configuration in the second mode in which shooting and independent TV-AF are performed. At these second mode positions, the light beam separation function surface 403a of the beam splitter 403 is disposed outside the optical path from the imaging optical system 102 toward the image sensor 106. For this reason, of the light beams from the imaging optical system 102, a light beam effective for photographing toward the image sensor 106 passes through the beam splitter 403 and reaches the image sensor 106 without passing through the light beam separation function surface 403a. However, in FIGS. 25A and 25B, the region through which the light beam passes through the beam splitter 403 is different in the vertical direction. In the following description, the state of FIG. 25B is referred to as the 2a mode, and the position at this time is referred to as the 2a mode position. The state shown in FIG. 25C is referred to as a second b mode, and the position at this time is referred to as a second b mode position.

  In the first embodiment, the case where the beam splitter 403 and the focus detection sensor 112 move integrally has been described. However, in the present embodiment, the focus detection sensor 112 is fixed at a predetermined position, and only the beam splitter 403 includes the first to first sensors. Move up and down between third mode positions.

  Further, as shown in FIGS. 25A, 25B, and 25C, in the beam splitter 403 arranged at any mode position, the light flux (in the optical path from the imaging optical system 102 toward the image sensor 106) ( All of the luminous flux effective for image display and photographing enters the beam splitter 403. Specifically, at the first mode position, all the light beams in the upper and lower regions (first prism 403-1 and second prism 403-2 described later) of the beam splitter 403 sandwiching the light beam separation function surface 403a. Is incident. Further, at the 2a mode position, all the light beams are incident on a region (second prism 403-2) below the light beam separation function surface 403a. Furthermore, at the 2b mode position, all the light beams are incident on a region (first prism described later) above the light beam separation function surface 403a.

  For this reason, the optical path length from the imaging optical system 102 to the image sensor 106 does not vary in the first mode, the second a mode, and the second b mode. Therefore, it is not necessary to correct the focus position depending on the mode.

  In addition, since the optical path length does not fluctuate during the switching between the modes, it is possible to check the fluctuation state of the image on the display 107, and the photographer does not drop a frame until just before the photographing is started. The captured image can be confirmed. Therefore, a short release time lag can be realized without impairing the high-speed focus detection operation.

  FIG. 26 shows the configuration of the beam splitter 403. Similar to the first embodiment, the beam splitter 403 is manufactured by bonding a first prism 403-1 and a second prism 403-2 made of a transparent body with surfaces 403-1a and 403-2a. . The incident surface 403b of the beam splitter 403 shown in FIG. 26B is composed of a surface 403-1b of the first prism 403-1 and a surface 403-2b of the second prism 403-2.

  Further, the exit surface 403d of the straight light from the incident surface 403b is composed of a surface 403-1d of the first prism 403-1 and a surface 403-2d of the second prism 403-2.

  Both the prisms 403-1 and 403-2 are made of the same material as in the first embodiment. The relationship between each surface of the first prism 403-1 and each surface of the second prism 403-2 is the same as in the first embodiment.

  In addition, a dielectric multilayer film is formed on the surface 403-2a of the second prism 403-2 so that the surface 103a of the beam splitter 103 has a light beam separating function. Then, the second prism 403-2 is bonded to the first prism 403-1 using an optical adhesive that has undergone index matching.

  The optical characteristics of the light beam separation function surface 403a are as shown in FIG. Further, an antireflection coating AR is formed on the incident surface 403b of the beam splitter 403, and the characteristics are as shown in FIG.

  In addition, an ND (Neutral Density) filter 403g is formed on the surface 403-2d of the second prism 403-2 except for an emission region to the focus detection sensor 112. Further, an IR cut filter film is formed on the front surface (on the beam splitter 403 side) of the low-pass filter 113 shown in FIG.

  The ND filter is a kind of light absorption film, and is composed of a vapor deposition film such as chromel, and can obtain flat transmission characteristics over a very wide wavelength range. Chromel is an alloy containing nickel (Ni) as a main component and has a composition ratio of Cr: 7.0 to 10.5%, Mn: 1.5% or less, Si: 1.0 or less. FIG. 27 shows an example of the optical characteristics of the ND filter 403g using a chromel deposited film. In this embodiment, an ND filter that reduces the amount of light by approximately half is used.

  FIG. 28 is a diagram illustrating the luminance of an object photographed by the image sensor 106, where (a) is an image at Fno2.8, (b) is an image at Fno4, and (c) is an image at Fno8. The shaded portion in the image is an image portion formed by the light beam that has passed through the light beam separation function surface 403a and the ND filter 403g.

  As shown in FIGS. 28A to 28C, the state of luminance unevenness in a captured image obtained by the image sensor 106 has a difference in the upper and lower sides, and also varies depending on Fno. However, the spectral characteristics are substantially the same regardless of the image height and Fno. For this reason, at the time of reproduction processing on the display 107, appropriate brightness correction parameters corresponding to Fno are stored in advance, and the reproduction processing is performed by the camera system control circuit 135 shown in FIG. 2 based on the Fno information. To control. As a result, it is possible to display a reproduced image without a sense of incongruity.

  As shown in FIG. 26A, the second prism 403-2 has a parallelogram cross section having the same diagonal. By adopting such a shape, the same characteristics as those of the beam splitter 303 described in the second embodiment (FIG. 24) are obtained, and the entrance surface 403b and the exit surface 403b are equivalent to an optically flat transmission surface. For this reason, even if the beam splitter 403 is displaced in the vertical direction, the optical path length does not change. In this case, since it is a flat transmission surface, the optical path length does not deviate even if the beam splitter 403 is displaced in the optical axis direction, and the allowable value with respect to the shake of the attitude of the beam splitter 403 is increased compared to the second embodiment. be able to.

  In this embodiment, when the subject is too bright and overexposed in the 2a mode, the beam splitter 403 is disposed at the 2b mode position shown in FIG. be able to. That is, the beam splitter 403 that originally has the function of separating the AF light beam and the photographing light beam can also serve as an ND filter that can advance and retreat with respect to the optical path.

  In this embodiment, an example is shown in which an ND filter that substantially halves the amount of light is used. However, it is possible to increase the dynamic range of brightness by increasing the dimming ratio of the ND filter. In that case, the luminance distribution of the photographed image is different from that in FIG. 28 and becomes darker in the upper part. However, by storing the luminance correction parameter for correcting the luminance distribution, it is possible to obtain a display image without a sense of incongruity. Become.

  In the present embodiment, the case where two second mode positions are provided has been described. However, the present invention is not limited to two positions, and three or more positions may be provided. In this case, if the density (transmittance) of the ND filter formed in the region where the light beam is transmitted at each position is different from each other, various dimming ratios can be selected.

  FIG. 29 shows the configuration of a lens barrel of a digital still camera (first and third imaging technologies) that is Embodiment 4 of the present invention. The beam splitter 503 in the present embodiment has basically the same configuration as the beam splitter 103 in the first embodiment, and the first prism 503-1 and the second prism 503-2 are arranged at the position of the light beam separation function surface 503a. It is manufactured by joining with. Further, in the present embodiment, the same reference numerals as those in the first embodiment are assigned to components common to the first embodiment other than the beam splitter 503.

  FIGS. 29A to 29C show the configuration in the first mode in which focus detection is performed by the focus detection sensor 112. FIG. At these first mode positions, the light beam separation function surface 503 a of the beam splitter 503 is disposed in the optical path from the imaging optical system 102 toward the image sensor 106. Therefore, a part of the light beam in the optical path is separated into an AF light beam toward the focus detection sensor 112 and an image display light beam toward the image sensor 106 by the light beam separation function surface 503a. Further, the light beam that does not pass through the light beam separation function surface 503 a passes through the beam splitter 503 and travels toward the image sensor 106.

  However, in FIGS. 29A to 29C, the vertical direction position of the light beam separation function surface 503a is different, and accordingly, the focus detection field of the focus detection sensor 112 is different. In the following description, the state of FIG. 29A is referred to as a 1a mode, and the position at this time is referred to as a 1a mode position. The state shown in FIG. 29B is referred to as a 1b mode, and the position at this time is referred to as a 1b mode position. Further, the state of FIG. 29C is referred to as a first c mode, and the position at this time is referred to as a first c mode position.

  Although not shown, in the second mode in which shooting and independent TV-AF are performed, the light beam separation function surface 403a of the beam splitter 503 is disposed outside the optical path from the imaging optical system 102 toward the image sensor 106. For this reason, of the light beams from the imaging optical system 102, a light beam effective for photographing toward the image sensor 106 passes through the beam splitter 503 and reaches the image sensor 106 without passing through the light beam separation function surface 503a.

  As shown in FIGS. 29A, 29B, and 29C, the imaging optical system 102 is also used in the beam splitter 503 disposed at any mode position (including a second mode position not shown). All of the light flux (light flux effective for image display and photographing) in the optical path from the light to the image sensor 106 enters the beam splitter 403. Specifically, in the 1a to 1c mode positions, all the light beams in the upper and lower regions (first and second prisms 503-1 and 503-2) of the beam splitter 403 sandwiching the light beam separation function surface 503a. Is incident. In the second mode position, all the light beams are incident on the region (second prism 503-2) below the light beam separation function surface 503a. For this reason, the optical path length from the imaging optical system 102 to the image sensor 106 does not fluctuate in the first to second modes and the second mode. Therefore, it is not necessary to correct the focus position depending on the mode.

  In addition, since the optical path length does not fluctuate during the switching between the modes, it is possible to check the fluctuation state of the image on the display 107, and the photographer does not drop a frame until just before the photographing is started. The captured image can be confirmed. Therefore, a short release time lag can be realized without impairing the high-speed focus detection operation.

  In the present embodiment, the beam splitter 503 and the focus detection sensor 112 are fixed, and similarly to the first embodiment, the beam splitter 503 and the focus detection sensor 112 are moved in the vertical direction by the drive mechanism shown in FIG. Then, by controlling the number of pulses for the microstepping motor 203, the light beam separation function surface 503a can be stopped at an arbitrary position.

  FIG. 30 shows a focus detection field of the focus detection sensor 112 in the finder field 120. The focus detection visual field indicated by 550b is the same as the central focus detection visual field shown in FIG. In this embodiment, an upper focus detection visual field 550a and a lower focus detection visual field 550b are provided above and below the central focus detection visual field, respectively.

  The photographer can select one of the focus detection areas 550a to 550c via a field selection switch (not shown) or a selection unit of the line-of-sight input device, and the camera system control circuit 135 responds to the selection input. By controlling the micro stepping motor 203, the beam splitter 503 is positioned at any one of the 1a to 1c mode positions. As a result, phase difference AF is performed on the subject existing in the selected focus detection field of view. Note that TV-AF subsequent to phase difference AF in the normal AF mode is also performed based on the high-frequency component of the image region corresponding to the selected focus detection visual field.

  The vertical length of the prism 505-2 that guides the light beam reflected by the light beam separation function surface 503a in the beam splitter 505 of the present embodiment to the focus detection sensor 112 is a position corresponding to the vicinity of the lower end of the image sensor 106 (first c When the light beam separation function surface 503a is disposed at the (mode position), the exit to the focus detection sensor 112 is set to be positioned slightly above the upper end surface of the image sensor 106. This prevents the beam splitter 505 from becoming unnecessarily large (long).

  FIG. 31 is a diagram illustrating the luminance of an object photographed by the image sensor 106. FIG. 31A is an image of Fno4 and the beam splitter 503 is disposed at the 1a mode position of FIG. 29A. It is. FIG. 31B is an image when Fno4 and the beam splitter 503 is disposed at the 1b mode position in FIG. 29B. Further, FIG. 31C is an image when Fno4 and the beam splitter 503 is positioned at the 1c mode position of FIG. 29C.

  Also, the luminance distribution of the captured image differs depending on Fno as in the first embodiment. In this embodiment, appropriate brightness correction parameters corresponding to the positions of Fno and the focus detection visual field are stored in advance, and the camera system control 135 shown in FIG. 2 is based on the Fno information and the position information of the focus detection visual field. To control the playback process. As a result, it is possible to display a reproduced image without a sense of incongruity.

  In the present embodiment, the case where the first mode position is provided at three positions has been described. However, the present invention is not limited to the three positions, and may be provided at two positions or at four or more positions.

  FIG. 32 shows the configuration of the lens barrel of a digital still camera (second imaging technology) that is Embodiment 5 of the present invention. In the present embodiment, components common to the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  FIG. 32A shows a configuration in the first mode in which focus detection is performed by the focus detection sensor 112. In the first mode position, the light beam separation function surface 603 a of the beam splitter 603 is disposed in the optical path from the imaging optical system 102 toward the image sensor 106. Therefore, a part of the light beam in the optical path is separated into an AF light beam toward the focus detection sensor 112 and an image display light beam toward the image sensor 106 by the light beam separation function surface 603a. Further, the light beam that does not pass through the light beam separation function surface 603 a passes through the beam splitter 603 and travels toward the image sensor 106.

  On the other hand, FIG. 32B shows a configuration in the second mode in which shooting and independent TV-AF are performed. At the second mode position, the light beam separation function surface 603a of the beam splitter 603 is disposed outside the optical path from the imaging optical system 102 toward the image sensor 106. For this reason, of the light beams from the imaging optical system 102, a light beam effective for photographing toward the image sensor 106 passes through the beam splitter 603 and reaches the image sensor 106 without passing through the light beam separation function surface 603 a.

  In any of the beam splitters 603 disposed at any mode position, all the light beams (light beams effective for image display and photographing) in the optical path from the imaging optical system 102 toward the image sensor 106 are incident on the beam splitter 603. . Specifically, at the first mode position, all the light beams in the upper and lower regions (first prism 603-1 and second prism 603-2 described later) of the beam splitter 603 sandwiching the light beam separation function surface 603a. Is incident. Further, at the second mode position, all the light beams are incident on a region (second prism 603-2) below the light beam separation function surface 103a.

  As shown in FIG. 33A, the beam splitter 603 of this embodiment is manufactured by bonding the first and second prisms 603-1 and 603-2 with surfaces 603-1 a and 603-2 a. . An incident surface 603b of the beam splitter 603 includes a surface 603-1b of the first prism 603-1 and a surface 603-2b of the second prism 603-2. Further, an exit surface 603d of the straight light from the incident surface 603b is composed of a surface 603-1d of the first prism 603-1 and a surface 603-2d of the second prism 603-2.

  The first prism 603-1 is formed by bonding quartz 603-11, 603-12, 603-13 (ordinary refractive index 1.546, extraordinary refractive index 1.555) together. Crystals 603-11, 603-12, and 603-13 have functions of an optical low-pass filter, a phase plate, and a low-pass filter, respectively. Thus, the first prism 603-1 is a three-sheet optical low-pass unit in which the phase plate is sandwiched between the two low-pass filters. Note that these crystals 603-11, 603-12, and 603-13 are joined by an optical adhesive that is index matched.

  The second prism 603-2 is made of a glass material LLF1 (refractive index: 1.54814). If the thicknesses of the first and second prisms 603-1 and 603-2 are the same, there is almost no difference in optical path length of light beams that pass through these prisms.

  The surface 603-1b and the surface 603-1d of the first prism 603-1 and the surface 603-2b and the surface 603-2d of the second prism 603-2 are parallel to each other and spaced apart from each other.

  Further, the two angles formed by the surface 603-1a of the first prism 603-1 with respect to the surfaces 603-1b and 603-1d are such that the surface 603-2a of the second prism 603-2 is the surface 603-1d. And two angles formed with respect to the surface 603-1b. For this reason, when the first prism 603-1 and the second prism 603-2 are joined by the surfaces 603-1a and 603-2a (the joined surface is denoted as 603a), the joined beam splitter 603 is Optically, it exhibits the same characteristics as a parallel plate. Therefore, no matter which region of the incident surface 603b the light beam enters, it passes through the same wavefront, so that no change in aberration occurs regardless of the incident position.

  In order to give the surface 603a of the beam splitter 603 a light beam separation function, a dielectric multilayer film is formed on the surface 603-2a of the second prism 603-2 as in the first embodiment. And the 2nd prism 603-2 is bonded with the 1st prism 603-1 using the optical adhesive agent which took the index matching. The optical characteristics of the light beam separation function surface 603a are as shown in FIG. Further, an antireflection coating AR having the characteristics shown in FIG. 7 is formed on the incident surface 603b surface and the AF exit surface 603c of the beam splitter 603.

  Further, an IR cut filter film 603e is formed on the exit surface 603d of the beam splitter 603. Thereby, only a visible region wavelength can reach the image sensor 106, and a camera with good color reproducibility can be constructed.

  On the other hand, as in the first embodiment, the focus detection sensor 112 emits light including infrared light from the AF exit surface 603c, so that the AF performance in a dark scene can be improved.

  According to the present embodiment, since the low-pass unit is integrally formed with the beam splitter, the number of optical units can be reduced as compared with the case where they are separately provided, which is advantageous for miniaturization.

  As described above, in each of the embodiments, the digital still camera has been described as an example. However, the present invention is not limited to the digital still camera, and may be applied to various imaging apparatuses such as a video camera, a monitoring camera, a web camera, and a mobile phone. Can do.

  In each of the above embodiments, a compact camera with an integrated lens has been described. However, the present invention can be applied to a camera to which an interchangeable lens having various characteristics (such as an F number and a focal length) can be attached. it can.

  Further, in each of the above embodiments, the case where the beam splitter is moved in the vertical direction of the camera (the short side direction of the image sensor) has been described. However, the beam is moved in the horizontal direction of the camera (the long side direction of the image sensor) You may make it change the area | region which the light beam in a splitter permeate | transmits.

1 is a cross-sectional view of a digital camera that is Embodiment 1 of the present invention. 1 is a block diagram illustrating an electrical configuration of a digital camera according to Embodiment 1. FIG. Sectional drawing of the lens-barrel part of the digital camera of Example 1 (1st mode). Sectional drawing of the lens-barrel part of the digital camera of Example 1 (2nd mode). FIG. 3 is a cross-sectional view of the beam splitter of the digital camera according to the first embodiment. FIG. 4 is a diagram illustrating optical characteristics of a light beam separation function surface in the beam splitter according to the first embodiment. FIG. 3 is a diagram illustrating optical characteristics of an antireflection coating in the beam splitter according to the first embodiment. FIG. 3 is a diagram illustrating a focus detection field of the focus detection sensor in the digital camera according to the first embodiment. 2 is a plan view of a focus detection surface of a focus detection sensor in the digital camera of Embodiment 1. FIG. 2 is a cross-sectional view of a pixel portion of a focus detection sensor in the digital camera of Embodiment 1. FIG. The top view showing the photoelectric conversion part of 1 pixel of the focus detection sensor of FIG. 10, and the top view of this 1 pixel. The top view showing the pixel row | line | column which connected each pixel of the focus detection sensor of FIG. FIG. 11 is a perspective view illustrating a pixel row in which pixels of the focus detection sensor in FIG. 10 are connected. FIG. 11 is a plan view showing an opening of a first wiring layer of the focus detection sensor of FIG. 10. FIG. 11 is a partial cross-sectional view of a focus detection visual field of the focus detection sensor of FIG. 10. FIG. 11 is a partial cross-sectional view of a focus detection visual field of the focus detection sensor of FIG. 10. The figure showing the output signal waveform of the focus detection sensor of FIG. The figure showing the output signal waveform of the focus detection sensor of FIG. FIG. 4 is a diagram for explaining a state of luminance unevenness in the first embodiment. FIG. 3 is a diagram illustrating a beam splitter driving mechanism according to the first embodiment. 5 is a flowchart of a shooting sequence in the digital camera of Embodiment 1. Sectional drawing of the lens-barrel part in the digital camera which is Example 2 of this invention. FIG. 6 is a cross-sectional view of a beam splitter in the digital camera of Embodiment 2. Explanatory drawing of the light ray in the beam splitter of Example 2. FIG. Sectional drawing of the lens-barrel part in the digital camera which is Example 3 of this invention. FIG. 6 is a cross-sectional view of a beam splitter in the digital camera of Embodiment 3. 10 is a diagram illustrating an example of optical characteristics of an ND filter in the digital camera of Embodiment 3. FIG. FIG. 10 is a diagram for explaining a state of luminance unevenness in the third embodiment. Sectional drawing of the lens-barrel part in the digital camera which is Example 4 of this invention. FIG. 6 is a diagram for explaining a focus detection visual field in the digital camera according to the fourth embodiment. FIG. 6 is a diagram for explaining a state of luminance unevenness in Example 4; Sectional drawing of the lens-barrel part in the digital camera which is Example 5 of this invention. FIG. 10 is a cross-sectional view of a beam splitter in the digital camera of Example 5.

Explanation of symbols

102 Imaging optical system 103, 303, 403, 503, 603 Beam splitter 103a, 303a, 403a, 503a, 603a Beam separation function surface 105 Lens barrel 106 Imaging element 112 Focus detection sensor 113 Optical low-pass filter 201 Splitter frame 202 Guide rod 203 Micro stepping motor 204 Lead screw

Claims (10)

An image sensor that photoelectrically converts a subject image;
Focus detection means for performing focus detection using a luminous flux from a subject;
An optical member provided with a light beam separation surface that separates a light beam from a subject into a light beam directed to the image sensor and a light beam guided to the focus detection unit;
The imaging apparatus according to claim 1, wherein the optical member is movable to a plurality of positions where the focus detection visual fields by the focus detection means are different from each other. An image sensor that photoelectrically converts a subject image;
An optical member provided with a light beam separation surface that separates a light beam from a subject into a light beam directed to the image sensor and a light beam guided to the focus detection unit;
The optical member is movable to a first position where the light beam separation surface is disposed in the optical path to the image sensor and a second position where the light beam separation surface is disposed outside the optical path,
The imaging apparatus according to claim 1, wherein the optical member has a size such that the entire light beam in the optical path is incident at each of the first and second positions. An image sensor that photoelectrically converts a subject image;
Focus detection means for performing focus detection using a luminous flux from a subject;
An optical member provided with a light beam separation surface that separates a light beam from a subject into a light beam directed to the image sensor and a light beam guided to the focus detection unit;
The optical member has a first position where the light beam separation surface is disposed in the optical path to the image sensor and the light beam separation surface disposed outside the optical path, and a portion other than the light beam separation surface is a light beam from the subject. The image pickup apparatus is capable of moving to a second position that passes through the image pickup device through the image pickup device.   The imaging apparatus according to claim 2, wherein the optical member is movable to a plurality of the first positions in which focus detection visual fields by the focus detection unit are different from each other.   5. The imaging apparatus according to claim 1, further comprising: a driving unit that drives the optical member to a position corresponding to a focus detection visual field selected from the plurality of positions. 6.   The imaging apparatus according to claim 1, wherein an infrared cut filter is provided on a surface of the optical member that transmits a light beam directed toward the imaging element.   The imaging apparatus according to claim 1, wherein a low-pass filter is provided on a surface of the optical member that transmits a light beam directed toward the imaging element. The optical member is movable to a plurality of positions where areas through which a light beam from a subject is transmitted are different from each other.
The imaging apparatus according to claim 1, wherein the plurality of regions have different transmittances. Image processing means for generating an image based on an output from the imaging element in a state where the optical member is disposed at the first position;
The image processing means uses the information according to the light amount difference between the light beam that has passed through the light beam separation surface and reached the image sensor and the light beam that has reached the image sensor without passing through the light beam separation surface. The image pickup apparatus according to claim 1, wherein an image is generated. The optical member is disposed at a position where the light beam separation surface is in the optical path from the subject when observing the subject, and is disposed at a position where the light beam separation surface is outside the optical path from the subject during photographing. The imaging device according to any one of claims 1 to 9.