JP2007094073A - Focusing system and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent positional deviation in the acting position of a luminous flux branching means from exerting an influence upon precision of focusing, without increasing the scale of a system. <P>SOLUTION: A focusing system includes; a luminous flux branching means 103 which is disposed between a lens for imaging a subject luminous flux on an imaging surface and the imaging surface and is provided with a reflection face for separating the subject luminous flux outside an imaging optical path; a light reception means 112 which receives the subject luminous flux separated by the luminous flux branching means to obtain a signal for focus adjustment of the lens; and holding means 201 and 204 which hold the luminous flux branching means in either of the acting position where the luminous flux branching means is placed within the imaging optical path and a retreat position where it retreats from the imaging optical path. The holding means hold the luminous flux branching means so that it can be moved in a direction approximately parallel to the light reception means within a plane orthogonal to the imaging optical axis. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a focusing apparatus and an imaging apparatus that are disposed between a lens and an imaging surface and have a light beam branching unit that splits a subject light beam out of an imaging optical path.

  Conventionally proposed is a method of separating a subject luminous flux and guiding the subject luminous flux to a light receiving element for focus detection. Patent Document 1 relates to a camera equipped with a zoom lens, and is a disclosure example of a technique for separating a light beam in the middle of the optical path of the zoom lens and performing focus detection using the separated light beam. Patent Document 2 describes imaging optics. This is a disclosed example of a digital single-lens reflex camera that forms a primary object image formed by a system on a two-dimensional light receiving sensor such as a CCD sensor or a CMOS sensor and photoelectrically converts an optical image to obtain an image output related to the object.

  In these proposals, the subject light flux is divided into an imaging sensor and a focus detection sensor by a beam splitter such as a beam splitter, and the focus state is detected on the focus detection sensor side, and shooting is performed on the imaging sensor side. Yes.

In Patent Document 3, a focus detection sensor can be inserted into and retracted from the imaging optical axis. When performing a focusing operation, the focus detection sensor is inserted into the imaging optical axis. It is configured to be evacuated.
JP-A 63-195630 JP 2003-140246 A JP 11-352393 A

  In the above conventional example, a beam splitter such as a beam splitter or a main mirror is provided in the subject beam. When such a beam splitter is used, the amount of light incident on the image sensor is generally reduced. As a countermeasure, in Patent Document 2, a part of the light beam branching unit (main mirror) is retracted at the time of photographing so that the total amount of light enters the sensor. However, in this case, since the retracting operation of the light beam branching unit is performed every time photographing is performed, there is a problem that an unstable element of the mechanism accompanying the retracting operation affects the focusing accuracy.

(Object of invention)
An object of the present invention is to provide a focusing apparatus and an imaging apparatus capable of preventing the positional deviation at the operating position of the light beam branching unit from affecting the focusing accuracy without causing an increase in the size of the apparatus. is there.

  In order to achieve the above object, the present invention provides a light beam branching unit including a lens that forms an image of a subject light beam on an imaging surface and a reflecting surface that is disposed between the imaging surface and separates the subject light beam out of the imaging light path. A light receiving means for receiving a subject light beam separated by the light beam branching means to obtain a signal for adjusting the focus of the lens, an operating position for positioning the light beam branching means in the imaging optical path, and in the imaging optical path Holding means for holding at any one of the retreat positions for retreating from the light source, and the holding means is in a direction substantially parallel to the light receiving means in a plane perpendicular to the imaging optical axis. And a focusing device that is movably held, or an imaging device including the focusing device.

  Similarly, in order to achieve the above object, the present invention provides a light beam including a lens that forms an image of a subject light beam on an imaging surface and a reflection surface that reflects the incident light beam outside the imaging light path. A branching unit; a light receiving unit that receives a subject light beam reflected by the light beam branching unit to obtain a signal for adjusting the focus of the lens; a working position that positions the light beam branching unit in the imaging optical path; Holding means for holding at any one of the retreat positions for retreating from the imaging optical path, and the holding means is capable of moving the light beam branching means in a direction substantially perpendicular to the plane including the incident / reflected optical axis. A focusing device to be held or an imaging device including the focusing device is provided.

  Similarly, in order to achieve the above object, the present invention provides a bending optical system that reflects a subject light beam and forms an image on an imaging surface, and a reflecting surface that separates the subject light beam outside the imaging optical path. A light beam branching means, a light receiving means for receiving a subject light beam separated by the light beam branching means to obtain a signal for adjusting the focus of the lens, and an action for positioning the light beam branching means in the imaging optical path Holding means for holding at any one of a position and a retreat position for retreating from the imaging optical path, and the holding means is arranged on the light receiving means within a plane perpendicular to the imaging optical axis. On the other hand, the focusing device is configured to be held so as to be movable in a substantially parallel direction, or an imaging device including the focusing device.

  Similarly, in order to achieve the above object, the present invention is arranged between a bending optical system that reflects a subject light beam to form an image on an imaging surface and the reflection surface that reflects the incident subject light beam outside the imaging optical path. A light beam branching means having a surface, a light receiving means for receiving a subject light beam reflected by the light beam branching means to obtain a signal for adjusting the focus of the lens, and the light beam branching means positioned in the imaging optical path. And holding means for holding at any one of the retracted position for retracting from the imaging optical path, and the holding means is substantially orthogonal to the plane including the incident / reflecting optical axis. The focusing device is held so as to be movable in the direction, or the imaging device includes the focusing device.

  According to the present invention, it is possible to provide a focusing device or an imaging device that can prevent the positional deviation at the operation position of the light beam branching unit from affecting the focusing accuracy without causing an increase in the size of the device.

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

  FIG. 1A is a side sectional view of a digital camera according to Embodiment 1 of the present invention, and FIG. 1B is a top sectional view of the digital camera according to Embodiment 1 of the present invention. These are states in which focus adjustment is performed, and a captured image and a display image are captured in a display device on the back side when preparing for capturing.

  In FIGS. 1A and 1B, 101 is a digital camera, 102 is an imaging optical system for forming an object image, 104 is an optical axis of the imaging optical system 102, and 105 is housing the imaging optical system 102. This is a lens barrel.

  The imaging optical system 102 can adjust the imaging position in the direction of the optical axis 104 by an energy source (not shown) and a driving mechanism (not shown). The focusing lens can be composed of a flexible transparent elastic member or a liquid lens, and the object can be focused by changing the refractive power by changing the interface shape. The imaging optical system 102 may be a single focus lens, a zoom lens, a shift lens, or the like. Further, it may be exchangeable for an imaging optical system having various characteristics (F number, focal length, etc.). As a material of the lens constituting the imaging optical system 102, a composite material in which niobium oxide particles having a size of about 5 nm to 30 nm are uniformly dispersed in an acrylic resin can be used. According to this, although it has a high refractive index of about 1.8, it is more resistant to impact than glass and can be manufactured at low cost by injection molding.

  Reference numeral 103 denotes a beam splitter as beam splitting means, 110 denotes an optical axis in the beam splitter 103, 111 denotes a shutter release button, 108 denotes a memory card for storing image data, and 109 denotes an eyepiece of an optical viewfinder. Reference numeral 106 denotes an image sensor which is a two-dimensional CCD or CMOS light receiving sensor, 112 denotes a focus detection sensor included in the AF module, and 113 denotes an optical low-pass filter. When the display image is captured and taken, the light beam that has passed through the beam splitter 103 and the optical low-pass filter 113 is projected onto the image sensor 106. Reference numeral 114 denotes a flat glass as an optical path length complementing optical system, which is inserted into the imaging light flux as the beam splitter 103 is retracted in the direction of the arrow 103y from the light flux (on the optical axis 104) to supplement the change in the optical path length. I am doing.

  Reference numeral 107 denotes a display device attached to the back of the camera, and an object image captured by the image sensor 106 is displayed on the display device 107. The user can determine the shooting composition by directly observing this during shooting preparation. If the display device 107 is composed of an organic EL spatial modulation element, a liquid crystal spatial modulation element, a spatial modulation element using microparticle electrophoresis, etc., it is convenient because it consumes less power and is thinner.

  The image sensor 106 performs an image output operation for the display device 107 by thinning readout and a high-definition image output operation for reading out all pixels at the time of shooting.

  FIG. 2 is a block diagram showing an electrical configuration of the digital camera 101. First, an explanation will be given from the part related to the imaging and recording of object images.

  The digital camera 101 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 information display circuit 142, an operation detection circuit 136, and an image sensor driving circuit 137. Reference numeral 138 denotes a standardized connection terminal for connecting to an external computer or the like to transmit / receive data. These electric circuits are driven by a small fuel cell (not shown).

  The imaging system is an optical processing system that forms an image of light from an object on the imaging surface of the imaging element 106 via the imaging optical system 102, and adjusts a diaphragm and a mechanical shutter (not shown) of the imaging optical system 102, An appropriate amount of object light is exposed to the image sensor 106. As the imaging device 106, a light receiving device having 3264 square pixels arranged in the long side direction and 2448 arranged in the short side direction and having a total number of about 8 million pixels is applied. Then, R (red), G (green), and B (blue) color filters are alternately arranged in each pixel to form a so-called Bayer array in which four pixels are a set. In the Bayer array, the overall image performance is improved by arranging more G pixels that are easily felt when an observer looks at the image than 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 is a circuit that converts a signal that is converted into, for example, a 12-bit digital signal according to the amplitude of the signal of each exposed pixel, and performs subsequent image signal processing by digital processing. Is done.

  The image processing system is a signal processing circuit that obtains an image signal of a desired format from R, G, and B digital signals. The R, G, and B color signals are converted into a luminance signal Y and a color difference signal (R−Y), ( B-Y) and the like are converted into a YC signal. The RGB image processing circuit 131 is a signal processing circuit that processes an image signal of 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, a gamma correction circuit, and an interpolation calculation circuit that performs high resolution by interpolation calculation.

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

  The recording / reproducing system is a processing system that outputs an image signal to the memory and outputs an image signal to the display device 107. The recording processing circuit 133 included in the recording / reproducing system performs processing for writing and reading image signals to / from the memory, and the reproduction processing circuit 134 reproduces the image signals read from the memory and outputs them to the display device 107. The recording processing circuit 133 includes a compression / expansion circuit that compresses YC signals representing still images and moving images in a predetermined compression format and expands the compressed data when it is read out. The compression / decompression circuit includes a frame memory or the like for signal processing, and stores the YC signal from the image processing system for each image in the frame memory, and reads and compresses each of the plurality of blocks. The compression encoding is performed, for example, by subjecting the image signal for each block to two-dimensional orthogonal transformation, normalization, and Huffman encoding. The reproduction processing circuit 134 is a circuit that performs matrix conversion 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 device 107, and a visible image is displayed and reproduced.

  The control system includes an operation detection circuit 136 that detects an operation of the shutter release button 111 and the like, and a camera system control circuit 135 that controls each unit in response to the detection signal and generates and outputs a timing signal at the time of imaging. including. Furthermore, under the control of the camera system control circuit 135, the image sensor driving circuit 137 that generates a drive signal for driving the image sensor 106, and the information display device in the optical viewfinder and the information display device on the outer surface of the camera are controlled. An information display circuit 142 is included. The control system controls the imaging system, the image processing system, and the recording / reproducing system in response to an external operation. Then, for example, pressing of the shutter 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 information display circuit 142 controls the state of each segment of the information display device that displays information on an optical finder or the like.

  An AF control circuit 140 and a lens system control circuit 141 are further connected to the camera system control circuit 135. These communicate with each other data necessary for each processing, centering on the camera system control circuit 135. The AF control circuit 140 obtains a signal output of the focus detection field of the focus detection sensor 112 set corresponding to a predetermined position on the imaging screen, generates a focus detection signal, and forms an imaging state of the imaging optical system 102. Is detected. When the defocus amount is detected, it is converted into a driving amount of a focusing lens which is a part of the imaging optical system 102, relayed by the camera system control circuit 135 and transmitted to the lens system control circuit 141. For a moving object, the focusing lens drive amount is instructed by predicting an appropriate lens position in consideration of a time lag from when the shutter release button 111 is pressed until actual imaging control is started. When it is judged that the brightness of the object is low and sufficient focus detection accuracy cannot be obtained, the object is illuminated by a flash light emitting device (not shown) or a white LED or fluorescent tube (not shown) to compensate for the insufficient brightness. .

  Upon receiving the driving amount of the focusing lens, 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 a driving mechanism (not shown) to focus on the object. As a result of a series of focus adjustment operations, when the AF control circuit 140 detects that the object is in focus, this information is transmitted to the camera system control circuit 135. At this time, when the shutter release button 111 is pushed down to the second stage and it is better to position the beam splitter 103 outside the imaging light beam, the beam splitter 103 and the flat glass plate 114 are replaced by a mechanism described later. As a result, a high-definition image is formed by the light flux that has passed through the optical low-pass filter 113, and imaging control is performed by the imaging system, image processing system, and recording / reproducing system as described above. At this time, since the flat glass 114 is inserted at the position where the beam splitter 103 is located so that the focus fluctuation of the imaging optical system 102 does not occur, it is not necessary to correct the focus. Therefore, a short release time lag can be realized without impairing the high-speed focus detection operation.

  3A is a side cross-sectional view of the lens barrel 105 portion of the digital camera 101 in a shooting preparation state, and FIG. 3B is a top cross-sectional view of the lens barrel 105 portion of the digital camera 101 in a shooting preparation state. FIG. 4A is a side sectional view in the photographing state, and FIG. 4B is a top sectional view in the photographing state. 5 is a cross-sectional view of the beam splitter 103, FIG. 6 is a perspective view of the beam splitter 103, and FIG. 7 is an exploded perspective view of the beam splitter 103. The beam splitter 103 and its peripheral part will be described in detail with reference to these drawings.

  The beam splitter 103 is positioned between the rear end of the lens group constituting the imaging optical system 102 and the image sensor 106. A focusing lens 102a moves in the direction of the optical axis 104 to adjust the focus. The image sensor 106 is positioned with respect to a fixed ground plate (not shown) of the lens barrel 105. In the visible wavelength region, the optical length of the beam splitter 103 is matched with the optical length determined by the thickness of the flat glass 114. Therefore, even when the beam splitter 103 shown in FIGS. 3A and 3B is retracted as shown in FIG. 4 and the flat glass 114 is inserted at that position, the image sensor 106 of the imaging optical system 102 is not affected. The image formation state on is not changed.

  A schematic imaging sequence is as follows. When it is detected that the shutter release button 111 has been pressed in the first stage, the image sensor 106 is driven to repeatedly capture an object image with the light beam transmitted through the beam splitter 103 and display the object image on the display device 107 in real time. Further, focus detection is performed using the focus detection sensor 112 with the light flux in the visible wavelength range divided by the beam splitter 103. When a defocus amount equal to or larger than a predetermined amount is detected, the driving amount of the focusing lens 102a is calculated, and the focusing lens 102a is moved in the direction of the optical axis 104 by that amount to adjust the focus. After focus adjustment is completed, focus detection is performed again using the focus detection sensor 112, and when it is confirmed that the defocus amount is within a predetermined range, a focus display by sound or light is issued.

  When the second stage pressing of the shutter release button 111 is detected, the beam splitter 103 is retracted from the optical path of the imaging optical system 102 in FIG. 3B in the direction of the arrow 103y by a mechanism described later, and a flat glass 114 is inserted instead. (See FIGS. 4A and 4B). The imaging device 106 is driven to perform imaging in the high definition mode. Then, after the photographing is finished, the flat glass 114 is retracted from the optical path of the imaging optical system 102, and the beam splitter 103 is returned to the original position (see FIGS. 3A and 3B). Image data relating to the imaged object image is written into the memory.

  Next, the light splitting function will be described in detail. As shown in FIGS. 5 to 7, the beam splitter 103 is obtained by bonding two prisms 103-1 and 103-2 with a light splitting functional surface 103a. The light incident surface of the beam splitter 103 is composed of the surface 103-1b of the prism 103-1, and the surface 103-2b of the prism 103-2, and the exit surface of the straight light is the surface 103-1d of the prism 103-1, and the prism 103. -2 surface 103-2d. There is no step between the surface 103-1b of the prism 103-1 and the surface 103-2b of the prism 103-2, or the step between the surface 103-1d of the prism 103-1 and the surface 103-2d of the prism 103-2. Further, the surfaces 103-1b and 103-1d of the prism 103-1, and the surfaces 103-2b and 103-2d of the prism 103-2 are parallel to each other. Therefore, the beam splitter 103 functions as a parallel plate for light traveling straight.

  The surface 103-1b and the light dividing functional surface 103a of the prism 103-1, and the surface 103-2d of the prism 103-2 and the light dividing functional surface 103a have different inclination angles. The surface 103-1b of the prism 103-1 and the light splitting functional surface 103a, and the surface 103-2b of the prism 103-2 and the light splitting functional surface 103a intersect each other.

  The light splitting function surface 103a of the beam splitter 103 is formed with a dielectric multilayer film on the surface 103-2a of the prism 103-2 in order to obtain desired optical characteristics. And it forms by bonding together with the surface 103-1a of the prism 103-1, using the optical adhesive which took the index matching. The optical characteristics of the light splitting functional surface 103a are as shown in FIG. 8, and the spectral transmittance characteristics from a wavelength of 400 nm to 1000 nm are valley-shaped having a minimum value near 500 nm, while the spectral reflectance characteristics are maximum near 500 nm. A mountain with a value. That is, a part of incident light in a predetermined wavelength region is reflected and the other part is transmitted. As a feature of the dielectric multilayer film, the absorption can be made small enough to be ignored. Therefore, the incident light is split in either direction of the image sensor 106 or the focus detection sensor 112 on the light splitting function surface 103a.

  Here, in the visible region from 450 nm to 650 nm, the spectral transmittance characteristic is constant at about 45%. In a color camera, the sensitivity range of the image sensor 106 is matched with the visibility range, so it can be said that the spectral reflectance characteristic is flat in the sensitivity wavelength range of the image sensor 106.

  Of the light beams incident on the inside of the beam splitter 103 from the light incident surface formed by the surface 103-1 b of the prism 103-1 and the surface 103-2 b of the prism 103-2, the light beam reflected by the light dividing function surface 103 a is the prism 103-. Second surface 103-2b is totally reflected. And it injects from the surface 103-2c. A focus detection sensor 112 is provided at a position facing the surface 103-2c, and a light beam from the beam splitter 103 is incident thereon. As a result, the focus detection function operates.

  Thus, the spectral characteristics of the light beam divided by the beam splitter 103 is substantially the same as that of the straight-ahead light, and the focus detection function is operated by this light beam. Since the spectral reflectance characteristic here is approximately 55%, high-precision focus detection is possible with a sufficient amount of light. In order to precisely match the spectral sensitivity of the focus detection sensor 112 to the image sensor 106, it is better to add an infrared cut function to the incident surface protection glass of the focus detection sensor 112.

  An ND (Neutral Density) filter is formed on the surface 103-1b of the prism 103-1 and the surface 103-2b of the prism 103-2. This ND filter is a kind of light absorption film, and a vapor deposition film such as chromel is used, and a flat transmission characteristic can be obtained 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. 9 is an example of optical characteristics of an ND filter using a chromel deposited film. In the visible region from 450 nm to 650 nm, the spectral transmittance is constant at about 45%, and since there is much absorption, the spectral reflectance during this period is about 15%.

  Next, the focus detection sensor 112 will be described. FIG. 10 is a diagram showing a focus detection field of view by the focus detection sensor 112.

  In FIG. 10, reference numeral 120 denotes a finder field with the imaging range as the observation range, and reference numerals 121-1 to 121-9 denote focus detection fields. If the focus detection field is set near the center of the imaging range, the camera is easy to use. Since the focus detection visual field formed by the vertical pixel rows is sensitive to the luminance distribution in the vertical direction, for example, focus detection can be performed on horizontal lines. On the other hand, the focus detection visual field constituted by the pixel rows in the horizontal direction is sensitive to the luminance distribution in the horizontal direction, so that, for example, focus detection with respect to vertical lines is possible.

  The actual focus detection sensor 112 is configured as shown in FIG. FIG. 11 is a plan view of the focus detection sensor 112, and reference numerals 112-1 to 112-9 denote pixel rows constituting the focus detection visual fields 121-1 to 121-9.

  FIG. 12 is a cross-sectional view of the pixel portion of the focus detection field (for example, 121-1) of the focus detection sensor 112. FIG. 13A is a plan view showing a photoelectric conversion unit of one pixel of the focus detection sensor 112, and FIG. 13B shows a microlens arranged on the photoelectric conversion unit shown in FIG. 2 is a plan view of one pixel of a focus detection sensor 112. FIG.

  In FIG. 12, light enters the focus detection sensor 112 from above in the figure, and in FIGS. 13A and 13B, the light enters the focus detection sensor 112 from the front side of the drawing. The focus detection sensor 112 is a CMOS type sensor having a one-chip type microlens, and the F number of the focus detection light beam can be defined by the action of the microlens.

  In FIG. 12, reference numeral 151 denotes a silicon substrate, and 152A and 152B denote photoelectric conversion portions of embedded photodiodes. Reference numeral 154 denotes a first wiring layer having light shielding properties by aluminum or copper, and 155 denotes a second wiring layer using aluminum or copper. Reference numeral 156 denotes an interlayer insulating film and a passivation film made of a silicon oxide film, hydrophobic porous silica, silicon oxynitride film, silicon nitride film, or the like. 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 technique such as curing after spin coating a thermosetting resin or an ultraviolet curable resin, or bonding a resin film.

  As shown in FIG. 13A, the photoelectric conversion units 152A and 152B have a zigzag shape, and circuit portions 159A and 159B are connected to the ends, respectively. The circuit portions 159A and 159B include a transfer MOS transistor that functions as a transfer switch and a reset MOS transistor that supplies a reset potential. Furthermore, 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 provided. On the photoelectric conversion unit 152 (152A, 152B), as shown in FIG. 13B, five microlenses 158 are provided in a zigzag manner for each pixel.

Here, the microlens 158 is formed of resin, SiO ₂ , TiO ₂ , Si ₃ N ₄ or the like, and is used not only for focusing but also for imaging, so it is an axially symmetric spherical lens or axially symmetric. It is a type of aspherical lens. Since it is a shape having a symmetry axis 160 (see FIG. 12), it is circular when viewed in plan, but by providing a plurality of microlenses per pixel, the light receiving area of one pixel is reduced while reducing the pixel pitch. Can be enlarged. Therefore, a sufficient focus detection output can be obtained even for a low-luminance object. Further, for example, a shape having no symmetry axis such as a saddle shape is not suitable for the focus detection sensor 112 because there is no image forming action as a lens. Note that the microlens 158 may be formed with a thin film having a low refractive index or a fine structure (so-called Sub-WaveLength Structure) having a wavelength equal to or less than the wavelength of visible light on the surface in order to suppress surface reflection of light.

  The light beam emitted from the beam splitter 103 first enters the microlens 158 of the focus detection sensor 112, and then passes through the opening 155A provided in the second wiring layer 155 and the opening 154A provided in the first wiring layer 154. The components enter the photoelectric conversion unit 152A. Thereafter, components that have passed through the opening 155A provided in the second wiring layer 155 and the opening 154B provided in the first wiring layer are incident on the photoelectric conversion unit 152B and converted into electric signals, respectively. Since the light shielding layer for forming the opening is also used as the first wiring layer 154 and the second wiring layer 155, it is not necessary to provide a light shielding layer for the opening, and the configuration of the focus detection sensor 112 is simplified. It is possible.

  14 and 15 are a plan view and a perspective view showing a state in which the pixels shown in FIG. 13 are connected to form a pixel row for use in focus detection.

  In FIG. 14, the microlenses at both ends are not shown so that the positional relationship between the photoelectric conversion unit 152 (152A, 152B) and the microlens 158 can be understood, so that the photoelectric conversion unit can be seen. In FIG. 15, the photoelectric conversion unit 152, the first wiring layer 154, the second wiring layer 155, and the microlens 158 are extracted from among the constituent elements and are shown in an exploded vertical direction. 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 and the second wiring layer and indicated by a broken line.

  In FIG. 14, five microlenses 158a with dots form one pixel, and a large number of these pixels are arranged in the horizontal direction to form the pixel columns 112-1 to 112-9 shown in FIG. Yes. Since the microlenses arranged in a zigzag form just fill the space between the adjacent microlenses, the microlenses are densely arranged on the pixel array. Therefore, the amount of light that cannot be used without entering the microlens is negligibly small.

  Further, when attention is paid to the arrangement direction, the frequency response of pixels near the Nyquist frequency can be lowered by arranging in a zigzag manner. As a result, aliasing distortion hardly occurs even when an object image including a spatial frequency component higher than the Nyquist frequency is projected, and phase difference detection between output signal waveforms of the focus detection sensor 112 described later can be performed with high accuracy. Further, a microlens 158b indicated by hatching that does not contribute to photoelectric conversion is formed around the pixel column without being arranged on the photoelectric conversion unit. This is due to the manufacturing reason that the microlens can be manufactured with high accuracy by laying the microlens as uniformly as possible.

  The first wiring layer 154 shown in FIG. 15 has a large number of openings 154A and 154B that look like diamonds. As shown in FIG. 16 which is a plan view, a pair of these openings 154A and 154B are provided corresponding to each of the microlenses 158, and the depth direction thereof is located in the vicinity of the focal point of the microlens 158. . With such a configuration, the apertures 154A and 154B are back-projected onto the exit pupil of the imaging optical system 102 by the microlens 158, so that the light receiving angle characteristic of the light beam taken in by the pixels can be determined by the shape of the apertures 154A and 154B. It becomes possible. The opening 155A provided in the second wiring layer 155 is a stop for preventing light from entering the openings of the first wiring layer 154 other than the openings 154A and 154B. As a result, only the light beams that can enter 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.

  17 and 18 are partial cross-sectional views of the focus detection visual field 121-1 (pixel row 112-1) shown in FIG. 10. 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. Therefore, as shown in FIG. 17, the fact that the light beam 132A can pass through the opening 154A is equivalent to the light beam 132A being emitted from the back projection image of the opening 154A of the first wiring layer 154.

  Similarly, as shown in FIG. 18, 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 that have entered the focus detection sensor 112 from other than the backprojected 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. In the meantime, a relatively laterally shifted state is observed according to the imaging state of the object image formed by the imaging optical system 102 on the focus detection field. This is because the region where the light beam passes on the exit pupil of the imaging optical system is obtained by arranging 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 it differs from the obtained output signal waveform. 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.

  19 and 20 are diagrams showing 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. 19 shows the output signal waveform when the object image is not in focus, and FIG. 20 shows the output signal waveform when the object image is in focus. Thus, first, it is possible to detect focus by 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. 05-088445. 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 drive to the in-focus position is usually performed only once, and extremely high speed focus adjustment can be performed.

  Here, the focus detection light beam will be described. The focus detection sensor 112 controls the light receiving angle characteristic for each focus detection field, thereby varying the F number of the focus detection light beam 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 is large in the central focus detection visual field 121-1, and small in the peripheral focus detection visual field, for example, 121-4.

  FIG. 21 is a diagram for explaining a passing area of the focus detection light beam on the exit pupil of the imaging optical system 102. The pupil region 141 represents vignetting of the imaging optical system 102 when viewed from the end of the focus detection visual field 121-1. Further, the pupil region 145 is vignetting of the imaging optical system 102 when viewed from the ends of the focus detection visual fields 121-4, 121-5, 121-6, and 121-7. On the other hand, the passage areas 143A and 143B of the focus detection light beam in the focus detection visual field 121-1 are located inside the pupil area 141. In addition, the passage areas 144A and 144B of the focus detection light beam in the focus detection visual field 121-4 are located inside the pupil area 145.

  The wider the detection area of the focus detection light beam, the more light is projected onto the light receiving sensor, and the focus detection of a low-luminance object can be performed with high accuracy. When this configuration is viewed from the viewpoint of the utilization efficiency of the object light, the focus detection visual field 112-1 at the center of the screen having a large pupil area as a characteristic of the imaging optical system also increases the actual focus detection light flux passing area. On the other hand, as a characteristic of the imaging optical system, in the focus detection field of view 121-4 around the screen where the pupil region is narrow and easily distorted, the actual focus detection beam passage region is also narrow. Therefore, it can be seen that the two requirements of the light quantity at the center of the screen and the arrangement of the focus detection visual field at the periphery of the screen are satisfied well, and the object light is used very efficiently.

  Next, the passage region of the focus detection light beam on the beam splitter 103 will be described. FIG. 22 is a cross-sectional view showing the beam splitter 103 depicting the focus detection light beam and the vicinity thereof.

  In FIG. 22, 170 is a focus detection light beam toward the focus detection field 121-3 of the focus detection sensor 112, 171 is a focus detection light beam toward the focus detection field 121-1, and 172 is a focus detection toward the focus detection field 121-2. Luminous flux. The focus detection light beams 170, 171, and 172 are reflected by the light separation function surface 103a, then totally reflected by the refractive index difference between air and the prism 103-2 on the surface 103-2b, and emitted from the surface 103-2c. In this cross section, since the focus detection light beams 170 and 172 pass through the outermost part of the all focus detection light beams, the focus detection light beams 170 and 172 may be focused on in determining the size of the effective range of each surface.

  Since the beam splitter 103 is a part of the imaging optical system 102, it is advantageous to make the imaging optical system 102 compact by making the thickness as thin as possible. In particular, when the imaging optical system 102 is retracted and accommodated inside the camera body, the larger the air length of the optical surface interval of the imaging optical system 102, the shorter the dimension at the time of accommodation. In order to reduce the thickness T of the beam splitter 103 as much as possible, the setting of the dimension L of the light separation function surface 103a and the dimension D of the surface 103-2c is considered in manufacturing at least to the minimum value that allows the focus detection light beam to pass. A value obtained by adding the power error amount may be used.

  When the thickness T of the beam splitter 103 is set based on such an idea, since the focus detection visual field is located near the center of the imaging range as described with reference to FIG. 10, a part of the imaging light beam is the light separation function surface 103a. You will pass outside.

  FIG. 23 is an explanatory diagram of an actual imaging light beam. In FIG. 23, reference numeral 173 denotes an imaging light beam incident on the upper end of the image sensor 106, 174 denotes an imaging light beam incident on the center of the image sensor 106, and 175 denotes the image sensor 106. Imaging light flux that is incident on the lower end of the image. Since the imaging light beam 174 passes through the light splitting functional surface 103a, the light beam is obtained by multiplying the spectral transmission characteristic of the light splitting functional surface 103a and the spectral intensity characteristic of the object described above with reference to FIG. It becomes light of intensity distribution.

  The imaging light fluxes 173 and 175 pass through the surface 103-1b of the prism 103-1 and the surface 103-2b of the prism 103-2 on which the ND filter is formed, respectively. Therefore, on the emission side of the beam splitter 103, the light has an intensity distribution obtained by the product of the spectral transmission characteristic of the ND filter and the spectral intensity characteristic of the object described above with reference to FIG. The spectral transmittances of the light splitting functional surfaces 103a, 103-1b, and 103-2b have almost no difference in the visible wavelength region. Therefore, when an optical image of a uniform luminance surface is picked up by the light receiving means, an image 180 having a uniform brightness is obtained as shown in FIG. 24, and there is no particular luminance unevenness, and the photographing result is the same as a normal image. It becomes. Temporarily, the surface 103-1b of the prism 103-1 and the surface 103-2b of the prism 103-2 are not formed with ND filters, and have a transmittance close to 100%. Then, the image of the object picked up by the light receiving means becomes an image 184 in which bright regions 182 and 183 are formed above and below the dark region 181 at the center as shown in FIG. It can be said that the effect of adjusting the transmittance using a filter is extremely large.

  FIGS. 26A and 26B are views showing a front surface and an upper surface in which an AF module including a beam splitter 103 and a focus detection sensor 112 as a light beam splitting unit is arranged in the lens barrel 105. FIG.

  26A and 26B, the long holes 201a of the arm portion 201 holding the beam splitter 103 and the flat glass plate 114 are penetrated by four fixing pins 204a provided on the base plate 204 of the lens barrel 105. Yes. Therefore, the arm portion 201 can slide in the left-right direction in FIG. 26B, but the position is regulated with high accuracy in the up-down direction on the paper surface. Further, as can be seen from FIG. 26A, each fixing pin 204a is provided with a biasing spring 204b to bias the arm 201 in the optical axis direction. Therefore, the arm part 201 is supported without backlash in the optical axis direction.

  The back side of the beam splitter 103 of the arm portion 201 is hollowed out, and the imaging light beam forms an image on the imaging element 106 from the subject and the imaging lens through the beam splitter 103. Similarly, the back side of the flat glass 114 of the arm portion 201 is also hollowed out, and when the flat glass 114 is positioned on the surface of the image sensor 106, the imaging light flux forms an image on the image sensor 106 from the subject and the imaging lens through the flat glass 114. To do.

  The base plate 204 is provided with a drive motor 202, and a pinion 202 a of the drive motor 202 is engaged with a rack 201 b provided on the arm portion 201. Therefore, the arm 201, the beam splitter 103, and the flat glass 114 are supported by the rotation of the drive motor 202 so as to be movable in the left-right direction on the paper surface.

  In the position (action position) shown in FIG. 26, the imaging light flux guides the light flux to both the focus detection sensor 112 and the imaging element 106 via the beam splitter 103. FIG. 27 shows a state where the beam splitter 103 is retracted from the imaging light beam (retracted position). Instead, the flat glass 114 is inserted into the imaging light beam, and focus correction is performed due to the absence of the beam splitter 103. .

  As described above, the arm portion 201 is positioned with high accuracy in the vertical direction and the vertical direction (optical axis direction) in FIG. 26 (b) and FIG. 27 (b). However, since the position is determined only by the rotation amount of the drive motor 202 in the left-right direction on the paper surface, the positioning accuracy in this direction is not high.

  As shown in FIG. 23 and the like, the reflection surface of the beam splitter 103 extends in the direction perpendicular to the paper surface. The moving direction of the beam splitter 103 is also aligned in this direction. Therefore, even if the position of the beam splitter 103 is slightly shifted in that direction, the light beam is reflected with high accuracy and is incident on the focus detection sensor 112. For example, in the configuration in which the beam splitter 103 is moved up and down in FIG. 23 so that the beam splitter 103 can be moved to the working position and the retracted position, the position of the light separation function surface 103a (reflective surface) of the beam splitter 103 at the working position is uneven driving. As a result, the sheet may be displaced in the vertical direction in FIG. In this case, since the position of the light beam incident on the focus detection sensor 112 changes, accurate focus detection cannot be performed.

  On the other hand, when the beam splitter 103 is moved in the direction in which the reflecting surface extends (the direction parallel to the focus detection sensor 112) as in the first embodiment, the position of the beam splitter 103 is somewhat as shown in FIG. Since the reflection angle and the reflection position of the reflection surface 103a do not change even if they deviate as indicated by the dotted line 103 ′, the imaging light flux enters the focus detection sensor 112 with high accuracy by the reflection surface 103a. This is because the beam splitter 103 is configured to move in a direction parallel to the focus detection sensor 112 in the plane orthogonal to the optical axis 104 (in FIG. 26, the left-right direction in the drawing). Since the beam splitter 103 is moved perpendicularly to the plane including the light beam incident on and reflected at 103a, driving without deteriorating AF accuracy is possible.

  Further, as shown in FIG. 3A, since the imaging optical system 102 and the focus detection sensor 112 are fixed to the lens barrel 105, the imaging optical system 102 and the focus detection sensor are fixed. The positional relationship of the sensor 112 is maintained with high accuracy. As described with reference to the mechanism of FIG. 26, the beam splitter 103 is held with high accuracy on the left and right sides (in the direction of the imaging optical axis) and on the top and bottom of the page in FIG. However, although a position error occurs due to driving unevenness in the direction perpendicular to the paper surface, even if there is a position error of the beam splitter 103 in this direction, the imaging light flux from the imaging optical system 102 is not affected and focus detection is performed. Therefore, the AF accuracy does not deteriorate.

  FIG. 28 is a flowchart for explaining the operation of the mechanism shown in FIGS. 26 and 27 along the shooting sequence of the camera. This flow starts when the camera is turned on and ends when the power is turned off. In order to avoid complications, this flow omits the operations of elements not directly related to the present invention and the detailed operations at each step (for example, confirmation after operation, standby operation by a timer, etc.).

  In step # 1001, the image sensor 106 is driven to accumulate subject information, and various processes are performed by the RGB processing circuit 131 and the YC processing circuit 132 and are output to the display device 107 so that the subject can be confirmed on the display device 107. To. Further, the brightness of the subject is obtained in the series of processes. Then, by adjusting the aperture in the lens barrel 105 according to the brightness or increasing the gain of the signal of the image sensor 106, a subject with appropriate brightness can be displayed on the display device 107. Yes. This brightness information is used in step # 1008, which will be described later, to determine whether or not the beam splitter 103, which is a beam splitter, needs to be retracted.

  In the next step # 1002, it is determined whether or not the switch S1 to be turned on by pressing the shutter release button 111 in the first stage is turned on. If not, the process returns to step # 1001 and the same operation is repeated. Thereafter, when the switch S1 is turned on, the process proceeds to step # 1003. In step # 1003, the light beam incident on the focus detection sensor 112 through the beam splitter 103 (usually disposed at the (acting position) in the lens barrel 105) is accumulated, and focus detection is performed by the method described above. Do.

  In the next step # 1004, a part or all of the imaging optical system 102 is driven in accordance with the focus detection result to focus on the surface of the image sensor 106. In the subsequent step # 1005, the light flux incident on the focus detection sensor 112 is accumulated again, and the distance to the subject is measured by the method described above to confirm that the focus is achieved. Although it is omitted in the flow, if it is determined that the focus is not sufficient here, the imaging optical system is driven again based on the result to correct the remaining focus and confirm the focus again. Repeat the operation. (If focus cannot be achieved even after performing the above operation a plurality of times, the inability to focus is displayed, the focus operation is stopped, and the process proceeds to step # 1006.

  In step # 1006, it is determined whether the switch S2 is turned on by pressing the shutter release button 111 in the second stage. If not, the process returns to step # 1002, and the same operation is repeated. Thereafter, when the switch S2 is turned on, the process proceeds to step # 1007. In the flow of FIG. 28, the flow does not advance to step # 1006 unless the operation from step # 1003 to step # 1005 is completed. However, the flow is not limited to this, and step ## in a state where the focusing operation is not completed. It may be configured to proceed to 1006 (even in a state where focus is not achieved, the exposure may be advanced by turning on the switch S2).

  In the next step # 1007, it is determined whether or not it is a mode (photographer selection mode) in which it is possible to select whether the beam splitter 103 is positioned in the imaging light beam (operation position) or retracted during exposure according to the photographer's preference. In the case of the selection mode, the process proceeds to step # 1010, and in the case of the automatic selection mode, the process proceeds to step # 1008.

  When the process proceeds to step # 1008 assuming that the mode is the automatic selection mode, it is determined here whether or not the beam splitter 103 is retracted from the imaging light beam during exposure based on the brightness of the subject obtained in step # 1001.

  The beam splitter 103 itself reduces the amount of light incident on the image sensor 106 as described above. For this reason, the beam splitter 103 may be arranged at the operating position in the imaging light beam in the case of a bright subject as in normal shooting, but in the case of a dark subject, the beam splitter 103 is driven to the retracted position. A sufficient amount of subject light is incident on the image sensor 106. Since recent image sensors have increased sensitivity, it is not necessary to retract the beam splitter 103 even if the subject is slightly dark. Conversely, because the sensitivity of the image sensor is high, there are more situations where the subject is bright and the photographing aperture must be narrowed down. Even in such a case, the amount of light can be attenuated by the beam splitter 103, which is a light beam splitting means, so that it is not necessary to stop the photographing aperture, and it is possible to avoid the influence of diffraction and the depth of field due to the aperture being reduced. it can. Some digital cameras adjust the amount of light by putting an ND filter in and out of the imaging light beam as a countermeasure when the subject is bright. However, in the case of the camera of the first embodiment, the ND filter is unnecessary. Furthermore, since the operation of retracting the beam splitter 103 during exposure is unnecessary, the photographing release time lag can be shortened. Further, in the case of an extremely dark subject, the beam splitter 103 is retracted as described above, and sufficient light is guided to the image sensor 106 to suppress the generation of noise.

  If it is determined in step 1008 that it is preferable that the beam splitter 103 be in the retracted position, the process proceeds to step # 1011 described later. If not, the process proceeds to step # 1009 to perform exposure. In this operation, the charge accumulated in the image sensor 106 is reset, and then the accumulated charge is read out by shielding the front surface of the image sensor 106 with a shutter or the like after an accumulation time corresponding to the brightness of the subject. At this time, the image data read simultaneously is recorded on a recording medium. After the exposure is completed, although not shown in this flow, if the switches S1 and S2 are kept on, the process stands by in Step # 1009 and continues to reproduce the captured image on the display device 107 during that time. When the pressing operation of the shutter release button 111 is released (both switches S1 and S2 are off), the shutter is opened again and the process returns to step # 1002.

  If it is determined in step # 1008 that the subject is dark and it is preferable to retract the beam splitter 103 during exposure, the process proceeds to step # 1011 to determine whether the exposure is a still image or a moving image. As a result, in the case of a still image, the process proceeds to step # 1012 and proceeds to a flow for retracting the beam splitter 103. However, in the case of a moving image, the process proceeds to step # 1009, and recording is performed without retracting the beam splitter 103. . This is because in the case of moving images, focus detection and focusing operations may be required during moving image recording.

  In step # 1012, the beam splitter 103 is placed at the retracted position as described above. In the next step # 1013, an exposure operation is performed in the same manner as in step # 1009. After the exposure is completed, although not shown in this flow, when the switches S1 and S2 are kept on, the process waits at step # 1013, and the image taken during that time is continuously reproduced on the display device 107. On the other hand, when the pressing operation of the shutter release button 111 is released, the shutter is opened again, the process proceeds to step # 1014, the beam splitter 103 is disposed at the operating position, and the process returns to step # 1002.

  If the photographer is in the photographer selection mode in which the photographer selects the position of the beam splitter 103 in step # 1007, the operation proceeds to step # 1010, and the operation of placing the beam splitter 103 in the working position or the retracted position. Determine the situation. If the operating position has been selected, the process proceeds to step # 1009 to proceed to the exposure operation, and if the retracted position has been selected, the process proceeds to step # 1012 to perform the retracting operation.

  Here, when the retracted position is selected, the beam splitter 103 is arranged at the retracted position at the time of exposure regardless of whether the image is a still image or a moving image. In this way, it is possible to select whether the beam splitter 103 is positioned on the photographing optical path or retracted during photographing. Therefore, even in a situation where the subject is bright and the photographing aperture needs to be narrowed down, it is not necessary to reduce the photographing aperture due to the light amount attenuation by the beam splitter 103, and the influence of diffraction and the depth of field due to the diaphragm being reduced are reduced. You can avoid getting deep. Further, when the subject is dark, a sufficient amount of light can be guided to the image sensor 106 by retracting the beam splitter 103.

  As described above, in the case of a mechanism in which the beam splitter 103 frequently enters and leaves the imaging light beam, there is a concern that focus detection and focus adjustment errors due to backlash of the mechanism, that is, focusing accuracy may deteriorate. However, as in the first embodiment, the beam splitter 103 is substantially orthogonal to the imaging optical axis (optical axis 104) and is along the reflection surface (light separation function surface 103a), in other words, an incident / reflection optical axis ( By moving in a direction substantially perpendicular to the plane including the optical axis 110) and inserting or retracting the beam splitter 103 with respect to the imaging light beam, focus detection and focus adjustment errors due to the play can be reduced to zero.

  According to the first embodiment, an error when the beam splitter 103 is held at the operating position can be prevented from affecting the focusing accuracy. That is, it is possible to prevent the positional deviation at the operating position of the beam splitter 103 from affecting the focusing accuracy without causing an increase in size.

  FIG. 29 is a front view showing the configuration of the light beam branching unit and the holding unit thereof according to the second embodiment of the present invention. Components having the same functions as those in the first embodiment shown in FIG.

  In FIG. 29, the arm portion 201 that holds the beam splitter 103 and the flat glass plate 114 is pivotally supported around a pin 201 c provided on the base plate 204. The shaft fitting between the pin 201c and the arm portion 201 is managed with high accuracy, and the arm portion 201 does not rattle in the optical axis direction (perpendicular to the paper surface) and the vertical direction on the paper surface. The back side of the beam splitter 103 of the arm part 201 is hollowed out, and the imaging light flux forms an image on the imaging element 106 (not shown) from the subject and imaging lens through the beam splitter 103. Similarly, the back side of the flat glass 114 of the arm portion 201 is also hollowed out, and when the flat glass 114 is positioned on the surface of the image sensor 106, the imaging light flux forms an image on the image sensor 106 through the flat glass 114 from the subject and the imaging lens. To do.

  The ground plane 204 is provided with a flat type drive motor 202, and is driven to rotate in relation to a flat coil 202b provided on the drive motor 202 and a magnet (not shown) opposed thereto. A gear is cut on the outer periphery of the drive motor 202 and meshes with a rack 201 b provided on the arm portion 201. Therefore, the arm part 201, the beam splitter 103, and the flat glass plate 114 can be moved substantially in the left-right direction on the paper surface by the rotation of the drive motor 202. Here, the reason why it is expressed as substantially right and left is that the arm part 201 is actually rotating. However, the position of the beam splitter 103 is far away from the pin 201c, which is the rotation center, and the rotation direction when the beam splitter 103 is positioned in front of the image sensor 106 is almost in the horizontal direction of the paper when viewed from the center of the beam splitter 103. It is.

  In the position (operation position) shown in FIG. 29, the imaging light flux guides the light flux to both the focus detection sensor 112 and the imaging element 106. Then, when the arm portion 201 is driven to rotate and rotates clockwise around the paper surface, the beam splitter 103 is retracted from the imaging light beam, and instead, the flat glass 114 is inserted into the imaging light beam, and the focus correction due to the absence of the beam splitter 103 is performed. Is going.

  In this way, the arm portion 201 is positioned with high accuracy by the pins 201c in the vertical direction and the vertical direction (optical axis direction) in FIG. However, since the position is determined only by the rotation amount of the drive motor 202 in the left-right direction on the paper surface, the positioning accuracy in this direction is not high. However, the reflection surface (light separation function surface 103a) of the beam splitter 103 extends right and left on the paper surface. The moving direction of the beam splitter 103 is also aligned in this direction. Therefore, even if the position of the beam splitter 103 is slightly shifted in that direction (see the dotted line 103 ′), the light beam is reflected with high accuracy without being affected by the deviation and is incident on the focus detection sensor 112.

  That is, when the beam splitter 103 is moved in the direction in which the reflecting surface extends (the direction parallel to the focus detection sensor 112) as in the second embodiment, the position of the beam splitter 103 is somewhat dotted as shown in FIG. Even if it deviates like 103 ', the reflection angle and reflection position of the light separation function surface 103a do not change. Therefore, the imaging light beam enters the focus detection sensor 112 with high accuracy by the light separation function surface 103a which is a reflection surface. This is because the beam splitter 103 is configured to move in a direction parallel to the focus detection sensor 112 in the plane orthogonal to the optical axis 104 (the left-right direction in FIG. 29). In other words, since the beam splitter 103 is moved perpendicularly to the plane including the light flux that enters and reflects on the reflecting surface, it is possible to drive without degrading the focusing accuracy.

  According to the second embodiment, the error when the beam splitter 103 is held at the operating position can be prevented from affecting the focusing accuracy. That is, it is possible to prevent the positional deviation at the operating position of the beam splitter 103 from affecting the focusing accuracy without causing an increase in size.

  FIG. 30A is a side cross-sectional view of the lens barrel 105 portion of the digital camera 101 according to the third embodiment of the present invention in a preparation state for shooting, and FIG. It is an upper surface sectional view in a state. Components having the same functions as those in the first embodiment shown in FIG.

  The beam splitter 103 according to the third embodiment of the present invention is a simple 45-degree reflection mirror, and is disposed between the focusing lens 102a and the image sensor 106, which are components of the imaging optical system 102. The focusing lens 102a moves in the direction of the optical axis 104 to adjust the focus.

  The image sensor 106 is positioned with respect to a fixed ground plate (not shown) of the lens barrel 105. The light flux in the central focus detection area of the imaging light flux is bent at a right angle by the beam splitter 103 which is a 45-degree reflection mirror, and almost 100% is incident on the focus detection sensor 112.

  A schematic imaging sequence is as follows. When it is detected that the shutter release button 111 has been pressed in the first stage, the beam splitter 103 is inserted into the imaging light beam (the states of FIGS. 30A and 30B). Next, focus detection is performed using the focus detection sensor 112 by the light beam reflected by the beam splitter 103. When the focus detection is completed, the beam splitter 103 is retracted out of the imaging light beam (in the direction of arrow 103y in FIG. 30B).

  Next, the image sensor 106 is driven, and an object image is repeatedly imaged with a light beam transmitted through the imaging optical system 102, and the object image is displayed on the display device 107 in real time. When a defocus amount 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. After the focus adjustment is completed, the beam splitter 103 is inserted into the imaging light beam again, the focus detection is performed by the focus detection sensor 112, and when it is confirmed that the defocus amount is within a predetermined range, a focus display by sound or light is performed. Put out. During this time, real-time display by the display device 107 is not performed, and the display of the image immediately before the beam splitter 103 is inserted is continued, and the operation for inserting the beam splitter 103 into the display device 107 is not displayed.

  The beam splitter 103 is retracted again, the image sensor 106 is driven, the object image is repeatedly imaged by the light beam transmitted through the imaging optical system 102, and the object image is displayed on the display device 107 in real time. Thereafter, the focus may be reconfirmed by performing a known hill-climbing AF, or the focus detection may be omitted after the focus adjustment is completed, and the hill-climbing AF may be used to finely adjust the focus.

  When it is detected that the shutter release button 111 has been pressed in the second stage, the image sensor 106 is driven to perform imaging in the high definition mode. Then, the image data relating to the captured object image is written in the memory, and the process returns to the first operation.

  As described above, in the third embodiment, the beam splitter 103 is inserted into the imaging light beam only when the shutter release button 111 is pressed in the first stage (during focus adjustment). Since the beam splitter 103 is a reflecting mirror, it is impossible to capture an image when it is positioned in front of the image sensor 106. However, only when the beam splitter 103 is inserted, the capturing of the image is stopped and the display screen is frozen. Accordingly, the beam splitter 103 becomes smaller and lighter, and the flat glass 114 for focus correction becomes unnecessary, so that the driving time for inserting and retracting the beam splitter 103 into the imaging light beam can be extremely shortened. Therefore, the screen freeze time at normal brightness (the insertion time of the beam splitter 103, the accumulation time of the focus detection sensor 112, and the retraction time of the beam splitter 103) is about 1/15 seconds, and the image display repetition rate is 1 There is no big difference with / 30 (1 or 2 freezes). Therefore, the screen freeze for distance measurement is hardly a problem.

  FIG. 31 is a front view showing the configuration of the light beam branching means and its holding means according to the third embodiment of the present invention. Components having the same functions as those in the first embodiment shown in FIG.

  In FIG. 31, the arm part 201 holding the beam splitter 103 is slidably supported by a bearing part 201d on a sliding shaft 203 whose end part 203a is supported by a base plate 204. The shaft fitting between the sliding shaft 203 and the arm portion 201 is managed with high accuracy, and the arm portion 201 does not rattle in the optical axis direction (perpendicular to the paper surface) and the vertical direction on the paper surface.

  The base plate 204 is provided with a drive motor 202, and a pinion 202 a meshes with a rack 201 b provided on the arm portion 201. Therefore, the arm 201 and the beam splitter 103 can move in the left-right direction on the paper surface by the rotation of the drive motor 202.

  At the position (action position) shown in FIG. 31, the imaging light flux is guided to the focus detection sensor 112. When the arm portion 201 is moved in the left-right direction by the drive motor 202, the beam splitter 103 is retracted from the imaging light beam.

  As described above, the arm portion 201 is positioned with high accuracy by the bearing portion 201d in the vertical direction and the vertical direction (optical axis direction) in FIG. 31, but the rotation amount of the drive motor 202 is determined in the horizontal direction on the paper surface. Since the position is determined only by this, the positioning accuracy in this direction is not high. However, the reflecting surface of the beam splitter 103 extends to the left and right of the page. The moving direction of the beam splitter 103 is also aligned in this direction. Therefore, even if the position of the beam splitter 103 is slightly deviated in that direction, the light beam is reflected with high accuracy without being affected by the deviation and is incident on the focus detection sensor 112.

  Therefore, the error when the beam splitter 103 is held at the operating position can be prevented from affecting the focusing accuracy. That is, it is possible to prevent the positional deviation at the operating position of the beam splitter 103 from affecting the focusing accuracy without causing an increase in size.

  FIG. 32 is a front view showing the configuration of the light beam branching unit and its holding unit of the digital camera according to Embodiment 4 of the present invention. Components having the same functions as those in the first embodiment shown in FIG. The configuration and operation in the digital camera are the same as those in the third embodiment shown in FIG.

  In FIG. 32, the arm portion 201 that holds the beam splitter 103 is slidably supported by a bearing portion 201d on a pair of sliding shafts 203 supported by an end portion 203a on a base plate 204. Of the pair of sliding shafts 203, the shaft fitting between one sliding shaft 203 and the arm portion 201 is managed with high accuracy, and the arm portion 201 is in the optical axis direction (the vertical direction on the paper surface) and in the vertical direction on the paper surface. There is no rattling. The other sliding shaft 203 is used as a rotation stop around the one sliding shaft 203 of the arm 203.

  The base plate 204 is provided with a flat coil 205, which drives the arm portion 201 in the left-right direction on the paper surface in relation to the permanent magnet 206 provided on the arm portion 201. A position detection element 209 such as a hall element is provided at the center of the coil 205 to detect the position of the arm 201 (permanent magnet 206). Based on the detection result, the driving of the focus detection sensor 112 or the driving of the image sensor 106 is controlled.

  At the position (action position) shown in FIG. 32, the imaging light flux is guided to the focus detection sensor 112. Even in this state, a current is applied to the coil 205 to bias the arm portion 201 in the direction of the operating position, and the beam splitter 103 is not shifted to the retracted position due to disturbance vibration or the like. When the coil 205 is energized, the beam splitter 103 is retracted from the imaging light beam. Even if the beam splitter 103 is retracted from the imaging light beam, a weak current continues to flow through the coil 205 so that the beam splitter 103 does not enter the imaging light beam due to disturbance. This is not a continuous application of a weak current, but a spring that always biases the beam splitter 103 out of the imaging light beam may be provided.

  As described above, the arm portion 201 is positioned with high precision by the bearing portion 201d in the vertical direction and the vertical direction (optical axis direction) of FIG. 32, but only the biasing force of the coil current is provided in the horizontal direction of the paper. Since the position is determined by this, the positioning accuracy in this direction is not high. However, the reflecting surface of the beam splitter 103 extends to the left and right of the page. The moving direction of the beam splitter 103 is also aligned in this direction. Therefore, even if the position of the beam splitter 103 is slightly deviated in that direction, the light beam is reflected with high accuracy without being affected by the deviation and is incident on the focus detection sensor 112.

  Therefore, the error when the beam splitter 103 is held at the operating position can be prevented from affecting the focusing accuracy. That is, it is possible to prevent the positional deviation at the operating position of the beam splitter 103 from affecting the focusing accuracy without causing an increase in size.

  FIG. 33 is a front view showing the configuration of the light beam branching means and its holding means of the digital camera according to Embodiment 5 of the present invention. Components having the same functions as those in the first embodiment shown in FIG. The configuration and operation in the digital camera are the same as those in the third embodiment shown in FIG.

  In FIG. 33, the arm portion 201 that holds the beam splitter 103 is pivotally supported around a pin 201 c provided on the main plate 204. The shaft fitting between the pin 201c and the arm portion 201 is managed with high accuracy, and the arm portion 201 does not rattle in the optical axis direction (perpendicular to the paper surface) and the vertical direction on the paper surface.

  The arm part 201 is provided with a flat coil 205, which drives the arm part 201 in a substantially horizontal direction on the paper surface in relation to the permanent magnet 206 provided on the base plate 204. Here, the reason why it is expressed as “substantially left and right” is that the arm part 201 actually rotates. However, the position of the beam splitter 103 is far away from the pin 201c, which is the rotation center, and the rotation direction when the beam splitter 103 is positioned on the front surface of the image sensor 106 is almost in the horizontal direction of the paper when viewed from the center of the beam splitter 103. is there.

  At the position (action position) shown in FIG. 33, the imaging light flux is guided to the focus detection sensor 112. Even in this state, a current is applied to the coil 205 to bias the arm portion 201 in the direction of the operating position, and the beam splitter 103 is not shifted to the retracted position due to disturbance vibration or the like. When the coil 205 is energized, the beam splitter 103 is retracted from the imaging light flux. Even if the beam splitter 103 is retracted from the imaging light beam, a weak current continues to flow through the coil 205 so that the beam splitter does not enter the imaging light beam due to disturbance. This is not a continuous application of a weak current, but a spring that always biases the beam splitter 103 out of the imaging light beam may be provided.

  As described above, the arm portion 201 is positioned with high accuracy by the pin 201c in the vertical direction and vertical direction (optical axis direction) in FIG. 33, but only in the horizontal direction on the paper surface by the biasing force of the coil current. Since the position is determined, the positioning accuracy in this direction is not high. However, the reflecting surface of the beam splitter 103 extends to the left and right of the page. The moving direction of the beam splitter 103 is also aligned in this direction. Therefore, even if the position of the beam splitter 103 is slightly deviated in that direction, the light beam is reflected with high accuracy without being affected by the deviation and is incident on the focus detection sensor 112.

  Therefore, the error when the beam splitter 103 is held at the operating position can be prevented from affecting the focusing accuracy. That is, it is possible to prevent the positional deviation at the operating position of the beam splitter 103 from affecting the focusing accuracy without causing an increase in size.

  The retracting structure of the beam splitter 103 in the first to fifth embodiments is not limited to the optical system disclosed in FIGS. 1A and 1B, but also in a bending optical system that has been actively employed in digital cameras recently. Applicable. This will be described below as a sixth embodiment of the present invention.

  FIG. 34 is a diagram in which mainly the bending optical system 207 is extracted from the digital camera according to Embodiment 6 of the present invention, and a high-magnification zoom optical system of four groups is formed as a whole.

  In FIG. 34, a first lens group is constituted by a front lens 207f, a mirror 207c, and a bonded lens group 207j, and a second lens group 207k that moves along the main optical axis 207a for zooming and a third lens that is always fixed. The bending optical system is constituted by the group 207l and the fourth group 207m that moves along the main optical axis 207a for focus adjustment. A beam splitter 103 is provided between the fourth group 207m and the image sensor 106. When the beam splitter 103 is retracted, the beam splitter 103 moves in the direction perpendicular to the paper surface (the direction along the reflection surface). Note that the holding means of the sixth embodiment may have any configuration of the first to fifth embodiments.

  35A is a top view of the digital camera 208 equipped with the bending optical system described in FIG. 34, and FIG. 35B is a front view thereof.

  The mirror 207c of the bending optical system aligns the longitudinal direction of the digital camera 208 in the direction along the reflection surface (the vertical direction in FIG. 34 and the horizontal direction in FIGS. 35A and 35B). The entire body of the camera 208 is reduced in thickness. Then, as shown in FIG. 35A, the beam splitter 103 is arranged to move the operating position and the retracted position along the longitudinal direction of the digital camera 208. This is because the focusing accuracy can be improved by moving the beam splitter 103 in the direction along the reflecting surface as described in the first to fifth embodiments. Also, as can be seen from FIGS. 35A and 35B, since the moving direction is along the longitudinal direction of the digital camera 208, it is not necessary to increase the thickness of the digital camera 208 in order to retract the beam splitter 103. . This is because the vacant space in the longitudinal direction of the digital camera 208 can be used effectively.

  According to the sixth embodiment, an error when the beam splitter 103 is held at the operating position can be prevented from affecting the focusing accuracy. That is, it is possible to prevent the positional deviation at the operating position of the beam splitter 103 from affecting the focusing accuracy without causing an increase in size.

  In the above first to sixth embodiments, the description has been continued by taking the digital camera as an example. However, the present invention is not limited to the digital camera, and may be configured as a focusing device. Furthermore, it can also be developed for a video camera, a surveillance camera, a Web camera, a mobile phone having an imaging function, and the like.

It is sectional drawing which shows the principal part structure of the digital camera concerning Example 1 of this invention. It is a block diagram which shows the electric constitution of the digital camera of FIG. FIG. 2 is a configuration diagram of a lens barrel portion at a beam splitter operating position in the digital camera of FIG. FIG. 2 is a configuration diagram of a lens barrel portion at a beam splitter retracted position in the digital camera of FIG. 1. It is sectional drawing of the beam splitter shown in FIG. It is a perspective view of the beam splitter shown in FIG. It is a disassembled perspective view of the beam splitter shown in FIG. It is a figure which shows the optical characteristic of the light splitting functional surface of the beam splitter shown in FIG. It is a figure which shows the example of the optical characteristic of the general ND filter used for a digital camera. It is a focus detection visual field figure by AF module concerning Example 1 of the present invention. It is a top view which shows the focus detection surface of the AF module concerning Example 1 of this invention. Sectional drawing of the pixel part of the image pick-up element concerning Example 1 of this invention. It is a top view which shows the photoelectric conversion part of 1 pixel of the image pick-up element concerning Example 1 of this invention. It is a top view showing the state which connected each pixel of the image pick-up element concerning Example 1 of this invention, and made it the pixel row | line | column for using for a focus detection. It is a perspective view showing the state which connected each pixel of the image pick-up element concerning Example 1 of this invention, and was used as the pixel row | line | column for using for a focus detection. FIG. 16 is a plan view showing openings 154A and 154B in the first wiring layer 154 of FIG. 15. It is a fragmentary sectional view of focus detection visual field 112-1 concerning Example 1 of the present invention. It is a fragmentary sectional view of focus detection visual field 112-1 concerning Example 1 of the present invention. It is a figure which shows the output signal waveform of the sensor for focus detection input into AF control circuit 140 of FIG. It is a figure which shows the output signal waveform of the sensor for focus detection input into AF control circuit 140 of FIG. It is a figure for demonstrating the passage area | region of the focus detection light beam on the exit pupil of the imaging optical system of FIG. It is explanatory drawing of the imaging light beam concerning Example 1 of this invention. It is sectional drawing of the beam splitter periphery which drawn the focus detection light beam concerning Example 1 of this invention. It is a figure which shows the generation | occurrence | production degree of the brightness nonuniformity on an image in Example 1 of this invention. It is a figure which shows the generation | occurrence | production degree of the brightness nonuniformity on an image in Example 1 of this invention. It is a figure which shows the front and side of a light beam branching means and its holding means etc. in an action position in Example 1 of this invention. It is a figure which shows the front and side of a light beam branching means in the retracted position and its holding means etc. in Example 1 of this invention. It is a flowchart which shows the imaging | photography sequence in Example 1 of this invention. It is a front view of the light beam branching means at the operation position and the holding means thereof in the digital camera according to the second embodiment of the present invention. It is sectional drawing in the beam splitter action position of the lens-barrel part in the digital camera concerning Example 3 of this invention. It is a figure which shows the front of the light beam splitting means in the action position in the digital camera concerning Example 3 of this invention, its holding means, etc. It is a figure which shows the front of the light beam branching means in the action position in Example 4 of this invention, and its holding means. It is a figure which shows the front of the light beam branching means in the action position in Example 5 of this invention, and its holding means. FIG. 10 is a diagram illustrating a layout of a bending optical system in a digital camera according to Example 6 of the present invention. It is sectional drawing of the digital camera which included the bending optical system of FIG.

Explanation of symbols

102 Imaging Optical System 103 Beam Splitter (Flux Splitting Unit)
106 Image sensor (imaging surface)
112 Focus detection sensor (light receiving means)
113 Low-pass filter 114 Flat glass 201 Arm (part of holding means)
202 Driving coil (part of holding means)
204 Ground plate (part of holding means)
205 coil (part of holding means)
206 Permanent magnet (part of holding means)
207 Refractive optical system

Claims (5)

A light beam branching unit that is disposed between a lens that forms an image of a subject light beam on an imaging surface and the imaging surface, and includes a reflecting surface that separates the subject light beam outside the imaging optical path;
A light receiving means for receiving a subject light beam separated by the light beam branching means to obtain a signal for adjusting the focus of the lens;
Holding means for holding the light beam branching means at any one of an action position to be positioned in the imaging optical path and a retraction position to be retracted from the imaging optical path;
Have
The focusing device is characterized in that the holding means holds the light beam branching means so as to be movable in a direction substantially parallel to the light receiving means within a plane orthogonal to the imaging optical axis. A light beam branching unit provided between a lens that forms an image of a subject light beam on the imaging surface and the imaging surface, and a reflecting surface that reflects the incident subject light beam outside the imaging optical path;
A light receiving means for receiving a subject light beam reflected by the light beam branching means and obtaining a signal for adjusting the focus of the lens;
Holding means for holding the light beam branching means at any one of an action position to be positioned in the imaging optical path and a retraction position to be retracted from the imaging optical path;
Have
The focusing device is characterized in that the holding means holds the light beam branching means so as to be movable in a direction substantially perpendicular to a plane including the incident / reflected optical axis. A light beam branching unit provided between a bending optical system that reflects a subject light beam to form an image on an imaging surface and a reflecting surface that separates the subject light beam from the imaging optical path; and
A light receiving means for receiving a subject light beam separated by the light beam branching means to obtain a signal for adjusting the focus of the lens;
Holding means for holding the light beam branching means at any one of an action position to be positioned in the imaging optical path and a retraction position to be retracted from the imaging optical path;
Have
The focusing device is characterized in that the holding means holds the light beam branching means so as to be movable in a direction substantially parallel to the light receiving means within a plane orthogonal to the imaging optical axis. A light beam branching unit provided between a bending optical system that reflects a subject light beam and forms an image on an imaging surface and a reflecting surface that reflects an incident subject light beam outside the imaging optical path; and
A light receiving means for receiving a subject light beam reflected by the light beam branching means and obtaining a signal for adjusting the focus of the lens;
Holding means for holding the light beam branching means at any one of an action position to be positioned in the imaging optical path and a retraction position to be retracted from the imaging optical path;
Have
The focusing device is characterized in that the holding means holds the light beam branching means so as to be movable in a direction substantially perpendicular to a plane including the incident / reflected optical axis. An imaging apparatus comprising the focusing device according to claim 1.

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