JP4007713B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus that has a focus adjustment function and that performs imaging using an electronic imaging element.
[0002]
[Prior art]
Conventionally, various techniques relating to an imaging apparatus that electronically captures a subject image using an electronic imaging element have been disclosed.
[0003]
For example, Japanese Patent Laid-Open No. 10-213737 discloses a technique related to an imaging apparatus that employs a so-called “mountain climbing method” as an autofocus (hereinafter referred to as AF) method. This hill-climbing method is a method of searching for a photographing lens position where the contrast of a subject image captured by an image sensor is maximized.
[0004]
Japanese Patent Application Laid-Open No. 10-197783 discloses a technique related to an imaging apparatus that employs a TTL phase difference detection method. In such a TTL phase difference detection method, a diaphragm member is driven to perform pupil division in a time division manner, and a light flux that has passed through the pupil is received by an imaging element to perform phase difference detection.
[0005]
On the other hand, Japanese Patent Publication No. 57-49841 discloses a technique related to a TTL phase difference detection device. This is a method called the fly lens method. The light beam that has passed through the lens array is received by a pair of light receiving elements that form a line sensor, and the signal from the line sensor is processed to calculate the image shift amount, that is, the phase difference amount. Then, the focus adjustment is performed by feeding back to the amount of extension of the focus sync lens.
[0006]
Japanese Patent Application Laid-Open No. 10-274562 discloses a technique related to a TTL phase difference detection apparatus that employs a re-imaging method. On the other hand, Japanese Patent Application Laid-Open No. 8-201683 discloses a technique related to a re-imaging type TTL phase difference detection apparatus having a plurality of focus detection areas.
[0007]
[Problems to be solved by the invention]
However, the hill-climbing method has a problem that the AF speed is slow because the photographing lens is moved to search for the contrast peak of the subject image of the image sensor.
[0008]
In the technique disclosed in Japanese Patent Laid-Open No. 10-197783, a diaphragm member is driven by a mechanical mechanism to perform pupil division. Therefore, a driving mechanism is required, and it is difficult to reduce the size because a mounting space is required. is there. Furthermore, since a time difference occurs in the formation of a plurality of divided pupils to be divided, there is a problem that detection accuracy is greatly deteriorated for a moving subject. Further, it takes time to move the mechanical aperture member, and the AF speed becomes slow.
[0009]
On the other hand, in the focus detection device disclosed in the above Japanese Patent Publication No. 57-49841, a part of the light beam from the subject that has passed through the photographing lens has to be divided and guided, so that there are optical restrictions and space restrictions. The problem of receiving occurs.
[0010]
Further, the focus detection apparatus disclosed in the above Japanese Patent Laid-Open No. 10-274562 has a problem that a re-imaging optical system is required in addition to the above-described problem of optical path division, and further, space restrictions are increased. ing.
[0011]
The focus detection apparatus disclosed in the above Japanese Patent Laid-Open No. 8-201683 requires a re-imaging optical system and an AF sensor for each of the plurality of focus detection areas, thereby further increasing the cost and increasing the space. Will be invited.
[0012]
The present invention has been made in view of the above problems, and the object of the present invention is to provide a low-cost and space-saving, wider focus detection area without adding a new mechanism or optical system, and an AF An object of the present invention is to provide an imaging apparatus having a focus adjustment function capable of improving speed and performing accurate focus adjustment.
[0013]
[Means for Solving the Problems]
  In order to achieve the above object, according to a first aspect of the present invention, in an imaging apparatus having an imaging element that receives subject image light that has passed through a photographing lens,The image sensorReceiving subject image light passing through the taking lensIn addition, a color filter arranged according to a predetermined rule is arranged on the front surfaceA first light receiving element group, a first microlens group for condensing subject image light on the first light receiving element group,WithAn imaging area for generating an output of the first light receiving element group for imaging, a second microlens group for pupil-dividing a luminous flux of subject image light passing through the photographing lens, and the second microlens Receiving each luminous flux divided by pupilsIn addition, a color filter arranged according to a predetermined rule is arranged on the front surfaceA pair of second light receiving element groupsAnd comprisingA focus detection area for generating outputs of the pair of light receiving element groups to perform focus detection;A focus detection unit that performs focus detection based on the output of the focus detection region unit, an image creation unit that generates a captured image based on the output of the imaging region unit,ComprisingThe focus detection unit performs focus detection based on outputs of the pair of light receiving element groups in which color filters of the same color in the focus detection region unit are arranged.Is provided.
[0014]
  And in the second aspect, in the first aspect,The focus detection unit performs focus detection for each of a plurality of different color filters based on outputs of the pair of light receiving element groups in which the color filters of the same color are arranged, and outputs a plurality of focus detection results corresponding to the different color filters. Use the average value as the focus detection resultAn imaging device is provided.
[0015]
  Furthermore, in the third aspect, in the first aspect,The focus detection unit performs focus detection for each of a plurality of different color filters based on outputs of the pair of light receiving element groups in which the color filters of the same color are arranged, and outputs a plurality of focus detection results corresponding to the different color filters. Select a focus detection result with higher reliabilityAn imaging device is provided.
[0016]
According to the 1st thru | or 3rd aspect, the following effects are show | played.
[0017]
  That is, in the first aspect of the present invention, in an imaging apparatus having an imaging element that receives subject image light that has passed through a photographing lens,In the imaging device, color filters are arranged and arranged on the front surface according to a predetermined rule, and subject image light passing through the photographing lens is received by the first light receiving element group, and the first minute lens group receives the first micro lens group. Subject image light is focused on the light receiving element group, and an output of the first light receiving element group is generated by the imaging region unit for imaging. Further, in the focus detection area portion, the second minute lens group splits the luminous flux of the subject image light passing through the photographing lens into a pupil, and a pair of color filters arranged in accordance with a predetermined rule are arranged on the front surface thereof. The second light receiving element group receives the light beams divided by the second minute lens group, and outputs the pair of light receiving element groups for focus detection. Further, the focus detection unit performs focus detection based on the output of the focus detection region unit, and the image generation unit generates a captured image based on the output of the imaging region unit. Then, the focus detection unit performs focus detection based on outputs of the pair of light receiving element groups in which the color filters of the same color in the focus detection region unit are arranged.
[0018]
  And in the second aspect, in the first aspect,The focus detection unit performs focus detection for each of a plurality of different color filters based on the output of the pair of light receiving element groups in which the same color filters are arranged, and a plurality of focus detection results corresponding to the different color filters. Is used as the focus detection result.
  Furthermore, in the third aspect,The focus detection unit performs focus detection for each of a plurality of different color filters based on the output of the pair of light receiving element groups in which the same color filters are arranged, and a plurality of focus detection results corresponding to the different color filters. Among them, a focus detection result with higher reliability is selected.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0020]
FIG. 1 is a configuration diagram of an optical system of the imaging apparatus according to the first embodiment of the present invention.
[0021]
As shown in the figure, a focusing lens 1a for receiving incident light is disposed at a predetermined position, and a diaphragm 2 is disposed on the optical axis thereof. The photographing optical system 1 is constituted by the focusing lens 1a, the diaphragm 2, and the like. A beam splitter 3 is disposed on the optical path of the subject light via the photographing optical system 1, and an infrared cut filter 4 and a low-pass filter (hereinafter, referred to as “light cut-off filter 4”) are disposed on the optical path of the light reflected by the beam splitter 3. (Referred to as LPF) 5 and an image sensor 6 are provided.
[0022]
On the other hand, a finder optical system 10 including a mirror 7, a pentaprism 8, and an eyepiece lens 9 is provided on the optical path of the light transmitted through the beam splitter 3.
[0023]
The diaphragm 2 can hold a predetermined diaphragm aperture, has a shutter function, and also has a function of completely shielding light.
[0024]
In such a configuration, part of the subject luminous flux that has passed through the photographing optical system 1 is reflected downward by the beam splitter 3, the infrared light component is removed by the infrared light cut filter 4, and moire is reduced by the LPF 5. After that, an image is picked up by the image sensor 6. A part of the subject luminous flux that has passed through the beam splitter 3 is reflected by the mirror 7 and then guided to a finder optical system 10 including a pendant prism 8 and an eyepiece 9 and is observed by a photographer.
[0025]
Next, FIG. 2 is a configuration diagram of an electric system of the imaging apparatus according to the first embodiment.
[0026]
As shown in the figure, a microcomputer 31 includes a central processing unit (hereinafter referred to as a CPU) 31a that controls the whole, a read only memory (hereinafter referred to as a ROM) 31b, a random access memory (hereinafter referred to as a RAM). 31c), an analog / digital converter (hereinafter referred to as ADC) 31d, and an EEPROM 31e which is a non-volatile memory.
[0027]
Further, the microcomputer 31 includes a lens driving unit 32, an aperture driving unit 33, an image sensor control unit 43, a display unit 46, a first release switch (hereinafter referred to as 1RSW) 47, and a second release switch (hereinafter referred to as 2RSW) 48. The area selection SW 49 is electrically connected.
[0028]
The output of the image sensor control unit 43 is connected to the input of the image sensor 16 (same as the image sensor 6 in FIG. 1), and the output of the image sensor 16 is connected to the input of the video signal processor 42. Yes. The output of the video signal processing unit 42 is connected to the inputs of the recording unit 44, photometry / exposure calculation unit 45, display unit 46, focus detection calculation unit 50, and auto white balance (hereinafter referred to as AWB) unit 51, respectively. Has been.
[0029]
The output of the photometry / exposure calculation unit 45 and the output of the focus detection calculation unit 50 are connected to the input of the microcomputer 31.
[0030]
In such a configuration, the microcomputer 31 performs a series of operations in accordance with a sequence program stored in the internal ROM 31b. The EEPROM 31e inside the microcomputer 31 stores correction data for focus adjustment, photometry / exposure calculation, AWB, and the like for each camera. The image sensor 6 captures a subject image formed by the photographing optical system 1 and converts it into an electrical signal.
[0031]
The video signal processing unit 42 processes an electrical signal that is a pixel signal from the image sensor 6 to create a video signal. The detailed configuration will be described later.
[0032]
The photometric / exposure calculating unit 45 calculates a photometric value and an exposure control value based on the video signal processed by the video signal processing unit 42. Further, the image sensor control unit 43 controls the electronic shutter of the image sensor 6 at the time of shooting based on the shutter speed that is the output of the photometry / exposure calculation unit 45. In this embodiment, based on the aperture value data calculated by the exposure calculation of the photometry / exposure calculation unit 45, the diaphragm 2 in the photographing optical system 1 is controlled at the time of shooting.
[0033]
The diaphragm drive unit 33 drives the diaphragm 2 based on a command from the microcomputer 31. Further, the focus detection calculation unit 50 performs focus detection calculation based on the video signal processed by the video signal processing unit 42. As a result of the focus detection calculation, in-focus determination data, a focus sync lens driving amount, and the like are transmitted to the microcomputer 31.
[0034]
The AWB unit 51 automatically controls white balance based on the video signal processed by the video signal processing unit 42. Under the control of the microcomputer 31, the display unit 46 displays images captured by the image sensor 6 and information inside the camera on a liquid crystal display (LCD) or the like.
[0035]
1RSW47 and 2RSW48 are switches linked to the release button. When the release button is depressed in the first stage, 1RSW47 is turned on. Subsequently, when the second stage is depressed, 2RSW48 is turned on. The area selection SW 49 is a switch for selecting an AF area, and moves and selects a predetermined AF area each time it is turned on. The microcomputer 31 performs photometry and AF operations when 1RSW 47 is on, and performs an exposure operation and an image recording operation when 2RSW 48 is on.
[0036]
In addition to the above, the lens driving unit 32 drives the focus sync lens 1 a based on a command from the microcomputer 31.
[0037]
Here, FIG. 3 is a diagram showing a detailed configuration of the image sensor 6.
[0038]
As shown in the figure, in the imaging element 6 as a MOS type sensor, a plurality of pixel units 110 each including a photodiode as a light receiving element are two-dimensionally arranged, and the control unit 111 performs an accumulation operation of each pixel unit 110. Is configured to be controlled. The control unit 111 controls the X shift register 112 and the Y shift register 113 to select the output Sn of the pixel unit as switches SWxn and SWyn, and outputs them to the outside by the output unit 114.
[0039]
Further, in FIG. 4C, the image pickup device 6 is functionally divided into two parts for explanation. As shown in the figure, the image pickup device 6 includes an image pickup unit 100 for using a pixel signal for photographing and a focus detection unit 200 for using the pixel signal for focus detection. The imaging unit 100 is formed on substantially the entire surface, and the focus detection unit 200 is formed on a part thereof. Further, on the photographing screen 120, the focus detection area 200A is arranged on the optical axis, and the focus detection area 200B is arranged outside the optical axis and in a direction perpendicular to the focus detection area 200A.
[0040]
On the other hand, a microlens is formed on the front surface of the photodiode as the light receiving element. As a technique for improving the photosensitivity of the image sensor, a so-called on-chip microlens technique has been established in which a microlens is provided at a position corresponding to each photodiode to efficiently collect incident light on the light receiving portion. ing. In the imaging unit 100, the microlens is set to optimize the light sensitivity as described above.
[0041]
FIG. 4A is a diagram showing an arrangement of photodiodes as light receiving elements on the image sensor 16. In the focus detection units 200A to 200C, a plurality of units of a pair of photodiodes 201a and 201b are arranged. A photodiode 101 is arranged in the imaging unit 100.
[0042]
FIG. 4B is a diagram showing the arrangement of photodiodes and microlenses.
[0043]
In the focus detection units 200 </ b> A to 200 </ b> C, the microlens 206 is disposed for the pair of photodiodes 201 a and 201 b, and in the imaging unit 100, the microlens 106 is disposed for the photodiode 101.
[0044]
Next, FIG. 5 is a diagram showing a general cross-sectional configuration of an image pickup element in which an on-chip microlens is formed. Note that the imaging unit 100 of the imaging device 6 in the imaging apparatus according to the present embodiment has a configuration substantially similar to that shown in FIG.
[0045]
As shown in FIG. 5, in a semiconductor substrate 131 made of silicon, a photodiode constituting the light receiving portion 133 is formed by a diffusion layer or the like.
[0046]
Further, the circuit portion 132, the gate electrode 134, and the like that constitute a circuit for amplifying the output of the photodiode are covered with a light shielding film 135. Further, the light receiving portion 133 is formed corresponding to the opening of the light shielding film 135, and a color filter 137 is formed on the light receiving portion 133 and the light shielding film 135. Further, on the color filter 137, a micro lens 139 having a predetermined curvature r and a spherical surface having a focal length f1 is formed.
[0047]
On the other hand, the microlens 206 corresponding to the focus detection unit 200 is different from the microlens 106 (139) of the imaging unit 100 in characteristics such as curvature and focal length, and a pair of light receiving elements substantially on the focal plane of the microlens 206. The photodiodes A and B are arranged. Then, as shown in FIG. 6, the microlens 206 divides the light beam passing through the photographing optical system 11 into pupils and acts so that the divided light beams are incident on the pair of light receiving elements A and B, respectively.
[0048]
The focus detection principle is the same as the phase difference detection method disclosed in the above-mentioned Japanese Patent Publication No. 57-49841, and a detailed description thereof is omitted here.
[0049]
Next, FIG. 7 shows and describes examples of focusing, front pins, and rear pins in the focus detection unit 200. Actually, the microlens Ln group and the light receiving elements An and Bn group are fixed and the position of the photographing optical system 1 moves. Here, for convenience of explanation, the position of the photographing optical system 1 is changed. The relative positional relationship will be described as fixed.
[0050]
The focal length of the microlens Ln is f2, which is substantially equal to the distance between the microlens Ln and the light receiving element photodiodes An and Bn.
[0051]
First, at the time of focusing, light rays R1, R2, R3, R4,..., Which are light east from the same subject and have passed through different exit pupils, are received by adjacent An and Bn around the optical axis of each microlens Ln. The amount of received light matches. For example, the microlens L2 and the light receiving elements A2 and B2 correspond to the light beams R3 and R4.
[0052]
In the case of the front pin, the amounts of light received by the light receiving elements A and B through different microlenses, that is, the amounts of light received by the light receiving elements A and B that are not adjacent to each other match. For example, since the microlens L3 and the light receiving element B3 and the microlens L1 and the light receiving element A1 respectively correspond to the light rays R3 and R4 from the same subject, the image is shifted by two pitches.
[0053]
On the other hand, in the case of the rear pin, detection elements having the same amount of received light are adjacent to each other, but light incident on the adjacent light receiving elements is light that passes through different microlenses. For example, since the microlens L1 and the light receiving element B1, and the microlens L3 and the light receiving element A3 respectively correspond to the light rays R3 and R4 from the same subject, the image is shifted by two pitches in the opposite direction to that at the front pin.
[0054]
In this way, image shift occurs according to the amount of focus shift. Actually, since the focus detection accuracy decreases with the image shift amount (phase production amount) in units of one pitch, a known interpolation calculation or the like is performed to detect the focus for one pitch or less. By detecting the image shift amount in this way, the focus shift amount of the photographing lens can be obtained.
[0055]
Here, FIG. 8A shows the configuration of the pixel unit 110 located in the imaging unit 100 portion among the pixel units arranged in a two-dimensional manner in the horizontal direction and the vertical direction shown in FIG. Will be described.
[0056]
In the figure, in the pixel unit 110, the output of the photodiode 101 is input to a pixel amplification circuit 102 that amplifies the charge generated by the photodiode 101. The pixel amplification circuit 102 includes a first stage amplifier 104 and a sample hold unit 105.
[0057]
The first stage amplifier 104 includes an amplifier A1, a storage capacitor C1, and a switch SW1, and constitutes an integrator. The output of the first stage amplifier 104 is input to the sample hold unit 105. The sample hold unit 105 includes a switch SW2, a hold capacitor C2, and a buffer A2.
[0058]
Then, the pixel unit 110 is initialized when the switches SW1 and SW2 are turned on, and then the accumulation operation is started when the switch SW1 is turned off. Further, when the switch SW2 is turned off, the accumulation level is held in the hold capacitor C2, and the accumulation operation is terminated. The on / off timing of the switches SW1 and SW2 is controlled by the control unit 111.
[0059]
Further, the accumulation level held by the hold capacitor C2 is output to Vsn through the buffer A2, selected by the X shift register 112 and the Y shift register 113, and output to the output unit 114.
[0060]
The focus detection unit 200 includes a pair of photodiodes 201a and 201b that respectively receive the light beams divided at the exit pupil of the photographing lens 11 by the micro lens group, and pixels that amplify the charges generated by the photodiodes 201a and 201b. A pixel unit 210 including amplifier circuits 202a and 202b is arranged.
[0061]
On the other hand, FIG. 8B is a diagram showing a detailed configuration of the pixel unit 210.
[0062]
As shown in the figure, the pixel amplifier circuits 202a and 202b have the same circuit configuration as the pixel amplifier circuit 102, respectively. The outputs of the pixel amplifier circuits 202a and 202b are selectively connected to the output Vsn via the switches SWa and SWb controlled by the control unit 111. Similarly to the pixel unit 103, the output Vsn is selected by the X shift register 112 and the Y shift register 113 outside the pixel unit 210 and output to the output unit 114.
[0063]
A color filter is disposed in front of the photodiode 101 of the imaging unit 100. The arrangement of the color filters is a so-called Bayer arrangement as shown in FIG. That is, in FIG. 9, R, G, and B indicate color filters that selectively transmit red, green, and blue, respectively.
[0064]
On the other hand, no color filter is arranged in front of the photodiodes 201a and 201b of the focus detection unit, and only the imaging unit 100 is arranged.
[0065]
As described above, it is possible to perform processing based on a known algorithm such as performing focus detection on the plurality of focus detection areas 200A, 200B, and 200C and automatically selecting the closest subject among them. Further, the photographer can select an AF area with an area selection switch 49 described later and focus on the area. In the focus detection area 200A, focus detection can be performed on an object having contrast in the horizontal direction with respect to the shooting screen 120, for example, a vertical line.
[0066]
On the other hand, in the focus detection areas 200B and 200C, focus detection can be performed on a subject having a contrast in the vertical direction with respect to the shooting screen 120 shown in FIG. 9, for example, a horizontal line. Therefore, it is possible to detect the focus even for a subject having only one direction of contrast.
[0067]
By the way, at the time of image creation, there is no image data for the focus detection areas 200A to 200C, so it is necessary to compensate.
[0068]
The method for supplementing this image data will be described below. In FIG. 4A, for example, the photodiodes 201a and 201b in the focus detection region 200A are the peripheral pixels of the photodiode 101A belonging to the imaging unit 100. It calculates | requires by interpolating using the pixel signal of -101E.
[0069]
At this time, it is needless to say that only pixel data of the same color filter may be used. As the interpolation calculation method, various methods such as simple averaging or weighted averaging of the pixel signals of the photodiodes 101A to 101E can be employed. Since this method is already known, detailed description is omitted.
[0070]
Next, FIG. 10 shows a detailed configuration of the video signal processing unit 42 and will be described.
[0071]
In FIG. 10, a fixed pattern noise (FPN) removal circuit 78 removes FPN and the like from the image signal of the image sensor 16. The gain control amplifier AMP79 amplifies the output of the FPN removal circuit 78 with a predetermined gain.
[0072]
The A / D converter 80 converts the output of the gain control amplifier 79 into a digital signal by AD conversion. The process processing circuit 81 performs various processes on the video signal converted into the digital signal.
[0073]
The image sensor control unit 43 outputs a drive signal to the image sensor 16 and controls its operation. The image sensor control unit 43 includes a timing generator 82 and a signal generator 83.
[0074]
That is, the timing generator (TG) 82 generates a drive signal such as a drive pulse for driving the image sensor 16, and also the sample hold pulse of the FPN removal circuit 78 and the AD conversion timing pulse of the A / D converter 80. Is generated. A signal generator (SG) 83 generates a signal for synchronizing the timing generator 82 and the microcomputer 31.
[0075]
The recording unit 44 includes a DRAM 84, a compression / decompression circuit 85, and a recording medium 86. The video signal (pixel data) output from the process processing circuit 81 in the video signal processing unit 42 is stored in the DRAM 84. The compression / decompression circuit 85 performs a compression process for recording by reducing the amount of pixel data stored in the DRAM 84 and a decompression process for restoring compressed data read from the recording medium 86. The recording medium 86 records the compressed still image data.
[0076]
Hereinafter, the operation of the microcomputer 31 will be described in detail with reference to the flowchart of FIG. In the following description, the time chart of FIG.
[0077]
When a power switch (not shown) is turned on or a battery is inserted, the microcomputer 31 starts operation and executes a sequence program stored in the internal ROM 31b.
[0078]
That is, when entering this sequence, first, each block in the imaging apparatus is initialized (step S1). Subsequently, the state of 1RSW 47 is detected (step S2).
[0079]
When the 1RSW 47 is off, the image pickup operation of the image pickup unit 6 is performed (accumulation (exposure) and read operation) (step S5), and photometry is performed based on the video signal of the image pickup unit 100 from the video signal processing unit 42. The exposure calculation unit 45 performs photometry and exposure calculation, calculates the aperture control value of the aperture 12 at the time of main exposure photography (image recording), the electronic shutter speed of the image sensor 6 and the like (step S6), and returns to step S2. .
[0080]
On the other hand, when 1RSW 47 is on, the accumulation operation (AF exposure) of the focus detection unit 200 of the image sensor 6 is performed, the image signal of the focus detection unit 200 is read (step S3), and the focus detection calculation is performed based thereon. (Step S4).
[0081]
This focus detection calculation is executed at timing F1 in FIG. 12 (f), and the calculation results in the focus detection areas 200A, 200B, and 200C are compared, and the closest area is selected. Can be adopted.
[0082]
Subsequently, it is determined whether the focus detection calculation result is in-focus or in-focus (step S7). If in-focus, the process proceeds to step S9. In the case of out-of-focus, the process proceeds to step S8, and the amount of movement of the focusing lens 1a that achieves in-focus is calculated and driven based on the focus detection calculation result. Then, the process returns to step S2, and the AF operation as described above is repeated. The driving of the focusing lens 1a is executed at the timing F2 in FIG.
[0083]
In step S9, it is detected whether 2RSW 48 is turned on. If it is turned on, the process proceeds to step S10. On the other hand, if the 2RSW 48 is off, the process proceeds to step S2, and the AF operation is continued while waiting for the 2RSW 48 to be on.
[0084]
In subsequent steps S1O and subsequent, the main exposure operation is performed.
[0085]
That is, the microcomputer 31 controls the aperture controller 33 to limit the aperture 2 to the exposure aperture value (step S10), and the image sensor control unit 43 turns off the charge reset signal RES (see FIG. 12B). Accumulation of the image sensor 6 is started, and the main exposure is performed by controlling the electronic shot speed based on the exposure calculation (step S11).
[0086]
This main exposure operation is executed at the timing of F3 in FIG.
[0087]
This electronic shutter operation is performed by generating a charge storage signal HOLD at a predetermined timing according to the shutter speed by the image sensor control unit 43 and holding the accumulated charge in the photodiode 101 (see FIG. 12C). .
[0088]
Next, the image sensor control unit 43 outputs the image readout signal DCLK to the image sensor 16, and the video signal processing unit 42 outputs the image signal of the image sensor 100 (in synchronization with the signal DCLK (see FIG. 12D)). The image pickup device signal) is A / D converted and read (step S12). Note that the reading of the image data is executed at the timing of F4 in FIG.
[0089]
Further, the microcomputer 31 controls the aperture controller 33 to transmit an aperture opening command to open the aperture 12 (step S13), perform processing such as compression of the read image signal, and then store it on the recording medium 86. Store (step S14). This image processing and recording operation are performed at the timing F5 in FIG.
[0090]
Thus, the series of photographing operations is completed, the process returns to step S2, and the above-described operation is repeated.
[0091]
Next, a second embodiment of the present invention will be described.
[0092]
In the second embodiment, the arrangement of the focus detection areas is changed with respect to the first embodiment described above.
[0093]
First, FIG. 13 is a diagram illustrating an arrangement state of focus detection areas of the image sensor in the imaging apparatus according to the second embodiment.
[0094]
As shown in the figure, in the shooting screen 120, the focus detection area 300A arranged in parallel with the long side direction of the shooting screen 120 with the optical axis of the shooting lens as the center, and the optical axis of the shooting lens as the center, 300B arranged in a direction perpendicular to the focus detection area 300A.
[0095]
FIG. 14 shows the arrangement of photodiodes in the image sensor of the image pickup apparatus according to the second embodiment.
[0096]
Similar to the first embodiment described above, the image pickup unit 100 is formed over the entire surface of the image pickup device 6, and as shown in FIG. 14, the focus detection units 300A and 300B are provided in the portion corresponding to the focus detection region. Is formed.
[0097]
A plurality of pairs of photodiodes 301 a and 301 b of the focus detection unit 300 </ b> A are arranged in parallel to the long side of the imaging screen 100, thereby forming a focus detection region. On the other hand, a plurality of pairs of photodiodes 301c and 301d in the focus detection area 300B are arranged perpendicular to the long side of the imaging screen, that is, parallel to the short side direction, thereby forming a focus detection area.
[0098]
In the second embodiment, by providing the cross-shaped focus detection area in this way, it is possible to detect the focus on the subject existing in the area near the center of the shooting screen regardless of the direction of contrast. .
[0099]
Next, a third embodiment of the present invention will be described.
[0100]
FIG. 15 is a diagram illustrating an arrangement of image pickup elements of the image pickup apparatus according to the third embodiment. The third embodiment further includes a plurality of combinations of cross-shaped focus detection areas shown in the second embodiment.
[0101]
The cross-shaped focus detection area 410A includes a horizontal focus detection area 400A and a vertical focus detection area 400B. Since the arrangement of the photodiodes on the image pickup device 6 in the vicinity of the similar cruciform focus detection areas 410A to 410E are all arranged in the same manner as in FIG. 14, a duplicate description is omitted here.
[0102]
In the third embodiment, the number of cruciform focus detection areas is further increased, so that focus detection can be performed over the entire shooting screen without being affected by the direction of subject contrast.
[0103]
Next, a fourth embodiment of the present invention will be described.
[0104]
FIG. 16 is a diagram illustrating an arrangement of image pickup elements of the image pickup apparatus according to the fourth embodiment. In the fourth embodiment, the focus detection area is extended obliquely with respect to the side of the shooting screen 120, and two rows of focus detection areas 510A and 510B are arranged in a cross shape so as to form a cross focus detection area. 501A is formed. Further, a plurality of the cross-shaped focus detection areas 501A are arranged. Note that the cross-shaped focus detection region 501A and the surrounding pixel configuration are as shown in FIG.
[0105]
Next, a fifth embodiment of the present invention will be described.
[0106]
The fifth embodiment is a modification of the first embodiment, and is different from the first embodiment in the configuration of the pixel unit.
[0107]
FIG. 18A is a diagram showing the configuration of the focus detection area 200A in the imaging device of the imaging apparatus according to the fifth embodiment, and FIG. 18B is the configuration of the pixel unit 210 in the focus detection area 200A. FIG.
As shown in FIG. 18A, in the fifth embodiment, the focus detection region 200A has an imaging photodiode 201c in addition to the pair of photodiodes 201a and 201b.
[0108]
Further, in FIG. 18B, the accumulation operation is performed with the switch Swg turned off during focus detection. In this case, the same operation as in the first embodiment described above is performed.
[0109]
On the other hand, when the recorded image is captured, the focus detection unit 200A does not perform the accumulation operation in the first embodiment described above. However, in the fifth embodiment, the accumulation operation is performed simultaneously with the imaging unit 100. .
[0110]
At that time, the switch SWg is turned on and the output of the photodiode 201c is also input to the pixel amplifier circuit 202a, so that not only the pupil-divided beam but also a wider beam including the pupil-divided beam is received and converted into a voltage signal.
[0111]
Then, by adding the added pixel signals of the obtained photodiodes 201a and 201c and the pixel signal of the photodiode 201b, an image signal corresponding to the case where the entire light flux is received can be obtained.
[0112]
In this manner, a higher quality image can be obtained by similarly creating an image signal for each of the focus detection areas 200A to 200C.
[0113]
FIG. 19 is a diagram showing the arrangement of the photodiodes of the focus detection unit 510A when the fifth embodiment is applied to the fourth embodiment (FIG. 17) described above. As shown in the drawing, an image photodiode 501c is provided in addition to the photodiodes 501a and 501b. At the time of recording and imaging, an image signal is created by adding the received light amounts of the photodiodes 501a, 501b, and 501c.
[0114]
As described above, since the optical characteristics of the micro lens 106 of the imaging unit 100 and the micro lens 206 of the focus detection unit 200 are different, the received light amount is different, but this light amount difference is stored in the EEPROM 31e in advance. The correction is performed for each pixel unit of the focus detection unit 200 to match the imaging unit 100.
[0115]
Next, a sixth embodiment of the present invention will be described.
[0116]
The sixth embodiment is a modification of the first embodiment described above, and in particular, the arrangement of the photodiodes is different.
[0117]
FIG. 21 is a diagram illustrating an arrangement of focus detection units of the image sensor in the image pickup apparatus according to the sixth embodiment.
[0118]
As shown in the figure, in the focus detection units 200A to 200C, units composed of a pair of focus detection photodiodes 201a and 201b and imaging photodiodes 101 are alternately arranged. In such a configuration, the detection pitch of the focus detection photodiode is twice that of the first embodiment. Therefore, although the focus detection accuracy is reduced to about ½, the image quality around the focus detection areas 200A to 200C can be improved.
[0119]
The photodiodes 201a and 201b in the focus detection area 200A are obtained by interpolating using the pixel signals of the photodiodes 101A to 101H that are the peripheral pixels and are effective as pixel data.
[0120]
In the sixth embodiment, since the number of effective pixel data for interpolation calculation is increased as compared with the first embodiment described above, the image quality can be further improved.
[0121]
Incidentally, although the unit composed of a pair of focus detection photodiodes 201a and 201b and the imaging photodiode 101 are alternately arranged, it is needless to say that it can be modified every 2 to 5 according to the required accuracy. It is.
[0122]
Next, a seventh embodiment of the present invention will be described.
[0123]
The seventh embodiment is a modification of the above-described first embodiment, and in particular, the arrangement of the color filters on the photodiode is different.
[0124]
FIG. 20 is a diagram illustrating the arrangement of the focus detection units of the image sensor in the imaging apparatus according to the seventh embodiment.
[0125]
In the first embodiment described above, the color filters are not arranged in the focus detection units 200A to 200C. However, in the seventh embodiment, the focus detection units 200A to 200C including the focus detection units 200A to 200C are the same. In addition, the color filters are regularly arranged according to the Bayer arrangement. During actual focus detection, the focus detection units 200A to 200C select pixel data of the same color filter and perform focus detection calculation.
[0126]
Of course, the color G pixel signal or the color B pixel signal may be individually subjected to focus detection calculation and averaged, or only one with high reliability may be selected. In this case, the detection pitch of focus detection becomes rough, but pixel signal information in the focus detection units 200A to 200C can also be adopted when creating a recorded image, and the quality of the image can be improved.
[0127]
Further, at the time of creating a recorded image, for example, for the focus detection area 200A, the pixel signals 201a and 201b (color G) are added and adopted as pixel data of that portion. Further, it is conceivable to perform interpolation processing or the like in consideration of the pixel signals 101A to 101D of the surrounding color G. The same processing may be applied to the color B pixel.
[0128]
As described above, in the present invention, the pupil-divided microlens group and the pair of light-receiving element groups that receive the pupil-divided light east are formed in a plurality of regions on the same chip as the image sensor, and the output of the light-receiving element group Since focus detection is performed based on this, it is possible to provide an imaging apparatus that has a focus detection area that is low-cost and space-saving, has a wide-field focus detection region, and has a high-speed and high-precision focus adjustment function.
[0129]
The embodiment of the present invention has been described above, but the present invention is not limited to this, and it is needless to say that various improvements and changes can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the image sensor is described as a MOS sensor, but a CCD or other type of solid-state image sensor may be used.
[0130]
In addition, the following invention is contained in the said embodiment of this invention.
[0131]
(1) In an imaging apparatus having an imaging element that performs photoelectric conversion of an optical image that passes through a photographic lens and forms an image on a light receiving surface;
First and second microlens arrays that are two-dimensionally arranged with the light receiving surface as a focal position,
A first light receiving element group having a single light receiving element as a constituent unit, which is arranged near the focal position of the first microlens array and outputs a first video signal,
A second light-receiving element group having a pair of light-receiving elements as structural units, which are arranged near the focal position of the second microlens array and each output a second video signal;
Comprising
An imaging apparatus, comprising: a plurality of focus detection block arrays in which the second microlens array and the second light receiving element group are regularly arranged.
[0132]
(2) In the above (1), the plurality of focus detection block rows are arranged so that the arrangement directions of the second light receiving element groups are different from each other.
[0133]
(3) In the above (1), the first light receiving element group and the second light receiving element group have different arrangement pitches on the imaging element.
[0134]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to reduce the cost, save space, have a wider focus detection area, improve the AF speed, and accurately without adding a new mechanism or optical system. An imaging apparatus having a focus adjustment function capable of performing focus adjustment can be provided.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an optical system of an imaging apparatus according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of an electrical system of the imaging apparatus according to the first embodiment.
FIG. 3 is a diagram showing a detailed configuration of an image sensor 6;
FIG. 4 is a diagram showing a detailed configuration of an image sensor 6;
FIG. 5 is a diagram showing a general cross-sectional configuration of an image sensor on which an on-chip microlens is formed.
6 is a diagram showing a state in which a light beam passing through the photographing optical system 11 is divided into pupils, and each divided light beam is incident on a pair of light receiving elements A and B, respectively. FIG.
7 is a diagram illustrating examples of focusing, a front pin, and a rear pin in the focus detection unit 200. FIG.
8A shows the configuration of the pixel unit 110 located in the imaging unit 100 among the pixel units arranged two-dimensionally in the horizontal and vertical directions shown in FIG. FIG. 2B is a diagram illustrating a detailed configuration of the pixel unit 210. FIG.
FIG. 9 is a diagram illustrating a Bayer array.
10 is a diagram showing a detailed configuration of a video signal processing unit 42. FIG.
FIG. 11 is a flowchart for explaining in detail the operation of the microcomputer 31 of the imaging apparatus according to the first embodiment;
FIG. 12 is a time chart for explaining in detail the operation of the microcomputer 31 of the imaging apparatus according to the first embodiment;
FIG. 13 is a diagram illustrating a state of arrangement of focus detection areas of an image sensor in an imaging apparatus according to a second embodiment.
FIG. 14 is a diagram illustrating an arrangement of photodiodes in an imaging element of an imaging apparatus according to a second embodiment.
FIG. 15 is a diagram illustrating an arrangement of imaging elements of an imaging apparatus according to a third embodiment.
FIG. 16 is a diagram illustrating an arrangement of image pickup elements of an image pickup apparatus according to a fourth embodiment.
FIG. 17 is a diagram showing a cross-shaped focus detection area 501A and a peripheral pixel configuration.
18A is a diagram illustrating a configuration of a focus detection area 200A in an image sensor of an imaging apparatus according to a fifth embodiment, and FIG. 18B is a diagram illustrating a configuration of a pixel unit 210 in the focus detection area 200A. FIG.
FIG. 19 is a diagram showing the arrangement of photodiodes in a focus detection unit 510A when the fifth embodiment is applied to the fourth embodiment (FIG. 17).
FIG. 20 is a diagram illustrating an arrangement of focus detection units of an image sensor in an imaging apparatus according to a sixth embodiment.
FIG. 21 is a diagram illustrating an arrangement of focus detection units of an image sensor in an imaging apparatus according to a seventh embodiment.
[Explanation of symbols]
1 Shooting optics
1a Focusing lens
2 Aperture
3 Beam splitter
4 Infrared cut filter
5 LPF
6 Image sensor
7 Mirror
8 Penta prism
9 Eyepiece
10 Finder optical system

Claims (3)

In an imaging apparatus having an imaging element that receives subject image light that has passed through a photographing lens,
The image sensor is
A first light receiving element group that receives subject image light passing through the photographing lens and has a color filter arranged in accordance with a predetermined rule on the front surface thereof, and collects subject image light to the first light receiving element group. A first micro lens group that emits light, and an imaging region unit that generates an output of the first light receiving element group for imaging,
The second minute lens group for pupil-dividing the luminous flux of the subject image light passing through the photographing lens and the luminous flux divided by the second minute lens group are respectively received and arranged on the front surface according to a predetermined rule. A pair of second light receiving element groups in which color filters are arranged , and a focus detection area unit that generates an output of the pair of light receiving element groups to perform focus detection;
Have
A focus detection unit that performs focus detection based on the output of the focus detection region unit;
An image creating unit that creates a captured image based on the output of the imaging region unit;
Comprising
The focus detection unit performs focus detection based on outputs of the pair of light receiving element groups in which color filters of the same color in the focus detection region unit are arranged.
An imaging apparatus characterized by that. The focus detection unit performs focus detection for each of a plurality of different color filters based on outputs of the pair of light receiving element groups in which the color filters of the same color are arranged, and outputs a plurality of focus detection results corresponding to the different color filters. Use the average value as the focus detection result
The imaging apparatus according to claim 1. The focus detection unit performs focus detection for each of a plurality of different color filters based on outputs of the pair of light receiving element groups in which the color filters of the same color are arranged, and outputs a plurality of focus detection results corresponding to the different color filters. Choose a focus detection result that is more reliable
The imaging apparatus according to claim 1.

Images