JP5963550B2 - IMAGING DEVICE AND IMAGING DEVICE CONTROL METHOD - Google Patents

Description

  The present invention relates to an imaging apparatus that performs phase difference type focus detection using an imaging device having a plurality of photodiodes for one microlens.

  2. Description of the Related Art Conventionally, there has been known an imaging apparatus that performs phase difference type focus detection using an imaging element having a plurality of photodiodes for one microlens. Patent Document 1 discloses an imaging device in which a photodiode in one pixel is divided into two, and each photodiode receives light in a different region of the pupil plane of the imaging lens. Yes. Focus detection is possible by comparing the outputs of two photodiodes. Thereby, it is possible to perform focus detection by the phase difference method while displaying an image captured from the image sensor in real time (live view).

  In order to perform a high-speed focusing operation during phase difference type focus detection, it is necessary to increase the number of focus detections per unit time. For this reason, it is possible to reduce the readout time by partially reading the specific area of the image sensor and increase the number of focus detections per unit time.

JP 2001-083407 A

  However, if the number of focus detections (frame rate) is increased in order to perform a high-speed focusing operation, it is difficult to increase the readout area of the image sensor and maintain focus detection accuracy. On the other hand, if the readout area of the image sensor is increased in order to maintain focus detection accuracy, it is difficult to increase the number of focus detections (frame rate) and realize a high-speed focusing operation. In other words, with the conventional configuration, it is impossible to achieve both high-speed focusing operation and maintenance of focus detection accuracy.

  Therefore, the present invention provides an imaging apparatus capable of focusing at high speed and high accuracy when performing focus detection using an imaging element, and a method for manufacturing the imaging apparatus.

An imaging apparatus according to an aspect of the present invention includes an imaging device having a plurality of photodiodes for one microlens, and focus detection that performs phase-difference focus detection based on pixel signals output from the imaging device. And a control unit that performs focus control based on a detection result of the focus detection unit, and the control unit sets the pixel signal readout region according to the aperture value when performing the focus detection. If the first aperture value is greater than the second aperture value, the first frame rate for the first aperture value is set to the second aperture value. Higher than the second frame rate .

An imaging apparatus control method according to another aspect of the present invention is an imaging apparatus control method including an imaging element having a plurality of photodiodes with respect to one microlens. A step of setting a readout region of the pixel signal output from the element; a step of setting a frame rate according to the readout region of the pixel signal; and the imaging at the readout region and the frame rate of the pixel signal a step of performing focus detection of a phase difference method based on the pixel signals output from the device, have a, and performing focus control based on a result of the focus detection, the first aperture is a second If greater than the aperture value, higher than the second frame rate of the first frame rate for the first aperture with respect to the second aperture

  Other objects and features of the present invention are illustrated in the following examples.

  ADVANTAGE OF THE INVENTION According to this invention, when performing focus detection using an image pick-up element, the imaging device which can focus at high-speed and high precision, and the manufacturing method of an imaging device can be provided.

It is a block diagram of the imaging device in a present Example. 1 is an overall configuration diagram of an image sensor in the present embodiment. It is a block diagram of one pixel contained in the image pick-up element in a present Example. It is a block diagram of the pixel array of the image pick-up element in a present Example. FIG. 3 is a conceptual diagram illustrating a state where a light beam from an exit pupil of an imaging lens is incident on an image sensor 103 in the present embodiment. It is a block diagram of the video signal processing part in a present Example. It is a flowchart of the live view AF process in a present Example. It is a figure which shows the relationship of the read-out area | region of an image pick-up element in this Example, and a phase difference detection.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same members are denoted by the same reference numerals, and redundant description is omitted.

  First, with reference to FIG. 1, the structure of the imaging device in a present Example is demonstrated. FIG. 1 is a configuration diagram of an imaging apparatus 100 in the present embodiment. In FIG. 1, reference numeral 110 denotes a power source. The power supply 110 supplies power to each circuit in the imaging apparatus 100. Reference numeral 172 denotes a card slot. A memory card 173 (detachable storage medium) is inserted into the card slot 172. In a state where the memory card 173 is inserted into the card slot 172, the memory card 173 is electrically connected to the card input / output unit 171. In this embodiment, the memory card 173 is adopted as the storage medium. However, other storage media such as a hard disk, an optical disk, a magneto-optical disk, a magnetic disk, or other solid-state memory may be used.

  Reference numeral 101 denotes an imaging lens that forms an optical image of the subject (subject image) on the imaging element 103. The imaging lens 101 is subjected to zoom control, focus control, aperture control, and the like by the lens driving unit 141. Reference numeral 102 denotes a mechanical shutter. The mechanical shutter 102 is controlled by the shutter driving unit 142. The imaging lens 101 and the mechanical shutter 102 constitute an imaging optical system. In this embodiment, the imaging optical system is incorporated in the main body of the imaging apparatus 100 (configured integrally). However, the present embodiment is not limited to this, and can also be applied to a case where the imaging optical system is configured to be detachable from the main body of the imaging apparatus 100.

  The image sensor 103 is a photoelectric conversion means configured to include a CMOS, a CCD, or the like. The image sensor 103 photoelectrically converts a subject image formed by the imaging optical system and outputs an image signal (pixel signal). As will be described later, the image sensor 103 of the present embodiment is configured to have a plurality of photodiodes for one microlens.

  Next, the configuration of the image sensor 103 in the present embodiment will be described in detail with reference to FIG. FIG. 2 is an overall configuration diagram of the image sensor 103. As illustrated in FIG. 2, the imaging element 103 includes a pixel array 201, a vertical selection circuit 202 that selects a row of the pixel array 201, and a horizontal selection circuit 204 that selects a column of the pixel array 201. In addition, the image sensor 103 includes a readout circuit 203 that reads a signal (pixel signal) of a pixel selected by the vertical selection circuit 202 among the pixels in the pixel array 201. The image sensor 103 also has a serial interface 205 (SI) for determining the operation mode of each circuit from the outside. The reading circuit 203 includes a memory for storing signals, a gain amplifier, an AD converter, and the like for each column. Typically, the vertical selection circuit 202 sequentially selects a plurality of rows of the pixel array 201 and reads them out to the reading circuit 203. Further, the image sensor 103 has a horizontal selection circuit 204. The horizontal selection circuit 204 sequentially selects a plurality of pixel signals read by the reading circuit 203 for each column. By appropriately changing the operations of the vertical selection circuit 202 and the horizontal selection circuit 204, it is possible to realize reading of a specific area (a specific pixel signal reading area).

  Next, the configuration of one pixel included in the pixel array 201 of the image sensor 103 will be described with reference to FIG. FIG. 3 is a configuration diagram of one pixel. Reference numeral 300 denotes one pixel. One pixel 300 has one microlens 301. A plurality of photodiodes (hereinafter referred to as “PD”) are provided for one pixel 300. In this embodiment, as shown in FIG. 3, four photodiodes 302 a, 302 b, 302 c, and 302 d are provided for one microlens 301. However, the present embodiment is not limited to this, and it is sufficient that two or more photodiodes are provided for one microlens. For example, a configuration having two PDs or nine PDs for one microlens may be employed. In this embodiment, the output signals of a plurality of photodiodes can be selected and added. For example, the output signals of PD 302a and PD 302c and PD 302b and PD 302d may be added to generate two output signals from these four PDs. In addition to the components shown in FIG. 3, the pixel 300 includes, for example, a pixel amplification amplifier for reading a PD signal (output signal) to the column readout circuit 203, a selection switch for selecting a row, and resetting the PD signal. A reset switch is provided.

  Next, the configuration of the pixel array 201 of the image sensor 103 will be described with reference to FIG. FIG. 4 is a configuration diagram of the pixel array 201 of the image sensor 103. In order to acquire a two-dimensional image, the pixel array 201 is configured by arranging a plurality of N pixels 300 in the horizontal direction and M in the vertical direction in a two-dimensional array, as shown in FIG. Yes. Each pixel 300 of the pixel array 201 is provided with a color filter. In the present embodiment, red and green color filters are provided repeatedly for odd-numbered pixels, and green and blue color filters are provided repeatedly for even-numbered pixels.

  Next, with reference to FIG. 5, how the image sensor 103 according to the present embodiment receives light will be described. FIG. 5 is a conceptual diagram showing a state in which the light beam from the exit pupil of the imaging lens is incident on the imaging element 103. Reference numeral 501 denotes a pixel array including three pixels. Reference numeral 502 denotes a microlens, 503 denotes a color filter, and 504 and 505 denote photodiodes (PD). The PDs 504 and 505 correspond to the PDs 302a and 302b shown in FIG. Reference numeral 506 denotes an exit pupil of the imaging lens. Reference numeral 509 denotes an optical axis, which is the center of the light beam emitted from the exit pupil with respect to the pixel having the microlens 502. Light emitted from the exit pupil 506 is incident on the image sensor 103 with the optical axis 509 as the center. Reference numerals 507 and 508 denote partial areas of the exit pupil 506 of the imaging lens. Reference numerals 510 and 511 denote outermost rays of the light passing through the partial area 507 of the exit pupil. Reference numerals 512 and 513 denote outermost rays of the light passing through the partial area 508 of the exit pupil.

  As shown in FIG. 5, among the light beams emitted from the exit pupil 506, the upper light beam is incident on the PD 505 and the lower light beam is incident on the PD 504 with the optical axis 509 as a boundary. That is, the PD 504 and the PD 505 receive light in different regions at the exit pupil 506 of the imaging lens. With this characteristic, at least two images with parallax can be acquired. Image data obtained from a plurality of right PDs is called a right image, and data obtained from a plurality of left PDs is called a left image. At this time, phase difference autofocus (phase difference AF) based on phase difference detection can be realized by using one line of the right image and one line of the left image arranged at the corresponding position.

  Next, the configuration and operation of the video signal processing unit 121 will be described with reference to FIGS. 1 and 6. FIG. 6 is a block diagram of the video signal processing unit 121. As shown in FIG. 1, the output signal (pixel signal) of the image sensor 103 is input to the video signal processing unit 121 and subjected to predetermined signal processing. As shown in FIG. 6, the video signal processing unit 121 includes a phase difference detection unit 601, an image addition unit 602, and a development processing unit 603.

  The phase difference detection unit 601 is a focus detection unit that performs phase difference type focus detection based on a pixel signal output from the image sensor 103. That is, the phase difference detection unit 601 detects a phase difference from the left image and the right image (pixel signal) output from the image sensor 103 and outputs the detection result to the memory 132 via the bus 150. The phase difference detection unit 601 also outputs the reliability of the calculated phase difference at the same time. In this embodiment, the detection result regarding the phase difference and its reliability may be output to the internal memory of the phase difference detection unit 601 instead of the memory 132. The image addition unit 602 performs addition synthesis of the right image and the left image (pixel signal) and outputs the result as one image data. The development processing unit 603 performs processing such as white balance, color interpolation, color correction, γ conversion, edge enhancement, resolution conversion, and image compression of digital image data.

  In FIG. 1, the memory 132 temporarily stores data necessary for the CPU 131 to perform various processes in addition to the output image data of the video signal processing unit 121. The CPU 131 (control unit) controls reading of pixel signals from the image sensor 103 and controls operation timings of the image sensor 103, the video signal processing unit 121, the memory 132, and the like. The CPU 131 performs focus control based on the detection result of the phase difference detection unit 601. The timing generator 143 provides timing to the image sensor 103 and the video signal processing unit 121.

  To the bus 150, a lens driving unit 141, a shutter driving unit 142, an image sensor 103, a timing generator 143, a video signal processing unit 121, a CPU 131, a power supply 110, a memory 132, and a display control device 151 are connected. The bus 150 includes a main switch 161, a first release switch 162, a second release switch 163, a live view start / end button 164, an AF start / end button 165, an up / down / left / right selection button 166, a setting button 167, a card input / output. Unit 171 is connected.

  The display control device 151 drives and controls the TFT 152 (liquid crystal display element), and exchanges signals with an external device via the VIDEO output terminal 153 or the HDMI terminal 154. Further, the display control device 151 outputs the image data arranged in the image format for display in the memory 132 to each display device. Here, the display image data area arranged in the memory 132 is referred to as VRAM.

  When the user turns on the main switch 161, the CPU 131 executes a predetermined program. When the main switch 161 is turned off, a predetermined program is executed, and the imaging apparatus 100 (camera) is set to the standby mode. The first release switch 162 is turned on at the first stroke (half-pressed state) of the release button. The second release switch 163 is turned on by the second stroke (fully pressed state) of the release button. In addition, the CPU 131 performs control according to the pressing of the up / down / left / right selection button 166 or the setting button 167 and the operation state of the imaging apparatus 100. For example, during live view, a subject to be autofocused can be specified with the up / down / left / right selection buttons 166. The live view can be switched between the normal mode and the zoom mode by performing selection and setting on the graphical user interface with the up / down / left / right selection button 166 and the setting button 167. When the live view start / end button 164 is pressed, image data is captured periodically (for example, 30 times per second) from the image sensor 103 and placed in the VRAM, thereby displaying an image captured from the image sensor 103 in real time. be able to. When the live view start / end button 164 is pressed while the live view is operating, the live view is ended.

  The AF start / end button 165 is an instruction unit that instructs the CPU 131 to start autofocus control. When the start of autofocus control is instructed by the AF start / end button 165, the CPU 131 causes the phase difference detection unit 601 to perform phase difference detection (focus detection).

  Next, with reference to FIG. 7 and FIG. 8, the live view AF process (control method of the imaging apparatus 100) in the imaging apparatus 100 of the present embodiment will be described. FIG. 7 is a flowchart of the live view AF process. Each step in the flowchart of FIG. 7 is executed based on a command from the CPU 131 according to a program stored in the CPU 131. FIG. 8 is a diagram showing the relationship between the pixel signal readout region and the phase difference detection in this embodiment.

  First, in step S100 of FIG. 7, when the CPU 131 detects that the live view start / end button 164 is pressed, it starts the live view AF process. Subsequently, in step S101, the CPU 131 determines whether or not the AF start / end button 165 is on (pressed). If the AF start / end button 165 has not been pressed (if off), the process returns to step S101, and the CPU 131 repeats this determination process until it detects that the AF start / end button 165 has been pressed. On the other hand, when the CPU 131 detects that the AF start / end button 165 is pressed (when on), the CPU 131 stops the real-time display and continues to display the last image, and proceeds to step S102.

  Next, in step 102, the CPU 131 sets a pixel signal readout region for the image sensor 103 in accordance with the aperture value set in the lens driving unit 141. For example, as illustrated in FIG. 8A, when the aperture value (F value) is 22, the imaging element 103 receives specific areas ((X2, Y) to (X3, Y) out of the entire angle-of-view reading area. )) Pixel signal is read out. On the other hand, as shown in FIG. 8B, when the aperture value is 1.8, the pixel signal of the specific region ((X1, Y) to (X4, Y)) is read from the image sensor 103. .

  As described above, when the first aperture value (for example, F = 22) is larger than the second aperture value (for example, F = 1.8), the CPU 131 sets the first aperture value of the pixel signal with respect to the first aperture value. The readout area (X2 to X3) is made smaller than the second readout area (X1 to X4). In this embodiment, as the aperture value increases, the depth of field increases, so the calculation is performed from a table designed to reduce the readout area. In FIG. 8, a central rectangular area (shaded area) is an area indicating a range to be focused, and a reading area is set to be larger than the central rectangular area.

  Subsequently, in step S103, the CPU 131 sets a frame rate for the image sensor 103 so as to read an image (pixel signal) at a frame rate corresponding to the reading area set in step S102. That is, when the first readout area (X2 to X3) of the pixel signal is smaller than the second readout area (X1 to X4), the CPU 131 sets the first frame rate for the first readout area to the second readout area. Higher than the second frame rate. In this embodiment, the frame rate is the number of frames displayed per unit time, and is equal to the number of focus detections per unit time. In this embodiment, the readout area set in the case of the aperture value (F = 22) in FIG. 8A is the readout area set in the case of the aperture value (F = 1.8) in FIG. Narrower (smaller) than the area. Therefore, the frame rate can be increased in the case of FIG. 8A than in the case of FIG.

  Next, in step S104, the CPU 131 (phase difference detection unit 601) performs phase difference detection (focus detection). That is, the CPU 131 reads the detection result of the phase difference detection unit 601 from the memory 132 and calculates the phase difference using the detection result. Here, the detection result of the phase difference detection unit 601 is the pixel signal of the readout area X2 to X3 or the readout area X1 to X4, that is, line data (left image line data, right image) in FIGS. 8 (a) and 8 (b). The phase difference obtained from the line data.

  Subsequently, in step S105, the CPU 131 performs in-focus determination. That is, the CPU 131 determines whether or not the phase difference detected in step S104 is within a predetermined threshold. If this phase difference is outside the predetermined threshold, the process proceeds to step S106. In step S <b> 106, the CPU 131 calculates the focus control amount of the imaging lens 101 based on the phase difference detected in step S <b> 104 and performs focus control via the lens driving unit 141. When the focus control in step S106 is completed, the process proceeds to step S104.

  On the other hand, if it is determined in step S105 that the phase difference detected in step S104 is within a predetermined threshold, the process proceeds to step S107. In step S <b> 107, the CPU 131 displays the completion of focusing on the TFT 152 via the display control device 151. Subsequently, in step S108, the CPU 131 determines whether or not the AF start / end button 165 is off (not pressed). When the AF start / end button 165 is pressed (when on), the determination in step S108 is repeated until the AF start / end button 165 is turned off. On the other hand, if the AF start / end button 165 has not been pressed (if off), the process proceeds to step S109. In step S <b> 109, the CPU 131 cancels the in-focus notification displayed on the TFT 152. When the cancellation of the display is completed, the process returns to step S101, and the series of processes in FIG. 7 is repeated.

  As shown in FIGS. 7 and 8, in the present embodiment, when performing focus detection, the CPU 131 changes the pixel signal readout area in accordance with the aperture value, and changes the frame rate in accordance with the readout area. . That is, when the first aperture value is larger than the second aperture value, the CPU 131 makes the first frame rate for the first aperture value higher than the second frame rate for the second aperture value.

  As described above, in the present embodiment, in the live view focusing process by partial reading, the frame rate is increased by changing the reading area of the image sensor according to the aperture value while ensuring the detection accuracy at the time of detecting the phase difference. As a result, it is possible to realize an autofocus operation that achieves both detection accuracy and operation speed. That is, according to the present embodiment, it is possible to provide an imaging apparatus and an imaging apparatus control method capable of focusing at high speed and with high accuracy when focus detection is performed using an imaging element.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

100 imaging device 103 imaging device 131 CPU
300 pixels 601 phase difference detection unit

Claims (11)

An imaging device having a plurality of photodiodes for one microlens;
Focus detection means for performing phase difference focus detection based on pixel signals output from the image sensor;
Control means for performing focus control based on the detection result of the focus detection means,
When the focus detection is performed , the control unit changes the readout area of the pixel signal according to the aperture value, changes the frame rate according to the readout area, and the first aperture value is the second aperture value. If greater than the value, it characterized by higher than the second frame rate of the first frame rate for the first aperture with respect to the second aperture imaging device. An imaging device having a plurality of photodiodes for one microlens;
Focus detection means for performing phase difference focus detection based on pixel signals output from the image sensor;
Control means for performing focus control based on the detection result of the focus detection means,
When performing the focus detection , the control unit changes the readout area of the pixel signal according to the aperture value, changes the frame rate according to the readout area, and the first readout area of the pixel signal is when the second smaller than the read area, IMAGING dEVICE you said to be higher than the second frame rate of the first frame rate for the first read area for reading region of the second. When the first readout area of the pixel signal is smaller than the second readout area, the control means sets the first frame rate for the first readout area to the second frame rate for the second readout area. The imaging device according to claim 1, wherein the imaging device is higher than the height. An imaging device having a plurality of photodiodes for one microlens;
Focus detection means for performing phase difference focus detection based on pixel signals output from the image sensor;
Control means for performing focus control based on the detection result of the focus detection means,
When the focus detection is performed , the control unit changes the readout area of the pixel signal according to the aperture value, changes the frame rate according to the readout area, and the first aperture value is the second aperture value. If greater than the value, IMAGING dEVICE you characterized in that less than the first readout region of the pixel signal relative to the first aperture second read area. When the first aperture value is larger than the second aperture value, the control means makes the first readout region of the pixel signal for the first aperture value smaller than the second readout region. The imaging device according to any one of claims 1 to 3. Further comprising an instruction means to instruct the start of the auto focus control with respect to said control means,
Wherein, when the start of the auto focus control is instructed by the instruction means, according to any one of claims 1 to 5, characterized in that to perform the focus detection in the focus detection unit Imaging device. A method for controlling an imaging apparatus including an imaging device having a plurality of photodiodes for one microlens,
Setting a readout area of a pixel signal output from the image sensor in accordance with an aperture value;
Setting a frame rate according to the readout region of the pixel signal;
Performing phase difference type focus detection based on the pixel signal output from the image sensor at the readout region and the frame rate of the pixel signal;
Performing focus control based on the result of the focus detection,
When the first aperture value is larger than the second aperture value, the first frame rate for the first aperture value is set higher than the second frame rate for the second aperture value. the method of that imaging device. A method for controlling an imaging apparatus including an imaging device having a plurality of photodiodes for one microlens,
Setting a readout area of a pixel signal output from the image sensor in accordance with an aperture value;
Setting a frame rate according to the readout region of the pixel signal;
Performing phase difference type focus detection based on the pixel signal output from the image sensor at the readout region and the frame rate of the pixel signal;
Performing focus control based on the result of the focus detection,
When the first readout area of the pixel signal is smaller than the second readout area, the first frame rate for the first readout area is set higher than the second frame rate for the second readout area. control method for you characterized IMAGING device. When the first readout area of the pixel signal is smaller than the second readout area, the first frame rate for the first readout area is set higher than the second frame rate for the second readout area. The method for controlling an imaging apparatus according to claim 7. A method for controlling an imaging apparatus including an imaging device having a plurality of photodiodes for one microlens,
Setting a readout area of a pixel signal output from the image sensor in accordance with an aperture value;
Setting a frame rate according to the readout region of the pixel signal;
Performing phase difference type focus detection based on the pixel signal output from the image sensor at the readout region and the frame rate of the pixel signal;
Performing focus control based on the result of the focus detection,
If the first aperture is larger than the second aperture, an imaging you characterized in that less than the first readout region of the pixel signal relative to the first aperture second read area Control method of the device. 8. The first readout area of the pixel signal for the first aperture value is made smaller than the second readout area when the first aperture value is larger than the second aperture value. The control method of the imaging device according to any one of 1 to 9.