JP2010066712A - Focus adjusting device and image pickup apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the risk of missing photo opportunity by reducing the possibility of shifting to the scanning auto focus by enlarging the defocusing range. <P>SOLUTION: A position with the highest correlation value between the correlation sensing blocks Ha is sensed by a first sensing means of an AF controller 122 as the focus position while displacing the correlation sensing blocks Ha of a pair of sensor arrays SA and SB. In the case the focus displacement is not sensed with the first focus sensing means, a position with the highest correlation value between the correlation sensing blocks Hb is sensed by a second sensing means as the focus position while displacing the correlation sensing blocks Hb narrower than the correlation sensing blocks Ha of a pair of the sensor arrays SA and SB. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a focus adjustment device that detects a focus shift from a subject image, and an imaging device including the focus adjustment device.

Conventionally, there is a phase difference method as one of the autofocus methods of a digital single lens reflex camera. This phase difference type autofocus (AF) detects a shift in the output of a sensor having a pair of parallaxes using a sensor that detects a shift in focus (hereinafter referred to as an AF sensor), thereby reducing the shift in focus. Ask.
When focus shift cannot be detected by this autofocus, the process proceeds to scan AF. This scan AF searches for a position where a focus shift can be detected while moving the focus adjustment lens from the infinity (∞) end to the closest end.

  However, since scan AF detects a focus shift while driving a focus adjustment lens, it takes time to focus, and as a result, there is a possibility of missing a photo opportunity.

For example, Patent Literature 1 discloses a technique for solving such a problem. In Patent Document 1, a photoelectric conversion unit that captures an image of a subject through a photographing lens and outputs focus detection image data, a command output unit that outputs a focus adjustment command, and a focus adjustment command are output from the command output unit. A focus detection unit that detects the focus adjustment state of the photographic lens based on the focus detection image data output from the photoelectric conversion unit, and whether or not focus detection is possible based on the detection result of the focus detection unit. When the determination means determines that the focus detection is impossible when the focus adjustment command is output, the scan operation control means for imaging the subject with the photoelectric conversion means while performing the scanning operation of the photographing lens, and the command output After the focus adjustment command is no longer output from the means, the prohibition means for prohibiting the scanning operation for a predetermined time and the focus detection when the determination means determines that focus detection is possible. And a lens driving unit that drives the photographic lens toward the in-focus position based on the detection result of the output unit, thereby prohibiting the scanning operation for a predetermined time, thereby suppressing the unnecessary scanning operation. Preventing missed photo opportunities.
JP 2006220928 A

For example, there are two factors that cannot detect a focus shift. One reason is that the AF sensor does not function sufficiently because the contrast of the subject is low, and the other reason is that the AF sensor is in a range where the focus shift of the AF sensor can be detected, that is, beyond the defocus range. This is a case where a focal position exists.
The former factor is unlikely to be able to detect the in-focus position even after performing scan AF. On the other hand, with the latter factor, the focus position can be detected by scan AF.

  However, in Patent Document 1, for example, although continuous scan AF is prevented, it is not a solution for the essential problem of shortening the time until focusing.

  The present invention has been made with the above problems in mind, and provides a focus adjustment device and an imaging device that can reduce the possibility of shifting to scan AF by widening the defocus range and reduce the possibility of missing a photo opportunity. The purpose is to do.

  A focus adjustment apparatus according to a main aspect of the present invention includes an optical system that forms a subject image, a first focus detection unit that detects a focus shift of the subject image formed by the optical system, and an optical system. The focus detection result by the second focus detection means for detecting the focus shift of the formed subject image in a range different from the first focus detection means, and the first focus detection means or the second focus detection means. And a focus adjusting means for adjusting the position of the optical system on the basis thereof.

  An imaging apparatus according to a main aspect of the present invention includes the focus adjustment apparatus.

  According to the present invention, it is possible to provide a focus adjustment device and an imaging device that reduce the possibility of shifting to scan AF by widening the defocus range and reduce the possibility of missing a photo opportunity.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a digital single-lens reflex camera (hereinafter referred to as a camera) as an imaging apparatus provided with an autofocus adjustment device. FIG. 2 is an external perspective view of the camera. This figure shows the state during normal focus adjustment (AF during phase difference detection). This camera includes an interchangeable lens 101 and a camera body 110.
The interchangeable lens 101 is detachably attached to the camera body 110 via a camera mount provided on the front surface of the camera body 110. The interchangeable lens 101 includes a photographing optical system including a focus lens 102, a lens driving unit 103, a lens CPU 104, a focus adjustment mechanism 106, an encoder 107, and the like.

The focus lens 102 is an optical system that forms a subject image, and is included in the photographing optical system to perform focus adjustment. The focus lens 102 is moved in the same direction (arrow A direction) as the direction of the optical axis P by the lens driving unit 103 to adjust the focus position. Thereby, the light beam from the subject that has passed through the photographing optical system including the focus lens 102 forms a focused subject image on the image sensor 124 in the camera body 110.
The lens driving unit 103 includes a DC motor, and drives the DC motor by a pulse signal from the lens CPU 104 to move the focus lens 102 in the arrow A direction.
The lens CPU 104 performs drive control of the lens driving unit 103 and the like. The lens CPU 104 stores various lens data such as manufacturing variation information of the focus lens 102 and aberration information of the focus lens 102 in advance. The lens CPU 104 can communicate with the system controller 123 in the camera body 110 via the communication connector 105. Accordingly, the lens CPU 104 transmits various lens data such as focus lens manufacturing variation information and focus lens aberration information stored in advance to the system controller 123, for example.

  The focus adjustment mechanism 106 is an operation mechanism for the user to directly control the driving of the focus lens 102 in the manual focus mode. This focus adjustment mechanism 106 is on the near side (the distance between the principal point of the photographing optical system including the focus lens 102 and the imaging surface is the minimum. The right side in FIG. 1) or the infinity side (the photographing optical including the focus lens 102). The distance between the principal point of the system and the imaging plane is the maximum (left side in FIG. 1), and the driving direction and driving amount can be given.

  The encoder 107 detects the drive direction and drive amount of the focus adjustment mechanism 106 and transmits a pulse signal corresponding to the drive direction and drive amount to the lens CPU 104. The lens CPU 104 counts the pulse signal from the encoder 107, detects the drive amount and drive direction of the focus adjustment mechanism 106 from the count value, and drives the focus lens 102 according to these drive amount and drive direction. The lens driving unit 103 is controlled.

On the other hand, the camera body 110 includes a main mirror 111, a focusing screen 112, a pentaprism 113, an eyepiece lens 114, a sub mirror 116, a condenser lens 117, a total reflection mirror 118, a separator diaphragm 119, and a separator lens 120. And an AF sensor 121, an AF controller 122, a system controller 123, an image sensor 124, a display unit 125, a memory card 126, a rotary switch 127, a release button 128, a setting switch 129, and the like.
Among these, the focusing screen 112, the pentaprism 113, and the eyepiece lens 114 constitute a finder optical system. Similarly, the condenser lens 117, the total reflection mirror 118, the separator diaphragm 119, and the separator lens 120 constitute an AF optical system.

  The main mirror 111 has a half mirror at the center. The main mirror 111 is configured to be rotatable and moves between a down position and an up position. The main mirror 111 is disposed on the optical axis P when in the down position, and reflects and transmits part of the light beam from the subject incident on the camera body 110 via the interchangeable lens 101. The main mirror 111 retracts from the optical axis P when in the up position.

A light beam reflected by the main mirror 111 is imaged on the focusing screen 112.
The pentaprism 113 causes the subject image formed on the focusing screen 112 to enter the eyepiece lens 114 as an erect image.
The eyepiece 114 enlarges the subject image from the pentaprism 113 so that the user can observe it. Thereby, the user can observe the state of the subject by looking into the eyepiece lens 114.
The sub mirror 116 is installed on the back surface of the half mirror portion of the main mirror 111. The sub mirror 116 reflects the light beam transmitted through the half mirror portion of the main mirror 111 in the direction of the AF optical system.

  The condenser lens 117 of the AF optical system collects the light beam reflected by the sub-mirror 116 and formed on a primary imaging surface (not shown) and makes it incident in the direction of the total reflection mirror 118.

Total reflection mirror 118 reflects the light beam from condenser lens 117 toward AF sensor 121.
The separator diaphragm 119 is disposed in front of the AF sensor 121 and divides the light beam from the total reflection mirror 118 into pupils.
The separator lens 120 condenses the luminous flux divided by the separator diaphragm 119 and re-images it on the AF sensor 121.
The AF sensor 121 converts a pupil-divided and re-imaged paired subject image incident through the separator lens 120 into a video signal. The AF sensor 121 can detect the focus state in a plurality of focus detection areas in the shooting screen.

  The AF controller 122 has a function as a defocus amount calculation unit that reads a paired video signal from the AF sensor 121 and calculates a two-image interval value of the subject image by, for example, correlation calculation based on the read video signal. The defocus amount is calculated based on the two-image interval value obtained by the AF controller 122. Further, the AF controller 122 selects a defocus amount to be used for focus adjustment from the defocus amounts calculated corresponding to a plurality of distance measuring points during focus adjustment, and uses the selected defocus amount as a lens. It transmits to CPU104. Accordingly, the lens CPU 104 performs focus adjustment of the focus lens 102 based on the defocus amount from the AF controller 122.

The system controller 123 controls the overall operation of the camera. The system controller 123 has a memory for storing a defocus amount calculated from the two-image interval value obtained by the AF controller 122.
When the main mirror 111 is at the up position and retracted from the optical axis P, the image sensor 124 converts a subject image formed through the photographing optical system into a video signal. As a result, the system controller 123 performs various image processing on the video signal obtained by the image sensor 124, and then displays the image acquired by the image processing on the display unit 125 or displays the image data. Store in the memory card 126.

The setting switch 129 includes a switch such as a setting button, and is provided on the exterior of the camera body 110. The setting switch 129 gives various setting instructions for switching the state of the camera to the system controller 123 in response to a user operation on a setting button or the like. Various setting instructions include a focus mode, a field angle of a captured image, and the like.
The rotary switch 127 is a switch that is provided on the exterior of the camera body 110 and switches a target function depending on the shooting mode, and gives a movable amount to the system controller 123.

  The release button 128 is provided on the exterior of the camera body 110, and gives an instruction to switch the state, for example, an instruction to start AF and an instruction to start imaging to the system controller 123, for example, in response to a user operation. The release button 128 includes a 1st release switch and a 2nd release switch. The release button 128 turns on the 1st release switch in response to a half-press operation by the user. When the first release switch is turned on, the release button 128 gives an instruction to start AF to the system controller 123. The release button 128 turns on the 2nd release switch in response to a full pressing operation by the user. When the 2nd release switch is turned on, the release button 128 gives an instruction to start imaging to the system controller 123.

As shown in FIG. 2, the interchangeable lens 101 is rotatably provided with a focus ring 205 as a part of the focus adjustment mechanism 106. For example, the focus ring 205 rotates in response to a user's rotation operation. The driving direction and driving amount of the focus ring 205 are detected by the encoder 107 as described above.
A viewfinder 203 is provided on the back of the camera. The viewfinder 203 has an eyepiece 114 shown in FIG. The user can observe the subject by looking through the viewfinder 203.
FIG. 3 is a schematic diagram of a secondary imaging system of the AF optical system. The light beam reflected by the sub mirror 116 is imaged on the primary image plane. The light beam of the subject imaged on the primary imaging surface is condensed by the condenser lens 117, reflected by the total reflection mirror 118, and then divided into four pupils by the separator diaphragm 119, for example. The luminous flux of the subject divided by the separator diaphragm 119 is collected by the separator lens 120 and enters a predetermined region of each of the light receiving surfaces 121a to 121d of the AF sensor 121 disposed behind the AF optical system.

  The AF sensor 121 includes a plurality of pairs of line sensors corresponding to distance measuring points. For example, the line sensor having the light receiving surface 121a and the line sensor having the light receiving surface 121b constitute a pair of line sensors, and the line sensor having the light receiving surface 121c and the line sensor having the light receiving surface 121d constitute a pair of line sensors. Configure. Each line sensor of the AF sensor 121 is formed by arranging a plurality of pixels in a line to form a single-row sensor array, and arranging the sensor arrays in parallel. Note that the sensor array in one column is composed of, for example, 42 pixels.

  4A and 4B show the principle of distance measurement in the optical system from the AF sensor 121 and the focus lens 102 to the separator lens 120. FIG. The light beam from the subject imaged on the primary imaging plane Q by the focus lens 102 is collected by the condenser lens 117, divided into pupils by the separator diaphragm 119, and each light receiving element arranged on the AF sensor 121 by the separator lens 120. Re-imaging is performed on the surfaces 121a to 121d. The formed subject image is converted into a video signal by a pair of sensor arrays SA and SB having respective light receiving surfaces 121a to 121d on the AF sensor 121. The pair of sensor arrays SA and SB is a one-row sensor array in each line sensor having the respective light receiving surfaces 121a and 121b. However, the AF sensor 121 has a pair of sensor arrays SA, SB, etc. each composed of a plurality of pixels, and converts and outputs a subject image having a parallax divided into pupils into a pair of video signals.

FIGS. 4A and 4B show a state in which the two-image interval Z of the video signal converted by the pair of sensor arrays SA and SB coincides with the two-image interval Z0 at the time of focusing. In this way, if the two-image interval Z coincides with the two-image interval Z0 at the time of focusing, the in-focus state (in focus) is indicated.
5 (a) and 5 (b), the two-image interval Z of the video signal converted by the pair of sensor arrays SA and SB is narrower than the two-image interval Z0 at the time of focusing, and is focused on the near side of the subject. The state of the so-called front pin that matches is shown.
6A and 6B, the two-image interval Z of the video signal converted by the pair of sensor arrays SA and SB is wider than the two-image interval Z0 at the time of focusing, and the focus is behind the subject. The state of the so-called rear pin that matches is shown.

  However, the AF controller 122 obtains a two-image interval Z of video signals in the pair of sensor arrays SA and sensor array SB on the AF sensor 121. The change in the shift amount of the two-image interval Z is proportional to the focus shift amount. The AF controller 122 obtains the feed amount of the focus lens 102 based on the shift amount.

Next, a method for calculating the defocus amount will be described.
The AF controller 122 calculates a defocus amount corresponding to the two-image interval value of the subject image based on the paired video signals output from the AF sensor 121. That is, the AF controller 122 determines the shift of the focus of the subject image formed by the focus lens 102, that is, the shift amount of the two image intervals Z of the video signals in the pair of sensor array SA and sensor array SB on the AF sensor 121. The focus shift of the subject image formed by the first focus detection means for detecting and the focus lens 102, that is, the two-image interval Z of the video signal between the pair of sensor arrays SA and SB on the AF sensor 121. Each function of the second focus detection means for detecting the amount of deviation in a range different from that of the first focus detection means.

  Among these, the second focus detection unit of the AF controller 122 detects focus shift in a wide range including a detection range of focus shift by the first focus detection unit. That is, as shown in FIG. 7, the first focus detection means of the AF controller 122 sets each correlation detection block Ha formed in a block width, for example, 24 pixels, in a pair of sensor array SA and sensor array SB. Then, the position where the correlation value between the correlation detection blocks Ha is highest is detected as the focus position while shifting the correlation detection blocks Ha.

  On the other hand, the second focus detection means of the AF controller 122 is formed in a pair of sensor array SA and sensor array SB with a block width narrower than the correlation detection block Ha, for example, 15 pixels, as shown in FIG. Each detected correlation detection block Hb is set, and the position where the correlation value between the correlation detection blocks Hb is highest is detected as a focus position while shifting the correlation detection blocks Hb.

  At this time, the AF controller 122 forms the correlation detection blocks Ha and Hb with respect to the pair of sensor arrays SA and SB, respectively, and shifts the correlation detection block Ha with respect to one sensor array SB. The position where the correlation value between the correlation detection blocks Ha and Hb is the highest is detected as the focus position, and the first focus detection means detects the focus shift of the subject image and is larger than the size of the correlation detection block Ha. The size of the correlation detection block Hb when the focus shift of the subject image is detected by the second focus detection means is reduced.

  However, the AF controller 122 uses the second focus detection unit to form the correlation detection block Hb (for example, 15 pixels) rather than the pixel number (for example, 24 pixels) to form the correlation detection block Ha by the first focus detection unit. ) Is set to be small, and the range in which the correlation detection block Hb is shifted with respect to the pair of sensor arrays SA and SB is widened. That is, in the first focus detection unit, the range in which the correlation detection block Ha shifts is, for example, 16 pixels as shown in FIG. 7, whereas in the second focus detection unit, the range in which the correlation detection block Hb shifts. As shown in FIG. 8, the number of pixels becomes, for example, 25 pixels, and the shift range becomes wider than 16 pixels of the first focus detection unit.

  The system controller 123 has a function as a focus adjustment unit that adjusts the position of the focus lens 102 based on the focus detection result by the first focus detection unit or the second focus detection unit of the AF controller 122. If the first focus detection unit 122 cannot detect the focus shift, the focus lens 102 is moved in the direction of arrow A with respect to the lens driving unit 103 based on the detection result of the second focus detection unit. A command for adjusting the position of the lens 102 is issued.

A defocus amount calculation method will be specifically described.
The defocus amount calculation method by the first focus detection unit as shown in FIG. 7 is a highly accurate method with a narrow defocus range, whereas the second focus as shown in FIG. 8 is used. The calculation method of the defocus amount by the detection unit is a method that is more likely to be erroneously detected than the first focus detection unit having a wide defocus range.

As described above, the AF sensor 121 has a pair of sensor arrays SA and SB of 42 pixels, for example, for each distance measuring point. The AF controller 122 detects a shift between the two images by detecting a position having the highest correlation between the data read from the pair of sensor arrays SA and SB.
As shown in FIG. 7, the width of the correlation detection block Ha for a pair of sensor array SA and sensor array SB is 24 pixels, and the AF controller 122 uses the data of the correlation detection block Ha of the sensor array SA and the sensor array. When calculating the correlation value with the data of the SB correlation detection block Ha, the correlation value is calculated while shifting the correlation detection block Ha on the sensor array SB side by one pixel. The correlation value is calculated by calculating a product sum of the differences between the corresponding pixels of the pair of sensor arrays SA and sensor array SB, and the smallest combination has the highest correlation. If the highest correlation value is in the same pixel position in the pair of sensor array SA and sensor array SB, focusing is performed.

  The defocus amount calculation method by the first focus detection unit as shown in FIG. 7 detects a focus shift toward the infinite end. In order to detect a focus shift toward the closest end by this method, it is possible to fix the sensor array SB and shift the correlation detection block Ha on the sensor array SA side. However, in this method, the position of the correlation detection block Ha on the sensor array SB side is shifted from the position where the waveform of the pixel data appears, and the waveform of the pixel data is detected from the correlation detection block Ha on the sensor array SB side. The correlation cannot be detected.

  On the other hand, in the method of calculating the defocus amount by the second focus detection unit as shown in FIG. 8 above, the width of the correlation detection block Hb is 15 pixels. For example, the number of pixels is increased by 9 pixels from the shift range (16 pixels) of the first focus detection unit to 25 pixels. As a result, the defocus detection range by the second focus detection unit is increased by about 1.5 times the defocus detection range by the first focus detection unit. As a result, the defocus amount calculation method by the second focus detection unit can detect the defocus in a range from 17 pixels to 25 pixels, for example, which could not be detected by the first focus detection unit. Therefore, in the defocus amount calculation method by the second focus detection means, the waveform of the pixel data that could not be detected by the first focus detection means can be detected by shifting the correlation detection block Hb to the focus detection position G. .

  FIG. 9 shows the relationship between the defocus range and the focus adjustment range. In the figure, f indicates a focal length, and fw indicates a focus adjustment range. This focus adjustment range fw is normally adjusted between f and f × 2. df1 and df2 indicate a defocus range. Among these, the defocus range df1 indicates a range in which a focus shift can be detected by the setting of the correlation detection block Ha shown in FIG. The defocus range df2 indicates a range in which a focus shift can be detected by setting the correlation detection block Hb shown in FIG.

Next, the AF operation of the camera configured as described above will be described with reference to the flowchart of the AF sequence shown in FIG.
First, when the AF operation is started, the AF sensor 121 starts accumulating charges in step S101 according to an instruction from the AF controller 122.

Next, the AF controller 122 reads sensor data from the AF sensor 121 in step S102, and determines whether or not the contrast exceeds a predetermined threshold from the sensor data in the next step S103.
As a result of the determination, if the contrast exceeds a predetermined threshold, the AF controller 122 proceeds to step S104 and performs the first correlation calculation. As shown in FIG. 7, the first correlation calculation is performed by shifting the correlation detection block Ha on the sensor array SB side by one pixel and the data of the correlation detection block Ha of the sensor array SA and the sensor array SB. A correlation value with the data of the correlation detection block Ha is calculated. The correlation value is calculated by calculating a product sum of differences between corresponding pixels of the pair of sensor arrays SA and sensor array SB, and the smallest combination has the highest correlation. If the highest correlation value is in the same pixel position in the pair of sensor array SA and sensor array SB, focusing is performed.
If the contrast does not exceed the predetermined threshold value, the AF controller 122 shifts to the sensor operation condition change flowchart shown in FIG. 11 and changes the operation condition of the AF sensor 121.

Next, in step S105, the AF controller 122 determines whether or not there is a correlation between the pair of sensor arrays SA and the sensor array SB, that is, minimizes between the pair of sensor arrays SA and the sensor array SB. It is determined whether or not there is the highest correlation in the combination.
If there is a correlation as a result of the determination, the AF controller 122 proceeds to step S106 and calculates the defocus amount. That is, the AF controller 122 obtains the two image intervals Z of the video signals in the pair of sensor arrays SA and sensor array SB on the AF sensor 121, and focuses based on the defocus amount that is the deviation amount of the two image intervals Z. The feeding amount of the lens 102 is obtained.

  Next, in step S <b> 107, the system controller 123 issues a defocus drive command to the lens CPU 104 for moving the focus lens 102 to the in-focus position based on the defocus amount obtained by the AF controller 122. Accordingly, the lens CPU 104 outputs a pulse signal to the lens driving unit 103 to drive and control the lens driving unit 103. The lens driving unit 103 drives the DC motor by a pulse signal from the lens CPU 104 to move the focus lens 102 in the arrow A direction.

  Next, in step S108, the system controller 123 determines whether or not the calculated defocus amount is within the close-up focusing range. This close-in focus range is a range where the defocus amount is small and the focus lens 102 can be reliably stopped at the focus position. In general, the defocus amount is corrected by the characteristics of the optical system such as the focus lens 102. An approximate value is used as the correction value. Therefore, when the defocus amount is large, the error due to approximation of the correction value tends to increase. If the error due to the factor in the defocus calculation is within the depth of focus, it can be ignored and it can be determined that the close-in focus is achieved.

  As a result of determining whether or not the defocus amount is within the close-up focus range, if the defocus amount is within the close-up focus range, the system controller 123 ends the AF operation. If the defocus amount is not within the close-up focusing range, the system controller 123 returns to step S101.

  On the other hand, as a result of determining whether or not there is a correlation between the pair of sensor arrays SA and sensor array SB in step S105, if there is no correlation, the AF controller 122 proceeds to step S109 and performs the second correlation. Perform the operation. As shown in FIG. 8, the second correlation calculation is performed by setting the width of the correlation detection block Hb to 15 pixels, for example, while shifting the correlation detection block Hb on the sensor array SB side, for example, pixel by pixel. A correlation value between the data of the correlation detection block Hb of the sensor array SA and the data of the correlation detection block Hb of the sensor array SB is calculated. As described above, the correlation value is calculated by calculating a product sum of differences between corresponding pixels of the pair of sensor array SA and sensor array SB, and the smallest combination has the highest correlation. If the highest correlation value is in the same pixel position in the pair of sensor array SA and sensor array SB, focusing is performed.

Next, in step S110, the AF controller 122 determines whether or not there is a correlation between the pair of sensor arrays SA and the sensor array SB, that is, minimizes between the pair of sensor arrays SA and the sensor array SB. It is determined whether or not there is the highest correlation in the combination.
If there is a correlation as a result of this determination, the AF controller 122 proceeds to step S111, obtains a two-image interval Z of the video signal in the pair of sensor arrays SA and sensor array SB on the AF sensor 121, and this two-image interval. The defocus amount of the focus lens 102 is calculated based on the defocus amount that is the Z shift amount.

Next, in step S112, the system controller 123 issues a defocus drive command for moving the focus lens 102 to the in-focus position based on the defocus amount obtained by the AF controller 122 to the lens CPU 104. Accordingly, the lens CPU 104 outputs a pulse signal to the lens driving unit 103 to drive and control the lens driving unit 103. The lens driving unit 103 drives the DC motor by a pulse signal from the lens CPU 104 to move the focus lens 102 in the arrow A direction. Then, the system controller 123 returns to step S101.
If there is no correlation between the pair of sensor arrays SA and SB as a result of the determination in step S110, the system controller 123 proceeds to scan AF.

  On the other hand, if the contrast does not exceed the predetermined threshold as a result of the determination in step S103, the AF controller 122 proceeds to step S104 and proceeds to the sensor operation condition change flowchart shown in FIG. To change. In the sensor operation condition change flowchart, the sensitivity of the AF sensor 121 and the gain at the time of reading are set according to the brightness of the subject.

That is, the AF controller 122 determines whether or not the sensitivity of the AF sensor 121 is maximum in step S201. If the sensitivity is not the maximum as a result of this determination, the AF controller 122 proceeds to step S202, increases the sensitivity of the AF sensor 121, and returns to the AF start shown in FIG.
If the sensitivity is maximum, the AF controller 122 proceeds to step S203 and determines whether or not the read gain for the AF sensor 121 is maximum. If the readout gain is maximum as a result of this determination, the AF controller 122 moves to scan AF. If the read gain is not the maximum, the AF controller 122 proceeds to step S204, increases the read gain of the AF sensor 121, and returns to the AF start shown in FIG.

  As described above, according to the embodiment, the first focus detection unit of the AF controller 122 shifts the correlation detection block Ha to the pair of sensor array SA and sensor array SB as shown in FIG. When the position where the correlation value between the correlation detection blocks Ha is the highest is detected as the focus position, and the focus shift cannot be detected by the first focus detection means, the second focus detection means shows in FIG. As described above, the position where the correlation value between the correlation detection blocks Hb is highest is detected as the focus position while shifting the correlation detection blocks Hb narrower than the correlation detection block Ha to the pair of sensor arrays SA and SB. To do.

  Thus, in the defocus amount calculation method by the second focus detection unit, the shiftable range of the correlation detection block Hb can be made wider than the shift range of the first focus detection unit, and the first focus detection unit detects the defocus amount. Defocusing can be detected in the range where it was impossible. Therefore, as shown in FIG. 8, in the method of calculating the defocus amount by the second focus detection unit, the waveform of the pixel data that could not be detected by the first focus detection unit is set to the focus detection position G with the correlation detection block Hb. It can be detected by shifting. As a result, by widening the defocus range, the possibility of shifting to scan AF can be reduced, the time until focusing can be shortened, and the possibility of missing a photo opportunity can be reduced.

  When the first focus detection unit cannot detect the focus shift, the second focus detection unit detects the focus shift. Therefore, the detection result of the first focus detection unit with higher reliability can be obtained. Priority can be given.

  Although the present invention has been described based on the above-described embodiment, the present invention is not limited to the above-described embodiment, and various modifications and applications are possible within the scope of the gist of the present invention. Of course.

  Further, the above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be extracted as an invention.

The block diagram which shows one Embodiment of the digital single-lens reflex camera as an imaging device provided with the auto-focus adjustment apparatus which concerns on this invention. The external appearance perspective view of the camera. FIG. 3 is a schematic diagram showing a secondary imaging system of an AF optical system in the camera. The figure which shows the state at the time of the focus of the 2 image space | interval of the video signal converted by the principle of ranging in the optical system from the AF sensor and the focus lens to the separator lens in the camera, and a pair of sensor arrays. The figure which shows the state of what is called the front pin where the 2 image space | interval of the video signal converted by a pair of sensor array in the same camera is narrower than the 2 image space | interval at the time of focusing, and it is focusing on the near side rather than the to-be-photographed object. The figure which shows the state of what is called a rear pin which the two image space | intervals of the video signal converted by the pair of sensor array in the same camera is wider than the two image space | interval at the time of focusing, and is focused on the back side rather than a to-be-photographed object. The figure which shows the calculation method of the defocus amount by the 1st focus detection means of AF controller in the camera. The figure which shows the calculation method of the defocus amount by the 2nd focus detection means of AF controller in the camera. The figure which shows the relationship between the defocus range and focus adjustment range in the camera. The flowchart of the AF sequence in the camera. The sensor operation condition change flowchart in the camera.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101: Interchangeable lens, 110: Camera body, 102: Focus lens, 103: Lens drive part, 104: Lens CPU, 105: Communication connector, 106: Focus adjustment mechanism, 107: Encoder, 111: Main mirror, 112: Focusing screen , 113: pentaprism, 114: eyepiece lens, 116: sub mirror, 117: condenser lens, 118: total reflection mirror, 119: separator diaphragm, 120: separator lens, 121: AF sensor, 122: AF controller, 123: system controller 124: Image sensor, 125: Display unit, 126: Memory card, 127: Rotary switch, 128: Release button, 129: Setting switch, 205: Focus ring, 203: Viewfinder, 121a to 121 : Light-receiving surface of the AF sensor, SA, SB: 1 pair of sensor arrays.

Claims (5)

An optical system for forming a subject image;
First focus detection means for detecting a focus shift of the subject image formed by the optical system;
Second focus detection means for detecting a focus shift of the subject image formed by the optical system in a range different from the first focus detection means;
A focus adjustment unit that adjusts a position of the optical system based on a focus detection result by the first focus detection unit or the second focus detection unit;
A focus adjusting apparatus comprising: The second focus detection unit detects the focus shift in a wide range including a detection range of the focus shift by the first focus detection unit;
The focus adjusting unit adjusts the position of the optical system based on a detection result of the second focus detecting unit when the focus shift cannot be detected by the first focus detecting unit;
The focus adjusting apparatus according to claim 1, wherein: The first and second focus detection means each have a pair of line sensors each composed of a plurality of pixels, and convert and output the subject image having a parallax that is divided into pupils into a video signal that forms a pair. When,
Defocus amount calculating means for calculating a defocus amount according to a two-image interval value of the subject image based on the paired video signals output from the autofocus sensor;
Have
The defocus amount calculation unit forms each correlation detection block for each of the pair of line sensors, and shifts the correlation detection block with respect to one of the line sensors while correlating the correlation values between the correlation detection blocks. Is detected as the focus position, and the second focus detection means is larger than the size of the correlation detection block when the first focus detection means detects the focus shift of the subject image. Forming a small size of the correlation detection block when detecting the focus shift of the subject image;
The focus adjusting apparatus according to claim 1, wherein:   The defocus amount calculation means sets the number of pixels forming the correlation detection block by the second focus detection means to be smaller than the number of pixels forming the correlation detection block by the first focus detection means. 4. The focus adjustment apparatus according to claim 3, wherein a range of shifting with respect to the line sensor of the correlation detection block is widened.   An imaging apparatus comprising the focus adjustment apparatus according to any one of claims 1 to 4.

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