JP5065466B2 - Focus detection apparatus and optical instrument - Google Patents

Description

  The present invention relates to a focus detection apparatus having a sensor means composed of a plurality of photoelectric conversion elements, and an improvement in an optical apparatus such as a camera or a mobile phone provided with the focus detection apparatus.

Conventionally, as a focus detection device of a camera, a light beam from a subject that has passed through different exit pupil regions of a photographing lens is imaged on a pair of line sensors, and a pair of subject images obtained by photoelectric conversion of the subject image is obtained. There is a so-called phase difference detection type focus detection device that detects a defocus amount of a subject by calculating a displacement amount of a relative position (hereinafter referred to as a phase difference calculation) and drives a photographing lens based on the detected defocus amount. Known (Patent Document 1).
Also, with this type of focus detection device, a pair of line sensors is divided into a plurality of regions, signal accumulation control is performed for each region, and a pair of subject images obtained by photoelectric conversion in each region are subjected to correlation calculation. Thus, a multi-point focus detection apparatus that performs focus detection on a plurality of subjects is also known (Patent Document 2).
Further, in the focus detection device of the phase difference detection method, the focus detection device capable of adjusting the defocus amount that can be detected by changing the region used in the accumulation control and the phase difference calculation of the pair of line sensors. Is also known (Patent Document 3).

Japanese Patent Laid-Open No. 09-054242 JP 2003-215442 A Japanese Unexamined Patent Publication No. 63-172206 (FIG. 8 etc.)

  By the way, the focus detection device disclosed in Patent Document 3 makes it possible to select an appropriate accumulation control region according to the focus detection result and the maximum defocus amount of the photographing lens. However, when focus detection is impossible, it is necessary to change the accumulation control region and perform the accumulation operation and the calculation operation again, which causes a problem that the time required for focus detection becomes long.

  Further, the focus detection device disclosed in Patent Literature 3 can be applied to a multipoint focus detection device that enables focus detection of a plurality of subjects, such as the focus detection device disclosed in Patent Literature 2. In this case, when the accumulation control area is narrow, adjacent areas do not overlap. However, when the accumulation control area is wide, adjacent areas overlap. Since the overlapping areas cannot be accumulated at the same time, the accumulation operation is performed for each area, and the time required for focus detection becomes longer.

(Object of invention)
A first object of the present invention is to provide a focus detection apparatus and an optical apparatus that can change the size of a plurality of regions of a sensor means without waiting for a focus detection result.

  The second object of the present invention is to achieve the first object and to perform re-accumulation in the enlarged area even when it is necessary to enlarge the area of the sensor means and detect the defocus state. It is an object of the present invention to provide a focus detection device and an optical apparatus that can eliminate the need for the above and reduce the detection time.

  A third object of the present invention is to provide a focus detection apparatus and an optical apparatus that can achieve the second object and can perform appropriate focus detection in each region.

  A fourth object of the present invention is to achieve the second object and to provide a focus detection device and an optical apparatus capable of performing appropriate focus detection in each region even when the focus detection target has a low luminance. Is to provide.

To achieve the above SL fourth object, an invention according to claim 1, it communicates with the imaging lens including a focus lens, the position information of the maximum defocus amount and the current focus lens that may occur in the photographing lens A pair of first line sensors and a second line sensor for receiving and photoelectrically converting a different pair of light beams among the light beams passing through the photographing lens and outputting an image signal; In the center of the pair of third line sensor and fourth line sensor, the first line sensor and the second line sensor, the maximum defocus amount of the photographing lens and the current focus lens position information A central region having a size based on the central region, and peripheral regions are set in the remaining regions on the left and right of the central region, and the third line sensor and the And setting means for setting a peripheral area of each of the four line sensors and setting a central area for each remaining area of the peripheral area, and performing accumulation control of image signals in the central area set by the setting means. And an accumulation control means for controlling the accumulation of image signals in the peripheral area set by the setting means, and the central area set for the first line sensor and the second line sensor by the setting means. The defocus amount of the central area based on the shift amount of the obtained image signal, and the images obtained in the central area set in the third line sensor and the fourth line sensor by the setting unit, respectively. The defocus amount of the central area based on the signal shift amount, and the first line sensor and the second line sensor are set. Obtained in the defocus amount of the peripheral region based on the shift amount of the image signal obtained in each of the peripheral regions, and obtained in the peripheral region set in the third line sensor and the fourth line sensor, respectively. Detecting means capable of detecting a defocus amount of the peripheral area based on a deviation amount of the image signal, and the setting means includes the first line sensor controlled by the accumulation control means, the first line sensor, When the accumulation time of image signals in the second line sensor, the third line sensor, and the fourth line sensor is longer than a predetermined accumulation time, the center of the first line sensor and the second line sensor The area is reset so that the size of the area is the same as the size of the central area of the third line sensor and the fourth line sensor. And

  According to the present invention, it is possible to provide a focus detection device or an optical apparatus that can change the size of a plurality of regions of the sensor means without waiting for a focus detection result.

  Further, the present invention eliminates the need for re-accumulation in the enlarged area and shortens the detection time even when it is necessary to enlarge the area of the sensor means and detect the defocus state. A focus detection apparatus or an optical instrument can be provided.

  In addition, according to the present invention, it is possible to provide a focus detection apparatus or an optical apparatus that can perform appropriate focus detection in each region.

  Furthermore, according to the present invention, it is possible to provide a focus detection apparatus or an optical apparatus that can perform appropriate focus detection in each region even when the focus detection target has low luminance.

It is a block diagram which shows the circuit structure of the camera concerning Example 1 of this invention. 1 is a layout diagram of an optical system of a camera according to Embodiment 1 of the present invention. 1 is an optical configuration diagram of a phase difference type focus detection device provided in a camera according to Embodiment 1 of the present invention. FIG. It is a figure which shows the sensor array (line sensor) of the AF sensor of the phase difference system concerning Example 1 of this invention. It is the figure which showed the positional relationship of the ranging point and AF visual field concerning Example 1 of this invention. It is a block diagram which shows the structure of the AF sensor concerning Example 1 of this invention. It is a figure which shows an example of a pixel structure of the AF sensor concerning Example 1 of this invention. It is a figure for demonstrating the control method of PB signal and accumulation time concerning Example 1 of this invention. It is a flowchart for demonstrating operation | movement of the focus detection apparatus concerning Example 1 of this invention. It is a figure for demonstrating the detection method of the maximum defocusing amount from the lens information concerning Example 1 of this invention. It is the figure which showed an example of the relationship between the phase difference concerning the Example 1 of this invention, and a defocus position. It is the figure which showed the division | segmentation method of the accumulation | storage control area | region in the sensor array concerning Example 1 of this invention. It is a block diagram which shows the circuit structure of the camera concerning Example 2 of this invention. It is a figure which shows the sensor array of the AF sensor of the phase difference system concerning Example 2 of this invention. It is the figure which showed the positional relationship of the ranging point and AF visual field concerning Example 2 of this invention. It is a block diagram which shows the structure of the AF sensor concerning Example 2 of this invention. It is a flowchart for demonstrating operation | movement of the focus detection apparatus concerning Example 2 of this invention. It is the figure which showed the division | segmentation method of the accumulation | storage control area | region in the sensor array concerning Example 2 of this invention.

  The best mode for carrying out the present invention is as described in Examples 1 and 2 below.

  FIG. 1 is a block diagram showing a circuit configuration of a camera according to Embodiment 1 of the present invention. In FIG. 1, a camera microcomputer (hereinafter referred to as CPU) 100 includes a switch group 214 for various operations of the camera. Are connected to a signal input circuit 204, an image sensor 206, an AE sensor 207, a shutter control circuit 208 for controlling shutter magnets 218a and 218b, and an AF sensor 101. In addition, a signal 215 is transmitted to a later-described photographic lens via a lens communication circuit 205 to control a focal position and an aperture. The operation of the camera is determined by the setting of the switch group 214.

  The AF sensor 101 is provided with a pair of line sensors, and the CPU 100 controls the AF sensor 101 to detect the defocus amount from the contrast distribution of the subject obtained by the line sensor, and the focus of the photographing lens. Control the position. Further, the CPU 100 controls the AE sensor 207 to detect the luminance of the subject, and determines the aperture value and shutter speed of the photographing lens. The aperture value on the photographing lens side is controlled via the lens communication circuit 205, the energization time of the shutter magnets 218a and 218b is controlled via the shutter control circuit 208, and the shutter speed is controlled. The shooting operation is performed by controlling.

  The CPU 100 has a built-in storage circuit 209 such as a ROM storing a program for controlling camera operations, a RAM for storing variables, and an EEPROM (electrical erasable and writable memory) for storing various parameters. Yes.

  Next, the arrangement relationship of the optical system of the camera will be described with reference to FIG.

  Most of the light beam from the subject incident through the photographing lens 300 is reflected upward by the quick return mirror 305 and forms an image on the finder screen 303. The user of the camera observes this image through the pentaprism 301 and the eyepiece lens 302. A part of the photographing light beam passes through the quick return mirror 305, is bent downward by the rear sub-mirror 306, and is coupled onto the AF sensor 101 through the field mask 307, the field lens 311, the diaphragm 308, and the secondary imaging lens 309. Image. The focus state of the photographic lens 300 can be detected by processing an image signal obtained by photoelectrically converting this image. At the time of shooting, the quick return mirror 305 jumps up, and the entire luminous flux is imaged on the image sensor 206, and the subject image is exposed.

  The focus detection method in the focus detection apparatus according to the first exemplary embodiment (in FIG. 2, which includes the field mask 307 to the secondary imaging lens 309 and the AF sensor 101) is a well-known phase difference detection method. It is possible to detect the focus state of a plurality of different areas.

  FIG. 3 shows a detailed configuration of an optical system related to focus detection. The light beam from the subject that has passed through the photographing lens 300 is reflected by the sub-mirror 306 (see FIG. 2), and once forms an image in the vicinity of the field mask 307 on a plane conjugate with the imaging surface. In FIG. 3, the optical path reflected by the sub-mirror 306 and turned back is developed. The field mask 307 is a member for shielding extra light other than a focus detection area (hereinafter also referred to as a distance measuring point) in the screen.

  The field lens 311 has an effect of forming each aperture of the diaphragm 308 in the vicinity of the exit pupil of the photographing lens 300. A secondary imaging lens 309 is disposed behind the stop 308 and is composed of a pair of two lenses. Each lens corresponds to each opening of the stop 308. Each light beam that has passed through the field mask 307, the field lens 311, the stop 308, and the secondary imaging lens 309 forms an image on a line sensor (sensor array) on the AF sensor 101. Further, the line sensor in the AF sensor 101 is configured so as to be able to form images of light beams from different subjects in the photographing screen.

  Here, the positional relationship between the arrangement of the line sensors in the AF sensor 101 and the distance measuring points in the shooting screen will be described with reference to FIGS. 4 and 5.

  FIG. 4 is a diagram showing the arrangement of the line sensors in the AF sensor 101. In the AF sensor 101, line sensors 111a and 111b formed in a pair of lines are arranged.

  FIG. 5 is a diagram showing the arrangement of distance measuring points displayed in the viewfinder and the range of the AF visual field by the line sensors 111a and 111b on the AF sensor 101. As shown in FIG. Three AF points, ranging point L, ranging point C, and ranging point R, are arranged on the AF field of view, and focus detection is possible for three different subjects corresponding to each ranging point. It has become.

  A detailed circuit configuration of the AF sensor 101 will be described with reference to a block diagram of FIG.

  The subject image formed by the secondary imaging lens 309 is photoelectrically converted by the line sensors 111a and 111b. The line sensors 111a and 111b are configured by arranging a plurality of pixels in a line, and signals that are photoelectrically converted and converted into voltages in each pixel are stored in the storage circuits 102a and 102b. The area selection circuit 103 has a function of dividing the signal accumulated in the accumulation circuit 102a into a maximum of three areas and allocating the accumulated signal in each area to the PB contrast detection circuits 104a, 104b, and 104c.

  The PB contrast detection circuits 104a, 104b, and 104c detect the largest signal (hereinafter referred to as Peak signal) and the smallest signal (hereinafter referred to as Bottom signal) in the range of pixel signals selected by the region selection circuit 103. Then, a difference signal between the Peak signal and the Bottom signal (hereinafter referred to as a PB signal) is output to the accumulation stop determination circuit 105. Here, the PB signals detected by the PB contrast detection circuits 104a, 104b, and 104c are PB1, PB2, and PB3, respectively.

  The accumulation stop determination circuit 105 compares the PB signals PB1, PB2, and PB3 with the target values, and stops the accumulation of pixels in the range selected by the region selection circuit 103 when it becomes larger than the target values. An accumulation stop signal is output to the accumulation circuits 102a and 102b. When the accumulation is stopped in any of the areas, the accumulation end signal and the information on the area where the accumulation is completed are output to the CPU 100. The pixel signals accumulated in the accumulation circuits 102 a and 102 b are output to the output circuit 107 as pixel signals for each pixel by driving the shift register 106 by the CPU 100. The output circuit 107 performs a process such as amplifying the pixel signal and outputs it to an AD converter (not shown) of the CPU 100.

  Here, an example when the line sensors 111a and 111b are divided into three regions will be described with reference to FIGS.

  In FIG. 7, each of the line sensors 111a and 111b is composed of 120 pixels, and the accumulated signal of the first pixel of the line sensor 111a is SA1, and the accumulated signal of the nth pixel is SAn. Further, the accumulation signal of the first pixel of the line sensor 111b is SB1, and the accumulation signal of the nth pixel is SBn.

  Here, the region selection circuit 103 causes the pixel signal in the range of SA1 to SA40 to be sent to the PB contrast detection circuit 104a, the accumulated signal in the range of SA41 to SA80 to the PB contrast detection circuit 104b, and the accumulated signal of SA81 to SA120 to be the PB contrast. The area is selected (assigned) so as to be input to the detection circuit 104c.

  FIG. 8 is a diagram showing the relationship between the signal amount of PB signals PB1, PB2, and PB3, which are output signals from the PB contrast detection circuits 104a, 104b, and 104c, and the accumulation time. The accumulation time 0 is the accumulation start timing, and the PB signal increases as time elapses. The increase rate of the PB signal varies depending on the brightness and contrast of the subject existing in each area. The PB signal is compared with the stop level by the storage stop determination circuit 105. Assuming that the timing when the PB signal becomes equal to or higher than the stop level is T1, T2, and T3, accumulation of pixel signals corresponding to the areas SA1 to SA40 and SB1 to SB40 input to the PB contrast detection circuit 104a is stopped at the timing of T1. To do. At the timing T2, the accumulation of pixel signals corresponding to the areas SA41 to SA80 and SB41 to SB80 input to the PB contrast detection circuit 104b is stopped. Further, at the timing of T3, accumulation of pixel signals corresponding to the areas SA81 to SA120 and SB81 to SB120 input to the PB contrast detection circuit 104c is stopped.

  As described above, by detecting the PB signal representing the contrast of the subject image for each divided area and performing accumulation until the signal reaches a predetermined level or more, optimal accumulation control can be performed in each area.

  The operation of the focus detection apparatus configured as described above will be described in detail based on the flowchart of FIG.

  When a focus detection start signal is received by operating the switch group 214, the focus detection operation by the AF sensor 101 is started. First, in step S701, the lens communication circuit 205 communicates with the photographic lens 300, and is attached to the photographic lens. The maximum defocus amount that can occur at 300 and the current focus lens position are detected. In the next step S702, the maximum defocus amount that can occur during focus detection is calculated from the maximum defocus amount and focus lens position information of the photographing lens 300 detected in step S701.

  Here, a method of calculating the maximum defocus amount that can occur during focus detection will be described. FIG. 10 shows the positional relationship between the maximum defocus of the lens A and the lens B and the focus lens positions P and P ′. In this figure, the maximum defocus amount of the lens A is narrower than the maximum defocus amount of the lens B.

  The amount of defocus that can occur in focus detection is the difference from the focus lens position to the maximum defocus position of the lens (infinite end side), and from the focus lens position to the maximum defocus position of the lens (closest end side). The greater of the difference amounts.

  In the lens A, in the case of the focus lens position P, APmax which is a difference amount from the position P to the defocus limit position in the closest direction is the maximum defocus amount that can be generated. On the other hand, in the case of the focus lens position P ′, AP′max which is the difference amount from the position P ′ to the defocus limit position in the infinite direction is the maximum defocus amount that can be generated.

  In the lens B, in the case of the focus lens position P, BPmax which is a difference amount from the position P to the defocus limit position in the closest direction is the maximum defocus amount that can be generated. On the other hand, in the case of the focus lens position P ′, BP′max, which is the difference amount from the position P ′ to the defocus limit position in the infinite direction, is the maximum defocus amount that can be generated.

  As described above, the maximum defocus amount that can occur varies depending on the type of lens and the focus lens position.

  Returning to the flowchart of FIG. 9, in the next step S703, the accumulation control region by the region selection circuit 103 is set based on the maximum defocus amount that can occur at the time of focus detection calculated in step S702.

  Here, the accumulation control region setting method will be described with reference to FIGS. 11 and 12. FIG.

  FIG. 11 is a diagram showing the relationship between the phase difference (deviation amount) of the subject images obtained by the line sensor 111a and the line sensor 111b and the defocus amount. This relationship can be expressed almost linearly, and the inclination is determined by the optical system of the focus detection system. Originally, the defocus amount is calculated from the phase difference of the obtained subject image. Conversely, the maximum phase difference that can be generated by the subject image can be calculated from the maximum defocus amount calculated in step S702. When the accumulation control area is smaller than the maximum phase difference, the subject image protrudes from the area at the maximum phase difference, and the phase difference cannot be detected. Therefore, the accumulation control area needs at least the maximum phase difference amount of the subject image. Here, the accumulation control region is determined by adding a predetermined margin amount to the maximum phase difference.

  FIG. 12A shows the L region, the C region, and the R region when the maximum defocus amount is small and the accumulation range calculated from the maximum phase difference is 1/3 or less of the sensor array length. The L region, the C region, and the R region are regions obtained by dividing the sensor array into three equal parts (the C region is limited so as not to be smaller than 1/3 of the sensor array length). FIG. 12B shows the L region, the C region, and the R region when the maximum defocus amount is large and the accumulation range calculated from the maximum phase difference is wider than 1/3 of the sensor array length. The C area expands more than 1/3 of the line according to the accumulation control area calculated from the maximum phase difference, and the L area and R area use portions other than those used for the C area. As described above, the region selection circuit 103 sends the pixel signal of the L region to the PB contrast detection circuit 104a, the pixel signal of the C region to the PB contrast detection circuit 104b, and the pixel signal of the R region to the PB contrast detection circuit 104c. Set to sort.

  As described above, an area for which accumulation control is performed is determined from information from the photographing lens 300, that is, information on the maximum defocus amount and the current focus lens position.

  Returning to the flowchart of FIG. 9 again, in the next step S704, the CPU 100 controls the AF sensor 101 to start the signal accumulation operation by the accumulation circuits 102a and 102b. In the next step S705, an accumulation stop determination operation is performed for the accumulation control region set in step S703. The CPU 100 detects an accumulation stop signal output from the AF sensor 101. Then, the operation of step S705 is repeated until the accumulation stop signal is detected. When the accumulation stop signal is detected, the process proceeds to the signal reading operation of step S706.

  In step S706, the pixel signal is read out from the area where the accumulation has been completed. By controlling the AF sensor 101 by the CPU 100, the pixel signals in the areas where the accumulation has been completed are sequentially output, and the pixel signals are AD-converted by an AD converter (not shown) in the CPU 100. Here, the AD-converted pixel signal is stored in the storage circuit 209. In the next step S707, it is determined whether the accumulation operation is completed in all the L region, C region, and R region, and the signal read operation is completed. If the read operation has been completed in all areas, the process proceeds to step S708. On the other hand, if there is an area where the read operation has not yet been completed, the process returns to the accumulation end determination operation in step S705, and thereafter the same operation is repeated.

  If the pixel signal read operation for all the L, C, and R regions has been completed, the process proceeds to step S708. Based on the pixel signals in the L, C, and R regions stored in the storage circuit 209, the process proceeds to step S708. Correlation calculation is performed to calculate the defocus amount in each region. Focus detection results corresponding to the L ranging point, the C ranging point to the C ranging point, and the R region to the R ranging point are obtained respectively. In the next step S709, based on the defocus amount calculated in step S708, the CPU 100 performs drive control of the focus lens of the photographic lens 300 via the lens communication circuit 205, and ends a series of focus detection operations.

  According to the first embodiment described above, an area for which accumulation control is performed is determined based on not only the maximum defocus amount that can be generated in the photographing lens 300 but also information on the focus lens position at that time, and the obtained area is obtained. Since the defocus amount is detected on the basis of the pixel signal, it is not necessary to perform a re-accumulation operation when changing the accumulation control area as in the conventional case, and the focus detection time is shortened. be able to.

  In addition, by applying the storage area range determined as described above to the central distance measurement area and using the remaining pixel range as the peripheral distance measurement area, the detection areas overlap (overlap). Since focus detection can be performed without unnecessarily widening the accumulation control range, focus detection error (conflict of perspective) due to a signal from the background of the subject can be prevented. It is also possible to perform focus detection for a plurality of subjects. That is, not only large defocus detection of one point (C area at the center of the screen) but also defocus detection of the surrounding distance measuring points (L area, R area) can be performed.

  Further, when the accumulation area range determined as described above is applied to the central distance measurement area, if the remaining pixel range is smaller than the predetermined range, focus detection is performed only in the central distance measurement area. Anyway. That is, the defocus detection of the surrounding distance measuring points (L region, R region) is not performed.

  The focus detection apparatus according to the first embodiment has a problem that when the C region is widened, the L region and the R region are narrowed and the defocus amount detection range is narrowed. Therefore, a technique for solving this problem will be described below as a second embodiment of the present invention.

  FIG. 13 is a block diagram showing a configuration of a camera according to Embodiment 2 of the present invention, and the same portions as those in FIG.

  The AF sensor 401 includes two pairs of line sensors. The CPU 100 includes a timer 400 for measuring the accumulation time in the AF sensor 401. Since other configurations are the same as those in FIG. 1, the description thereof is omitted.

  Here, the relationship between the line sensor on the AF sensor 401 and the distance measuring point in the shooting screen will be described with reference to FIGS. 14 and 15.

  FIG. 14 is a diagram showing the arrangement of the line sensors in the AF sensor 401. In the AF sensor 401, two pairs of line sensors 411a and 411b and line sensors 421a and 421b are arranged.

  FIG. 15 is a diagram showing the arrangement of ranging points displayed in the viewfinder, the range of the AF visual field 1 formed by the line sensors 411a and 411b, and the range of the AF visual field 2 formed by the line sensors 421a and 421b. . On the adjacent AF visual fields 1 and 2, three ranging points, ranging point L, ranging point C, and ranging point R, are arranged, and three ranging points corresponding to each ranging point are arranged. Focus detection is possible for different subjects.

  A detailed circuit configuration of the AF sensor 401 will be described with reference to a block diagram of FIG. The subject image formed by the secondary imaging lens 209 is photoelectrically converted by the line sensors 411a and 411b and the line sensors 421a and 421b. The line sensors 411a and 411b are configured by arranging a plurality of pixels in a line, and signals that are photoelectrically converted and converted into voltages in each pixel are stored in the storage circuits 402a and 402b. Similarly, the line sensors 421a and 421b are configured by arranging a plurality of pixels in a line, and the signals photoelectrically converted into voltages in each pixel are stored in the storage circuits 403a and 403b.

  The region selection circuit 404 divides the signal accumulated in the accumulation circuit 402a into a maximum of three regions, and distributes the accumulated signals in each range to the PB contrast detection circuits 406a, 406b, and 406c. The area selection circuit 405 divides the signal accumulated in the accumulation circuit 403a into a maximum of three areas, and distributes the accumulation signal in each area to the PB contrast detection circuits 407a, 407b, and 407c. The PB contrast detection circuits 406a, 406b, and 406c and the PB contrast detection circuits 407a, 407b, and 407c have the same functions as the PB contrast detection circuits 104a, 104b, and 104c in FIG.

  The accumulation stop determination circuit 408 outputs an accumulation stop signal to the accumulation circuits 402a and 402b based on the PB signals output from the PB contrast detection circuits 406a, 406b, and 406c. The accumulation stop determination circuit 409 outputs an accumulation stop signal to the accumulation circuits 403a and 403b based on the PB signal output from the PB contrast detection circuits 407a, 407b, and 407c. The pixel signals accumulated in the accumulation circuits 402a and 402b are output via the output circuit 503 as pixel signals for each pixel by driving the shift register circuit 501 by the CPU 100. The pixel signals accumulated in the accumulation circuits 403a and 403b are output via the output circuit 503 as pixel signals for each pixel by driving the shift register circuit 502 by the CPU 100. The output circuit 503 performs processing such as amplifying the pixel signal and outputs it to an AD converter (not shown) of the CPU 100.

  The operation of the focus detection apparatus configured as described above will be described in detail based on the flowchart of FIG.

  When a focus detection start signal is received by operating the switch group 214, the focus detection operation by the AF sensor 401 is started. First, in step S801, the lens communication circuit 205 communicates with the photographic lens 300 and is mounted. The maximum defocus amount that can occur at 300 and the current focus lens position are detected. In the next step S802, the maximum defocus amount that can occur during focus detection is calculated from the maximum defocus amount and focus lens position information of the photographing lens 300 detected in step S801. In the subsequent step S803, the first accumulation control region by the region selection circuits 404 and 405 is set based on the maximum defocus amount that can occur in the focus detection calculated in step S802.

  FIG. 18A is a diagram showing an accumulation control region when the maximum defocus amount is small and the accumulation range calculated from the maximum phase difference is 1/3 or less of the sensor array length. The L1, C1, and R1 areas, which are accumulation control areas of the line sensors 411a and 411b, are areas obtained by dividing the line sensor into three equal parts. Further, the L2, C2, and R2 areas, which are the accumulation control areas of the line sensors 421a and 421b, are also areas obtained by dividing the line sensor into three equal parts. In this case, it is possible to detect the focus in the two accumulation control areas for the subject at each distance measuring point.

  FIG. 18B is a diagram showing an accumulation control region when the maximum defocus amount is large and the accumulation control range calculated from the maximum phase difference is wider than 1/3 of the line. Among the accumulation control areas of the line sensors 411a and 411b, the C1 area is expanded from 1/3 of the sensor array length according to the accumulation control area calculated from the maximum phase difference, and the L1 area and the R1 area are the C area. Use parts other than those used for.

  On the other hand, among the accumulation control areas of the line sensors 421a and 421b, the L2 area and the R2 area are expanded to be 1/3 of the sensor array length according to the accumulation control area calculated from the maximum phase difference, and the C2 area is L2 Use parts other than those used for the region and R2 region. Even when the accumulation control area calculated from the maximum phase difference is wide, focus detection can be performed in at least one accumulation control area for the subject at each ranging point.

  The region selection circuit 404 is set to distribute the pixel signal of the L1 region to the PB contrast detection circuit 406a, the pixel signal of the C1 region to the PB contrast detection circuit 406b, and the pixel signal of the R1 region to the PB contrast detection circuit 406c. The region selection circuit 405 is set to distribute the pixel signal of the L2 region to the PB contrast detection circuit 407a, the pixel signal of the C2 region to the PB contrast detection circuit 407b, and the pixel signal of the R2 region to the PB contrast detection circuit 407c. To do.

  As described above, the accumulation control area is determined from the maximum defocus amount of the photographing lens 300 and the current focus lens position information.

  Returning to the flowchart of FIG. 17, in the next step S804, the CPU 100 controls the AF sensor 401 to start the accumulation operation by the accumulation circuits 402a and 402b and the accumulation circuits 403a and 403b. Also, the counting of the accumulation time by the timer 400 is started. In the next step S805, the CPU 100 performs a comparison determination between the accumulation time by the timer 400 and a predetermined time set in advance. If the accumulation time is equal to or shorter than the predetermined time, the process proceeds to step S806. On the other hand, if the accumulation time is longer than the predetermined time, the process proceeds to step S807.

  If it is determined that the accumulation time is equal to or shorter than the predetermined time and the process proceeds to step S806, an accumulation stop determination operation is performed for the accumulation control region set in step S803. The CPU 100 detects the accumulation stop signal output from the AF sensor 401. If the accumulation stop signal is detected, the CPU 100 proceeds to the signal reading operation in step S809. On the other hand, when the accumulation stop signal is not detected, the process returns to step S805, and thereafter the same operation is repeated.

  If the accumulation time is longer than the predetermined time and the process proceeds to step S807, the second accumulation control area is set (reset). Here, since it is determined in step S805 that the accumulation time is longer than the predetermined time, the subject is in a low luminance state. When the accumulation time is longer than the predetermined time, the focus detection accuracy decreases due to dark current that is a noise component of the pixel signal. Therefore, as shown in FIG. 18A, the subject is always restored to the accumulation control area where focus detection is possible in the two accumulation control areas (L1 area and L2 area, C1 area and C2 area, R1 area and R2 area). Set.

  In the next step S808, an accumulation stop determination operation is performed for the second accumulation control region reset in step S807. The CPU 100 detects the accumulation stop signal output from the AF sensor 401, and continues the operation of step S808 until the accumulation stop signal is detected. Thereafter, when an accumulation stop signal is detected, the process proceeds to a signal reading operation in step S809.

  In step S809, the pixel signal is read out from the area where the accumulation has been completed. By controlling the AF sensor 401 by the CPU 100, the pixel signals in the areas where the accumulation has been completed are sequentially output, and the pixel signals are AD-converted by an AD converter (not shown) in the CPU 100. Here, the AD-converted pixel signal is stored in the storage circuit 209. In the next step S810, it is determined whether the accumulation operation has been completed and the signal read operation has been completed in all of the L1, C1, R1, and L2, C2, and R2 regions. If the read operation has been completed in all areas, the process proceeds to step S811. On the other hand, if there is an area where the read operation has not yet been completed, the process returns to the operation of step S805, and the same operation is repeated thereafter.

  When the read operation is completed in all the areas and the process proceeds to step S811, correlation calculation is performed based on each pixel signal of each area stored in the storage circuit 209, and each area defocus amount is calculated. Focus detection results corresponding to the L ranging points in the L1 region and the L2 region, the C ranging points in the C1 region and the C2 region, and the R ranging points in the R1 region and the R2 region, respectively, are obtained. In addition, when the above steps S807 and S808 are passed, the focus detection result is obtained by performing an average process of the focus detection results by the two regions. In the next step S812, the focus of the photographic lens 300 is set via the lens communication circuit 205 based on the defocus amount (which always includes the defocus amount in the L2 region and the R2 region) calculated by the CPU 100 in step S811. The drive control of the lens is performed, and a series of focus detection operations are completed.

  According to the second embodiment described above, as in the first embodiment described above, the accumulation control of each line sensor is performed based not only on the maximum defocus amount that can occur in the photographic lens 300 but also on the focus lens position information at that time. Since the defocus amount is detected based on the pixel signal obtained in the determined area, the re-accumulation operation is performed when the accumulation control area is changed as in the prior art. It is not necessary to perform this, and the focus detection time can be shortened. In addition, by applying the accumulation area range determined as described above to the central distance measurement area and using the remaining pixel range as the peripheral distance measurement area, the detection areas overlap (overlap). Since focus detection can be performed without unnecessarily widening the accumulation control range, focus detection error (conflict of perspective) due to a signal from the background of the subject can be prevented.

  Further, the size (range) of the accumulation control area determined as described above is applied to the distance measuring area in the center of the line sensors 411a and 411b, and is applied to the distance measuring areas around the line sensors 421a and 421b. Thus, even when the accumulation control area is widened, the focus detection for a plurality of subjects can be appropriately performed without the areas overlapping each other.

  Further, when the subject is in a low luminance state or the like and the accumulation time becomes long and the focus detection accuracy is lowered due to the dark current that is a noise component of the pixel signal, the subject is always placed in two identical ranges as shown in FIG. The accumulation control region is switched so that focus detection can be performed in the regions (L1 region and L2 region, C1 region and C2 region, R1 region and R2 region). The detection accuracy can be improved by performing an average processing of the focus detection results by the two areas.

100 CPU
101 AF sensor 111a, 111b Line sensor 102a, 102b Storage circuit 103 Area selection circuit 104a, 104b, 104c PB contrast detection circuit 105 Storage stop determination circuit 106 Shift register 107 Output circuit 401 AF sensor 411a, 411b Line sensor 421a, 421b Line sensor 403a, 403b Storage circuit 404, 405 Region selection circuit 406a, 406b, 406c PB contrast detection circuit 408, 409 Storage stop determination circuit 501, 502 Shift register 503 Output circuit

Claims (3)

A focus detection device that communicates with a photographing lens including a focus lens and detects the maximum defocus amount that can occur in the photographing lens and the current position information of the focus lens,
A pair of first line sensors, a second line sensor, a pair of third line sensors, and a fourth line that receive and photoelectrically convert different pairs of light fluxes among the light fluxes passing through the photographing lens and output image signals. Line sensor,
A central area having a size based on the maximum defocus amount of the photographing lens and the current focus lens position information is set at the center of the first line sensor and the second line sensor, and the center Peripheral areas are set in the left and right remaining areas of the area, the peripheral areas of the third line sensor and the fourth line sensor are respectively set, and the central areas are set in the remaining areas of the peripheral areas, respectively. Setting means for setting;
Accumulation control means for performing image signal accumulation control in the central area set by the setting means, and for performing image signal accumulation control in the peripheral area set by the setting means;
The defocus amount of the central region based on the shift amount of the image signal respectively obtained in the central region set in the first line sensor and the second line sensor by the setting unit, and the setting unit by the setting unit The defocus amount of the central region based on the shift amount of the image signal respectively obtained in the central region set in the third line sensor and the fourth line sensor, the first line sensor, and the second line sensor. The defocus amount of the peripheral region based on the shift amount of the image signal respectively obtained in the peripheral region set in the line sensor, and the peripheral set in the third line sensor and the fourth line sensor Detecting means capable of detecting the defocus amount of the peripheral region based on the shift amount of the image signal respectively obtained in the region;
The setting means has a predetermined accumulation time of image signals in the first line sensor, the second line sensor, the third line sensor, and the fourth line sensor controlled by the accumulation control means. When longer than the accumulation time, the size of the central region of the first line sensor and the second line sensor is the same as the size of the central region of the third line sensor and the fourth line sensor. A focus detection apparatus that resets an area so as to become When the accumulation time of image signals in the first line sensor, the second line sensor, the third line sensor, and the fourth line sensor controlled by the accumulation control unit is longer than a predetermined accumulation time The detection means detects a defocus amount detected based on a shift amount of an image signal obtained in a central area of the first line sensor and the second line sensor reset by the setting means; An averaging process is performed on the defocus amount detected based on the shift amount of the image signal obtained in the center area of the third line sensor and the fourth line sensor reset by the setting means. The focus detection apparatus according to claim 1. An optical apparatus comprising the focus detection device according to claim 1.

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