JP2006322970A - Focus detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus detector capable of reducing a reference two-image interval value while achieving wide field. <P>SOLUTION: By excluding range-finding points near four corners of a photographic image plane corresponding to range-finding points which are not used for photography so much, a sensor train is arranged to come nearer to the center direction of the photographic image plane by as much as the space spared. The shape of the aperture part of a field mask is changed in accordance with the arrangement of the sensor train. Thus, the two-image interval value is shortened while maintaining the wide field. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a focus detection apparatus, and more particularly to a focus detection apparatus capable of detecting the focus state of a plurality of distance measuring points in a shooting screen.

  Various focus detection devices for cameras that can detect a focus state for a plurality of points in a shooting screen by arranging a plurality of distance measuring points on the shooting screen have been proposed. For example, Patent Document 1 is an example in which five-point distance measurement in the phase difference method is realized.

Further, in Patent Document 2, a horizontal sensor row pair corresponding to a horizontal focus detection region in a shooting screen and a vertical sensor row pair corresponding to a vertical focus detection region in a shooting screen are used, thereby The multi-point distance measurement and the accuracy of focus detection in the phase difference method are realized.
Japanese Patent Laid-Open No. 5-100159 JP-A-9-184965

  In recent years, the number of ranging points has been steadily increasing in order to realize further multi-point ranging and wide field of view. In order to realize high-precision focus detection, it is necessary to perform horizontal focus detection and vertical focus detection at all distance measurement points. Here, the technique of Patent Document 1 is a distance measuring point arrangement for obtaining golden division or third equal division, and horizontal focus detection and vertical focus detection are performed at the center distance measurement point. Only. In the method of Patent Document 2, the positions of the subject light fluxes at the exit pupils of the horizontal sensor row and the vertical sensor row are different, and the horizontal sensor row has higher focus detection accuracy than the vertical sensor row. However, the horizontal sensor row detects only the focus state near the center in the shooting screen.

  On the other hand, when the field of view is further increased, the optical path length of the secondary imaging system in the AF optical system provided in the focus detection apparatus increases. The reason for this will be described below.

  For example, the arrangement of AF sensor arrays for detecting the focus states of 23 distance measuring points as shown in FIG. 17 using a horizontal sensor array and a vertical sensor array is as shown in FIG. In the arrangement of sensor rows as shown in FIG. 18, when the shape of the opening of the field mask is rectangular as shown in FIG. 19, the range of the broken line frame in FIG. 18 (horizontal direction ls horizontal, vertical direction ls vertical range) ) Is irradiated with the subject luminous flux that has passed through the opening of the field mask. Here, in order to realize a wide field of view, it is necessary to widen the range in which the subject luminous flux that has passed through the opening of the field mask reaches the sensor surface (that is, the range of the broken line frame in FIG. 18). Here, when the range of the broken line frame in FIG. 18 is expanded, in order to prevent stray light from being generated between the horizontal sensor rows and between the vertical sensor rows, a reference two-image interval value (two image intervals at the time of focusing) ( It is necessary to lengthen the horizontal direction lz horizontal and the vertical direction lz vertical in FIG.

  FIG. 20 is a diagram schematically showing a secondary imaging system of the AF optical system. The reference two-image interval value lz is substantially determined by the emission angle θ of the subject light beam emitted from the condenser lens 117. The exit angle θ of the subject luminous flux emitted from the condenser lens 117 is determined by the position lp of the subject luminous flux at the exit pupil position when the subject luminous flux passes through the photographing lens, the primary imaging plane of the photographing lens and the AF optical system. And the distance (optical path length) Lt. Here, the pupil position lp of the subject light flux and the optical path length Lt are values determined at the time of designing the interchangeable lens, and cannot be changed after the interchangeable lens is manufactured. Therefore, the angle θ cannot be changed by changing the position lp and the optical path length Lt. Depending on the configuration of the AF optical system, for example, the angle θ can be minutely changed by the power of the condenser lens 117. However, since the subject light flux passes on the paraxial axis of the condenser lens 117 as shown in FIG. 20, the subject light flux hardly refracts. Therefore, it is impossible to largely change the angle θ. That is, the only way to increase the reference two-image interval value lz is to increase the optical path length L of the secondary imaging system.

  Thus, since the optical path length L of the secondary imaging system is substantially determined by the reference two-image interval value, it is necessary to reduce the reference two-image interval value in order to reduce the size of the focus detection device.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a focus detection apparatus capable of reducing the reference two-image interval value while realizing a wide field of view.

  In order to achieve the above object, a focus detection apparatus according to a first aspect of the present invention is a focus detection apparatus that detects a focus state of a subject at a plurality of distance measuring points in a shooting screen. A focus detection sensor including a pair of first sensor arrays corresponding to a focus detection area in a direction and a pair of second sensor arrays corresponding to a focus detection area in a substantially vertical direction of the shooting screen, The first sensor array and the second sensor array are configured such that the other pair of sensor arrays is arranged between the pair of sensor arrays.

  In order to achieve the above object, a focus detection apparatus according to a second aspect of the present invention is a focus detection apparatus that detects a focus state of a subject at a plurality of distance measuring points in a shooting screen. A focus detection sensor including a pair of first sensor rows corresponding to a substantially horizontal focus detection region and a pair of second sensor rows corresponding to a substantially vertical focus detection region of the photographing screen; The plurality of distance measuring points in the shooting screen are not arranged near the four corners of the shooting screen, and the focus states of the upper and lower distance measuring points at the plurality of distance measuring points in the shooting screen are determined. The first sensor row and the second sensor row to be detected are configured such that the other pair of sensor rows is optically disposed between the pair of sensor rows. It is characterized by.

  According to these first and second aspects, it is possible to reduce the reference two-image interval value while realizing a wide field of view.

  ADVANTAGE OF THE INVENTION According to this invention, the focus detection apparatus which can reduce a reference | standard 2 image interval value can be provided, implement | achieving a wide visual field.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration related to a focus state detection operation in a camera having a focus detection apparatus according to an embodiment of the present invention. Here, FIG. 1 illustrates a lens interchangeable single-lens reflex camera. That is, the camera shown in FIG. 1 includes an interchangeable lens 101 and a camera body 110.

  The interchangeable lens 101 is configured to be detachable from the camera body 110 via a camera mount (not shown) provided on the front surface of the camera body 110. Inside the interchangeable lens 101, a focus lens 102, a lens driving unit 103, and a lens CPU 104 are provided.

  A focus lens 102 as a photographing lens is a focus adjusting lens included in the photographing optical system, and is driven in an optical axis direction (arrow direction in FIG. 1) by a motor (not shown) in the lens driving unit 103. Here, the actual photographing optical system is composed of a plurality of lenses, but only the focus lens 102 is shown in FIG. The lens driving unit 103 includes a motor and its driving circuit (motor driver). The lens CPU 104 is a control circuit that performs control of the lens driving unit 103 and the like. The lens CPU 104 is configured to be able to communicate with the AF controller 122 in the camera body 110 via the communication connector 105. For example, lens data such as focus lens manufacturing variation information and focus lens aberration information stored in advance in the lens CPU 104 is communicated from the lens CPU 104 to the AF controller 122.

The camera body 110 is configured as follows.
The main mirror 111 is a mirror that is configured to be rotatable and that has a central portion formed of a half mirror. When the main mirror 111 is in the down position (shown position), a part of the light beam from a subject (not shown) that enters the camera body 110 via the focus lens 102 in the interchangeable lens 101 is reflected by the main mirror 111. Thus, the eyepiece lens 114 is reached through the focusing screen 112 and the pentaprism 113. Thereby, it is possible to observe the state of a subject (not shown).

  Further, a part of the light beam incident on the main mirror 111 is transmitted through the half mirror part and reflected by the sub mirror 115 installed on the back surface of the main mirror 111 to be used in an AF optical system for performing automatic focus detection (AF). Led. The AF optical system includes a field mask 116, a condenser lens 117, a total reflection mirror 118, a separator diaphragm 119, and a separator lens 120. An AF sensor 121 is disposed behind the AF optical system.

  FIG. 2 is a diagram schematically showing a secondary imaging system of the AF optical system used in the camera of FIG. The light beam reflected by the sub mirror 115 forms an image on the primary image forming surface. A field mask 116 is disposed on the primary imaging plane. In the field mask 116, the irradiation range of the incident light flux to the AF sensor 121 is regulated. The field mask 116 will be described in detail later.

  The light beam of the subject incident through the field mask 116 is collected by the condenser lens 117, reflected by the total reflection mirror 118, and then divided into pupils by a separator stop (not shown). The luminous flux of the subject divided into pupils by the separator diaphragm is collected by the separator lens 120 and enters a predetermined area of the AF sensor 121 as a focus detection sensor disposed behind the AF optical system. The AF sensor 121 will be described in detail later.

  In the AF sensor 121, the light flux from the subject is converted into an analog electric signal by photoelectric conversion. The output of the AF sensor 121 is input to the AF controller 122. The AF controller 122 calculates the defocus amount. The operation control of the AF controller 122 is performed by the system controller 123.

  Further, the defocus amount obtained by the AF controller 122 is communicated to the lens CPU 104. The lens CPU 104 calculates a drive amount of a motor for driving the focus lens 102 based on the communicated defocus amount. The focus lens 102 is driven to focus through the lens driving unit 103 based on the driving amount of the motor.

  In FIG. 1, when the main mirror 111 is at the up position where it is retracted from the optical path of the focus lens 102, the light flux from the subject incident through the focus lens 102 forms an image on the image sensor 124 and is photoelectrically converted. . The signal thus obtained is input to the system controller 123 and subjected to predetermined image processing.

  Next, the AF sensor will be described. FIG. 3 is a diagram showing a sensor array arrangement of AF sensors in the focus detection apparatus according to the embodiment of the present invention. The AF sensor shown in FIG. 3 includes a horizontal sensor row as a first sensor row including a horizontal reference portion sensor row A200a and a horizontal reference portion sensor row B200b arranged along the horizontal direction of the shooting screen, and shooting. It is composed of a vertical sensor row as a second sensor row comprising a vertical direction reference portion sensor row C200c and a vertical direction reference portion sensor row D200d arranged along the vertical direction of the screen. Here, each of the horizontal reference portion sensor row A200a and the horizontal reference portion sensor row B200b constituting the first sensor row is composed of 19 islands of n = 1 to 19. This island is a sensor area corresponding to each ranging point in the photographing screen. Each island has three lines of line sensors in which about several tens of pixels are arranged side by side in a direction perpendicular to the pixel arrangement direction. Further, as will be described later, the three rows of line sensors are arranged so as to be shifted from each other by ½ pixel in order to improve accuracy (FIG. 10). Further, each of the vertical direction reference portion sensor row C200c and the vertical direction reference portion sensor row D200d constituting the second sensor row is composed of 19 islands of n = 20 to 38. Here, the sensor array of FIG. 3 excludes islands at the four corners for detecting the four corners of the shooting screen with respect to FIG. The reference two-image interval values (lz horizontal and lz vertical) are shortened so as to be arranged according to the direction. Note that the lengths of ls horizontal and ls vertical are the same as in FIG. This is because the exit pupil diameter when the subject light flux incident on the horizontal sensor array pair passes through the focus lens 102 and the exit pupil diameter when the subject light flux incident on the vertical sensor pair pass through the focus lens 102 are equal. Is meant to be.

  FIGS. 4A and 4B are diagrams showing the arrangement of distance measuring points that can be detected by the sensor array arrangement of FIG.

  First, FIG. 4A shows an example in which 19 points excluding the vicinity of the four corners of the shooting screen are used as distance measuring points. Here, the distance measuring points in the vicinity of the four corners of the shooting screen are points that are not so necessary at the time of actual photography, and even if these distance measurement points are excluded, there is not much influence on actual photography. Conceivable. In the example of FIG. 4A, all 19 focus states can be detected using both the horizontal sensor row and the vertical sensor row.

  4B is the same as FIG. 4A in that the distance measuring points corresponding to the vicinity of the four corners of the photographing screen are excluded, but the distance measuring points at the upper and lower ends of the photographing screen are accordingly photographed. Multi-point distance measurement (in the example, 25 points) is performed by collecting near the center of the screen. However, since both the horizontal sensor array and the vertical sensor array have 19 islands, the focus state of some distance measuring points shown in FIG. 4B is the island of the horizontal sensor array or the vertical sensor array. Detect only on one of the islands in the row.

  Here, in FIG. 3, the four sensor rows are brought close to the center direction of the imaging screen, so stray light may be generated if the shape of the opening of the field mask 116 is a conventional rectangle. Therefore, in the present embodiment, the shape of the opening of the field mask 116 is determined so that the irradiation range of the subject light flux that has passed through the opening of the field mask 116 has the shape shown by the broken line frame in FIG. That is, in the present embodiment, the field mask 116 having the opening 116a shown in FIG. 5A that substantially matches the shape shown by the broken line frame in FIG. 3 is used.

  4A, in addition to the shape shown in FIG. 5A, the field of view having a substantially hexagonal opening 116b as shown in FIG. 5B. A mask 116 may be used, or a field mask 116 having a substantially elliptical opening 116c as shown in FIG. 5C may be used. This is because the subject image on the AF sensor surface is blurred due to the aberration of the secondary imaging system, etc., so that the shape of the opening of the field mask does not need to be the same as the shape of the island.

  The shape of the opening 119a of the separator aperture 119 may be a rectangle as shown in FIG. This is because the separator aperture 119 only has a function for preventing the subject light flux that does not need to enter the separator lens 120 and does not need to match the shape of the opening of the field mask 116. However, the position and size of the opening need to be appropriately determined depending on the position of the separator diaphragm 119.

FIG. 7 is a diagram comparing the relationship between the two-image interval value and the optical path length and the relationship between the conventional two-image interval value and the optical path length in the focus detection apparatus according to the embodiment of the present invention. Here, the relationship of FIG. 7 is common to both the horizontal direction sensor row and the vertical direction sensor row. By using the sensor array arrangement and the field mask as described above, the sensor array of the standard part and the sensor array of the reference part can be brought closer to the state indicated by the reference numeral 121a from the state indicated by the reference numeral 121a. As a result, the two-image interval value can be shortened from, for example, lz ₂ to lz _{1 in} FIG. 7 without changing the value of ls. In this case, the optical path length of the secondary imaging system can be shortened from L2 to L1 while maintaining a wide field of view. For example, in the sensor array arrangement shown in the example of FIG. 3, the optical path length can be shortened by about 9% compared to the example of FIG.

  FIG. 8 is a diagram showing a sensor circuit configuration of a part (each of five islands) of the horizontal direction reference portion sensor row A200a and the horizontal direction reference portion sensor row B200b of FIG. Here, n shown in FIG. 8 corresponds to n in FIG. In FIG. 3, sensor circuits other than those shown in FIG. 8 have the same circuit configuration as that of FIG. 8 except that island numbers are different.

  As shown in FIG. 8, in this embodiment, three line sensors 201 to 203 are arranged in parallel per island. In addition, as shown in FIG. 10, the three line sensors are arranged such that the line sensor 202 is shifted by 1/2 pixel from the other line sensors. Thus, the accuracy of focus detection can be improved by arranging the three line sensors in each island in a staggered manner. Further, as shown in FIG. 8, a monitoring photodiode unit 204 is disposed between the line sensor 202 and the line sensor 203.

  In FIG. 8, each island is provided with a photodiode portion 201-1 including a plurality of photodiodes. Each photodiode constitutes a pixel, and the photodiode unit 201-1 obtains a charge corresponding to the amount of light flux of the subject incident on each photodiode. The photoelectric charge obtained by the photodiode unit 201-1 is accumulated in the charge accumulation unit 201-2.

  Here, the charge accumulation amount of the charge accumulation unit 201-2 is monitored by the monitoring photodiode unit 204. The output of the monitoring photodiode unit 204 is output to the integration time control circuit 209. The integration time control circuit 209 determines whether or not the output of the monitoring photodiode unit 204 is equal to or higher than a predetermined threshold, and stores the charge when the output of the monitoring photodiode unit 204 exceeds the threshold. End (integration operation). Even if the output of the monitoring photodiode unit 204 is not equal to or greater than the threshold value, the charge accumulation is also terminated when a predetermined integration time is measured. Note that the threshold and the integration time for ending charge accumulation can be changed.

  When the charge accumulation ends, the transfer switch 201-3 connected to the subsequent stage of the charge accumulation unit 201-2 is closed, and the photocharge accumulated in the charge accumulation unit 201-2 is transferred to the charge transfer path 205.

  In the charge transfer path 205, each time a shift pulse is applied, the photocharge is transferred to the charge / voltage conversion amplifier 206 pixel by pixel and converted into a voltage signal. A voltage signal converted by the charge / voltage conversion amplifier 206 is selected at a predetermined amplification factor (for example, 1 ×, 2 ×, 4 ×, or 8 ×) in an amplifier circuit (shown as AMP in the figure) 207. And then input to the output selection circuit 208.

  In the output selection circuit 208, the voltage signal input in units of pixels is temperature-compensated based on the temperature detected by the temperature sensor 210, and the output voltage VN obtained thereby is output to the AF controller 122 at the subsequent stage. .

  Next, a method for calculating the defocus amount will be described. First, correlation calculation is performed prior to calculation of the defocus amount. This correlation calculation is performed by dividing the island into a plurality of correlation calculation frames. FIG. 9 shows a conceptual diagram of the division of the correlation calculation frame. Here, FIG. 9A shows a state of division in the islands in the horizontal sensor row, and FIG. 9B shows a state of division in the islands in the vertical direction sensor row. In the example of FIGS. 9A and 9B, one island is divided into a central correlation calculation frame 301, a right correlation calculation frame 302, and a left correlation calculation frame 303. The reason for performing the correlation calculation by dividing in this way is to enable the correlation calculation to be performed correctly even when a plurality of light beams of a subject mixed in perspective are incident on one island.

  Further, as described above, in this embodiment, each island is configured by arranging the three line sensors 201 to 203 in a staggered manner. In such a case, two adjacent lines (line sensor 201 and line sensor 202, line sensor 202 and line sensor 203) can be considered as one set.

  When light beams from the same part of the subject are incident on the same correlation calculation frame in one set of line sensors, the one set of line sensors can be regarded as one line sensor. In this case, the sensor data is alternately read out for each pixel to perform the correlation calculation. Hereinafter, such a calculation method is referred to as a staggered calculation.

  FIG. 10 is a diagram illustrating the concept of the reading order of sensor data when performing zigzag calculation. When performing the staggered calculation, first, the line sensor 201 and the line sensor 202 are regarded as one line sensor, and sensor data is read alternately for each pixel. In the case of FIG. 10, reading is performed in the order of pixel 1, pixel 2, pixel 4, pixel 5... Pixel 11, pixel 13, pixel 14. After reading the sensor data of the pair of the line sensor 201 and the line sensor 202, the line sensor 202 and the line sensor 203 are regarded as one line sensor, and the sensor data is alternately read for each pixel. In the case of FIG. 10, readout is performed in the order of pixel 2, pixel 3, pixel 5, pixel 6... Pixel 12, pixel 14, pixel 15.

  In addition, when the light beam from the same part of the subject is not incident on the same correlation calculation frame in one set of line sensors, the one set of line sensors cannot be regarded as one line sensor. The sensor data is read by using 201 to line sensors 203 as separate line sensors. In the case of FIG. 10, reading is performed in the order of pixel 1, pixel 4, pixel 7, pixel 10, pixel 13. Thereafter, the sensor data of the line sensor 202 and the line sensor 203 are read in the same manner.

  FIG. 11 is a flowchart showing a procedure of sensor data processing of the staggered line sensor. This process is performed inside the AF controller 122 and the system controller 123.

  In the process of FIG. 11, 1 is set to the parameter k indicating the line numbers of the three line sensors constituting the nth island of FIG. 3 (step S1). That is, k is a parameter that takes 1 to 3. In the example of this embodiment, k = 1 corresponds to the line sensor 201, k = 2 corresponds to the line sensor 202, and k = 3 corresponds to the line sensor 203.

After setting 1 to k, a parameter NG indicating whether the subject is similar or the subject distance is different is reset to 0 (step S2). Next, it is determined whether or not there is similarity in the sensor data of a pair of adjacent line sensors (k-th line sensor and k + 1-th line sensor, the first time being the line sensor 201 and the line sensor 202) (step S3). This similarity determination is performed by performing a correlation calculation between a pair of adjacent line sensors within each correlation calculation frame, and determining the reliability of the correlation value that provides the maximum correlation as a result of this correlation calculation. . Here, the correlation calculation is

In this equation, the minimum value of the correlation value F in the range of the shift amount −4 to +4 may be obtained. In Equation (1), D _k (i) is sensor data of the k-th line sensor, and D _{k + 1} (i) is sensor data of the k + 1-th line sensor.

  For example, the sensor data of the k-th line sensor is indicated by reference numeral 401-1 in FIG. 12A, and the sensor data of the k + 1-th line sensor is indicated by reference numeral 401-2 of FIG. If it is, the correlation value F calculated by (Equation 1) becomes the minimum when the shift amount is +1. At this time, the correlation amount shown in FIG.

  The reliability is high when the subject has high contrast, is not a repetitive pattern, and the minimum value of (Equation 1) is smaller than a predetermined threshold value. It is determined that the sensor data has similarity.

If it is determined in step S3 that the sensor data of a pair of adjacent line sensors is similar, step S3 is branched to step S4, and two images obtained by each of the adjacent pair of line sensors are obtained. It is determined whether or not the interval values are the same (step S4). For this purpose, the two-image interval value is individually calculated by the kth line sensor and k + 1. The two-image interval value can be obtained from the shift amount that provides the maximum correlation when the same correlation calculation as in the above (Equation 1) is performed between the standard part island and the reference part island. That is,

What is necessary is just to obtain | require the shift amount (shift amount which the correlation value F of (Formula 2) becomes the minimum) in which the maximum correlation is obtained. In the case of (Expression 2), the range of the shift amount is set within the range of the correlation calculation frame. In addition, DL (i) in (Expression 2) is sensor data for the island in the reference portion, and DR (i) is sensor data for the island in the reference portion.

  After obtaining the two-image interval value for each line sensor, it is determined whether or not the two-image interval value obtained by the k-th line sensor and the two-image interval value obtained by the k + 1-th line sensor are the same. To do. In this determination, first, the average value of the two image interval values obtained by the k-th line sensor and the two image interval values obtained by the (k + 1) -th line sensor is calculated, and each of the average value and each line sensor obtained is calculated. This is performed by determining whether or not the difference between the two image interval values is smaller than a predetermined threshold value.

  If it is determined in step S4 that the two image interval values are the same, step S4 is branched to step S5, and the sensor data of the kth line sensor and the sensor data of the k + 1th line sensor are combined. A correlation operation is performed between the reference portion and the reference portion, and a composite two-image interval value is calculated (step S5). The sensor data is synthesized by shifting and synthesizing one sensor data by the shift amount obtained at the time of similarity determination in step S1, as shown in FIG. By performing synthesis in this way, the apparent pixel pitch can be halved before synthesis. Note that it is preferable to determine the reliability after the correlation calculation in the same manner as the method of step S3.

  Further, when there is no similarity in the sensor data of the adjacent pair of line sensors in the determination in step S3, or when the two image interval values respectively obtained by the adjacent pair of line sensors in the determination in step S4 are not the same. After branching to step S6 and adding 1 to NG (step S6), the two image interval values are respectively determined for the k-th line sensor and the k + 1-th line sensor in the same manner as in the determination of step S4. Calculate (step S7). Also in this case, it is preferable to determine the reliability after the correlation calculation in the same manner as the method of step S3. However, the predetermined threshold in the reliability determination in step S7 is smaller than the predetermined threshold in the reliability determination in step S5.

  After the above processing, 1 is added to k (step S8), and it is determined whether or not k has become 3, that is, whether processing has been completed for all lines (step S9). If it is determined in step S9 that k is not 3, the process returns to step S3, and the process from step S3 to step S7 is performed on the next set of adjacent line sensors (that is, the line sensor 202 and the line sensor 203). On the other hand, if it is determined in step S9 that k is 3, step S9 is branched to step S10, and it is determined whether NG is 0 (step S10).

If NG is 0 in the determination in step S10, it means that the staggered calculation is being performed on both the line sensor 201 and the line sensor 202, and both the line sensor 202 and the line sensor 203. In this case, the final two-image interval value is obtained by performing weighted addition averaging of the two combined two-image interval values obtained by the two operations with reliability (step S11). That means

Perform the operation. Note that the calculation in step S11 is not a weighted average, but may simply average two composite two-image interval values. The system controller 123 determines whether to perform a weighted average or a simple average.

  By combining the sensor data of the paired line sensors in this way to obtain the two-image interval value, and further averaging the two combined two-image interval values, the two-image interval value was obtained with only one line. Compared to the case, the accuracy can be improved by a factor of two.

  If NG is not 0 in the determination in step S10, the staggered calculation is not performed on at least one of the line sensor 201 and the line sensor 202, and the line sensor 202 and the line sensor 203. In this case, the two-image interval value obtained by the line sensor in which the luminous flux of the closest object among the line sensors 201 to 203 is incident is set as the final two-image interval value (step S12).

  The two-image interval value can be obtained by the processing as described above. After the two-image interval value is obtained, the defocus amount is calculated.

  First, a correlation calculation frame is selected. Here, a correlation calculation frame in which the obtained two-image interval value is highly reliable and a plurality of line sensors receive the same subject is preferentially selected. By selecting such a correlation calculation frame, the focus state can be detected with higher accuracy.

  After selecting the correlation calculation frame, the distance measuring point is selected. This distance measuring point selection is performed according to the distance measuring point selection mode. For example, when the distance measuring point selection mode is the single point mode, the two-image interval value specified by the photographer is used. In addition, when the AF point selection mode is multi-mode, the AF points that output sensor data with high reliability are selected from all AF points, and the closest AF points are selected. This distance measuring point is selected, and the two-image interval value at this distance measuring point is used to calculate the defocus amount. Here, when there are a plurality of distance measuring points having two image interval values that are substantially the same as the two image interval values of the distance measuring point selected as the closest object, the images of these distance measuring points are the same as those of the same subject. Assuming that the image is an image, the average value of the two image interval values of a plurality of distance measuring points having the same two image interval values is used to calculate the defocus amount.

  As a result of such a distance measurement point selection, the defocus amount is calculated from the obtained two-image interval value by the optically calculated defocus coefficient. The final defocus amount is corrected by correcting the defocus amount error due to variations in temperature, body variations during manufacturing, focus lens variations during manufacturing, etc. Is calculated.

  After the defocus amount is calculated, the calculated defocus amount is transmitted to the lens CPU 104. The focus driving of the focus lens 102 is performed by controlling the lens driving unit 103 by the lens CPU 104 based on the transmitted defocus amount.

Next, an electric circuit configuration of a camera equipped with the focus detection apparatus according to the present embodiment will be described with reference to FIG.
FIG. 14 is a block configuration diagram showing an overall electrical circuit configuration of a camera having the focus detection apparatus according to the present embodiment. FIG. 14 shows the interchangeable lens and the camera body without distinction.

  In FIG. 14, a zoom lens system 501 including the focus lens is disposed at a predetermined position of the camera. The zoom lens system 501 represents a photographic optical system including the focus lens as a representative lens. The zoom lens system 501 is driven by a lens driving unit 502. The lens driving unit 502 is controlled by the lens CPU 503.

  An imaging element 504 such as a CCD is disposed on the optical path of incident light of the zoom lens system 501. The imaging element 504 is connected to the bus line 507 via the imaging circuit 505 and the A / D converter 506. A system controller 508 and an AF controller 509 are connected to the bus line 507. An AF sensor 510 is connected to the AF controller 509. Further, the bus line 507 has a disk 511 or a card-like recording via a ROM 511 storing various control programs and various data processing information, a RAM 512 for temporarily storing data, a drive controller 513 and a media drive 514. The medium 515 is connected, the external input / output terminal 517 is connected via the external I / F unit 516, the video output terminal 519 is connected via the video encoder 518, and the LCD display is displayed via the video encoder 518 and the LCD driver 520. The part 521 is connected.

  A system controller 508 controls the entire camera, and is configured to be communicable with the lens CPU 503. Furthermore, the system controller 508 supplies power to the dial unit 523 and the switch unit 524 for detecting the operation state of the operation unit that inputs each instruction to the camera such as mode setting via the operation unit driver 522. A power supply unit 525 to be supplied is also connected.

  The power supply unit 525 is provided with an external power input terminal 526 for receiving external power supply. Further, a strobe light emission unit 527 for performing flash emission is connected to the system controller 508.

  In such a configuration, when the sensor output from the AF sensor 510 is input to the AF controller 509, the AF controller 509 performs various calculations as described above to calculate the defocus amount, and the calculated defocus amount. Based on this, the lens driving unit 502 is controlled via the lens CPU 503, and the focus lens in the zoom lens system 501 is driven.

  In addition, when an image of a subject (not shown) is formed on the image sensor 504 via the zoom lens system 501, the subject image is output from the image sensor 504 as an imaging signal obtained by photoelectric conversion. This image pickup signal is processed in the image pickup circuit 505 in the subsequent stage, and further converted into digital image data in the A / D converter 506. This digital image data is input to the system controller 508 via the bus line 507. The system controller 508 performs various signal processing such as JPEG compression / decompression processing of input image data. Here, the RAM 512 is used for temporary storage of various data during signal processing by the system controller 508 and AF calculation by the AF controller 509.

  In addition, when a disk-like or card-like recording medium 515 for recording image data or the like is loaded into the media drive 514, the image data is recorded on the recording medium 515 or the image data is read. At this time, the operation of the media drive 514 is controlled by the drive controller 513. When image data is read from the recording medium 515, the read image data is sent to the system controller 508 via the bus line 507, and the same signal processing as described above is performed.

  Peripheral devices such as a personal computer are connected to the bus line 507 via an external input / output terminal (for example, a USB terminal) 517 and an external I / F unit 516. Image data and the like held by the peripheral device are captured via the external input / output terminal 517 and the external I / F unit 516, and the media drive 514 is driven and recorded on the recording medium 515 under the control of the drive controller 513. It is like that.

  Further, the video encoder 518 encodes the image signal A / D converted by the A / D converter 506 or the image signal read from the recording medium 515 and subjected to JPEG decompression processing by the system controller 508, and is displayed on the LCD display unit 521. A predetermined display is made. At this time, the LCD display unit 521 is driven by the LCD driver 520. Furthermore, this camera can also output a video signal externally via a video output terminal 519.

  As described above, according to the present embodiment, the distance measuring points near the four corners of the shooting screen corresponding to the distance measuring points that are rarely used for shooting are excluded, and the sensor array is arranged in the center direction of the shooting screen by the empty space. Therefore, the two-image interval value can be shortened while maintaining a wide field of view. Thereby, the optical path length of a secondary optical system can be shortened, and a focus detection apparatus can be reduced in size.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention. For example, in the above-described embodiment, the number of line sensors of the staggered line sensor is three, but this number may be increased.

  Further, the way of arranging the distance measuring points is not limited to that shown in FIG. For example, when the distance measuring points are nine as shown in FIG. 15, n = 1, n = 3, n = 4, n = 7, n = 8, n = 12, n = 13, n in FIG. = 16, n = 17, n = 19, n = 20, n = 21, n = 22, n = 23, n = 25, n = 33, n = 35, n = 36, n = 37, n = 38 islands may be excluded, and the shape of the opening of the field mask may be a substantially rhombus shape as shown in FIG. In this way, although the field of view is narrowed, the optical path length can be further shortened.

  Further, the above-described embodiments include various stages of the invention, 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.

It is the figure shown about the structure regarding a focus state detection operation | movement in the camera which has the focus detection apparatus which concerns on one Embodiment of this invention. It is the figure which showed typically the secondary image formation system of AF optical system used with the camera of FIG. It is a figure which shows the example of sensor row | line | column arrangement | positioning of AF sensor as a focus detection apparatus which concerns on one Embodiment of this invention. It is the figure shown about the ranging point which the AF sensor of FIG. 3 detects. It is a figure shown about the shape of the opening part of a visual field mask. It is a figure shown about the shape of the opening part of a separator aperture_diaphragm | restriction. It is a comparison figure of the relationship between 2 image interval value and optical path length of one Embodiment of this invention, and the relationship between 2 image interval value and optical path length of a prior art example. It is a figure shown about a part of sensor circuit structure of the horizontal direction reference | standard part sensor row | line and horizontal direction reference | standard part sensor row | line | column of FIG. It is a conceptual diagram of the division | segmentation of a correlation calculation frame. It is the figure shown about the view of the reading order of sensor data. It is a flowchart shown about the procedure of the sensor data process of a staggered line sensor. It is a figure for demonstrating a correlation calculation. It is a figure for demonstrating composition of sensor data. It is a block block diagram which shows the whole electric circuit structure of the camera which has the focus detection apparatus which concerns on one Embodiment of this invention. It is a figure shown about ranging point arrangement | positioning in the modification of one Embodiment of this invention. It is a figure shown about the shape of the opening part of the visual field mask in the modification of one Embodiment of this invention. It is a figure shown about the ranging point arrangement | positioning in a prior art example. It is a figure shown about the sensor array arrangement | positioning in a prior art example. It is a figure shown about the shape of the opening part of the visual field mask in a prior art example. It is a figure shown about the relationship between the 2 image interval value and optical path length of a prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Interchangeable lens, 102 ... Focus lens, 103 ... Lens drive part, 104 ... Lens CPU, 105 ... Communication connector, 110 ... Camera body, 111 ... Main mirror, 112 ... Focusing screen, 113 ... Pentaprism, 114 ... Eyepiece , 115 ... sub-mirror, 116 ... field mask, 116 a to 116 c ... aperture, 117 ... condenser lens, 118 ... total reflection mirror, 119 ... separator diaphragm, 120 ... separator lens, 121 ... AF sensor, 122 ... AF controller, 123 ... System controller 124 ... Imaging device

Claims (5)

In a focus detection device that detects a focus state of a subject at a plurality of distance measuring points in a shooting screen,
For focus detection including a pair of first sensor rows corresponding to a focus detection region in a substantially horizontal direction of the shooting screen and a pair of second sensor rows corresponding to a focus detection region in a substantially vertical direction of the shooting screen. Equipped with a sensor,
The focus detection apparatus, wherein the first sensor array and the second sensor array are configured such that the other pair of sensor arrays is disposed between the pair of sensor arrays. A field mask having an opening provided on a primary imaging plane of the photographing optical system and having an opening for restricting an irradiation range of the subject light flux that has passed through the photographing optical system to the focus detection sensor;
The focus detection apparatus according to claim 1, wherein the shape of the opening of the field mask includes any one of a substantially elliptical shape, a substantially hexagonal shape, and a substantially rhombus shape.   The exit pupil diameter when the subject luminous flux incident on the first sensor array passes through the imaging optical system is the exit pupil diameter when the subject luminous flux incident on the second sensor array passes through the imaging optical system. The focus detection apparatus according to claim 2, wherein   The focus detection apparatus according to any one of claims 1 to 3, wherein a plurality of distance measuring points in the shooting screen are not arranged near four corners of the shooting screen. In a focus detection device that detects a focus state of a subject at a plurality of distance measuring points in a shooting screen,
For focus detection including a pair of first sensor rows corresponding to a focus detection region in a substantially horizontal direction of the shooting screen and a pair of second sensor rows corresponding to a focus detection region in a substantially vertical direction of the shooting screen. Equipped with a sensor,
The plurality of distance measuring points in the shooting screen are not arranged near the four corners of the shooting screen,
The first sensor array and the second sensor array for detecting the focus states of the upper and lower distance measuring points at the plurality of distance measuring points in the photographing screen are optically one pair of sensor arrays. A focus detection apparatus characterized in that the other pair of sensor rows are arranged between each other.

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