JPS62163008A - Focus detector - Google Patents

Abstract

PURPOSE:To make correct focus detection by an electrical correction operation by dividing the 1st photoelectric transducer array which generates the output corresponding to the illuminance distribution of the 1st light image out of the 1st and 2nd light images of an object of which the inter-image spacing changes according to the focusing condition of an objective lens to plural blocks and correcting the data on the focusing condition by as much as the distortion components of a focus detecting optical system. CONSTITUTION:Not the central part over the entire part of a reference part L of a line sensor 15 but the regions deviated to the right and left are used and therefore, the correction of the distortion is executed in the case of using the 1st and 3rd blocks I, III of the reference part L. More specifically, whether the detection with the 1st block I is possible or not is judged and if the detection is possible, the inter-image spacing deviation P1 by the 1st block I is calculated after the interpolation calculation. The error by the distortion of the focus detecting optical system is corrected in the stage of calculating the inter-image spacing deviation P1. A correlation calculation is similarly executed after checking of the contrast, by which the inter-image spacing deviation P3 by the 3rd block III is calculated and the error is corrected in this case as well. Driving of the lens is thereafter executed.

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a focus detection device that detects the focus state of the objective lens by receiving limb photographing light that has passed through the objective lens of a camera. 2. Description of the Related Art In this type of focus detection device, a first
・In order to form a second optical image, the first and second imaging lenses are placed near the intended imaging plane of the objective lens so that the effective diameters of the first and second imaging lenses are projected into the exit pupil of the objective lens. It is common to place a condenser lens in front of the second imaging lens. Figures 10 and 11 show condenser lens (6)
This figure shows the optical system of a conventional focus detection device of this type using a focus detection device and the state of image formation by it. It has a condenser lens (6) made of a spherical lens at the rear position, and an imaging lens (
8), (10), and each imaging lens (8), (10
) are arranged with line sensors (12) and (14) each having, for example, a C0D (charge coupled device) as a light receiving element. The first and second images of the object are formed on each line sensor (12) and (14), respectively, and as shown in Figure 1+, these images are different from the image of the object to be focused on. In the case of so-called front bins, which form an image in front of the intended focal plane, they are close to the optical axis (18) and close to each other, while in the case of rear bins, on the other hand, they are far from the optical axis (18). When the image is in focus, the distance between the two corresponding points of the I and second images becomes a specific distance defined by the configuration of the optical system. Therefore, the focus state can be determined by detecting the first and second image intervals. Detection of this image interval is performed in principle as follows. That is, in FIG. 12, each of the sensors (12) and (14) consists of, for example, 10 and 16 photodiode cells aI-alo+b+ to b+s. For convenience, it is assumed that the symbols assigned to the cells also represent the output of each cell. Now, considering a set of 10 consecutive cells in the sensor (14), seven sets Bl+Bl . . . B7 are formed as shown in FIG. 12. Which pair of elephants among these 7 pairs is cell 8 of sensor (12)?
The focus state is determined by determining whether the image most closely matches the image detected in the group A of 1 to alQ. For example, assume that the image of the sensor (12) matches the image of the part of the sensor (14) of group B. In other words, cell allat
%”, each output of a+o and cells b, , b, , −
, b , , and each output, a+=b+, at=tl
It is assumed that the relationship t+"'+a+o=tl+o holds true. In this case, Sl"'lal bll+1at-btl+...la
+o b, ol=0...
...(1), but Sl is smaller than similar calculation results for images of groups other than group B1, and is the smallest among the calculation results for all images of groups. In order to find a set that takes such a minimum value, set B1 and set B t that are sequentially shifted one cell at a time relative to this set B1,
The above calculation is performed for each image of B 3 , . . . , B 7 . Next, an operation is performed to find the minimum value among the obtained calculation results. The above series of calculations are performed by the correlator (16) shown in FIG. 16, and the focus state is detected. Problems to be Solved by the Invention By the way, what should be noted here is that the optical axes of the first and second imaging lenses (8) and (+o) are the optical axis of the condenser lens (6), that is, the focal point. Wavefront aberrations, especially distortion aberrations, which occur due to deviation from the optical axis (18) of the objective lens (2), which is the main optical axis of the detection optical system, cause the optical axis ( 18), and this makes it difficult to accurately detect the image interval between the first and second images. This is shown in Figure 13(a),
To explain in detail with reference to (b) and (c), the first
Figure 3 (a) shows the main optical axis (I8) on the planned imaging plane (4).
) shows the illuminance distribution of the first and second images on the line sensors (12) and (14) when a single dark slit image is formed at the position. In contrast, Fig. 13 (
In b) and (c), one dark slit image is located on the planned imaging plane (4) at a distance ΔQ from the optical axis (I8).
The figure shows the illuminance distribution of the first and second images on the line sensors (+2) and (14) when they are formed shifted upward and downward by the same amount. In these cases, the image interval between the first and second images should be ρ1-ρ2-Q3, but due to the difference between the optical axes of the first and second imaging lenses (8) and (10) and the condenser Q+>(
h=(b, and as Δg increases, Q2.Q becomes smaller as shown by the solid line in FIG. 14. In other words, when a dark slit image is also formed on the planned imaging plane (4) Even if there is, the further away from the main optical axis (I8) the image is formed, the narrower the distance between the first and second images becomes.This means that when performing focus detection of an actual object image, , which means that even if the focus adjustment state of the objective lens (2) is the same, the image interval may differ for each corresponding portion of the first and second images. Therefore, the first and second images, which are the basis of image interval calculation,
There will be a difference in focus detection results depending on the position of the main part of the second image. JP-A-60-32012 proposes an invention that attempts to optically suppress the above-mentioned effects of wavefront aberration, especially distortion, by making the condenser lens aspherical, as shown by the broken line in Figure 14. However, not only is it costly to manufacture an aspherical lens due to the manufacturing of molds, etc., but also a complex aspherical lens design is required to increase the suppression effect, making it impossible to provide an inexpensive focus detection device. There were drawbacks. SUMMARY OF THE INVENTION An object of the present invention is to provide a focus detection device that solves the above problems in an inexpensive manner by using electrical calculations. Means for Solving the Problems Therefore, the present invention provides first and second lenses arranged symmetrically with respect to the optical axis of the objective lens behind the condenser lens.
The imaging lens forms first and second optical images of an object whose image distance changes depending on the focus adjustment state of the objective lens, and outputs corresponding to the illuminance distribution of these first and second optical images are formed. providing first and second photoelectric conversion element arrays that generate

The photoelectric conversion element array is divided into a plurality of blocks, and the data calculation means calculates data corresponding to the focus adjustment state of the objective lens based on the correlation with the pixels of the second photoelectric conversion element array corresponding to each block. Based on this data, the selection means selects which block from among the multiple blocks should be used as focus adjustment state data, and only the distortion component by the focus detection optical system corresponding to the selected block is corrected. The present invention is characterized in that the focus adjustment state data is corrected by the means. That is, according to the present invention, the second optical system generates an output corresponding to the illuminance distribution of the second optical image of the object. The photoelectric conversion element array is divided into a plurality of blocks, and the focus adjustment state data is corrected by the distortion component caused by the focus detection optical system depending on the block adopted for focus detection. When the main parts of the first and second optical images are located away from the center of each optical image, the main parts are greatly affected by the wavefront aberration generated by the condenser lens. Therefore, a difference occurs in the focus detection results depending on the positions of the main parts of the first and second elephants, which are the basis of the image interval calculation. Therefore, in the present invention, it is possible to detect which block of the first photoelectric conversion element divided into a plurality of blocks the main part belongs to, select that block, and create a distortion corresponding to the selected block. The focus adjustment state data is corrected by the correction means for only the component. Therefore, TI-focus detection can be performed without being affected by wavefront aberrations generated by the condenser lens. Embodiments of the present invention will now be described in detail with reference to the drawings. A circuit diagram of a focus detection device and an automatic focus adjustment device using the same according to the present invention is shown in FIG. In the following description, it is assumed that the conventional optical system shown in FIG. 10 is used as a focus detection optical system. However, the line sensors (12) and (Ia) are each constructed from two different regions of one line sensor (15) formed on the same semiconductor chip as shown in FIG. In this Figure 2, (X) is the objective lens (2
) indicates the position through which the optical axis (18) passes. (Q,)～((,
, ) is the reference part (L) corresponding to the line sensor (12)
(Ql) ~ (ρ20), (Otsu, ~ (3
, ) and (f!2.-1.,) are respectively placed in the base yarn part (L). Second. Third block (1), (II)
, (III). Here's the first one. Third block (
1) and (III) each have 20 pl pixels, and
The second block (II) also has 21 pixels. on the other hand,
(rl) to (r48) indicate pixels in the reference section (R) corresponding to the line sensor (14). The number of pixels in the reference portion (R) is 48, which is eight more than the number of pixels in the reference portion (L). A monitor light-receiving element (not shown), which will be described later, is disposed above and close to the reference part (L). In addition,
In Figure 2, the pixel (mu) of the reference part (L) located farthest from the optical axis passing position (X) and the pixel (mu) of the reference part (R) located closest to the optical axis passing position (X). Let Ll be the distance to the pixel (rl). Further, when the objective lens (2) is in focus on the object, that is, when the object image by the objective lens (2) is formed on the planned imaging plane (4), the reference portion (L) The image with the same illuminance distribution as the image on the second block (II) of
,), the optical system is designed to be formed. These pixels (r5) to (r=,) are the focused block (F) in the reference part (r()), and the second block (F) in the reference part (L) is
The distance between the pixel (ff2.) at the center of If) and the pixel (r-,) at the center of the focusing block (F) of the reference section (R), that is, the image interval at the time of focusing, is . Figure 1 shows a CCD as a line sensor (15) in Figure 2.
(charge coupled device
) shows a circuit diagram of a focus detection device and an automatic focus adjustment device using the same. (20) is a photoelectric conversion circuit including the above-mentioned line sensor (15) and a monitor light receiving element, and a shift pulse (SH)
, transfer lock (φυ, (φ2), clear pulse (■C
G) is manually input and outputs a time-series pixel signal (OS), monitor output (AGCOS), and reference voltage output (D.S). Here, the clear pulse (T CG) is a pulse for setting each pixel in the line sensor (15) to the initial state.
) discharges the accumulated charge and starts anew light integration, that is, charge accumulation. Also, due to this pulse, the integral of the output of the monitor light receiving element is changed to the photoelectric conversion circuit (
20), and the monitor output (AGCOS) changes relative to the reference voltage output (DOS) over time at a speed that depends on the brightness of the object. The shift pulse (SH) is a pulse that shifts accumulated charges from the pixel section of the line sensor (15) to a part of the shift register, and when this pulse is input, light integration in the pixel section ends. Transfer lock (
φl) and (φ2) are pulses that are 180° out of phase with each other in order to sequentially output the accumulated charge shifted to a part of the shift register from that part of the shift register in a time-series manner. is a photoelectric conversion circuit (2
0) are converted into negative voltage signals respectively, and the pixel signals (OS
) is output as (22) is the reference voltage output (DO) from each pixel signal (OS).
S) is subtracted, and the pixel signal (DO8
'), (24) is the subtraction circuit (22)
Among the pixel signals (DO9') output from the , the pixel signals corresponding to the several pixels that are shaded (for example, the several pixels to the left of (1) in Fig. 2) are peak-held, and those pixel signals are The peak bold circuit that outputs the voltage (vp) corresponding to the maximum value, (26) is the subtraction circuit (22)
From the pixel signal (DOS') from the peak hold circuit (
This is a variable gain amplifier that subtracts and amplifies the output voltage (vp) of 24), and the dark current component included in each pixel signal (DOS') is removed by the subtraction in this amplifier circuit (26). (28) is an A/D conversion circuit that converts the amplified pixel output (DOS) from this amplifier circuit (26) into a digital value of predetermined bits, and its output is sent to a microcomputer (3o) (hereinafter referred to as microcomputer). (32) is a gain control circuit, and the monitor output (A
GCOS) is detected with respect to the reference output (DOS), and when the amount of change reaches a predetermined threshold within a predetermined time from the start of the change in monitor output (when it is bright), a message indicating this is sent to the microcontroller (30). Outputs a signal (TINT) indicating
And outputs a gain signal that sets the gain of the amplifier (26) to "1x". Furthermore, after a predetermined period of time has elapsed since the start of the output of the monitor output (AGCOS), the forced shift signal (Sl-IM) output from the microcomputer (30) is output to the gain control circuit (32). Circuit (3
2) is the signal (Sr-1M) monitor output (
The IIJ gain of the amplifier (26) is "1x" according to the amount of change with respect to the reference voltage output (DOS) of the AGCOS). A gain signal set to "2x", "4x" or "8x" is output. In this case, the smaller the amount of change, the larger the set f11 gain becomes. (AN) and (011) are an AND circuit and an OR circuit, respectively, and the AND circuit (AN) receives the above-mentioned signal (TtNT) from the gain control circuit (32).
and the signal (SHEN) from the microcomputer (30), the output signal of the OR circuit (On)/the AND circuit (AN), and the above-mentioned signal (SHM) from the microcomputer (30). Here, a signal (Sl-
IEN) is a signal for permitting shift pulse generation by the shift pulse generation circuit (34).
H) should be prohibited from occurring (for example, in photoelectric conversion circuits (
20) to the microcomputer (30) and data calculation in the microcomputer (30)) becomes "LOW", but then becomes "High" and the AND circuit (AN)
open. Therefore, this signal (SHEN) is “High”.
When the signal (TINT) is generated at the time of ``h'', the AND circuit (AN) outputs the ``I-I igh'' signal (TINT). (M) to the shift pulse generation circuit (34), and in response, the shift pulse generation circuit (34)
generates a shift pulse (S H). (36) is a transfer lock generation circuit that receives a clock pulse (CL) from the microcomputer (30) and generates transfer locks (φ, ), (φ2).
) or (SHM), it is reset to the initial state,
Regardless of the phase of the previous transfer lock (φυ, (φ,), start generating new (φ,), (φ2) (this is a combination of shift pulse (SH) and transfer lock (φ, ),
This is to synchronize (φ2). ). The signal (S/T()) output from the microcomputer (30) is the pixel signal (DO5') taken in by the peak hold circuit (24).
) is a sample bold signal for specifying. The microcomputer (30) is connected to the display circuit (38) and the lens drive amount ff1 (40), and causes the display circuit (38) to display the focus adjustment state of the objective lens (2) obtained by calculation as described later. On the other hand, the lens driving device (40) is then caused to drive the objective lens. In this embodiment, the focus adjustment state of the objective lens (2) calculated by the microcomputer (30) is expressed by a defocus point and a defocus direction, and therefore the objective lens (2) is 2) The amount of drive and the direction of drive are determined. The lens driving device (40) drives the objective lens (2) according to the driving amount and driving direction, while outputting a signal indicating the executed lens driving amount to the microcomputer (3o), and the microcomputer (30) When the lens drive amount reached the drive amount determined by calculation, a signal to stop lens drive is output to the lens drive device. In addition, in Fig. 1, (A F S W) is the microcomputer (
3o) is an AF switch for inputting a start signal for starting detection of the amount of deviation and automatic focus adjustment based thereon. FIG. 3 is a flowchart showing the basic operation flow of the above-mentioned microcomputer (30). When a power switch (not shown) is turned on, power is supplied to the camera. The steps in Figure 3 start,
In the #1 ΔF switch determination step, the AP switch (A
When the AP switch (AF SW) is turned on, the microcomputer (30) causes the COD to accumulate charge in step #2, and when this is completed, # In the DataDump step of 3, the COD output is sequentially output as a video signal (O9). This video signal (O5> is subtracted by a subtraction circuit (22) to become a pixel signal, but this pixel signal is amplified by 1] with a gain according to the subject, and then further converted into an A/D conversion circuit (28). /D conversion and becomes a digital value.Next, in step #4, difference data is re-created from the pixel signal obtained in order to remove the low-frequency signal component of the pixel signal.Next, the obtained pixel signal is Using the difference data of the pixel signals obtained, the correlation between the standard part (L) and the reference part (R) is calculated in step #5, and the reference part (It) with the highest degree of correlation is calculated in step #6.
Calculate the area of Furthermore, in step #7, interpolation calculation is performed to obtain a more accurate image interval deviation insect, and #8
The image interval deviation P is calculated based on this step. Step #9 checks whether the image interval deviation amount P obtained in step #8 is highly reliable! This is the step of cutting l'JI. If it is determined that detection is not possible in step #9, #1
At step 0, it is determined whether LO-CON SCAN has ended or not. L□-CON 5CA
N is a measure to be taken when the amount of defocus is too large and distance measurement becomes impossible.N is the measurement that is obtained when the amount of defocus is within the measurable range when distance measurement is performed without moving the camera lens. This is 5CAN for controlling the lens to the in-focus position based on the distance value, that is, the amount of image interval deviation. #LO-CON 5CA already in step 1O
If N has been completed, L (not shown) in step #12.
Display O-C0N and return to #2 COD integration step again. If LO-CON 5CAN is not completed, step #ll and 0-CONSCAN
and returns to #2 COD integration step again. #9
If it is determined that detection is possible in step #13, the image interval shift amount is converted into a defocus amount (focus shift amount), and further, in step #14, it is converted into a lens drive amount for rotating the lens. Next, it is determined whether the defocus amount or lens drive amount found in step #15 is within the focusing range. If it is determined that the camera is in focus, a focus display (not shown) is performed in step #I7. If it is determined that the lens is not in focus, the lens is driven in step #16 according to the drive amount obtained in step #I11, and the process returns to step #2 for ccpx. The series of operations explained above is described in Japanese Unexamined Patent Publication No. 5
As it is explained in detail in Publication No. 9-126517,
Below, only the parts related to the present invention will be explained in more detail. FIG. 4 is a flowchart showing one embodiment of the present invention.
Divide the base part into three blocks, calculate the image interval deviation amount for each block, and use the value that determines that the rear focus is the closest, that is, the subject is closest to the objective lens (2), as the true value. It is used as a lens to drive the lens. As explained in Figure 2, the pixel area of the reference part (L) is divided into three blocks (D, (II), and (III)), and each block is divided into three blocks (D, (II), and (III)) as shown in Figure 5 and the following table. The detection range of the image interval error type to be detected is designed to overlap. [Left below margin] In Fig. 4 again, the AP switch (AF SW)
When is turned on, #1. #2. Step #18. In #19, every third difference data is created from the pixel data of the base Q part (L) and the reference part (R). The purpose of this process is to remove low-frequency error factors in the spatial frequency of the illuminance distribution on the standard part (L) and reference part (R), which occur due to deviations from the design values of the ranging optical system. is JP-A-60-49
Since it is explained in Publication No. 14, the explanation will be omitted. Next #20. Using the second block (It) in #21,
Calculate the correlation between the standard part (L) and the reference part (R) in four ranges at ±lO pitch from focus, and calculate LM2 indicating the position of the area within the reference part (R) with the highest correlation. . #
#20 in 22. ; It is determined whether the correlation calculation in #21 is highly reliable, that is, whether it is detectable. If it is determined that detection is possible, a highly accurate image interval deviation ffi p 2 is calculated after interpolation calculations in #23 and #24. In #25, before performing the correlation calculation using the first block (1), the amount of image interval deviation in pitch units obtained in the second plot (n) is calculated using the first block (1), which can be calculated by interpolation. Determine whether it is within the range of correlation calculation using D. 12M
If 2<II, the amount of image interval deviation obtained in the second block (If) from the detection range in the first block (I) indicates what is known as a pin, so it is set as the first block (1). #28. over the entire detection area, i.e. from -4 to +14 pitches. Correlation calculation is performed in #29, and L M + indicating the position of the region within the reference portion with the highest degree of correlation is calculated. Similar steps are also performed when it is determined in #22 that the correlation calculation in the second block (II) is undetectable. If 4M2≧11 is determined in #25, #26. In #27, the correlation calculation for calculating the front focus from the image interval shift amount obtained in the second block (II) is omitted, and the correlation calculation is performed to calculate the area in the reference part (R) with the highest degree of correlation. Calculate ρM, which indicates the position. At #30, it is determined whether or not the correlation calculation in the first block (1) is undetectable. If it is determined that detection is possible, a highly accurate image interval deviation amount P1 is calculated after interpolation calculation in steps #31 and #32. When calculating this image interval deviation ff1P, xM, -4 is corrected by +a in order to reduce the influence of distortion possessed by the focus detection optical system, which is a feature of the present invention. Regarding this correction in #32,
The correction in #42 of the third block (III) will be explained in detail later. Next, #38. In #39, correlation calculation is performed using the third block (III), but the image interval deviation amount obtained in the first block (1) is within the image interval deviation amount detection area set in the third block (III). Moreover, since it is a rear pin area, #38. In the scope of the correlation calculation in step #39, the part in which surface bins are calculated from the amount of image interval deviation obtained in the first block (1) is omitted in order to save time. Although it is omitted in the flowchart in Figure 4, (1M+
If ≧8 and the detection area exceeds the detection area where interpolation calculation is possible in the third block (Iff), #38. Skip #39 and proceed to #40. If it is determined in #30 that the correlation calculation in the first block (1) is undetectable, then in #33 it is determined whether the correlation calculation in the second block (II) is undetectable. If detectable, #34. In #35, correlation calculation is performed while omitting the part in which the front focus is calculated from the image interval deviation amount obtained in the second block (n). Although omitted in the flowchart of Fig. 4, Q M t
≧18, and if it exceeds the detection area where interpolation calculation is possible in the third block (1), #34. Skip #35 and proceed to #40. If it is determined in #33 that the correlation calculation cannot be detected in the second block (II), correlation calculation is performed over the entire detection area set as the third block (III) in #36 and #37, and the correlation calculation is performed to find the highest degree of correlation. Indicates the position of the area within the high reference area (calculate M3. Next, in #40, the third
It is determined whether correlation calculation by block ([) cannot be detected. If it is determined that detection is possible, a highly accurate image interval deviation ff1p3 is calculated after interpolation calculation in #4+ and #42. In #42, as in #32, in order to reduce the influence of distortion that the focus detection optical system has,
Three HIs of +h are performed for M, -24. Regarding this correction, #32 in the first block (I)
This will be explained in detail later along with the correction in . Next, in #43, the image interval deviation ff1P calculated so far
+, P2. The largest value of P3, that is, the value indicating the most posterior focus, is determined as the true value P of the image interval deviation m. At this time, P,,P3. If any of P3 is undetectable, exclude it and calculate the maximum value of the detectable values as P
Find it as. Next, from #13 onwards, steps similar to those described in FIG. 3 are executed. If it is determined in #40 that detection is not possible, it is determined in #44 and #45 whether or not detection is not possible in the first block (I) and second block (n). If it can be detected by either, the process goes to #43 and the true image interval value P is calculated. 1st. Second. Any third block (I
), (II), and (III), it is determined that the detection is impossible as a whole, and the steps from #10 onward are executed in the same manner as described in FIG. Next, #32 to reduce the influence of distortion of the focus detection optical system. The correction in #42 will be explained. As already mentioned, the optical system shown in FIG. 10 includes a condenser lens (6), a reimaging lens (8),
If O) is constructed with a spherical lens, considerable distortion will occur if contrast exists only in the distance measurement area, that is, at the end of the reference part (L), as shown in FIG. In other words, if the contrast is not distributed over the entire area but is unevenly distributed in one part, the focus state of the lens is equal and the reference part (L
) depending on where the contrast is present in the CCD.
The above image interval value changes, and therefore the amount of defocus determined by the focus detection calculation also changes. This phenomenon is particularly affected by the condenser lens (8), and if it is constructed with an aspherical lens, the distortion can be improved to a level 1, as shown by the dotted line in Figure 14, but it is difficult to eliminate it completely. Moreover, it is difficult from a cost and manufacturing perspective. As in the embodiment of FIG. 4, the first part of the reference part (L). When using the third block (I) or (III), the reference part (L)
Since we use areas that are tilted to the left and right, rather than the center of the whole, the influence of the distortion shown in FIG. 14 is not ignored. For this reason, the first and third blocks (D, (III
) is used to correct distortion. Figure 6 is; #31. The details of the interpolation calculation in #41 and its correction are shown. #32 in FIG. Distortion is corrected in #42. As shown in FIG. 2, the first. Third block (1). If (III) is set, normally it will be a-b, but if it is made asymmetrical, it will be af-b. Note that #I02 in FIG. #IO] and #IO3 are not shown in the flow of FIG.
) is recalculated, thereby enabling focus detection of 0.5 pitch at both ends before and after the minimum value of n. This is a flowchart showing a part of the image interval detection area on the focus side after correlation calculation using the first block (1) in FIG. 4, when the second block (n) is undetectable and when it is detectable. In this second embodiment, in order to improve the detection probability as much as possible, taking into account that the focus is largely out of focus when detection is not possible in the second block (n), , the image interval detection area is widened. On the other hand, if it is possible to detect the image in the second block (II), taking into consideration the competing objects in the distance and near, Correlation calculations are also performed on the pin side, but in the case of the former, there is no need to detect over a wide area, so the detection area is narrowed to save time. In Figure 7, the second block (II) is #22. If it is determined that the correlation calculation cannot be detected in , r: (=0
~Il+ area two area hoe #28. Correlation calculation is performed in #29, but if it is determined that detection is possible, #46. #, 17,448° #49 and #28. #2
9, the correlation calculation is performed only in the region of relative pitch moe pin, where a≦12. FIG. 8 is a flowchart showing a part of the third embodiment of the present invention, and in #43 in FIG. 4, the true value P of the image distance value is
This is a modification of the content of the calculation to find . In the embodiment shown in Fig. 4, the obtained image interval deviation value is used as a measure against distance conflict, which indicates that the subject is closest to the lens, but in reality, even if a flat subject is measured, When the object contrast decreases, an error occurs in the detected image interval deviation ↑, and there are cases where the accuracy decreases. The present embodiment was implemented as a countermeasure against this problem, and the Max
If the difference between (P+, P2, P3) and the image interval deviation mP4 due to the block with the highest contrast is within a certain value, P4 is used as the true image interval deviation amount. In FIG. 8, #50 indicates 1.12. The maximum value (Max value) of the image interval deviation amount obtained in the third block (1), (II), and (III) is P. Calculated as follows. Next #51. #52. #53, 1st. Second. Difference data Q for each third block (I), (II), (I[)! Sk
), the total contrast value C,,C2,C. is calculated. Furthermore, in #54 to #58, the 1st degree and the 2nd degree.
The image interval deviation amount of the third blocks (1), ([1), and (III) with the maximum contrast is calculated as P4. Next, #59, P4 and P. The difference between
If the difference is within a certain value A, the image interval deviation ffi P4 of the block with high contrast is the true image interval deviation f
It is obtained as f1P. If the difference is larger than A, Po-MaX (P+, P
2, P3) is determined as the true image interval deviation ff1P. FIG. 9 is a flowchart showing a part of the fourth embodiment of the present invention. In this embodiment, for the purpose of time reduction, correlation calculations are performed by selecting two blocks with high contrast among the three blocks (1), (II), and (III) of the base ω portion. Furthermore, if the contrast value of each block (1), (II), (I) is less than the constant value B, the reliability of detection is considered to be low and it is considered that detection is impossible, and no correlation calculation is performed. In Fig. 9, the AP switch (AF SW) is set to O.
When it is N, #I to #53 are shown in the same way as explained in Fig. 4 and Fig. 8.
The difference data (QSk, rSk) and the contrast values c, , C, , C3 of each block a-7 are calculated. #6
In step 4, it is determined whether the second block (n) has the smallest contrast among the three blocks. When it is determined that the contrast is minimum, the correlation calculation in the second block (n) is not performed and the first block (1) after #68 is performed.
Let's start the correlation calculation. If it is not the minimum, it is determined in the next step #65 whether the contrast of the second block ([) is equal to or greater than the contrast limit value 3. If it is less than B, the correlation calculation begins in the first block (I) starting from #68. 166 if B or higher
, #67 performs correlation calculation, and #22 calculates the second block (n
) is highly reliable, that is, whether it is detectable or not. When it is determined that it is detectable #
23. After the interpolation calculation in #24, the image interval deviation amount P due to the second block (n) is calculated. Next, the correlation calculation begins in the first block (1) starting from #68. The same applies when it is determined in #22 that detection is not possible. #68. #69 and #64. Similar to #65, the contrast C1 of the first block (1) is different from that of the three blocks (+), (II), (II).
It is determined whether the contrast of I) is not the minimum or whether the contrast is equal to or greater than the contrast limit value 3. If any of the conditions are not satisfied, proceed to the first block (I).
The correlation calculation in the third block (I) is entered without performing the correlation calculation. If both conditions are satisfied, #70. Correlation calculation is performed in #71, and in #30 it is determined whether detection is possible in the first block (I). #3 if detectable
1. After the interpolation calculation is performed in #32, the image interval deviation amount P1 due to the first block (1) is calculated. When calculating this image interval deviation IF, errors due to distortion of the focus detection optical system are corrected. Next, the third block after #72 (■
) correlation calculation/\enter. If it is determined that detection is not possible in #30, interpolation calculation is not performed and the process proceeds to #72 and subsequent steps. #72
Hereafter, et al. After checking the contrast as in the case of the second blocks (I) and (n), the F[] function calculation is performed #42, and the amount of image interval deviation P due to the third block ([),
is calculated. This image distance 1, bow 1) (HaTakenaka l
Errors due to distortion in the optical system are corrected. Below, the fourth
The lens is driven in the same way as the steps in the figure. In the above embodiment, in order to reduce the influence of distortion of the focus detection optical system, the image interval deviation ff1P is
. Effects of the Invention According to the present invention, among the first and second optical images of an object whose image interval changes according to the focus adjustment state of the objective lens, the illuminance distribution of the first optical image is The first photoelectric conversion element array that generates the output is divided into a plurality of blocks, and the focus adjustment state data is corrected by the distortion component of the focus detection optical system depending on the block used for focus detection. By electrical correction calculation, focus detection can be performed correctly without being affected by distortion of the focus detection optical system.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the focus detection device according to the present invention, FIG. 2 is an explanatory diagram of a line sensor used in the focus detection device of FIG. 1, and FIGS. 1 is a flowchart showing the basic operation flow of the focus detection device and the operation flow in the first embodiment of the present invention, and FIG. 5 is a flowchart showing the detection range of the image interval error amount in each block of the line sensor. FIG. 6 is a flowchart showing the details of the interpolation calculation step and the correction step in the flowchart of FIG. 4; FIGS. 10, 11, and 12 are explanatory diagrams of the optical system of the focus detection device and the focus detection principle, and FIGS. 13(a), (b), and (c) respectively.
and FIG. 14 are explanatory diagrams of distortion that the focus detection optical system has. 2...Objective lens, 4...Planned focal plane, 6...
Condenser lens, 8.10...imaging lens, ! 5... Line sensor (L... basic part, R...
Reference section. I... 1st block, ■... 2nd block, ■...
・3rd block). 20...Photoelectric conversion circuit, 30...Microcomputer. Patent Applicant: Minolta Camera Co., Ltd. Agent: Patent Attorney: Mr. Maeda and 2 others Figure 10 +2i! i Fig. 13 (C) Line 7' cer 12 Line sen size -14 degree line cer 12 Finn's = I4 shin, sword [

Claims (3)

[Claims] (1) A condenser lens placed near the intended image formation plane of the objective lens, and a condenser lens placed behind the condenser lens symmetrically with respect to the optical axis of the objective lens, and a focus adjustment state of the objective lens via the condenser lens. first and second imaging lenses that form first and second optical images of an object whose image distance changes according to the image distance; The first that generates the output
The second photoelectric conversion element array and the first photoelectric conversion element array are divided into a plurality of blocks, and the focus adjustment state of the objective lens is determined by the correlation with the pixels of the second photoelectric conversion element array corresponding to each block. a data calculation means for calculating data corresponding to the data, a selection means for selecting data from which block among the plurality of blocks is to be used as focus adjustment state data, and a focus detection optical system corresponding to the selected block. and a correction means for correcting focus adjustment state data by a distortion component caused by distortion. (2) The selection means selects only the block with the maximum contrast, and the correction means corrects the focus adjustment state data by a distortion component corresponding to the selected block. The focus detection device described in . (3) The selection means determines the centroid position of the luminance distribution of the first photoelectric conversion element array, selects the block to which this centroid position belongs, and the correction means corrects only the distortion component corresponding to this selected block. The focus detection device according to claim 1, wherein the focus detection device corrects focus adjustment state data.