JP2712412B2 - Focus detection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a focus detection device such as a camera.

[Prior Art] A pair of subject images formed by light beams passing through different portions of a photographing optical system are photoelectrically converted by a pair of photoelectric conversion means to obtain a subject image signal composed of a pair of discrete data. A focus detection device that performs a predetermined correlation operation while relatively shifting the subject image signal, searches for the shift amount having the highest degree of correlation, and calculates the defocus amount of the photographing optical system from the shift amount (shift amount). Are known.

Such a focus detection device will be described with reference to FIGS.

FIG. 6 shows an embodiment in which a conventional focus detection device is applied to an interchangeable lens single-lens reflex camera, and an interchangeable lens 10 can be detachably mounted on a camera body 20. I have.

In a state where the lens 10 is mounted, a photographic light beam coming from a subject passes through the photographic lens 11 and is partially reflected upward by a main mirror 21 provided on a camera body 20 and guided to a finder (not shown).

At the same time, another part of the photographing light beam is transmitted through the main mirror 21 and further reflected by the sub-mirror 22, so that the light beam is guided to an autofocus module 23 (hereinafter, referred to as an AF module) as a light beam for focus detection.

 FIG. 2 shows a configuration example of the AF module 23.

In FIG. 2, the AF module is a focus detection optical system including a field lens 27 and a pair of re-imaging lenses 28A and 28B.
24, and a CCD (charge coupled device) 25 having a pair of light receiving sections 29A and 29B.

In the above configuration, the light flux passing through the pair of regions 18A and 18B symmetric with respect to the optical axis 17 included in the exit pupil 16 of the photographing lens 11 is formed as a primary image near the field lens 27, and furthermore, the field lens 27 and A pair of secondary images are formed on a pair of light receiving sections of the CCD 25 by the re-imaging lenses 28A and 28B. When the primary image coincides with a predetermined focal plane (not shown), which is a conjugate plane of the film, the image is in focus, and the relative position of the pair of secondary images in the light receiving portion arrangement direction on the CCD 25 is determined by a focus detection optical system. Is a predetermined value determined by the configuration of.
Note that the pair of light receiving units 29A and 29B are respectively n light receiving elements Ai,
The light receiving elements (A ₁ and B ₁ , A ₂ and B _2, ...) Corresponding to the case where the primary image is made of Bi (i = 1 to n) coincide with the film conjugate plane.
..) Are arranged to be equal.

When the imaging plane of the primary image is located on a plane shifted from the film conjugate plane, the relative positions of the pair of secondary images on the CCD 25 are shifted in the optical axis direction of the primary image (that is, forward). The value is changed from the predetermined value in the case of the coincidence according to the pin or the post-pin. For example, in the case of a rear focus, the positional relationship between a pair of secondary images is relatively widened and in the case of a front focus, it is narrow.

The light receiving elements Ai and Bi forming the light receiving sections 29A and 29B are configured by charge storage elements such as a fort diode, and the charge storage is performed only for a charge storage time according to the illuminance on the CCD 25, and the output of the light receiving elements is described later. Output level suitable for the above processing.

 Returning to FIG. 6, the description will be continued.

The sensor control means 26 is a focus detection calculation means (AFCPU) 30
Receiving the charge accumulation start and end commands from the port P4 of the CCD 25 and giving a control signal corresponding to the command to the CCD 25,
Control the start and end of charge accumulation and apply a transfer clock signal to the CCD25
Transfer to PU. When a light-receiving element output signal is generated, the sensor control means 26 sends a synchronization signal to the port P4 of the AFCPU 30,
The FCPU 30 starts the A / D conversion by the built-in A / D conversion means in synchronization with the generated synchronizing signal. Conversion data (2n
G), a well-known focus detection calculation (correlation calculation) described later is performed based on the data to obtain a defocus amount corresponding to a difference between the image forming plane of the primary image and the film conjugate plane.

The AF CPU 30 controls the display mode of the autofocus display means (AF display means) 40 using the port P5 based on the focus detection calculation result. For example, in the case of the front pin, the triangle display section 41
The AF CPU 30 controls the AF display means 40 to activate the triangular display section 43 for rear focus, the circular display section 2 for focus, and the cross display section 44 for focus detection failure. I do.

The AF CPU 30 also determines the AF motor 50 based on the focus detection calculation result.
The driving direction and the driving amount are controlled to move the photographing lens 11 to the focal point.

First, the AF CPU 30 generates a drive signal for rotating the AF motor 50 from the port P2 in the direction in which the taking lens 11 approaches the focal point according to the sign of the defocus amount (front focus, rear focus).
The rotational movement of the AF motor is transmitted to a body-side coupling 53 provided on a mount portion of the body 20 and the lens 10 via a body transmission system 51 including a gear built in the body 20 and the like.

The rotation transmitted to the coupling 53 on the body side is further coupled to the coupling 14 on the lens side and the lens.
The photographic lens 11 is transmitted to a lens transmission system 12 constituted by gears and the like built in 10, and finally moves in the focusing direction.

The drive amount of the AF motor 50 is fed back to the AF CPU 30 from the port P1 by converting the rotation amount of the gears and the like of the body transmission system 51 into the number of pulses by an encoder 52 constituted by a photo interrupter or the like.

That is, the AF CPU 30 controls the driving amount of the AF motor 50, that is, the number of pulses fed back from the encoder 52, in accordance with parameters such as the speed reduction ratio of the body transmission system 51 and the lens transmission system 12, thereby setting the photographing lens 11 to a predetermined value. It can move by the moving amount.

The AFCPU 30 has a built-in pulse counter for counting the number of pulses input from the port P1 and a comparison register for comparison with the contents of the pulse counter. It has a function that includes

The AF CPU 30 controls the driving amount of the AF motor 50 in the following order. First, before the driving of the AF motor 50 is started, the contents of the pulse counter are cleared and the desired number of pulses is set in the comparison register.

 Next, driving of the AF motor 50 is started.

The encoder 52 generates a pulse by the rotation of the AF motor 50, and this pulse is counted up by a pulse counter.

When the content of the pulse counter matches the comparison register, an interrupt occurs and the AF CPU stops the AF motor in the interrupt processing. In this way, the AF motor is driven and controlled by a desired number of pulses.

The lens CPU 13 is built into the lens 10, and the AF CPU 30
Necessary information (for example, AF-related information such as the number of rotations of the coupling 14 per unit movement amount of the photographing lens 11) is transmitted to a body-side communication bus via a lens-side contact 15 provided with a mount portion and a body-side contact 63. Send to 64.

The AF CPU 30 transmits AF-related information from the lens CPU 13 to the communication bus 64.
Received from port P6 connected to

The outline of the focus detection calculation such as the correlation calculation in the AF CPU 30 will be described below with reference to FIGS. 8, 9, and 10.

The light receiving elements Ai and Bi (i
Assuming that ai and bi (i = 1 to n) are the CCD data (difference in some cases) corresponding to = 1 to n), the correlation amount C (L) is obtained by the correlation operation shown in Expression (1).

However, in the equation (1), L is an integer and is a relative shift amount (shift amount) in units of a pitch of a pair of CCD data light receiving elements. Further, the range taken by the parameter i in the correlation operation of the equation (1) is appropriately determined according to the shift amount L and the number n of data.

When the CCD data ai, bi is made to correspond to the matrix of the matrix, for example, as shown in FIG.
It is possible to determine a combination of data, that is, a range of the parameter i. In FIG. 10 (A), the shift amount L is -4 to
The combination of the CCD data which is changed in the range of +4 and is operated by each shift amount L by "*" and "0" is represented by a position on the matrix. When set in this way, the range taken by the parameter i is as follows.

INT ((L + 1) / 2 + 3) ≦ i ≦ INT ((L + 1) / 2 + n−2) (2) Further, as shown in FIG. 10 (B), the range of the parameter i can be determined. In this case, the range taken by the parameter i is as follows.

L ≦ i ≦ n (L ≧ 0), 1 ≦ i ≦ n + L (L <0) (3) The calculation result of equation (1) is obtained by taking the relative shift amount L on the horizontal axis in FIG. As shown by the amount C (L) on the vertical axis, the correlation amount C (L) is minimized at the shift amount L where the correlation between the pair of CCD data is high.

However, the relative shift amount L is actually equal to the light receiving units 29A and 29A.
Since it is determined based on data discretely obtained from the light-receiving elements constituting 9B, the correlation amount C (L) itself is also discrete. Therefore, the minimum value of the correlation amount C (L) is not always directly obtained from the correlation amount C (L) obtained by the calculation.

Therefore, the correlation amount C is calculated using the three-point interpolation method shown in FIG.
Find the minimum value C (x _m ) of (L).

That is, assuming that the minimum value of the correlation amount C (L) obtained discretely is obtained when the relative shift amount L is L = x, it corresponds to the relative shift amounts x-1, x, x + 1 before and after the relative shift amount L. The correlation amount C (L) is C (x-1), C (x), C (x).
(X + 1). Therefore, first, the minimum correlation amount C (x) of the obtained data and the remaining two correlation amounts C (x
-1) and C (x + 1), a straight line H connecting the larger correlation amount (C (x + 1) in FIG. 9) is drawn. Is drawn, and the intersection W of these two straight lines H and J is determined.

The coordinates of the intersection point W is the correlation shift value x _m, the correlation amount C
(X _m ), and a correlation shift value x _m that maximizes a correlation state for a continuous shift amount by the coordinates.
And the minimum correlation amount C (x _m ) can be determined.

If the three-point interpolation method is expressed by an arithmetic expression, the correlation shift value
x _m is And the correlation amount C (x _m )
Is represented by the following equation: C (x _m ) = C (x) − | D | (5)

Here, in the equations (4) and (5), D is Can be represented by

In equations (4) and (5), SLOP is the correlation amount C (x−x) corresponding to the relative shift amounts x−1, x, x + 1.
1), C (x), and C (x + 1), which represent the larger of the deviations, and is expressed by the following equation: SLOP = MAX (C (x + 1) -C (x), C (x-1) -C (x )) ... (7)

(4) correlation shift amount obtained by the equation x _m represents a relative shift amount of the CCD data pair, if the pitch of the light receiving element and y, relative to the two object image formed on the CCD25 The typical lateral shift amount g can be expressed as g = y × x _m (8).

 The defocus amount DEF on the focal plane can be approximated as in the following equation: DEF = KX × g (9)

Here, KX is a coefficient determined by the configurational conditions of the focus detection optical system shown in FIG.

The larger the value of the parameter SLOP obtained by the equation (7), the deeper the depression of the correlation amount C (L) shown in FIG. 8, that is, the larger the correlation. Therefore, the obtained defocus amount DE
This shows that F has high reliability.

Next, a specific method of obtaining the shift amount L will be described.

FIG. 11 shows that the number n of the CCD data is 16, and the range of the shift amount L is −1.
After setting from 2 to +12, the combination of the CCD data ai and bi used in the correlation calculation is represented by “*” and “0” on the matrix. In this case, for each shift amount L, there are four pairs of ai and bi used in the correlation operation of equation (1). When the extreme value of the correlation amount C (L) appears when the shift amount L = 0, the photographing lens is in focus and the defocus amount is almost zero. The absolute value of the amount of defocus of the photographing lens increases as the shift amount L moves away from 0.

FIG. 12 shows a shift amount L and a correlation amount C when a certain subject image is formed near a focal point by a photographing lens.
(L) is represented by a graph. In this figure, when the shift amount L = -1, the correlation amount C (L) has the lowest value. In addition, it can be seen that the drop of the correlation amount C (L) is sharp near the shift amount L = −1.
K shown on the left side of the figure indicates the order in which the correlation calculation is performed with the shift amount L, and indicates that the calculation is performed from L = -12 to L + 12 by increasing L by one.

On the other hand, FIG. 13 is a graph showing the relationship between the shift amount L and the correlation amount C (L) in the case where the subject image is largely defocused and formed for the same subject. In this figure, when the shift amount is L = + 6, the correlation amount C
(L) indicates the lowest value. In the vicinity of the shift amount L = 6, the drop of the correlation amount C (L) is not abrupt but gentle as shown in FIG. 7, and the maximum shift amount L = −12 at both ends is obtained.
Even at +12, the correlation amount C (L) is not as large as in FIG. In other words, when the subject image is formed with a large defocus, the high spatial frequency component is removed and the image becomes only the low frequency component, so that the peak indicating the correlation state becomes gentle.

Based on the defocus amount obtained in this way, the imaging position of the subject image through the photographing lens 11 is sequentially monitored,
The photographing lens 10 is focused on a target subject.

[Problems to be Solved by the Invention] In the above-described related art, when a predetermined correlation operation is performed while relatively shifting a pair of subject image signals, and a shift amount with the highest degree of correlation is searched for, a pair of subject image signals are detected. If the number of combinations of the relative shifts of the subject image signal is large, the correlation calculation is performed for all the shift amounts, so that the calculation amount becomes enormous, and as a result, the calculation time increases. There is a problem that the responsiveness of the device is reduced.

In addition, when the photographing lens is out of focus and the absolute value of the defocus amount is large, that is, when the absolute value of the shift amount L is large, the extreme value of the correlation amount C (L) is searched for. It is not necessary to take the variation of the quantity L finely. When the absolute value of the defocus amount is large, it is not necessary to calculate the defocus amount with high accuracy. In some cases, it is only necessary to detect the positive or negative of the defocus amount. It did not need to be as fine as the near focus.

On the other hand focus near to correlating shift value X _m which gives the defocus amount of precision in accordance with equation (4), there is necessary to obtain the correlation amount C (L) by variation of possible fine shift amount L Was.

Means for Solving the Problems The present invention provides a focus detection optical system that forms a pair of subject images by subject light passing through different optical paths, and generates a pair of subject image signals by receiving the pair of subject images. A pair of photoelectric conversion means, a conversion means for converting the pair of subject image signals into a pair of subject image data, and a correlation amount between the pair of subject image data while relatively shifting the pair of subject image data. And a correlation calculating means for calculating, wherein the correlation calculating means relatively shifts the pair of subject image data at a first pitch when the shift amount is within a predetermined range. Calculating a correlation amount between the pair of subject image data, and when the shift amount is out of the predetermined range, relatively shifting the pair of subject image data at a second pitch larger than the first pitch; Meanwhile, the correlation amount between the pair of subject image data is calculated.

[Operation] In the present invention, since the focus detection device is configured as described above, the change amount of the shift amount (the change amount of the shift amount within the first shift amount range that provides the defocus amount near the in-focus state where accuracy is required) Outside the range of the first shift amount that gives a large defocus amount away from the focal point where the precision is not required, but the precision is not so required, the change amount (pitch) of the shift amount can be increased, and therefore the calculation time can be increased. Can be shortened.

Embodiment FIG. 1 schematically shows a focus detection device 100 of the present invention. An optical system for guiding an image of a subject to a focus detection optical system 24,
Reference numerals 21 and 20 are the same as those of the prior art described above.

The two light beams from the subject reflected by the sub-mirror 22 in the camera body are guided to a focus detection optical system 24 similar to that shown in the prior art, and each light beam forms a primary image and a secondary image.

The photoelectric conversion means 25 'generates a pair of subject image signals corresponding to the light intensity distribution of the pair of secondary images. This is achieved by a CCD 25 and sensor control means 26 similar to those shown in the prior art.

The focus detection calculation means 30 'corresponds to the AF CPU 30 shown in the prior art, and in some cases, performs the AD conversion of the subject image signal, and in some cases, calculates the difference between the subject image signals after the AD conversion (the subject image signal with respect to the shift amount). Is calculated. Further, a pair of subject image signals are relatively shifted by a predetermined shift amount L according to a predetermined program to perform a correlation operation, and a correlation shift value x _m that maximizes a correlation state between the pair of subject image signals. It was determined from these correlation calculation, and calculates a defocus amount corresponding to the difference from the correlation shift value x _m and position of the planned focal plane of the imaging plane of the photographing lens 11.

In the present invention, the focus detection calculation means (AFCPU) 3
It has a feature in the operation of 0 '.

Hereinafter, the operation of the AF CPU 30 'in the first embodiment will be described with reference to FIG.

FIG. 2A is a part of a flowchart of the correlation calculation performed inside the AF CPU 30 ', and FIG. 2B is a flowchart showing the second focus operation for the same focus state as when the correlation graph of FIG. 12 was obtained. It is a graph showing the relationship between the shift amount L and the correlation amount C (L) obtained when the embodiment of FIG.

FIG. 2A is a flowchart applied when the camera is pointed at the subject and the photographing lens is at a certain focal position, and is used for sequentially monitoring the image forming position in response to an external focusing operation command. It is a flowchart.

Correlation calculation starts at a certain focal position, and is # 100
Sets the initial value of the shift amount L to -12.

Next, in # 105, the correlation amount C (L) is calculated from the set shift amount L by the equation (1) and the like.

In step # 110, a test is performed to determine whether the currently set shift amount L has reached 12, and if the shift amount has reached 12, the processing exits from the correlation operation loop. If the shift amount L has not become 12, #
At 115, it is tested whether the shift amount L satisfies either condition of L <−4 or L ≧ 4 (out of the range of the first shift amount). In step # 120, the increment Δ is set to 1 and the process proceeds to step # 130.

On the other hand, when the condition is satisfied in # 115, that is, when the shift amount L corresponds to the state where the absolute value of the defocus amount is large, the increment Δ is set to 2 in # 125 and the process proceeds to # 130.
In # 130, the shift amount L is updated by adding the increment Δ to the current shift amount L, the process returns to # 105, and the above operation is repeated.

Finally, the correlation amount C (L) up to the shift amount L = 12
Is calculated and the process exits the correlation calculation loop in # 110. After that, the smallest (larger) value is selected from the correlation amounts C (L) obtained, and the correlation shift value _Xm is obtained as described with reference to FIGS. 8 and 9, and finally the defocus amount is calculated. And use it to display defocus as described above,
The lens is driven. As shown in FIG. 2 (B), when the correlation operation is performed in order from K = 1 to 17, the shift amount L is also -12, -10, -8, -6, -4, -3, -2. ...
It changes to 2,3,4,6,8,10,12. When the shift amount L indicating the lowest value of the correlation amount C (L) is found in the range of variation 1 as shown in FIG. 2 (B), the correlation shift value X _m is obtained as described above.
Can be requested. If the shift amount L indicating the lowest value of the correlation amount C (L) is not found in the variation 1 (first pitch) around the shift amount L = 0 corresponding to focusing,
The correlation amount C (L) and re-correlation calculation as variation 1 (first pitch) again in the vicinity of the shift amount L, may be obtained correlation shift value X _m in the same manner as described above , may be employed shift amount L indicating the minimum value as a direct correlation shift value X _m as accuracy is not so required because originally defocus amount absolute value is large.

Hereinafter, a second embodiment of the present invention will be described with reference to FIG. (The second embodiment also includes the same focus detection optical system 24, photoelectric conversion means 25 ', AFCPU 30', etc. as in the first embodiment.) FIG. 3A shows the correlation calculation performed inside the AFCPU 30 '. FIG. 3B is a part of the flowchart of FIG.
It is obtained when the flowchart shown in FIG. 3A is applied to the same state as when the correlation graph of FIG.
It is a graph showing the relationship between the shift amount L and the correlation amount C (L).

In FIG. 3A, first, at # 200, the initial value of the shift amount L is set to 0, and the initial values of the variables LP and LM are set to L, that is, 0.

Next, in # 205, the correlation amount C (L) is calculated by the equation (1) or the like with respect to the set shift amount L.

In step # 210, a test is performed to determine whether the currently set shift amount L has become -12. If the shift amount L has become -12, the process exits the correlation calculation loop.

If not −12, the shift amount L is L># 215.
It is tested whether the condition of 0 is satisfied. If the condition is not satisfied, that is, if it is L in the back focus state, the variable LP is set to LP in # 220.
It is tested whether the condition of .gtoreq.4 is satisfied. If the condition is satisfied, that is, if the LP has a large absolute value of the defocus amount, the increment .DELTA.

If the variable LP does not satisfy the condition of LP ≧ 4 in # 220, that is, if the LP is in the vicinity of focusing, the increment Δ is set to 1 in # 230 and the process proceeds to # 235.

At # 235, the variable LP is updated by adding the increment Δ to the current variable LP, and further, at # 236, the shift amount L is set to the variable LP, the process returns to # 205, and the above operation is repeated.

On the other hand, when the condition of L> 0 is satisfied in # 215, that is, when L is in the previous focus state, the variable LM is set to LM in # 240.
It is tested whether or not the condition of ≦ −4 is satisfied. If the condition is satisfied, that is, if the absolute value of the defocus amount is a large LM, the increment Δ is set to −2 in # 245 and the process proceeds to # 255.

If the variable LM does not satisfy the condition of LM ≦ −4 in # 240, that is, if the variable LM is in the vicinity of focus, the increment Δ is set to −1 in # 250 and the process proceeds to # 255.

At # 255, the variable LM is updated by adding the increment Δ to the current variable LM, and further, at # 256, the shift amount L is set to the variable LM, the process returns to # 205, and the above operation is repeated.

Finally, the correlation amount C up to the shift amount L = -12
When (L) is calculated and obtained, the process exits from the loop of the correlation calculation in # 210. After that, the smallest (larger) value is selected from the correlation amounts C (L) obtained, and the correlation shift value _Xm is obtained as described with reference to FIGS. 8 and 9, and finally the defocus amount is calculated. Then, the defocus display and the lens drive are performed by using them as described above. As shown in FIG. 3 (B), when the correlation calculation is performed in order from K = 1 to 17, the shift amount L is also 0,1, −1,2, −2,3, −3,4, −. 4,6, −6,
8, ... 12, -12.

If the shift amount L indicating the lowest value of the correlation amount C (L) is found in the variation 1 range (the range of the first pitch shift amount) around the shift amount L = 0 corresponding to focusing, it is possible to obtain the immediate shift value X _m as. FIG. 3 (B)
When the shift amount L indicating the lowest value of the correlation amount C (L) is not found in the range of variation 1 (the range of the shift amount of the first pitch), the variation in the vicinity of the shift amount L is renewed. The correlation operation is performed again at 1 (pitch 1) to obtain the correlation amount C (L)
Look, may be the correlation shift value X _m in the same manner as described above, originally defocus amount absolute value is large state because precision direct correlation shift value shift amount L indicating the minimum value as not so much necessary X _m can also be adopted.

Hereinafter, a third embodiment of the present invention will be described with reference to FIG. (The third embodiment also includes the same focus detection optical system 24, photoelectric conversion means 25 ', AFCPU 30', etc. as in the first embodiment.) FIG. 4A shows a correlation operation performed inside the AFCPU 30 '. FIG. 4 (B) is a part of the flowchart of FIG. 4 (A) for the same state as when the correlation graph of FIG. 13 was obtained.
7 is a graph showing the relationship between the shift amount L and the correlation amount C (L) when the flowchart shown in FIG.

In FIG. 4A, first, at # 300, the initial value of the shift amount L is set to -12, and the initial value of the increment Δ is set to 5.

Next, in step # 305, a correlation amount C (L) is calculated with respect to the set shift amount L using the equation (1) and the like.

In step # 310, it is tested whether or not the currently set shift amount L has reached 12, and if it has reached 12, the process is skipped from the correlation operation loop. If it is not 12, it is tested in # 315 whether the shift amount L satisfies either condition of L <−4 or L ≧ 4. At 325, the increment Δ is set to 1 and the process proceeds to # 340.

On the other hand, when the condition is satisfied in # 315, that is, when L is a state in which the absolute value of the defocus amount is large, #
At 320, it is tested whether the shift amount L is L <−4, and L <−
If it is 4, the increment Δ is updated by subtracting 1 from the current increment Δ in # 330. If L <−4 is not satisfied in # 320, the flow proceeds to # 335, where 1 is added to the current increment Δ to update the increment Δ.

In # 340, the shift amount L is updated by adding the increment Δ to the current shift amount L, and the process returns to # 305 to repeat the above operation.

Finally, the correlation amount C (L) up to the shift amount L = 12
Is calculated and the processing exits from the correlation calculation loop in # 310. After that, the smallest (large) value is selected from the correlation amounts C (L) obtained, and the correlation shift value _Xm is obtained as described with reference to FIGS. 8 and 9, and finally the defocus amount is calculated. , Using it to display defocus as described above,
The lens is driven. As shown in FIG. 4 (B), when the correlation operation is performed in order from K = 1 to 13, the shift amount L is accordingly changed to -12, -8, -5, -3, -2, -1, 0, 1,2,3,5,8,12
And change. Thus, the first position corresponding to the vicinity of the in-focus state
In the range of the shift amount L, the variation is set to 1, and outside the range of the first shift amount, the variation is set to 2 as the absolute value of the shift amount increases (as the distance from the first shift amount increases). , 3,4 gradually increased. Subsequent processing is performed in the same manner as in the above embodiment.

Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG. (The fourth embodiment also includes the same focus detection optical system 24, photoelectric conversion means 25 ', AFCPU 30', etc. as in the first embodiment.) FIG. 5A shows a correlation operation performed inside the AFCPU 30 '. FIG. 5B is a part of the flowchart, and the shift amount obtained when the flowchart shown in FIG. 5A is applied to the same state as when the correlation graph of FIG. 13 is obtained. It is a graph showing the relationship between L and the correlation amount C (L).

In FIG. 5A, first, the shift amount L is -4 at # 400.
The correlation amount C (L) is calculated as variation 1 in the range of ≦ L ≦ 4. The order at that time is as shown by K = 1 to 9 in FIG. 5 (B), and the shift amount L is L = 0,1, −1,2, −2, −3, −.
3, 4, and -4, and the obtained correlation amount C (L) is indicated by "*" in FIG. 5 (B).

In # 405, the minimum value of the reliable correlation amount C (L) is-
A test is performed to find if 3 ≦ L ≦ 3. That is, in order to obtain the correlation shift value X _m described above, FIG. 8 in the range of -4 ≦ L ≦ 4, it is necessary that the dent amount of correlation shown in FIG. 9 C (L) is present The reliability is determined from the amount of depression, the degree of inclination of depression, and the like.

When a reliable minimum value of the correlation amount C (L) is found in # 405 (actually, since # 400 and # 405 operate in combination, it is not necessary to change the shift amount L to -4). If the minimum value is found at L = 0, the correlation operation may be terminated at L = 0, 1, -1.), The process skips step # 410 and exits the correlation operation loop.

When a reliable minimum value of the correlation amount C (L) is not found in # 405, for example, as shown in FIG. 12 (B), the process proceeds to # 410 and the shift amount L is set to -12 ≦ L ≦ − 6, 6 ≦
The correlation amount C (L) is calculated as variation 2 in the range of L ≦ 12. The order at that time is as shown by K = 10 to 17 in FIG. 5 (B), and the shift amount L is L = −12, −10, −8, −6, 6,
The correlation amount C (L) obtained is changed to 8, 10, and 12, and the obtained correlation amount C (L) is indicated by # in FIG. 5B.

Steps after step # 410 are the same as those in the above-described embodiment, and a description thereof will be omitted.

In the first to fourth embodiments, the correlation amount C
When calculating (L), the calculation is performed by setting the variation of the shift amount L to 1 in the range of the shift amount L near the in-focus state, and the variation of the shift amount L in the range of the shift amount L where the absolute value of the defocus amount is large. Although the calculation is performed with the minute set to 2 or more, the range of the shift amount L near the focus (for example, -4 ≦ L ≦ 4 in the embodiment of FIG. 2A) can be changed manually or automatically. You may keep it.

For example, the range of the shift amount L near the focal point may be stored as lens information for each interchangeable lens, and the range of the shift amount L near the focus point of the camera may be set based on this information. The range of the shift amount L near the camera may be set based on lens information such as the focal length of the lens.

In addition, various camera operation modes related to response time and calculation time (manual or one-shot or continuous, focus detection area is wide or multi or spot, motor winding speed is fast or slow, tracking operation for moving subject is performed. The range of the shift amount L in the vicinity of the in-focus state is changed in accordance with whether or not the change of the shift amount L is changed in the vicinity of the in-focus state and in the other range. You may.

[Effects of the Invention] In the present invention, when calculating the correlation amount C, when the shift amount is within a predetermined range, the pair of subject image data are relatively shifted at the first pitch while the pair of subject image data are being shifted. A data correlation amount is calculated, and when the shift amount is out of a predetermined range, a pair of subject image data is converted to a second image data larger than the first pitch.
Calculates the amount of correlation between a pair of subject image data while relatively shifting at a pitch of, so that even if the focus detection area expands and the number of data increases, the focus detection accuracy near the in-focus state is maintained and defocus is maintained. Until the absolute value of the amount reaches a large shift amount, detection can be performed without increasing the calculation time.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a focus detection device according to the present invention. FIGS. 2A and 2B are a flowchart and an explanatory diagram of a first embodiment of the present invention. 4B is a flowchart and explanatory diagram of a second embodiment of the present invention. FIGS. 4A and 4B are a flowchart and explanatory diagram of a third embodiment of the present invention, respectively. FIG. And (B) are a flowchart and an explanatory diagram of a fourth embodiment of the present invention, FIG. 6 is a configuration diagram of a conventional focus detection device and the like, and FIG. 7 is a description of a conventional focus detection optical system. 8, FIG. 9, FIG. 10, FIG. 11, FIG. 12, and FIG. 13 are explanatory diagrams of the focus detection calculation. [Explanation of Signs of Main Parts] 10: Photographic lens, 13: Lens CPU, 20: Camera body, 24: Focus detection optical system, 25: CCD sensor, 25 ': Photoelectric conversion means, 30, 30 ': AFCPU (focus detection calculation means), 40: AF display means, 50: AF motor, 100: focus detection device.

Claims (1)

(57) [Claims] A focus detection optical system for forming a pair of subject images by subject light passing through different optical paths; a pair of photoelectric conversion means for receiving the pair of subject images and generating a pair of subject image signals; Conversion means for converting a pair of subject image signals into a pair of subject image data; and correlation calculating means for calculating a correlation amount of the pair of subject image data while relatively shifting the pair of subject image data. In the focus detection device, when the shift amount is within a predetermined range near a shift amount corresponding to a focus position, the correlation calculating means uses the pair of subject image data as pitches of subject image data used in the correlation calculation. The relative amount of the pair of subject image data is calculated while relatively shifting at the same first pitch, and when the shift amount is out of the predetermined range, the pair of subject image data is calculated. Focus detecting apparatus characterized by calculating a correlation amount of the pair of object images data while relatively shifting a large second pitch than the pitch of the subject image data using the data in the correlation calculation.