JPS62205323A - Automatic focus detector for camera - Google Patents

Abstract

PURPOSE:To shorten an arithmetic time and to improve tracking performance for a moving subject by storing the focusing state of last focus adjustment and limiting the shift range of current correlation arithmetic operation according to the output of the stored state. CONSTITUTION:A microcomputer 30 shifts both photoelectric converting element arrays in a photoelectric converting circuit 20 in position relatively according to signals indicating the illuminance distribution of the two arrays to find the shift positions where the best correlation is obtained. In continuous AF mode, the focusing state of the last focus adjustment is stored and when focus detection arithmetic operation for the current focus adjustment is performed according to the memory output, the shifting range is limited. Therefore, when focus detection is possible within the limited shifting range, the arithmetic time can be shortened.

Description

[Detailed Description of the Invention] The present invention is a focus detection device that detects the focus state of a photographic lens by receiving object light that has passed through a photographic lens of a camera. Regarding.

The first lens of the photographic lens is symmetrical with respect to the zero optical axis.
The subject light beams that have passed through the and second regions are respectively re-imaged to create two images, and the mutual positional relationship of these two images is determined to determine the amount of deviation of the imaging position from the expected focal position and its deviation. A focus detection device has already been proposed that determines the direction (whether the imaging position is in front of or behind the expected focus position, that is, whether the focus is in front or behind). The optical system of such a focus detection device has a configuration as shown in FIG.
Alternatively, there is a condenser lens (6) located roughly behind this surface, and a reimaging lens (8) further behind that.
, (I O), each reimaging one nons (8), (I
Image sensors (+2) and (14) each having, for example, a COD as a light-receiving element are disposed on the image forming plane of O). The north image of each image sensor (12), (14,) is
As shown in Figure 7, the image of the object to be focused on (9
) and (11) are so-called front focus images that are formed in front of the planned focal plane, they are close to the optical axis (1) and close to each other,
On the other hand, in the case of rear focus, they are far from the optical axis (1). When the image is in focus, the distance between the corresponding two points of the two images (9) and (I1) becomes a specific distance defined by the configuration of the optical system of the focus detection device. Therefore, in principle, the focus state can be determined by detecting the distance between two corresponding points of the two images.

An automatic focus adjustment device for a camera with a built-in focus detection optical system of this type uses C and CD image sensors to integrate the amount of subject light, focus state detection calculation (defocus amount calculation) using COD image sensor force, and defocus amount calculation using COD image sensor force. A control circuit including a microcomputer program-controls the sequence of driving the lens according to the focus amount and stopping at one point from 2 to 3 (when the glossy release button is pressed).

This automatic focus adjustment device continuously performs the above-mentioned sequential automatic focus adjustment control even when the subject image comes close to being in focus, so that the final focus position can be set accurately. Continuous automatic focusing (AF) is performed.

The installation point that Mitsukiri is trying to solve Image sensor (+2) for focus detection.

(+4) The interval between the images of J- must be detected.

Therefore, a correlation is found between the two light distributions on the image sensors (12) and (14). Both image sensors (]
2) The positions of the light-receiving elements constituting (14) are relatively shifted to determine the shift position (ie, the interval between the two images) that provides the best correlation. This detection principle is explained in detail in, for example, Japanese Patent Laid-Open No. 60-4914.

By the way, this correlation calculation requires a considerable amount of time because it is performed by relatively shifting the positions over a wide range. For this reason, there is a problem in that the responsiveness of the automatic focus adjustment device and the ability to follow the subject deteriorate.

Now, when I think about the tracking ability of the subject, ``2nd note'';
An automatic focus adjustment device detects the amount of defocus in a single distance measurement, such as when the subject is approaching or moving away from the camera, and focuses the photographic lens based on this amount of defocus. When moved to the position,
Since the subject is moving during this time, the subject is actually no longer in focus.

Figure 8 shows the situation. The horizontal axis is the time axis, and the vertical axis is the amount of defocus on the film surface. In Figure 8, the curve σ indicates the degree to which the amount of defocus increases at the film plane when the subject approaches at a constant speed, and the straight line m tracks the position where the photographic lens is about to focus its image. This is what happened. The “product” of the time axis is
It represents the integration time of COD, and "performance" represents the calculation time of the defocus amount. The subject approaches during the calculation time, so even if you drive the lens based on the calculation results,
When the lens stops, the subject is already moving.

As the subject approaches, the amount of defocus increases, and the camera quickly moves out of the depth of field and is out of focus.

Therefore, it is necessary to shorten the calculation time of the defocus amount as much as possible.

JP-A-51-126517 discloses that the detection zone of an image sensor is divided into three blocks, the entire area is shifted for each block, the best correlation position in each block is found, and the best correlation position for each block is calculated. A method has been proposed in which the value with the highest degree of correlation is adopted. However, in the end, this method ends up calculating over the entire correlation range for each focus detection, so that no effective time reduction can be achieved.

In addition, Japanese Patent Application Laid-open No. 56-75607 states that since the shift amount in the second and subsequent focus detections is not larger than the shift amount in the first focus detection, the maximum shift is set to 1.
A method has been proposed in which the adjustment is performed using the shift amount of the first shift, but if the shift 1ift is large, the calculation must be performed over a wide range, so the calculation takes time and the shift amount must be adjusted every time. control becomes complicated. Furthermore, it is not possible to cope with a case where focus detection becomes impossible, and there is a possibility that continuous automatic focus adjustment may not be possible.

An object of the present invention is to provide a focus detection device that can shorten the time required for correlation calculation in focus detection.

Means for Solving the Problems For this reason, the present invention provides a first area in which the subject light beams that have passed through each of the first and second areas of the photographic lens, which are symmetrical to each other with respect to the optical axis, are re-imaged. , storing in a memory means the focusing state in the previous focus adjustment obtained by relatively softening the positions of both photoelectric conversion element arrays from a signal representing the illuminance distribution from the second photoelectric conversion element array; When performing the focus detection calculation for the current focus adjustment by the calculation means in response to the output of
The main feature is that the shift range of the That is, in the present invention, the memory means stores the focus state in the previous focus adjustment, and limits the focus detection range in accordance with this memory means.

Aim Generally, when detecting the focus of an automatic focus adjustment device, once the best correlation position is found within a wide range, the lens is driven to the in-focus position according to the signal at this position.
Next time, if you scan only a predictable range instead of scanning a wide range as you did this time, you will be able to find the best correlation position for most subjects, which will save time. Furthermore, even when it is once determined that the object is in focus, it is sufficient to shift the area before and after the in-focus position in the next calculation instead of calculating the entire area.

Therefore, in the present invention, the focus state in the previous focus adjustment is stored in the memory means, and the shift range limiter limits the shift range in the next correlation calculation according to the output thereof, thereby shortening the calculation time.

Embodiments of the present invention will now be described with reference to the accompanying drawings.

FIG. 1 shows a circuit configuration of an automatic focus detection device for a camera according to the present invention.

FIG. 1 shows a circuit diagram of a focus detection device and an automatic focus adjustment device using the same when a line sensor (15) made of a COD as shown in FIG. 2 is used as a light receiving element.

(20) is a photoelectric conversion circuit including the above-mentioned line sensor (15) and a monitoring light receiving element, which includes soft pulse (SH), transfer lock (φ1), (φ, ), and clear pulse (ICG).
) is input, and outputs a time-series pixel signal (O8), a monitor output (AGCO8), and a reference voltage output (DO8). Here, the clear pulse (ICG) is the line sensor (
A pulse for setting each pixel in I5) to an initial state, whereby each pixel in the line sensor (15) discharges the accumulated charge and starts anew light integration, that is, charge accumulation. In addition, this pulse starts integration of the output of the monitoring light receiving element in the photoelectric conversion circuit (20), and the monitor output (AGCO8) changes over time to the reference voltage output (DO8) at a speed corresponding to the brightness of the object. ). The shift pulse (S H) is the line sensor (+
5) is a pulse that shifts the accumulated charge from the pixel section to the shift register section, and when this pulse is input, light integration in the pixel section ends. The transfer locks (φ,), (φ,) are pulses that are 180" out of phase with each other and are used to sequentially output the accumulated charges shifted to the shift register section from the shift register section in a time-series manner. The accumulated charges outputted by the photoelectric conversion circuit (20) are each converted into a negative voltage signal and output as a pixel signal (O8).

(22) is the reference voltage output (DO) from each pixel signal (O8).
8), the pixel signal (DO8) as a positive voltage signal is obtained.
°), (24) is the subtraction circuit (22)
Among the pixel signals (DO8') output from the pixel signal (DO8'), the pixel signals corresponding to the shaded several pixels (for example, the several pixels to the left of (Q,) in FIG. 2) are peak-bolded, and those pixel signals are The peak hold circuit that outputs the voltage (VP) corresponding to the maximum value, (26) is the subtraction circuit (22)
This is a variable gain amplifier that subtracts and amplifies the output voltage (Vl) of the peak bold circuit (24) from the pixel signal (DOS") from the pixel signal (DOS"). The dark current component contained in DO8') is removed. (28) is an A/D conversion circuit that converts the amplified pixel output (DO9'') from this amplifier circuit (26) into a digital value of a predetermined bit. , its output is taken into a microcomputer (hereinafter referred to as microcomputer 308). (32) is the gain control circuit and monitor output (AGC
Detecting the amount of change in O3) with respect to the reference output (DO8),
When the amount of change in the monitor output reaches a predetermined threshold within a predetermined time from the start of the change in monitor output (when it is bright), the microcontroller (3
0) and outputs a signal (TINT) indicating this, and also outputs a gain signal that sets the gain of the amplifier (26) to "1x". Furthermore, when a predetermined period of time has elapsed from the start of output of the monitor output (AGCO8), the forced shift signal (SHM) output from the microcomputer (30) is transmitted to the gain control circuit (32).
In this case, the gain control circuit (32) adjusts the gain of the amplifier (26) according to the amount of change in the monitor output (8GCO8) with respect to the reference voltage output (DO8) at the time of inputting the signal (SHM). “1x”, “2x”, “4x” or “
3. In this case, the smaller the amount of change, the larger the set gain.

(AN) and (OR) are an AND circuit and an OR circuit, respectively.
) is input, and the OR circuit (OR
) is the output signal of the AND circuit (AN) and the microcomputer (30
) is input. Here, the signal (SHEN) from the microcomputer (30) is a signal for permitting shift pulse generation by the shift pulse generation circuit (34), and is used during the period when generation of the shift pulse (SI-() should be prohibited (for example, During delta dump from photoelectric conversion circuit (20) to microcomputer (30) and microcomputer (30)
(during data calculation) becomes “Low”, but then becomes “H”.
high” and opens the AND circuit (AN). Therefore, when this signal (SHEN) is “high”, the signal (
TINT) occurs, the AND circuit (AN)
igh” signal (TINT). OR circuit (OR circuit)
) outputs this signal (TINT) or signal (SHM) to the shift pulse generation circuit (34), and in response, the shift pulse generation circuit (34) generates a shift pulse (SI-I).
will occur. (36) receives the clock pulse (CL) from the microcomputer (30) and transfers the lock (φ1), (φ
2), and upon receiving the signal (T I NT) or (Sr(M)) from the OR circuit (OR), it is reset to the initial state, and the previous transfer lock (φ1), Regardless of the phase of (φ,), the new (
φ, ), (φ2) are started to be generated (this is to synchronize the shift pulse (SH) and the transfer lock (φ, ), (φ2)). The signal (SH) output from the microcomputer (30) is a sample bold signal for specifying the pixel signal (DO8') to be captured by the peak hold circuit (24).

The microcomputer (30) is circuit-connected to a display circuit (38) and a lens drive device (40), and displays the focus adjustment state of the photographic lens (2) calculated by calculation as described later.
38), and also causes the lens drive device (40) to drive the photographic lens based on the display. In addition, the photographic lens (2) is calculated by the microcomputer (30).
In this example, the focus adjustment state of is expressed by the defocus amount and defocus direction, and therefore the lens driving device (
The driving amount and driving direction of the photographing lens (2) by 40) are determined. The lens driving device (40) drives the photographic lens (2) according to the driving amount and driving direction, and outputs a signal indicating the executed lens driving amount to the microcomputer (30), and the microcomputer (30) outputs a signal indicating the executed lens driving amount. 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 Fig. 1, Sl is an AF start signal switch (AF' switch), and when the AF' start signal switch S1 is closed, the focus detection operation is started, and when the AF start signal switch S1 is opened, the focus detection operation is started. will be stopped.

S2 is a release signal switch, and when the release signal switch S2 is closed, the camera itself moves to release operation and exposure control is performed, but the focus detection circuit temporarily uses the 1-noise signal switch to operate the mirror at the time of release. The stop operation occurs when S2 is closed.

Sof>C is a mode changeover switch for one-shot AF mode and continuous consistent ΔF mode, and the mode changeover switch 5oec is closed to set one-shot/soto AF mode, and opened to set continuous AF mode. Continuous AF mode has already been explained, but One-shot AF mode is effective when shooting a still subject in AF mode, which performs focus detection, once the focus state is detected, lens position adjustment is completed, and AF lock is performed. AF operation.

The switch Swd->n is a focus detection sensitivity range changeover switch, and when this switch is closed, the focus detection sensitivity range becomes the center spot-shaped sensitivity range B within the field of view frame 42 of the camera shown in FIG. When , the focus detection sensitivity range A is wide.

Next, before explaining the operation of the camera automatic focus detection device whose configuration is explained below, the correlation calculation and interpolation calculation used in this embodiment will be explained.

The correlation calculation used here is the line sensor (I5) in Figure 2.
photoelectric conversion element rows Q1 to Q 4 n + r l-r
411. L:1. ~(24Q+rl
The 8-bit data of ~r4B was first obtained from Japanese Patent Application Laid-open No. 1986-0-
As detailed in the 4914 publication, difference data DQn, . . . Dr.
, 1 (however, Dfljn=pH(21-1-t, Drn
=ry1 rl+4+ DL~D(2se, Dr+
~ Converted to DrtJ. Subsequently, the total contrast value is calculated. The contrast value C is as follows:
It is determined by the sum of the absolute values of the differences between adjacent differences in the reference portion (L).

(2) Finally, calculation is performed by shifting the correlation value YM/CCI) of the reference portion (I, ) and reference portion (R) by one pixel using the following equation.

wax However, I=1 to 9.

As a result, the higher the degree of correlation, the smaller this correlation value YM/=15-CCT) becomes. Then, the point where the degree of correlation is maximum is determined, and when the r value is 5, the object is in focus, and when ■ is smaller than 5, it is in the front focus state, and when it is larger than 5, it is in the back focus state.

The correlation value obtained in this way is obtained using a line sensor (15
), so interpolation calculations are performed to obtain fine precision, and the in-focus point is calculated.

Regarding this interpolation calculation, various proposals have been made in Japanese Patent Application Laid-Open No. 126'517, etc., but here we will discuss the 5th
Steps #100 to #■06 of the flowchart shown in the figure
This is done by

First, the minimum correlation value YM (aM) is detected.

Next, the value YM(2M) is normalized by the contrast value C, and the value YM(2M)/C is less than a predetermined value (YM(2M)
M)/C<0.1) and above the specified value (YM(2M)
/C≧02), a different method is used.

First, in the former case, the minimum value YM(2M)/C is judged to have high reliability, and when YM(ρM+1)≧YM(2M-1), YM(ρ
M+1)<yM(2M-1).

In this method, when considered in an ideal state, the correlation curves are 4
It is based on having an inclination of 5° and being orthogonal. When considering the ideal state, the standard F4 (L), the reference part (R) are N,
−”rn+ is output as exactly the same value as 4. Therefore, the difference data becomes Dρ□−Drl++.

On the other hand, the minimum correlation value is -1+l DQ+ Dr+ l / C1QA -1+lDρjHI Dr++ l /C, and I
Dρ+ Dr+ l, l D(13a Dr4
As long as the value of +l is sufficiently small with respect to the overall contrast C, these correlation curves have an inclination of 45° and are orthogonal to each other. This interpolation calculation method has conventionally been used in Japanese Patent Application Laid-Open No. 59-12651.
This is a more accurate interpolation method than the interpolation method proposed in Publication No. 7. However, if the value YM(4M)/c, which is obtained by normalizing the minimum correlation value YM(4M) with the contrast value, becomes larger than a predetermined value, the minimum correlation value may be affected by some kind of influence, in this case, due to a competing object near or far, or electrical noise. This becomes a large value, resulting in a value with poor reliability. Therefore, if this value YM(4M)/C is a predetermined value, M)/
Taking into consideration that the interpolation value at the Srenyu Bold level will vary, a hysteresis is provided, and once the interpolation method becomes the curver's interpolation method, the former interpolation method is used until this value YM(4M)/C becomes 02 or more. Use.

Next, please refer to the flowcharts in FIGS. 4(a) and 4(b) for an example in which the line sensor (15) is divided into blocks as shown in FIG. 2 and the following table. I will explain while doing so.

[Margins below] =21- Note that the line sensor (15) has a reference part (L) consisting of pixel colors ~1240 and a reference part (R) consisting of pixels r and ~r48, with an intermediate separation strip in between. It is divided into

The reference portion (L) includes pixels g1 to Q. 1st block (1) up to, pixel color, 2nd block (II) up to Qso
, the third block (III
) and are divided into blocks that overlap each other.

When the two images respectively formed on the reference part (R) and the standard part (L) are in focus, the distance between them is a predetermined distance.

Now, in FIGS. 4(a) and 4(b), after starting the operation, the microcomputer (30) first specifies the start block (zone) of the focus detection calculation in #20 as the second block, and In addition to resetting the shift amount limit flag ZF for defocus amount calculation, the lens driven flag S
Set F on your hair. This lens driven flag SF is a flag indicating whether or not the subject exists near the in-focus position.
Since the position of the subject has not been detected at the start of the focus detection calculation, it is set arbitrarily as described above. Then AF
Wait for the human power of the operation start signal (#1). AF switch S
1 closes and the start of AF operation is instructed, first the line sensor (15) is initialized, and then the line sensor (15)
image information storage is started (#2). Line sensor (I5
) is completed to a predetermined level, the accumulated charges are transferred in parallel to the analog shift register by a shift pulse, and thereafter the transfer locks (φ, ), (φ2)
Charge transfer and data dump (#3) are performed in synchronization with . When the data dump of all pixels required for the focus detection calculation is completed, the micro combi coater (30) first converts the pixel data into difference data (#4). This is to remove spatial frequency components that are not necessary for focus detection calculations and are an obstacle.

After calculating the difference data, the microcomputer (
30) performs sensing of the focus detection sensitivity range changeover switch 5w8n in order to determine whether or not a limit is imposed on the focus detection sensitivity range. Focus detection sensitivity range selection switch 5w4
-> When n is in the OFF state, in #21, the entire focus detection sensitivity range, that is, the first to third blocks (
1) When the zone calculation counter j is set to 3 in order to perform focus detection calculations with (n) and (In), and conversely, the focus detection sensitivity range changeover switch S+h 4-5nh is in the ON state. At #22, the zone calculation counter j is set to 1 in order to perform the focus detection calculation for the focus detection sensitivity range of only the second block (II), and the zone designation is set to 1 in the second block (II).
Set n=2 to make block (II).

Next, the microcomputer (30) determines in #61 whether the lens driven flag SF is SF-. Since it is SF-arrow before the start of the focus detection calculation, the micro combi coater (30) starts the focus detection calculation. In this case, since zone designation n-2 and defocus amount limit flag ZF = 0, after #23 to #27,
First, in #29, correlation function calculations are performed for the entire software range of the second block (II), and as shown in FIG.
), the image interval with the minimum correlation function YM2/C2(k), that is, the image interval with the highest correlation &
M2 is required. This QM2. YM2/C2 (f2M
2) and the correlation values before and after it, interpolation calculation is performed in #31, and the image interval XM2. Find YM2/C2 (XM2).

Next, LO-CON determination is performed on this value in #32, and if the obtained XM2 is reliable, the image shift 1lF2 is calculated from the image interval in #33 and stored in memory. Furthermore, in order to speed up the correlation calculations for subsequent blocks, only image deviations greater than this image deviation amount are calculated. Therefore, in #34, the defocus limit flag ZF is set to 1, and Q and M2-15 are stored as the limit value P min. This is a value that is 1 smaller than the line sensor pitch image interval that gives the maximum correlation,
This is because interpolation calculations require correlation values of pitch deviations on both sides. Regarding this LO-CON determination, please refer to the patent application filed in 1986-
No. 7687, supra.

After this, check the routine counter. At this stage, if the focus detection sensitivity range changeover switch Sw→n is set to ON and the focus detection sensitivity range is set only for the second block (II), j is set to 1 in advance. Therefore, the counter j becomes φ after passing the j-j-+ step of #35, and at the point when the focus detection calculation of the second block (n) is completed, the process proceeds to the lens drive routine from #36 to #38.

On the other hand, when a wide focus detection sensitivity range is selected and the focus detection sensitivity range changeover switch Sw→n is in the OFF state, j is preset to 3, and at the end of this routine j-j-1
-2≠0, n-n +1=2+], select the third block (In) as the next focus detection zone, and return to the correlation function calculation for the third block (TII) (#25.
#41 to #44).

In the correlation calculation of the third block (III), if the second block (If) determines that it is not LO-CON, the image detected in the second block (II) after confirming the set ZF flag is Correlation calculation is performed only with an image shift amount that is larger than the deviation amount. In the second block (n) L O-
If it is determined to be CON, the third block (I[
In step 1), correlation calculation is performed under the total image shift amount.

In this way, similar to what was done in the second block (n), the process shown in FIG.
As shown in b), calculation of QM3 (#45), XM3. Calculation of YM3/C3 (XM3) (#46
), performs LO-CON determination (#47), and LO-CO
If not N, store ill image shift ftP3 in memory (#48)
Then, the defocus limit P m1n-0M3-25 is memorized and the flag ZF=1 is set (#49). It is conceivable that P3 obtained here may be smaller than I)2 by a difference of less than one pitch, but in that case, both P min will be the same value, and it is impossible for P min to decrease.

Next, in #50 to #59, n=n+
I=4 is added, and the correlation calculation of the first block (1) is performed.

When a wide focus detection sensitivity range is selected in this way, the first
~ In the third block (1), (1), and (III), after the focus detection calculation is performed in an image shift range larger than the image shift 1-@ of the block previously determined by the correlation calculation, the zone counter becomes 0. Then, the process moves to #38, the lens drive routine.

Here, turn on the focus detection sensitivity range changeover switch Sw←n again.
, the routine is the same regardless of whether it is OFF or not.

First, it is determined whether there is a zone that is not LO-CON (#39). Here, if the focus detection sensitivity range changeover switch Sw←n is ON and the narrow focus detection sensitivity range of only the second block (n) is selected, only the second block (IT) will be subject to discrimination. Needless to say. #
39, the first to third Brozok (1), (n), (III
) is determined to be LO-CON, #10, #
Return to #l from #11 and #76 and take the photographic lens (2)
moves through the lowest eye area from the closest state to ■, moves to LO-CON 5CAN, which performs focus detection calculations, and drives the lens. During this operation, several focus detection calculations are performed, all of which result in I, O-CON, and LO-CON 5CA.
When N ends, the lens operation is stopped at the nearest lens end point (3), and as long as the AF switch Sl remains ON, the image sensor is driven and focus detection calculations are performed. LO-CON is displayed (#12), and the camera waits for the subject to be in a state suitable for focus detection.

When a zone other than L O-CON is detected, the image shift amount of the zone with the largest image interval, that is, the zone including the closest object among the objects, and the zone are extracted (#40). The image shift amount Pi is converted by multiplying defocus 2 by a constant (#I3), and is stored as n-zone number i. The obtained defocus amount is converted to a lens drive amount (#14) by multiplying the defocus amount that differs for each photographic lens (2) by the lens drive amount coefficient (#14), and when the lens drive amount is extremely small, In other cases, the lens is driven (816).

Next, the lens driven flag SF, which was cleared in #20 at the start of the AF operation, is set to 1 in #72. This lens driven flag SF indicates that there is a high probability that the subject exists near the in-focus position. After this, the focus detection device reintegrates the image sensor, obtains new image information, and repeats the focus detection calculation. Here, when 5F=1, there is a high probability that the subject exists near the in-focus position, so the image interval with the highest correlation can be predicted in advance. Therefore, correlation values are determined only for the five image intervals of -2, -1, 0, 1, and 2 from the focused image interval (#62). As a result, if the image interval that yields the highest correlation is -1, 0, or 1, interpolation calculations are performed according to that value, and the LO-CO
N determination is performed (#63, #64, #65), and when the value is determined to be highly reliable, lens driving is repeated according to the interpolated image interval XMn. That is, this interpolated image interval XM
After the image interval deviation amount Pn is calculated in step #66 of FIG. 4(a) from n, the image distance deviation amount Pn is converted into a defocus amount in step #13 of FIG. 4(b). On the other hand, if LO-CON is determined in #65, the same correlation calculation as the first time is performed, including when the maximum correlation image interval is 2 or -2. Also, in the focus detection calculation, the final L
When O-CON is determined, the lens driven flag SF is cleared in #76, and this routine is not repeated thereafter, and the focus detection calculation is performed in the same way as the first focus detection operation until focus is detected again. Repeat focus detection calculations for all defocus amount ranges and all blocks. In addition, when focus is detected, in the case of one-shot AF, the lens driven flag SF is set to #.
It is set at 74.

Here, we have shown an example in which refocus detection is performed after the lens drive is completed, but it is also possible to repeat focus detection while the lens is being driven, and in such an example, the lens drive completion flag Sl'i' is It can also be set only when focus is detected. In addition, here, the correlation value calculated image shift amount at the time of simple focus detection is set to 2.1, 0. I gave it 5 points of -1 and -2, but this is an A.
This value depends on the adjustment accuracy between the F-sensor and the re-imaging lens, etc., and if sufficient accuracy is ensured, it should be 1.0. -] 3 points or 1.0. -1. -2 or 2,1,0. It goes without saying that even 4 points of -1 is possible.

Finally, in FIGS. 4(a) and 4(b), the ON/OFF determination part of the focus detection sensitivity range changeover switch Sw←n is changed to the ON/OFF determination part of the mode changeover switch 500C. Continuous AF, One-shot AF
It is also possible to switch the focus detection sensitivity range between wide and narrow according to the present invention. Since the shift range in the correlation calculation is limited in response to the shift range, if focus detection is possible within the limited shift range, the time for the focus detection calculation can be shortened, and the AI? The operation cycle is shortened, and the ability to follow a moving subject is improved.

[Brief explanation of drawings]

Figure 1 is a block diagram of the automatic focus adjustment circuit, Figure 2 is an explanatory diagram showing the pixel arrangement of the image sensor, Figure 3 is an explanatory diagram of switching the focus detection sensitivity range within the camera's field of view, and Figure 4. 4(a) and 4(b) are flowcharts of the operation of the automatic focus adjustment circuit of FIG. 1, FIG. 5 is a flowchart 1 showing an example of interpolation calculation, and FIG. 6 is an explanation of the focus detection optical system. 7 is an explanatory diagram that does not show the positions of two images in focus detection, and FIG. 8 is an explanatory diagram for explaining problems with a conventional automatic focus detection device. 1... Subject luminous flux, 2... Shooting lens, 9
．． 11. Two images, 12.14... photoelectric conversion element array. ]5... line sensor, 20a/photoelectric conversion circuit, 30
...Micro combination coater, S, ...AF switch, So←C...mode changeover switch, Sw←n...focus detection sensitivity range changeover switch. SF: Lens driven flag. Patent applicant: Minolta Camera Co., Ltd. Agent: Patent attorney: Aobai Ao and 2 others Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] (1) The subject light beams that have passed through the first and second areas of the photographic lens, which are symmetrical to each other with respect to the optical axis, are re-imaged and the two images are converted into first and second photoelectric converters. A continuous lens is formed on an element array and detects the focusing state of a photographing lens by determining the mutual positional relationship of images from signals indicating illuminance distribution from the first and second photoelectric conversion element arrays. In an automatic focus detection device for a camera having an AF mode, a shift is performed in which the best correlation is obtained by relatively shifting the positions of both photoelectric conversion element arrays from signals representing the illuminance distribution from the first and second photoelectric conversion element arrays. a calculation means for determining the position; a memory means for storing the focus state in the previous focus adjustment in the continuous AF mode; and a memory means for storing the focus state in the previous focus adjustment in the continuous AF mode; An automatic focus detection device for a camera, comprising: shift range limiting means for limiting the shift range of the camera.