JPS62205307A - Automatic focus detecting device for camera - Google Patents

Abstract

PURPOSE:To shorten an arithmetic time and to improve tracking performance for an object by performing focusing arithmetic operation based upon the shift quantity limited almost in a focusing state by a block which obtains a signal indicating the nearest focus state selected by last focusing detection arithmetic operation. CONSTITUTION:A microcomputer 30 stores the block whose gap between images is largest by the last focusing arithmetic operation and performs focusing detection arithmetic operation by the zone arithmetic routine of the 1st time for the block at the time of refocusing arithmetic operation. Then the 1st focusing detection correlative arithmetic is performed by a flow branched by set (n) and the focusing detection arithmetic operation after temporary focusing detecting operation is speeded up. Further, when the block whose gap between images is largest is selected preferentially in block fractionization focusing detection arithmetic operation, the number of times of correlation arithmetic for the focusing detection of following blocks is decreased to improve the response of focusing adjustment.

Description

[Detailed description of the invention] Robbery! BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focus detection device for a camera that detects the focus state of a photographic lens by receiving object light that has passed through the photographic lens of the camera.

Conventional technologyThe first lens of the photographic lens is symmetrical to the optical axis.
The subject light flux that has passed through each of the and second areas is
Create two images by re-imaging each image, find the phase U positional relationship of these two images, and calculate the amount of deviation of the imaging position from the expected focal position and its direction (the imaging position is from the expected focal position). A focus detection device has already been proposed that obtains front or rear focus (front focus or rear focus). The optical system of such a focus detection device has a configuration as shown in FIG.
Alternatively, there is a condenser lens (6) further behind this, and a re-imaging lens (8) further behind that.
, (10), each reimaging lens (8).

Image sensors (+ 2) and (] 4) such as COD, for example, are arranged on the imaging plane (10). As shown in FIG. 9, the images on each image sensor (12), (+4) are the images (9), (I1) of the object to be focused on.
In the case of so-called front focus, in which the images are formed in front of the intended focal plane, they are close to the optical axis (1) and close to each other, and on the other hand, in the case of rear focus, they are respectively far from the optical axis (1).

When the image is in focus, the distance between the two corresponding points of the two images (9) and (l 1) is a specific distance determined 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.

The distance between these two corresponding points is the image sensor (12
) and (14), and by relatively shifting the positions of the light receiving elements constituting both image sensors (12) and (14), the shift position where the best correlation is obtained (i.e., It is detected by determining the distance between two images. Regarding this detection principle, for example,
It is explained in detail in Publication No. 4.914 and the like.

In an automatic focus adjustment device for a camera with a built-in focus detection optical system of this kind, there is integration of subject light weight by CC and D image sensors, focus state detection calculation (defocus amount calculation) using COD image sensor output, A sequence of lens drive according to the amount of defocus, first stop at the current focal position (when the shutter release button is pressed) is program-controlled by a control circuit consisting of a microphone computer.

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.

Invention is not going to solve the problem When performing focus detection, an image sensor (12).

(14) The spacing of the images above must be detected.

Therefore, the image sensor (+ 2), 2 on (14)
Find the correlation for the two light distributions. Both image sensors (
12) The positions of the light receiving elements constituting (14) are relatively shifted to find the shift position (ie, the interval between the two images) that provides the best correlation.

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 and subject tracking performance of the automatic focus adjustment device deteriorate.

Now, when thinking about subject tracking, the automatic focus adjustment device described above detects the amount of defocus in a single distance measurement, such as when the subject approaches or moves away from the camera. When the photographing lens is moved to the in-focus position due to the amount of defocus, the subject is actually moving and is no longer in focus.

The situation is shown in Figure 1O. The horizontal axis is the time axis, and the vertical axis
The second is the amount of defocus on the film surface. In Fig. 10, the curve Q indicates the degree to which the amount of defocus increases on the film plane when the subject approaches at a constant speed, and the straight line m indicates the degree to which the photographic lens tracks the position on which the photographic lens is trying to focus its image. It is something that "Product" of time axis
represents the integration time of the COD, and "E" represents the calculation time of the defocus amount. The subject approaches during the computation time, so even if the lens is driven based on the computation result, the subject may have already moved by the time the lens stops.

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-59-126517 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.

Furthermore, 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 amount is set to 1.
A method has been proposed in which the shift amount is adjusted using the first shift amount, but when the shift amount 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. Since it is necessary to change +'J to -, 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.

It is an object of the first and second inventions of the present application to provide a focus detection device for a camera that reduces the time required for focus detection calculations.

Means for Solving the Problems Therefore, the first invention of the present application is such that the object light beams that have passed through the first and second regions of the photographic lens, which are symmetrical to each other with respect to the optical axis, are re-respected. Among the eleventh and second photoelectric conversion element arrays that form an image, the first photoelectric conversion element array is divided into a plurality of blocks each having a predetermined number of pixels, and the light distribution signal of each block and the second photoelectric conversion element are divided into blocks each having a predetermined number of pixels. Shifts the light distribution signal from the array relatively to find the shift position where the best correlation is obtained. Among the signals indicating the focus adjustment state of each block from the calculation means, the object is closest to the photographing lens. The determined signal indicating the rearmost focus state is selected as the signal indicating the focus adjustment state of the photographing lens, the block that obtained the signal indicating the rearmost focus state selected in the previous focus detection calculation is memorized, and the current block is The focus detection calculation is characterized in that the calculation area limiting means causes the calculation means to perform the focus detection calculation in the blocks stored in the memory with a limited shift amount in the vicinity of the focus.

In the first invention of the present application, the object is determined to be closest to the photographing lens among the signals indicating the focus adjustment state of each block of the first photoelectric conversion element array consisting of a predetermined number of pixels. A signal indicating the state is selected as a signal indicating the focus adjustment state of the photographing lens. The block selected in the previous focus detection calculation where the signal indicating the most rear focus state can be obtained is memorized, and in the current focus detection calculation, this memorized block is used with a limited shift amount near the focus. A focus detection calculation is performed.

Further, the second invention of the present application provides first and second regions in which the subject light beams that have passed through the first and second regions of the photographing lens, which are in a symmetrical relationship with respect to the optical axis, are re-imaged, respectively. Among the photoelectric conversion element arrays, the first photoelectric conversion element array is divided into a plurality of blocks each having a predetermined number of pixels, and the light distribution signal of each block and the light distribution signal from the second photoelectric conversion element array are divided into blocks. of the signals indicating the focus adjustment state of each block from the calculation means to determine the shift position where the best correlation can be obtained by relatively shifting . The signal is selected as a signal indicating the focus adjustment state of the photographing lens, the block in which the signal indicating the rearmost focus state selected in the previous focus detection operation was obtained is stored in memory, and the calculation area limiting means selects the current signal in this block. It is characterized in that the reliability of the data obtained by the focus detection calculation is determined, and if this data is determined to be reliable, the range of the focus detection calculation in other blocks is limited. Second part of the application
In the invention, the reliability of data obtained by a focus detection calculation only in the vicinity of the current focus position in a block from which a signal indicating the rearmost focus state selected in the previous focus detection operation was obtained is determined.

If this data is determined to be reliable, focus detection calculations for other blocks are omitted.

41 Generally, in a camera's automatic focus detection device, once
When the best correlation position is found within a wide range (), the photographing lens is driven to the in-focus position according to the signal at this position, so there is no need to scan a wide range next time as before. By scanning only the range that can be predicted, the best correlation position can be found for most subjects, which saves time.

Furthermore, even when it is once determined that the object is in focus, it is sufficient to perform the next calculation by shifting the vicinity of the in-focus position instead of the entire area.

Therefore, in the first invention of the present application, the current focus calculation is performed with a limited shift amount near the focus in the block where the signal indicating the rearmost focus state selected in the previous focus detection calculation is obtained. conduct. This limits the shift range in the correlation calculation and shortens the calculation time.

Further, in the second invention of the present application, the reliability of the data obtained in the first invention of the present application is determined.

If this data is determined to be reliable, other blocks = 11
− Omit focus detection calculations in locking. This results in
Computation time is reduced.

Jinbana carp Hereinafter, the present invention will be described in detail 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 the above-mentioned line sensor (15),
A shift pulse (SH), transfer lock (φI), (φ2), and clear pulse (I CG) are input to the photoelectric conversion circuit including the monitor light receiving element, and the time-series pixel signal (O8) and monitor Output (AGCO8), reference voltage output (
DO8) is output.

Here, the clear pulse (rcc) is the line sensor (15)
A pulse to set each pixel in the initial state,
As a result, 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 (DO9) at a speed corresponding to 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 the shift register section, and when this pulse is input, light integration in the pixel section ends. The transfer locks (φl) and (φ, ) are 180 degrees out of phase with each other in order to sequentially output the accumulated charges shifted to the shift register section from the shift register section in time series.
These are shifted pulses, and the accumulated charges outputted thereby are converted into negative voltage signals within the photoelectric conversion circuit (20) and outputted as pixel signals (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) that outputs
Among the pixel signals (DO3') output from the pixel signal (DO3'), the pixel signals corresponding to the shaded several pixels (for example, the several pixels to the left of (νI) in FIG. 2) are peak-held, and the maximum of those pixel signals is The peak hold circuit (26) outputs the voltage (V'P) corresponding to the value, and the subtraction circuit (26)
This is a variable gain amplifier that subtracts and amplifies the output voltage (VP) of the peak bold circuit (24) from the pixel signal (DO9') from 2). The dark current component contained in DO8') is removed. (28) is an A/D conversion circuit that converts the amplified pixel output (DO3'') from this amplifier circuit (26) into a digital value of predetermined bits, and the output is sent to a microcombicoater (308 hereinafter referred to as a microcomputer). ).(32) is a gain control circuit that detects the amount of change in the monitor output (800O8) 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 (AGCO6), the forced shift) signal (STIM) output from the microcomputer (30) is switched to the gain control circuit (3).
2), but in this case, the gain control circuit (32) outputs the monitor output (AGCO8) at the time of inputting the signal (SHM).
The gain of the amplifier (26) is set to "1x", "2x", or "4x" depending on the amount of change with respect to the reference voltage output (DO9).
Or output a gain signal set to "8x". 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, and the AND circuit (AN) includes a double signal (TINT) from the gain control circuit (32) and a signal (sr -+EN) is input, and the OR circuit (OR
) is the output signal of the AND circuit (AN) and the microcomputer (30
) from -'' double signal (SHM) 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 a signal for allowing shift pulse generation by the shift pulse generation circuit (34). (20) to the microcontroller (3
0) and during data calculation in the microcomputer (30)), it becomes “[, Ow”, but after that it becomes “High”.
” and opens the AND circuit (AN). Therefore, when this signal (SHEN) is “high”, the signal (T r
NT) occurs, the AND circuit (AN) becomes “High
h” signal (T r NT) is output. OR circuit (OR
) outputs this signal (TINT) or signal (SHM) to a shift pulse generation circuit (34), and in response, the shift pulse generation circuit (34) generates a shift pulse (SH). (36) receives the clock pulse (CL) from the microcomputer (30) and transfers the lock (φ1), (φ,
) is a transfer lock generation circuit that generates an OR circuit (
When the signal (TINT) or (SHM) is received from 01"(), it is reset to the initial state, and regardless of the phase of the previous transfer lock (φI) and (φ2), the new (φ1
), (φ2) starts to be generated (this is a shift pulse (
This is to synchronize the transfer locks (φ1) and (φ,) with the transfer locks (φ1) and (φ,). ). 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 AP start signal switch (AP switch), and when the AP start signal switch Sl is closed, the focus detection operation is started, and when the AP start signal switch S1 is opened, the focus detection operation is stopped. be done.

S2 is a release signal switch, and when the release signal switch S2 is closed, the camera itself starts the release operation and exposure control is performed, but the focus detection circuit temporarily closes the release signal switch S2 to operate the mirror at the time of release. It becomes a stop operation.

So<-”>c is the mode selection switch for one-shot AF mode and continuous AP mode, and the mode selection switch 5or-)c is closed for one-shot AF mode,
Open to set Continuous AF mode. Continuous AP mode has already been explained, but One-shot AF mode is effective when shooting a still subject in AP mode, which performs AP lock after the lens position adjustment is completed once the focus state is detected during focus detection operation. This is AP operation.

The switch Sw<→n is a focus detection sensitivity range changeover switch of the present invention, and when this switch is closed, the focus detection sensitivity range is set to the third focus detection sensitivity range.
This becomes a central spot-like sensitivity area B within the field of view frame 42 of the camera shown in the figure, and when it is open, it becomes a wide focus detection sensitivity area A.

Next, before explaining the operation of the automatic focus detection device of the camera shown in FIG. 1, the correlation calculation used in the first and second inventions of the present application will be explained with reference to FIGS. and interpolation calculations will be explained.

The correlation calculation used here is based on this photoelectric conversion element array ρ.

It is calculated using ~ρtoul-rye. ρ1～ρ4
0. The 8-bit data r1 to r48 was first
Difference data Dρn is used to limit the spatial frequency to be detected as detailed in Japanese Patent No. 0-4914.

Drn((Date, D evening, =Qn121+t, Drn=
rl rn-)4D12. ~Di238. Drl-D
r44). Subsequently, the total contrast value is calculated. The contrast value C is determined by the sum of the absolute values of the differences between adjacent difference data of the reference portion (I,) as follows.

11I+ Finally, calculation is performed by shifting the correlation value YM/C(T) of the reference portion (L) and reference portion (R) by one pixel using the following formula.

However, I=1 to 9.

As a result, the higher the degree of correlation, the higher the correlation value YM/C (1)
becomes smaller. Then, the point where the degree of correlation is maximum is determined, and when the I value is 5, the object is in focus, and when ■ is smaller than 5, the front focus state is obtained, and when it is larger than 5, the rear focus state is obtained.

The correlation value obtained in this way is obtained using a line sensor (15
), the in-focus point is calculated by performing interpolation calculations to obtain it with fine precision.

Various proposals have been made regarding this interpolation calculation in Japanese Patent Application Laid-Open No. 59-126517, etc., but here it is performed using steps #100 to #106 of the flowchart shown in FIG.

First, the minimum correlation value YM (i2M) is detected.

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

First, in Moe's case, the minimum value YM(12M)/C is judged to be highly reliable, and when YM(12M+1)≧YM(4M-1), YM(
12M+1)<YM(cM-1).

In this method, when considered in an ideal state, the correlation curves are 45
It is based on the fact that they are orthogonal with an inclination of °. When this is considered in an ideal state, the reference part (I,) and the reference part (R) are outputted with exactly the same value as (!n=rn+).Therefore, the difference data becomes DI2n-Drn+4.

9ζ It is.

On the other hand, the minimum correlation value is 2G −1+ l DI2+ Dr41 / C'1rX = I + l D(lse Dr4+ l / C
Then, l Do, 1Dr, l, l D(be
As long as the value of Dr4+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 was previously used in Japanese Unexamined Patent Publication No. 59-1
This interpolation method is more accurate than the interpolation method proposed in Publication No. 26517. However, the minimum correlation value YM(ρ
YM (12M), which is the value obtained by normalizing M) with the contrast value C.
When /C becomes larger than a predetermined value, the minimum correlation value becomes a large value due to some influence, in this case a competing object near and far, or electrical noise, resulting in a value with poor reliability. Therefore, when this value YM(ρM)/C is greater than or equal to a predetermined value, an interpolated value is determined not based on the minimum value but using correlation values on both sides thereof. Also, this value YM ((2M
)/C considers that the interpolation value at the threshold level will vary, so hysteresis is provided, and once Moe's interpolation method is used, this value YM((!M)/C becomes 0.2 or more. The former interpolation method is used.

Next, the basic operations of the first and second inventions of the present application will be explained with reference to the flowchart shown in FIG.

When a power switch (not shown) is turned on, the flow shown in FIG. 3 starts, the microcomputer (30) executes step #1, and waits for the AP operation switch S to be turned on. The AP switch s1 is normally turned on by pressing the first stage of the release switch, and starts the AF operation.

The microcomputer (30) has a photoelectric conversion circuit (2
0), in step #2, the photoelectric conversion circuit (20) starts integrating image brightness information. After the integrated charge reaches a predetermined level, in step #3 (hereinafter, "step" is omitted), the microcomputer (
30) stores the A/D converted value of each pixel output in a RAM (not shown) in the microcomputer (30) in synchronization with the transfer lock after the shift pulse is generated. Each required pixel data ρ1 to ρ1. 8 of rl~r411
After manually inputting the bit digital data, the microcomputer (30) outputs the above-mentioned difference data DL to D123 in #4.
e, Dr+ to Dr44 are created.

After completing the preparations for the correlation calculation in this way, the microcomputer (30) checks the focus detection sensitivity range changeover switch Sw→n at #5--. If the focus detection sensitivity range changeover switch Sw (→n is ON and the photographer requests a narrow focus detection sensitivity range, the microcomputer (30) performs the correlation calculation in #5-2. The number of data in the narrow focus detection sensitivity range 16 and the start difference data 11 are set in the data number and start difference data number S, and the predetermined value C8I is set in the focus lower limit contrast value cs.Conversely, in focus detection Sensitivity range selection switch S
W (-> If n is OFF and a wide focus detection sensitivity range is requested by the photographer, the microcomputer (30) calculates the total sensitivity range as the number of correlation calculation data in #5-1. Set the number of difference data to 36, set I as the start difference data number, and set a predetermined value CS v to the focus detection lower limit contrast value C8.Next, #5-
At step 3, the microcomputer (30) selects values from 1 to 9 according to the S and D values set by ON and OFF'F of the focus detection sensitivity range changeover switch Sw←)n.
The correlation value for each value of k is calculated. This is where the focus detection sensitivity range is limited.

The minimum value of the correlation values thus obtained is detected in #6, and the above-mentioned interpolation calculation is performed in #7 to calculate the image interval XM.

The difference between this image interval XM and the reference focused image interval XJ is calculated as the image interval deviation amount P in #8. This image interval deviation f
iP is a value proportional to the amount of defocus.

Next, the reliability of this value is checked in #9. This is described in detail in Japanese Patent Application No. 7687/1987. That is, ``the contrast value C must be greater than or equal to a predetermined value (in this case, it must be greater than the already set C8 value), and ``the maximum value of each pixel output must be greater than the predetermined value Ps''.
(2) The minimum value of the correlation value is not at both ends; (2) Furthermore, the YM/C value obtained by interpolation calculation using the same interpolation calculation as the image interval X'M value is less than or equal to the predetermined value YMs; When all four points are satisfied, the image interval deviation amount P calculated by calculation is converted into a defocus amount in #13 as highly reliable data. Further, in #14, the defocus amount is converted into a lens drive amount. Thereafter, it is determined in #I5 whether the lens is in focus or if lens driving is required based on the amount of lens drive, and in the former case, in-focus display is performed in #17.

In the latter case, the lens is driven in step #16, and the photoelectric conversion circuit (20) reintegrates again, and the focus confirmation operation is performed by refocusing detection. Also, after the display is displayed in black, the microcomputer (30) switches the mode selector switch S at #18.
It is determined whether o<-)c is ON or OFF, and when the mote changeover switch So<-yc is ONt (one shot 1-ΔF), the AF operation is finished with the lens stopped. If the mode selector switch So'-)c is in the oFp state and the continuous AF' mode is not selected, the photoelectric conversion circuit (2o) is activated to repeat this routine.
Reintegrate.

On the other hand, if it is determined in #9 that the contrast value, pixel output maximum value, or correlation value is unreliable, the lens is driven in #11, and all lenses are driven. Low-contrast scanning L O-CON5CAN is performed to pass through the range at least once, and if it is determined that reliable data cannot be obtained even after completing this at #■0, the lens drive is finished and the scan is performed at #12. , LO-CON indicates that focus detection is impossible due to low contrast.
Perform display.

In the flow shown in Figure 5, the micro combicoater (30) checks whether the focus detection sensitivity range is wide or narrow in the flow #5-~, but whether it is in continuum AP mode or not.
One-shot AF mode sensing may also be performed. If the motor selector switch So (→C is OFF),
If the continuous AF mode is selected in the F state, go to the flow #5-] and set the focus detection sensitivity range widely, and set the mote selector switch So/→C to the 011 state and switch to the one-shot AP mode. If is selected, proceed to flow #5-2 and set a narrow focus detection sensitivity range. Here, it is assumed that the focus detection sensitivity range changeover switch 5w1->n shown in FIG. 1 is deleted.

In this way, in continuous AP mode,
Is it easy to track moving subjects due to the wide focus detection sensitivity range?
In contrast, when using one-shot AP, the subject can be easily captured within the limited focus detection sensitivity range, and highly accurate AF can be achieved for stationary subjects.

Next, we will discuss the operation of the embodiments of the first and second inventions of the present application when the line sensor (15) is divided into blocks as shown in FIG. 2 and the following table.
Figure 6, Figure 7 (a) and Figure 7 (b) (1) 7
This will be explained with reference to , -ja-1.

[Margins below] Note that the in-sensor (15) indicated by - is divided into a reference part (I,) consisting of pixels C to FF40 and a reference part (R) consisting of pixels r1 to r48, with an intermediate separation strip in between. It is divided into The reference portion (I,) includes pixels ρ1 to ρ,. The first block (I) of pixels (!II to Q30), the third block (IT) of pixels ρ, 1 to ρ4o
The blocks are overlapped with each other and divided into blocks as shown in II). When the two images respectively formed on the reference part (R) and the reference part (I7) are in focus, the distance between them is a predetermined distance ML.

In FIG. 6, after starting the operation, the microcomputer (30) first specifies the start block (zone) of the focus detection calculation in #20 as the second block (n), and limits the shift amount of the defocus amount calculation. Reset flag ZF.

Thereafter, it waits for the input of an AF operation start signal (#1). ΔF
When the switch S1 is closed and the start of AF operation is instructed, the line sensor (15) is first initialized, and then image information storage of the line sensor (15) is started (#2). When the charge accumulation in the line sensor (15) is completed to a predetermined level, the accumulated charges are transferred in parallel to the analog shift register by shift pulses, and thereafter the transfer locks φ, φ
, 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 microcomputer (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) is a focus detection sensitivity range changeover switch Sw (→n
perform the sen song. Focus detection sensitivity range selection switch Sw
(→When n is in the OFF state, in #21, the entire focus detection sensitivity range, that is, the first to third blocks (
1), ('TI), (ITI) to perform focus detection calculation, zone calculation counter j is set to 3, and conversely, focus detection sensitivity range changeover switch 5w1->n is in ON state. At #22, the zone calculation counter j is set to 1 in order to perform focus detection calculation for the focus detection sensitivity range of only the second block (TI), and the zone designation is set to 1 in the second block (TI).
Set n=2 to make it a block (U).

Focus detection calculation is started in this state, but zone designation n=
2. Since the defocus amount limit flag ZF=0, after steps #23 to #27, each correlation function calculation is performed for the entire shift range of the second block (U) in #29, and then #3 Correlation function vM2/c2 within it at °
The minimum image interval of (k), that is, the image interval ρM2 with the highest correlation is determined. This f! M2. YM2/C
2 (ρM2) and the correlation values before and after it, interpolation calculation is performed in #3■, and the image interval XM2. YM2/C2 (XM2)
seek.

Next, perform LO-CON judgment on this value in #32, and if the obtained XM2 is reliable, calculate the image shift weight P2 from the image interval in #33 and store it 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 the limit value P min is set to ρM.
2-15 is stored in memory. This is because the value is 1 smaller than the line sensor bit image interval at which the degree of correlation is maximum, and the correlation value of the pitch deviation on both sides is required for the interpolation calculation. This interpolation calculation and LO-CON determination are similar to the explanation of the flowchart in FIG. 5.

After this, check the Luzin counter. If the focus detection sensitivity range changeover switch Sw(-)n is set to ON at this stage and the focus detection sensitivity range is set only for the second block (It), set j = 1 in advance. Therefore, the counter j becomes φ after passing the step j=j-1 in #35, and at that point when the focus detection calculation of the second block (TI) is completed, the lens drive routine from #36 to #38 is started. Head towards.

On the other hand, when a wide focus detection sensitivity range is selected and the focus detection sensitivity range switch SW'→n is in the OFF state, j=3 is preset, and at the end of this routine, j=j-
1 = 21O, n-n + I = 2 + I, select the third block (Ill) as the next focus detection zone, and return to the correlation function calculation for the third block (ITI) (#25. #41~ #44).

In the correlation calculation of the third block (III), if the second block (n) determines that the LO-CON is not present, 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. L□-CO in the second block (H)
If it is determined as N, the third block (III)
Correlation calculation is performed under the total image shift amount.

In this way, as in the second block (II), θM3
calculation (#45), XM3. by interpolation calculation. YM3/C
3 (XM3) (#46), L, O-CON judgment (#47), and if it is not L O-CON, store the image shift amount P3 (#48) L, defocus limit Pm1
n-ρMl-25 is stored in memory and flag ZF-1 is set (#49). It is conceivable that P3 obtained here may be smaller than P2 by a difference of less than one pitch, but in that case, both Pm1n will be the same value, and it is impossible for Pm1n to decrease.

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

When a wide focus detection sensitivity range is selected in this way, the first
~ After the focus detection calculation is performed in the image shift range larger than the image shift amount of the block previously determined by the correlation calculation in the third blocks (I), (n), and (III), the zone counter becomes j-0. , moves to the lens driving routine of #38.

Here, the same routine as in FIG. 5 is performed again regardless of whether the focus detection sensitivity range changeover switch Sw (->n is ON, OF, or F).

First, it is determined whether there is a zone that is not LO-CON (#39). If the narrow focus detection sensitivity range of only the second block (n) is selected by turning on the focus detection sensitivity range changeover switch Sw (→nON), the determination will target only the second block (TI). Needless to say, the first to third blocks (1) and (II).

When (III) is LO-CON, the photographic lens = 36 = lens (2) moves from the closest state to ■ in the lowest base area, moves to LO-CON 5CAN which performs focus detection calculation,
Drives the lens. During this operation, several focus detection calculations are performed, all of which result in LO-CON, and LO-CON 5
When CAN is completed, the lens operation is stopped at the nearest lens end point or ■, and as long as the AP 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 an appropriate state for focus detection.

When a zone that is not LO-CON is detected, the image shift amount of the zone with the largest image interval, that is, the zone that includes the closest object among the objects, and the zone are extracted (#40). The image shift amount Pi is converted by multiplying the defocus amount by a certain constant (#13), and is stored as an n-zone number i. The obtained defocus amount is converted into a lens drive amount by taking the product of the defocus amount, which differs for each photographic lens (2), and the lens drive amount coefficient (
#14), and if the amount of lens drive is extremely small, the focus is displayed (#17), otherwise the lens is driven (#16), and then image sensor reintegration and refocus detection are performed. Perform calculations. After the focus display is displayed, the mode changeover switch 5o8c is sensed, and if the one-shot AF' mode is selected, the microcomputer (30) stops while displaying the focus display, and the continuous AP is activated. When the mode is selected, image sensor reintegration and refocus detection calculations are performed in the same way as in the out-of-focus state.

As explained below, in the first invention of the present application, the block with the largest image interval in the previous focus detection calculation is memorized, and in the case of refocus detection calculation, the first zone is stored for that block. Focus detection calculations are performed in the calculation routine. By performing the first focus detection correlation calculation in a flow branched by the set n, the focus detection calculation after the focus detection operation is performed quickly.

In this way, in this block subdivision focus detection calculation, the block with the largest image interval is extracted in the first zone calculation routine, and the block with the largest image interval is given priority in the subsequent focus detection calculation routine. When selected, the number of correlation calculations for subsequent block focus detection is reduced and the responsiveness of focus adjustment is improved.

Next, the flow of the embodiment of the second invention of the present application is shown in FIG.
) and shown in FIG. 7(b).

In this embodiment, in order to make the operation faster, the block with the largest image interval in the previous focus detection calculation is memorized, and in the case of refocus detection calculation, a limited amount of shift near the focus is used. Focus detection calculations are performed using the blocks stored in the memory, and if the data is reliable rather than LO-CON, the focus detection calculations are not performed at all using only other blocks and the lens is driven. .

In FIGS. 7(a) and 7(b), the first focus detection operation after the AF operation start switch S1 is turned on is exactly the same as that in FIG. 6. After the defocus amount is calculated here and the lens is driven according to the defocus amount (#13 to #I6), the lens driven flag SF, which was cleared in #20 at the start of AP operation, is set to l 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 re-integrates the image sensor,
Obtain new image information and repeat 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, from the focused image interval -2, -1, 0, 1,
Calculate the correlation value only for the image interval of the 5 points in step 2 (#62
). As a result, the image spacing that provides the highest correlation is -1, 0,
If it is either 1, interpolation is performed according to the value and LO-CON determination is performed (#63.#64.
#65) When it is determined that the value is highly reliable, lens driving is repeated according to the interpolated image interval XMn. That is, with this interpolated image interval XMn, #66 in FIG. 7(a)
After calculating the image interval deviation amount Pn, # in FIG. 7(b)
At step 13, the image interval deviation JIPn is converted into a defocus amount of -40-. 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, when the focus detection calculation finally determines 0-CON, the lens driven flag SF is cleared in #76, and this routine is not repeated after that, until the focus is detected again. Similar to the first focus detection calculation, the focus detection calculation is repeated for the entire defocus amount range and all blocks. Note that when focus is detected, the lens driven flag SF is set in #74 in the case of one-shot AP.

Here, we have shown an example in which refocus detection is performed after lens drive is completed, but it is also possible to repeat focus detection while driving the lens, and in such an example, the lens drive completed flag SF indicates focus detection. It can also be set only at the time.

In addition, here, the correlation value calculated image shift amount at the time of simple focus detection is set to 2.1.0. The five points -1 and -2 were chosen, but these values depend on the adjustment accuracy between the AF sensor and the re-imaging lens, and if sufficient accuracy is ensured, the three points J, O, and -1 are sufficient. Needless to say, it is Noh.

Finally, in FIGS. 6, 7(a) and 7(b), the focus detection sensitivity range changeover switch Sw<)n is turned on and off.
The r'F discrimination part is a mode changeover switch S.

←) By determining whether C is ON or OFF, it is possible to switch between wide and narrow focus detection sensitivity ranges using continuous AF and one-shot AF, as explained in FIG. 5.

Effects of the Invention According to the first invention of the present application, the current focus calculation is performed with a limited shift amount in the block from which the signal indicating the rearmost focus state selected in the previous focus detection calculation is obtained. Therefore, the shift range in the correlation calculation is limited, the calculation time for focus detection is shortened, and the ability to follow the subject is improved.

Further, according to the second invention of the present application, the reliability of the defocus obtained by the current focus detection calculation in the block from which the signal indicating the rearmost focus state selected in the previous focus detection operation was obtained is determined. Since the shift range is limited by this, there is less risk of focus detection being impossible even when the subject is moving, and when automatic focus adjustment is performed, continuous automatic focus adjustment is possible.

[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 line sensor, Figure 3 is an explanatory diagram of switching the focus detection sensitivity range within the camera's field of view, and Figure 4. is a flowchart of the interpolation calculation, FIG. 5 is a flowchart of the basic operation of the first and second inventions of the present application, and FIGS. 6, 7(a) and 7(b) are the flowcharts of the first and second inventions of the present application, respectively. Flowchart of the operation of the automatic focus detection device for a camera according to the invention of 2, FIG. 8 is an explanatory diagram of the focus detection optical system, FIG. 9 is an explanatory diagram showing the positions of two images in focus detection, and FIG. FIG. 3 is an explanatory diagram showing changes in focus amount. -43= I...Subject luminous flux, 2...Photographing lens, 9.1
1... Two images, 12.14... Photoelectric conversion element array. 15... line sensor, 20... photoelectric conversion circuit, 30
・Microcomputer. Patent Applicant Minolta Camera Co., Ltd. Representative Patent Attorney Aohaku Ao and 2 others - 44 = Figure 8 Figure 9 Figure 10

Claims (2)

[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. Camera automatic focus detection that detects the focus adjustment state of a photographic lens by determining the mutual positional relationship of both images from signals formed on the element array and indicating the illuminance distribution from the first and second photoelectric conversion element arrays. In the device, a first photoelectric conversion element array is divided into a plurality of blocks each having a predetermined number of pixels, and a light distribution signal of each block is compared with a light distribution signal from a second photoelectric conversion element array. It is equipped with a calculation means for determining the shift position where the best correlation can be obtained by shifting, and among the signals indicating the focus adjustment state of each block from this calculation means, the rearmost focus that is determined to be the object closest to the photographing lens is selected. A selection means for selecting a signal indicating the state as a signal indicating the focus adjustment state of the photographing lens, and a block that obtained the signal indicating the rearmost focus state selected in the previous focus detection calculation are stored in memory, An automatic focus detection device for a camera, characterized in that the automatic focus detection device for a camera is equipped with a calculation block selection means for causing the calculation means to perform a focus detection calculation with priority on the blocks stored in the memory in the detection calculation. (2) The subject light beams that have passed through the first and second regions 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. Camera automatic focus detection that detects the focus adjustment state of a photographic lens by determining the mutual positional relationship of both images from signals formed on the element array and indicating the illuminance distribution from the first and second photoelectric conversion element arrays. In the device, a first photoelectric conversion element array is divided into a plurality of blocks each having a predetermined number of pixels, and a light distribution signal of each block is compared with a light distribution signal from a second photoelectric conversion element array. It is equipped with a calculation means for determining the shift position where the best correlation can be obtained by shifting, and among the signals indicating the focus adjustment state of each block from this calculation means, the rearmost focus that is determined to be the object closest to the photographing lens is selected. A selection means for selecting a signal indicating the state as a signal indicating the focus adjustment state of the photographic lens, and a block in which a signal indicating the rearmost focus state selected in the previous focus detection operation was obtained is stored in memory, and the current block in this block is calculation area limiting means for determining the reliability of the data obtained by the focus detection calculation in the block and omitting the focus detection calculation in other blocks when the data is determined to be reliable. A feature of the camera's automatic focus detection device.