JPH0990206A - Automatic focusing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce operation quantity and to shorten necessary operation time by obtaining the contrast of a video concerning the output of respective video signals from plural line image sensors and calculating a focusing distance concerning the image sensor outputting the high-contrast video signal. SOLUTION: Correlative operation concerning a direction where total contrast quantity becomes large is preferentially performed so as to drive a lens; and the other correlative operation for detecting focusing is not performed until the direction shows low contrast because of influence that a subject is a long/ short distance competiting subject, and the lens is driven based on the result. A microcomputer generates difference data in a direction (x) first and obtains the sum of the adjacent difference of the difference data so as to calculate the total contrast value Cx in the direction (x). successively, the microcomputer calculates the total contrast value Cy in a direction (y) in the same manner. After calculating the total contrast values Cx and Cy in both directions (x) and (y), both values are compared, and the correlative operation concerning a direction Z where the total contrast value is large is preferentially performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the focus state of a photographic lens by receiving a subject image using a line image sensor, and drives the photographic lens based on the detected focus state to adjust the focus. The present invention relates to an automatic focusing device.

[0002]

2. Description of the Related Art Conventionally, the line image sensor as described above has been used for a focus detecting device of a camera, for example. However, this line image sensor has the following problems because it can detect only a linear light amount distribution in a single direction.

In a focus detecting device of a type that analyzes a video signal obtained by an image sensor, reliable focus detection cannot be performed unless the image on the image sensor has a certain degree of contrast. When a line image sensor is used as the image sensor, focus detection cannot be performed if the contrast of the image on the image sensor in the line direction is low, but even then, the image contrast in a direction different from the line of the sensor is often sufficient. When taking a picture of a person or an outside scene, the contrast in the horizontal direction is often higher than the contrast in the vertical direction.Therefore, when using a line image sensor for focus detection, the image sensor should be placed horizontally. It is rational. However, in this case, focus detection cannot be performed for a subject that happens to have a low horizontal contrast but a high vertical contrast. The same problem also occurs when the camera is used in the vertical position. This problem is solved by using a two-dimensional image sensor. As a focus detecting device of this type, a proposal has been made by JP-A-59-174807. The point of this proposal is to arrange the light-receiving elements two-dimensionally and form a subject image on it, and read the output of one row of light-receiving elements from this array of light-receiving elements to find if the contrast is insufficient. , Change the direction and read the output from the light receiving element array. In this way, focus detection calculation is performed by searching for a direction in which sufficient contrast is obtained, but it is expensive because a two-dimensional image sensor is used.

Therefore, it is conceivable to use a plurality of line image sensors having different line directions instead of the two-dimensional image sensor. In this case, the focusing distance (currently the photographing lens is used) for each line image sensor in each direction. When the lens movement amount from the position until the subject is in focus, that is, the focus state) is calculated, it takes time to complete the calculation of the focusing distance, and for example, the calculation of the focusing distance is repeated,
The responsiveness when the shooting lens is driven following a moving subject is lost.

[0005]

When the focusing distance is calculated using a plurality of line image sensors, the amount of calculation is reduced and the time required for calculation is shortened.

[0006]

In an automatic focus detection device capable of detecting a focus state in a plurality of areas of an object scene, an optical means for forming a subject image separately corresponding to the plurality of areas, and a plurality of the plurality of areas. The focus state is detected for each image pickup unit based on a plurality of image pickup units that are arranged corresponding to the regions and that receive the subject image formed by the optical unit, and the video signals output from these image pickup units. Calculation means for performing the calculation, a contrast detection means for detecting the contrast for each image pickup means based on the video signal output from each of the image pickup means, and a contrast detection means for each image pickup means. Based on the comparison result of the comparison means and the comparison result of the comparison means, the above calculation based on the output of the image pickup means having a small contrast is prohibited, Based on the output of the bets larger imaging means configured an automatic focus detecting device by a control means for controlling to perform the operation.

[0007]

According to the present invention, for each video signal output of a plurality of line image sensors, the contrast of the video is obtained, and the focusing distance is calculated for the image sensor which outputs the video signal of high contrast. The contrast does not require much time, but the calculation to obtain the focusing distance is multiple and takes a long time.Therefore, the focusing distance is calculated only by the selected image sensor instead of all the image sensors. The time required for calculation can be shortened. The image sensor that outputs a video signal with a high contrast is adopted here because the focus distance calculated with a higher video contrast is more reliable.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The content of the present invention is mainly described in FIG. 10 and its related explanation subparagraphs 0020 to 0029. First, the overall configuration and operation of the device of the present invention will be described.
Next, each part will be described in detail in order.

FIG. 1 is a perspective view of the arrangement of an optical system and an image sensor according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of the apparatus of the same embodiment. In FIG. 1, 1 is a taking lens of a camera, 6 is a condenser lens, 8 is four re-imaging lenses, and 10 is an image sensor. The condenser lens 6 forms an image of the pupil mask placed in front of the four re-imaging lenses 8 on the taking lens 1. The dotted circle drawn on the taking lens in the figure is this projected image. A field mask 2 having a cross-shaped opening is arranged on the front surface of the condenser lens 6, and the mask surface is a planned focal plane of the photographing lens 1 and is at a position equivalent to the film surface of the camera. The re-imaging lens 8 forms an image of the surface of the field mask 2 on the image sensor 10. In this configuration, for example, the image on the lens 1 by the condenser lens 6 of one of the re-imaging lenses 8 is a, and similarly, the image of b'is b, which is the circle of b of the taking lens 1. The image formed on the field mask 2 by the subject light that has passed through the enclosed area is formed on the image sensor 10 by the re-imaging lens a ′. Similarly, the image formed on the field mask 2 by the subject light that has passed through the area B on the photographing lens is formed on the image sensor by the re-imaging lens B '. The rectangles arranged in a cross shape on the image sensor 10 are images of the horizontal portion of the cross-shaped opening of the field mask 2 where X1 is the re-imaging lens B'and X2 is the cross-shape of the field mask formed by the re-imaging lens B '. It is an image of the horizontal part of the aperture. Similarly, Y1 and Y2 are images of the vertical portion of the cross-shaped aperture of the field mask formed by a pair of re-imaging lenses arranged in the vertical direction. An image of the same portion of the subject is formed on X1 and X2, but when the image of the subject by the taking lens 1 is formed on the field mask 2, that is, when the subject is in focus, the same portion of the subject is formed. With reference to the position of the re-formed image on X1 and X2, the re-formed images on X1 and X2 approach each other when the subject image is located closer to the taking lens than the field mask (front pin), and opposite. When they are rear pins, they move away from each other. Therefore, a line image sensor is arranged in the direction connecting X1 and X2, and X1
The image signal of the subject image on X ₂ is superimposed on the image signal of the subject image by shifting the image signals little by little and detecting the amount of shift that maximizes the correlation between the two image signals to obtain the correct image of the subject. It can be calculated how much to which side from the focus position. The above is the principle of focus detection in the present invention. Regarding the image signal processing operation, Japanese Patent Application Laid-Open No. 60-2472 was filed by the applicant of the present patent application.
No. 10. According to the above principle, line image sensors are arranged on the surface of the image sensor 10 along the direction of arrangement of X1 and X2 and the direction of arrangement of Y1 and Y2 which are orthogonal thereto.

In FIG. 2, the photographing lens is not shown in the figure, and the mirror which is inclined downward by 45 ° behind the transparent portion in the central portion of the single-lens reflex mirror and which is arranged downward is used to cut the transmitted light of the photographing lens by the infrared cut filter 3 and the field mask 2. , Is directed toward the condenser lens 6, and is further turned in the horizontal direction by the mirror 4 of 45 °, and is projected onto the image sensor 10 through the pupil mask 7 and the re-imaging lens 8 (two to four). 5
Is a frame that combines all the above-mentioned elements into one unit. The image sensor 10 moves in the horizontal direction (X
A line image sensor is arranged in each of a direction in which 1 and X2 are connected) and a vertical direction. A CCD image sensor is used as the line image sensor.

In the CCD image sensor, a photodiode and a capacitor for integrating the output photocurrent are elements for one pixel, and such elements are arranged in an array. Each element is integrated for a suitable time photocurrent. By applying a shift pulse to the integration control gate at the point where the signal is transferred, the light amount signal due to the accumulated charge of each element is transferred in parallel to the shift register, and then the transfer clock is applied to the shift register to A video signal is obtained by sequentially reading the charge signal as a voltage signal. FIG. 3 shows a circuit configuration around the CCD image sensor in the embodiment of the present invention. In this figure, PD array I to PD array IV are arrays of the above-mentioned elements in the CCD image sensor. PD array I is located at the position X1 in FIG.
2, the PD array II is located at the Y1 position, and the PD array IV is located at the Y2 position. Further, since the integration time of the photocurrent is determined by the average brightness of the image projected on the PD array, the photodiode (PD) M1 for monitoring is arranged along the PD array I and the monitoring photodiode along the PD array II. A photodiode (PD) M2 is arranged. G1 to G4 are integration control gate columns corresponding to PD arrays I to PD array IV and have a one-to-one correspondence with each element of the PD array. R1 and R2 are shift registers. The shift register R1 corresponds to the PD arrays I and IV, and when a shift pulse is applied to the integration control gates G1 and G4, the photocurrent integrated charges of each element in the PD arrays I and IV are shifted in parallel. Transferred to R1. The timings of the shift pulses applied to the integration control gates G1 and G4 are different. The shift register R2 corresponds to the PD arrays II and III, and
The charge signals in arrays II and III are transferred. These shift registers are driven by two-phase transfer clock pulses φ1 and φ2, and the information stored in the registers are sequentially output.

For convenience of explanation below, some words are decided. Regarding the direction of the line image sensor, the x direction (horizontal) and the y direction (vertical) are determined as shown in FIG.
These two directions are the directions indicated by arrows x and y in FIG. The total contrast is the sum of absolute values of differences between adjacent difference data in a video signal, and the larger the difference between light and dark, and the finer the mixture of light and dark, the larger the total contrast. "LowCon" is Low Conf
It is an abbreviation of "idence", which means that the reliability of focus detection is low. The configuration and operation of each part of the device will be described in detail below.

(CCD image sensor circuit) In FIG. 3, CCD analog shift registers R1 and R2 transfer charges by two-phase clocks φ1 and φ2. A voltage conversion unit and a buffer are provided at its output end, and the accumulated charges of the PD arrays I and IV are output from the OSI terminal via the analog shift register R1, and the accumulated charges of the PD arrays II and III are transmitted via the analog shift register R2 to OSII. It is output from the terminal. The output side of the monitor PD has the same structure as the accumulated charge of the PD array, and the accumulated charge of the monitor (PD) M1 is transferred from the AGCOSI terminal to the accumulated charge of the monitor (PD) M2 via the voltage converter and the buffer. Is output from the AGCOSII terminal. Further, in order to output the reference voltage of the monitor PD, there is provided a voltage conversion section to which the PD is not connected or the PD which is shielded from aluminum is connected, and the reference voltage DOS is output. This output is used to control the generation timing of the shift pulse described later.

The integration control gates G1 and G3 are x
A common shift pulse SH1 is applied via a terminal SH1 corresponding to the PD arrays I and III in the same direction. Similarly, the integration control gates G2 and G4 correspond to the PD arrays II and IV in the y direction, and the common shift pulse SH2 is applied via the terminal SH2. Further, shift pulses SH can be simultaneously applied to the integration control gates G1 to G4 via terminals SH. The video signal obtained from the CCD image sensor must have a signal level suitable for focus detection regardless of the brightness of the subject, so the integration time is controlled by the outputs of the monitor photodiodes (PD) M1 and (PD) M2. To be done. Here, since the average brightness of the strip portions of the subject in the x direction and the y direction may be different, the shift pulses SH1 and SH2 can be applied separately.

The PD arrays I to IV are integrated clear signals ICG.
Cleared all at once by the pulse, and the photocurrent integration starts from that point. Here, for example, when the average luminance of the strip portion of the subject in the x direction is higher than that in the y direction, the shift pulse SH1 is output first, and the photocurrent integration signals of the PD arrays I and III are intermediately output to the integration control gates G1 and G3. Retained. After that, when the video signals of the PD arrays II and IV reach an appropriate value, a shift pulse SH2 is issued and the PD
The photocurrent integration signals of the arrays II and IV are held intermediately in the integration control gates G2 and G4. Then each gate G
By applying the shift pulse SH to 1 to G4 all at once, all the video signals in the x direction and the y direction are shifted to the shift register R.
1 is transferred to R2.

As described above, the integration control gate G
1 to G4 have a function of temporarily holding the outputs of the PD arrays I to IV and transferring the outputs in parallel to the shift registers R1 and R2, and the circuit configuration therefor is shown in FIG. FIG.
Shows the structure for one pixel, and the charges photoelectrically converted by the PD array are accumulated through the barrier gate in the first accumulation portion C1 which is charged to almost the power supply level by the integral clear pulse ICG through the barrier gate. When the integrated signal obtained by monitoring the average brightness of the PD array column by the monitor PD reaches the appropriate integrated level, the SH ₁ or SH 2 pulse is applied, and the charge of each pixel is transferred from the storage section C 1 to C 2 in parallel.
At this time, the charge transfer is almost completely performed due to the capacitance difference between V1, V2, C1 and C2. In this way, the charges accumulated between the application of the ICG pulse and the application of the SHn (n = 1 or 2) pulse are transferred from the storage portions C1 to C2, and the other image is projected in this state. Wait for the PD array charge accumulation to complete. No photocurrent is generated in the second storage portion C2, and the charge amount is substantially maintained. When charge accumulation is completed in the other PD array, C
The charges of all the pixels of the CD image sensor are aligned in the second storage portion C2 at a level suitable for the focus detection calculation.
Next, by applying an SH pulse to the SH gate, the information of all pixels is transferred in parallel to the analog shift register at an appropriate level, and thereafter, in synchronization with the transfer clock, OSI,
This charge is sequentially output from the OSII terminal.

(Circuit for Performing Focus Detection and Focus Adjustment) Next, FIG. 5 shows a circuit configuration for driving the image sensor to perform focus detection and focus adjustment. Reference numeral 20 denotes an AF microcomputer that drives the image sensor 10, inputs the information, performs focus detection calculation, drives the lens through the motor drive circuit 90, and controls through the focus state display circuit 100. The AF microcomputer starts its operation when the AF start switch SAFS is turned on. 30 is x
Direction monitor output AGCOS1 is detected and x direction PD
A shift pulse generating circuit for generating a shift pulse SH1 for completing the integration of the arrays I and III, 31 is y
Direction monitor output AGCOS2 is detected and y direction PD
This is a shift pulse generation circuit for generating a shift pulse SH2 for completing the integration of the arrays II and IV. This circuit is composed of a circuit as shown in FIG. Reference voltage D
The OS is input to the buffer circuit Buf1 and a voltage obtained by lowering the output of the buffer circuit Buf1 by the constant voltage ΔV1 by the resistor R31 and the constant current I31 is applied to the (+) input of the comparator Com1. The monitor output A is applied to the (-) input of this comparator.
GCOSn is applied. Integral clear pulse ICG
Both outputs DOS and AGCOSn become equipotential, but thereafter the potential of AGCOSn decreases in proportion to the amount of charge generated in the monitor PD, that is, the amount of incident light. Looking at the input level of the comparator Com1, the (-) input is higher by .DELTA.V1 at the time of ICG application, but it decreases with charge accumulation, and when the (-) input becomes lower than the (+) input, the output of the comparator is inverted. If focus detection is performed at the average level of the video signal at the time of this inversion, an appropriate focus detection result can be obtained.
31, I31, that is, ΔV1 is set in advance. At this time, the inversion signal of the comparator COM1 sets the flip-flop FF31 reset by the pulse ICG, and the output inversion of the FF31 is converted into a pulse by the AND31, INV31 and the delay circuit 32 and output as the SHn (n = 1 or 2) signal. It Further, the time from the application of the pulse ICG to the output of this SHn signal requires a longer time as the brightness becomes lower. Therefore, the maximum integration time is set and the shift pulse SH is generated by the microcomputer when this time elapses. It is also possible to limit the integration time. Regarding how to handle these at low brightness, see JP-A-60-
It is equivalent to that described in No. 125817.

The circuit 40 is a transfer clock generation circuit,
The basic clock supplied from the microcomputer to the terminal is divided to generate φ1 and φ2 pulses. A signal for switching the transfer clock frequency is supplied to the Sφ terminal from the microcomputer 20, and this signal becomes High when the output in both the x and y directions is input, and only the output in one of the x and y directions. When inputting, the Sφ signal is set to Low and the transfer clock frequency is input as a double of the bidirectional output described above to shorten the charge transfer time. Further, since it is necessary to synchronize the charge transfer from the second storage means C2 to the analog shift register, the SH signal is input. Reference numerals 50 and 51 are analog processing circuits for the pixel outputs OSI and OSII, and the basic configuration is shown in FIG. The output of each pixel is output as a difference from the reference voltage V52 in the differential amplifier Amp51. This output is SP1 output by the microcomputer 20 when the dark output signal of the aluminum light-shielded pixel provided at the forefront of the output of each photodiode array PDI-IV is output.
Alternatively, the difference between the optical output which is sampled by the signal of SP2 and held by C51, and is output thereafter is output by the differential amplifier A.
Only the light output component is extracted by using mp52.

The reason why the dark output is sampled and held by each PD array I to IV is that the PD arrays I, III and II, IV are controlled by different integration times, and a difference occurs in the dark output voltage. is there. The pixel output in which only the light component is extracted in this way is then input to the sample hold circuits 60 and 61 and then to the multiplexer 70. Here, the multiplexer 70 outputs the sampled and held pixel outputs I1 and I1.
One of the two is selected by the input data selection zone signal SZ and output to the A / D conversion circuit 80 from the D1 terminal. As described above, when the microcomputer inputs data in both the x and y directions, the Sφ signal Hi is output to generate the transfer clock at the normal speed and AND2, OR1.
The output switching of the multiplexer 70 is switched in synchronization with the transfer clock φ1. As a result, as shown in the timing chart of FIG. 8A, the CCD shift register R1,
The output signals of the CCD shift register R2 are alternately output, digitized by the A / D conversion circuit 80 and input to the microcomputer. On the other hand, when inputting only the x direction or the y direction, the Sφ signal is set to Low and AND2
The output of the multiplexer is switched by setting one of the inputs to Low according to the selection signal SZ of the microcomputer. At this time, the transfer lock frequency of the CCD image sensor becomes double speed. The microcomputer inputs the standard part output in the x direction and the reference part output in the y direction and then SZ
Invert the signal and output CCD shift registers I and II x
Reference part output in direction Input standard part output in y direction. FIG. 8B shows the timing at which the data transfer time can be shortened by making full use of the A / D conversion time.

(Automatic Focus Detection Operation) In the present invention, several operation modes are possible for automatic focus detection. Specific examples of operations in these modes are shown in flowcharts in FIGS. 9 to 11. FIG. 9 is a flow of performing the focus detection calculation in the x direction and the y direction, and driving the lens based on the focus detection result in the direction in which the subject is determined to be closer to the camera as a result. FIG. 10 compares the total contrasts in both x and y directions, preferentially performs the focus detection calculation in the direction with high contrast to drive the lens, and performs the other focus detection calculation only when LowCon occurs and drives the lens. Is a flow for performing. Here, the contrast value becomes large and becomes LowCon, as an evaluation function YM (XN) / C by correlation calculation as proposed by the present applicant in Japanese Patent Laid-Open No. 60-247210 as a LowCon discrimination criterion.
Because it is also conditioned that N is less than or equal to a predetermined value,
In the case of a perspective competing subject, the evaluation function may be significantly deteriorated. FIG. 11 shows an example in which focus adjustment is performed by prioritizing the focus detection function in the x direction, and the focus detection function in the y direction is used only when the x direction becomes LowCon.

First, FIG. 9 will be described. When the AF switch SAFS is turned on, the microcomputer 20 is activated. The microcomputer first initializes the CCD image sensor. This is to discharge unnecessary charges previously stored in the register and the photoelectric conversion unit before power is supplied or while the transfer clock is stopped. Next, the microcomputer 20 supplies an ICG pulse to the CCD image sensor 10 to start integration. By applying this ICG pulse, the image sensor discharges the accumulated charge of each pixel and also discharges the accumulated charge of the monitor output, and when the pulse disappears, the accumulation of the generated charge is started by both of them. After that, the microcomputer
The inversion of both INT1 and TINT2 terminals, that is, the average of the charge accumulated in each pixel of the PD arrays I and III and PD arrays II and IV reaches a preset level, and the shift pulses SH1 and S1.
H2 is generated, and the accumulated charges of the PD arrays I and III are stored in the second storage portion C2 of each pixel and are stored in the second storage portion C2 of each pixel.
Wait until the charges accumulated in arrays II and IV are completely transferred. When the microcomputer detects this completion, the microcomputer generates an SH pulse and the accumulated charges in the PD arrays I and IV are analog shift register (CCD register).
Charges accumulated in the PD arrays II and III are transferred to R1 in parallel to an analog shift register (CCD register) R2.

Thereafter, the OSI, O are synchronized with the transfer clock.
Each pixel signal is output from both terminals of SII, and the microcomputer sends an A / D conversion completion signal A for the subsequent one pixel signal.
The number of output pixels is known by counting / DEOC, and the dark output sample signals SP1 and SP2 of the aluminum light-shielded pixels installed in each PD array I to IV are output, and each optical output that is subsequently output. Image information is obtained by sequentially inputting A / D conversion values of pixels. This timing will be described later.
In this way, when the digital information of all pixel outputs necessary for focus detection calculation is stored in the microcomputer,
The microcomputer starts the focus detection calculation. The microcomputer first performs a correlation calculation in the x direction. First, x-direction difference data is created. This difference data is Ux
(K) = Sx (k) -Sx (k + 4), Vx (k) = T
The difference between every fourth raw data is calculated as x-Tx (k + 4). This is to cut low frequency components that cannot be used for focus detection calculation. Difference data of standard part and reference part 27
When there are 35 pieces, the microcomputer calculates the correlation value YM (l) for each image shift amount while increasing the image shift amount by one pitch. Further, the total contrast value, that is, the sum of adjacent data of the difference data is obtained. Among the correlation values YM (l) thus obtained, the image shift amount having the highest degree of correlation, that is, lx that minimizes the value of the correlation value YM (l) is obtained. This lx is related to the lens defocus amount, but in the system used here, interpolation calculation is performed using the correlation value at the time of adjacent image shift and the correlation value at the image shift amount in order to obtain more accuracy. I do. This interpolation calculation is described in detail in Japanese Patent Laid-Open No. 60-247211 by the present applicant, so refer to it. In this way, the precise image shift amount XM and the correlation evaluation function YM (XM) can be obtained with high accuracy.
/ CX is required. This correlation evaluation function YM (XM) /
LowCon discrimination is performed at three points of CX, total contrast value CX, and all output raw data values. This LowCon discrimination is also described in Japanese Patent Application Laid-Open No. 60-247210 and will not be described here. When the correlation value at both ends of lx = 1 or 9 is minimum, LowCon is set.

When it is determined that the value is not LowCon, a PX value XM-5, that is, a difference from the image shift amount during focusing is calculated and stored. In addition, lmin = 1x−1 is set as a memory, and the image shift range of the correlation calculation in the y direction is limited. On the other hand, when it is determined to be LowCon, the image shift range of the correlation calculation in the y direction is not provided, and the correlation calculation is performed over the entire range. After the limitation of the correlation calculation range in the y direction is memorized in this way, difference data in the y direction is created in the same manner as in the case of the x direction. Uy (k) = Sy (k) −Sy (k +
4), Vy (k) = Ty (k) -Ty (k + 4) The correlation value is calculated in the same manner as in the x direction based on the difference data thus created. However, here, the correlation calculation is performed only for the image shift amount of 1 min or more obtained from the correlation calculation result in the x direction. This is because the closer the object is, the larger the image distance becomes. Therefore, the one in which the image shift amount of the correlation calculation result in both the x and y directions is large is selected. Therefore, it is sufficient to perform the correlation calculation only on a portion larger than the image shift amount in the x direction previously obtained, and the correlation calculation can be shortened. In this way, the correlation value is obtained also in the y direction, and the portion having the highest correlation is calculated. Next, interpolation calculation is performed as in the x direction, and the image shift amount xN and the correlation evaluation function YM (XN) / Cy are calculated as the correlation calculation result in the y direction. This evaluation function YM (XN) / Cy, the total contrast value Cy in the y direction,
The peak value of the raw data in the y direction is discriminated, and the minimum correlation value image interval lx is calculated for both ends lmin and 9 of the correlation calculation image shift amount
If it is determined that it is not LowCon, the image shift amount xN-5 from the focused state is stored as PY. When the correlation calculation in both the x and y directions is completed in this way, the microcomputer drives the lens based on the correlation calculation results in both the x and y directions.

First, when it is determined that both the directions are LowCon, the microcomputer drives the lens and performs an operation (LowCon Scan) for finding the lens position where the contrast can be detected. This operation is a mode in which the lens driving is stopped after the entire lens driving range has been scanned at least once, only the focus detection calculation is repeated at the lens position as it is, and the lens driving is restarted in the state where the contrast is detected. . At least one is LowC
If it is not on, the magnitudes of the obtained image shift amounts in the x-direction are compared, and the larger one is set as P and used as the image spacing amount used for subsequent lens driving. Here, it is assumed that the values of Px to Py are set to the Min value (-4) at LowCon. Despite the limitation in the y-direction calculation, the size comparison is purposely made here because the image shift amount has a considerable defocus amount within one pitch and a large difference in the defocus amount occurs due to the value calculated by the interpolation calculation. Is. The calculated image shift amount P is converted into a defocus amount, and the lens drive amount is calculated by multiplying the lens drive amount conversion coefficient that differs depending on the lens, and the focus determination is performed. When the lens drive amount is extremely small and it is not necessary to drive the lens, the focus display is performed. If not, the lens drive is performed according to the lens drive amount, and the focus detection operation of the image sensor is performed again to perform the focus detection operation. Perform reintegration.

Next, using the flowchart of FIG. 10, the lens is driven by preferentially performing the correlation calculation in the direction in which the total contrast amount is large, and the LowCon state is set due to the influence of the direction being a near-far competing object. The operation of the focus detection apparatus which performs the other focus detection correlation calculation for the first time, and drives the lens based on the result will be described. The image sensor data in both the x and y directions are stored in the microcomputer as in the case of FIG. 9 described above until the operation is started and the data input is completed. The microcomputer first creates x-direction difference data in the same manner as in the case of FIG. 9, and calculates the x-direction total contrast value Cx by calculating the sum of the adjacent differences of the difference data. Subsequently, difference data in the y direction is created and the y direction total contrast value Cy is calculated in the same manner. In this way, the total contrast values Cx and Cy in both the x and y directions are calculated, and then the magnitudes of the two are compared. Here, it is generally considered that the correlation calculation result in the direction in which the total contrast value is large is more reliable than the correlation calculation result in the direction in which the total contrast value is small.

Therefore, the direction Z in which the total contrast value is large
The correlation calculation is preferentially performed for. This correlation calculation is performed using the same method as that shown in FIG. An image shift amount xM and a correlation evaluation function YM (XM) / CZ are calculated by calculating a portion having a high correlation and performing an interpolation calculation. The LowCon determination is performed using this result, and when it is determined that it is not LowCon, the image shift amount XM is used to calculate the image shift amount at the time of focusing, and the differential focus amount and the lens drive amount are calculated. When it is determined whether or not the focus is achieved, the focus display is performed when the focus is achieved, and when the focus is not achieved, the lens is driven according to the lens drive amount. On the other hand, when it is determined to be LowCon, the correlation calculation in the reverse direction is performed this time. Based on this result, calculation of a highly correlated portion and interpolation calculation are performed, and the image shift amount XM, Y
Calculation of M (XM) / CZ is performed. The LowCon determination is performed again using this result, and when it is determined that the LowCon is not LowCon, the image shift amount from the in-focus state is calculated based on the image shift amount XM, and the differential focus amount and the lens drive amount are calculated. When it is determined whether or not the focus is achieved, the focus display is performed when the focus is achieved, and when the focus is not achieved, the lens is driven according to the lens drive amount. When it is determined to be LowCon, it is determined that both x and y directions are LowCon this time, so the above-described LowCon Scan is performed. The x-direction (horizontal direction) where the high-contrast part is often placed at the end
A focus detection apparatus which performs focus detection calculation in the y direction only when it is determined that the x direction is LowCon will be described with reference to the flowchart of FIG. 11. In this focus detection device, unlike the two examples shown in FIGS. 9 and 10, only data in the x direction is preferentially input. In order to shorten the integration time and the data transfer time and improve the system responsiveness, the microcomputer sets the transfer clock frequency to the double speed in the above example at the time when the initialization of the CCD is completed after the AF operation is started. Lo
Output w and perform high-speed output in one direction only as shown in FIG. 8B.

After the integration clear pulse is applied to start the integration, the microcomputer T indicates that the integration in the x direction is completed.
Wait for the inverted signal of INT1 signal. When the inversion of the TINT1 signal is detected, the microcomputer generates a shift pulse regardless of whether the integration in the y direction is completed or not, and starts inputting the pixel output data in the x direction. First, P from OS1
D array I, x direction reference part pixel output is output, so S
Z = Hi is output, and the D1 output of the multiplexer 70 is I
One signal, that is, an OS1 processed signal is used to A / D convert the output of the reference portion pixel in the x direction and input it to the microcomputer. During this period, the output of the y-direction reference portion output from OS2 is ignored. When the input of the x-direction reference portion is completed, the microcomputer outputs Sz = Low, and the D1 output of the multiplexer 70 is used as the I2 signal, that is, the OS2 processed signal of the image sensor, so that the output of the reference portion in the x-direction is A / D converted. And enter. Thus the reference part in the x direction,
When the input of the reference portion is completed, difference data creation, correlation value calculation, maximum correlation extraction, interpolation calculation, and LowCon determination are performed on these data as in the above-described two examples. As a result of the LowCon determination similar to those shown in the above two examples, Low
If it is determined that the obtained image shift amount is high reliability data instead of Con, a difference P = XM-5 from the focused image shift amount is calculated from the image shift amount. Defocus amount PF, lens drive amount When the lens drive amount is extremely small, it is determined to be in focus and the focus display is performed. If not, the lens is driven according to the calculated lens drive amount, and reintegration is performed for each pixel in the x direction. , The refocus detection calculation is repeated.

On the other hand, the focus detection calculation result in the x direction is LowC.
If it is determined to be on, the microcomputer then starts the integration and focus detection calculation of the image sensor in the y direction. The microcomputer outputs the integration clear signal ICG while outputting Sφ = Low to perform data input in one direction, and thereafter the integration completion signal TI in the y direction is generated.
Wait for NT2 to reverse. When this inversion of TINT2 is detected, an SH pulse is generated and input of y-direction data is started regardless of whether the integration in the x-direction is completed or not. At this time, contrary to the above-mentioned x-direction input, first, SZ = Low is output and the y-direction reference part output is I while ignoring the x-direction reference part output.
2 is passed through the multiplexer and data is input after A / D conversion. When this is completed, SZ = Hi is output and the output in the y direction is ignored while I1 is passed through the multiplexer in the A / D. Input data after conversion.

When all the data in only the y direction have been input in this way, the microcomputer creates difference data in the y direction, calculates the correlation value, extracts the highest correlation, performs interpolation calculation, and LowC.
The same procedure as that for performing the on determination in the x direction is performed. When it is determined that the image shift amount obtained as a result of the LowCon determination is not the LowCon and the data is highly reliable, the difference P = xM−5 from the image shift amount to the focused image shift amount.
Is calculated, the defocus amount DF, and the lens drive amount are calculated. When the lens drive amount is extremely small, the focus is determined to be displayed, and when it is not, the lens is driven according to the calculated lens drive amount. However, the refocus detection operation in the x direction is not performed at all, and the reintegration and refocus detection calculation for each pixel in the y direction is repeated. On the other hand, when it is determined that LowCon is also in the y direction, LowCo is determined in both the x and y directions.
Since it has been determined to be n, while performing LowCon Scan, reintegration and refocus detection are repeated in both directions of the image sensors x and y, and the state of LowCon is awaited.

[0030]

According to the present invention, even if a large number of image pickup means are used, the image pickup means outputting a high-contrast video signal is selected from among the image pickup means to calculate the focusing distance, so that the calculation time is shortened. Not only is the responsiveness of automatic focus adjustment obtained, but since the focusing distance is calculated from the video signal with high contrast, a highly reliable focusing distance can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing an optical configuration of the present invention.

FIG. 2 is an exploded perspective view of an optical portion according to an embodiment.

FIG. 3 is a circuit diagram around the image sensor in the same embodiment.

FIG. 4 is a circuit diagram of an integration control gate in the same embodiment.

FIG. 5 is a circuit diagram of a portion that performs image sensor driving, focus detection, and focus adjustment in the same embodiment.

FIG. 6 is a detailed circuit diagram of a part of the above circuit.

FIG. 7 is a detailed circuit diagram of another part of the same.

FIG. 8 is a time chart of the operation of the above circuit

FIG. 9 is a flowchart of one operation mode in the above embodiment.

FIG. 10 is a flowchart of another operation mode of the same.

FIG. 11 is a flowchart of another operation mode of the same.

[Explanation of symbols]

 1 Photographic lens 2 Field mask 6 Condenser lens 8 Re-imaging lens (2 to 4) 10 Image sensor

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[Procedure amendment]

[Submission date] August 1, 1996

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims] 1. In an automatic focus detection device capable of detecting a focus state in a plurality of regions of an object scene, optical means for forming a subject image separately corresponding to the plurality of regions, and arranged corresponding to the plurality of regions, A plurality of image pickup means for receiving a subject image formed by the optical means, and a calculation means for performing a calculation for detecting a focus state for each image pickup means based on a video signal output from each of these image pickup means , A contrast detecting means for detecting the contrast of each of the image pickup means based on the video signal outputted from each of the image pickup means, and a comparing means for comparing the contrast detected by each of the image pickup means by the contrast detecting means, Based on the comparison result of the means, the above-mentioned calculation based on the output of the image pickup means having a low contrast is prohibited, and the output based on the output of the image pickup means having a high contrast is used. There are automatic focus detection apparatus characterized by comprising a controller that controls so as to perform the above operation. 2. When the reliability of the focus state calculated based on the output of the image pickup means having a large contrast is low, the control means controls to perform the calculation based on the output of the image pickup means having a small contrast. The automatic focus detection device according to claim 1, which is characterized.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiko Karazaki 2-3-3 Azuchi-cho, Chuo-ku, Osaka, Osaka International Building Minolta Co., Ltd. (72) Inventor Hisao Morita 2-chome, Azuchi-cho, Chuo-ku, Osaka 3-13 Osaka International Building Minolta Co., Ltd. (72) Inventor Nobuyuki Taniguchi 2-3-13 Azuchicho, Chuo-ku, Osaka City Osaka International Building Minolta Co., Ltd.

Claims (2)

[Claims] 1. An automatic focus detection device capable of detecting a focus state in a plurality of areas of an object scene, comprising: an optical unit that forms a subject image separately for each of the plurality of areas; And a plurality of image pickup means for receiving the subject image formed by the optical means, and a calculation for detecting a focus state for each image pickup means based on a video signal output from each of these image pickup means And a contrast detecting means for detecting a contrast for each image pickup means based on a video signal output from each image pickup means, and a contrast detected for each image pickup means by the contrast detecting means. Based on the comparison result of the comparison means and the comparison means, the above-mentioned calculation based on the output of the image pickup means of the low contrast is prohibited, and An automatic focus detection device comprising: a control unit that controls the above calculation based on the output of the stage. 2. The control means, when the reliability of the focus state calculated based on the output of the image pickup means having a large contrast is low, performs the calculation based on the output of the image pickup means having a small contrast. The automatic focus detection device according to claim 1, wherein the automatic focus detection device is controlled as follows.