JPH08166535A - Focus detector and focus detecting method for camera - Google Patents

Abstract

PURPOSE: To provide a focus detector and a focus detecting method for a camera by which operation time in the case of detecting a focus is shortened and the focus is accurately detected even in the case of detecting the focus in a wide visual field that the coexistent state of distant and close subjects is easily caused. CONSTITUTION: A pair of subject images is received by a storage type line sensor 4 and photoelectrically converted. Furthermore, a CPU 1 divides a pair of electrical signals from the line sensor 4 to the specified number of blocks so as to extract plural characteristic points of every block. The CPU 1 arithmetically operates the contrast value and the degree of coincidence of the pair of electrical signals based on output on the extraction of the characteristic points for every block, and further performs correlation arithmetic operation based on the result of the arithmetic operation of the degree of coincidence and plural blocks to which a minimum value is given, and interpolation arithmetic operation and a relible value arithmetic operation to a part where correlativity is the highest.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detecting device for a camera using a phase difference type focus detecting method and a focus detecting method thereof.

[0002]

2. Description of the Related Art Conventionally, as an automatic focus detection method for a camera, a light flux from an object passing through different pupils is formed by 2
A so-called phase-difference focus detection method is known in which the focus state is detected from the amount of displacement of two images.

For example, Japanese Patent Laid-Open No. 59-126517 discloses a focus detection device for a camera as disclosed below. A pair of line sensors, each of which is divided into a plurality of overlapping blocks, and the contrast of each block of one of the line sensors, which is the reference portion, of the two images formed on each line sensor is obtained. Then, for a block with high contrast, the degree of coincidence between the two images with the corresponding block portion of the other line sensor as the reference unit is obtained by a correlation calculation.

In this method, first, a high-contrast portion (block) is searched for in the reference line sensor, and the correlation calculation is performed only with the corresponding portion (block) in the reference line sensor. Since it does not exist, the time required for the correlation calculation can be shortened.

[0005]

However, in the method disclosed in Japanese Patent Laid-Open No. 59-126517, when the specification is set so that defocus detection can be sufficiently performed in a wide field of view, that is, each line sensor in a pair of line sensors. However, when the specifications are long and the number of pixels of the sensor is large, there is a problem that the accuracy of the calculation result of the focus detection tends to deteriorate.

This is because in the case of a wide field of view, a distant view and a near view are present in the same field of view, that is, a so-called mixed state of the objects is likely to occur, and in this mixed state of the perspective, focusing is performed based on which object information. This is because it is not possible to accurately determine whether to perform detection.

As a countermeasure against this, in another conventional example, the field of view is made small by setting the size of the block of the line sensor of the reference portion small, and the distance information is separated. However, when performing the correlation calculation for checking the degree of coincidence between the reference portion and the reference portion, even if the reference block is small, the correlation calculation corresponding to the defocus amount is necessary, and the calculation is performed for the entire defocus range. Must be done. Therefore, by making the block smaller, the calculation time becomes considerably longer than in the conventional case.

On the other hand, it is conceivable that the data processing time can be shortened by thinning out the data and performing the calculation. However, simply thinning out the data only lowers the calculation accuracy and lowers the reliability.

Therefore, according to the present invention, a focus detection device for a camera and a focus detection device for the camera capable of shortening the calculation time at the time of focus detection and performing accurate focus detection even in the focus detection in a wide field of view in which the state of distant objects is likely to be mixed. It is intended to provide a detection method.

[0010]

In order to achieve the above object, a focus detection device for a camera according to a first aspect of the present invention comprises a pair of light fluxes from a subject passing through different pupil portions of a photographing lens. In a focus detection device for detecting a focus adjustment state of a photographing lens with respect to the subject based on the subject image, a storage type light receiving means for receiving and photoelectrically converting the pair of subject images, and a pair of the light receiving means. Each of the electric signals is divided into a predetermined number of blocks, and a plurality of characteristic points for each block are extracted, and a contrast value of each of the pair of electric signals is calculated based on the output of the characteristic extracting means. And the mutual matching degree for each block, and the correlation calculation is performed based on the calculation result of the matching degree and a plurality of blocks giving the minimum value. Characterized by comprising a second operation means for performing sexual high part per interpolation operation and the reliability value calculation.

Further, the camera focus detection device according to a second aspect of the present invention is characterized in that the plurality of feature points for each block are the maximum value and the minimum value of the signal in the corresponding block, respectively.

According to a third aspect of the focus detection method of the camera, the focus adjustment state of the photographing lens is based on a pair of subject images formed by a pair of light beams from the subject that have passed through different pupil portions of the photographing lens. In the focus detection method for detecting a light receiving step, the pair of subject images are received and photoelectric conversion is performed, and the pair of photoelectrically converted electric signals are divided into a predetermined number of blocks. Of a plurality of feature points, and the contrast values of the pair of electrical signals and the degree of mutual agreement for each block based on the feature point extraction result of the feature extracting step. The phase for performing the correlation calculation based on the first calculation step for calculating The imaging lens includes a calculation step and a second calculation step for performing an interpolation calculation and a confidence value calculation for a portion having the highest correlation based on the correlation calculation result obtained by the correlation calculation step. Is output.

[0013]

In the focus detection apparatus for a camera of the present invention, the focus adjustment state of the photographing lens for the subject is determined based on the pair of subject images formed by the pair of light beams from the subject that have passed through different pupil portions of the photographing lens. In the focus detecting device for detecting, the pair of subject images are received by photoelectric conversion means and photoelectrically converted. Further, the pair of electric signals from the light receiving unit is divided into a predetermined number of blocks by the feature extraction unit, and a plurality of feature points in each block are extracted.

Then, based on the output of the feature extracting means, the contrast value of each of the pair of electric signals and the degree of coincidence with each other are calculated by the first calculating means for each block, and the second value is calculated. Correlation calculation is performed by the calculation means based on the calculation result of the degree of coincidence and a plurality of blocks giving the minimum value, and interpolation calculation and reliability value calculation are performed for the portion having the highest correlation.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a signal processing unit which is a feature of a focus detection apparatus according to an embodiment of the present invention.

This focus detection device is a CPU (Central Processing Unit; CP) for controlling the operation of the entire device.
U) 1, a control unit 2 that receives an instruction from the CPU 1 to control the operation of each circuit of the focus detection unit, and a focus detection unit 3 that receives a light beam from a subject and outputs a signal for focus detection. Composed of. Here, the control unit 2 and the focus detection unit 3 are formed on one sensor chip.

The CPU 1 controls the operation of the focus detecting device, and at the same time, performs analog / digital (hereinafter referred to as A / D) conversion of the output signal from the focus detecting section 3 to perform arithmetic processing.

The CPU 1 sends to the control unit 2 a signal MON for sampling and holding the monitor output voltage, a signal RES for resetting the accumulated charges, a signal END for ending the accumulation of charges, a chip enable signal CEN, and the retained charges. A signal READ for controlling the reading of the signal and a signal GAIN for controlling the gain of the focus detection signal are output. The control unit 2
Receives these signals and controls the operation of each part of the circuit of the focus detection unit 3.

The pair of line sensors 4 are composed of a light receiving portion 4a which is composed of pixels which receive a light beam from a subject and outputs an image signal, and a light-shielded pixel which outputs a current corresponding to the dark current of the line sensor 4. And a light shielding portion 4b. For simplification, FIG. 1 shows the pair of line sensors 4 as one block.

A peak detector 5a for monitoring the accumulation state of the output of the image signal is connected to the light receiving portion 4a, and a peak detector 5b is connected to the light shielding portion 4b. The subtracter 6 obtains the difference between the peak-detected outputs of the peak detectors 5a and 5b, and the output is guided to the output unit 8 through the sample-hold circuit 7.

Further, the light receiving section 4a is constructed so as to automatically switch between high sensitivity and low sensitivity according to the brightness of the subject. (Note that this switching is automatically performed according to the brightness of the subject under the control of the sensitivity switching control unit (not shown).) Then, the control unit 2 responds to the signal END from the CPU 1 to switch unit 9a, 9b is switched. This switching is switched so that it is output from the switch unit 9a when monitoring the accumulation state, and is output to the A / D conversion input unit of the CPU 1. On the other hand, when the accumulation is completed by the signal END under the above control, the switch section 9b is switched to output and the AF signal output described later is output as the distance measurement output AFDATA to the A / D conversion input section of the CPU 1. To do.

Further, in the light receiving section 4a, the control section 2 controls the CP.
It is initialized in response to receiving the signal RES from U1 and starts accumulation. When the light receiving section 4a accumulates a predetermined amount of electric charge, the electric charge accumulated in each pixel of the light receiving section 4a is sent to the reading section 10 in response to the accumulation end signal END.
The reading of the accumulated charge from the light receiving unit 4a is performed alternately by one of the pair of line sensors 4 as a standard unit and the other line sensor as a reference unit. Further, the control unit 2 receives the signal REA from the CPU 1.
In accordance with D, the shift register 11 sequentially reads the charges held in the reading section 10.

The read signal is amplified by the amplifier 12 into a signal of a predetermined magnitude based on a preset amplification factor, and then subtracted by the subtractor 13 from the signal of the light receiver 4a to the light shield unit 4.
The signal for b is subtracted and the AF signal is output.

In FIG. 2, the distance between the two images formed on the standard row 21L, which is the line sensor of the reference section, and the reference row 21R, which is the line sensor of the reference section, is calculated from the signal obtained by the line sensor 4. It is a figure for explaining the method of doing.

The two images formed in the standard row 21L and the reference row 21R are arranged so as to form images at substantially central positions on the line sensor 4 when focused, and are formed in front of the line sensor 4. In this case, the image is moved (shifted) to the inside by the same amount in the opposite direction when the image is formed behind the line sensor 4.
That is, it moves (shifts) in a predetermined relationship with respect to the degree of focusing on the film surface.

Now, a method for obtaining the shift amounts of the two images in this embodiment will be described below. A size corresponding to the visual field on the film surface is defined as a visual field V. The shift on the reference column 21L side starts from the position Sastart at the left end of the reference column 21L.
At the position where the visual field V reaches the right end, the leftmost point in the visual field V is the position S
Shift in step d until astop. Step d
Shifting with has an advantage that feature point detection within the visual field V described later can be performed more easily than each time. In this embodiment, step d = 3.

On the other hand, the shift on the reference row 21R side is
Shifting is performed at positions corresponding to the respective positions of the reference row 21L. Here, the position of the reference row 21R corresponding to the step number d of the standard row 21L is shifted in the opposite direction from the standard row 21L by the step d. Therefore, with respect to one step of the standard column 21L, the reference column 21R shifts from the position corresponding to the standard column 21L to +3 and -2 in -1 step. This is repeated to detect the degree of coincidence between the two images. FIG. 3 that calculates the distance between the two images from the degree of coincidence is a diagram showing the configuration of the optical system of the focus detection apparatus of this embodiment.

A light beam passing through different pupils of the taking lens 30 passes through a field stop 31 and a condenser lens 32 provided in the vicinity of the primary image forming plane, and is divided by a stop mask 33 into two light beams forming two images. To be After that, the two light fluxes pass through the separator lens 34 and are re-imaged on the line sensor 4 provided in the sensor 35. The blur of the image in the optical axis direction on the primary image forming surface appears on the line sensor 4 by the movement in the direction orthogonal to the optical axis, and the focused state is detected from the interval between the two images.

Next, the operation of the signal processing unit, which is a feature of the focus detection apparatus according to the embodiment of the present invention, will be described. 4 and 5 are flowcharts showing the processing of the CPU 1 of the signal processing unit which is a feature of the focus detection apparatus of the embodiment.

After reading the data, the following variables are initialized (step S1). First, Cmin1 = 50, Cm
in2 = 7, Cmin = Cmin1, LX = 0, LN =
It is set to 255. Also, of C (CK, L) = 0, CK
= 0 to 23 and L = 0 to 3. Furthermore, min (L)
= 255 out of 255.

Next, the difference processing is performed from all the pixels on the side of the reference column 21L by the following equation, LX = max {128-d (i + 3) + d (i)} LN = min {128-d (i + 3) + d (i)}. And calculate LX and LN. here,
i represents the number of signals on the reference column 21L side (step S2).

Next, the CPU 1 sets LX-LN <Cmin.
It is determined whether the condition of 2 + 5 is satisfied (step S
3). Here, when the condition of LX-LN <Cmin2 + 5 is satisfied, the signal becomes low contrast when the difference processing is performed, and the calculation result becomes unreliable in the detection calculation.
Therefore, the signal data is preprocessed only when the condition of LX-LN <Cmin2 + 5 is not satisfied.

The above-mentioned preprocessing is an averaging processing by adding three pixels. D (i) = int [{d (i-1) + d (i) + d (i
+1)} / 3] to smooth high-frequency noise (step S
4).

Next, d (i) = 128-d (i + 3) + d (i), which is a difference process between three pixels, is performed on the data averaged in step S4 to remove low frequency noise ( Step S5).

After these pre-processes, the loop counter Sa for moving the visual field V on the reference row 21L side is set to Sa = Sasta.
rt (step S6). Then, the visual field V on the reference row 21L side is divided into four blocks, and the loop counter L for moving the position of each block is set to L = 0 (indicating the leftmost block) (step S7).

Next, the CPU 1 uses Cmin = Cmin2
Then, it is determined whether or not the contrast determination flag C (CK, L) at Cmin2 in each block is "1" (step S8). When this condition is not satisfied, the maximum value position mx (L) and the minimum value position mn (L) are detected from the signals in each block, and the maximum value and the minimum value are obtained (step S9). .

Then, the contrast is determined. At this time, the contrast is determined in two stages, and the “maximum value-minimum value” in the block is set to Sinn, and the contrast determination is performed under the following conditions. Here, in this embodiment, the determination value is set to Cmin1 = 50, C as set in step S2.
Let min2 = 7.

First, it is determined whether or not the condition of Sinn <Cmin2 is satisfied (step S10). Sinn <C
When the condition of min2 is satisfied, the process jumps to step S16 and L = L + 1 is set in order to detect the next block. On the other hand, if the condition of Sinn <Cmin2 is not satisfied, the process proceeds to step S11, and Sinn <Cmin1.
It is determined whether or not the condition of is satisfied. Sinn <Cmin
When the condition of 1 is satisfied, that is, Cmin2 ≦ Si
When the condition of nn <Cmin1 is satisfied, the contrast determination flag C (CK, L) is set to “1” (step S1).
3), the position of the maximum value and the minimum value at that time, mx
(CK, L) = mx and mn (CK, L) = mn are stored (step S14), and the process proceeds to step S16. Here, CK represents a shift position of the reference column 21L, L represents a block position, mx represents a maximum value position, and mn represents a minimum value position.

On the other hand, when the condition of Sinn <Cmin1 is not satisfied, that is, when Sinn ≧ Cmin1, it is determined that the contrast is sufficient, and the process proceeds to step S15.

In step S8, Cmin =
When the contrast determination flag C (CK, L) in Cmin2 in each block satisfies the condition of "1", the process proceeds to step S12, and the maximum value in the block stored in the process described later is performed. Value mx (L) and the minimum value position mn (L) are read (step S1).
2) and shifts to step S15.

In step S15, the comparison data min (L) is calculated from the maximum and minimum values in the block used for contrast detection in step S9. This comparison data min (L) is obtained by comparing the absolute value comparison amount from the sum of the two points and comparing the change amount from the difference between the two points in order to compare the features of the two points. At this time, the positions of the maximum value and the minimum value of the block L and their sizes are respectively [mx (Sa + LL + mx), d {mx (Sa + LL +
mx)}] [mn (Sa + LL + mn), d {mn (Sa + LL +
mn)}] and mL1 = d {mx (Sa + LL + mx)} + d {mn
(Sa + LL + mn)} mL2 = d {mx (Sa + LL + mx)}-d {mn
(Sa + LL + mn)} is calculated. Here, LL gives the head position of the block L, and LL = 11 × L. The signal value of the reference row 21R corresponding to each of the positions is [mx (Sb + LL + mx), d {mx (Sb + LL +
mx)}] [mn (Sb + LL + mn), d {mn (Sb + LL +
mn)}], the comparison data of the reference column 21R corresponding to the standard column 21L is: mR1 = d {mx (Sb + LL + mx)} + d {mn
(Sb + LL + mn)} mR2 = d {mx (Sb + LL + mx)}-d {mn
(Sb + LL + mn)}. Here, Sb is the block start position on the reference column 21R side corresponding to Sa, which represents the block start position on the standard column 21L side.

When the object has a predetermined shift amount, the magnitudes of the signals at the respective positions of the standard row 21L and the reference row 21R have substantially the same value. Therefore, the difference of the comparison data obtained for each column in order to check the size is expressed by min (L) = | mL1-mR1 | + | mL2-mR2
|, And the min of four blocks in the loop
Of (L), the minimum value is stored as min (L).

After that, L = L + 1 is set (step S1
6) and shifts to step S17. In step S17, it is determined whether or not the condition of L ≦ 3 is satisfied. here,
When the condition of L ≦ 3 is satisfied, the process returns to step S8 and the processes of steps S8 to S17 are repeated. L
When the condition of ≦ 3 is not satisfied, the process proceeds to step S18. That is, for all four blocks,
Repeat the processing from step S8 to step S17,
Similarly, min (L) is calculated.

After that, the CPU 1 shifts Sa by +3 steps (step S18), and determines whether or not the condition of Sa≤Sastop is satisfied (step S19). Here, when the condition of Sa ≦ Sastop is satisfied, the process returns to step S7, and the processes from step S7 to step S19 are repeated. When the condition of Sa ≦ Sastop is not satisfied, the process proceeds to step S20.

When the comparison calculation for each block is completed, the contrast determination flag C is set in step S20.
It is determined whether or not even one (CK, L) is "1". If the contrast determination flag C (CK, L)
If even one is not "1", it is determined that the contrast is low, and the process branches to step S34 to perform the out-of-focus determination.

On the other hand, the contrast determination flag C (CK,
If even one of L) is "1", it is determined whether or not min (L) of the contrast detection value is the initial value 255 (step S21). Here, when the initial value is still 255, the contrast condition of Cmin1 has not been reached, so the process of step S15 is not performed.
At this time, Cmin = Cmin2 (step S2
2) and returns to step S6. On the other hand, when min (L) is not the initial value 255, the process proceeds to step S23.

At step S23, min of each block
Among the minimum values of (L), the minimum value and the second smallest value are detected as Fi1 and Fi2, respectively. Then, the block of the visual field used for distance measurement calculation is selected by the method described later with reference to FIG. 6 (step S24).

The true minimum value is calculated below using all the data in the selected field of view. With respect to the shift amount position of the visual field selected in step S24, the correlation calculation is performed by the following formula from the signal data on the standard column 21L side and the reference column 21R side within a range shifted by ± 2 pixels. Here, the ± 2 pixel shift is performed because the shift calculation is not performed on the standard column 21L side and the reference column 21R side, and in some cases, the previously obtained position may not be the minimum position. Occurs. Therefore,
As a countermeasure, the size of min (L) at the adjacent position is also checked. The following equation is used for the correlation calculation equation.

[0049]

[Equation 1]

It is assumed that the minimum value is Fmin, the value in the -1 shift is Fm, and the value in the +1 shift is Fp. Furthermore, the values of the autocorrelation at positions shifted by ± 1 pixel from the detection position on the reference row 21L side are Fm1 and Fp, respectively.
Set to 1. These can be expressed by the following equations.

[0051]

[Equation 2]

[0052]

(Equation 3)

[0053]

[Equation 4]

[0054]

(Equation 5)

Interpolation calculation is performed from these values by the method described later to obtain the minimum value zr and the reliability coefficient SK for evaluating the reliability of the value (steps S25 and S26). next,
The CPU 1 determines whether or not the condition of SK <SK0 is satisfied (step S28). Here, when the condition of SK <SK0 is satisfied, it is determined that there is reliability, and the line sensor 4
Deviation amount d from the upper deviation amount zr in the optical axis direction of the film surface
Is converted by the following equation (step S29), and the process proceeds to step S30.

D = b- (axb) / (a + zr) + cx
zr, (a, b, and c are coefficients) In step S30, focus determination is performed, and this processing ends. On the other hand, in step S28, when the condition of SK <SK0 is not satisfied, that is, when it is determined that the reliability is low, the process proceeds to step S31, and the view selection condition is set depending on whether Fi = Fi1 is satisfied. The determination is made (step S31). Here, when Fi = Fi1 is satisfied, the field of view is set to Fi = Fi2 (step S32), and based on this condition, the process returns to step S24 to change the field of view block.

When Fi = Fi1 is not established, it is already set to Fi2, and it is determined whether or not the contrast condition Cmin = Cmin1 is established (step S33). Here, Cmin = Cmin1
Does not hold, that is, Cmin = Cmin2
In the case of, the out-of-focus determination is performed (step S34), and this processing ends. On the other hand, when Cmin = Cmin1 is satisfied, the process returns to step S22 and Cmin = Cmin2
Then, the process returns to step S6, and the processes after step S6 are performed again. The above is the flow of focus detection processing.

FIG. 6 is a diagram showing the relationship between the maximum value and the minimum value of each block on the standard column 21L side and the value of each position on the corresponding reference column 21R side by dividing the block in the visual field into four. Is.

VL and VR are on the reference column 21L side,
The size of the block corresponding to the visual field at the position corresponding to the shift amount on the reference row 21R side is shown. Also, BL0 to BL3, B
R0 to BR3 represent the position of each block obtained by dividing the visual field into four. The maximum and minimum values in each field of view are the reference row 21L
Calculate for each block on the side. Now, the positions of the maximum value and the minimum value of each block are mx (L) and mn (L), respectively.
In other words, as described above, for example, regarding the leftmost block, it is stored as mx (0) = Sa + mx0, mn (0) = Sa + mn0. Here, mx0 is a block shift amount from the left end to the maximum value, and mn0 is a block shift amount from the left end to the minimum value. The other blocks are Sa
The block shift amount is further added from the position of.

At this time, since the position on the reference row 21R side corresponding to the position on the base row 21L side is known in advance, the position on the reference row 21R side corresponding to the maximum value and minimum value positions of each block described above. Select the signal output. Although there are only two points, they are the most characteristic points in both the information on the size and the contrast difference. If the calculation time has a margin, a point representing the maximum difference value in the block may be added. Two points may be added to the maximum difference value, or, for example, when a maximum difference value at two pixels apart is obtained, one point between them may be added. That is, when the processing of d (i) = 128−d (i + 2) + d (i) is performed, the position where the maximum difference value is obtained is set as d (i) = d (i + 1).

All of these points are the most representative points of the feature of the block, and sufficient information can be obtained without using all the points in the block. Contrast detection is shifted on the reference line 21L side by three steps, so it must be reviewed every shift. However, when the maximum or minimum point is in the range after the shift, the contrast condition is satisfied, so the maximum and minimum determination may be omitted. Even if not omitted, it is sufficient to newly compare three pixels. When the maximum or minimum point is out of the shift range after the shift, detection is performed again in the entire block.

FIG. 7 is a diagram showing a method of selecting a field block in step S24 in the flowchart of FIG. Of the comparison data min (BL), BL = 0 to 3 obtained for each block as a result of the shift operation, when the block Fi1 giving the minimum value is BL = 1 or 2,
The field of view selects blocks of BL = 1 and BL = 2. When the block Fi1 giving the minimum value is BL = 0,
For the field of view, select blocks of BL = 0 and BL = 1. Furthermore, when the block Fi1 giving the minimum value is BL = 3,
The field of view selects the blocks of BL = 2 and BL = 3, respectively.

The block Fi2 having the second smallest value
When Fi2 is BL = 1, the field of view selects blocks of BL = 0 and BL = 1. Also,
When Fi2 is BL = 2, the field of view selects blocks of BL = 2 and BL = 3. Further, when Fi2 is BL = 0 or BL = 3, the field of view selects blocks of BL = 0 and BL = 3.

Of the two blocks selected as described above, the smaller block number of the reference column 21L,
By storing the leftmost pixel number of the reference column 21R, the position of the pixel when performing the correlation calculation can be known.

FIG. 8 is a diagram showing a method of interpolation calculation in step S26 in the flowchart of FIG. As shown in the figure, Fm and Fmi of three points obtained by the correlation calculation
For n and Fp, the position of the inflection point when the position where the straight line of the slope obtained from the autocorrelation of the reference column 21L passes closest to the above-mentioned three points is selected as the true minimum value. This utilizes a method of obtaining a straight line by the least square method with respect to an operation result that originally includes an error.

When Fm ≦ Fp, zr = zr0− (Fp1-2 × Fm + Fmin + Fp)
/ {2 × (Fp1 + Fm1)} When Fm> Fp, zr = zr0 + (Fm1-2 × Fp + Fmin + Fm)
/ {2 × (Fp1 + Fm1)} Here, Fp1 and Fm1 are values obtained by autocorrelation, zr represents a two-image interval, and zr0 represents a reference two-image interval.

Further, the reliability coefficient SK uses Fmin, Fm, and Fp at three points used for interpolation. When Fm ≦ Fp, SK = (Fmin + Fm) / (Fp
-Fmin) When Fm> Fp, SK = (Fmin + Fp) / (Fm
-Fmin).

As described above, according to this embodiment, the comparison operation is performed using a large number of pixels from both ends and a small amount of data between them, and the field of view for the interpolation calculation is determined from the result, and focusing is performed. Seeking position. As a result, the focus detection system with a large amount of data and a large amount of deviation can be calculated in a short time, and a smooth focusing operation can be performed without being affected by the perspective competition occurring in the wide field of view.

According to the above embodiment of the present invention, the following configuration can be obtained. (1) Light receiving means for photoelectrically converting the first and second optical images based on the light flux from the subject that has passed through the taking lens, and processing for obtaining the focus adjustment state of the taking lens for the subject based on the output signal from the light receiving means A phase-difference-type focus detection device comprising: a means for dividing the signal of the first optical image into a plurality of blocks, and detecting a plurality of pixels having characteristics from a predetermined pixel signal in the block. And a pixel signal of the block of the second optical image corresponding to the block position of the first optical image by dividing the signal of the second optical image into a plurality of blocks. From a plurality of pixels at positions corresponding to a plurality of pixels having the above characteristics, the second arithmetic means for performing arithmetic operation, the arithmetic result by the first arithmetic means, and the arithmetic result by the second arithmetic means. Comparison hand to compare A distance measuring device comprising: a stage; and a correlation calculation unit that performs a correlation calculation on the signal of the first optical image and the signal of the second optical image based on the comparison result of the comparison unit. (2) Light receiving means for photoelectrically converting the first and second optical images based on the light flux from the subject that has passed through the taking lens, and processing for obtaining the focus adjustment state of the taking lens for the subject based on the output signal from the light receiving means. A phase-difference-type focus detection device comprising: a means for dividing the signal of the first optical image into a plurality of blocks, and detecting a plurality of characteristic pixels from a predetermined pixel signal in the block And a pixel signal of the block of the second optical image corresponding to the block position of the first optical image by dividing the signal of the second optical image into a plurality of blocks. From a plurality of pixels at positions corresponding to a plurality of pixels having the above characteristics, the second arithmetic means for performing arithmetic operation, the arithmetic result by the first arithmetic means, and the arithmetic result by the second arithmetic means. Comparison hand to compare A step, a field-of-view selection means for selecting a field of view based on the comparison result of the comparison means, a field of view selected by the field-of-view selection means, and a signal of the first optical image based on the comparison result of the field of view. A distance measuring device comprising: a correlation calculating unit that performs a correlation calculation with respect to the signal of the second optical image. (3) The distance measuring device according to (1) or (2), wherein the calculation by the first calculation means is performed when a plurality of pixels having the above characteristics satisfy a predetermined condition. (4) The distance measuring apparatus according to (1) or (2), wherein the feature extraction by the first computing means includes at least a maximum value or a minimum value in the signal of the predetermined block. (5) The distance measuring apparatus according to (1) or (2) above, wherein the feature extraction by the first computing means comprises a signal obtained by preprocessing a signal in a signal of a predetermined block. (6) When preprocessing the first arithmetic means, whether or not to execute the processing is determined based on the signal of the first optical image. The distance measuring apparatus according to (5) above. . (7) The distance measuring apparatus according to (5), wherein the pre-processing is performed by combining a plurality of filter calculations.

[0070]

As described above, according to the present invention, even in the focus detection in a wide field of view in which the state where objects are distant and near are likely to occur, the calculation time for focus detection can be shortened and accurate focus detection can be performed. A focus detection device for a camera and a focus detection method thereof can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a signal processing unit that is a feature of a focus detection apparatus according to an embodiment.

FIG. 2 illustrates a method of calculating a distance between two images formed on a standard row 21L which is a line sensor of a standard section and a reference row 21R which is a line sensor of a reference section from a signal obtained by a line sensor 4. FIG.

FIG. 3 is a diagram showing a configuration of an optical system of a focus detection device according to an embodiment.

FIG. 4 is a flowchart showing the processing of the CPU 1 of the signal processing unit, which is a feature of the focus detection apparatus of the embodiment.

FIG. 5 is a flowchart showing the processing of the CPU 1 of the signal processing unit, which is a feature of the focus detection apparatus of the embodiment.

FIG. 6 is a diagram showing the relationship between the maximum value and the minimum value of each block on the standard column 21L side and the value of each position on the corresponding reference column 21R side by dividing the block in the visual field into four.

7 is a diagram showing a method of selecting a block of a visual field in step S24 in the flowchart of FIG.

8 is a diagram showing a method of interpolation calculation in step S26 in the flowchart of FIG.

[Explanation of symbols]

1 ... CPU (Central Processing Unit; CP)
U), 2 ... Control unit, 3 ... Focus detection unit, 4 ... Line sensor, 4a ... Light receiving unit, 4b ... Light shielding unit, 5a, 5b ... Peak detection unit, 6 ... Subtractor, 7 ... Sample hold circuit, 8
... output section, 9a, 9b ... switch section, 10 ... readout section, 11 ... shift register, 12 ... amplification section, 13 ... subtractor, 21L ... standard row of line sensor, 21R ... reference row of line sensor, 30 ... photography Lens, 31 ... Field stop,
32 ... Condenser lens, 33 ... Aperture mask, 34 ... Separator lens, 35 ... Sensor.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03B 3/00 A

Claims (3)

[Claims] 1. A focus detection device for detecting a focus adjustment state of a photographing lens for a subject based on a pair of subject images formed by a pair of light fluxes from the subject that have passed through different pupil portions of the photographing lens. Storage type light receiving means for receiving and photoelectrically converting a pair of object images, and a pair of electric signals from the light receiving means are each divided into a predetermined number of blocks, and a plurality of characteristic points for each block are extracted. Extraction means, first calculation means for calculating, for each block, the respective contrast values of the pair of electric signals and the mutual matching degree based on the output of the feature extracting means; Second calculation means for performing a correlation calculation based on the calculation result and a plurality of blocks giving the minimum value and performing an interpolation calculation and a confidence value calculation for the portion having the highest correlation. Focus detecting device of a camera according to claim. 2. The focus detection device for a camera according to claim 1, wherein the plurality of feature points for each block are a maximum value and a minimum value of a signal in the corresponding block, respectively. 3. A focus detection method for detecting a focus adjustment state of a photographing lens based on a pair of subject images formed by a pair of light fluxes from the subject that have passed through different pupil portions of the photographing lens, wherein the pair of subjects A step of receiving an image and performing photoelectric conversion, a step of dividing the photoelectrically converted pair of electric signals into a predetermined number of blocks, and extracting a plurality of characteristic points in each block, A first calculation step of calculating, for each block, the contrast value of each of the pair of electric signals and the degree of mutual agreement based on the extraction result of the characteristic points by the characteristic extraction step; The correlation calculation step of performing a correlation calculation based on the calculation result of the degree of coincidence by the calculation step and the plurality of blocks giving the minimum value, and the correlation calculation step. Based on the correlation calculation result,
A second calculation step for performing an interpolation calculation and a confidence value calculation for the portion having the highest correlation, and outputting a focus adjustment state of the photographing lens based on these results. Detection method.