JPS6236207B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a focus detection device.

For example, Japanese Patent Application Publication No. 50-39543 (Japanese Patent Application No. 49-68068)
The focus detection device described in No. 1) forms an optical image of an object on a pair of photoelectric element arrays, calculates the difference in the photoelectric output of the photoelectric elements at corresponding positions on both photoelectric element arrays, and calculates the difference between the two photoelectric element arrays. A correlation output is obtained as the sum of absolute values, and the in-focus state of the objective lens is detected from the minimum value of the correlation output. In addition, as a method for detecting the minimum value of correlation output,
There is a method of scanning one side of the detection optical system mechanically, storing the value of the maximum extreme value corresponding to the minimum value, and performing a second scan using this value as a threshold. By obtaining the value for the extreme value,
The distance to the focal position of the objective lens is determined by determining the minimum value of the correlation output.

However, in this case, a mechanical scanning member is required, which not only complicates the mechanism but also takes time to respond.Also, when applied to TTL focus detection, the above scanning requires the use of an objective lens. Since focus cannot be detected unless the camera scans once from infinity to close range, this operation has the disadvantage of being extremely troublesome when viewing the viewfinder of a single-lens reflex camera.

The present applicant has already proposed Japanese Patent Application No. 54-5270 as a method to solve the above-mentioned drawbacks. In this publication, a spatial frequency component extraction circuit for detecting the phase difference of an optical image is provided, and the spatial frequency component extraction circuit is provided separately, and the output signal of the photoelectric element array is not the output signal of the spatial frequency component extraction circuit. A correlation detection section is provided which inputs a signal and outputs a standardized correlation output obtained by removing the influence of contrast from the correlation output, and when it is determined that the output related to the correlation detection section is close to in-focus, A method is disclosed in which a shift amount calculation result based on the phase difference of optical images is employed as an appropriate calculation result to perform highly accurate focus detection.

However, in the focus detection device described above, in order to detect the amount of deviation of the optical image with high precision, a spatial frequency component extraction circuit is provided, and in order to standardize the correlation output, the output signal of the spatial frequency component extraction circuit is Since a correlation detection section is provided which directly inputs the output signal of the photoelectric element array, the circuit structure of the correlation detection section becomes complicated and the circuit scale increases.

As described above, the present invention standardizes the correlation output so as not to depend on the sharpness (contrast) of the optical image with a simple circuit configuration without increasing the circuit scale of the focus detection device, and based on this standardizes the correlation output, without increasing the circuit scale of the focus detection device. It is an object of the present invention to provide a focus detection device that detects a state.

In order to standardize the correlation output, the present invention does not directly process the output signal of the photoelectric element array.
Since the output signal that has been processed once by the spatial frequency component extraction circuit is used, the circuit configuration for this purpose can be simplified.

For this purpose, in the embodiment of the present invention, the correlation output is determined as the sum of the absolute values of the differences between the outputs of the corresponding photoelectric conversion elements. Unlike the method of the previous application, in other words, since the output of the spatial frequency component extraction circuit includes the phase and amplitude, the position of the optical image can be calculated from the electrical signals of the two spatial frequency components derived from the pair of photoelectric conversion element arrays. Calculate the phase difference, and further (at the time of focusing, the phase difference becomes zero, but in order to prevent the phase difference from becoming zero even when the spectral image shifts by one cycle and generating a false focus signal, ) Using the above amplitudes, since the amplitudes become equal when in focus, we can calculate the absolute value of the difference in amplitudes, perform such calculations on multiple spatial frequency components, and synthesize them. It is used in place of the correlation output of the previous application. In order to remove the influence of contrast from this correlation output, a calculation is performed to add the amplitudes of the spatial frequency components, and this correlation output is normalized by the calculation result.

A detailed explanation of the embodiment will be given below.

In FIG. 1, a field lens 2 is provided on a fixed focal plane of an objective lens 1 or a plane conjugate thereto. In a camera, a film is placed on a fixed focal plane, so the field lens 2 shunts the optical path of the objective lens 1 and is provided in the shunted optical path. With respect to the re-imaging lenses 3 and 4, photoelectric element arrays 5 and 6 (referred to as first and second photoelectric element groups, respectively) are provided at positions conjugate with the field lens 2, that is, the fixed focal plane of the lens 1. ing. In this example, each array 5, 6 consists of eight photoelectric elements _P1 to _P8 , _P1 ' to _P8 '. When the objective lens 1 is focused on the object to be focused, the photoelectric element array 5,
The optical image of the object formed on 6 and the arrays 5 and 6
The positional relationship between the re-imaging lenses 3 and 4 and the arrays 5 and 6 is determined so that the positional relationship between and is the same. Therefore, in the focused state, the positionally corresponding photoelectric elements P ₁ and P ₁ ' of the pair of arrays 5, 6...
The intensities of light incident on P ₈ and P ₈ ′ are equal. Also, the image of the object formed by the objective lens 1 is transmitted to the field lens 2.
When formed in front of (front pin) array 5
The upper image moves downwards, while the image on array 6 moves upwards. Conversely, when the image by the objective lens 1 is formed behind the field lens 2 (rear focus), the images on the arrays 5 and 6 move in the opposite direction to the front focus.

The configuration of each photoelectric element in such an array and the arrangement relationship between the optical system and the array are not limited to those shown in FIG. It is completely arbitrary as long as it changes at least one of the positional relationship with the optical image on it and the positional relationship between the other array and the optical image on it. For example, the photoelectric elements in each array do not necessarily need to be arranged in a straight line, and the photoelectric elements may be arranged at certain intervals without being placed in close contact with each other.

The photoelectric element output of each photoelectric element P ₁ -P ₈ of the array 5 is linearly amplified or logarithmically amplified, respectively, to obtain the electrical output ₁ - ₈ associated with the photoelectric output.
The signals are output from the output terminals 5a to 5h of the array 5 as follows. The photoelectric outputs of the photoelectric elements P ₁ ′ to P ₈ ′ of the array 6 are similar, and the associated electrical outputs ₁ ′ to ₈ ′ are outputted from the output terminals 6a to 6h. In the following description, it is assumed that related electrical outputs ₁ to ₈ and ₁ ' to ₈ ' are logarithmically amplified photoelectric outputs, respectively.

Next, this related electrical output ₁ to ₈ , ₁ ' to
₈ ' processing will be explained. In FIG. 2, the spatial frequency component extraction circuit 7 extracts a first electrical signal V ₁ containing a large amount of information on the first spatial frequency component of the optical image on the array 5.
and a second electrical signal V ₂ containing a large amount of information on the second spatial frequency component with a spatial period of 1/2 of that period are extracted from the related electrical outputs ₁ to ₈ . The second spatial frequency component may have a spatial period different from the first spatial frequency component, and is not limited to the above example. When the optical image on the array 5 is displaced in the arrangement direction of the elements, this first electric signal V ₁ contains phase information φ ₁ that changes in a fixed relationship according to the displacement, and the magnitude of the extracted spatial frequency component. It is a vector quantity including size information _γ1 representing the size. 2nd electric signal
Similarly, V ₂ is a vector quantity including phase information φ ₂ and magnitude information γ ₂ . The other spatial frequency component extraction circuit 8 is identical to circuit 7 and extracts the first and second spatial frequency components of the optical image on the array 6 from the associated electrical outputs ₁ ' to ₈ ' of the array 6 and extracts them. First and second electrical signals V ₁ ′ and V ₂ ′, respectively, are generated. The first and second electrical signals V ₁ ′ and V ₂ ′ are vector quantities including phase information φ ₁ ′ and φ ₂ ′ and magnitude information γ ₁ ′ and γ ₂ ′, respectively.

The principle of this extraction circuit will be explained with reference to FIG.
In the same figure, the associated electrical outputs of photoelectric elements P ₁ to _{P 8}
The vectorization circuit 9 sequentially converts ₁ to ₈ into vectors exp(i2π×0/
8 p), exp(i2π×1/8p)…exp(i2π×7/8p)
is multiplied and converted to a vector. Addition circuit 10 adds the outputs of vectorization circuit 9. Therefore, the output Vp of the adder circuit 10 is as follows.

The output V ₁ of the adder circuit 10 when p=1 is a vector quantity containing a lot of information on the spatial frequency component of the optical image whose spatial period is the length d in the arrangement direction of the photoelectric elements P ₁ to _{P 8} of the array 5. Similarly, by setting p=2 and 3, the outputs V ₂ and V ₃ of the adder circuit 10 become vector quantities containing a lot of information on spatial frequency components whose spatial periods are d/2 and d/3, respectively. .

Generalizing the above, the related electrical output ₁ ~ _N
is sequentially multiplied by a vector with a phase shift of 2π×P/N by the vectorization circuit 9, and the results are added by the addition circuit 10. When P=1, 2, 3... The length of the element in the array direction, 1/2 of that,
A vector quantity containing a large amount of information on spatial frequency components with a spatial period of 1/3... is obtained.

Referring again to FIG. 2, summing circuit 12 sums the associated electrical outputs ₁ through ₈ to produce a scalar output γ ₀ representing the total amount of light incident on array 5. Similarly, the summing circuit 13 is connected to the associated electrical output of the array 6.
₁ ' to ₈ ' are added to produce a scalar output γ ₀ ' representing the total amount of light incident on the array 6. The subtraction circuits 14 and 15 calculate the difference between the first electrical signals V ₁ and V ₁ ' representing the first spatial frequency component and the difference between the second electrical signals V ₂ and V ₂ ' representing the second spatial frequency component, respectively. Then, the subtraction circuit 16 calculates the difference between the scalar outputs γ ₀ and γ ₀ '. Circuits 17 and 18 are each subtraction circuit 1
Absolute values of the vector outputs V ₁ -V ₁ ′, V ₂ -V ₂ ′ of 4 and 15, that is, the magnitude of the vector |V ₁ -V ₁ ′|, |V ₂
―V ₂ ′|

The absolute value circuit 19 determines the absolute value of the scalar output γ ₀ -γ ₀ ' of the subtraction circuit 16. Addition circuit 20
adds the outputs of the circuits 17, 18, and 19 to generate the output |V ₁ −V ₁ ′|+|V ₂ −V ₂ ′|+|γ ₀ −γ ₀ ′|. On the other hand, circuits 21, 22, 23, 24
are the absolute values of the first and second electrical signal outputs V ₁ V ₁ ′ and V ₂ V ₂ ′, respectively, that is, the magnitude of the vector |V ₁ |=γ ₁
Find |V ₂ |=γ ₂ , |V ₁ ′|=γ ₁ ′ and |V ₂ ′|=γ ₂ ′. The adder circuit 25 receives the output γ of the circuits 21 to 24.
₁ , γ ₂ , γ ₁ ′, γ ₂ ′ are added.

The above outputs |V ₁ −V ₁ ′|, |V ₂ −V ₂ ′|, |γ ₀
−γ ₀ ′| is at a minimum, ideally zero, when in focus, and increases as it deviates from there, so that it is correlated with the focal position of the objective lens 1. However, each of these correlation outputs is The sharpness of the image also depends. That is, each correlation output |V ₁ −V ₁ ′|, |V ₂ −
V ₂ ′|, |γ ₀ −γ ₀ ′| change depending on both the amount of deviation from focus and the sharpness of the optical image.

On the other hand, the outputs γ ₁ , γ ₂ , γ ₁ ′, γ ₂ ′ are also the above-mentioned outputs |V ₁ −V ₁ ′|, |V ₂ −V ₂ ′|, |γ ₀ −γ ₀ ′|
In almost the same way, it depends on the optical image clarity. Therefore, when the output of the adder circuit 20 is divided by the output of the adder circuit 25 by the divider circuit 26, in other words, the correlation output |V ₁ −V ₁ ′|+|V ₂ −V ₂ ′|+|γ ₀ − When dividing γ ₀ ′| by the standard factor (γ ₁ + γ ₂ + γ ₁ ′ + γ ₂ ′), we get
A standardized correlation output T that is almost independent of the sharpness of the optical image is obtained.

In this example, _the normalized correlation output T is expressed as T= ₍ |V ₁ −V ₁ ′|+|V _{2 −V 2 ′} | ₂ +
γ ₂ ′) However, in the present invention, the normalized correlation output T is not limited to this, and can be expressed as |V ₁ −V ₁ ′|, |V ₂ −
V ₂ '| is a correlation output based on the first and second electrical signals that contain many first and second spatial frequency components, respectively, so the normalized correlation output T is obtained from either one of these and the standardization factor for it. You can ask for it.

For example, T=|V ₁ −V ₁ ′|/(γ ₁ +γ ₁ ′), T
= |V ₂ −V ₂ ′|/(γ ₂ +γ ₂ ′). Also,
The correlation may be based on spatial frequency components other than the first and second spatial frequency components. Calculating the normalized phase correlation output based on one specific spatial frequency component in this way has the advantage of greatly simplifying the circuit configuration, but calculating the normalized phase correlation output based on one specific spatial frequency component has the advantage that the circuit configuration is extremely simple. There are the following drawbacks compared to the normalized correlation output obtained by

If only a correlation output based on one spatial frequency component is used, then for an optical image that happens to contain no or very little of that spatial frequency component,
However, by using correlation outputs related to a plurality of spatial frequency components as in this embodiment, the above disadvantage can be avoided, and correlation outputs can be obtained for almost any optical image. I can do it. Further, the correlation output |V ₁ −V ₁ ′| regarding the first spatial frequency increases as it deviates from the focused state, but if the light image on array 5 and the light image on array 6 are in the focused state If there is a relative shift by exactly the spatial period d, a troublesome situation arises in that the correlation output |V ₁ −V ₁ '| again becomes a value close to zero. The same goes for the correlation output |V ₂ −V ₂ ′| regarding the second spatial frequency component,
If both optical images are relatively shifted by the spatial period d/2, the value will become close to zero again. Therefore,
If only the correlation output |V ₁ −V ₁ ′| or |V ₂ −V ₂ ′| is used, there is a risk of incorrect focus detection. However, as mentioned above, the correlation output |γ ₀ −γ ₀ ′| is the absolute value of the difference in the total amount of light incident on each array, so it almost never becomes zero except at the focused point, and this output is easy to obtain. For example, T=(|V ₁ −V ₁ ′|+|γ ₀ −γ ₀ ′|)/(γ ₁
+γ ₁ ′), the correlation output based on the spatial frequency component and the correlation output based on the total light amount |γ ₀ −γ ₀ ′ |
It is preferable to avoid the above-mentioned erroneous focus detection.

Further, when obtaining a normalized correlation output from a plurality of spatial frequency components, normalization may be performed as follows.
T=|V ₁ −V ₁ ′|/(γ ₁ +γ ₁ ′)+{|V ₂ −V ₂ ′|
+|γ ₀ −γ ₀ ′|||}/(γ ₂ +γ ₂ ′) Using this formula, the total light amount correlation output |γ ₀ −γ ₀ ′|
The correlation output of the second spatial frequency component |V ₂ −V ₂ ′| was added to the correlation output of the first spatial frequency component |V ₁ −
It can be added to V ₁ ′|, it can be added to both, or it can be added to
It may also be an independent term, as in equation (2).

Further, when obtaining a normalized correlation output based on a plurality of pieces of information, weights k and h may be attached to the correlation output for each piece of information as described below.

T=k ₁ |V ₁ −V ₁ ′|+k ₂ |V ₂ −V ₂ ′|+k ₀ |γ ₀ −γ ₀ ′|/h ₁ (γ ₁ +γ ₁ ′)+h ₂ (γ ₂ −
γ ₂ ′) (1) or T = (k ₁ |V ₁ −V ₁ ′|)/(γ ₁ +γ ₁ ′)+k ₂ |V ₂ −V ₂ ′|/(γ ₂ +γ ₂ ′)+k ₀ |γ ₀ −γ ₀ ′ | (2) Since the outputs γ ₀ and γ ₀ ′ are related to the total amount of incident light of each array, the other outputs V ₁ , V ₁ ′, V ₂ ,
Since it is generally larger than V ₂ ′, γ ₁ , γ ₁ ′, γ ₂ , and γ ₂ ′, it is preferable to select the weighting coefficient k ₀ to be smaller than the other weighting coefficients.

Figure 4 shows a specific circuit example of the block diagram in Figure 2.
This will be explained with reference to FIG.

In FIG. 4 showing a specific circuit example of arrays 5 and 6, photodiodes P ₁ to _{P 8} of arrays 5 and 6,
The photocurrent of P ₁ ′ to P ₈ ′ flows through the operational amplifier and its feedback transistor. Logarithmic conversion circuit 27 consisting of a diode
a to 27h, 28a to 28h are the associated electrical outputs ₁ to ₈ proportional to the logarithm of the incident light intensity;
Converted from ₁ ′ to ₈ ′. Note that the feedback transistors and diodes of the logarithmic conversion circuits 27b to 27h and 28a to 28h are not shown in the figure. The circuit 29 applies feedback so that the average value of the related electrical outputs ₁ to ₈ and ₁ ' to ₈ ' becomes zero. Setting this average value to zero is to reduce the influence of errors in the vector values multiplied by the vectorization circuit, specifically errors such as the input resistance of the differential amplifiers 30 to 37 in FIG. be.

Next, in FIG. 5, terminals 5a to 5h, 6a to
6h are terminals 5a to 5 with the same symbols in FIG. 4, respectively.
h, connected to 6a to 6h. The vectoring circuit vectorizes the associated electrical outputs ₁ to ₈ , ₁ ' to ₈ '.
It multiplies exp(i2π×0/8) to exp(i2π×7/8) in the form of its x and y components. Differential amplifier 30
denotes the x component of the above vector as the associated electrical output
₁ to ₈ are multiplied and added, and the value of each input resistance is proportional to the reciprocal of the x component to be multiplied. Thus, the output of the differential amplifier 30 is the first electrical signal related to the spatial frequency component of the spatial period d.
It becomes the x component of V ₁ .

The differential amplifier 31 multiplies the related electrical outputs ₁ to ₈ by the y component of the vector described above and adds them. This addition output corresponds to the y component of the first electrical signal _V1 . In addition, differential amplification signal devices 32 and 33
produce the x and y components of the first electrical output V ₁ ' from the associated electrical outputs ₁ ' to ₈ ' of the array 6 in exactly the same way as the amplifiers 30 and 31, respectively. The differential amplifiers 34 and 35 also provide a second electrical signal regarding a spatial frequency component with a spatial period of d/2 for the array 5.
The differential amplifiers 36 and 37 respectively output the x and y components of the second electric signal V _{2 '} for the array 6.

The multipliers 38, 40, 42, 44 multiply the outputs of the differential amplifiers 30, 32, 34, 36 by the AC output cos wt from the circuit 46, and the multipliers 39, 41, 4
3, 45 are differential amplifiers 31, 33, 35, 37
The output of is multiplied by the AC output sin wt from the circuit 46. Adders 47, 48, 49, and 50 are multipliers 38, 39, 40, 41, 42, 43, and 44, respectively.
and the output of 45 are added. These adders 47,
The AC outputs of 48, 49, and 50 correspond to the first electric signals V ₁ , V ₁ ', and the second electric signals V ₂ , V ₂ ', respectively, and their positions correspond to the phases φ ₁ , φ ₁ ', φ ₂ , φ ₂ ′, and their amplitudes are the above absolute values γ ₁ , γ ₁ ′, γ
₂ , γ ₂ '.

In this way, the circuits 30, 31, 34, shown in FIG.
35, 38, 39, 42, 43, 46, 47, 4
9, the extraction circuit 7 of FIG. 2 is replaced with circuits 32, 33, 36, 37, 40, 41, 44, 4 shown in FIG.
5, 46, 48, and 50 constitute the extraction circuit 8 of FIG. 2, respectively.

The differential amplifier 51 has one input terminal connected to the terminal 5.
The other input terminal is connected to eight parallel resistors 52 connected to terminals a to 5h, and the other input terminal is connected to eight parallel resistors 53 connected to terminals 6a to 6h.

This amplifier 51 and a pair of eight parallel resistors 52 and 53 constitute circuits 12, 13, and 16 in FIG. 2, respectively. The output of the amplifier 51 becomes γ ₀ −γ ₀ '.

The differential amplifiers 54 and 55 are the subtraction circuit 1 in FIG.
4 and 15, and the subtraction signals V ₁ −V ₁ ′ and V ₂ −
Outputs V ₂ ′.

The rectifying and smoothing circuits 56, 57, and 58 rectify and smooth the outputs of the amplifiers 54, 55, and 51, respectively, and produce correlation outputs |V ₁ −V ₁ ′|, |V ₂ −V ₂ ′|, |γ ₀ −γ
Create ₀ ′ |

The outputs of the rectifying and smoothing circuits 56, 57, and 58 are resistors.
The weights k ₁ , k ₂ , k ₀ are multiplied by R ₁ , R ₂ , R ₃ and added at the connection point 59 . Thus, this addition output corresponds to the output of the addition circuit 20, k ₁ |V ₁ −V ₁ '|
+k ₂ |V ₂ −V ₂ ′|+k ₀ |γ ₀ −γ ₀ ′|.

The rectifying and smoothing circuits 61, 62, 63, and 64 rectify and smooth the electrical signals V ₁ , V ₁ ′, V ₂ , and V ₂ ′, respectively, and output γ ₁ ,
Create γ ₁ ′, γ ₂ , and γ ₂ ′. These outputs γ ₁ , γ
₁ ', γ ₂ , γ ₂ ' are added at connection point 65 after being weighted by resistors R ₄ to _{R 7} . Therefore, h ₁ (γ ₁ +γ ₁ ′)+h ₂ (γ ₂ +γ ₂ ′) is generated at the lever.

The logarithm circuits 64, 65 and the differential amplifier circuit 66 constitute the division circuit 26 in FIG. The output of the intensifier 64 is the logarithm of h ₁ (γ ₁ + γ ₁ ′) + h ₂ (γ ₂ + γ ₂ ′),
The output of the amplifier 65 is (k ₁ |V ₁ −V ₁ ′|+k ₂ |V ₂ −
Since it is the logarithm of V ₂ ′|+k ₀ |γ ₀ −γ ₀ ′|),
The output of the amplifier 66 is the logarithm of the normalized correlation output T in equation (1) above.

In addition to the normalized correlation output, the first electrical signal V ₁
and V ₁ ′ or from the second electric signals V ₂ and V ₂ ′, the distinction between in-focus, front focus, and back focus, and the amount of deviation from focus can be determined.
To be more specific, as described above, the phases φ ₁ , φ ₁ ', φ ₂ , and φ ₂ ' of the first and second electrical signals are determined by the position of the optical image on the array 5, and What is the relative relationship between the position of the optical image on the array 6 and the position of the optical image on the array 6 is determined by the focal position of the objective lens, so when measuring the phase difference φ ₁ - φ ₁ ' or φ ₂ - φ ₂ ', , its zero is in focus, the positive sign is, for example, front focus,
The negative sign represents the rear focus, and the absolute value of the phase difference represents the amount of deviation from focus.

In the above specific circuit example, vectors V ₁ , V ₁ ′,
V ₂ , V ₁ ′, and V ₂ ′ were each determined in the form of an AC signal, and the absolute value of each vector was determined through processing such as _{rectification .} , V ₂ ,
V ₂ ' may be determined in the form of its x and y components, and then the absolute value of the vector may be directly determined. For example, an amplifier 30 that is the x component and y component of the vector V ₁
The outputs of the vector V 1 ' and the outputs of the amplifier 31 are respectively V ₁ x and V ₁ y, and the outputs of the amplifiers 32 and 33, which are the x and y components of the vector V ₁ ', are V ₁ x' and V ₁ y', respectively. Then, γ ₁ and |V ₁ −V ₁ ′| are It is found by the calculation.

In addition, in the above, the related electrical output was a logarithmically amplified photoelectric output, but if the related electrical output is a linear amplified photoelectric output,
Since |γ ₀ −γ ₀ ′| changes according to changes in the incident light intensity, |γ ₀ −γ ₀ ′| itself is also normalized, and |γ
₀ −γ ₀ ′|/(γ ₀ −γ ₀ ′) in the above equations |γ ₀
It is recommended to use it instead of −γ ₀ ′|.

The focus detection device of the present invention can share many of the configurations with a focus detection device that detects focus from the phase difference between electrical signals containing specific spatial frequency components of an optical image on a pair of photoelectric element arrays. It can be easily combined with a focus detection device, thereby enabling highly accurate focus detection.

Correlation outputs related to spatial frequency components and their standard factor outputs can share many generation circuits, so
The overall circuit configuration is simplified.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining the principle of the focus detection device, Fig. 2 is a block diagram showing an embodiment of a circuit for processing signals of the focus detection device according to the present invention, and Fig. 3 is the same as Fig. 2. The block diagrams of the spatial frequency component extraction circuit shown in FIGS. 4 and 5 are circuit diagrams showing specific circuit configurations of the embodiment shown in FIG. Explanation of symbols of main parts, 5, 6...Photoelectric element array, 7, 8...Spatial frequency component extraction circuit, 1
2, 13... Addition circuit, 14, 15... Subtraction circuit, 16... Subtraction circuit, 17, 18... Absolute value circuit, 19... Absolute value circuit, 20... Addition circuit, 2
1 to 24...absolute value circuit, 25...addition circuit, 2
6...Division circuit.

Claims (1)

[Claims] 1. An image of substantially the same object is projected onto a first photoelectric element group consisting of a plurality of photoelectric elements arranged in a certain direction and a similar second photoelectric element group, respectively, At least one of the relative position between the first photoelectric element group and the optical image thereon and the relative position between the second photoelectric element group and the optical image thereon is changed in accordance with a change in the focal position of the objective lens. and detects the focused state of the objective lens from the relationship between the two relative positions, which obtains phase information of at least one spatial frequency component in the optical image on the first photoelectric element group from the output of the first photoelectric element group. , a first spatial frequency component extraction circuit that creates an electrical signal representing magnitude information, and an electrical signal representing phase information and magnitude information of the same spatial frequency component as the above spatial frequency component from the output of the second photoelectric element group. a second spatial frequency component extraction circuit to be created; and inputting electric signals from both the first spatial frequency component extraction circuit and the second spatial frequency component extraction circuit,
a correlation circuit that calculates the absolute value of the difference between the electric signals; a standard factor circuit that calculates the sum of the absolute values of the respective electric signals; A focus detection device comprising: means for creating a standardized correlation output that does not depend on the sharpness of an image, and detecting a focus state of an objective lens based on the output of the means. 2. In the device according to claim 1,
The correlation circuit outputs a signal representing the absolute value of the difference between a signal representing the total amount of light incident on the first photoelectric element group and a signal representing the total amount of light incident on the second photoelectric element group. A focus detection device comprising: 3. In the device according to claim 1 or 2, each spatial frequency component extraction circuit has at least a first and second spatial frequency component extracting circuit representing a first spatial frequency component and a second spatial frequency component, respectively.
A focus detection device that generates a second electrical signal. 4. In the device according to claim 3,
The correlation circuit generates an output obtained by taking the absolute value of the difference between the first electrical signals from each spatial frequency component extraction circuit and adding the absolute value of the difference between the second electrical signals from each spatial frequency component extraction circuit, The standard factor circuit is
generating an output of the sum of the absolute values of the first and second electrical signals from each spatial frequency component extraction circuit, the apparatus further including a division circuit for dividing the output of the correlation circuit by the output of the standardization factor circuit. A focus detection device characterized by: 5. In the device according to claim 3,
The correlation circuit represents the absolute value of the difference between a first absolute value signal representing the absolute value of the difference between the first electrical signal from each spatial frequency component extraction circuit and a second electrical signal from each spatial frequency component extraction circuit. A second absolute value signal is formed, and the standard factor circuit generates a first standard factor signal representing the sum of the absolute values of the first electric signals from each spatial frequency component extraction circuit, and a first standard factor signal representing the sum of the absolute values of the first electric signals from each spatial frequency component extraction circuit. a second signal representing the sum of absolute values of the second electric signal;
and the apparatus further includes circuitry for dividing the first absolute value signal by the first normalizing factor signal, dividing the second absolute value signal by the second normalizing factor signal, and adding the two. Features a focus detection device. 6. In the device according to claim 1,
The correlation circuit outputs an absolute value signal in which each absolute value output is given a predetermined weight, and the standard factor circuit outputs a standard factor signal in which each sum output is given a predetermined weight. Focus detection device.