JP3491303B2 - Focus detection device and focus detection method - Google Patents

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 and a focus detecting method for detecting a photographing distance to a subject or a defocus amount of a photographing lens.

[0002]

2. Description of the Related Art An autofocus camera has a focus detection area in the center of a photographic screen, and automatically drives a photographic lens so that an object captured in this focus detection area is in focus. Therefore, the photographer can focus the photographing lens on the main subject by capturing the subject to be photographed (hereinafter referred to as the main subject) in the focus detection area in the photographing screen.

A pair of light fluxes from a subject are guided onto a pair of image sensors to form a pair of subject images, and the relative shift amount between the pair of subject images is calculated based on image signals output from these image sensors. 2. Description of the Related Art There is known a phase difference detection type focus detection device that calculates and calculates information regarding focus adjustment of a photographing lens.

FIG. 7 shows the structure of a focus detection device of the phase difference detection type. The light flux from the subject that has entered through the area 101 of the objective lens 100 reaches the image sensor A through the field mask 200, the field lens 300, the aperture opening 401, and the re-imaging lens 501, and the subject on the image sensor A. Form an image. Similarly, the light flux from the subject that has entered through the area 102 of the objective lens 100 reaches the image sensor B through the field mask 200, the field lens 300, the aperture opening 402 and the re-imaging lens 502, and the image sensor B. A subject image is formed on top.

The pair of subject images formed on the pair of image sensors A and B are distant from each other in a so-called front focus state in which the objective lens 100 forms a sharp image of the subject before the planned focal plane, and is reversed. In addition, a sharp image of the subject is formed after the planned focal plane, so that they are close to each other in the so-called rear focus state, and a sharp image of the subject is formed just on the planned focal plane. Match each other. Therefore, the focus adjustment state of the objective lens 100 is obtained by photoelectrically converting the pair of subject images by the image sensors A and B, converting them into electric signals, and processing these signals to obtain the relative position of the pair of subject images. , Here, the amount away from the focused state and its direction, that is, defocus can be obtained. In the focus detection area, the image sensors A and B are used by the re-imaging lens 50.
It is a portion projected by 1, 502 and overlapping in the vicinity of the planned focal plane.

Next, a method of calculating the defocus amount will be described. The image sensors A and B each include a plurality of photoelectric conversion elements, and as shown in FIGS. 8A and 8B, a plurality of photoelectric conversion outputs a1, a2, ..., An, b1, b2.
.., bn are output. Then, the correlation calculation is performed while relatively shifting each data string by a predetermined amount L of data. Specifically, the correlation amount C (L) is calculated by the following equation.

[Equation 1] Here, L is an integer corresponding to the shift amount of the data string as described above, and the first term k and the last term r may be changed depending on the shift amount L. Of the correlation amounts C (L) thus obtained, the shift amount giving the minimum correlation amount is multiplied by a constant determined by the pitch width of the photoelectric conversion element of the optical system and the image sensor shown in FIG. It is the focus amount.

However, the correlation amount C (L) is shown in FIG.
As shown in (c), it is a discrete value, and the minimum unit of defocus amount that can be detected is limited by the pitch width of the photoelectric conversion elements of the image sensors A and B. Therefore, a method has been proposed in which a minimal value Cex is newly calculated by performing an interpolation operation from the discrete correlation amount C (L) to perform close focus detection (see Japanese Patent Laid-Open No. 60-37513). . As shown in FIG. 9, this is because the correlation amount C (0), which is the minimum value, and the correlation amount C in the shift amounts on both sides thereof.
(1), C (-1) is used to calculate the minimum value C
The shift amount Fm and the defocus amount DF that give ex are obtained by the following equations.

DF = Kf * Fm Fm = L + DL / E DL = {C (-1) -C (1)} / 2 Cex = C (0)-| DL | E = MAX [{C (1)- C (0)}, {C (-1)-
C (0)}] where MAX {Ca, Cb} means selecting the larger of Ca and Cb, and Kf is the pitch width of the photoelectric conversion element of the optical system and image sensor shown in FIG. Is a constant determined by.

It is necessary to determine whether the defocus amount thus obtained truly indicates the defocus amount or whether it is due to fluctuations in the correlation amount due to noise or the like. That is, the defocus amount satisfying the following condition is set as a reliable defocus amount.

## EQU3 ## E> E1 and Cex / E <G1 where E1 and G1 are predetermined values. In the above equation, E
Is a value depending on the contrast of the subject, and the larger the value, the higher the contrast and the higher the reliability of the defocus amount. Cex / E mainly depends on the degree of coincidence of the images, and the closer to 0, the higher the reliability of the defocus amount. Then, the objective lens 100 is driven and focused based on the defocus amount DF determined to be reliable.

By the way, a charge storage type photoelectric conversion element such as a CCD is mainly used as a photoelectric conversion element constituting an image sensor. However, if the charge storage time of these photoelectric conversion elements is not appropriate, the contrast becomes low, so that high accuracy cannot be obtained or focus detection becomes impossible. In such a case, it is necessary to re-accumulate again with an appropriate charge accumulation time, but if the accumulation time is judged to be proper based on the calculation result after calculation,
It takes a lot of time to complete the focus detection.

In order to solve such a problem and maintain high focus detection accuracy and perform focus detection in a short time, the validity of the image signal accumulated before the calculation is judged and it is judged as invalid. In that case, it is conceivable that the focus detection calculation is not performed using those image signals, and the charge is stored again. The following two methods have been proposed for determining the validity of this image signal. One is to focus on the fact that the effectiveness depends on the contrast of the subject, calculate the image contrast of the subject before performing the correlation calculation, and perform the correlation calculation only when this value is larger than a predetermined value. Is. The other is a method of detecting the peak value in the output signal of the image sensor before performing the correlation calculation and performing the correlation calculation only when this value is larger than a predetermined value.

[0011]

By the way, there are cases where a reliable defocus amount can be calculated if the peak value is large even if the contrast value is small. For example, in FIG.
When an image signal having a low contrast as shown in (a) is obtained, the image signal is subjected to a filter process as disclosed in Japanese Patent Laid-Open No. 59-142506 to extract only low frequency components, When a new image signal as shown in FIG. 10B is generated, the image signal initially determined to have a small contrast value and being invalid becomes effective.
Further, as shown in FIG. 11, even if the peak value is small, if the contrast value is large, it may be possible to calculate a reliable defocus amount. As described above, the method of determining the validity of the image signal described above has a problem that the possibility of calculating a reliable defocus amount is limited.

An object of the present invention is to accurately judge the validity of an image signal in order to carry out highly accurate focus detection in a short time.

[0013]

When the inventions of claims 1 and 2 are described in association with FIG. 1 showing the configuration of the first embodiment, the invention of claim 1 forms an image by an optical system 2. A pair of image sensors 3 that output image signals corresponding to the light intensity distribution of the captured object image, and a focus that calculates information regarding focus adjustment of the taking lens based on the pair of image signals output from the pair of image sensors 3. It is applied to a focus detection device provided with the adjustment information calculation means 7. Then, the peak detection means 4 for detecting the peak value of the image signal output from the image sensor 3, the contrast detection means 5 for detecting the contrast value of the image signal output from the image sensor 3, and the peak detection means 4 are detected. Based on the peak value thus obtained and the contrast value detected by the contrast detection means 5, the focus adjustment information calculation means 7
The calculation determining means 6 determines whether or not to calculate the information regarding the focus adjustment by the calculation determining means 6 before calculating the information regarding the focus adjustment by the focus adjustment information calculating means 7. Whether or not to perform the calculation is determined, and when the determination to perform the calculation is made, the focus adjustment information calculation means 7 calculates the information regarding the focus adjustment. This achieves the above object. Further, in the focus detecting device according to claim 2, the peak value detected by the peak detecting means 4 and the contrast value detected by the contrast detecting means 5 are weighted and summed by the calculation determining means 6, and the sum thereof is obtained. When the value is equal to or larger than the predetermined value, the focus adjustment information calculation means 7 determines whether the focus adjustment information is calculated. When the inventions of claims 3 to 5 are described in association with FIG. 3 showing the configuration of the second embodiment, the invention of claim 3 comprises a plurality of photoelectric conversion elements, and an object imaged by the optical system 2 is formed. A pair of image sensors 3 that outputs an image signal corresponding to the light intensity distribution of the image, and a focus adjustment information calculation that calculates information regarding focus adjustment of the taking lens based on the pair of image signals output from the pair of image sensors 3. Means 7 and a focus detection device. Then, peak detecting means 4 for detecting the peak value of the image signal output from the image sensor 3, and contrast detecting means 5 for detecting the contrast value of the image signal output from the image sensor 3,
Overflow detection means 10 for detecting the number of photoelectric conversion elements whose output signal level is a predetermined value or more among a plurality of photoelectric conversion elements, and a peak value detected by the peak detection means 4,
Calculation determination for deciding whether or not the focus adjustment information calculation unit 7 calculates the information regarding focus adjustment based on the contrast value detected by the contrast detection unit 5 and the number of photoelectric conversion elements detected by the overflow detection unit 10. Before calculating the information regarding the focus adjustment by the focus adjustment information calculating means 7, the calculation determining means 6A determines whether or not to calculate the information regarding the focus adjustment, and the calculation is determined. In this case, the focus adjustment information calculation means 7 calculates the information regarding focus adjustment. This achieves the above object. In the focus detection device according to claim 4, the calculation determining means 6A causes
The peak value detected by the peak detection means 4, the contrast value detected by the contrast detection means 5, and the number of photoelectric conversion elements detected by the overflow detection means 10 are respectively weighted, and the weighted peak value and the weighted contrast are weighted. And the value obtained by subtracting the number of weighted photoelectric conversion elements from the total value is greater than or equal to a predetermined value, the focus adjustment information calculation unit 7 determines whether focus adjustment information should be calculated. . Further, in the focus detecting device according to claim 5, the calculation determining means 6A weights the peak value detected by the peak detecting means 4 and the contrast value detected by the contrast detecting means 5 and sums them, and sums them. When the value is greater than or equal to the first predetermined value and the number of photoelectric conversion elements detected by the overflow detection unit 10 is less than or equal to the second predetermined value, the focus adjustment information calculation unit 7 determines to execute focus adjustment information calculation. It was done like this. According to a sixth aspect of the focus detection apparatus, a photographing distance to a subject is calculated as information regarding focus adjustment of the photographing lens. According to a seventh aspect of the focus detection apparatus, the defocus amount of the photographing lens is calculated as the information regarding the focus adjustment of the photographing lens. The invention according to claim 8 is applied to a focus detection method for calculating information regarding focus adjustment of a photographing lens based on a pair of image signals corresponding to light intensity distributions of a subject image output from a pair of image sensors. Before calculating the information on the focus, the peak value and the contrast value of the image signal output from the image sensor are detected, and whether or not the information on the focus adjustment is calculated based on the peak value and the contrast value is determined. The above object is achieved by performing a calculation of information relating to focus adjustment when the decision is made to make the calculation. The focus detecting method according to claim 9, wherein the peak value and the contrast value of the image signal are weighted and summed, and when the total value is equal to or more than a predetermined value, execution of the focus adjustment information is determined. Is. According to a tenth aspect of the present invention, a focus for calculating information regarding focus adjustment of the photographing lens based on a pair of image signals corresponding to a light intensity distribution of a subject image output from a pair of image sensors including a plurality of photoelectric conversion elements. Applied to the detection method,
Before calculating information regarding focus adjustment, the peak value and the contrast value of the image signal output from the image sensor are detected, and the number of photoelectric conversion elements whose output signal level is a predetermined value or more among the plurality of photoelectric conversion elements. Detect
Based on the detected peak value, contrast value and the number of photoelectric conversion elements, it is determined whether or not the information regarding the focus adjustment is to be calculated, and when the operation is determined, the information regarding the focus adjustment is calculated. By doing so, the above object is achieved. The focus detection method according to claim 11, wherein the peak value, the contrast value, and the number of photoelectric conversion elements are respectively weighted, the weighted peak value and the weighted contrast value are summed, and the weighted photoelectric conversion is performed from the total value. When the value obtained by subtracting the number of elements is equal to or greater than a predetermined value, execution of focus adjustment information is determined. In the focus detection method according to claim 12, the peak value and the contrast value are weighted and added together, and the total value is equal to or larger than a first predetermined value and the number of photoelectric conversion elements is equal to or smaller than a second predetermined value. In this case, the calculation execution of the focus adjustment information is decided. In the focus detection method according to the thirteenth aspect, a shooting distance to a subject is calculated as information regarding focus adjustment of the shooting lens. According to the focus detecting method of the fourteenth aspect, the defocus amount of the photographing lens is calculated as the information regarding the focus adjustment of the photographing lens.

[0014]

Before calculating the information regarding the focus adjustment, it is determined whether or not the information regarding the focus adjustment is calculated based on the peak value and the contrast value of the image signal output from the image sensor 3, and the calculation is performed. When the determination is made, the calculation of the information regarding the focus adjustment of the taking lens is executed. For example, the peak value and the contrast value are respectively weighted and added together, and when the total value is equal to or larger than a predetermined value, execution of focus adjustment information is determined. This allows
The validity of the image signal can be accurately determined, and highly accurate focus detection can be performed in a short time.

Before calculating the information regarding the focus adjustment, the information regarding the focus adjustment is calculated based on the peak value and the contrast value of the image signal output from the image sensor 3 and the number of photoelectric conversion elements whose output signal level is a predetermined value or more. Whether or not the calculation is performed is determined, and when the calculation is determined, the calculation of the information regarding the focus adjustment of the photographing lens is performed. For example, the peak value, the contrast value, and the number of photoelectric conversion elements are respectively weighted, the weighted peak value and the weighted contrast value are summed, and the value obtained by subtracting the number of weighted photoelectric conversion elements from the total value is predetermined. When the value is equal to or larger than the value, it is decided to execute the calculation of the focus adjustment information. Alternatively, the peak value and the contrast value are weighted and added together, and when the total value is equal to or larger than the first predetermined value and the number of photoelectric conversion elements is equal to or smaller than the second predetermined value, the focus adjustment information Determines the operation execution. As a result, even though both the peak value and the contrast value of the image signal are sufficiently high, the number of overflowing photoelectric conversion elements is large and normal focus detection cannot be performed, and the focus detection operation is repeated many times. Is prevented.

Incidentally, in the section of means and action for solving the above-mentioned problems for explaining the constitution of the present invention, the drawings of the embodiments are used in order to make the present invention easy to understand. It is not limited to.

[0017]

【Example】

First Embodiment FIG. 1 is a functional block diagram showing the configuration of the first embodiment. The focus detection optical system 2 has a field mask, a field lens, a diaphragm aperture, and a re-imaging lens as shown in FIG. 7, and guides a pair of light fluxes passing through different regions of the objective lens 1 to the image sensor 3. A subject image is formed on each image sensor. The peak value detecting unit 4 detects the peak value of the image signal output from the image sensor 3, and the contrast value detecting unit 5 detects the contrast value of the image signal output from the image sensor 3. The determination unit 6 is
Based on the peak value detected by the peak value detection unit 4 and the contrast value detected by the contrast value detection unit 5, it is determined whether or not the correlation calculation for focus detection is performed. When the determination unit 6 determines to execute the correlation calculation, the correlation calculation unit 7 performs the correlation calculation based on the image signal output from the image sensor 3 to calculate the defocus amount of the objective lens 1. The drive control unit 8 drives and controls the motor 9 based on the defocus amount calculated by the correlation calculation unit 7 to drive the objective lens 1 in focus.

The detection of the contrast value Ct in the contrast value detecting section 5 is performed by the following equation, for example.

[Equation 4] However, if | a (i) -a (i + 1) | <Sth2, | a (i) -a (i + 1) | = 0 is set to reduce the influence of noise. Here, Sth2 is a predetermined value,
For example, a value that is slightly larger than the dark current output of the image sensor is considered appropriate. Since the dark current depends on the storage time and temperature, Sth2 may be variable depending on the storage time and temperature. When high-frequency noise is included in the low-frequency image signal, the contrast value Ct can be calculated by the following equation, for example.

[Equation 5] Here, q is an integer of 2 or more.

The detection of the contrast value and the peak value described above may be performed based on the image signal output of either one of the pair of image sensors, or may be performed based on the output of both image signals.

The determination of whether or not the correlation calculation is performed in the determination unit 6 is performed by, for example, whether or not the following equation is satisfied.

[Mathematical formula-see original document] α * Ct + β * P ≧ Sth1 where P is the peak value detected by the peak value detection unit 4, α and β are coefficients for weighting Ct and P, and S
th1 is a certain predetermined value. When Expression 6 is satisfied, even if the peak value of the image signal detected by the image sensor 3 is low, the contrast value is sufficient to obtain a reliable defocus amount. Alternatively, even if the contrast value of the image signal is low, its peak value is sufficient to obtain a reliable defocus amount. Alternatively, both the peak value and the contrast value of the image signal are sufficient to obtain a reliable defocus amount. It is determined to be one of these, and the execution of the correlation calculation is determined. That is, the peak value P detected by the peak value detection unit 4
And the contrast value Ct detected by the contrast value detection unit 5 are weighted by α and β, respectively, and summed. If the total value is equal to or more than the predetermined value Sth1, execution of the correlation calculation is determined. On the other hand, when Expression 6 is not satisfied, both the peak value and the contrast value are low, it is determined that the correlation calculation cannot be executed, and the correlation calculation is not performed.

FIG. 2 is a flow chart showing the focus detecting operation of the first embodiment. The operation of the first embodiment will be described with reference to this flowchart. When the photographer half-presses a release button (not shown), the focus detection operation shown in FIG. 2 is started. First, in step S1, charge of the image sensor 3 is accumulated, and when the accumulation is completed, the process proceeds to step S2. In step S2, the peak value detector 4 detects the peak value of the image signal output from the image sensor 3, and in the subsequent step S3, the contrast value detector 5 detects the contrast value of the image signal output from the image sensor 3. To detect. In step S4, the determination unit 6 determines whether or not to perform the correlation calculation based on the above-described formula 6, and when the formula 6 is satisfied, the process proceeds to step S5, the correlation calculation unit 7 performs the correlation calculation, and the subsequent step In S6, the drive control unit 8 drives the objective lens 1 based on the defocus amount of the calculation result. On the other hand, step S4
If the equation 6 is not satisfied, steps S5 and S6
Skip to step S7, the correlation calculation based on the invalid image signal and the lens driving are omitted, and the focus detection time is shortened accordingly. In step S7, when the photographer releases the half-press, the focus detection operation ends, and otherwise, the process returns to step S1 and the above-described operation is repeated. In addition,
When starting again from the charge accumulation, the accumulation time is determined based on the peak value or the average value of the image signal detected this time.

Second Embodiment By the way, even if both the peak value and the contrast value of the image signal are high, normal focus detection cannot be performed if the number of photoelectric conversion elements causing overflow as shown in FIG. 5 is too large. Sometimes. In order to avoid such a problem, when determining the validity of the image signal, in addition to the peak value and the contrast value of the image signal, the number of photoelectric conversion elements causing overflow in the image sensor is considered. An example will be described. FIG. 3 is a functional block diagram showing the configuration of the second embodiment. The same elements as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and different points will be mainly described. The overflow element number detection unit 10 detects the number of photoelectric conversion elements that have overflowed among the plurality of photoelectric conversion elements that form the image sensor 3. The determination unit 6A performs a correlation calculation based on the peak value detected by the peak value detection unit 4, the contrast value detected by the contrast value detection unit 5, and the overflow element number detected by the overflow element number detection unit 10. Decide whether or not.

The determination of whether or not the correlation calculation is performed by the determination unit 6A is performed by, for example, whether or not the following equation is satisfied.

[Formula 7] α * Ct + β * P−γ * Ov ≧ Sth3 Or

[Expression 8] α * Ct + β * P ≧ Sth1 and Ov ≦ Sth4. Here, Ov is the number of photoelectric conversion elements that have overflowed the image sensor 3 detected by the overflow element number detection unit 10, γ is a coefficient for weighting Ov, and Sth3 and Sth4 are certain predetermined values.

FIG. 4 is a flow chart showing the focus detection operation of the second embodiment. The operation of the second embodiment will be described with reference to this flowchart. When the photographer half-presses a release button (not shown), the focus detection operation shown in FIG. 4 is started. First, in step S11, the charge of the image sensor 3 is accumulated, and when the accumulation is completed, the process proceeds to step S12. In step S12, the peak value detector 4 detects the peak value of the image signal output from the image sensor 3, and in the subsequent step S13, the contrast value detector 5 detects the contrast value of the image signal output from the image sensor 3. To detect. Further, in step S14, the number of overflow photoelectric conversion elements in the image sensor 2 is detected by the overflow element number detection unit 10. In step S15, the determination unit 6A determines whether or not to perform the correlation calculation based on the above-described formula 7. If the formula 7 is satisfied, the process proceeds to step S16, the correlation calculation unit 7 performs the correlation calculation, and the subsequent step S
At 17, the drive control unit 8 drives the objective lens 1 based on the defocus amount of the calculation result. On the other hand, step S1
If the formula 6 is not satisfied in step 5, step S16,
Step S17 is skipped and the process proceeds to step S18, in which the correlation calculation based on the invalid image signal and the lens driving are omitted, and the focus detection time is shortened accordingly. In step S18, when the photographer releases the half-press, the focus detection operation ends, and if not, the process returns to step S11 and the above-described operation is repeated. In the case of starting over from the charge accumulation, the accumulation time is determined based on the peak value or the average value of the image signal detected this time. In step S15, the validity of the image signal may be determined by the above-described mathematical expression 8.

By the way, in a focus detection apparatus having a plurality of focus detection areas such as multi-auto focus, the predetermined values such as Sth1 and Sth2 may be set for each area. For example, when the focus detection device has three detection areas as shown in FIG. 6, a difference in noise amount in an image signal due to a difference in focus detection range and a difference in optical performance between sensors are provided between the areas. , Illuminance unevenness due to the focus detection optical system. Therefore, by setting each predetermined value for each area, it is possible to appropriately correct the noise amount difference between the areas, the optical performance difference, the illuminance unevenness, and the like.

In each of the above-described embodiments, the focus detection device of the TTL phase difference detection system for detecting the focus adjustment state of the objective lens has been described as an example, but the focus of the passive system for detecting the photographing distance to the subject is described. The present invention can be applied to a detection device, and similar effects can be obtained.

In the configuration of the above embodiment, the image sensor 3 is an image sensor, the focus detection optical system 2 is an optical system, the correlation calculation unit 7 is a focus adjustment information calculation unit, and the peak value detection unit 4 is a peak detection unit. The contrast value detecting section 5 constitutes the contrast detecting means, the judging sections 6 and 6A constitute the calculation determining means, and the overflow element number detecting section 10 constitutes the overflow detecting means.

[0028]

According to the present invention as described above, according to the present invention, shooting
Before computing the information about the focusing of the shadow lens, the peak value of the image signal output from the image sensor and on the basis of the contrast value, to determine whether to perform the calculation of the information on focus adjustment, performs computation Where the decision was made
Information on the focus adjustment of the shooting lens
It For example, the peak value and the contrast value are respectively weighted and added together, and when the total value is equal to or larger than a predetermined value, execution of focus adjustment information is determined. This allows
The validity of the image signal can be accurately determined, and highly accurate focus detection can be performed in a short time. Also, for adjusting the focus of the shooting lens
Before calculating the information related to the information, whether to calculate the information related to the focus adjustment based on the peak value and the contrast value of the image signal output from the image sensor, and the number of photoelectric conversion elements whose output signal level is a predetermined value or more. Decide
And the focus of the shooting lens when a decision is made to perform the calculation.
Performs calculations of information about adjustments . For example, the peak value, the contrast value, and the number of photoelectric conversion elements are respectively weighted, the weighted peak value and the weighted contrast value are summed, and the value obtained by subtracting the number of weighted photoelectric conversion elements from the total value is predetermined. When the value is equal to or larger than the value, it is determined whether the focus adjustment information is calculated. Alternatively,
The peak value and the contrast value are weighted and added together, and the total value is equal to or greater than a first predetermined value, and
When the number of photoelectric conversion elements is equal to or less than the second predetermined value, the focus adjustment information is determined to be calculated. As a result, the validity of the image signal can be accurately determined, high-precision focus detection can be performed in a short time, and the peak value and the contrast value of the image signal are both sufficiently high, but overflow has occurred. Since the number of photoelectric conversion elements is large and normal focus detection cannot be performed, it is possible to prevent the focus detection operation from being repeated many times.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a configuration of a first embodiment.

FIG. 2 is a flowchart showing a focus detection operation of the first embodiment.

FIG. 3 is a functional block diagram showing a configuration of a second embodiment.

FIG. 4 is a flowchart showing a focus detection operation of the second embodiment.

FIG. 5 is a diagram showing an overflowed image signal.

FIG. 6 is an explanatory diagram of a focus detection device having three focus detection areas.

FIG. 7 is a diagram showing an optical system and an image sensor of a phase difference detection type focus detection device.

FIG. 8 is an explanatory diagram of correlation calculation.

FIG. 9 is an explanatory diagram of a correlation calculation.

FIG. 10 is a diagram showing an effect of filter processing.

FIG. 11 is a diagram showing an image signal having a small peak value but a large contrast value.

[Explanation of symbols]

1 Objective lens 2 Focus detection optical system 3 image sensor 4 Peak value detector 5 Contrast value detector 6,6A judgment part 7 Correlation calculator 8 Drive control unit 9 motors 10 Overflow element number detector

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-2-15218 (JP, A) JP-A-57-19703 (JP, A) JP-A-3-256016 (JP, A) JP-A-2- 64519 (JP, A) JP 63-30811 (JP, A) JP 62-86317 (JP, A) JP 63-262611 (JP, A) JP 4-145406 (JP, A) JP-A 61-186917 (JP, A) JP-A 2-53012 (JP, A) JP-A 60-29716 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 7/34 G03B 13/36

Claims (14)

(57) [Claims] 1. A pair of image sensors that output an image signal corresponding to a light intensity distribution of a subject image formed by an optical system, and a taking lens based on the pair of image signals output from the pair of image sensors. A focus detection device including focus adjustment information calculation means for calculating information regarding focus adjustment, peak detection means for detecting a peak value of an image signal output from the image sensor, and an image output from the image sensor. Contrast detection means for detecting the contrast value of the signal, based on the peak value detected by the peak detection means and the contrast value detected by the contrast detection means, of the information regarding focus adjustment by the focus adjustment information calculation means. and an arithmetic determining means for determining whether or not to perform an operation, the focus adjustment Information about focusing the information calculating means
Before calculating the
Decide whether or not to calculate the information to
If the focus adjustment information calculation means
A focus detection device characterized by executing calculation of information relating to adjustment . 2. The focus detection device according to claim 1, wherein the calculation determination unit weights the peak value detected by the peak detection unit and the contrast value detected by the contrast detection unit, respectively. A focus detection apparatus, characterized in that the focus adjustment information calculation means decides to perform calculation of the focus adjustment information when the total value is equal to or more than a predetermined value. 3. A pair of image sensors, each of which is composed of a plurality of photoelectric conversion elements and outputs an image signal corresponding to a light intensity distribution of a subject image formed by an optical system, and a pair of image sensors output from the pair of image sensors. In a focus detection device including a focus adjustment information calculation unit that calculates information regarding focus adjustment of a photographic lens based on the image signal of, a peak detection unit that detects a peak value of an image signal output from the image sensor, Contrast detection means for detecting the contrast value of the image signal output from the image sensor; overflow detection means for detecting the number of photoelectric conversion elements whose output signal level is a predetermined value or more among the plurality of photoelectric conversion elements; The peak value detected by the peak detection means, the peak value detected by the contrast detection means. Based on the photoelectric number conversion elements detected by the last value and the overflow detection unit, and an arithmetic determining means for determining whether to perform an operation of information on the focusing by the focus adjustment information calculating means, said focusing Information about focus adjustment by information calculation means
Before calculating the
Decide whether or not to calculate the information to
If the focus adjustment information calculation means
A focus detection device characterized by executing calculation of information relating to adjustment . 4. The focus detection device according to claim 3, wherein the calculation determination unit detects the peak value detected by the peak detection unit, the contrast value detected by the contrast detection unit, and the overflow detection unit. When the weighted peak value and the weighted contrast value are summed, the value obtained by subtracting the weighted photoelectric conversion element number from the total value is equal to or more than a predetermined value. A focus detection apparatus, characterized in that the focus adjustment information calculation means determines whether focus adjustment information is calculated. 5. The focus detection device according to claim 3, wherein the calculation determination unit weights the peak value detected by the peak detection unit and the contrast value detected by the contrast detection unit. If the total value is greater than or equal to the first predetermined value and the number of photoelectric conversion elements detected by the overflow detection unit is less than or equal to the second predetermined value, the focus adjustment information calculated by the focus adjustment information calculation unit is calculated. A focus detection device characterized by determining execution of calculation. 6. The focus detection device according to claim 1, wherein the information regarding the focus adjustment of the photographing lens is a photographing distance to a subject. 7. The focus detection device according to claim 1, wherein the information regarding focus adjustment of the photographing lens is a defocus amount of the photographing lens. 8. A focus detection method for calculating information on focus adjustment of a photographing lens based on a pair of image signals corresponding to light intensity distributions of a subject image output from a pair of image sensors, wherein Before the calculation, the peak value and the contrast value of the image signal output from the image sensor are detected, and based on the peak value and the contrast value, it is determined whether or not the information regarding the focus adjustment is calculated. And before the decision to perform the operation is made
A focus detection method characterized by executing calculation of information regarding focus adjustment . 9. The focus detection method according to claim 8, wherein the peak value and the contrast value of the image signal are weighted and added together, and when the total value is equal to or more than a predetermined value, the focus adjustment information A focus detection method characterized by determining execution of calculation. 10. A focus detection method for calculating information relating to focus adjustment of a photographing lens based on a pair of image signals corresponding to a light intensity distribution of a subject image output from a pair of image sensors composed of a plurality of photoelectric conversion elements. In, before calculating the information regarding the focus adjustment , while detecting the peak value and the contrast value of the image signal output from the image sensor, the output signal level among the plurality of photoelectric conversion elements is a predetermined value or more. of detecting the photoelectric number conversion element, it said detected peak value, on the basis of the contrast value and the number of the photoelectric conversion element to determine whether to perform an operation of information on the focusing, the operation
Of information on the focus adjustment when a decision is made to make
A focus detection method characterized by executing a calculation . 11. The focus detection method according to claim 10, wherein the peak value, the contrast value, and the number of photoelectric conversion elements are weighted, respectively, and the weighted peak value and the weighted contrast value are summed up. The focus detection method is characterized in that the calculation execution of the focus adjustment information is determined when a value obtained by subtracting the number of weighted photoelectric conversion elements from the total value is a predetermined value or more. 12. The focus detection method according to claim 10, wherein the peak value and the contrast value are weighted and added together, and the total value is equal to or greater than a first predetermined value, and the photoelectric conversion is performed. A focus detection method, wherein the execution of calculation of the focus adjustment information is determined when the number of elements is equal to or less than a second predetermined value. 13. The focus detection method according to claim 8, wherein the information regarding the focus adjustment of the photographing lens is a photographing distance to a subject. 14. The focus detection method according to claim 8, wherein the information regarding focus adjustment of the photographing lens is a defocus amount of the photographing lens.