JP2526884B2 - Focus detection device - Google Patents

Description

The present invention relates to a focus detection device such as a camera.

[Background of the Invention]

Conventionally, as a focus detection device for a TTL camera, a so-called pupil division method that detects a focus adjustment state of the photographing optical system from relative displacement amounts of a plurality of subject images generated by light beams coming from different areas of the pupil of the photographing optical system. Is known.

For example, Japanese Examined Patent Publication (Kokoku) No. 57-49841 discloses an automatic focus detection device of this type including a pair array of a lens array arranged near the primary image plane and a light receiving element array arranged immediately after the lens array. There is.

Further, in Japanese Patent Laid-Open No. 54-104859, there are a field lens arranged on the primary image plane and two re-imaging lenses for re-imaging the image formed on the primary image plane on the secondary image plane and a secondary image plane. An automatic focus detection device of this kind is disclosed which is composed of two image sensor arrays arranged above.

However, such a conventional pupil division type automatic focus detection device has the following drawbacks.

That is, in this type of automatic focus detection device, the optical system on the focus detection side specifies the pupil of the predetermined F number on the plane orthogonal to the predetermined position on the optical axis.
Even if the F-number of the exit pupil is larger than the predetermined F-number, or the F-number of the exit pupil is the same as or smaller than the predetermined F-number, the interchangeable lens whose exit pupil position is different from the predetermined position is automatically focused. When the camera is equipped with a detection device, the exit pupil of the camera may cause vignetting on the focus detection light beam, and if the vignetting is not uniform on the image plane of the focus detection optical system, the subject image Distortion was generated at the center, and accurate focus detection could not be performed.

This drawback will be described in detail with reference to FIGS. 4 and 5 by taking the conventional example disclosed in Japanese Patent Publication No. 57-49841.

FIG. 4A is a schematic side view of the device, and FIG. 4B is a front layout view of the photoelectric conversion element.

A field lens 12 is arranged behind the taking lens 11, and a plurality of minute lenses 13, 14, 15, ... Are arranged near the focal plane behind the field lens 12, and minute lenses 13, 14, 15 ,.
Corresponding to the light receiving sections (13a, 13b), (14a, 14b), (15a, 15b), which are photoelectric conversion elements paired behind them.
Are arranged.

In the light-receiving sections 13a, the subscripts a and b form an image sensor array, and the position of the light-receiving section, which is a pair of photoelectric conversion elements behind each microlens, and the exit pupil position of the taking lens 11 are defined as follows. The curvature of each microlens is formed so as to come to a position substantially conjugate with each microlens. Further, in the field lens 12, it is necessary to bend the optical path more strongly for the minute lenses closer to the upper and lower ends in FIG.
When the exit pupil position of 11 is at a predetermined position 16, the images of the light receiving surfaces of each pair of photoelectric conversion elements are present on the exit pupil so as to be completely overlapped with each other, that is, the light receiving portions 13a, 14a,
The image of 15a ... is the photoelectric conversion element 13 at the position 11a of the taking lens 11.
The curvatures of the microlenses are determined so that the images b, 14b, 15b, ... Exist at the position 11b, respectively, respectively (hereinafter, the field lens 12, the microlens 13 and the like focus detection optics of the light receiving portion of each photoelectric conversion element). The position where the images from the system overlap each other is called the set pupil position).

In this automatic focus detection device, only when the light beam used for focus detection is hardly eclipsed by the exit pupil of the taking lens, that is, the bright taking lens with a small F number or the exit pupil position even with a large F number. Since it is equal to the set position, focus detection can be effectively performed only on a lens in which the influence of vignetting uniformly occurs on the detection element.

For example, when considering the case of a 35 mm single-lens reflex camera, the exit pupil position of the interchangeable lens, which is a taking lens, varies from about 50 mm from the focal plane to over 400 mm, and the F number is F1 as well. There exist from about 2 to dark ones that exceed F11.

If the automatic focus detection device corresponding to FIG.
The set pupil position 16 is set to 100 mm from the focal plane (hereinafter, the distance between the set pupil position and the focal plane is represented by P0. Therefore, in this case, P0 = 100 mm), the spread of the light flux used for detection, that is, Light receiving parts (13a, 13b), (14a, 14b),
If the spread of the detected light flux limited by the shape of the light receiving part of (15a, 15b) ... is designed as F4, it is darker than F4 and the distance between the exit pupil position and the focal plane (hereinafter, this is referred to as P0 ′ For an interchangeable lens that is not 100 mm, the detection accuracy of the automatic focus detection device will be significantly reduced.

This will be explained with reference to FIG. 5. FIG. 5 is an explanatory diagram showing the state and degree of vignetting by various photographing lenses in contrast to each other. With respect to the above design values, the detected light flux is F4 and the set pupil position is P0 = When the brightness is 100 mm and the brightness of the taking lens is F6, P0 ′ = 100 mm, 50 mm and ∞ are shown.

Fig. 5 (A) shows the case of P0 '= 100 mm, and F0 respectively.
The light receiving part of each photoelectric conversion element (15
a, 15b), (14a, 14b) ... The light fluxes that have passed through the F6 pupil of the taking lens are received by the light receiving sections (15a, 15b), (14
a, 14b) ... are assigned equally to the pairs. Therefore, when the subject has uniform brightness, as shown in FIG. 5 (D), the outputs 15a1 and 15b of the respective light receiving units 15a ...
1, 14a1 ... become uniform. In other words, in this case, the detection accuracy does not decrease despite the presence of vignetting. That is, it is possible to detect the deviation of two images by the row of photoelectric conversion element pairs.

FIG. 5 (B) shows the case of P0 '= 50 mm, and the light flux which has passed through the pupil of F6 of the photographing lens as described above is received by each light receiving portion 15a ...
It is distributed in different ratios in each place. Therefore,
At this time, the outputs of the respective light receiving portions 15a ... Are remarkably different from each other, as shown in FIG.

Here, the positions of the micro lens 13 and the micro lens 15 of both are +2.5 mm and -2.5 mm from the micro lens 14 at the center, respectively.
When the degree of vignetting δ in FIG. 5 (E) is obtained for the case of the position, the average value is 1, which is a very large value of approximately δ = 0.3. That is, the photoelectric output of the pair of photoelectric conversion elements is greatly different due to vignetting even though the subject has uniform brightness. Under such a situation, the pair of photoelectric conversion elements outputs two images. It is very difficult to detect the deviation.

FIG. 5 (C) shows the case of P0 ′ = ∞, and the vignetting in this case is completely opposite to the cases of FIGS. 5 (B) and (E). That is, the photoelectric output for a subject with uniform brightness is as shown in Fig. 5 (F), and the degree of vignetting δ is ± 2.5 mm.
It becomes about δ0.3 at the position. That is, as in the case of FIG. 5 (B), the photoelectric output of the pair of rows of photoelectric conversion elements is greatly different due to vignetting, even though the subject has uniform brightness. It will be very difficult.

In order to solve the above-mentioned drawbacks, the applicant of the present invention has disclosed in JP-A-60-86.
Japanese Patent No. 517 discloses a focus detection device provided with a vignetting state detection unit that detects a vignetting state of an image formed by a focus detection optical system by a pair of outputs output from an image sensor and outputs a signal according to the state. is suggesting.

In this method, the vignetting state is directly obtained from the output of the image sensor, so that the vignetting state can be detected with high accuracy for an object satisfying a special condition such as a subject having a uniform illuminance. However, when the subject has a complicated brightness distribution, the pattern of the image sensor output is also complicated, and the image position related to the pair of image outputs varies depending on the defocus amount, so even if various measures are taken, the degree of accurate vignetting is always present. It had the drawback of not being detectable.

[Problems to be solved by the invention]

Further, a method has been proposed in which the method of filtering the image sensor output is changed according to vignetting. However, this alone is not sufficient to prevent malfunction due to a decrease in detection accuracy.

In the present invention, the presence or absence of vignetting is determined by providing vignetting monitor means, and false detection is provided by providing threshold value changing means for changing the threshold value in algorithm processing based on this. The objective is to provide a stable focus detection device that does not have any problems.

In order to solve the above-mentioned problems, in the present invention, the taking lens is provided with lens information generating means, and the information of the open F value of the taking lens is stored in the memory thereof, more preferably, the information of the exit pupil position is also included. Accordingly, the amount of vignetting is calculated by reading this information from the body side.

As a result, an accurate vignetting amount can be grasped irrespective of the subject, and the optimum algorithm processing can be performed correspondingly. An example of a method of changing the algorithm processing according to vignetting has already been disclosed by the present applicant in Japanese Patent Application Laid-Open No. 60-
From the point presented in No. 86517, there are methods such as changing the filtering method of image output, performing logarithmic ratio processing, and limiting the image area. However, even if any of the above algorithm processing is used, there is a difference in the detection accuracy of the focus detection calculation result between the case where vignetting is present and the case where vignetting is not present, and vignetting is performed on an object close to the detection limit when there is no vignetting If this occurs, the detection accuracy is further reduced, which causes a malfunction.

Generally, the focus detection accuracy is improved as the contrast of the object is larger, and the image sensor of the focus detection apparatus is improved as the spatial frequency is higher than a certain upper limit determined by the pixel pitch. Therefore, a parameter related to the contrast or the spatial frequency information and having a correspondence relationship with the detection accuracy can be calculated and used as a guideline for the detection accuracy. Such a parameter will be referred to as an information amount from now on.

In the present invention, a threshold value is set for the calculated amount of information, and if there is an amount of information that is greater than or equal to this threshold, the detection result is recognized as valid and display / drive is performed. In addition to prohibiting display and driving, determine the presence or absence of the vignetting and change the threshold value according to the presence or absence of vignetting,
Alternatively, by changing the threshold value depending on the size of vignetting, it is possible to obtain a highly reliable focus detection device that does not malfunction even if vignetting occurs.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which a photographing lens 100 includes a lens information generating means 102 in addition to an optical system 101. The memory of the lens information generating means has an open F value F ₀ and an exit pupil. Contains data about the location of.

The light passing through the taking lens passes through the semi-transparent portion in the center of the Cook return mirror, is bent downward by the sub mirror 105, and is guided to the focus detection device. The focus detection device receives the above-mentioned light flux, the focus detection optical block 106, the photoelectric conversion means 107 composed of a large number of photoelectric conversion elements, and the image output of the photoelectric conversion means, and inputs the image output to the display drive means 114. It is composed of arithmetic control means 108 for transmitting an output. Here, the arithmetic and control unit 108 is generally constituted by a microcomputer or the like, and the processing contents thereof are described by a program, but in order to make the various functions easy to understand, they are described in a block diagram. Of course, any of these functions may be performed by hardware without being described in a program.

The contents of the arithmetic control means 108 will be described with reference to the flowchart of FIG. The image output from the photoelectric conversion means 107 is stored in the data memory of the arithmetic control means 108 in steps.

Next, at step, the data processing means 109 performs a plurality of filtering processes.

Performing a plurality of filter processes in this way is well known and is not the gist of the present invention, so a brief description will be given. That is, vignetting has the effect of mixing very low-order spatial frequency components into the subject image, so it is effective to perform filter processing that removes DC components. For example, in the first process, the DC component is not removed and the image data is stored in the memory area A. In the second process, the DC component is removed and the image data is stored in the memory area B.

Of course, both the first process and the second process are filter processes for removing DC components, and the main extraction spatial frequencies can be selected so as to be different, and three or more types of processes can be arranged in parallel. May be. Further, even when the filtering process is performed alone, the constituent requirements of the present invention are satisfied. Since it is effective to perform a plurality of filter processes in order to improve the detection accuracy, the present embodiment will be described with an example of performing two types of filter processes.

In step, the calculation means 110 performs known calculation processing for calculating the defocus amount on the image data in the memory area A and the image data in the memory area B, respectively. At this time, the above-mentioned amount of information is also calculated. As this amount of information, for example, the parameter E described in JP-A-60-37513 can be used. Of course, other than this, as long as it reflects the information amount of the subject and has a high correlation with the detection accuracy, it is possible to use even the sharpness as the information amount. Although there are various methods of obtaining the sharpness, for example, the method of obtaining the sum of absolute values of adjacent differences is most often used.

The step is a step of identifying whether or not the taking lens has the open F-number information and the exit pupil position information.

This step is not necessary in a camera body intended only for a new type of lens in which a lens information generating means including a storage means such as a ROM is built in the taking lens, and the step can be immediately performed.

However, in order to ensure that focus detection can be performed without error even with a conventional lens that does not even have the open F-number information, it is necessary to identify whether the new lens or the conventional lens is attached to the body. Required and the steps are to make this identification. Calculation means 10
If 8 can communicate with the lens, lens data flag = 1
If not possible, the lens data flag is set to 0. As for conventional lenses that have the function of mechanically transmitting the open F value to the body, if a function to electrically read the mechanically read value is provided on the body side, this will roughly eliminate vignetting. Since the determination can be made, the lens data flag = 1 may be set in this case.

When the lens data flag is 1 in step, the process proceeds to step and the vignetting monitor means 112 calculates the amount of vignetting or the presence or absence of vignetting using the lens data. When the lens data flag = 0, the process proceeds to step and the size of the vignetting is estimated from the output data of the image sensor.

Based on the value of the parameter Vig indicating the amount of vignetting thus obtained, the threshold value setting means 113 sets the threshold value for the focus determination in step.

 Next, how to set the threshold value will be described.

Generally, when there is no vignetting, there is a relationship between the amount of information and the focus detection accuracy such that the product of the two is almost constant regardless of the subject.

When vignetting occurs, this constant value increases as the degree of vignetting increases. Therefore, in order to guarantee the focus detection accuracy above a certain level, a certain threshold value is set, and when the amount of information is less than this threshold value, focus detection is disabled and the result at this time is not used for display or driving. Is preferred. It is necessary to change this threshold value at least depending on the presence or absence of vignetting, and it is preferable to change it also depending on the degree of vignetting if there is a margin in calculation processing.

Further, as a matter of course, it is necessary to individually set an optimum threshold value for each step result and each step result which have undergone different data processing.

The following Table 1 shows such a concrete example, and the arithmetic control means 108 stores such a table to set the threshold value corresponding to the vignetting amount Vig.

Second when the filtering process is performed in the step
If the process is a process of extracting higher spatial frequency components than the first process, the focus detection calculation using the contents of the memory B in the second process deteriorates the detection accuracy due to vignetting. Is small, so for information amount B,
The increase in the threshold value with the increase in vignetting is small.

Next, in step, the focus determination means 111 compares the corresponding threshold value with the information amount A and the information amount B to determine the focus.

When only one exceeds the threshold value, the calculation result of the defocus amount of that one is set as the final result.

When both exceed the threshold value, the result of the defocus amount B calculated using the higher spatial frequency is used as the final result. Of course, if the amount of information A is significantly larger than the amount of information B, the defocus amount A may be more accurate, so even if it is decided which defocus amount is the final result in T1 of both. Alternatively, the average value of the defocus amount A and the defocus amount B may be simply determined as the final defocus amount.

In step, the drive display means 114 is controlled based on this defocus amount.

Next, the steps and the contents of the steps will be described in detail. Step is release from lens information generation means F
This is a routine for calculating the vignetting amount using the value signal and the exit pupil position information. First, the principle will be described.

 First, the relationship between the exit pupil position and vignetting will be described.

FIG. 6 is equivalent to FIG. ± from the on-axis point 14 of the predetermined detection surface 100 near the position conjugate with the film surface
It is assumed that focus detection is performed by processing an image in the image height range of h (the range of points 13 to 15). The points 13, 14, and 15 substantially correspond to the positions of the minute lenses 13, 14, and 15 in FIG. 1, and the pupil division optical system is composed of a pair of re-imaging lenses. In the case of the re-imaging optical system such as, the field lens position placed in the vicinity of the film plane conjugate position corresponds to the position shown in FIG. 6 and the image detection range thereon is within the range of point 13 to point 15. Will correspond.

The point where the detection pupil (pupil used for detection) overlaps in the plane perpendicular to the optical axis is point 11a in FIG. 6 regardless of the position on the predetermined detection surface. This point is the same as point 11a in FIG. Therefore, the set pupil position 101 described above is determined as a plane perpendicular to the optical axis of the projection lens and passing through the point 11a. The distance between the set pupil position and the focus detection surface is B. Further, the distance between the exit pupil position 102 of the photographing lens and the predetermined detection surface 100 is P0. In FIG. 6, 11a, 14,
The angle α formed by 11b is the opening angle of the light beam used for focus detection, and its size is determined by the size of the light receiving elements 13a, 13b ..., 15a, 15b in the lenslet array focus detection optical system of FIG. In the case of the above-mentioned re-imaging optical system, it is determined by the size of the pupil of the re-imaging optical system.

If the F value corresponding to the opening angle α of this focus detection light beam is F _AF (Α is in radians).

Vignetting does not occur with a bright lens having an F value smaller than F _AF when the exit pupil position of the taking lens is equal to the set pupil position, but when the exit pupil position and the set pupil position differ.
No. 6 even with a shooting lens with an open F value that is somewhat smaller than F _AF .
As shown in the figure, vignetting begins to occur at the point 13 of the image height h.
In this case, the limit F value at which vignetting begins to occur In general, the following relationship is established.

Here, | | indicates an absolute value. This formula means that the larger the image height h and the farther the exit pupil position of the taking lens from the set pupil position, the smaller the F value at which the vignetting starts to occur, and only brighter lenses can be used.

The following amount can be used as the parameter Vig that reflects the amount of vignetting. Taking the open F value of the taking lens as F ₀ , Here, in Vig, the term that does not depend on h indicates the amount of vignetting that does not depend on the position of the image height, and the term that depends on h reflects the size of the asymmetric X-mark type vignetting shown in FIG. ing. The magnitude of the effect of vignetting on the focus detection error differs depending on the detection algorithm. Therefore, as the vignetting parameter, the expression may be used as it is, but only the term proportional to h may be used.

As described above, it is possible to know the presence or absence of vignetting and the size thereof from the exit pupil of the taking lens and the open F value. In this case, the exit pupil position appears in the form of its reciprocal, as is apparent from the expansion of the above formula, so it is easier to divide it by recording it as the reciprocal of 1 / P0 as the shooting lens data. preferable.

Also, when a teleconverter or the like is installed, the 1 / P0 form has an advantage that the arithmetic expression is easier when obtaining the combined pupil position of the master lens and the teleconverter.

The reciprocal form is also more suitable for the effect of vignetting due to the position of the exit pupil of the photographing lens on the detected light flux in the case of photometry other than focus detection. That is, even with the same difference of 25 mm, there is no great difference in the effect of vignetting on photometry and distance between P0 = 400 mm and 425 mm, but there is a large difference between when P0 = 25 mm and 50 mm. This is because the angle (β) looking into the opening is proportional to 1 / P0 and the size of the vignetting also depends almost on β, so it is possible to store the exit pupil position information in the 1 / P0 format. preferable.

Although it has been stated that the reciprocal form of the information on the exit pupil position stored in the lens is preferable, in practice it is appropriate to store it as 8-bit data, so the value range is from 0 to 255. The exit pupil position of most shooting lenses varies in the range of P0 = 40 mm to 400 mm, and the concrete expression form of the exit position information is α / P0, and the value of α is suitable in the range of 400 to 10000. Good value In a lens with a large amount of extension such as a macro lens, the exit pupil position greatly changes depending on the amount of extension, so divide the amount of extension into zones, put each zone at the optimum exit pupil position, and select with a known encoder. Is good.

Next, FIG. 1 shows the actual flow for calculating the vignetting amount.
This will be described with reference to FIG. In the step of FIG. 3, the memory exit pupil position information and the open F-number information of the lens information generating means built in the taking lens 100 of FIG. 1 are read by the arithmetic control means 108 on the body side. The vignetting monitor means 112 corresponds to the read exit pupil position information, the set pupil position information of the focus detection device included in the body, and the F corresponding to the opening angle of the detected light beam.
Using the information F _AF , F _Lim , which is the limit F value for vignetting occurrence, is calculated in a step, for example, by an equation. Next, the vignetting monitor means compares the open F value F ₀ and F _Lim of the taking lens previously read in step, and if F _Lim ≦ F ₀ , vignetting does not occur, and thus the vignetting parameter Vig is set to 0.
(Step) If F _Lim <F ₀ , vignetting may occur, and the magnitude of F ₀ and F _AF is compared in step. If F ₀ ≤ F _AF , the vignetting parameter is set to i
i), and if (step) F _AF <F ₀ , then ii
The vignetting parameter Vig is calculated by the equation i).

If there is no information on the exit pupil position, it is not possible to calculate an accurate vignetting amount as in the above example. However, even if only the open F value F ₀ can be obtained, the presence or absence of vignetting can be roughly determined by comparing the magnitude of this with F _AF , except for some lenses whose exit pupil positions are significantly displaced. Therefore, even at this level, the effect of the present invention is not appreciable.

 Next, the contents of the steps will be described.

The step is to calculate the effect of vignetting from the image sensor output data, and the specific method of this calculation has already been disclosed by the present applicant in JP-A-60-85617. Here, a more effective method than the method disclosed in the above publication will be described.

The amount of vignetting (Vi
A method of detecting g) will be described with reference to FIG.
For the sake of clarity, it is assumed here that the interchangeable lens mounted on the camera body is in focus.

In the figure, (A) indicates that the data stored in the memory A is 1
A pair of data strings A (a ₁ , a ₂ , a ₃ , ... a _i , ...; b ₁ , b ₂ , b ₃ ,
... ₁ b _i ...), the correlation value C (L) when the correlation calculation process is performed in the L data shift of the following formula (1) is the shift number L
Is plotted as a parameter.

In the absence of vignetting, the pair of image patterns in the in-focus state are essentially the same, so the shift number L =
At 0, the correlation value C (L) becomes the minimum value C _min .

However, when vignetting occurs, the shift number L that gives the maximum correlation C _min is not always L = 0 as shown in (A) in the figure, and it largely deviates from 0 as the vignetting state increases. This means that the focus detection cannot be performed accurately due to vignetting.

In the figure, (B) indicates that the data stored in the memory B is 1
A pair of data strings B (a ₁ ′, a ₂ ′, a ₃ ′, ... a _i ′; b ₁ ′,
b ₂ ′, b ₃ ′, ... b _i ′ ...) are subjected to the correlation calculation processing of the equation (1), and the DC cut filtering removes the vignetting pattern which is a very low-order frequency component. Therefore, the shift number L that gives the maximum correlation amount C _min is approximately L = 0, which indicates that focus detection is being performed accurately. By the way, here, C (O) in the same figure (A) is used as what gives the vignetting amount (Vig). That is, the correlation value C (focus point) calculated from the data string A in which the DC component in the in-focus state is not cut reflects the degree of mismatch between the patterns due to vignetting only.

In the above description, focusing is performed at L = 0 for the sake of simplicity. However, in practice, L = 0 is always set at the time of focusing due to an adjustment error or the like.
Does not. In this case, the value of L (L
Focus) may be used instead of 0. A method of specifically obtaining the L focus value will be described below.

From the data string A from which the DC component has not been removed, the in-focus point cannot be accurately known. On the other hand, the focus position detected by using the DC cut data string B is almost accurate. First, after obtaining the in-focus point (L focus) from the latter data string B, the data not DC cut By calculating the correlation value C (L focus) using the column A, it is possible to estimate the approximate vignetting amount (Vig) even when the lens data described above is unknown. Even when the interchangeable lens is out of focus, the vignetting amount (Vig) can be estimated by the same process. That is, the shift number L that gives the focus is the data string B
Then, the correlation value C
(L focus) may be calculated. The above step (7-
In 8), using the DC-cut data string B as described above, the DC component is not cut for the shift number L focus which gives the focus position calculated there after focus detection. From column A Is to be detected.

The vignetting amount (Vi) calculated from the lens data is set by setting the coefficient k so that Vig = k · c (L focus).
Since it can be handled almost equivalently to g), the algorithm processing is easy.

〔The invention's effect〕

As described above, according to the present invention, the degree of vignetting of the focus detection light flux by the photographing lens is calculated by the vignetting monitor, and the focus determination threshold value is changed based on the presence or absence of vignetting or the amount of vignetting. By performing the focus determination, it is possible to perform accurate focus determination on a lens that does not cause vignetting, and even if vignetting occurs, eliminating the case where the detection accuracy is significantly reduced enables display drive even with vignetting. A focus detection device in which no malfunction occurs can be obtained.

Therefore, according to the present invention, there is an effect that it is possible to detect the focus even in a dark photographing lens, which has been conventionally impossible to detect the focus due to vignetting.

[Brief description of drawings]

FIG. 1 is a block diagram of a focus detection device according to an embodiment of the present invention. FIG. 2 is a flow chart diagram of processing calculation of the focus detection device. FIG. 3 is a flow chart diagram of calculating an amount of vignetting of the focus detection device. FIGS. 5A and 4B are explanatory views of the focus detection optical system of the conventional example and the example, and FIGS. 5A to 5C are incident on the photoelectric conversion elements of the conventional example and the example. 5 (D) to 5 (F) are explanatory views showing the state of detection output of the photoelectric conversion element, and FIG. 6 is an exit pupil and vignetting of the embodiment of the present invention. And FIGS. 7A and 7B are explanatory diagrams showing the relationship between the correlation amount and the shift amount associated with the image shifting of the focus detection device. (Explanation of symbols of main parts) 11,101; Photographing lens 102; Lens information generating means 106; Focus detection optical block 108; Arithmetic control means

Claims (2)

(57) [Claims] 1. A focus detection optical system that forms a pair of optical images of the same object from a light beam that has passed through a taking lens, a photoelectric conversion unit that photoelectrically converts the pair of optical images, and an image from the photoelectric conversion unit. A focus detection device comprising: a first calculation means for calculating a defocus amount corresponding to a difference between an image formation surface of the taking lens and a focus detection surface using an output, wherein the image output of the photoelectric conversion means is Second calculation means for calculating the amount of information corresponding to the accuracy of focus detection, and vignetting detection means for calculating the vignetting amount of the light beam passing through the taking lens and incident on the focus detection optical system or the presence or absence of vignetting. A focus determination unit that compares the amount of information calculated by the second calculation unit with a predetermined threshold value and determines whether the defocus amount calculated by the first calculation unit satisfies the accuracy of focus detection; Of the vignetting detection means And a threshold value setting unit that changes the predetermined threshold value according to the calculated amount of vignetting or the presence or absence of vignetting. 2. The focus detecting device is installed in a camera body, the taking lens is attached to the camera body, and in the vignetting detecting means, the taking lens has lens information. In this case, the amount of vignetting or the presence or absence of vignetting is determined using the lens information, and when the taking lens does not have lens information, the amount of vignetting or vignetting is determined using the image output of the photoelectric conversion means. The focus detection device according to claim 1, wherein presence or absence is determined.