JPS5917513A - Focusing detector - Google Patents

Abstract

PURPOSE:To detect a focusing state with high detection precision over an extremely wide range by detecting a focus on the basis of information on the lateral shifting of an image and information on the definition of the image. CONSTITUTION:The openings 16-n of numbers of stripe masks 17-n are given different directivity between photodetectors 15A-n and 15B-n to detect only pieces of luminous flux R and L, and photodetectors 15C-n are arranged between photodetectors 15A-n and 15B-n. Information on the definition of an image is obtained from the outputs of the photodetectors 15C-n, and the information of the lateral shifting of the image is obtained on the basis of the differences between the outputs of the photodetectors 15A-n and 15B-n; and focusing is detected on the basis of both pieces of information to realize the focusing detection with high precision over the extremely wide range.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a focus detection device for detecting the focus state of an optical device such as a camera or a microscope.

2. Description of the Related Art Conventionally, so-called blurred image detection methods and lateral shift image detection methods are well known as methods for detecting the in-focus state of an object image formed by an imaging optical system. FIG. 1 is a diagram illustrating a configuration example of the following case where a focus detection device implementing the blur image detection method is applied to a single-lens reflex camera. In the figure, a part or all of the light beam from a photographing lens 1 is divided into two parts by a quick return mirror 8 formed on a no-f mirror 2, and one part is divided into two parts by a focusing screen 44, a pentaprism 5, etc. At the same time, the other beam transmitted through the nauf mirror 2 is guided to a downward beam splitter by a total reflection mirror 6 placed behind the quick return mirror 8.
Here, it is further divided into two, for example, a pair of light receiving element arrays 9a and 9b arranged at positions separated by a certain distance across a plane conjugate with the intended focal plane 8 (film plane) of the photographing lens l.
We are trying to form an image on each of them.

In the above configuration, assuming that the output of one light receiving element array is X, for example, "' = ' xn - xn - 1'MAX" xn - x
Considering a value such as n-1'SUBMAX, this gives an evaluation value for the sharpness of the image that varies according to the sharpness of the image.

゛For the outputs of the two light-receiving element arrays 91L and 9b, the evaluation values S obtained from the above equation are respectively So.

S, S and S change as shown in FIG. 2 with respect to defocus. Therefore 80 and 82
If you observe the difference between S□〈S2, front pin, S > S
This means that 2 defocus directions and the in-focus position can be detected (8), such as rear focus at S = 82 and focus at S = 82.

The conventional example described above has the advantage of being able to detect the in-focus state with high precision by using a relatively simple optical system, but it is possible to detect a state in which the image-forming surface of the photographic lens 1 is far away from the expected focus position. Now, as shown in Figure 2, the evaluation value is S and 8.
Since there is no difference between the two evaluation values S1.82 and it becomes difficult to compare the two evaluation values S1.82, it is possible to focus, detect the front focus and the rear focus only within a limited range of the lens drive range, It has been extremely difficult to detect the in-focus state over the entire driving range of the imaging optical system.

As a conventional example using the lateral shift image detection method,
There is a configuration shown in the figure. In this figure, the same functional parts as in FIG. 1 are given the same reference numerals. In this focus detection device, the light beam from the photographing lens 1 reflected by the total reflection mirror 6 is arranged at or near the predetermined focal plane of the photographing lens 1, that is, the plane conjugate to the film surface 8. Emission of the photographing lens 1 to this auxiliary optical system 1o via a minute auxiliary optical system 10'E (4) Light receiving element array 11 arranged in a plane optically almost conjugate with the pupil plane
It is input to. As shown in FIG. 4, the light-receiving element row 11 includes light-receiving element groups 11A and IIB, and each light-receiving element 11A-1 to IIA of these light-receiving element groups 11A and IIB.
-n and l IB -1 to 11B-n each have a corresponding one light receiving element pair 11A-1, 11B 1
; form 11A-n, 11Bn;
All of these light receiving elements are arranged in a straight line. Further, the auxiliary optical system 10 includes a light receiving element pair 11.
There are n light-receiving elements corresponding to A-1, IIB-1i11A-n, and IIB-n, and the two light-receiving elements constituting each light-receiving element pair are located approximately on the exit pupil plane of the photographing lens 1, and A plane perpendicular to the arrangement direction and containing the optical axis of the photographing lens 1 (in Fig. 8, a plane perpendicular to the plane of the paper containing the optical axis), the portions located on each side as V boundaries, that is, the optical axis in Fig. 8 It is arranged so as to receive images of the upper and lower parts of the exit pupil plane bordering on .

In such a configuration, the photographic lens l and the auxiliary optical system l
When a small common part of the image of the subject is projected onto the light-receiving element group 11 through the light receiving element group 11A, only the following light beam passes through the lower part of the photographic lens l in the figure and enters the light-receiving element group 11B. On the contrary, only the secondary light beam passes through the upper part and enters, and the illuminance distribution of the images projected onto the light receiving element groups 11A and IIB match when in focus, and when out of focus, the illuminance distribution of the images is the same. They shift laterally in opposite directions depending on the direction. In the focus detection device shown in FIG. 8, the outputs of the light receiving element groups 11A and IIB are appropriately processed to detect the lateral shift direction of the image, and based on this, each focus state of front focus, rear focus, and focus is detected. is being detected.

The advantage of a focus detection device based on such a lateral shift image detection method is that the range in which focus can be detected is much wider than that of the focus detection device based on the blurred image detection method explained with reference to FIG. On the other hand, the gain of the lateral shift signal near the in-focus area is small, and the configuration is generally complicated. In particular, in the conventional focus detection device shown in FIG. This has drawbacks such as making the entire device expensive and large, as well as making it difficult to optically adjust each auxiliary optical system and its corresponding light-receiving element pair.

SUMMARY OF THE INVENTION An object of the present invention is to provide a focus detection device with a simple structure that has the respective advantages of the blurred image detection method and the lateral shift image detection method as described above, and eliminates the above-mentioned disadvantages.

The focus detection device of the present invention linearly connects a large number of light receiving element pairs arranged before and after a predetermined focal plane of an imaging optical system or a surface conjugate to that plane, and light receiving elements arranged respectively between the light receiving element pairs. A pair of light receiving element rows are arranged, and an optical axis of the imaging optical system is connected to each light receiving element arranged on the light incident side of the pair of light receiving element rows and forming the light receiving element pair of each light receiving element row. An aperture is formed so that the light beams from the first and second regions bounded by the surface containing the light beams are mainly incident thereon, and the light receiving element between the pair of light-receiving elements is formed so that the light beams from the two head regions are incident thereon. (7) a light-receiving element group that receives a light beam from a first area of the imaging optical system of each light-receiving element array; and a light-receiving element that receives a light beam from a second area (7). detecting the lateral shift of each object image formed in each group, and detecting the sharpness of each object image formed in each light receiving element group disposed between each pair of light receiving elements of each light receiving element row, The present invention is characterized in that it is configured to detect the focal state of an object image formed by the imaging optical system on its predetermined focal plane or on a plane conjugate to the predetermined focal plane, based on the detected information.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 5 is a diagram showing an example of the configuration of an embodiment in which the device of the present invention is applied to a single-lens reflex camera.

In this figure, the same parts as those in FIG. 1 are designated by the same reference numerals, and since these parts have been explained previously, their explanation will be omitted here.

As shown in the figure, the apparatus of the present invention receives each light beam before and after the predetermined focal plane of the imaging lens l or a plane conjugate to the plane of the imaging optical system, for example, as in the conventional method for detecting blurred images. A first light receiving element array 12A and a second light receiving element array 12B are provided. Each of the light receiving element rows 12A and 12B has a structure in which a light receiving element pair consisting of two light receiving elements and a light receiving element arranged between the light receiving element pairs are linearly and alternately arranged as shown in (8), details of which will be described later. It has become. In addition, those light receiving element rows 12
In the optical path between A, 12B and the photographic lens 1, that is, between the beam splinter and each light receiving element row 12A, 12B, for the adjacent light receiving elements forming a pair in each light receiving element row 12A, 12B, The light flux from the first region and the light flux from the second region bordered by a plane including the optical axis of the photographic lens are mainly incident on each light receiving element separately, and each light receiving element between each light receiving element pair is provided with: A light shielding member, such as a stripe mask plate 18, the details of which will be described later, is arranged to allow each of the light beams from the first and second regions to enter. 1, 1
4 is a light receiving element array forming substrate.

FIG. 6A is a top view showing the configuration and arrangement relationship of the light-receiving element array 1'/A and the stripe mask plate 18, and FIG.
is an explanatory diagram viewed from the side.

Each of the light receiving element rows 14A and IBB is mounted on the same substrate 14.
(See Figure 5).

The pair of light-receiving element arrays 12A and 12B have the same configuration and have the same function, so in order to simplify the explanation, only one of the light-receiving element arrays 12A will be described below.

In FIGS. 6A and 6B, the light receiving element array 12A includes a large number of light receiving element pairs 15A-1, 15B-1 knee: l 6A
-n, 11SB-n, and hole light receiving elements 150-1 to 11So-n inserted between each pair of light receiving elements.
are arranged alternately in a straight line.

On the other hand, the stripe mask plate 18 is made of a transparent substrate such as glass or a polymer film, and each of the light-receiving element pairs 15A-1, 1! IB-1:
...-: Opening 16- corresponding to 15A-n and 15B-n
1 to 16-n. The apertures 16-1 to 16-n and each light-receiving element pair 15A1, 15B-1: ---: l 5A-n
, 15B-n is shown in FIG. 6B. That is, each aperture -1 to 16-n 111J\skin light element pair 15A-1, 15B-0: -:
15A-n and 15B-n, first and second regions bordered by a plane perpendicular to the arrangement direction of the light-receiving elements and including the optical axis of the photographing lens l; That is, in FIG. 5, the light fluxes R and L that have passed through the upper and lower parts of the exit pupil plane bordering the optical axis are mainly incident on each of the light receiving elements 150-1 to 15C1 arranged between each light receiving element pair. −〇 is formed so that the light beams from both of these areas are incident.

With this configuration, the two light-receiving elements constituting each light-receiving element pair, for example, light-receiving elements 15A-1 and 15B-1, have directivity in mutually different directions as shown in FIG. Therefore, the fifth light receiving element group 15A-1 to 15A-n has a fifth
In the figure, the light beam that has passed mainly above the optical axis of the photographing optical system l enters the photodetector groups 15B-1 to 15B-15.
The light beam that has passed through the lower side is mainly incident on B-n. Therefore, each of these light receiving element groups 15A-1 to
15A-n: 1! The illuminance distribution of the images formed on each of IB-1 to IB-15B-n is the same when focused on the light-receiving element array 12A, but when out of focus, the illuminance distribution varies depending on the direction of the front focus or rear focus shift. Since the images are shifted in opposite directions, by detecting the direction of the lateral shift of the image, the state of focus on the light receiving element array 12A can be detected. Moreover, since the advantages of the lateral shift image detection method are fully utilized, the focus detection range is further expanded compared to the method using the blurred image detection method described in FIG. on the other hand,
Each light receiving element 15A of the light receiving element row 12A 1.15
B-1: ...: Since a light beam that is not divided into exit pupils is projected onto the light receiving element groups 150-1 to 150-n arranged between 15A-n and 15B-n, this light receiving element group The images projected on 150-1 to 150-n do not cause lateral shift and have a sharpness that corresponds to the focal state on the light-receiving element array 12A of the photographic lens 1.

In the apparatus of the present invention, the above-described horizontal shift image detection and sharpness detection are also performed for the other light-receiving element array IBB, and each light-receiving element array 12A.

The focus state is detected based on the lateral shift information of the next image obtained from 12B and information regarding the sharpness of the image.

For example, each light-receiving element pair 15A-1, 15B-1 in the light-receiving element rows 12A, 12E:...=15mm-"+1
5B Light receiving element group 1150-1 to 1 arranged between n0
When the output of 50-n is turned on, the evaluation function F1 representing the sharpness of the image projected onto the light receiving element array 12A is as follows: F=IO-01... (1) l n n+1! la Columns 12A, 12B
When a projection image is formed on the projection image, the evaluation values F□F change so as to differ from the peak value.

On the other hand, the output of the light-receiving element group 15A-1-15-n consisting of one of the light-receiving elements constituting each light-receiving element pair is inputted, and the output of the light-receiving element group 15B-1 to 15B-n consisting of the other light-receiving element is inputted.
Let the output of n be Bn, and as the evaluation function F8 representing the lateral shift of the image on the light receiving element array 12A, for example, F8=Σ(IA, , -Bn, 1-IAn-Bn+, l
')...Using (2), the other light receiving element row 1
Similarly, the evaluation function representing the lateral shift of the image on 2B is
Then, F.

As shown in FIG. 8(b), F has a value of zero at the position of each peak value of the evaluation functions F and F by the blurred image detection method because no lateral shift occurs in the image, and the value is zero at this position. If it deviates from this, a lateral shift occurs, resulting in a curve whose sign reverses depending on the direction of defocus. Therefore, in the defocus direction of front focus and rear focus, the evaluation function F8 of equation (2) above. F8. ? , are the same sign, it is determined by the positive or negative inner sign, and F8. If the defocus direction and focus are determined using the evaluation functions F and F according to equation (1) when F and F have different signs, the conventional blurred image detection method explained in Figure @1 can be used to determine the defocus direction and focus. Compared to focus detection devices, it is possible to detect the in-focus state over an extremely wide driving range of the imaging optical system.
The in-focus state can be detected with high detection accuracy, which is an advantage of the blurred image detection method.

FIG. 9 is a block diagram showing a schematic configuration of an example of a signal processing circuit that obtains focus information representing in-focus, front focus, and back focus based on the output of each light receiving element array 12A, 12B.

In this example, the outputs of a large number of light receiving elements of each light receiving element row 12A, 12B are simultaneously held in the sample and hold circuit 20, and this hold value is determined for each output of each light receiving element row 12A, 12B according to the arrangement order of the light receiving elements. read sequentially,
This is sequentially converted from analog to digital by the A/D conversion circuit 21 and taken into ffVl and the second arithmetic circuit 22.28. In the first arithmetic circuit 22, each light receiving element array 12A,
Using the output c c' of the light receiving element group consisting of light receiving elements between the adjacent light receiving element pairs of 12B, the above (1) n,
The evaluation functions F0 and F2 representing the sharpness of the image on each light receiving element row 12A, 12B are calculated based on the formula n, and the second calculation circuit 28 calculates each light receiving element pair of each light receiving element 12A, 12B. Outputs AB and A' B of each two light-receiving element groups consisting of different light-receiving elements
' to the equation (2) above, n, n
Evaluation functions F and F, ? representing the lateral shift direction of the image on each light-receiving element array 12A, 12B based on n, n? The calculation results are led to judgment (b) path No. 2.

Their evaluation functions F□, F2. F8 and F are the eighth
As explained in the figure, the predetermined focus is 7?1. For a surface conjugate to Kesore, in the front bin state, F, > F in the range where F8 and F have different signs, and F < 0 in other ranges. F, <O. When in rear pin state, F8
Fx<Fs in the range where and F have different signs, and F>0 in other ranges. F,>O. Also, when the imaging optical system focuses on the predetermined focal plane or a plane conjugate to it,
1゛8 and F have different signs and F□=F2.

That is, for the range in the front and rear bin directions where Fo and F2 cannot be compared, the positive sign of F and F4,
They can be easily distinguished by their negative values, F8 and F.

In the range of opposite signs, the in-focus state can be determined with high accuracy by comparing F□ and F.

(15) In the determination circuit 24, F□, F1+, '8 and F,
The above relationship is determined with respect to
Displayed by Light receiving element row 12A.

IBB, sample and hold circuit 20. A/D conversion circuit 2
1. First and second arithmetic circuits 22.28, determination circuit 24
Each operation of the display circuit 25 is controlled by a control circuit z6.

In the embodiment described above, the focus state is detected using lateral shift information when the focus is out of focus, and using blurred image information when the focus is near the focus, but both It goes without saying that detection may be performed using information, or lateral shift information may be used to detect A near focus.

As explained above in detail, the focus detection device of the present invention is configured by the predetermined focal plane of the imaging optical system or its surface and a co-receiving element, and the focus detection device is configured by the predetermined focal plane of the imaging optical system or its surface and the co-receiving element. (16) detecting the intensity distribution of the image; and (16) detecting the first and
□The configuration is commonly used for detecting lateral shift of an image due to the light flux from the second area. Regarding the driving range of the optical system where it is difficult to compare the blurred images, the out-of-focus direction is detected by the lateral shift image detection method, and regarding the driving range of the front imaging optical system where it is easy to compare the blurred images, The focus state is detected using an image detection method using an image that does not cause lateral shift. Therefore, according to the apparatus of the present invention, with a relatively simple configuration, it is possible to achieve the out-of-focus direction detection effect over a wide range over the entire driving range of the imaging optical system, which is an advantage of the lateral shift image detection method, and the blurred image detection method. It is possible to provide a focus detection device that also has the advantage of highly accurate focus state detection.

In addition, as in the nine configurations shown in the above embodiments, the light flux from the exit pupil of the imaging optical system is divided into the first and 1g2 areas bordered by the plane containing the optical axis of the imaging optical system. In the case of using a stripe mask as a light shielding member for dividing the luminous flux, the structure is not only simple, but also
It has the advantage of being easy to manufacture and optically adjusting with the light-receiving element, being economical, and being able to be made compact.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of the configuration of a focus detection device using a conventional blurred image detection method, and Fig. 2 shows a change in the evaluation value representing the sharpness of an image with respect to the telefocus direction in the one shown in Fig. 1. 8 is a diagram showing a configuration example of a conventional focus detection device using the lateral shift image detection method. FIG. 4 is a diagram showing an auxiliary optical system and a light receiving element array in the conventional example shown in FIG. 8. FIG. 5 is a plan view showing the arrangement relationship between the strip mask and the light receiving element array shown in FIG. FIG. 7 is a diagram showing the configuration and their arrangement relationship; FIG. 7 is an example of the directivity characteristics of a pair of light-receiving elements in the same row of light-receiving elements; FIG. , a diagram showing an example of the relationship between signals representing the lateral shift of an image, and FIG. 9 is a block diagram showing a schematic configuration of an example of the signal processing circuit of the focus detection device of the present invention. Lens, 2... Half mirror 18... Quick return mirror, 6... Total reflection mirror, 7...
・Beam splitter, 8... Film surface, 12A, 1
2B... Light receiving element row, 18... Stripe mask plate, 14... Substrate, 15A, 15B... Light receiving element group,
15A-1 to 15A-n, 15B-1 to 15B-n,
150-1 to 150-n-・-light receiving element, l 6-
1 to 16-n-aperture, 17-1 to 17-n...stripe mask, BO...sample hold circuit, 2
1... A/D conversion circuit, 22... First arithmetic circuit, 2
8... Second arithmetic circuit, z4... Judgment circuit, 25...
- Display circuit, 26... control circuit. 11flBi159-17513 (7) Figure S Figure 9 Procedural Amendment July 18, 1981 1. Indication of the case 1987 Patent Application No. 126273 2. Name of the invention Focus detection device 3. Make the amendment Patent applicant (037) One person other than Olympus Optical Industry Co., Ltd.
It says, "Auxiliary optical system 10 consisting of multiple microlenses.
” he corrected. 2.In the 11th line of page 5 of the same page, there is a statement that says, “I have n pieces.”
Corrected "n microlenses 1 (1-IP-1, 11-n, and the above"), and changed the phrase "image" in line 17 of the same page to 8. In the 19th line of page 6 of the same page, the word "minor" is corrected to "consist of a large number of microlenses." 4, page 10, line 15.17.20, “t 6-nJ
116-+n+1)J, and in line 16 of the same page, the line ``Stripe Mask 17'' is corrected to read [Stripe Mask 17-1''-17nJ. 5, Page 11 of the same page. Lines 7-8, page 12, 11-12
"15C-nJ" in the line 14 of the same page, and in the 6th line of the 18th page are replaced with [150-1nJ, respectively.
-1) Correct it as J. 6. Corrected "defocus direction" in line 7 of page 19 to "defocus direction" and added
Correct "strip mask" in the line to "stripe mask". 7 In the same page 20, line 11, replace “15cmn” with “
Corrected 15cm (n-1)J to N on the same page [t6-
Correct nJ to [e-1n+1)J. Figures 6A and 6B of the cylinder in Figure 8 are corrected as shown in the attached correction diagram.

Claims (1)

[Scope of Claims] 1. A plurality of light receiving element pairs arranged in front of and behind a predetermined focal plane of an imaging optical system or a plane conjugate to that plane, and light receiving elements respectively arranged between the light receiving element pairs, are arranged in a straight line. a pair of light-receiving element rows arranged in a row, and an optical axis of the imaging optical system to each light-receiving element arranged on the light incident side of the pair of light-receiving element rows and forming the light-receiving element pair of each light-receiving element row. An aperture is formed so that the light beams from the first and second regions bounded by the surface containing the light beams are mainly incident thereon, and the light receiving element between the pair of light-receiving elements is formed so that the light beams from the two head regions are incident thereon. a light-shielding member having a light-shielding member, and a light-receiving element group that receives the luminous flux P from the first region of the imaging optical system of each of the light-receiving element arrays and a light-receiving element group that receives the luminous flux from the second region, respectively. In addition to detecting the lateral shift of each object image formed, the sharpness of each object image formed on the light receiving element group arranged between each light receiving element pair of each light receiving element row is detected, and these detected information are detected. A focus detection device characterized in that the imaging optical system is configured to detect a focal state of an object image formed on a plane conjugate to the planned focal plane f:, based on the imaging optical system.