JPS60125814A - Focusing detector - Google Patents

Abstract

PURPOSE:To detect a correct in-focus state by utilizing lateral deviation of an image, to facilitate adjusting operation, and to attain size and cost reduction by providing a light shield member which is a stripe mask shape and has a reflection preventing function at the photodetection surface side of a photodetecting element array. CONSTITUTION:The photodetecting element array 11 is arranged for an optical photography system 2 on a surface conjugate to a film 6, and the light shield member 12 in the stripe mask shape is arranged at is photodetection surface side; and openings 17 are so formed that luminous flux passed through the upper side of an exit pupil surface about the optical axis of the optical photography system 2 is incident on photodetecting elements 14A-1-14A-n and luminous flux passed through the lower side is incident on photodetecting elements 14B-1- 14B-n. Illuminance distributions of images formed on those photodetecting element groups 14A and 14B coincide with each other in a focusing state and deviate in the opposite directions in an out-of-focus state according to the out-of- focus direction, so the lateral deviation direction of the image is detected to detect an in-focus, a front-focus, and a rear-focus state respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a focus detection device for detecting a focus state of a camera, a microscope, a high-density optical recording/reproducing device, etc.

(Prior Art) A conventional device shift detection method is known as a method for detecting the focal state of an object image formed by an imaging optical system.

FIG. 1 is a diagram illustrating the configuration of a focus detection device that implements such a lateral deviation detection method, when applied to an eye reflex camera. The image of the subject 1 is guided through a photographing optical system 2 and a quick-return type movable reflective mirror 3 to an observation optical system comprising a focusing plate 4, a pentaprism 5, etc., and the movable reflective mirror 3 is flipped up. is projected onto the film 6. The focus detection device has a half mirror 7 in the center of the mirror 3, and reflects a light beam passing through the half mirror 7 on a total reflection mirror 8 provided on the back surface of the mirror 3, and directs this light beam to the photographing optical system. Through a minute auxiliary optical system 9 such as a lenticular lens arranged near the predetermined focal plane of 2, that is, on a plane substantially conjugate with the film 6, the exit pupil plane of the photographing optical system 2 and the optical The light is incident on a row of light-receiving elements arranged on a plane that is substantially conjugate to the light beam. As shown in FIG. 2, this light-receiving element array recess is provided with a light-receiving element group and a decoy light-receiving element I0A-1''-10A-n and 10B-.
1 to 10B-n each correspond to a pair of light receiving elements (10A-4, 10B-1);
. Further, the auxiliary optical system 9 includes the light receiving element pair (10A-1, 10B).
-1);-・Bow (10A-n, 10B-n) K
The two light receiving elements constituting each light receiving element pair are located approximately on the exit pupil plane of the photographing optical system 2, perpendicular to the arrangement direction of the light receiving elements, and aligned with the optical axis of the photographing optical system 2. (in Fig. 1, the plane perpendicular to the plane containing the optical axis), that is, the images of the upper and lower parts of the exit pupil bordering on the optical axis in Fig. 1. is arranged to receive light.

In this configuration, when at least a part of the image of the subject 1 is projected onto the light receiving element array through the photographing optical system 2 and the auxiliary optical system 9, the light receiving element group 1 [IAK is the image of the photographing optical system 2]. In the figure, only the light flux that has passed through the lower part is incident, and on the contrary, & of the light flux that has passed through the upper part is incident on the above-mentioned light-receiving element group. The illuminance distributions match when in focus, and when out of focus, they shift laterally in opposite directions depending on the direction of the shift. The focus detection device shown in FIG. Detecting focus state.

However, in the conventional focus detection device shown in FIG.
The minute auxiliary optical system 9, such as the lenticular lens, etc.
It is difficult to manufacture the device, which makes the entire device expensive and large, which is a drawback.In addition, it is difficult to optically adjust each auxiliary optical system and its corresponding light-receiving element pair.

(Objective) The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks by using a striped mask-like light shielding member, and to solve the problem of light reflection caused by using this light shielding member, by providing the light shielding member with an anti-reflection function. It is an object of the present invention to provide a focus detection device which detects a correct focus state by utilizing the lateral shift of an image, which is solved by having a lateral shift of an image.

(Summary) The focus detection device of the present invention includes a light receiving element array disposed at or near a predetermined focal plane of an imaging optical system, and an optical path between this light receiving element array and the imaging optical system. Is the phase in the first light Raiko row dark? -+W child W Toki It has an aperture formed so that light from the first and second regions bounded by the plane including the optical axis of the imaging optical system is mainly incident, and unnecessary light rays are prevented. Equipped with a light-shielding member that has the function of absorbing light,
A lateral shift of an object image formed by a light receiving element group that receives light from the first area of the imaging optical system of the light receiving element array and a light receiving element group that receives light from the second area, respectively. The present invention is characterized in that the focal state of the object image formed by the imaging optical system is detected.

(Example) Hereinafter, the present invention will be explained with reference to illustrated embodiments.

FIG. 3 is a diagram showing the optical arrangement of the focus detection device of the present invention applied to a single-lens 7-lens camera, and the same reference numerals as those shown in FIG. 1 represent the same members, and their explanations will be omitted. In this example, in the photographing optical system 2, a light-receiving element array is arranged on a surface that is almost conjugate with the °C film 6, and a light-shielding member is arranged on the light-receiving surface side. The light flux is made to enter the light receiving element array U through the light shielding member U.

Next, the present invention will be described in detail based on a first embodiment of the present invention shown in FIGS. 4(4) to 4(k).

The fourth view is a perspective view showing the structure of the light receiving element and the light shielding member. The light-receiving element array (2) consists of a large number of light-receiving elements formed on the same substrate 13 in a straight line at equal intervals.

In this example, the odd-numbered light receiving element 1 with respect to the arrangement direction is
4A-1 to 14A-n and even numbered light receiving elements 14B
-1 to 14B-n are light receiving element groups 14A and 1, respectively.
4B, and a pair of light receiving elements (14A-1゜14B-1); one adjacent element in both groups;
A-n, 14B-n). The light shielding member is provided with n striped masks 16-1 on a transparent substrate 15 such as glass or polymer film, corresponding to each pair of light receiving elements.
~16-n are formed by the means described below, and these stripe masks are used to form two light-receiving elements constituting each pair of light-receiving elements, as shown in FIGS. 4(B) and (C1). The first and second regions, which are perpendicular to the direction and bounded by a plane containing the optical axis of the photographing optical system 2, are
In the figure, an aperture 17 is formed so that the light beams that have passed through the upper and lower portions of the exit pupil plane bordering on the optical axis mainly enter therein.

With this configuration, the two light-receiving elements constituting each pair of light-receiving elements are
light receiving element, for example, light receiving element 14A-1.

14B-1 have directivity in mutually different directions as shown in FIG. The light flux that has mainly passed through the upper side with the optical axis as the boundary enters the light receiving element 14B-1 of the light receiving element group 14B.
~14B-n mainly receives the light beam that has passed through the lower side. Therefore, these light receiving element groups 14A
, 14B, the illuminance distributions of the images formed on each of them match when in focus, and shift in opposite directions depending on the direction of the shift when out of focus, so the direction of lateral shift of the hoe can be detected. By doing this, it is possible to detect the in-focus state, the front bin focus state, and the back bin focus state.

Here, the stripe masks 16-1 to 16-n are 1
Tokomasa: In this example, it is as follows. That is, Fig. 4 (
As shown in q, chromium oxide (Cr203), which is a light absorbing material, is first deposited on the upper surface of the transparent substrate 15 (for example, glass) to a thickness of 250 μm, and then chromium (Cr), which is a light blocking material, is deposited on top of it. Vapor deposition is performed to a thickness of 700 μm. Then, etching is performed using ceric ammonium nitrate to form the opening 17. That is, the stripe masks 16-1 to 16-n are in contact with the glass and the light absorber 1
6b-1 to 16b-n are formed, and furthermore, light shielding bodies 16a-1 to 16a-n are formed thereon. The above-mentioned chromium is widely used for the above purposes because its thin film is strong and does not easily get scratched, and because it has good adhesion to the above-mentioned glass, and the above-mentioned chromium oxide alone can be used as a light shielding material and a light absorbing material. Although it would be preferable to serve both of the above, it is not practical due to its weak mechanical strength, and therefore it is necessary to form it with both the light absorber and the light shield. In addition, when using the above-mentioned chromium oxide as a light absorbing material for visible light, the film thickness is preferably about 250 μm as mentioned above, and the reflection of light is reduced by several degrees, to 3° when only the above-mentioned chromium is used. .

Next, FIGS. 6 and 7 show a second configuration example of a light shielding member used in the focus detection device of the present invention.

The light-shielding member 2 of ε is a light absorber (chromium oxide) 24b-1 to 24b-1 on the surface of the transparent substrate 15 on the imaging optical system side using the same means and material as the first light-shielding member in the embodiment described above.
24b-n, m light body (chromium) 24a-1 to 24a
- n stripe masks 24-1 to 24-n corresponding to each light-receiving element pair are provided to form a relatively large opening 25, and on the surface on the side of the light-receiving element pair. As the second light shielding member, 2n+1 stripe masks 26-1 to 26-(2n+1) are formed by the same means as described above, and these stripe masks 26-1 to 26-
(2n+1), as shown in FIG. 7, an opening 27 is formed which faces each light receiving element and whose width is relatively smaller than the length in the arrangement direction. If the light shielding members are used interchangeably, even if the optical adjustment between the light shielding member η- and the pair of light receiving elements is slightly deviated in the arrangement direction of the light receiving elements, each of the light shielding members facing each opening 27 can The light-receiving area of the light-receiving element does not change, so the light-receiving element group 14A.

Since the balance of the amount of light incident on the light receiving element 14B does not change, optical adjustment between the light shielding member 22 and the light receiving element array 11 is easy, and moreover, highly accurate focus detection can be performed at all times. Incidentally, in the light-shielding member used in the above-mentioned embodiment, it is
For example, if the light receiving elements 14A-1 to 14A-n are arranged slightly to the right in FIGS.
The light-receiving area of the light-receiving element 14B-
The light receiving areas of the light receiving element groups 1 to 14B-n are uniformly narrowed, and the imbalance between the outputs of the light receiving element groups 14A and 14B may become severe, making it impossible to perform highly accurate focus detection. A relatively high n degree is required for optical adjustment between - and light shielding member wind.

Next, a sixth configuration example of the light shielding member is shown in FIG.

In this example, light absorbers (chromium oxide) 28b-1 to 28b-n are placed on both upper and lower surfaces of the transparent substrate 15, respectively.
29b-1 to 29b-(2n+1) are provided, and light shielding bodies (chromium) 28a-1 to 28a-n, 2 are provided thereon.
9a-1 to 29a-(2n+1), and furthermore a light absorber (chromium oxide) 28cm1 to 28cmn.

29cm1~29cm(2n+1) is deposited to form stripe masks 28-1''-28-n, 29-1
~29-(2n+1) and an opening 25°27.

FIG. 9 shows a fourth configuration example of a light shielding member on a helmet. This configuration example shows a light shielding member 65 made of cadmium telluride (ca're) that has both light shielding and light absorption functions.
-1 to 55-n and 56-1 to 36-(2n+1) are vapor-deposited on both upper and lower surfaces of the transparent substrate 15, thereby forming a stripe mask.

Note that the opening 25.2 in the sixth and fourth configuration examples above
The size of 7 is shown in Figure 6.7 above. , - formed similarly to that of the second configuration example.

As described above, when the light shielding member having a light absorption function according to the present invention is used, the following extremely remarkable effects can be obtained.

That is, as shown in FIG. 10, stripe masks 37-1 to 57-n and 38-1 to 38-n are formed by vapor deposition on both upper and lower surfaces of the transparent substrate 15 using only a light shielding material with high reflectivity such as chromium. Then, among the light rays incident on the light shielding member,
Some light rays enter the light receiving elements 14A-3 and 14B-2n and are correctly received as shown by the light rays 51a and 51b, respectively, but some of them are reflected by the light receiving element 14A-1 and are blocked, as shown by the light ray 52. Some light reaches the body 68-2, and is further reflected by the light shielding body 38-2 to become stray light, which is received by some element of the light-receiving element frame A or B. Also, like the light ray 53, it is partially reflected by the light receiving element 14A-2 and reaches the light shielding body 37-2 located on the upper right side, where it is reflected again and is received by the light receiving element 14B-2. In this case, the light ray 55 that should originally be received by the light receiving element group A is
This means that the light has been received by the light receiving element group B. Furthermore, light rays like the light ray 54 are reflected back by the light shield 68-6 and the light shield 67-3 and are received by the light receiving element 14B-5, and light rays like the light ray 55 are reflected by the light shield
7-(n-1), which is reflected by a component of an optical system (not shown), and becomes stray light, each of which causes diffuse reflection.

In this way, depending on the light ray, the light receiving element may receive light that should not be on the upper surface of the stripe mask formed of chromium, which is a reflector. As a result, the correct illuminance distribution may not be obtained or the contrast of the image may deteriorate. In particular, if there is a very bright part of the image nearby, the image will deteriorate significantly and the focus detection ability will deteriorate. That is, specific failures include poor focus detection accuracy, a focus signal being output even though it is not in the focus position, or a narrowing of the range in which direction can be detected.

In the present invention, the light absorber solves this drawback, that is, the drawback of using a striped mask. That is, the first configuration example (
According to FIG. 4), the light absorbers 16b-1 to 16b-n absorb such reflected light of the light ray 53 (see FIG. 10),
According to the second configuration example (Fig. 6.7), the light ray 53
．． According to the third and fourth configuration examples (Figs. 8 and 9), the light rays 52 to 55 are similarly absorbed, which prevents the instability of focus detection due to the above-mentioned stray light. Because it can be prevented,
Correct focus detection can be performed.

The focus information obtained by the light shielding means using the light absorber as described above is processed by a signal processing circuit as shown in FIG. In this example, the appearance of a large number of light-receiving elements of the above-mentioned light-receiving element month/day is sequentially read out in the arrangement direction, and this is sequentially converted from analog to digital by the A/D conversion circuit 18 to the arithmetic circuit 1.
9, and here the light receiving elements 14A-k and 14B-
Let the outputs of k (where 1<k<n) be A and A, respectively, and calculate the following. This calculated value S is the above-mentioned light receiving element array -υ.

As shown in FIG. 12, the value is positive in the front focus state, zero in the in-focus state, and negative in the rear focus state, as shown in FIG. At 20, front focus, focus, and back focus are displayed. The operations of the light-receiving element array υ-1 A/D conversion circuit 18, arithmetic circuit 19, and display circuit 2o are controlled by a control circuit 21.

(Effects) According to the present invention, a light shielding member having an opening on the light receiving surface side of the light receiving element array is provided without using a minute auxiliary optical system for forming an image of the exit pupil of the imaging optical system, and thereby 2 adjacent
The light-receiving element is made to have directivity so that light from the first and second regions bounded by the plane containing the optical axis of the imaging optical system mainly enters the light-receiving element, and the light-shielding member is provided with directivity. Since it is treated to absorb unnecessary light, accurate focus judgment can be made, the structure is simple and easy to manufacture, and it can be made inexpensive and compact. Further, since the light-receiving element array and the light-shielding member can be housed in one piece, optical adjustment of both can be performed easily and with high precision.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a conventional focus detection device, FIG. 2 is a plan view showing the arrangement relationship between the auxiliary optical system and the light receiving element array shown in FIG. 1, and FIG. FIG. 4 is an optical layout diagram of the focus detection device of the present invention applied to a flex camera, and (Q is a perspective view of the focus detection device according to an embodiment of the present invention, a plan view of the main part. FIG. 5 is a directional characteristic diagram of the light receiving element that changes the pair in the present invention. FIGS. 6 to 9 are cross sections showing examples of the structure of the light shielding member in the focus detection device of the present invention. and a plan view; FIG. 10 is a sectional view of a light shielding member for explaining the adverse effects caused by a light shielding member that does not have a light absorption function; FIG. 11 is an example of a signal processing circuit of the focus detection device of the present invention. FIG. 12 is a diagram showing the form of a detection signal representing the focus state. 1. Subject 2. Imaging (photography) optical system 3. ......Movable reflection mirror 6----- Film 7... Half mirror 8... Total reflection mirror ji*@@@*@Photodetector array 12m*@ a@@ Light shielding members 14A, 14B... Light receiving element groups 14A-1 to 14A-n, 14B-1 to 14B-n
--- Light receiving element 15 --- Transparent substrate 17 --@φ.-- Aperture 18 --- A/D conversion circuit 19 --- Arithmetic circuit 20 --- Self-display circuit 21... Control circuit 22... Light shielding member 25-・Work 1・Aperture 27...Opening 16-1 to 16-1-Conflict...- ... Stripe mask 24-1 to 24-n- ... Stripe mask 2
6-1~26-(2n+1)・Sao・Stripe Mask 2
8-1 ~ 28-n...e...1111 Strive Mask 52.55-----Light Line 1 Ward'2 Ward'4 Ward (A) Power, 4 Ward (B) Ward 4 (C) Outer 5 wards Shima 6/hh 11 wards 12 wards

Claims (2)

[Claims] (1) A light-receiving element array arranged at or near the predetermined focal plane of the imaging optical system, and a light-receiving element array arranged in the optical path between this light-receiving element array and the imaging optical system, and adjacent to the light-receiving element array. a light-shielding member having an aperture formed so that light from first and second regions bounded by a plane including the optical axis of the imaging optical system is mainly incident on the light-receiving element; an anti-reflection means that has an anti-reflection function using an absorbing substance, and a light-receiving element group that receives light from a first region of the imaging optical system of the light-receiving element array; The system is characterized in that it detects the lateral shift of the object image formed in each of the light receiving element groups that receive light, and detects the value estimation ability of the object image formed by the imaging optical system. Focus detection device. (2) The light shielding member is made of a chromium (Cr) film, and the light absorbing material is made of a chromium oxide (Cr, 0.) film. Focus detection device.