JPS59208515A - Focus detecting device - Google Patents

Abstract

PURPOSE:To detect exactly a focus even in case of a dark object by providing an insensitive part on each pair of photodetectors for constituting a photodetector group. CONSTITUTION:A titled device is provided with many minute optical members 24 arrayed in the rear of an image forming lens 2, and a pair of photodetectors 26a, 26b arrayed adjacently to each other in the rear of the respective members at every said optical member 24. This device is constituted so as to detect a focus of the image forming lens 2 basing on an output of these photodetectors 26a, 26b, and provided with a projecting means for generating a luminous flux toward a focus detecting object through the image forming lens 2 from the rear of the image forming lens 2. Also, a blind part B having a shape and size by which a luminous flux generated from a projecting meand and reflected by the image forming lens 2 is not photodetected by a pair of photodetectors 26a, 26b is provided between a pair of photodetectors for constituting each pair of photodetectors 26a, 26b.

Description

DETAILED DESCRIPTION OF THE INVENTION 2- Technical Field The present invention relates to a focus detection device for detecting the focus adjustment state of an imaging lens.1 More specifically, the present invention relates to a focus detection device used in an automatic focus adjustment device of a camera.

Prior Art Conventionally, according to Japanese Patent Publication No. 57-4984.1, a large number of microlenses are arranged in the direction perpendicular to the optical axis near the expected focal plane of the imaging lens, and a first and second microlens is arranged behind each microlens. By arranging the second light-receiving elements adjacent to each other across the optical axis of each microlens, the first light-receiving element group receives light from the subject through the first region of the exit pupil of the imaging lens. At the same time, the second light-receiving element group receives light from the object through the second region of the exit pupil, and the focusing state of the imaging lens with respect to the object is determined by comparing the light-receiving states of both light-receiving element groups. Devices for detection are known.

However, such a device has the disadvantage that if the subject is dark, both light receiving element groups are not inspected and a sufficient amount of light is not received, making accurate focus detection impossible.

Purpose The present invention was made in view of the above-mentioned drawbacks, and its purpose is to enable accurate focus detection even for dark objects and to enable accurate focus detection even when the imaging lens is replaced. An object of the present invention is to provide a focus detection device with a simple configuration.

SUMMARY OF THE INVENTION In order to achieve the object described in "Summary of the Invention", the present invention projects a light beam toward a subject from behind an imaging lens, and receives reflected light from the subject by the first and second light receiving element groups. By performing focus detection by comparing the light receiving states of both light receiving element groups, accurate focus detection is possible even for dark subjects, and the lens of the imaging lens is prevented from reaching the subject by the light beam. In order to prevent the reflected light from the surface from being received by the light-receiving element group and deteriorating detection accuracy, each light-receiving element pair constituting the light-receiving element group is provided with a dead section. .

Example Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 shows a lens-interchangeable single-lens reflex camera using a focus detection device according to an embodiment of the present invention. In the same figure, (2) is a deformed glass type lens i (4
), and (1)) is a camera body with which various lenses can be exchanged. (8) is a light emitting diode that emits infrared light provided near the focusing plate (10), and the focusing plate (
The light is focused by a lens (10a) integrally molded with 10), and becomes a parallel light beam with a small diameter (for example, 3fiφ). This parallel infrared light beam is reflected by a mirror (12) provided at the center of the focus plate (10), and further reflected by a movable mirror (14) to direct the optical axis of the photographic lens (2). The light enters the lens system (4) of the photographic lens from the rear as a small-diameter light beam centered at the center. This infrared light beam is diverged by a photographic lens (2) and projected toward the subject.

5 - Then, the infrared light reflected by the subject passes through the photographing lens (2) again, passes through the light semi-transparent part at the center of the movable mirror circle, is further reflected by the sub mirror (1G), and reaches the light receiving part (18). ). The light receiving section (18) has a spectral sensitivity determined in advance so as to photometer infrared light.

(20) detects the focus adjustment state of the photographing lens (2) according to the light receiving state of the light receiving unit (18), and displays front focus, focus, back focus, etc. based on the detection result. This is an arithmetic processing circuit that sends a signal indicating a focus adjustment state to a display device or a focusing means (not shown) that focuses a photographic lens toward focusing. In this way, by projecting light from the focus detection device toward the subject and performing focus detection using the reflected light, accurate focus detection is possible even for dark subjects.

However, a part of the infrared light emitted from the light emitting diode (8) does not reach the subject and is reflected by the lens surface of the photographic lens (2), causing the light receiving part (]8
If the light enters the light, it becomes harmful light 9 and focus detection accuracy deteriorates. This will be explained using FIG. 2. In FIG. 2, the lens surfaces of the lens system (4) of the photographic lens (2) are arranged in order from the object side: rl, r2.
...-..., rll. aI''!, indicates the projected light that is not emitted from the light emitting diode (8) and is directed to the subject (0) via the photographic lens (2), a part of which is reflected at the lens surface (rl) and (r + o). It is reflected and becomes reflected light beams 1) and C. When these reflected light beams 1] and C enter the light receiving part (18) for focus detection, they become harmful light, and such reflected light beams can occur. Photography lens (2)
Table 1 shows the configuration of the lens system (4). In the table, f represents the focal length, FNa represents the F number, and 2ω represents the angle of view.

7- 1st Table f=50τ FN[l=1. ．． 7 2ω247
° Radius of curvature Core thickness Refractive index Atsube number r+ 37.99 dl 4.66 N+ 1.7003 Si14
7.6r2332.30 d20.1.6 r4 37.04 642.22 r5 66.81 ds 1. ．． 4-6 N3],,7006
ν3301T'6], 5.32 d611.62 r7 -16.83 d7 0.88 N4 1. ．． 6129 ν437
0rs 63.42 ds 6.41 Ns 1.6935 ν55
34r9 -22.58 d90.16 rlo 278.82 d102.80 N6 1. ．． 781 Shiro 4
46rn -48,58 Figure 3 shows the optical system inside the light receiving section (18).
(22) is a condenser lens, (24) is a large number of microlenses arranged behind it, and a pair of light receiving elements (26a) (26b) are arranged behind each microlens. Table 2 shows the configuration of the condenser lens (22+ and micro lens group).

Table 2 Radius of curvature Core thickness Refractive index Atsbe number 24
dl40.58 N+31.49
14 57.8 Figure 4 (a) (+)) (C) is
In the light-receiving section as described in Japanese Patent Publication No. 57-4.9841, a light beam emitted from a light-emitting diode and reflected by a photographing lens enters a pair of light-receiving elements provided for each microlens. This figure shows how harmful light becomes.

9-8- Figure 4(a) shows that the light beam reflected by the lens surface (r8) of the photographic lens is 2 times vertically from the optical axis of the photographic lens.
This shows a state in which the light beam passes through a microlens (24a) having an optical axis (Aa) separated from the body, and this light beam is a reflected light beam that is placed adjacent to the microlens (24a) across the optical axis (Aa). This shows the state in which the light beam passes through the microlens (24, b) whose optical axis (Ah) is vertically 1 inch away from the optical axis of the photographic lens, and this luminous flux passes through the microlens (24, b).
The light enters a pair of light-receiving elements (28a) and (28b) arranged adjacently across the optical axis (Ab) of 411) and becomes harmful light. Figure 4 (q) shows a microlens (24C) in which the light flux reflected by the lens surface (rl) of the photographic lens has an optical axis (Ac) that is vertically away from the optical axis of the photographic lens by 0.5 rnJn. A pair of light receiving elements (28a) (28b) are transmitted through the light and are arranged adjacently across the optical axis (Ac).
') and becomes harmful light. Each of the above-mentioned harmful lights becomes a spot image on the light-receiving surface of the light-receiving element, and the situation is shown in FIG.

10- In FIG. 5, (A) is the optical axis (Aa) of the microlens shown in FIG. 4. (Ah) is also 1. < is (Ac) and (
SL) (S2) (S3) Figure 4 (a)
0))(c) This is a spot image formed by the illustrated harmful light. Table 3 shows the spread of each spot image when the origin is the point through which the optical axis of the microlens passes, with the Y coordinate in the downward direction and the X coordinate in the horizontal direction, as shown in Fig. 5 -. Shown below. In Table 3, the coordinates of the edge of each spot image are (0, Y+), the coordinates of the center are ρ, Yo), the coordinates of the lower end are (D, Y2), and the width in the left and right direction is Xl.

Table 3 However, the diameter of the projected infrared light beam is 3 Hu.

In this embodiment, as shown in FIG.
(261)) from receiving the light beam reflected by the 1/lens, each of the pair of light receiving elements (26a) (261)) placed adjacent to each other with a microlens in between is placed near the optical axis. It is characterized by having a shape having a dead part). In this example, the shape of the dead part provided between the pair of light receiving elements is a circle whose center is on the optical axis of the microlens, as shown in circle Φ in FIG. 5, and its diameter is 0.075wn. .

Here, the shape and size of the dead area are determined according to the range illuminated by the reflected light flux as described above, and are determined by the distance from the optical axis of the photo-taking lens of the pair of light-receiving elements, the reflected lens surface, and Although the above range changes in various ways depending on the subsequent configuration of the lens system, etc., the above range, that is, the shape and size of the dead area is set with these things in mind, so that the reflected light flux does not exceed the outside of the dead area. The light does not enter the light receiving element and become harmful light.

According to this embodiment, focus detection is performed using the reflected light from the subject of the infrared light beam projected from the light emitting diode (8) towards the subject via the photographic lens (2).
Accurate focus detection is possible even when the subject is dark, and the dynamic range of the focus detection device on the low-brightness side can be expanded. Even if the light is reflected by the light, it does not enter the light receiving element group for focus detection, so it does not become harmful light during focus detection. Furthermore, by using infrared light for focus detection, a small diameter parallel beam centered on the optical axis of the L1 photographing lens can be emitted, which can eliminate the influence of stationary light in the subject. There is no variation between the focus detection system and the focus detection system.Furthermore, compared to conventional devices, the configuration is simpler because only slight changes such as adding a light emitting diode and changing the shape of the light receiving element are required.

FIG. 7 shows a pair of light receiving elements (2
6a) This shows the shape of (261)), and in this example, the dead part ) of the previous example was circular, but in this example, it is a long shape that is rotationally symmetrical about the optical axis of the microlens. This embodiment differs from the previous embodiment 13 in that it has a circular dead section 0. However, as shown in the figure, semicircular notches (d) are formed on opposing sides of both light receiving elements (28a, 281). This means that when the light receiving element pair (28a) (28b) is arranged symmetrically with respect to the optical axis of the photographing lens, the spot image (Sl) (S2) (S3) due to the light reflected from the lens surface is
As shown in Fig. 9 and Fig. 9, it is formed at a position shifted from the optical axis of the microlens in the direction in which the light receiving elements are arranged. With this configuration, the portion (e) corresponding to the difference between the circular shape and the oval shape can be used as the light-receiving surface, so the light-receiving area increases and a larger output can be obtained even for a dark subject.

Fig. 10 shows a pair of light receiving elements used together with the pair of light receiving elements shown in Fig. 8, and is arranged so as to be used especially when the aperture diameter of the lens attached to the camera body as a photographic lens is small. It shows what was done. This light-receiving element pair is the light-receiving element pair (26
a) It has the same shape as (26b>), but based on the same-shaped circle (G) drawn for comparison 14- in Figures 8 and 10, it becomes 10th
It can be seen that the photodetector pair (30a) (3o1) in the figure has a smaller outer diameter. However, both light receiving elements (3oa) (3o
The shape and size of the dead area (q) formed between (1) and (1) are the same for both. This is because the spot image by the light reflected from the lens surface can be formed in the same way as on the optical axis of the photographing lens. be.

FIG. 11 shows a light-receiving element pair according to still another embodiment of the present invention, in which the light-receiving element pair (26a> (2
6b) Blind part (C) K second light receiving element pair (32a)
, (32+)), and when the subject is bright and illumination by the light emitting diode (8) is unnecessary, the light emitting diode (8) is turned off and the second light receiving element pair (32a) (
32 +)) (7) Output is also used for focus detection, and when the subject is dark and the light emitting diode 8) is lit, K is used as the second light receiving element pair (32a) (3213
) is configured to remove harmful light by blocking the output of the light.

With this configuration, when the subject is bright, focus detection can be performed without illuminating the subject, as in the conventional device, and power consumption due to lighting of the light emitting diode can be reduced. Here, the light emitting diode (8
) may be controlled by a manual switch or may be configured to be controlled according to the brightness of the subject. Note that the shapes of the light receiving elements in each of the above embodiments are as follows. This was determined by focusing on the light reflected from the lens surface by the lens system of a modified Gaussian type standard lens as shown in Figure 2. This was determined by calculating the optical path of the light reflected from the lens surface for various lenses. This is because it has been confirmed that the standard lens data can almost represent the optical path of light reflected from the lens surface.

In other words, even if a beam of light is projected through a wide-angle lens or a telephoto lens, the inter-plane reflection of each lens will follow almost the same optical path as the optical path caused by inter-plane reflection of a standard lens, so it is necessary to further increase the area of the dead area. It means no.

Effects As described in ``2'', the present invention allows light transmitted through two different regions of the exit pupil of an imaging lens to be transmitted through a large number of micro optical members so as to correspond to each micro optical member. In a focus detection device that receives light with a pair of arranged light receiving elements and detects the focus of an imaging lens based on the outputs of a large number of pairs of light receiving elements, light is passed from behind the imaging lens to the focus detection target through the imaging lens. A light projecting means for emitting a luminous flux toward the target is provided, and each pair of light receiving elements described in -I- is arranged between two light receiving elements arranged adjacent to each other. The device is characterized in that it has a shape that includes a dead section that does not receive the emitted light beam, and with this configuration, accurate focus detection is possible using the projected light from the light projecting means even when the object is dark. Even if the light emitted from the light projecting means is reflected by the lens surface of the imaging lens, it will not enter the light receiving element for focus detection and become harmful light, and the imaging lens Accurate focus detection is possible even if the 2D device is replaced, and the configuration is simple as there are only a few changes in the configuration compared to conventional devices.

Furthermore, as in the embodiment, the light projected from the rear of the imaging lens is made into a small diameter parallel light beam centered on the optical axis,
By forming the blind portion into an elliptical shape, harmful light can be removed without significantly impairing the light-receiving area of the light-receiving element.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an automatic focusing type eye reflex camera using the present invention, Fig. 2 is a diagram showing the optical path of light reflected from the lens surface, and Fig. 3 is a focus detection device according to an embodiment of the present invention. Figure 4 is a diagram showing the drawbacks of the conventional device, Figure 5 is a diagram showing the position of a spot image due to light reflected from a lens surface, and Figure 6 is a diagram showing the position and spread of the spot image. FIG. 7 is a diagram showing a pair of light receiving elements according to one embodiment of the present invention. FIGS. 8 and 9 are diagrams showing a pair of light receiving elements according to another embodiment. 10 and 10 are diagrams each showing still another embodiment. (2); Imaging lens, (8) (1oa); Light projecting means,
0; Focus detection target, country); Microscopic optical member, ('26a)
(26b); Light receiving element pair, (B) (C) i dead area, (
30a) (30t)) i Photodetector pair. Applicant: Minolta Camera Co., Ltd. 18- Figure 5, Figure 6, Figure 7 LLl) Figure 1, Figure 11, page 1 continued 9 Inventor: Norio Ishikawa Osaka Kokusai Building, 2-30 Azuchi-cho, Higashi-ku, Osaka City Minolta Inside Camera Co., Ltd. 0 Inventor Toru Matsui Inside Osaka Kokusai Building Minolta Camera Co., Ltd. 2-30 Azuchi-cho, Higashi-ku, Osaka

Claims (1)

[Scope of Claims] 1. It has a large number of micro optical members arranged behind the imaging lens, and a pair of light receiving elements arranged adjacent to each other behind each micro optical member, In a focus detection device that detects the focus of an imaging lens based on the outputs of a large number of light-receiving element pairs, a light projector is provided that emits a light beam from behind the imaging lens toward the focus detection target via the imaging lens. In addition, between the pair of light-receiving elements constituting each of the light-receiving element pairs, there is a shape and a shape so that the pair of light-receiving elements do not receive the light beam emitted from the light projecting means and reflected by the imaging lens. A focus detection device characterized by having a blind portion of a certain size. 2. The light projecting means is configured to emit a small diameter parallel light beam centered on the optical axis of the imaging lens from behind the imaging lens. The focus detection device described. 3. The focus detection device according to claim 1 or 2, wherein the light projecting means emits an infrared beam. 4. The focus detection according to any one of claims 1 to 6, wherein the dead part has a circular shape arranged to span the pair of light receiving elements. Device. 5. Claims 1 to 5, characterized in that the dead part is arranged to span the pair of light receiving elements and has an oval shape extending in the arrangement direction of the pair of light receiving elements. The focus detection device according to any one of items 3 to 3. 6. A pair of second light-receiving elements is disposed in the dead part of each light-receiving element pair, and the output of the second light-receiving element pair is also used for focus detection when the light projecting means is turned off. A focus detection device according to any one of claims 1 to 5.