JPS6280511A - Optical system for range finding - Google Patents

Abstract

PURPOSE:To simplify the constitution of an optical system by projecting spot light from a position at specific distance laterally from the optical axis of a photographic lens and photodetecting reflected light from an object through the photographic lens. CONSTITUTION:The projection optical system composed of a projection lens 11, etc., projects spot light from the position at distance laterally from the optical axis of photography and the direction of the projection is changed associatively with the forward/backward movement of the photographic lens 16. A two-division photodetector 15 consists of photodetecting element A and B and is arranged on a surface substantially equivalent to the image pickup surface of the lens 16. Consequently, the projection spot from the lens 11 is reflected by the object and incident on the lens 16. This incident light forms a photodetection spot image P on the sensor 15 through a mirror 18, etc. Then, the outputs of the elements A and B, etc., of the sensor 15 are compared with each other by an arithmetic circuit 50; when there is an output difference, the lens 16 is moved and put in focus and the projection system is associated 22 and 24 to move the spot light reflected by the object on the surface of the sensor 15 so that the outputs of the elements A and B coincide with each other. When both outputs coincide with each other, an in-focus state is decided.

Description

[Detailed Description of the Invention] [Industrial Field] The present invention relates to an optical system for measuring object distance, and more specifically, the present invention relates to an optical system for measuring object distance, and more specifically, it projects a spot light onto an object and separates the reflected light from the object by a certain baseline length. The present invention relates to an improvement in a distance measuring optical system that receives light with a light receiving optical system and determines whether or not it is in focus by comparing the outputs of a two-split optical sensor.

[Prior Art] FIG. 9 shows a conventional example of a distance measuring optical system. In this conventional example, a spotlight from a light emitting element 12 such as an infrared light emitting diode or a laser diode is directed onto a subject 1 by a light projecting lens 11.
3 to form a projected spot image on the subject 13. This reflected light is imaged on the two-split optical sensor 15 by the light-receiving lens 14 separated by a certain baseline length, and the outputs of the two-split optical sensor 15 are compared. The object distance can be detected by moving the two-split photosensor 15 so that the outputs of both elements A and B of the two-segment photosensor 15 match. That is, a focusing operation can be achieved by mechanically interlocking the two-split optical sensor 15 and the photographing lens.

FIG. 10 shows another conventional example. In this example, a beam splitter 17 is placed behind the shadow lens 16, a spot light is incident on the beam splitter 11 from the side, and the spot light is projected onto the subject via the photographing lens 16. Beam splitter 17 reflects only infrared light,
It is a cold mirror that transmits visible light.

[Problem to be Solved by the Invention J] In the conventional example shown in Fig. 9, both the light emitting system and the light receiving system are located laterally outside the photographing lens, so there is a drawback that the whole cannot be compactly assembled. Ta. Furthermore, when the light projector is fixed, there is also the drawback that parallax occurs at short distances.

The conventional example shown in Fig. 10 overcomes the drawbacks of the conventional example shown in Fig. 9, but requires a complicated optical system to project the distance-measuring light beam through the photographic lens. have shortcomings.

SUMMARY OF THE INVENTION An object of the present invention is to provide a distance measuring optical system with a simple configuration that solves the above-mentioned drawbacks.

[Means for Solving the Problems] The distance measuring optical system according to the present invention projects a spot light from a location spaced apart by a predetermined distance in the lateral direction from the optical axis of the photographing lens, and interlocks with the focusing operation of the photographing lens. a light projection optical system that changes the projection angle of the projected spot light; a two-split optical sensor that is located on a surface substantially equivalent to the imaging surface of the photographic lens and consists of two light receiving elements A and B; It consists of a light-receiving optical system that receives reflected light from a subject via the photographing lens and guides it to the two-split optical sensor.

Further, in the present invention, the light beam incident on the two-split optical sensor can be switched by using a switching plate having an opaque portion having an aperture fitted with a visibility correction filter and a filter portion for cutting visible light. . As a result, 2
The split light sensor can also be used for spot photometry.

[Examples] The present invention will be described below with reference to examples shown in the drawings. FIG. 1 shows the basic configuration of an optical system according to the present invention. In this embodiment, the carrier lens 1G is also used for receiving the distance measuring light beam, and the two-split optical sensor 15 is placed on the side of the imaging device (for example, on the film surface of an eye reflex camera). As a result, the light receiving optical system has an extremely simple configuration. The arithmetic circuit 50 is a circuit that compares the outputs of the two-split optical sensor 15 and moves the photographing lens 16 according to the comparison result.

The projection angle of the projected spot light is changed in conjunction with the focusing operation of the photographing lens 16 along the photographing optical axis. A broken line connecting the photographic lens 1G and the projected light in FIG. 1 represents an interlocking relationship. The mechanism itself for interlocking the back and forth movement of the photographic lens and the change in the projection angle is well known, so a description thereof will be omitted.

The amount of light that enters the optical sensor 15 as reflected light from the subject is proportional to the aperture area of the light receiving optical system.

Further, each output of the two-split optical sensor 15 is not related to the focal length of the light receiving optical system if the reflected light of the projected spot light does not protrude from the light receiving surface of the two-split optical sensor 15. In general, if the FL of the photographic lens is the same, the long focal length lens will be the same, and if the focal lengths are the same, the smaller the F number, the larger the aperture of the lens. This is consistent with the condition that requires more focus detection accuracy, that is, the need to be able to measure distances over longer distances.In this respect, the optical system with the above configuration according to the present invention is extremely rational. be.

FIG. 2 shows an embodiment in which the present invention is applied to an automatic focusing device for a single-lens reflex camera. The light projection lens 11 is designed to change its light projection direction in conjunction with the back and forth movement of the photographing lens 16 on the field optical axis, that is, the focusing operation. Specifically, a light emitting lens 11 and an infrared light emitting element 12 are fixed to the middle part of a lever 20 whose one end is rotatably supported on a lens housing, and a photographing lens 16 is fixed to the tip of the lever 20.
A protrusion 22 facing toward is provided. On the other hand, a wedge-shaped member 24 is fixed to the side surface of the photographic lens 16, and this wedge-shaped member 2
The protrusion of the lever 20 is urged against the curved surface of the lever 4. As a result, when the photographing lens 16 is moved back and forth, the lever 20 rotates around its support, changing the direction of the light projecting lens 11 and the infrared light emitting element 12, that is, the angle of the projected light.

The projected spot light directed from the projection lens 11 toward the subject is reflected by the subject and enters the photographic lens 16. This incident light passes through the first mirror 18 and is reflected by the second mirror 19, and is transmitted to the two-split optical sensor 15 disposed on the imaging equivalent plane.
A received light spot image is formed.

Of course, the wedge-shaped member 24 and the lever 20 are linked together so that the photographic lens 16 is in focus when the output of the two-split optical sensor 15 is balanced. Note that it is desirable that the first mirror 18 transmit 100% of infrared light, and that the second mirror 19 reflect 100% of infrared light.

Furthermore, it is desirable that the photographing lens 16 be coated to allow infrared light to pass therethrough as well. Furthermore, although it has been explained that the two-split optical sensor 15 is placed on the imaging equivalent plane, strictly speaking, the MGE lens 16 has chromatic aberration, and the focus position in the infrared region usually shifts slightly in the direction of increasing the focal length. be. Therefore, the position of the sensor 15 should be determined with this consideration in mind, and should be placed on the imaging equivalent plane at the wavelength of the distance measuring light beam.

In order to accommodate various types of interchangeable lenses, each interchangeable lens may be provided with a light projecting section that changes the projection angle of the projected light spot image in accordance with the focal length of the photographing lens 16. . Needless to say, in the case of a zoom lens, it is sufficient to satisfy the case of the longest focal length. In order to reduce the projection angle of the projection spot light, there are methods such as increasing the focal length of the projection lens 11 or reducing the light emitting surface of the infrared light emitting element 12.

FIG. 3 shows an example of the shape of the two-split optical sensor 15 in the present invention. In the present invention, the two-split optical sensor 15 is formed on the same day as the light-receiving element, and the boundary line between the two is perpendicular to the moving direction of the light-receiving spot image during a focusing operation. The light-receiving element A has a narrow foot-shaped portion 15a on the opposite side of the light-receiving element B.
The length in the moving direction of the light-receiving spot image excluding the foot-like portion 1'5a is large enough to receive the spot image (indicated by a broken line in FIG. 3) when in focus. The length of the light-receiving element B in the moving direction of the light-receiving spot image may be at least as long as it can receive the spot image in focus. Optical sensor 1 in a direction perpendicular to the moving direction of the light receiving spot image
The width of the lens 5 is also preferably large enough to receive a spot image when focused.

This sensor shape allows the received light spot image to partially protrude from the sensor 15 except when in focus.
The reason why such a configuration does not cause any problems will be explained with reference to FIG. 4. (A) in Figure 4 is
The image formation state of the projected spot light and its reflected light is shown when the subject is at a short distance and the photographic lens 16 is in focus. In this case, the spora on the sensor surface]
The image is off the optical axis of the photographing lens and is largely blurred on the sensor surface, resulting in a light-receiving spot image like the broken line drawn superimposed on the sensor 15 on the right side of FIG. Here, most of the light-receiving spot image is off the sensor 15, but this condition only occurs when the subject is sufficiently close. Therefore, although only a part of the light-receiving spot image is incident on the sensor 15, the sensor 1
5 produces sufficient power. When the output of element A of the two-split photosensor consisting of element A and element B is greater than that of element B, the photographing lens 16 is moved to the short distance side (the side in focus). Then, at the same time as the VAr lens is extended, the light projection system is mechanically linked to this focusing operation, and the spot light reflected by the subject passes through the state shown in FIG. 6 (B) on the surface of the optical sensor 15. Same (C
). In the state of (C) in Figure 6, element A
and the output of element B match, and it is determined that the state is in focus. The light receiving spora 1 to @ also come into focus on the sensor surface.

Next, consider a case where the focus of the carrier lens is located closer to the object distance than the object distance, as shown in FIG. 6(E). In this case, the light-receiving spot image is not incident on the optical sensor 15 at all. That is, both outputs of the optical sensor 15 are O. However, when constructing a light projecting type focus detection device, it is essential to control the Fukiage lens to move to the (1) side when there is no output from the optical sensor 15. Therefore, the IF lens 16 is controlled so as to inevitably go through the state shown in FIG. 6(D) and then into the focused state shown in FIG. 6(C).

FIG. 5 shows an embodiment in which the distance measuring optical system according to the present invention is used for exposed spot photometry. Here, the arrangement of the photographing lens 16, the first mirror 18, the second mirror 19, and the two-split optical sensor 15 is the same as that shown in FIG.

In this embodiment, a switching plate 31 is further arranged in front of the optical sensor 15 for switching the optical sensor 15 to use for exposure spot photometry. This switching plate 31 includes a filter portion 32 for cutting visible light to reduce the influence of ambient light when the optical sensor 15 is used for focus detection, and a spot photometry area when used for exposure spot photometry. It consists of an opaque part 34 having an aperture 33, and a visibility correction filter is installed in the aperture V-33.

This switching plate 31 can be slid laterally, and the mechanism for sliding the switching plate 31 connects the output of the optical sensor 15 to an automatic focusing calculation circuit, or to an exposure calculation circuit or a photometry circuit. It is linked to a circuit switching mechanism that switches between FIG. 6 shows a state in which the visible light cut filter portion 32 of the filter 31 is positioned in front of the optical sensor 15 when viewed from the second reflecting mirror 19 side.

In the above embodiment, the two-split optical sensor 15 is provided on the camera body side, but as shown in FIG. The reflected light from the subject may be guided to the optical sensor 15. This allows it to be configured independently as an autofocus lens.

Further, in the embodiment shown in FIG. 2, each interchangeable lens is provided with a light projecting section, but as shown in FIG. 8, the light emitting element 12 can also be arranged on the camera body side.

In this case, the distance measuring base length is lengthened by the mirror 35, the projection lens 1.1, and the movable mirror 36. The movable mirror 36 moves with the focusing operation to scan the projected spot light and change the projection angle. In order to change the projection angle according to the interchangeable lens, the focal length of the projection lens 11 may be changed according to the focal length of the @shadow lens.

[Effects of the Invention] According to the present invention, since the light-receiving optical system also serves as a photographing lens, a very simple optical system can be obtained.

Also, if the F number is the same, a long focal length lens will be used, but if the focal length is the same, the smaller the F number, the larger the effective aperture of the photographing lens will be. Since this conforms to the condition that distance measurement must be performed, it is possible to provide an optical system with an extremely rational configuration. Further, since the shape of the two-split optical sensor is minimized while taking advantage of such advantages, it is possible to provide a sensor with less influence of ambient light noise and dark current.

Furthermore, the optical sensor having this configuration can be easily used as a spot photometry sensor, and is extremely effective.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the basic configuration of an optical system according to the present invention. FIGS. 2 and 3 are diagrams showing an embodiment in which the present invention is applied to a single-lens reflex camera. FIG. 4 is a diagram illustrating the present invention in detail. FIGS. 5 and 6 are diagrams showing an example in which the optical sensor of the present invention can be used for exposed spot photometry. FIGS. 7 and 8 are diagrams showing other embodiments of the present invention. 9 and 10 show conventional examples. 11... Light projection lens 12... Infrared light emitting element 13
...Subject 14...Light receiving lens 15...Two-split optical sensor -6...Photographing lens 17...Beam splitter -18...First mirror 19...Second mirror 20... Lever 22...Protrusion 24...Horizontal member 31...Switching plate 32...Visible light cut filter portion 33...Aperture 34...Opaque portion 35...Mirror 36...Movable mirror
50... Arithmetic circuit 111 t Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7! Figure 8 Figure 9 Figure 10

Claims (10)

[Claims] (1) A projection optical system that projects a spot light from a location a predetermined distance laterally from the optical axis of the photographic lens and can change the projection angle of the projected spot light in conjunction with the focusing operation of the photographic lens, and a photographic lens. A two-split optical sensor, which is located on a plane substantially equivalent to the imaging plane of A ranging optical system characterized by comprising a light receiving optical system that guides the light to a light sensor. (2) The two-split optical sensor consists of a light-receiving element A and a light-receiving element B, which are divided by a line perpendicular to the moving direction of the light-receiving spot image by the light-receiving optical system, and one element A is connected to the other element B. The distance measuring optical system according to claim 1, further comprising a narrow foot-like light receiving surface extending in the direction of movement of the spot image on the opposite side. (3) The light-receiving optical system includes a first mirror that reflects most of the light beam transmitted through the photographing lens to another optical system and transmits a portion of the light beam that passes through the photographing lens except when shooting, and a photosensor that divides the light beam that has passed through the first mirror into two parts. A distance measuring optical system according to claim (1) or (2), comprising a second mirror facing toward. (4) The distance measuring optical system according to claim (3), wherein the transmission characteristics of the first mirror and the reflection characteristics of the second mirror transmit only infrared rays to the two-split optical sensor. (5) Claim (1) or (2), wherein the light receiving optical system is a beam splitter located behind the photographing lens, and the beam splitter is incorporated into a lens barrel. The distance measuring optical system described in Section 1. (6) A projection optical system that projects a spot light from a location separated by a predetermined distance in the horizontal direction from the optical axis of the photographic lens and can change the projection angle of the projected spot light in conjunction with the focusing operation of the photographic lens; A two-split optical sensor is located on a plane substantially equivalent to the imaging plane and is composed of two light-receiving elements A and B, and receives the light reflected by the subject of the projected spot light through the photographic lens, and receives the two-split light from the subject. It has a light receiving optical system that guides the light to the sensor, an opaque part that has an aperture fitted with a visibility correction filter, and a filter part that cuts visible light.
It consists of a switching plate that regulates the incident light flux to the two-split optical sensor, and when the two-split optical sensor is used for focusing, the visible light cut filter part of the switching plate is connected to the two-split optical sensor.
A measuring method characterized in that the aperture of the switching plate is moved in front of the light receiving surface of the split light sensor, and when the split light sensor is used for spot photometry, the aperture of the switching plate is moved to the front of the light receiving surface of the split light sensor. Distance optics. (7) The two-split optical sensor consists of a light-receiving element A and a light-receiving element B, which are divided by a line perpendicular to the moving direction of the light-receiving spot image by the light-receiving optical system, and one element A is connected to the other element B. The distance measuring optical system according to claim 5, further comprising a narrow foot-like light receiving surface extending in the direction of movement of the spot image on the opposite side. (8) The light-receiving optical system includes a first mirror that reflects most of the light beam transmitted through the photographing lens to another optical system and transmits a portion of the light beam that passes through the photographing lens except when shooting, and a light sensor that divides the light beam that has passed through the first mirror into two parts. A distance measuring optical system according to claim (6) or (7), comprising a second mirror that faces toward. (9) The distance measuring optical system according to claim (8), wherein the transmission characteristics of the first mirror and the reflection characteristics of the second mirror are such that only infrared rays are transmitted to the two-split optical sensor. (10) Claim (6), wherein the light receiving optical system is a beam splitter located behind the photographing lens, and the beam splitter is incorporated into the lens barrel.
or (7).