JPS62247312A - Floodlighting system for automatic focus detection - Google Patents

Abstract

PURPOSE:To obtain a highly accurate floodlighting system for automatic focus detection having expanded rangefinding limits by constituting a floodlighting lens of plural lens parts of deviated optical axes and thereby enlarging the extent of projection of a pattern image efficiently to the nearest side. CONSTITUTION:A floodlighting lens 2 is provided with a lens part 23 having an optical axes 21 and a lens part 24 having an optical axis 24. A pattern image 3 is projected by the two lens parts 23, 24 of the floodlighting lens 2 in different directions. For instance, the lens part 23 projects the pattern image 3 in an extent shown by solid lines, and the lens part 24 projects the pattern image 3 in an extent shown by dotted lines which is deviated from the extent of projection by the lens part 23. Thus, by expanding the extent of projection of the pattern image 3, projection of the pattern image on the object face is made possible even when the object moves from a long distance to very short distance.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a light projection system for automatic focus detection that is useful for photographic cameras, cine cameras, video cameras, etc. Improves focus detection accuracy by passive and active automatic focus detection KJP suitable for performing focus detection in a photographic system by projecting light to the side and receiving the pattern that is reflected from the subject side. This invention relates to a light projection system for automatic pointless detection.

(Prior Art) Conventionally, two main focus detection methods have been used in photographic cameras, video cameras, and the like.

One is the passive method proposed in, for example, Japanese Patent Application Laid-Open No. 159259/1982.
This is an active method proposed in Publication No. 7-154206 and the like.

Among these, the active method detects focus by emitting, for example, infrared light from the camera side toward the subject and receiving the reflected light from the subject, even when the subject is dark or when the contrast of the subject is low. It has the advantage of being able to perform focus detection with high precision. However, when the subject is far away, the amount of reflected light flux decreases and the focus detection F1
There is a drawback that the temperature decreases by 1 degree.

The passive method is a method that detects the focal point by detecting the imaging state of the subject image by the imaging system using a detection means installed in a part of the camera. It has the advantage of being able to detect focus. However, there is a drawback that focus detection accuracy decreases when the subject side is dark or when the contrast of the subject is low.

One method to improve this drawback is, for example,
This is proposed in Publication No. 10. In this publication, focus detection is performed by projecting a pattern image of a certain pattern from the camera side to the subject side using a light projection system and detecting the reflected pattern image from the subject.

However, in this method, if the amount of projected light is small, the distance that the pattern image can reach is limited, so a light projection system with a large amount of light is required.

However, when the light projection system projects a pattern image and receives the reflected pattern 7 images reflected from the 1st subject side, unless the light is projected through the 1st photographing system, that is, if the light is not projected at TTL, the distance to the subject will change. So-called parallax occurs.

As a result, in the case of non-TTL, there is an inconvenience that the range of distance #l over which the image of the putter 7 can be projected is limited. For example, if you narrow down the projected light beam to increase the illuminance on a distant subject and then try to project it onto a nearby or distant subject, the pattern image may not be projected onto the subject due to parallax. As a result, focus detection may become difficult.

(Problems to be Solved by the Invention) The present invention appropriately arranges each element of a light projection system having a fixed pattern image and efficiently projects the pattern image in the direction of one subject. It is an object of the present invention to provide a light projection system for automatic focus detection suitable for both passive and active methods, which can be enlarged and can perform good distance measurement even in dark places or with low-contrast objects.

(Means for solving the problem) A constant pattern image is projected onto the subject side using a projection lens, and the cough pattern image reflected from the subject side is received by the light receiving system to detect the focus of the photographing system. @1 The above-mentioned light projecting lens is made up of a plurality of lens parts whose optical axes are shifted.

The features of this pond water invention are described in Example i.

(Practical) FIG. 1 is a schematic diagram of an optical system according to an embodiment when applied to a part of the t-imaging system of the present invention.

In the figure, 1 is the photographing system, 2 is the light projection lens, and 3 is the pattern image 14.
The light source 15 is an image forming surface, and the light receiving lens 17 is a light receiving element.

As shown in FIG. 2, the projection lens 2 has two lenses St, a lens part 2 having an optical axis 21 and a lens s24 having an optical axis 22'. In this example, the lens f! 623 and the lens s2/4 are configured to have approximately the same focal length, that is, the same refractive power, but they may be configured to have different refractive powers.
It is possible to provide three or more lenses. The two lenses @23 and 24 of the light projecting lens 2 project pattern images 3t in different directions.

In this embodiment, the pattern image 3t illuminated by the light source 4 is projected by the projection lens 2 in 92 different directions on the subject side. For example, the lens part 2 projects the pattern image 3 within the range shown by the solid line 1, and the lens s24 projects the pattern image 3 within the range shown by the dotted line, which is shifted from the projection range by the lens part 1.
is projected.

By expanding the projection range of the putter/image 30 in this manner, it is possible to project the pattern image onto the object surface even if the object is displaced from a distant place to a close distance.

Then, the reflection pattern image reflected from the subject side is guided to the light receiving element 7 through the photographing system 1 or through the upper light receiving lens 6 installed near the photographing system 1 as shown in FIG. The distance to the subject is measured using the output signal from the camera 7, and the focusing lens # in the photographing system 1 is moved to focus.

FIG. 3 is an explanatory diagram of a projected pattern image on the subject side of the pattern image according to this embodiment. In the figure, 31 is a projected pattern image by lens section 4, and 32 is a projected pattern image by Fi lens section λ. The projection pattern image 31 corresponds to when the subject is far away, and the projection pattern image 32 corresponds to when the subject is close.

Generally, when the subject is far away, high illumination is required, so
In this embodiment, the projected effective area of the lens s23 is the lens 1I.
It is larger than s24.

In this embodiment, the refractive powers of the lens portion n and the lens portion U are approximately equal, and the projected pattern images are projected with approximately the same size. Also, because of this, even if the object is located at an intermediate distance, the projected pattern images of both lenses are K is used so that the images overlap, and the projection of the Watashibatan image is performed well over the entire shooting distance.

Incidentally, in the projection lens 2 shown in FIG. 2, the lens surface 23b and the lens surface 24bt may be constructed from the same lens surface, and the optical axes of the lens surface 23m and the lens surface 24a may be shifted from one another.

Furthermore, the optical axis may be shifted in parallel, 4S or tilted.

The light projection system for automatic focus detection described above can be suitably applied to either a passive method or an active method.

(Effects of the Invention) A floodlight system for high-precision automatic focus detection that efficiently expands the projection range of one pattern to the close side and expands the measurable distance range by configuring as described above. can be achieved.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an optical system of an embodiment when applied to a part of a 1m shadow system of the present invention, Fig. 2 is a cross-sectional view of the projection lens of Fig. 1, and Fig. 3 is a lens sectional view of the projection lens shown in Fig. 1. The following is an explanatory diagram of a projected pattern image in this embodiment. In the figure, 1 is the photographing system 12, the light projecting lens, 3 is the pattern image, 4 is the light source 15, the imaging plane, 6 is the light receiving lens, 7 is the light receiving element S21.22 is the optical axis 31-3
2 are projection pattern images. Akira 1 Kuchikai 2 Diagram

Claims (2)

[Claims] (1) When detecting the focus of the photographing system by projecting a pattern image of a certain pattern onto the subject side using a light projecting lens and receiving the pattern image reflected from the subject side by the light receiving system, the light projecting lens is A light projection system for automatic focus detection, characterized by being composed of a plurality of lens sections whose optical axes are shifted. (2) The light projection system for automatic focus detection according to claim 1, wherein each of the plurality of lens sections is composed of lenses having substantially the same focal length.