JP2643453B2 - Projection system for automatic focus detection - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a light projection system for automatic focus detection suitable for a photographic camera, a cine camera, a video camera, and the like, and in particular, projects a pattern on a subject side by the light projection system. In the passive and active automatic focus detection suitable for detecting the focus of the photographing system by receiving the pattern reflected from the object side, the fine and good pattern image is sufficiently far away. In addition, the present invention relates to a compact projection system for automatic focus detection that can project over a wide range.

(Prior Art) Conventionally, various automatic focus detection devices have been proposed for photographic cameras, cine cameras, video cameras and the like.

Among them, for example, in Japanese Patent Publication No. 49-19810, focus detection is performed by projecting a pattern from a camera side to a subject side by a light projecting system and detecting a reflection pattern from the subject side. This method has an advantage that the focus can be detected accurately even when the subject side is dark or when the contrast of the subject is low.

FIG. 6 and FIG. 7 are schematic views of main parts of a conventional light projecting system for automatic focus detection of this kind.

In FIG. 6, 101 is a light projecting lens, and 102 is a pattern, which is arranged near the focal plane of the light projecting lens 101. 103 is an LED having a dome for condensing light, and 104 is a light emitting unit of the LED 103.

In FIG. 7, reference numeral 111 denotes a light projecting lens, and 112 denotes a pattern arranged near the focal plane of the light projecting lens 111. 113 is
It is an LED and has a light emitting section 114 in a transparent resin.

Conventionally, a focus is detected in a photographing system by projecting a pattern onto a subject using a light projecting system configured as shown in FIGS. 6 and 7, and detecting a reflection pattern from the subject by a detection system. .

In general, the following items are required for a light projection system for automatic focus detection.

(A) A pattern image can be projected on a subject as far away as possible. To this end, the aperture of the light projecting lens should be made sufficiently large and the aperture can be used effectively.

(B) In a projection system for automatic focus detection of a camera whose lens can be exchanged, a pattern image is projected within the distance measurement field of view even when a distance lens is attached and the distance measurement field is narrowed. To do so, the pattern must be sufficiently fine.

(C) In a light projection system for an automatic focus detection device capable of measuring a distance at a plurality of points, a pattern image can be projected on a subject in a sufficiently wide range corresponding to the plurality of points. To this end, the focal length of the light projecting lens must be sufficiently short, and the imaging magnification of the pattern must be increased.

(D) A good pattern image can be formed on a subject surface in order to improve focus detection accuracy.

(Problems to be Solved by the Invention) In the conventional light projecting system shown in FIG. 6, the distance between the light projecting lens 101 and the pattern 102 must be sufficiently long in order to make the pattern image reachable sufficiently long. , Pattern 102 and light emitting unit 104
Needs to be sufficiently short. However, in such a configuration, there is a problem that the projection range of the pattern image is narrowed due to a long focal length of the light projecting lens, and a problem that it is difficult to make the light projecting system compact. come.

There is also a method in which the light projecting lens is constituted by a plurality of lenses, the focal length of the light projecting system is shortened, and the projection range of the pattern image is widened while sufficiently maintaining the reach of the pattern image. In this case, the angle of the light beam emitted from the pattern becomes extremely large, which makes it difficult to correct the aberration of the light projecting system, resulting in a problem that a good pattern image cannot be obtained, and the positional accuracy of the light emitting portion becomes extremely severe, making the production difficult. Problem arises.

On the other hand, in the light projecting system shown in FIG. 7, since the pattern 112 is provided on the light emitting section 114, the opening of the light projecting lens 111 can be effectively used, and therefore, the distance of the pattern image can be reduced. It can be made long enough. However, when creating the pattern 112 on the light emitting unit surface,
It becomes difficult to miniaturize the pattern. For this reason, it becomes difficult to project a fine pattern on the subject. Further, since the pattern is provided only on the light emitting portion, there is a problem that it is difficult to widen the projection range of the pattern image.

The present invention can project a fine and good pattern to a sufficiently long distance and a wide range of objects by appropriately configuring a light projecting system including a light projecting lens, a pattern, and an illuminating means, and achieve a high-precision focus. It is an object of the present invention to provide a compact light projection system for automatic focus detection capable of detection.

(Means for Solving the Problems) The light-projecting system for automatic focus detection of the present invention projects a fixed pattern illuminated by the illuminating means onto the object side by a light-projecting lens, and reflects the pattern reflected from the object side. When detecting the focus of the photographing system by receiving the pattern by the light receiving system, the light projecting lens includes a first lens having a positive refractive power in order from the object side and a second convex-shaped second lens having a convex surface facing the object side. The illumination means has a light emitting portion filled with a transparent resin on the object side, the second lens and the pattern, and the illumination means is provided with a refractive index of the material of the second lens and the transparent resin. It is characterized in that it is integrally formed by bonding with a transparent adhesive having a refractive index substantially equal to that of the transparent adhesive.

(Embodiment) FIG. 1 is a schematic diagram of an optical system according to an embodiment when the present invention is applied to a part of a photographing system.

In the figure, reference numeral 11 denotes a photographing system, 12 denotes a light projecting system, 13 denotes a detection system when the focus detection system is an active system, 14 denotes an image forming surface, and 18 denotes a focus detection unit when the focus detection system is a passive system.

In practice, either the active method or the passive method is adopted.

 FIG. 2 is an enlarged explanatory view of the light projecting system 12 according to the present invention.

In the same figure, reference numeral 15 denotes a light projecting lens, the first lens 1 having a positive refractive power with both lens surfaces being convex, and the lens surface on the object side being convex and the lens surface on the light source side (pattern side) being substantially flat. And a second lens 2 in the shape of a circle. Numeral 3 is a pattern made of a predetermined pattern. Reference numeral 4 denotes an illuminating means, which has a configuration in which a light emitting unit 5 is provided in a transparent resin made of an LED or the like.

In this embodiment, the second lens 2, the pattern 3, and the LE
D4 is integrated in this order with a transparent adhesive having a refractive index substantially equal to the refractive index of the material of the optical member.

By configuring the light projecting system in this manner, the focal length of the entire light projecting system can be shortened while making full use of the aperture of the first lens, and as a result, the pattern 3 can be projected over a long distance and a wide range of subjects. I can do it.

In this embodiment, it is preferable that at least one of the first lens 1 and the second lens 2 is provided with an aspherical surface, since the optical performance of the projection pattern can be maintained satisfactorily.

The detection system 13 includes a light receiving lens 16 and a light receiving element 17, and forms, for example, a light beam emitted from the light projecting system 12 and reflected by the subject and returned (in this case, the pattern 3 is omitted) or a pattern image. The focus of the imaging system 11 is detected by the detection.

The focus detection unit 18 detects an image signal related to a subject image obtained through the imaging system 11, or detects a reflection pattern image of the pattern 3 projected toward the subject from the light projecting system 12 when the subject is dark, The focus of the imaging system 11 is detected by a known method.

3 to 5 are explanatory views showing the optical operation of the light projecting system in the present invention.

FIG. 3 is an enlarged view of the vicinity of the pattern 3 in FIG. 2, and FIG. 4 is a case where minute air gaps are provided between the second lens 2 and the pattern 3 and between the pattern 3 and the LED 4 in FIG. FIG. 5 is an enlarged view of the vicinity of the pattern in FIG. In the respective drawings, the same members are denoted by the same reference numerals.

In the case where an air gap is provided between the second lens 2 and the pattern 3 while fully utilizing the opening of the first lens 1 as shown in FIG. 4, as shown in FIG. The angle of the emitted light beam becomes large, and when the light beam emitted from the pattern 3 is incident on the second lens 2, aberration is easily generated due to the difference in the refractive index between the air layer and the optical member. On the other hand, when the second lens 3 and the pattern 3 are bonded with a transparent adhesive having a refractive index substantially equal to those of the optical members as in the present invention shown in FIG. Can be reduced.

When an air gap is provided between the pattern 3 and the LED 4 as shown in FIG.
In order to make full use of the aperture of the first lens 1 as shown in FIG.
Disadvantageously, the size of the light emitting section 5 must be increased.

Also, in this case, if there is an error in the position of the light emitting unit 5 of the LED 4 with respect to the first and second lenses 1 and 2, the opening of the first lens 1 cannot be fully utilized, and the reach of the pattern image becomes shorter. It becomes easier to shorten. For this reason, it is necessary to make the position accuracy of the light emitting unit 5 of the LED 4 stricter.

On the other hand, the light projecting system for automatic focus detection according to the present invention shown in FIG. 2 bonds the second lens 2, the pattern 3 and the LED 4 to each other with a transparent adhesive having substantially the same refractive index. This makes it easy to project a good pattern image onto a long-distance subject.

In this embodiment, the pattern 3 may be made of any material as long as it is a transparent member. Therefore, the degree of freedom in selecting the material is far greater than when a pattern is provided on the light emitting portion 5 of the LED 4. In many cases, it has such features that a fine pattern can be easily obtained.

In the above embodiment, the aperture of the light projecting lens is proposed in, for example, Japanese Patent Application No. 63-256312 (Japanese Patent Application Laid-Open No. 2-101412) or Japanese Patent Application No. 63-256313 (Japanese Patent Application Laid-Open No. 2-101413). The pattern image may be divided into a plurality of regions having different refraction directions, a plurality of pattern images may be formed on the subject, and the pattern image may be projected on a wider range of subjects.

Further, the lens surface on the pattern side of the second lens is formed as a flat surface to facilitate adhesion, but may have a curvature,
This is preferable for aberration correction.

(Effects of the Invention) According to the present invention, as described above, a part of the light projecting lens, the pattern, and the illuminating means are integrally formed with a transparent adhesive having a predetermined refractive index, so that a fine and favorable structure is obtained. A projection system for automatic focus detection that can project a pattern image sufficiently far and on a wide range of subjects and enables highly accurate focus detection can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of an optical system according to an embodiment when the present invention is applied to a part of a photographing system, FIG. 2 is an explanatory diagram of a light projecting system 12 of FIG. 1, and FIG. 2, 4 and 5 are explanatory diagrams for comparison with the present invention, and FIGS. 6 and 7 are schematic diagrams of a conventional light projecting system. In the figure, 11 is a photographing system, 12 is a light projecting system, 13 is a detecting system, 14 is an image forming surface, 15 is a light projecting lens, 1 is a first lens, 2 is a second lens, 3 is a pattern, and 4 is illumination means. Reference numeral 5 denotes a light emitting unit, and reference numeral 18 denotes a focus detection unit.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-291511 (JP, A) JP-A-62-17717 (JP, A) JP-A-62-145228 (JP, A) JP-A 63-145228 78133 (JP, A)

Claims (1)

(57) [Claims] When detecting a focus of a photographing system by projecting a pattern of a fixed pattern illuminated by an illuminating means onto a subject by a light projecting lens and receiving the pattern reflected from the subject by a light receiving system. The light projecting lens includes a first lens having a positive refractive power and a second convex lens having a convex surface facing the subject in order from the subject side, and the illuminating means fills the subject side with a transparent resin. The second lens, the pattern, and the illuminating means are bonded together by a transparent adhesive having a refractive index substantially equal to the refractive index of the material of the second lens and the transparent resin. A light projection system for automatic focus detection, characterized in that it is configured.