JPS61255302A - Optical device - Google Patents

Abstract

PURPOSE:To prevent occurrence of a blind sector, by respectively forming a lens section and reflecting surface at the central part and its circumference as the 1st surface, lens surface which condenses projected light and, at the same time, changes incident light to almost parallel light as the 2nd surface, and another lens surface which condenses incident light reflected by the reflecting surface as the 3rd surface. CONSTITUTION:An optical device 20 is equipped with three surfaces 21-23 and the 1st surface 21 has a lens section 21a at its central part and a reflecting surface 21b around the central part. The 2nd surface 22 is a lens surface which condenses projected light and, at the same time, changes incident light to almost parallel light. The 3rd surface 23 is a lens surface which condenses incident light reflected by the reflecting surface 21b. The reflecting surface 21b can be formed at a mirror surface by depositing a thin metallic film, etc., or to such a surface that reflects light by utilizing the total reflection of light. The lens section 21a and 2nd lens surface 22 have the same optical axis M and a light projecting element 1 is provided on the optical axis M on the lens section 21a side. An object to be detected O is put on the optical axis M. The optical axis N of the 3rd lens surface intersects the optical axis at the center of the lens section 21a and a photodetecting element 2 is provided on the optical axis N.

Description

DETAILED DESCRIPTION OF THE INVENTION Summary of the Invention Having at least three surfaces, the first surface has a lens portion in the center and a reflective surface formed around the lens portion, and the second surface focuses the projected light. An optical device characterized in that the third surface is a lens surface that converts incident light into substantially parallel light, and the third surface is a lens surface that condenses the incident light reflected by the reflective surface.

[Technical Field] The present invention relates to an optical device, and more particularly to an optical device effectively used as an optical system of a coaxial reflective optical detector.

[Prior Art] In a general reflective optical detector, the optical axes of the optical system of the light projecting section and the optical system of the light receiving section do not coincide.

This creates a so-called dead zone in the vicinity of the photodetector. FIG. 2 shows an example of a conventional coaxial reflective optical detector in which the dead zone is eliminated by aligning the optical axes of the transmitting and receiving optical systems. In this figure, a light projecting element 1 and a light projecting lens 11 are arranged so that the projected light is focused on an object to be detected 0 that is a predetermined distance away from a detector. Further, the light receiving element 2 and the light receiving lens 12 are arranged so that the object to be detected 0, which is separated by the predetermined distance, is imaged on the light receiving element 2. Role, light receiving lens L1. and the light projecting element 1 by setting the focal lengths of L2 to be different from each other.

The light-receiving probes 2 can be placed at different positions on the same optical axis.

Although it is possible to eliminate the dead zone near the photoelectric detector with such a configuration, a holding material (not shown) is required to hold the light emitting element 1 within the recess of the light receiving lens 12, and There was a drawback that the effective area of the light receiving lens 12 was reduced. Also.

If the projecting and receiving lenses 11 and 12 are integrally molded, a large concave portion must be formed in the receiving lens 12, which causes a problem of distortion in the receiving lens I2. If the projecting and receiving lenses 11 and 12 were made as separate parts, a holding material would be required to hold the projecting lens 11 within the receiving lens 12, and since the lenses are generally arranged on the outer surface of the photoelectric detector, this would be necessary. The holding material must also have a sealing effect, which causes the problem that the holding material becomes expensive.

Such a problem arises from a structural defect in arranging the light projecting element and the light receiving element on the same optical axis.

[Object of the Invention] An object of the present invention is to provide an optical device that can prevent the occurrence of a dead zone and solve the above-mentioned structural problems.

[Configuration and Effects of the Invention] In FIG. 1, the optical device 20 has three surfaces 21, 22 and 23. The first surface 21 has a lens portion 21a in the center and a reflective surface 21b around the lens portion 21a. The second surface 22 is a lens surface that condenses the projected light and converts the incident light into approximately parallel light. The third surface 23 is a lens surface that collects the incident light reflected by the reflective surface 21b.

The lens portion 21a may be formed integrally with the optical device 20 or may be formed separately.

Of course, the optical device 1f20 may be formed by dividing into several parts, and then these parts may be combined, or they may be arranged at an appropriate distance. The reflective surface 21b may be made into a mirror surface by depositing a metal thin film or the like, or may reflect light using total internal reflection.

The optical axes M of the lens portion 21a and the second lens surface 22 coincide with each other, and the light emitting cable l is located on the axis M and on the lens portion Zta side.
is placed. The object to be detected O is on the optical axis M. Further, the optical axis N of the third lens surface 23 intersects with the optical axis M at the center of the lens portion 21a. A light receiving element 2 is arranged on this front axis N.

The lens section 21a can be called a light projecting lens, the lens surface 22 can be called an objective lens, and the lens section 23 can be called a light receiving lens. However, the term "objective lens" here does not mean a general objective lens, but merely means that it faces the object O to be detected.

The projected light from the light projecting element 1 is transmitted through a lens section (light projecting lens) 21
It is converted into almost parallel light at point a. This parallel light is transmitted to the lens surface (
The light is focused onto the object O to be detected by the objective lens) 22.

The reflected light from the object to be detected O is converted into substantially parallel light by the lens section 22, reflected by the 9 reflecting surface 21b, and directed toward the lens surface (light receiving lens) 23. This reflected light is focused onto the light receiving cable 2 by the lens surface 23 and is received.

The optical axis M of the light projecting optical system does not coincide with the optical axis N of the light receiving optical system, but intersects with it at an appropriate angle. Therefore, it is not necessary to provide the light emitting element 1 and the light receiving element 2 on the same optical axis, and there is no need to provide four parts to the light receiving lens as in the conventional case.
There is also no need for a holding material for the light projecting lens, and adverse effects caused by these materials can be avoided.

Further, since only the second lens portion 22 faces the outside of the photoelectric detector, it is only necessary to seal the periphery of this lens portion 22 to the case, etc., making it easy to seal.

Although the optical axis N of the light-receiving optical system is different from the optical axis M of the light-emitting optical system, the incident light from the object to be detected O actually enters with the optical axis M of the light-emitting optical system as the optical axis. Therefore, there is no problem of a dead zone occurring in the nearby area.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional example. 20... Optical device, 21... First surface. 21a... Lens portion, 21b... Reflective surface. 22... second side, 23 river third side. that's all

Claims (1)

[Claims] It has at least three surfaces, the first surface has a lens section in the center and reflective surfaces around it, and the second surface condenses the projected light and converts the incident light into approximately parallel light. An optical device characterized in that the third surface is a lens surface that collects incident light reflected by the reflective surface.