JPH0583884B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical field to which the invention is directed] This invention relates to a light projection optical system for guiding a light beam projected from a halogen lamp to a light guide constituted by a bundle of optical fibers. can be applied.

[Prior Art] Because halogen lamps emit light that is very close to white light due to their nature, they are preferably used for more accurate color recognition, but as shown in FIG. Since it is on the optical axis, it has a reflecting section 2 usually made of a concave mirror, and this reflecting section efficiently reflects the light in front of it.

In this figure, since only an elbow-sized amount of light exists near the optical axis near the lamp 1, the light amount distribution becomes as shown in FIG. 4A. On the other hand, as shown in Figure B, a light spot with a large amount of light is obtained near focal point b, but since the angle between each ray and the optical axis is the same as in other parts, a light guide consisting of an optical fiber bundle is placed at that point. When the end of the light guide is placed, the light projection spot from the other end of the light guide also becomes annular.

Incidentally, as the distance from the focal point b on the optical axis of the lamp 1 increases, the luminous flux distribution changes as shown in FIG. 4C and D.

Therefore, in order to avoid the phenomenon that the shape of the light emitting spot becomes annular, a convex lens 11 is arranged on the optical axis of the lamp 1 at a position far from the focal point, as shown in FIG. The light beam corrected to almost parallel light is sent to the light guide 3.
There is a method of letting the light enter the focal point, or a method of arranging a concave lens 12 at a position before the focal point, as shown in FIG. 6, for the same purpose.

[Problems to be solved by this invention]

In the case of the device shown in FIG. 5 or 6, it is necessary to hold the lenses 11 and 12, and the structure, especially the manufacturing process, becomes complicated, and as the number of parts increases, it becomes difficult to assemble them into a device. However, its structure also has the disadvantage of being larger overall.

[Purpose of the invention]

This invention takes into consideration these conventional drawbacks,
In particular, the purpose is to obtain a uniform light projection spot onto a light guide without using high-precision optical parts such as lenses.

[Structure of the invention]

In order to achieve this object, the present invention is arranged such that one end of the light guide is located inside the focal point of the halogen lamp.

Additionally, a heat ray attenuation filter is provided between the halogen lamp and the light guide, and a reflective mirror is provided on the surface of this filter on the halogen lamp side. It is formed.

On the other hand, on the optical axis of the halogen lamp, a convex mirror is provided closer to the halogen lamp than the reflecting mirror and guides the light reflected by the reflecting mirror to the light guide through the transmitting part.

[Action of the invention]

The light beam emitted from the halogen lamp is reflected twice by the reflecting mirror and the convex surface, making the light incident on the light guide more uniform.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

That is, in FIGS. 1 and 2, a halogen lamp 1 has a reflecting section 2 made of a concave mirror. Further, the light guide 3 is constituted by a plurality of optical fibers, that is, a bundle of optical fibers. The light guide is arranged on the optical axis of the halogen lamp 1 such that one end thereof is located closer to the halogen lamp than the focal point b of the light beam from the halogen lamp 1.

A heat ray attenuation filter 4 is provided between the halogen lamp 1 and the light guide 3 to attenuate the heat rays generated by the halogen lamp 1. A planar reflecting mirror 5 is formed on one surface of this filter, that is, on the halogen lamp 1 side. Note that this reflecting mirror is provided on the heat ray attenuation filter 4 by vapor deposition, by attaching a separately formed member, or by other means. A transmitting portion 6 having a diameter larger by a predetermined dimension than the effective diameter of the light guide is formed in the reflecting mirror at a portion corresponding to the end surface of the light guide 3.

Also, on the optical axis L1 of the halogen lamp 1,
A convex mirror 7 having a diameter approximately equal to the bulb diameter of the halogen lamp is provided closer to the halogen lamp than the reflecting mirror. The curvature of this convex mirror is set so that the light emitted from the halogen lamp 1 and reflected by the reflecting mirror 5 is guided to the light guide 3 through the transmitting section 6.

As shown in FIGS. 1 and 2, the light rays emitted from the halogen lamp 1 are reflected by the reflecting mirror 5 toward the halogen lamp 1, further reflected by the convex mirror 7 toward the reflecting mirror 5, and then passed through the transmitting section 6. The light is incident on one end of the light guide 3. Light guide 3 here
It is necessary that the incident angle θ2 of the light beam relative to the halogen lamp 1 is smaller than the exit angle θ1 from the halogen lamp 1.

In an embodiment of the invention, a halogen lamp 1
If the aperture diameter of the reflecting section 2 is 34 mm, and the distance from the aperture of this reflecting section to the focal point b is 36 mm, then the diameter of the reflecting mirror 5 is 20 mm, the diameter of the transmitting section 6 is 4 mm, and the diameter of the convex mirror 7 is 7mm, its radius of curvature is 20mm, reflective part 2
The distance on the optical axis from the aperture to the convex surface of convex mirror 7 is 6.05 mm, and the distance between reflecting mirror 5 and convex mirror 7 is
11.95mm and the diameter of light guide 3 is 3.5mm, the light from halogen lamp 1 will pass through light guide 3.
Therefore, an annular light projection spot does not occur.

Here, it is necessary that the incident angle θ2 of the light beam to the light guide 3 is smaller than the exit angle θ1 of the light beam from the halogen lamp 1, as shown in FIG.

〔Effect of the invention〕

In this invention, as described above, a reflecting mirror is formed on the surface of the heat ray attenuation filter on the halogen lamp side, and a convex mirror facing the reflecting mirror is provided on the optical axis of the halogen lamp on the optical axis of the halogen lamp. The light is reflected toward the halogen lamp by a reflecting mirror, and then this reflected light is further reflected by a convex mirror, and then guided to one end of the light guide through a transmission section (heat ray attenuation filter) provided on the reflecting mirror. Since the angle of incidence of the light beam on the light guide is compressed compared to when it is directly incident from a halogen lamp, the resulting light spot at the other end of the light guide is more uniform. In addition, since a reflecting mirror and a convex mirror are combined to obtain a uniform light emitting spot, the configuration is simple, and in particular, it can be achieved without using expensive optical parts as in the past. High efficiency can be obtained at the same time.

Furthermore, the combination of a reflecting mirror and a convex mirror can shorten the distance between the halogen lamp and the light guide on the optical axis of the halogen lamp, that is, the total length of the optical system.

Note that since the light projecting optical system in this invention is a reflective optical system, another feature is that it does not cause chromatic aberration when used in a color detection device.

[Brief explanation of drawings]

FIG. 1 is a side view showing an embodiment of the light projecting optical system according to the present invention, FIG. 2 is a side view illustrating the process in which the light rays emitted from the halogen lamp reach the light guide in FIG. 1, and FIG. FIG. 4 is a side view showing a light projection curve of a general halogen lamp, FIG. 4 is a characteristic curve diagram at each point in FIG. 3, and FIGS. 5 and 6 are side views showing a conventional light projection optical system. 1...Halogen lamp, 2...Reflector, 3...
Light guide, 4... Heat ray attenuation filter, 5...
...Reflector, 6... Transmissive part, 7... Convex mirror.

Claims (1)

[Claims] 1. A halogen lamp having a reflective part, a light guide composed of an optical fiber bundle, and a heat ray attenuation filter provided between the light guide and the halogen lamp to reduce heat rays to the light guide. One end of the light guide is disposed closer to the halogen lamp than the focal point of the light beam from the halogen lamp, and a reflecting mirror is formed on the surface of the heat ray attenuation filter on the halogen lamp side, and the reflecting mirror is A transmitting portion having a diameter larger by a predetermined dimension than the effective diameter of the light guide is formed in a portion corresponding to the end surface of the light guide, and further, on the optical axis of the halogen lamp, a transmitting portion is formed on a portion corresponding to the end surface of the light guide. A light projecting optical system characterized in that a convex mirror is provided near the halogen lamp to guide light emitted from the halogen lamp and reflected by the reflecting mirror to the light guide through the transmitting portion.