JPS61296220A - Detector for wide angle light emitting source - Google Patents

Abstract

PURPOSE:To make it possible to reduce a measuring error even if the light emitted from a wide angle light emitting source is detected by a minute caliber detector, by using a lens for converging the light emitted from the wide angle light emitting source to convert the same to parallel light and a lens for condensing said parallel light. CONSTITUTION:The optical arrangement of the lens 2 to a wide angle light emitting source 1 and that of the detector 5 to a lens 4 are made symmetric around a filter 3. Therefore, light having the same caliber as the light emitting source 1 can be detected by a light receiving surface 6. The filter 3 permits the incidence of light when the optical output of the light emitting source 1 is high output of +10dBm or more. Because the light passing through the filter 3 is parallel one, if the filter 3 is vertically inserted in parallel light, the incident angle of parallel light to the filter 3 becomes constant. Therefore, the effect in the incident angle characteristics caused by the filter 3 can be prevented.

Description

Detailed Description of the Invention (a1 Technical Field of the Invention The present invention focuses and detects light from a wide-angle light source with a large radiation spread angle without omission, and also detects light with a wide level range from minute output to high output. The present invention relates to a detector for a wide-angle light emitting source.

(b) Prior art and problems Recently, wide-angle light emitting sources with large radiation spread angles have been used, but when measuring the output level of such wide-angle light sources, it is difficult to measure the radiation spread angle from 80° to 120°. In order to detect the total amount of light from a wide-angle light emitting source, a detector with a large diameter light receiving surface is required.

However, a large-diameter detector increases dark current and noise in proportion to the light-receiving area, and is therefore unsuitable for detecting light of minute output.

Generally, in order to detect light with minute output, a detector with a light-receiving surface of a small diameter is used.

Next, a conventional technique in such a case will be explained with reference to FIG.

In FIG. 2, 1 is a wide-angle light emitting source, 5 is a detector, and 6 is a light receiving surface.

When detected using a small-diameter light-receiving surface 6 as shown in FIG. 2, a part of the light from the wide-angle light emitting source 1 cannot enter the detector 5, and a measurement error occurs due to the amount of light that cannot enter the detector 5.

Also, the level range of optical output that can be detected by the detector 5 is Od
Bm is normally +10'' dBm or less, and when light with a higher output than that is incident on the detector 5, the output of the detector 5 is saturated and becomes non-linear.

Therefore, the light output between the wide-angle light source 1 and the detector 5 is /[
A filter is installed to adjust the input level to the detector 5 so that the detector 5 does not become saturated.

However, using a filter for level adjustment has the following problems.

A metal evaporated film type filter is used for a filter with a precise amount of light loss, but since such a filter has an incident angle characteristic, if the angle of incidence of light to the filter is not constant, it will cause measurement errors.

(c) Purpose of the Invention The present invention is capable of detecting light from a wide-angle light emitting source with a large radiation slope angle in a wand shape with little measurement error, and even if a filter is used, An object of the present invention is to provide a detector for a wide-angle light emitting source that can detect light output with a wide level range without being affected by incident angle characteristics.

(Example of d1 invention First, a diagram of the principle of this invention is shown in FIG.

In FIG. 1, 1 is a wide-angle light emitting source, 2 and 4 are lenses, 3 is a filter, 5 is a detector, and 6 is a light receiving surface of the detector 5.

The present invention makes the optical arrangement of the wide-angle light emitting source lens 2, lens 4, and detector 5 symmetrical, so that the light emitting area of the wide-angle light source 1 and the light receiving area of the detector 5 are the same, The light incident on the filter 3 is made to be parallel light rays.

The lens 2 focuses the emitted light from the wide-angle light emitting source 1 having a large radiation angle into parallel light beams.

The filter 3 has the function of attenuating the level of the optical output that has become a parallel beam at the lens 2 by '14.

The lens 4 converts the parallel rays that have passed through the filter 3 into a light receiving surface 6.
Focus the light on.

The detector 5 detects the light focused on the light receiving surface 6.

It is better to use lenses 2 and 4 with the same focal length and lens diameter.

In FIG. 1, the optical arrangement of the lens 2 with respect to the wide-angle light emitting source 1 and the optical arrangement of the detector 5 with respect to the lens 4 are made symmetrical with respect to the filter 3.

Note that due to the size of the radiation angle of the wide-angle light emitting source 1, the size of the aperture of the filter 3, or the relationship between the focal lengths of lenses 2 and 4, 2
More than one lens may be used.

Usually, the diameter of the wide-angle light emitting source 1 made of a light emitting diode or laser diode is 50 μm or less, and the diameter of the light receiving surface 51 made of a light receiving diode is in the range of 100 μm to 300 μm.

Therefore, light having the same aperture as the wide-angle light emitting source 1 can be detected by the light receiving surface 6 of the detector 5.

The filter 3 is inserted when the wide-angle light emitting source 1 has a high optical output of +10 dBm or more.

Since the portion of the light that passes through the filter 3 is parallel rays, if the filter 3 is inserted perpendicularly to the parallel rays, the angle of incidence of the parallel rays on the filter 3 will be constant.

Therefore, it is possible to prevent the filter 3 from being influenced by the incident angle characteristics.

The filter 3 may be inserted anywhere in the parallel beams as long as it is inserted perpendicularly to the parallel beams.

Next, a configuration diagram of an embodiment according to the present invention is shown in FIG.

FIG. 3 shows lens 7 and lens 8 in contrast to lens 2 in FIG.
and lens 9 and lens 1 for lens 4 in Figure 1.
This uses o.

In other words, Figure 3 is an example in which two lenses are used for each lens in Figure 1, making it possible to deal with a light source with a larger radiation angle than when using one lens. It is.

In Figure 3, lens 7 and lens 1o have diameters l〇-■,
Use lenses with a focal length of 1o, lens 8 and lens 9.
A lens with a diameter of 20 m and a focal length of 20 mm is used.

Also, the distance between wide-angle light emitting IjX1 and lens 7, lens 10
and detector 5 are each 5*1, the distance between lenses 7 and 8, and the distance between lens 9 and lens LO is 10 each.
Make it into a seal.

(e) Effects of the Invention According to this invention, the light emitted from the wide-angle light source 1 is focused into parallel light beams. Since the lens 4 that condenses the light beam is used, measurement errors can be reduced even if the light emitted from the wide-angle light emitting source l is detected by the detector 5 with a minute aperture.

Further, by using filters 3 with different attenuation amounts between the lenses 2 and 4, it is possible to detect light outputs ranging from minute outputs to high outputs.

Furthermore, since the light entering and exiting the filter 3 is parallel, the filter 3 is no longer affected by the angle of incidence, and errors in the amount of attenuation caused by the filter 3 are reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is an explanatory diagram of the prior art, and FIG. 3 is a configuration diagram of an embodiment according to the present invention. 1...Wide-angle light source, 2...Lens, 3
...Filter, 4...Lens, 5...
...Detector, 6... Light receiving surface, 7-10...
····lens. Agent Patent Attorney Kin Tsukasa Omata #I l (8) Figure 2 Light receiving surface

Claims (1)

[Scope of Claims] 1. When the light from a wide-angle light emitting source is detected by a detector, a lens A that converts the light from the wide-angle light source into parallel rays, and a lens B that focuses the parallel rays on the light receiving element. , and a filter for entering the parallel light beam.