JPH0444871B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention effectively eliminates reflected light within a container of a photodetector, which becomes harmful background light to a photodetector, particularly input signal light. The present invention relates to a photodetecting device.

Many photodetecting devices are used to convert a modulated optical signal or an optical image into an electrical signal, and in the latter type of imaging device, suppression of background light is particularly strongly required.

[Problems to be solved by conventional technology and invention]

Semiconductor photodetectors that convert optical signals into electrical signals include photovoltaic and MIS types, but in imaging devices, the light-receiving surface is usually divided into a matrix of pixel areas, and each pixel area has a photodetector. A device is provided to photoelectrically convert an image of an object formed on a light-receiving surface for each pixel to form an image signal.

In a photodetecting device such as an imaging device, such a photodetecting element is usually housed in a vacuum container, and a target signal light is made to enter the photodetecting element through a light entrance provided in the container.

Of this incident light, when light that does not directly enter the light-receiving surface reaches the light-receiving surface indirectly after being reflected several times on the inner surface of the container, in most cases it is different from the pixel that should originally be incident. The light enters a pixel and becomes background light relative to the original signal light of the pixel, causing deterioration of the image signal such as reduction in dynamic range, reduction in contrast, and reduction in signal-to-noise ratio.

In order to suppress background light caused by reflection inside the container, conventional measures have been taken to reduce the reflectance of the inner surface of the container and limit the incident light flux, but these efforts have not yet been sufficiently effective. .

[Means for solving problems]

The problem is that the photodetecting element is housed in a container,
The problem is solved by a light detection device according to the present invention, which includes a light reflection surface made of a plurality of retroreflectors inside the container, and emits light incident on the light reflection surface to the outside of the container from a light entrance of the container.

[Function] The photodetecting device according to the present invention has a light reflecting surface composed of a fine retroreflector disposed inside the container, so that the light does not directly reach the light receiving surface of the photodetecting element from the light incidence opening. The incident light is reflected in the direction of incidence by the light reflecting surface and emitted from the light entrance to the outside of the container.

A retroreflector is, as shown in Figure 2a,
It is usually a combination of three square plane mirrors arranged three-dimensionally at right angles to each other. The intersection of these two planes is the X, Y, and Z axes, and the intersection of these three axes is the origin O, and one point A (x, y, z) of this retroreflector is
The reflected light of the incident light passes through a point B (-x, -y, -z) which is symmetrical with respect to the origin O, and is parallel to and opposite to the direction of incidence.

The light reflecting surface of the present invention, as shown in a schematic perspective view in FIG. 2b, is an array of fine retroreflectors, reflects incident light in the direction of incidence, and its position is hardly displaced. Therefore, the harmful incident light that has reached this light reflecting surface can be turned back, made to travel in the opposite direction, and emitted from the light entrance to the outside of the container.

〔Example〕

The present invention will be specifically explained below using examples.

FIG. 1a is a schematic side sectional view showing a first embodiment of the present invention. In the figure, 1 is a container, 2 is a photodetecting element, 3 is a light entrance, and 4 is the light reflecting surface according to the present invention, which in this embodiment is shaped like a cone or a polygonal pyramid. Further, 5 is a support that supports the light reflecting surface 4.

As illustrated in the figure, light that enters through the light entrance 3 and does not directly reach the photodetector element 2 is almost completely captured by the reflective surface 4, is reflected back to the light entrance 3, and is emitted outside the container. .

Figure b shows a second embodiment of the present invention, in which equivalent parts are designated by the same reference numerals as in figure a, and in this embodiment, the light reflecting surface 4 is a cylinder or a polygonal cylinder surface.

In this example, almost the same effect as in the previous example can be obtained, and the formation of the light reflecting surface 4 is easier than in the previous example.

Figures c, d, and e show other embodiments of the present invention, in which a light reflecting surface 4 according to the present invention covers all or part of the interior surface of the container 1. In these embodiments as well, as illustrated in the figures, harmful incident light is reflected by the light reflecting surface 4, thereby suppressing background light.

The light reflecting surface 4 of the above embodiment is formed by driving a head into the surface of a soft metal, plastic, etc., by molding, etc., so that one side of the square mirror surface is, for example, 1 to 2 mm.
It can be formed by two-dimensionally arranging a retroreflector structure of about 100 yen, and applying aluminum A1 vapor deposition, plating, etc. to the surface thereof.

〔Effect of the invention〕

As explained above, according to the present invention, harmful incident light that is reflected within the container of the photodetector and indirectly reaches the photodetector element and becomes background light is removed, and the dynamic range of the photodetector is improved. expansion,
Improvements in the output signal are achieved, such as improved contrast and increased signal-to-noise ratio.

[Brief explanation of drawings]

FIG. 1 is a schematic side sectional view showing an embodiment of the present invention;
FIG. 2 is a perspective view illustrating the retroreflector. In the figure, 1 is a container, 2 is a photodetecting element, 3 is a light entrance, 4 is a light reflecting surface, and 5 is a light reflecting surface support.

Claims (1)

[Claims] 1. The photodetecting element is housed in a container, and the container is provided with a light reflecting surface composed of a plurality of retroreflectors, and the light incident on the light reflecting surface is emitted from the light entrance of the container to the outside of the container. A light detection device featuring: