JPS6181084A - Light detecting device - Google Patents

Abstract

PURPOSE:To eliminate harmful light incident on a light detecting element by providing a light reflecting face consisting of plural retroreflectors in the container of the light detecting element and emitting light incident on the light reflecting face to the outside of the container from the port of incidence of the container. CONSTITUTION:A light detecting element 2 is contained in the container 1. Further, a light reflecting face consisting of plural retroreflectors is provided. Thus, light incident from a light incidence port 3 and does not arrive directly at a light detecting element is caught by the reflecting face 4 almost perfectly and reflected to the port of incidence 3 and emitted to the outside of the container.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention effectively eliminates reflected light within a container of a photodetector, which becomes background light that is harmful 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 imaging device, there is a strong demand for suppressing background light.

[Prior art and problems to be solved by the invention] Semiconductor photodetecting elements that convert optical signals into electrical signals include photovoltaic and MIS types, but in imaging devices, the light-receiving surface is usually a matrix. The photodetector element is provided in each pixel region, and the image of the object formed on the light receiving surface is photoelectrically converted for each pixel to form an image signal.

In a photodetecting device such as an imager, 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 where it 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 such bank ground 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 they have not yet achieved sufficient effects. .

(Means for solving the problem) The above problem is such that the photodetecting element is housed in a container, and the container is provided with a light reflecting surface composed of a plurality of retroreflectors, so that the light that is incident on the light reflecting surface is This problem is solved by the light detection device according to the present invention, which emits the light from the light entrance of the container to the outside of the container.

[For production]

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 above-mentioned harmful incident light does not directly reach the light receiving surface of the photodetecting element from the light entrance. is reflected in the direction of incidence by this light reflecting surface and emitted from the light entrance to the outside of the container.

As shown in FIG. 2(a), a retroreflector is a three-dimensional combination of three plane mirrors, usually square, at right angles to each other. The intersection line of these two planes - is X, Y,
Z axis, the intersection of these three axes is the origin 0, and this i
(7) u). 'J7u? ff(7)1c. +LZ). Oh.

The reflected light is reflected at a point B (-x
+ -L-Z) in a direction 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. 2(b), is an arrangement of fine retroreflectors, which 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 out of the container from the light entrance.

〔Example〕

The present invention will be specifically explained below using examples.

FIG. 1(a) 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, and 3
is a light entrance, 4 is the light reflecting surface according to the present invention,
In this embodiment, the cylinder is shaped like a cone or a polygonal pyramid. Further, 5 is a support that supports the light reflecting surface 4.
4) r As illustrated in the figure, the light enters from the light entrance 3 and directly i
The light that does not reach the photodetecting element 2 is almost completely reflected by the reflective surface 4.
The light is captured by the light incident port 3, reflected, and emitted outside the container.

Figure (b) shows a second embodiment of the present invention, in which equivalent parts are indicated 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-mentioned embodiment is formed by two-dimensionally arranging retroreflector structures of about 1 to 2 square mirrors on each side of the square mirror surface by a method such as driving a head or molding on the surface of a soft metal, plastic, or the like. , aluminum (A1
) can be formed by vapor deposition, plating, etc.

〔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 puncture ground light is removed, thereby expanding the dynamic range of the photodetector. , improvements in the output signal such as improved contrast and increased signal-to-noise ratio are achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic side sectional view showing an embodiment of the present invention, and FIG. 2 is a perspective view illustrating a retroreflector. In the figure, 1 is a container, 2 is a photodetector, 3 is a light entrance, 4 is a light reflection surface, and 5 is a light reflection surface support. Figure 1 <C> Figure 2 Cθ) 2

Claims (1)

[Claims] 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. Characteristic light detection device.