JPS63151232A - Optical receiver - Google Patents

Abstract

PURPOSE:To constitute simply the processing circuit by utilizing a spherical lens and photodetectors independently of themselves placed near the said lens and split into plural light receiving faces. CONSTITUTION:An optical signal 1 made incident perpendiclarly to a photodetector face 5 is focused by a spherical lens 3 and the image is formed on the photodetector face 5 parted by a focus (f) in a form of a minimum circle of confusion 6 (radius r0). On the other hand, an optical signal 2 made incident with an angle 8 with respect to the optical signal 1 is focused by the spherical lens 3, forcused on a focus plane 4 and projected as an elliptic spot on the photodetector face 5. The elliptic photodetectors having a shape nearly equal to the projected shape are split and arranged around the photodetector 8 by taking the increase in the incident area to the photodetector face 5 due to the defocus component.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical receiver used in an optical space transmission system that transmits optical signals using space as a transmission medium, and in particular to a mobile type receiver used in a personal type. The present invention relates to an optical receiving device that can also be applied to an optical receiving device.

[Background of the Invention] Conventionally, this type of optical receiving device has a narrow communication angle, so its use is limited to cases where the position of the transmitting side is known in advance within a fixed range, such as in a stationary type or robot control. was. In order to enable application to random moving objects used on a personal level, it is necessary to widen the angle of view that can be received, and as a means of improving this, the use of fisheye lenses etc. and the light receiving element used in the optical system. Expansion of the light-receiving area is being considered.

However, the former has the disadvantage of being large and heavy, making it difficult to apply on a personal level, while the latter has the disadvantage of decreasing the response speed due to an increase in the junction capacitance of the light-receiving element.

[Objective of the Invention] The object of the present invention is to expand the angle of view that can be received by using a ball lens in the optical system in view of the problems of the conventional optical receiving device, and to An object of the present invention is to provide an optical receiving device that improves signal reproduction of light incident as an external light flux.

``Summary of the Invention'' The purpose of the following is to provide an optical receiving device that receives an optical signal and converts the optical signal into an electrical signal, the light receiving section of the optical receiving device comprising a condensing lens and the lens. and a light receiving element installed close to the lens and divided into a plurality of light receiving surfaces, each of which is independent, and a light spot formed on the light receiving element by the light incident on the lens as an off-axis beam. This is achieved by an optical receiving device characterized in that the area of each divided light-receiving surface of the light-receiving element increases from the center toward the periphery in accordance with the size of.

[Function] According to the optical receiver as described above, each light receiving element is divided in accordance with the spread of a light spot formed on the light receiving element by the light incident off the basic optical axis. This has the advantage of simplifying the processing circuit that processes the output of the light receiving element.

In other words, when multiple light receiving elements on one chip are arranged with equal size (for example, the light receiving elements are divided into grids), the peripheral area on one chip is The optical signal becomes defocused and enters a larger number of light-receiving elements than the center of the light-receiving element, and in order to compensate for this, the addition circuit of the processing circuit becomes complex, increasing the circuit size and increasing noise. However, in the case of the present invention, the light-receiving element is divided so that the area of each light-receiving surface becomes larger in accordance with the increase in the area of incidence on the light-receiving element surface due to the defocus component. can have a simple configuration.

[Example] Hereinafter, the optical receiving device of the present invention will be described in detail based on a specific example.

FIG. 1(a) is a schematic cross-sectional view showing an embodiment of the optical receiver of the present invention.

In the figure, 3 is a lens that condenses light in a wide angle range (a spherical lens in the case of the figure), 5 is a light receiving element surface, 1 is incident light (optical signal) that enters the light receiving element perpendicularly, 2 is incident light that enters the optical axis perpendicular to the light receiving element at an angle θ, 4 is the focal plane of the ball lens 3, f is the sunspot distance, and R is the radius of the ball lens 3. It should be noted that although there is actually nothing on the focal plane 4, this is for illustration purposes only.

The incident lights 1 and 2 containing optical signals are incident on the ball lens 3 and then on the light receiving element surface 5, where they are photoelectrically converted and reproduced as electrical signals.

FIG. 1(b) is a diagram showing a light spot formed on the light receiving element surface 5 by the incident light.

In the figure, an optical signal 1 incident perpendicularly on the light receiving element surface 5 is condensed by a ball lens 3 and the light receiving element surface 5 has a focal length gIf#.
A circle of least confusion 6 (radius ro) is imaged on the top. - The optical signal 2 incident at an angle θ with respect to the force tip signal 1 is condensed by the ball lens 3, focused on the focal plane 4, and then projected as an elliptical spot on the light receiving element surface 5''. .

In this way, the area of incidence on the light-receiving element surface 5 changes greatly depending on the incident angle of the optical signal, so if the light-receiving element is divided in a grid pattern, a complex processing circuit will be required depending on the variation in the incident area. It becomes necessary. Therefore, in the present invention, the light receiving element is divided and arranged in consideration of an increase in the area of incidence on the light receiving element surface 5 due to this defocus component.

In order to quantitatively determine the increase in the incident area, the optical signal 2 is shaped like a film and forms an ellipse 7 that is in contact with the distance 1111L from the center of the light receiving element surface 5 (the shortest position with respect to the spherical lens 3).
Let us consider the case where the light is incident on the ball lens 3. At this time, the angle of incidence θ can be expressed as follows: R: Radius of the spherical lens f: Focal length of the spherical lens.

In addition, the major axis a and the minor axis of the elliptical system 7 at this time are: becomes.

Based on the above results, the method of dividing and arranging the light receiving element of the present invention will be explained using FIG.

FIG. 2 is a plan view of the light receiving element surface 5. FIG.

First, for the optical signal l that is perpendicularly incident on the light receiving element surface 5, the radius rl is greater than or equal to the radius rO of the circle of least confusion (rl>ro)
A light-receiving element 8 is arranged. Next, the light receiving element 9 is arranged on concentric circles so as to encompass the diameter of the ellipse projected so as to be in contact with the light receiving element 8. At this time, the width of the light receiving element 9 is r
It is assumed that the major axis al of the ellipse projected so as to be in contact with l is obtained by (L=r 1) in equations (1) and (2). That is, the light receiving element 9 has an inner diameter rl and an outer diameter r2=rl+
The concentric circles of the light receiving element 8 are assumed to be al. Further, the light-receiving element 9 is 9-1°9-2. ......, angle division as 9-n.

Hereinafter, the outer light-receiving elements 10-1, 10-2, .・・・・・・
..., 1O-n (determined by major axis a2. minor axis b2. L=r2), and the outer light receiving element is also 11-1.11
-2.・・・・・・・・・・・・

They are sequentially divided and arranged as 1l-n (determined by L=r3: major axis a3. minor axis b3. L=r3).

Here, the sizes of rl, r2, and r3 are determined depending on the angle of view of the device and the number of divisions of the light-receiving element allowed.

The present invention is not limited to the above-mentioned embodiments, and various modifications and applications are possible.

FIGS. 3 and 4 are diagrams showing other examples of division of the light-receiving surface of the light-receiving element.

FIG. 3 is a diagram showing an embodiment in which an elliptical light-receiving element having a shape substantially equal to the projected shape of the divided light-receiving surface is developed in all directions with the light-receiving element 8 at the center. Further, FIG. 4 is a diagram showing a case in which the concentric circles in FIG. 2 are changed to a hexagonal shape. In this way, the method of dividing the light-receiving surface of the present invention is not limited to concentric circles.

Furthermore, in the above embodiment, it was explained that "frl is the circle of least confusion 10 or more" and the width of one concentric circle is equal to the major axis of the projected ellipse, but it should be set according to the circuit scale after the optical system, the response speed, etc. Therefore, the present invention can be practiced with settings other than those described above.

[Effects of the Invention] As explained above, according to the optical receiving device of the present invention, the combination of a wide-angle lens such as a spherical lens and a light-receiving element divided on a plane enables small size, light weight, high-speed processing, and The light-receiving system with an improved angle of view has a configuration that can be divided relatively easily on a plane, and the area of each light-receiving surface increases as the area of incidence on the light-receiving element surface increases due to the defocus component. Since the light-receiving element is divided into two parts, the conventional problem of complicating the circuit has been solved. Furthermore, the simpler circuit also contributes to noise reduction.

[Brief explanation of the drawing]

FIG. 1(a) is a schematic cross-sectional view showing an optical receiving device of the present invention,
Figure 1 (b) is a diagram showing the state of the light spot created on the light receiving element when incident light enters the device, and Figures 2 to 4
Each figure is a plan view of a light receiving element showing an example of division of the light receiving element. 1.2: Incident light 3: Lens that condenses light in a wide angle range (spherical lens in the case of Figure 1) 4: Focal plane of spherical lens 5: Light receiving element surface 6: Circle of least confusion (optical spora l -) 7: Elliptical spot 8.9, 10, 11: Split light-receiving element agent Patent attorney Jo Taira Yamashita Figure 1/Niniko Pancreas 721ゝ〕ゝ\”;ll-211 frontage 863-151232 (4 ) Figure 3 Figure 4 78 series/)-Iha,, 1-1

Claims (2)

[Claims] (1) An optical receiving device that receives an optical signal and converts the optical signal into an electrical signal, wherein the light receiving section of the optical receiving device is installed close to a condensing lens and the lens, and has a plurality of light receiving surfaces. and a light receiving element which is divided and each independent, and furthermore, the light receiving element is divided into parts according to the size of the light spot formed on the light receiving element by the light incident on the lens as an off-axis beam. An optical receiving device characterized in that the area of each divided light receiving surface increases from the center toward the periphery. (2) The optical receiving device according to claim 1, wherein the lens for condensing the light in the wide angle range is one ball lens.