JPH07212314A - Converging light spot size discriminating method and device therefor - Google Patents

Abstract

PURPOSE:To discriminate whether the converging light spot size in the light receiving part of an optical radio communication equipment is matched with a desired design value or not by a simple constitution. CONSTITUTION:On the light receiving surface 30A of a light receiving element 30 receiving a light spot formed by a converging light means 28, through holes 32A and 32B of a prescribed size-or a shield means 32 where light transmission parts are provided at least two prescribed space is arranged. A light receiving part 10 including the converging light means and the light receiving element is rotated in a prescribed direction, the level of the output signal of the light receiving element is detected and a discrimination is performed by the mode of the change of the level. For the rotation of the light receiving part, a rotation stage 12 which is possible to rotate in a prescribed direction may be used. A computer 16 controls the rotation stage while fetching the output signal of the light receiving element via a digital multimeter 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver for an optical wireless communication device, and more particularly to a method and device for determining whether or not the size of a focused spot in a light receiving portion of the optical wireless communication device is appropriate.

[0002]

2. Description of the Related Art When performing signal transmission by optical wireless communication, it is very important on the light receiving side how much light can be collected from a light beam emitted from an optical transmitter to a light receiving element. Yes, it is closely related to transmission distance and transmission quality. If the size of the light spot obtained as a result of focusing is larger than the light receiving surface of the light receiving element, the light that does not hit the light receiving surface is wasted, and the transmission quality deteriorates accordingly. When the position or direction is determined by the received light, a plurality of light receiving elements may be used. In such a light receiving element, there is a dead zone between the divided light receiving areas where light cannot be detected, and if the focused spot does not have a certain size, all the light falls into the dead zone, and positioning or direction determination is performed. There are some inconveniences such as poor control. The focused spot size is mainly determined by the distance between the optical component and the light receiving element. Therefore, it is very important that the focused spot size is a desired size.

The size of the focused spot is determined by the characteristics of the optical system of the light receiving section and the distance between the optical component and the light receiving element. Therefore, if the mechanical precision such as the aberration of the lens or the reflecting mirror, the surface precision, the mounting error, and the mounting error of the light receiving element is relied on, the respective errors may be added, and there is a possibility that the desired focused spot size may be deviated. .

[0004]

As described above, in the receiver in optical wireless communication, the size of the light spot obtained on the light receiving surface as a result of focusing is extremely important. Even when trying to confirm the size, it was difficult to confirm with the naked eye even by using an auxiliary optical system. Therefore, it is necessary to monitor the output signal of the light receiving element and judge whether or not a good signal is actually obtained. Such a determination alone may result in a lower signal quality than the signal quality that should be originally obtained.

Therefore, according to the present invention, it is possible to determine with a simple configuration whether or not the focused spot size obtained on the light receiving surface of the light receiving element in the receiver of the optical wireless communication device matches the designed desired size. An object of the present invention is to provide a discriminating method and a discriminating apparatus that can be performed.

[0006]

In order to achieve the above object, according to the present invention, at least two through holes or light transmitting portions having a predetermined size are provided in the light receiving surface of a light receiving element at a predetermined interval. Means is arranged, the light receiving part including the light receiving element and the light collecting means is rotated in a predetermined direction to detect the output signal level of the light receiving element, and the light spot size is too large than the design value due to the level change mode. It is designed to determine whether or not it is too small.

If the size and the interval of the light transmitting portion of this through hole are both made equal to the design value of the condensing spot size, the detection level becomes a double mountain shape (the through hole or the light transmitting portion becomes 2 as the light receiving portion rotates. When the focused spot diameter and the design value match, this mountain shape becomes a triangle, and when they do not match, it becomes a trapezoid. Therefore, by monitoring this level change, it is possible to easily determine the focused spot size. Since the shielding means is used only for this determination and is not necessary during normal communication, it is detachably attached.

That is, according to the present invention, it is possible to discriminate the condensed spot size in the light receiving portion of the optical wireless communication receiver configured to collect the light incident from the predetermined direction and give the light spot to the light receiving element. In the method, at least two through-holes or light-transmitting portions of a predetermined size are provided at a predetermined interval on a light-receiving surface of the light-receiving element, and the converging spot is shielded. The light receiving part is rotated so as to move in the direction in which the through hole or the light transmitting part of the means is arranged, and when the light receiving parts are at different rotation angles, the output signal levels of the light receiving elements are sequentially detected and the output is output. A condensing spot size discriminating method for discriminating from a change mode of a signal level is provided.

Further, according to the present invention, the optical wireless communication has a condensing means for condensing light incident from a predetermined direction and a light receiving element for receiving a condensing spot resulting from condensing by the condensing means. Is a condensing spot size discriminating device in a light receiving portion of an optical receiving device, wherein at least two through holes or light transmitting portions having a predetermined size are provided at predetermined intervals, Holding means detachably arranged on the light-receiving surface of the element; and the at least two through-holes or light-transmitting portions provided on the shielding means when the shielding means is attached to the light-receiving surface. There is provided a condensing spot size discriminating apparatus having a rotating means for rotating the light receiving section so as to move in a lined direction and a detecting means for detecting an output signal level of the light receiving element. That.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall perspective view of a preferred embodiment of a focused spot size determination device of the present invention that realizes the focused spot size determination method of the present invention. In FIG. 1, the light receiver 10 is mounted on the rotary stage 12,
It can be rotated horizontally. The light receiver 10 is used as a part of a receiver of an optical wireless device (not shown). The light receiver 10 is attached and installed so that the optical axis thereof faces the incident light. Here, a light source device 20 that emits light for determining the focused spot size is used. Light source device 2
Reference numeral 0 has an LED (light emitting diode) 22, a drive circuit 24 that drives the LED 22, and a constant voltage source 26 that supplies a power supply voltage to the drive circuit 24.

FIG. 2 is a block diagram showing a part of FIG. The output signal of the light receiver 10 is a digital multimeter 14
To the computer 16 via the digital multimeter 14. That is, the digital multimeter 14 constitutes the detection means together with the computer 16. The computer 16 drives the rotary stage 12 to rotate the light receiver 10 little by little in the horizontal direction. At this time,
The computer 16 records the level of the output signal of the photodetector 10 that is input via the digital multimeter 14, that is, the output signal of the photodetector described later. The rotation of the light receiver 10 and the recording of the signal level may be performed while slowly rotating, or may be stopped after rotating by a certain angle, the signal level may be recorded in that state, and this may be repeated. Here, the former is used.

FIG. 3 is a side sectional view of the light receiver 10. The light receiver 10 has a parabolic reflecting mirror 28 that functions as a light converging unit inside the casing 10A, and a light receiving element 30 that is arranged in the vicinity of the focal point position of the parabolic reflecting mirror 28. For example, a photodiode can be used as the light receiving element 30, and the light receiving surface 30A thereof faces the center of the parabolic reflector 28. Although the above-described configuration is the same as that of the conventional light receiver 10, in the present invention, a shielding means is provided on the light receiving surface 30A of the light receiving element 30 in order to determine the size of the focused spot. As the shielding means, the shielding plate 32 shown in FIGS. 3 and 4 can be used. The light receiving element 30 is attached to the substrate 34, and the shield plate 32 is detachably attached to the support member 36 attached to the substrate 34. The support member 36 can use, for example, a U-shaped frame, and slidably holds the shield plate 32.

The shield plate 32 is detachable because the shield plate 32 must be in close contact with the light-receiving surface 30A of the light-receiving element 30 when the light-condensing spot size is determined, but at the time of other than the determination, that is, when the light is not detected. When communicating, shield plate 3
2 is an obstacle and is unnecessary, and it is necessary to remove it from the light receiving surface 30A so as not to block the optical path from the parabolic reflector 28 to the light receiving surface 30A. The shield plate 32 may be completely removable or may be hinged so that it can be opened and closed.

FIG. 4 is a plan view of the shielding plate 32. Hereinafter, the parabolic reflector 28 has a diameter of 50 mm and a focal length of 40 mm.
The case will be described. LE shown in FIG. 1 and FIG.
The light emitted from D22 is reflected and condensed by the parabolic reflecting mirror 28, and is incident on the light receiving element 30 only at the portion passing through one or both of the through holes 32A and 32B. The light receiving surface 10A of the light receiving element 30 is 2.0 mm square, and the shield plate 32 is 2.2 mm.
It was a corner. Designed focal spot diameter is 0.5 mm
If the circle is, the light receiving surface 10A of the light receiving element 30 may be displaced from the focus position by 0.4 mm. Since the design value of the focused spot is a circle with a diameter of 0.5 mm, the shielding plate 3
2 is a through-hole 32A having a diameter of 0.5 mm which is equal to the design value of the light spot with an interval of 0.5 mm which is equal to this.
Two 2B are provided in the horizontal direction. The through hole 32A,
The number of 32B is two in this embodiment, but at least two may be provided, and three or more may be provided.

Next, a method of discriminating the light spot size using the apparatus of the above embodiment will be described. The computer 16 captures and records or displays the output signal level of the light receiving element 30 that is sequentially obtained as the light receiver 10 rotates. A hard copy may be obtained by a printer (not shown) for this display, or the CRT 16 of the light receiver 10 may be obtained.
It may be obtained on the screen of A.

In this embodiment, since the two through holes 32A and 32B provided in the shielding plate 32 are arranged in the horizontal direction, the light receiving element 30 is rotated in the horizontal direction. That is, the light receiving element 30 may be rotated so that the light spot moves in the direction in which the through holes 32A and 32B are aligned.

In the above embodiment, when the rotary stage 12 is driven to rotate the photodetector 10 horizontally and the output of the photodetector 30 at that time is measured, a graph as shown in FIG. 5 is obtained. In each graph, the horizontal axis represents the rotation angle and the vertical axis represents the output signal level. In either case, the through holes 32A, 32B
A number of mountain-shaped graphs are obtained according to the number of. If the size of the focused spot completely matches the design value, two triangular shapes are obtained as shown in (A). If the size of the focused spot is larger than the design value, it becomes a combination of two trapezoids with a low height and a shallow central valley as shown in (B), and vice versa. When it is small, two trapezoidal graphs separated at the center as in (C) are obtained. Therefore, actually measure (A)
If such a result is obtained, it can be confirmed that the focused spot size is as designed, and (B) or (C)
If the result is, it is understood that it is not as designed. It can be seen that when the focused spot size is different from the designed value, it is necessary to take measures such as changing the distance between the light receiving element 30 and the parabolic reflector 28. In order to change this distance, for example, the light receiving element 30 may be movable in the optical axis direction, and the adjustment knob may be manually rotated to adjust the distance so that the focused spot size approaches the design value. it can.

In the above embodiment, the through hole 3 is used as the shielding means.
Although the shielding plate 32 having 2A and 32B is used, the present invention is not limited to this, and two or more light transmitting portions are left on a light transmitting plate material such as glass, quartz, or synthetic resin, and other portions are colored. It is also possible to use a shielding means obtained by attaching an adherent. A lens or other optical system can also be used as the light converging means.

[0019]

As described above, according to the condensing spot size discriminating method and the condensing spot size discriminating device of the present invention, a shield provided with two or more through holes or light transmitting portions of a predetermined size at a predetermined interval. By arranging the means on the light-receiving surface of the light-receiving element of the light-receiving section of the optical wireless communication device, the light-receiving section is rotated in a predetermined direction, and the resulting change in the output signal level from the light-receiving element is monitored for determination. Therefore, it is possible to know with a simple configuration what kind of relationship the actual focused spot size obtained by the optical system such as the focusing means has with the design value. Therefore, it becomes easy to understand the variations at the stage when a plurality of light receivers are manufactured, and it becomes easy to control the accuracy. Also, it is not only known that the focused spot size is different from the designed value, but it is easy to recognize whether it is larger or smaller than the designed value. It is convenient in deciding how to do it.

[Brief description of drawings]

FIG. 1 is a perspective view of a preferred embodiment of a focused spot size determination device of the present invention.

2 is a block diagram of a portion of the embodiment shown in FIG.

FIG. 3 is a side sectional view of a light receiving portion in FIGS. 1 and 2.

FIG. 4 is a plan view of the shielding plate in FIG.

5 is a graph showing the measurement results obtained by the examples of FIGS. 1 and 2. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 light receiver 12 rotating stage (rotating means) 14 digital multimeter (constituting detection means together with computer 16) 16 computer 16A CRT 20 light source device 22 LED 24 drive circuit 26 constant voltage source 28 parabolic reflector (light collecting means) ) 30 light receiving element 30A light receiving surface 32 shielding plate (shielding means) 32A, 32B through hole 34 substrate 36 supporting member (holding means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G01M 11/00 T 9309-2G H04B 10/08

Claims (2)

[Claims] 1. A method for determining a focused spot size in a light receiving portion of a receiver for optical wireless communication, which is configured to collect light incident from a predetermined direction to give a light spot to a light receiving element, At least two through-holes or light-transmitting portions of a predetermined size are provided on the light-receiving surface of the light-receiving element, and the light-shielding means is provided on the light-receiving surface of the light-receiving element. Alternatively, the light receiving unit is rotated so as to move in the direction in which the light transmitting portions are arranged, and when the light receiving units have different rotation angles, the output signal levels of the light receiving elements are sequentially detected, and the output signal level change mode Focus spot size determination method to determine from 2. A light receiving device for optical wireless communication, comprising: a light-collecting unit that collects light incident from a predetermined direction; and a light-receiving element that receives a light-collecting spot resulting from light collection by the light-collecting unit. A condensing spot size determining device in a portion, wherein at least two through holes or light transmitting portions having a predetermined size are provided at predetermined intervals, and the shielding means is provided on a light receiving surface of the light receiving element. Holding means that can be removably arranged; and when the shielding means is attached to the light receiving surface, the condensing spot is in a direction in which the at least two through holes or light transmitting portions provided in the shielding means are arranged side by side. A condensing spot size discriminating apparatus having a rotating unit that rotates the light receiving unit so as to move, and a detecting unit that detects an output signal level of the light receiving element.