JPS61182338A - Optical diffusing device - Google Patents

Abstract

PURPOSE:To ensure a wide service area and to attain communication with high reliability by arranging plural light emitting elements in circular to a focus of a cylindrical optical reflecting mirror having a parabolic curved face at its side face. CONSTITUTION:A light source comprising light emitting elements 6-41-6-4n is arranged at the focus of a reflection mirror 6-1 having a parabolic face. The parabolic face is corrected in an optical path C that light at a side angle from a light source O2 is reflected in a reflecting face 6-12 of the parabolic face 6-11 and propagates slightly downward. In optical paths D, E, the light near the center from the light source On propagates and since the optical output is large, the light is reflected in a direction of a diffusion limit angle psi(-60 deg.). Thus, the light in the direction of diffusion limit angle -60 deg. has a stronger optical output than other directions and a directivity is obtained. The operation above is applied as to the plural light emitting elements 6-41-6-4n and the photodetecting quantity of a reception signal is uniform on a plane within the transmission area in the diffusion angle.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] A light diffuser for an infrared space propagation communication device that uses the infrared rays of the present invention to communicate with a terminal device on the floor via a light diffuser installed in a high place such as a ceiling. Regarding the configuration of

[Background of the invention]

Figure 1 shows the configuration of a conventional light diffuser with a light emitting element 2-2.
1 to 2-2n are arranged in a circle and are fixed by an element mounting plate 2-3. A reflecting plate 2-1 is provided around the light emitting elements 2-21 to 2-2n, and the light emitting elements 2-21 are arranged at an aperture angle θ1. ~2-21
Diffusion of light. An example of the directivity characteristics at this time is shown in FIG. 2. In this example, θ is set to 120°. As is clear from this directional characteristic, the strength of the light output is strongest toward the center, and the disadvantage is that the light output decreases as the angle becomes wider.

[Purpose of the invention]

It is an object of the invention to provide a light diffuser which improves the drawbacks of the prior art.

[Summary of the invention]

FIG. 3 shows the relationship between the transmission distance of the infrared space propagation communication device. The transmission distance is Q, the position of the light diffuser is ○, the height to the light diffuser 0 is h, the receiving point is P, the point directly below the light diffuser is Q, and the receiving point P is movable on the line PQ. Then, the transmission distance Q is Q = h / cosθ, ...
... becomes ■. Here, el is the angle between the receiving point P and the position of the light diffuser.The condition that the amount of light received at the receiving point P, P2, remains constant even if the angle θ changes is -P, =P, /Ω2... ...From the relationship ■, it is necessary to increase the transmitted light output P0 in proportion to the square of the transmission distance. From the formula ■, P, = P r h ”
/ CO8" e 4, and p and h are normalized and set to 1, which is shown in Figure 4 up to ±60°. That is, the angle is ±60°.
In the 0° force direction, four times the destination output is required compared to the 0° force direction.

[Embodiments of the invention]

FIG. 5 shows a system diagram of the infrared space propagation communication device. Signals from the host computer 1-4 to the terminal device 1-6 are sent to the modem device 1-3. The form of the signal sent to the light diffuser 1-1 via the coaxial cable 1-2 is a baseband signal between the host computer 1-4 and the modem, and a modulated signal between the modem 1-3 and the light diffuser. It is a high frequency signal. The frequency of this high frequency signal is f.
It is distinguished from u.

The light diffuser 1-1 sends a high frequency signal f to the terminal device 1-6,
is converted into an optical signal and radiated from the ceiling 1-7 at a diffusion angle θ toward the optical conversion demodulator 1-5 provided on the terminal device 1-6 side.

The optical modulator/demodulator 1-5 converts the optical signal from the optical diffuser 1-1 into an electrical signal using a light receiving element to obtain a high-frequency signal f, which is further demodulated to the original baseband signal and sent to the terminal device 1-
6 for communication.

A cross section of the light diffuser of the present invention is shown in FIG. Further, FIG. 7 shows the bottom surface of the light diffuser of the present invention.

A conical reflector 6-1 with a parabolic curved surface is fixed with a fixing screw 6-2.
The light emitting element 6-4l is fixed to the element mounting plate 4-3 with
-6-4n is arranged on a circumference slightly larger than the diameter d of the reflecting mirror 6-1, so as to prevent the shadow of the reflecting mirror 6-1 directly below from being formed.

A light emitting element 6-41 is placed at the focal point of the reflecting mirror 6-1 having a radiation surface.
~6-4n light sources are arranged.

FIG. 8 shows a diagram of the operation of the light diffuser of the present invention.
4n light source 0. is at the focal point of the paraboloid 6-11 at the offset angle shown by the dotted line, and the optical path A is from the light source 0. Proceed directly below with direct light from. Similarly to the optical path A, the optical path B also has a light source 0. It is direct light from.

Optical path C is light source 0. With light at a side angle from , the paraboloid 6-
The paraboloid is corrected so that it is reflected by the reflective surface 6-12 of No. 11 and travels slightly downward. The optical path E is the light near the center from the light source O1, and the light output is large, so the diffusion limit angle ψ(
In this case, the light is reflected in the -60° direction. Therefore, a stronger light output is obtained in the diffusion limit angle -60@ direction than in other directions,
It becomes possible to obtain the directional characteristics shown in FIG. This operation is performed for the plurality of light emitting elements 6-41 to 6-4n, and the amount of light received by the received signal becomes uniform on a plane within the transmission area within the diffusion angle of the received signal.

In the explanation so far, the light diffuser of an infrared space propagation communication device between a host computer and a terminal device has been described, but the present invention can also be applied to a device that performs light diffusion through optical communication of modulated signals including audio signals.

As described above, when using the diffuser of the present invention, within the range having the diameter of the transmission range S in the transmission distance relationship diagram (Figure 3), the light output corresponding to the transmission distance a is Since the light output starts from 0, a uniform amount of received light can be obtained.

〔Effect of the invention〕

According to the configuration of the present invention, light having a strong intensity in the direction of the central axis of the light source is diffused toward the apogee within the transmission area using a parabolic mirror. Since the amount of light received at -5 is uniform within the transmission area, it is possible to ensure a wide service area <1, making highly reliable communication possible.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the cross section and bottom surface of a conventional light diffuser, Fig. 2 is a diagram showing the directional characteristics of the conventional light diffuser, Fig. 3 is a diagram showing the relationship between transmission distances, and Fig. 4 is a diagram according to the present invention. A diagram showing the directivity characteristics (calculated values) of a light diffuser, FIG. 5 is a block diagram of an infrared space propagation communication device to which the present invention is applied, and FIG. 6 is a diagram showing a cross-section of the light diffuser according to the present invention. FIG. 7 is a diagram showing the bottom surface of the light diffuser according to the present invention, and FIG. 8 is a diagram showing the operating characteristics of the light diffuser according to the present invention.

Claims (1)

[Claims] A light diffuser characterized in that a plurality of light emitting elements are arranged in a circular manner at the focal position of a cylindrical light reflecting mirror having a parabolic curved side surface.