JPH0746794B2 - Optical communication system - Google Patents

Description

Description: (a) Technical Field of the Invention The present invention relates to a cableless optical communication system, and more particularly to an optical communication path abnormality determination system for determining the presence or absence of an interference component due to an external factor contained in a received light signal. .

(B) Prior Art and Problems The present invention is used, for example, in an online test of a printer device, for automatic connection between a device under test successively carried by a belt conveyor and a test facility.

Conventionally, the interface between the host computer and the printer, which is the device under test, was connected using a connector. However, in order to eliminate the complexity of this connector connection, a test is performed by optical connection.

In the conventional cableless communication system using a light source for communication, there is no means for detecting interference due to an external factor (for example, blocking of an optical path or mixing of light rays of the same wavelength other than the intended purpose), and therefore there is a problem in reliability of a received light signal. there were.

(C) Object of the Invention In view of the above-mentioned conventional drawbacks, it is an object of the present invention to provide an abnormality determination method for an optical communication path capable of detecting the presence or absence of interference due to an external factor.

(D) Structure of the Invention And, as shown in FIG. 1, an object of the present invention is to provide an optical communication system including a light transmitting section 1 and a light receiving section 2 which are arranged with a predetermined space in between, and the light transmitting section 1 and the light receiving section. An optical communication path A for information transmission and at least one guard optical path B which is parallel to the optical communication path A are provided between the optical communication path A and the section 2, and a light receiving level received by the light receiving section 2 of the optical communication path A. An information determination signal obtained by comparing the signal P with a threshold value + V ₂ ′ within the normal range of the received light level value and an unmodulated received light level signal received through the guard optical path B An AND circuit 30 is provided to take the AND with the gart judgment signal obtained by comparing the upper and lower thresholds + V ₁ and + V ₂ within the normal range of the received light level value. And the information output is included in the optical communication path A. Is achieved by providing an optical communication system, characterized by determining the signal to be normal.

(E) Embodiments of the Invention Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a block diagram of an optical communication system according to the present invention.

The optical communication system in the figure is roughly divided into a light transmitting unit 1 and a light receiving unit 2.
And lenses 14 and 21 that are separated by a predetermined space.
An optical communication path A is constructed through and and a guard optical path B is constructed through the lens 14 'and the lens 21'.

A plurality of guard optical paths B are usually provided so as to surround the optical communication path A. The light transmitting unit 1 includes a storage unit 11 for storing information to be transmitted, a modulator 12 for superimposing the stored information as a modulation signal on carrier light, and a light transmitter 13 for emitting modulated carrier light.
And a light-sending lens 14 and a light-sending device 13 for splitting the light-sending device 13 to emit unmodulated light and a light-sending lens 14 '.

The light receiving unit 2 includes a light receiving lens 21, a light receiver 22 for photoelectrically converting incident light, and a detection rectifier 24 for shaping the output of the light receiver 22.
The light receiving level signal P is obtained via the demodulator 23, and the demodulator 23 that demodulates the modulated signal and outputs the reproduced signal 25 constitutes the first half of the light receiving section 2. The reproduced signal 25 is transmitted via the gate circuit 26 to the controller 27.
Is input to and processing is performed.

The light-receiving level signal P, the comparator 29 'as well as to one input terminal of the other to a low level threshold + V _2'
Is applied, and when the level value of the received light level signal P becomes smaller than the threshold value + V ₂ ′, the output of the comparator 29 ′ is connected so as to be inverted to the L level. The threshold value + V ₂ ′ is set to a required value within an allowable range for the reception level value of the received light level signal P in the normal state.

On the other hand, 22 'is a photodetector for photoelectrically converting unmodulated light incident from the guard optical path B through the level 21', and 24 'is a photodetector 22'.
It is a detection rectifier that shapes the output of. The received light level signal Q of unmodulated light obtained through the detection rectifier 24 'is input in parallel to the comparators 28 and 29, and a high level threshold value + V ₁ is applied to the input of the comparator 28 to apply the received light level signal Q The output of the comparator 28 is connected so as to be inverted to the L level when the level value exceeds the threshold value + V ₁ . A low level threshold value + V ₂ is applied to the input of the comparator 29, and the output of the comparator 29 is connected so as to be inverted to the L level when the level value of the received light level signal Q becomes smaller than the threshold value + V ₂ . In addition, the plurality of threshold values + V ₁ and + V ₂ are the light reception level signals Q
It is set to a required value within the allowable range for the reception level value at the normal time.

The outputs of the comparators 28 and 29 and the output of the comparator 29 'are input in parallel to the AND circuit 30, respectively, and the three comparators output the H level when all the received light level signals are normal. The output also outputs H level, but at least one of the outputs of each comparator is L level.
When it becomes the level, the output of the AND circuit 30 also becomes the L level, and at that time, the gate circuit 26 is triggered and the input of the reproduction signal 25 to the controller 27 is cut off. Further, each input signal to the AND circuit 30 is also input in parallel to the control unit 27 to monitor the level change of each input signal.

Next, the operation will be described. The light sending unit 1 starts sending unmodulated light from the light sending device 13 'to the guard light path B at a constant level, and then emits a light wave modulated by the information to be transmitted from the light sending device 13 to the optical communication path A. To do. As long as the light transmitter 13 of the light transmitter 1 emits a light wave of a constant level, the light reception level signal P of the light receiver 2 should always maintain a constant level when the optical communication path A is not disturbed. (However, it is assumed that the characteristics are compensated for changes in temperature, etc.) By the way, when the optical communication path A is completely or partially cut off due to an external factor, the optical communication path A is interrupted depending on the degree of the interruption. The incident light of the light receiver 22 becomes small, and the light receiving level value also decreases, and when the degree of this decrease becomes smaller than the threshold + V ₂ ′ of the allowable limit, the output of the AND circuit 30 becomes L level and the control of the reproduction signal 25 is controlled. The input to the device 27 is stopped.

Similarly, if all or part of the guard optical path B is blocked by the guard optical path B due to an external factor, the incident light of the photodetector 22 'becomes smaller according to the degree of the block, and the received light level value also decreases. When the degree of this decrease becomes smaller than the threshold value + V ₂ which is the allowable limit, the output of the AND circuit 30 becomes L level and the input of the reproduction signal 25 to the controller 27 is stopped.

Further, when a light wave of the same wavelength other than the target is received by the light receiver 22 due to an external factor in the guard light path B, a beat phenomenon occurs between the light wave for the original communication purpose and the amplitude of the combined wave is both. It fluctuates corresponding to the phase difference of the light wave, and the reproduced signal 25 is also affected by the change due to interference. Since the received light level value of the received light level signal Q also changes with the change of the composite wave to exceed the threshold + V ₁ or become smaller than the threshold + V ₂ , the AND circuit 30 outputs the L level and the gate circuit 26 is turned on. The input of the reproduction signal 25 to the controller 27 is stopped by triggering.

In such an optical path configuration, it is preferable to use light waves of different wavelengths in each optical path in order to avoid beat disturbance. Further, by appropriately selecting the arrangement and the number of the guard optical paths B with respect to the optical communication path A, it becomes possible to block the guard optical path B before the obstructing object on the optical path blocks the optical communication path A. It is possible to detect the interference of the optical communication path A in advance and control the transmission of information. This optical communication system can be used for communication between computers and the like by taking advantage of the feature of cableless.

(F) Effects of the Invention As described in detail above, the optical communication system of the present invention has an effect of improving the reliability of a transmission signal in cableless optical communication.

[Brief description of drawings]

FIG. 1 shows a block diagram of an optical communication system according to the present invention. In the figure, 1 is a light-transmitting part, 2 is a light-receiving part, 13 and 13 'are light-transmitting devices, 22 and 22' are light-receiving devices, 28, 29 and 29 'are comparators, 30 is an AND circuit, + V ₁ and + V ₂ And + V ₂ 'represent thresholds, respectively.

Claims (1)

[Claims] 1. An optical communication system including a light-transmitting section and a light-receiving section, which are arranged with a predetermined space therebetween, and an optical communication path for information transmission between the light-transmitting section and the light-receiving section, and the optical signal. At least one guard optical path parallel to the communication path is provided, and the received light level signal received by the light receiving section of the optical communication path is
The information determination signal obtained by comparing with the threshold value within the normal range of the received light level value and the unmodulated received light level signal received through the guard optical path are the upper and lower limits within the normal range of the received light level value. An AND circuit is provided for ANDing with the gart judgment signal obtained by performing the respective comparisons with the threshold value, and the information signal included in the optical communication path at the AND output when both of the plurality of judgment signals become normal. An optical communication system characterized by determining that the normal.