JPH01289328A - Optical signal receiver - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an optical signal receiving device used in optical communication devices, photodetecting devices, and the like.

"Prior Art" When communicating by optical signals, a configuration is adopted in which the optical signals are transmitted from a transmitting section 10 to a receiving section 12, as shown in FIG.

In this case, the transmitting section 10 is generally provided with a light emitter 1oa and a light projecting lens 10b, and the receiving section 12 is provided with an optical filter 12a, a light receiving lens 12b, and a light receiving element 12c.

The light emitter 10a is driven by a pulsed power source and emits pulsed light in order to distinguish it from ambient light. This pulsed light is used as a carrier wave and is output as signal light modulated by signals containing various information.

This signal light is condensed by the light projecting lens 10b and radiated to the receiving section 12 side.

When the emission wavelength of the five light emitters 10a is near-infrared light, the optical filter 12a is composed of a filter that cuts visible light, or a bandpass filter that passes only the emission wavelength of the light emitter 10a. be done. The signal light that has passed through the optical filter 12a is transmitted to the light receiving element 12C via the light receiving lens 12b, and is converted into an electrical signal by the light receiving element 12c. The output of this light receiving element 12c is
As shown in FIG. 7, the signal is input to the differentiating circuit 14, and only the target carrier wave is extracted from the output signal of the light receiving element 12c, and is output to the amplifier circuit 16.

The amplifier circuit 16 amplifies the carrier wave with a predetermined amplification degree.

The amplified signal is output to the demodulation circuit 18, and the electrical signal input to the demodulation circuit 18 is demodulated, and only the target No. 48 is extracted from the carrier wave modulated by various information signals.

In this way, when transmitting signal light from the transmitter 10 to the receiver 12, pulsed light is output from one light emitter 12a.
Natural light from sunlight and artificial light from electric potential, other than pulsed light, enter the receiving section 12 as noise light. Light with a 24-hour cycle of light and dark, such as sunlight, can be considered constant light.

Also, the frequency of electric potential light that flashes at a commercial frequency is 50
~100Hz, so the frequency of the pulsed light is set to 10
If the frequency is about KHz, it is possible to distinguish between pulsed light for communication and other ambient light.

[Problems to be Solved by the Invention] However, in the configuration of a conventional receiving device, when high-frequency ambient light is irradiated onto the light receiving element 12c from a high-frequency electric device using an inverter as a power source, this irradiated light becomes noise light. As a result, it becomes difficult to separate the signal light from the five light emitters 10a from the above-mentioned noise light, and it may not be possible to reliably receive only the communication pulse light. From this, the receiving unit 12
It is necessary to set the acceptance angle as small as possible to prevent ambient light that becomes noise light from entering. Also.

Furthermore, when receiving the signal light from the light emitter 10a while moving the receiving section 12, it is necessary to increase the light projection angle of the transmitting section 10 and the light receiving angle of the receiving section 12;
When such settings are made, a large amount of ambient light is taken in, resulting in a very poor S/N ratio, and some of the ambient light has frequency components that are the same as or similar to the carrier wave of the communication pulsed light. In some cases, it may be impossible to separate the communication pulsed light from the noise light.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to develop an optical signal receiving device that can receive only signal light without being affected by ambient light.

"Means for Solving the Problems" In order to achieve the above object, the present invention provides a method for outputting electrical signals in response to signal light and light including noise light acting as a noise signal on the signal light. a first light receiving means, a filter means for blocking the wavelength range of the signal light and allowing the noise light to pass through, a second light receiving means for outputting an electrical signal in response to the noise light that has passed through the filter means; The output level of the output signal of the light receiving means corresponding to the noise light and the output level of the second light receiving means are adjusted to be the same or approximately the same level as necessary. An optical signal receiving apparatus is proposed, characterized in that it has a differential output means which receives an output signal of the optical signal and generates an electrical signal corresponding to the signal light.

"Function" When the first light receiving means is irradiated with the signal light together with the ambient light, an electric signal corresponding to the light is output. The filter means also has a first
The same light as the light receiving means is irradiated, and only noise light passes through. The second light receiving means outputs an electric signal in response to the noise light that has passed through the filter means.

After the output signal level corresponding to the noise light of the electrical signal from the first light receiving means and the output signal level of the second light receiving means are adjusted to the same or almost the same level, the first. The output signal of the second light receiving means is input to the differential output means.

- Therefore, the output signals corresponding to the noise light of the first and second light receiving means are canceled by the differential output means, and only the output signal corresponding to the signal light is outputted by the differential output means.

"Example" An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the receiving device 20 is composed of a pair of bandpass filters 22.24, a pair of light receiving elements 26, 28, and a receiving circuit 30, and each bandpass filter 22.24 includes a receiving circuit 30.
The signal light from the light source 32 and the high-frequency light from the fluorescent lamp 34 as ambient light are incident on the light source 24 .

The light WX 32 is composed of LEDs and the like, and is configured to emit near-infrared light with a center wavelength of 850 nm, which is close to single-wavelength light, and has spectral characteristics shown by the dotted line in FIG. 2.

Further, as shown in FIG. 2, the fluorescent lamp 34 includes various light wavelength components and is shown as a noise light generation source.

As shown in FIG. 3, the bandpass filter 22 has a light emission range 1 of the signal light from the light source 32, for example, 800 nm to 90 nm.
It is configured to allow only 0 nm light to pass through, and only the light included in the above-mentioned light emitting region out of the signal light from the light source 32 and the irradiation light from the fluorescent lamp 34 is allowed to pass through.

On the other hand, the bandpass filter 24 is designed to pass light outside the emission range of the signal light from the light source 32, as shown by the dotted line in FIG. That is, the configuration is such that the signal light from the light source 32 is blocked.

The light that has passed through the bandpass filter 22 is transmitted to the light emitting element 26, and the noise light that has passed through the bandpass filter 24 is transmitted to the light receiving element 28, where they are each converted into electrical signals and input into the receiving circuit 3o.

As shown in FIG. 4, the receiving circuit 30 includes impedance elements 36, 38 . It is composed of amplifiers 40, 42 and a differential amplifier 44, and the impedance element 36 is connected to the light receiving element 2.
6, impedance elements 38 are connected to the light receiving elements 28, respectively. The light received by the light receiving element 26.28 is amplified by the amplifier 40.42 at a predetermined amplification degree.

The amplifiers 40 and 42 are configured as level adjustment means for adjusting the output level of the impedance element 36 and the output level of the impedance element 38. That is, these amplifiers 40 and 42 adjust the signal level corresponding to noise light among the output signals of the light receiving element 26 and the output signal level of the light receiving element 28 to be at the same level.

The output signal of each amplifier 118B40.42 is outputted to a differential amplifier 4.
4.

The differential amplifier 44 serves as differential output means and is configured to generate a differential output between the output signal of the amplifier 40 and the output signal of the amplifier 42. In this case, the electrical signals corresponding to the signal light and the noise light are inputted to the differential amplifier 44 from the amplifier 40, and the electrical signals corresponding to the noise light are inputted from the amplifier 42, but the electrical signals corresponding to the noise light are inputted to the differential amplifier 44. Same level as above! II! ! Therefore, the electrical signal corresponding to the noise light is canceled out, and only the electrical signal corresponding to the signal light is output from the differential amplifier 44.

The output signal of the differential amplifier 44 passes through an amplifier circuit and a demodulation circuit, and only the target transmission signal component contained in the signal light can be extracted.

In addition, in the above embodiment, the fluorescent lamp 3 is used as the noise light.
Although the pulsed light generated from 4 has been described, even if the noise light is steady light, only the signal light can be extracted.

In this case, it is necessary to use a resistor as the impedance element 36,38.

Further, as the filter 24, it is sufficient that the light from the light source 32 can be blocked and the wavelength range of the noise light can be transmitted.
It is possible to configure it with the characteristics shown in the figure.

Further, as the filter 22, it is also possible to use a shortcut filter having characteristics as shown by the dotted line in FIG.

Further, in the embodiment, although it is not necessary to provide the bandpass filter 22, the bandpass filter 22
By providing this, light other than the wavelength of light emitted from the light source 32 is blocked, so a signal with a good S/N ratio can be obtained from the light receiving element 26.

Furthermore, if noise light generating sources such as fluorescent lamps 34 are installed in multiple locations, and the emission spectra of these noise lights are different, and the receiving device is moved under such circumstances, each light receiving element 26, 28 is Since the intensity of the irradiated noise light varies, in order to receive signal light with less noise components, the amplification degree of the amplifiers 40 and 42 should be adjusted for each location, or the attenuation of the bandpass filters 22 and 24 should be adjusted. need to be adjusted.

Furthermore, if the output sensitivities of the light receiving elements 26, 28 are the same with respect to noise light, there is no particular need for amplification for the adjusting means of the amplifiers 40, 42.

Further, the receiving device in the above embodiment can be used for an ID card system, a voice communication system, a remote controller, a personal computer terminal communication, a device for detecting the position of an object, a device for detecting the presence of an object by opening and closing an optical path, and the like.

"Effects of the Invention" As explained above, according to the present invention, the noise signal component of the first light receiving means that is sensitive to signal light and noise light is the same as the output signal of the second light receiving means that is sensitive to noise light. , or after adjusting to approximately the same level, the first. Name for finding the differential output of the output signal of the second light receiving means! Therefore, the influence of noise light is extremely small, and only signal light can be received, and a received signal with a high SZN ratio can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a simple configuration diagram showing one embodiment of the present invention, and FIG.
3 is a characteristic diagram of the band pass filters 22 and 24, FIG. 4 is a diagram showing a specific circuit example of the receiving circuit 30, and FIG. 5 is a diagram of the band pass filter 24. FIG. 6 is a simplified configuration diagram of a conventional transmitting/receiving section, and FIG. 7 is a block diagram showing a signal processing circuit of receiver No. 4. 20... Receiving device 22.24... Bandpass filter 26.28...
... Light receiving element 30 ... Receiving circuit 32 ... Light source 36.38 ... Impedance element 40.42 ...
...Amplifier 44... Differential amplifier Fig. 1 Image +□ Input 1t, X nm Fig. 6 Fig. 3 G 7 Fig. 4 Fig. 5 □ Input X100 nm

Claims (1)

[Claims] a first light receiving means for outputting an electrical signal in response to signal light and light including noise light acting as a noise signal on the signal light; a second light receiving means that outputs an electrical signal in response to the noise light that has passed through the filtering means;
1. A receiving device for optical signals, comprising differential output means for inputting the output signals of the first and second light receiving means and generating an electric signal corresponding to the signal light.