JP2003152649A - Optical receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform stable reception by suppressing continuous wave noise or impulse noise. SOLUTION: When an input signal is contained in a BPF signal A outputted from an amplifier circuit 2 through a BPF 3, the gain of the amplifier circuit 2 is controlled by a signal AGC voltage provided by an AGC detector 4 and a signal level detecting part 5 so that the input signal can become a prescribed signal level and when noise is contained in the BPF signal A outputted from the amplifier circuit 2 through the BPF 3, the gain of the amplifier circuit 2 is controlled by a noise AGC voltage provided by the AGC detector 4 and a noise level detecting part 6 so that the continuous wave noise or impulse noise inputted as disturbance light can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiver suitable for receiving a signal transmitted using light such as infrared rays.

[0002]

2. Description of the Related Art Conventionally, as a remote control system for operating an electronic device from a distant position, a system for transmitting operation information using light such as infrared rays is known. As such a remote control system, for example, infrared rays are used from a remote commander to transmit a transmission signal obtained by modulating a carrier wave of a certain predetermined frequency according to operation information, and the transmission signal is transmitted to the infrared rays mounted on the main body of the device. It is well known that the receiver is configured to receive. Such an infrared receiver is configured to include a light receiving element such as a photodiode and a demodulation circuit that demodulates an operation signal from a light reception signal received by the light receiving element. The data is output to a computer (hereinafter referred to as "microcomputer").

By the way, in the infrared receiving device as described above, the light receiving element also receives the ambient light noise generated in the illumination device or the like. Therefore, under the condition where the ambient light noise is generated, the pulse noise corresponding to the ambient light noise received by the light receiving element is taken into the microcomputer of the device. In this case, the microcomputer determines that the pulse noise from the infrared receiver is an input signal from the remote commander and performs signal determination processing. Therefore, under the environment where pulse noise is input, the microcomputer remains in the operation state (busy state) for distinguishing the input signal, which causes a problem that other operations cannot be performed. was there.

Therefore, in order to solve the above problems, 1
As one means, for example, an attenuation plate for attenuating ambient light noise may be provided on the front surface of the light receiving element to attenuate the ambient light noise component received by the light receiving element. However, in this case, since infrared light from the remote commander is attenuated in addition to the ambient light noise component, there is a problem that the transmission reach distance of the remote commander becomes short.

Therefore, the conventional infrared receiver employs various noise suppression methods as a measure against ambient light noise. FIG. 5 is a block diagram of an infrared receiving device showing an example thereof. In FIG. 5, the light receiving element 101 is a portion that receives an optical signal transmitted by infrared rays or the like, and converts, for example, a photocurrent obtained according to the amount of received light into a voltage and outputs it. This output is a bandpass filter (BPF) 103 amplified by an amplifier circuit 102 to remove unnecessary band components, and then a detector 104 as a BPF signal A.
Is output to. The detector 104 uses the B from the BPF 103.
The input signal is detected by comparing the PF signal A with the required slice level Vth, the detected signal B output from the detector 104 is integrated by the integrator 105, and the integrated signal C is waveform-shaped by the waveform shaper 106. By shaping, the light receiving element 101
Output signal (demodulated signal) obtained by demodulating the input signal input to
I am trying to get D.

In such an infrared receiver,
As a measure against ambient light noise, an initial offset level is given to the slice level Vth of the detector 104, and this slice level Vth is configured to change following the level of the BPF signal A. With this configuration, even when the light receiving element 101 receives the ambient light noise component together with the input signal from the remote commander,
Since the slice level Vth of the detector 104 follows the input signal level from the remote commander and becomes a sufficiently high level, it is possible to prevent the detector 104 from detecting the disturbance light noise component.

Further, even if the ambient light noise component is received by the light receiving element 101 under the condition that there is no input signal from the remote commander, the slice level V of the detector 104 is detected.
Since an initial offset level is given in advance to th, if the level of the disturbance light noise component is equal to or lower than the slice level Vth of the detector 104, the detector 104 should not detect the disturbance light noise. You can

FIG. 7 is another block diagram of a conventional infrared receiver. In the infrared receiver shown in FIG. 7, the output of the light receiving element 201 is input to the amplifier circuit 202, the gain is adjusted in the amplifier circuit 202, and the unnecessary band component is removed in the BPF 203 to obtain the BPF signal A. There is. Then, the detection signal B obtained by detecting the BPF signal A by the wave detector 204 is shaped by the waveform shaper 206 to obtain the output signal D by demodulating the input signal input to the light receiving element 201. ing.

In this case, the detection signal B output from the detector 204 is also input to the signal level detection unit 205.
The signal level detection unit 205 controls the amplifier circuit 202 so that the input signal level from the light receiving element 201 becomes a constant level.
Gain automatically adjusted (AGC; Automatic GainContro
In order to do l), a control signal for controlling the amplifier circuit 202 is generated and output based on the level of the detection signal B from the detector 204. With this configuration, the BPF 203
If the level of the ambient light noise included in the BPF signal A output from the device is lower than the level of the input signal from the remote commander, the AGC operation suppresses the level of the ambient light noise included in the BPF signal A. As a result, the detector 204 can be prevented from detecting the ambient light noise.

[0010]

However, in recent years,
With the spread of high-frequency inverter type inverter fluorescent lamps and fluorescent lamps of the so-called rabbit start type, which light with a boosted high voltage, the conventional infrared receiver as described above sufficiently suppresses ambient light noise components. It has the drawback of not being able to do it.

The problems of the conventional infrared receiver will be specifically described below with reference to the operation waveforms shown in FIGS. 6 and 8. FIG. 6 is a diagram showing operation waveforms of each part of the infrared receiver shown in FIG. 5, and FIG. 6 (a) shows operation waveforms of each part in the absence of ambient light noise, FIG. 6 (b). 6C shows the operation waveforms of the respective parts when there is continuous wave noise from the inverter fluorescent lamp, and FIG. 6C shows the operation waveforms of the respective parts when there is impulse noise from the rabbit start type fluorescent lamp. .

First, as shown in FIG. 6A, in a state where there is no ambient light noise from the illuminating device, in a no-signal section where there is no input signal (transmission signal) from a remote commander (not shown), the BPF 103 outputs a signal. The BPF signal A is in a non-signal state. At this time, since the slice level Vth of the detector 104 has become a predetermined initial offset level, the detector 104 does not output the detection signal B and the integration signal C of the integrator 105 does not change. The output signal D output from the shaper 106 becomes a high level indicating that there is no signal.

On the other hand, in the signal input section in which the input signal is input from the remote commander, the slice level Vth of the detector 104 rises from the initial offset level following the level of the BPF signal A from the BPF 103, and this slice The detection signal B is output by comparing the level Vth with the level of the BPF signal A. The level of the integrated signal C obtained by integrating the detected signal B by the integrator 105 is the hysteresis level V1 (O of the waveform shaper 106).
When it exceeds N), the output signal D of the waveform shaper 106 falls from the high level to the low level. When the level of the integrated signal C output from the integrator 105 drops below the hysteresis level V2 (OFF),
The output signal D of the waveform shaper 106 rises from low level to high level. Therefore, in the absence of ambient light, the waveform shaper 106 outputs the output signal D obtained by demodulating the input signal from the remote commander.

On the other hand, as shown in FIG.
In the state where the continuous wave noise is input from the inverter fluorescent lamp, if the level of the continuous wave noise becomes higher than the initial offset level of the slice level Vth, the detection signal B is output from the detector 104 even in the no signal section. The integrated signal C of the integrator 105 has a waveform as shown in the figure, and the output signal D output from the waveform shaper 106 becomes an erroneous signal.

Further, as shown in FIG. 6C, the detector 104 always detects the impulse noise contained in the BPF signal A when the rabbit start type fluorescent lamp has the impulse noise. In the non-signal section, since the integrated signal C of the integrator 105 does not exceed the hysteresis level V1 of the waveform shaper 106, the output signal D of the waveform shaper 106 is not affected by impulse noise. However, in the signal input section,
Before the integral signal C of the integrator 105 is sufficiently reduced, the integral signal C is increased by the detection signal B that detects the impulse noise, and the integral signal C exceeds the hysteresis level V1. May output an output signal D in response to the.

As described above, in the conventional infrared receiver shown in FIG. 5, the noise countermeasure in the non-signal section where there is no transmission signal from the remote commander merely gives the slice level Vth of the detector 104 an initial offset level. As a countermeasure, if continuous wave noise equal to or higher than the initial offset level is input in the no-signal section, the detector 104
However, there is a drawback in that the continuous wave noise is detected and the output signal D is output from the waveform shaper 106 even though there is no signal. Further, in the signal input section, it is possible to eliminate the influence of continuous wave noise,
When the impulse noise is input, there is a drawback that an erroneous output signal D that responds to the impulse noise is output.

Next, FIG. 8 is a diagram showing operation waveforms of each part of the infrared receiver shown in FIG. 7, and FIG. 8 (a) is an operation waveform of each part in the absence of ambient light noise, FIG.
FIG. 8B shows operation waveforms of each part when there is continuous wave noise from the inverter fluorescent lamp, and FIG. 8C shows operation waveforms of each part when there is impulse noise from the rabbit start type fluorescent lamp. There is.

Also in this case, as shown in FIG. 8A, in the no-signal section in which there is no ambient light noise from the illuminating device and there is no input signal from the remote commander, BP
Since the BPF signal A of F203 is in a non-signal state, the output signal D output from the waveform shaper 206 becomes high level.

On the other hand, in the signal input section, the input signal becomes a constant level by the AGC operation by the signal level detection unit 205, and the BPF signal A having this constant level is detected by the detector 204 to obtain the detection signal B. ing.
Therefore, when the level of the detection signal B exceeds the hysteresis level V1 (ON) of the waveform shaper 206, the output signal D of the waveform shaper 206 falls from the high level to the low level and the level of the detection signal B changes. When it becomes lower than the hysteresis level V2 (OFF), the output signal D of the waveform shaper 206 rises from low level to high level. By operating in this manner, the output signal D obtained by demodulating the input signal from the remote commander is output from the waveform shaper 206 in the absence of ambient light.

On the other hand, as shown in FIG.
With continuous wave noise from the inverter fluorescent lamp,
Even in the non-signal section, the detector 204 outputs the detection signal B, and the output signal D output from the waveform shaper 206 becomes an erroneous signal.

Further, as shown in FIG. 8C, when there is impulse noise from a rabbit start type fluorescent lamp or the like, the impulse noise is detected in the detector 204 in both the no-signal section and the signal input section. The detected signal is output from the waveform shaper 206 in response to the impulse noise.

As described above, in the conventional infrared receiver shown in FIG. 7 as well, as in the infrared receiver shown in FIG. 5, when continuous wave noise is generated from the inverter fluorescent lamp in the no signal section, detection is performed. There is a disadvantage that the continuous wave noise is detected by the device 204 and the output signal D corresponding to the continuous wave noise is output from the waveform shaper 206.
Further, regarding the impulse noise from the rabbit start type fluorescent lamp, detection is performed by the detector 204 in both the no-signal section and the signal input section, and the waveform shaper 2
From 06, there is a drawback that the output signal D in response to impulse noise is output.

Further, as a modified example of the infrared light receiving device shown in FIG. 7, an infrared light receiving device in which a noise level is detected by the signal level detection unit 205 and the AGC operation of the amplifier circuit 202 is performed is proposed. However, in this case, in order to perform noise detection in the level detection unit 205, since the level detection unit 205 needs to be configured with a long time constant circuit of several hundred ms, impulse noise generated by the rabbit start type fluorescent lamp is required. Could not be suppressed.

As described above, in the conventional infrared receiver,
For example, continuous wave noise generated by an inverter fluorescent lamp and impulse noise generated by a rabbit start type fluorescent lamp cannot be sufficiently suppressed.

[0025]

Therefore, the present invention has been made in view of such a point, and a light receiving element for receiving an input signal from an optical transmitter and an amplification for amplifying a light receiving output of the light receiving element. Means and a predetermined offset level and a first threshold voltage whose level fluctuates according to the amplified output level from the amplifying means and the amplified output are compared to detect the input signal. Detection means, demodulation means for demodulating the input signal from the detection output of the first detection means, and a signal for controlling the gain of the amplification means so that the input signal included in the amplified output has a predetermined signal level. A level control means and a noise level control means for controlling the gain of the amplification means so that the noise component included in the amplified output has a predetermined noise level.

According to the present invention, when the amplified output from the amplifying means includes the input signal, the signal level control means controls the gain of the amplifying means so that the input signal has a predetermined signal level. In addition, when a noise component is included in the amplified output from the amplifying unit, the noise level control unit controls the gain of the amplifying unit so that the noise component has a predetermined noise level, thereby disturbing the ambient light. The input signal can be demodulated without being affected by continuous wave noise or impulse noise input as.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. In this embodiment, an infrared receiving device will be described as an example of the optical receiving device of the present invention. FIG. 1 is a block diagram of an infrared receiver as an embodiment of the present invention. In FIG. 1, the light receiving element 1
Is a portion for receiving an optical signal transmitted by infrared rays or the like from an optical transmitter such as a remote commander (not shown). The photoelectric current obtained according to the amount of received light is converted into a voltage and output to the amplifier circuit 2.

The gain of the amplifier circuit 2 can be adjusted according to a control signal (AGC voltage) from a signal level detector 5 and a noise level detector 6, which will be described later, and the output signal from the light receiving element 1 is set to the AGC voltage. The gain is adjusted accordingly and output to the bandpass filter 3.

The bandpass filter (BPF) 3 is a bandpass filter whose band is set so as to pass only the carrier frequency component of the transmission signal input from the optical transmission device and remove the other band components. The BPF signal A that has passed through the BPF 3 is input to the detector 4 and the detector 8.

The detector 4 includes a signal level detector 5 which will be described later.
The noise level detector 6 is provided to detect the detection signal E used when generating the AGC voltage that controls the gain of the amplifier circuit 2. In this specification, in order to avoid confusion with the later-described detector 8, the detector 4 will be referred to as “AGC detector 4” hereinafter.

The AGC detector 4 uses the BPF from the BPF 3.
A double-wave rectifier circuit for double-wave rectifying the signal A and an input signal from the optical transmitter included in the BPF signal A are detected,
It is provided with a detection circuit for detecting a noise signal component from the lighting device. Such a detection circuit is composed of a slice level for signal detection and a comparator provided with a slice level for noise detection. A level difference is provided between the slice level for signal detection and the slice level for noise detection. At this time, BPF signal A
Each slice level is set such that the level of the noise signal component included in the signal is lower than the signal level.

That is, the AGC detector 4 compares the BPF output signal A, which has been double-wave rectified by the double-wave rectifier circuit, with the slice level for signal detection to perform signal detection as second detection means, and Similarly, the double-wave rectified BPF output signal is compared with the slice level for noise detection to perform the detection operation of the third detection means for performing noise detection. The signal detection output and the noise detection output output from the AGC detector 4 are output to the signal level detection unit 5 and the noise level detection unit 6, respectively.

The signal level detector 5 is composed of a time constant circuit composed of, for example, a capacitor, and charges and discharges the capacitor by the signal detection output from the AGC detector 4 to control the gain of the amplifier circuit 2. (Hereinafter, referred to as “signal AGC voltage”). This signal AGC voltage is fed back to the amplifier circuit 2 via the adder 7.

The noise level detecting section 6 is also composed of a time constant circuit composed of, for example, a capacitor, and the AGC
The capacitor 4 is charged and discharged by the noise detection output from the detector 4 to generate an AGC voltage (hereinafter, referred to as “noise AGC voltage”) that controls the gain of the amplifier circuit 2. This noise AGC voltage is fed back to the amplifier circuit 2 via the adder 7.

By the way, the AGC detector 4 described above is
The PF output signal A is compared with a slice level for signal detection, the comparison result is output as a signal detection output, and the BPF output signal A is compared with a slice level for noise detection, and the comparison result is a noise detection output. Will be output as. Therefore, when the BPF output signal A includes a noise component having a level higher than the slice level for signal detection, the detection output including this noise component is output to the signal level detection unit 5 as the signal detection output, Further, when the BPF output signal A includes a signal component, the detection output including this signal component is output to the noise level detection unit 6 as a noise detection output. That is, A
The signal detection output output from the GC detector 4 to the signal level detection unit 5 includes a detection output obtained by detecting a noise component, and also the noise detection output output from the AGC detector 4 to the noise level detection unit 6 May include a detection output obtained by detecting a signal component.

Therefore, in the present embodiment, the signal level detection unit 5 and the noise level detection unit 6 are configured as follows, so that the signal level detection unit 5 outputs the signal detection output from the AGC detector 4 as a signal. The signal AGC voltage is generated when the detection output is obtained by detecting the component, and the noise level detection unit 6
Generates a noise AGC voltage when the noise detection output from the AGC detector 4 is a detection output obtained by detecting a noise signal component.

In general, a transmission signal sent from a remote commander or the like using infrared rays has a duty ratio (Duty ratio) of the signal ON section and the signal OFF section of 50% or less and a signal length of 50. It is set to about 100 ms. Further, it is known that a signal ON period of 2 to 10 ms is usually provided as a guide pulse at the head of the transmission signal. On the other hand, it is known that the ambient light noise component from the lighting device or the like is a continuous wave or white noise except for impulse noise generated in a rabbit start type fluorescent lamp.

Therefore, the noise level detecting section 6 of the present embodiment determines whether the noise detection output is the detection output obtained by detecting the noise component based on the difference in the duty ratio of the noise detection output detected by the AGC detector 4. When the noise detection output is obtained by detecting the noise component, noise AG
The C voltage is generated. Therefore, the noise level detection unit 6 sets the duty ratio of the charging / discharging time of the capacitor that constitutes the time constant circuit to 50%, and sets the capacitance value so that the time constant is 100 to several hundreds ms. It is set.

Further, in the signal level detecting section 5, whether or not the signal detection output is the detection output obtained by detecting the signal component by the guide pulse (2 to 10 ms) provided at the head of the transmission signal from the optical transmitter. It is determined that the signal AGC voltage is generated when the detection output is obtained by detecting the signal component. Therefore, the signal level detection unit 5 raises with the guide pulse (2 to 10 ms) provided at the head of the input signal sent from the optical transmitter,
The current value and the capacitance value are set so that the time constant is within 2 ms.

When the signal level detecting section 5 and the noise level detecting section 6 are configured as described above, the output waveform of the detection signal E output from the AGC detector 4 when continuous wave noise is generated is as shown in FIG. become. That is, in the no-signal section where there is no input signal from the optical transmitter, only the noise level detection unit 6 operates, so the level of continuous wave noise is limited to the noise AGC voltage level output from the noise level detection unit 6. , The level of the detection signal E of the AGC detector 4 becomes the noise AGC detection level. Further, in the signal input section, since only the signal level detecting unit 5 operates, the input signal level from the optical transmitter is limited to the signal AGC voltage output from the signal level detecting unit 5,
The level of the detection signal E detected by the C detector 4 is the signal AG
The C detection level is reached.

The detector 8 which is the first detecting means shown in FIG.
Is provided to obtain an output signal D corresponding to an input signal from the BPF signal A from the BPF 3. In this specification, the wave detector 8 is referred to as a “signal wave detector 8”. The signal detector 8 includes a not-shown single-sided rectifying circuit for single-sided rectifying the BPF output signal A and a comparison circuit for comparing the single-sided rectified BPF output signal A with a required slice level Vth. To be done. An initial offset level is given to the slice level Vth used for comparison with the BPF signal A, and the slice level Vth is changed by following the level of the BPF signal A.
Therefore, the signal detector 8 uses the BPF signal A (not shown).
And an adder circuit for adding the integrated output to the slice level Vth, and the integrated signal integrated by the resistors and capacitors of the integrator circuit is added to the slice level Vth.
Is configured to be added to the initial offset of That is, the signal detector 8 is configured to take an intermediate position between peak detection and average value detection. Also, the slice level V
The initial offset level of th is set to a level higher than the noise AGC detection level of the detection signal E described above, so that the signal detector 8 does not detect the continuous wave noise generated in the no-signal section. There is.

The integrator 9 integrates the detection signal B detected by the signal detector 8 to obtain an integrated signal (envelope signal) C of the detection signal B. Then, the integrated signal C is shaped by the waveform shaper 10 including a hysteresis comparator to obtain an output signal D obtained by demodulating the input signal from the optical transmitter.

Therefore, according to the infrared receiver of the present embodiment, when continuous wave noise is generated from the lighting device, the continuous wave noise in the no signal section is AGC.
The wave is detected by the wave detector 4. Then, based on the noise detection output output from the AGC detector 4, the gain of the amplifier circuit 2 is controlled by the noise AGC voltage generated in the noise level detection unit 6, so that the AGC detector 4 detects the gain. The level of the detection signal E is changed to noise A
The GC detection level, that is, the slice level Vth of the signal detector 8 or less can be suppressed. As a result, it is possible to prevent the signal detector 8 from detecting the continuous wave noise component that is the disturbance light in the no-signal section.

Further, at the time of signal input, FIG.
As shown in, the slice level Vth of the signal detector 8 is
Following the level of the BPF signal A from the BPF 3, it rises from the initial offset level, and the signal detector 8 and the integrator 9 output the detection signal B and the integration signal C that are not affected by continuous wave noise as shown in the figure. Will be done.

The output waveforms of the signal detector 8 and the integrator 9 when impulse noise is generated from the lighting device are shown in FIG. 3 (b). In this case, if the level of the impulse noise generated in the lighting device is equal to or lower than the initial offset voltage of the slice level Vth of the signal detector 8, the signal detector 8 will not detect the impulse noise. On the other hand, when the impulse noise level exceeds the slice level Vth of the signal detector 8, the signal detector 8 will detect the impulse noise, but the signal detector 8 will detect the BPF signal A.
Since the single-wave rectified signal obtained by the single-wave rectification is detected, the detection time of impulse noise in the signal detector 8 is shorter than the detection time at the time of signal input (see FIG. 3A). Become. As a result, the integrated signal C output from the integrator 9 has the hysteresis level V of the waveform shaper 10.
The output signal D output from the waveform shaper 10 does not rise to 1 and is not affected by impulse noise.

FIG. 4 shows the operation waveform of each part of the infrared receiver of this embodiment. 4 (a) is an operation waveform of each part in the absence of ambient light noise, FIG. 4 (b) is an operation waveform of each part in the presence of continuous wave noise from the inverter fluorescent lamp, and FIG. 4 (c) is a rabbit start type. FIG. 5 is a diagram showing operation waveforms of respective parts in a state where there is impulse noise from the fluorescent lamp of FIG.

As shown in FIG. 4A, when there is no ambient light noise from the lighting device, BPF3 is generated in a no-signal section where there is no transmission signal (input signal) from the optical transmission device (not shown).
Since the BPF signal A from 1 is in a non-signal state, the detection signal B is not output from the signal detector 8 and the integration signal C of the integrator 9 is not changed, so that the output signal output from the waveform shaper 10 is output. D becomes high level indicating that there is no signal.

On the other hand, in the signal input section, the input signal is controlled to a constant level by the signal AGC operation by the AGC detector 4 and the signal level detecting section 5. Further, in the signal detector 8, the slice level Vth rises from the initial offset level following the output level of the BPF signal A, the slice level Vth is compared with the level of the BPF signal A, and the comparison result is set as the detection signal B. Output.
The level of the integrated signal C obtained by integrating the detected signal B by the integrator 9 is the hysteresis level V of the waveform shaper 10.
When it exceeds 1 (ON), the output signal D output from the waveform shaper 10 falls from the high level to the low level. Further, when the level of the integrated signal C output from the integrator 9 becomes equal to or lower than the hysteresis level V2 (OFF), the output of the waveform shaper 10 is made to rise from the low level to the high level. Thus, the output signal D obtained by demodulating the input signal of the optical transmitter from the waveform shaper 10
Will be obtained.

On the other hand, as shown in FIG.
When the continuous wave noise is generated from the inverter fluorescent lamp, the continuous wave noise in the non-signal section is detected by the AGC detector 4, and the noise level detection unit 6 is operated by this noise detection output, whereby the BPF signal A The continuous wave noise of is suppressed to a constant level.

In this case, since the level of the continuous wave noise of the BPF signal A becomes less than the initial offset level of the slice level Vth of the signal detector 8, the signal detector 8 should not detect the continuous wave noise. Become.

On the other hand, in the signal input section, the slice level Vth of the signal detector 8 rises following the output level of the BPF signal A, and the detected signal B is compared by comparing this slice level Vth with the level of the BPF signal A. Is obtained.
Then, the detected signal B is integrated by the integrator 9, and the integrated signal C is waveform-shaped by the waveform shaper 10 to be output, whereby the output signal D obtained by demodulating the input signal is obtained.

Further, as shown in FIG. 4C, when impulse noise is generated from the rabbit start type fluorescent lamp, even if impulse noise is detected by the AGC detector 4 in the no signal section. Since the signal level detection unit 5 and the noise level detection unit 6 do not operate, the gain adjustment is not performed in the amplification circuit 2, but at this time, the detection time of the detection signal B detected by the signal detector 8 is Since it is short, the integrated signal C output from the integrator 9 is
Does not exceed the hysteresis level V1 of the waveform shaper 10, and the output signal D output from the waveform shaper 10 is not affected by impulse noise.

In the signal input section, the signal level detector 5 operates to suppress the level of impulse noise, and the slice level Vth of the signal detector 8 follows the level of the input signal and becomes high. The level of impulse noise is equal to or lower than the slice level Vth of the signal detector 8, and the impulse noise is not detected by the signal detector 8.

As a result, according to the infrared receiving apparatus of the present embodiment, it becomes possible to suppress impulse noise generated between signals in the input signal section, which could not be suppressed conventionally. It is possible to prevent the output signal D of the waveform shaper 10 from being affected by impulse noise.

In the present embodiment, the infrared receiving device using infrared light has been described as an example, but this is merely an example, and the optical receiving device of the present invention is limited to infrared light. Alternatively, any receiving device that is affected by noise generated by an inverter fluorescent lamp or a rabbit start type fluorescent lamp can be applied to an optical receiving device that uses light other than infrared light.

[0056]

As described above, in the optical receiver of the present invention, when the amplified output from the amplifying means includes the input signal, the signal level control means causes the input signal to have a predetermined signal level. The gain control of the amplifying means is performed so that when the amplified output from the amplifying means contains a noise component, the noise level control means causes the noise component to reach a predetermined noise level. Since it is possible to suppress continuous wave noise and impulse noise that are input as ambient light noise by configuring the gain control of the input signal, the input signal is demodulated without being affected by continuous wave noise and impulse noise. It will be possible. Particularly, according to the optical receiver of the present invention, it becomes possible to suppress impulse noise at the time of signal input, which cannot be suppressed by the conventional infrared receiver.

Therefore, if the remote control system is constructed by using the optical receiver of the present invention, the microcomputer of the equipment equipped with the infrared receiver is conventionally installed in the environment where the ambient light noise is continuously generated. It is possible to solve the problem that the pulse noise keeps the busy state and the problem that the optical transmission reach decreases.

[Brief description of drawings]

FIG. 1 is a block diagram of an infrared receiver as an embodiment of the present invention.

FIG. 2 is a diagram showing an operation waveform of a detection signal in the infrared receiving device according to the present embodiment.

FIG. 3 is a diagram showing an operation waveform of a detection signal in the infrared receiving device according to the present embodiment.

FIG. 4 is an operation waveform diagram of each unit in the infrared receiving device according to the present embodiment.

FIG. 5 is a block diagram of a conventional infrared receiver.

6 is an operation waveform diagram of each unit in the infrared receiving device shown in FIG.

FIG. 7 is a block diagram of another conventional infrared receiver.

8 is an operation waveform diagram of each part in the infrared receiving device shown in FIG.

[Explanation of symbols]

1 light receiving element, 2 amplification circuit, 3 band pass filter (BPF), 4 AGC detector, 5 signal level detector, 6 noise level detector, 7 adder, 8 signal detector, 9 integrator, 10 waveform shaper

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04B 10/14 H04Q 9/00 341B 10/22 H04B 9/00 Y 10/26 R 10/28 H04L 25 / 02 303 25/03 H04Q 9/00 301 311 341

Claims (5)

[Claims] 1. A light receiving element for receiving an input signal from an optical transmitter, an amplifying means for amplifying a light receiving output of the light receiving element, a predetermined offset level, and an amplified output from the amplifying means. A first detection means for detecting the input signal by comparing a first threshold voltage whose level fluctuates according to the level with the amplified output; and the input signal from the detection output of the first detection means. Demodulating means for demodulating, signal level control means for controlling the gain of the amplifying means so that the input signal included in the amplified output has a predetermined signal level, and noise components included in the amplified output. And a noise level control unit that controls the gain of the amplification unit so that the noise level becomes a predetermined noise level. 2. The signal level control means comprises a second detection means for detecting the amplified output by comparing the amplified output of the amplification means with a second threshold voltage, and the second detection means. 2. The optical receiving device according to claim 1, further comprising: a signal level detecting unit that detects a signal level included in the amplified output from the detection output of. 3. The noise level control means compares the amplified output of the amplifying means with a third threshold voltage to detect the amplified output, and a third detecting means of the third detecting means. The optical receiving device according to claim 1, further comprising: a noise level detecting unit that detects a noise level included in the amplified output from a detection output. 4. The second level so that the noise level controlled by the noise level control means is lower than the signal level controlled by the signal level control means.
The optical receiving device according to claim 2 or 3, wherein the threshold voltage and the third threshold voltage are set. 5. The noise level controlled by the noise level control means is set to a level lower than an offset level given to the first threshold voltage. The optical receiver according to.