JPH0629783B2 - Light intensity detector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light amount detection device for detecting the intensity of a light amount by inputting an optical signal, converting an electric signal, and then performing an amplification process.

Conventional Technology A conventional method will be described with reference to FIGS. 4 and 5.

Conventionally, a configuration as shown in FIG. 4 has been adopted as a method of detecting the amount of light. When the light receiver 9 receives infrared light, the amplifier 10
To the input, a signal of about several tens of μV to several hundreds of mW is generated depending on the intensity of light. The signal is amplified by the pre-stage amplification section 12 of the amplification section 10 by 40 to 60 dB. Further, the amplifier 13 at the next stage amplifies the signal by 20 to 30 dB and outputs only the necessary frequency component through the band pass filter. The input / output characteristic of the conventional amplifier is as shown in FIG. From this relationship, the amount of light can be detected by the amplified signal.

Problems to be Solved by the Invention As described above, the conventional circuit configuration is merely for amplifying the optical input, so that it is uniform from strong input (several hundred mV) to weak input (several tens of μV). Therefore, the dynamic register becomes narrower in order to determine the level of the input signal by looking at the voltage level of the output signal. For example, if the input signal level is 100 mV, 5V, 20
In the case of μV, it is limited to 4V, which is within the range of about 1V.
In such an amplifying unit, when the amount of light from the infrared light emitting source is known, the determination becomes difficult because the dynamic range of the input / output characteristics is narrow. Therefore, the amount of light cannot be detected accurately.

Therefore, the present invention expands the dynamic range of input and output,
The purpose is to accurately detect the amount of light.

Means for Solving the Problems The present invention relates to a light receiving section for converting a light quantity into an electric signal, a pre-stage amplifying section for amplifying an output signal of the light receiving section, and a gain output section for outputting a signal amplified by the pre-stage amplifier section. Depending on the signal from, the gain control unit with gain reduction characteristics that can change the amplification degree, the detection unit for converting the output from this gain control unit into the gain output, the signal from this detection unit The gain output section outputs the gain output and outputs the gain output section to the gain control section to return the gain output section output and the gain output section. It is composed of a comparison unit for comparing the ability.

By the above means, the present invention can widen the dynamic range and can obtain an output signal according to the light amount.

Embodiment An embodiment of the present invention will be described with reference to FIGS. In FIG. 1, the light emitted from the light emitting portion 9 is received by the light receiving portion 1 and the optical signal is converted into an electric signal. The amount of light and the output voltage (voltage at point B) of the light receiving section 1 are shown in FIG. This graph is a diagram showing the relationship between the amount of light and the point B voltage.

This signal enters the amplification unit 2. The signal that has entered the amplification unit 2 is amplified by the pre-stage amplification unit 3, and that signal enters the gain control unit 4 that has a gain reduction characteristic that can change the amplification degree according to the output of the gain output unit 7. The signal of which the frequency of the optical signal used in the bandpass filter 5 is selected enters the detection unit 6 for converting it into the output of the gain output unit.
The signal passes through the gain output section, which is returned to the gain control section 4, as an output of the gain output section, and enters the comparison section 8. The relationship between the C point voltage and the B point voltage is as shown in FIG. A circuit using a general gain output circuit keeps the voltage at the point A constant regardless of the magnitude of the voltage at the point B. By configuring the circuit to fix the voltage at the point A, the gain output unit 7 The output signal of is as shown in FIG. By using the output signal of the gain output section 7, the dynamic range of input / output is expanded as compared with the conventionally used amplifier circuit for receiving a wireless signal. The potential at the point C enters the comparison unit 8,
A / D conversion is performed, and an output signal according to the amount of light is obtained.

EFFECTS OF THE INVENTION As is apparent from the above-described embodiments, the present invention can detect the magnitude of the light amount with high accuracy by the configuration using the amplifier circuit using the gain output circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an input / output characteristic view of an amplifier section of the same embodiment, FIG. 3 is an input / output characteristic view of a light receiving section of the same embodiment, and FIG. Is a block diagram showing a configuration of a conventional example, and FIG. 5 is a conventional output characteristic diagram. 1 ... Light receiving part, 2 ... Amplifying part, 3 ... Pre-stage amplifier part, 4
...... Gain control unit, 6 ...... Detection unit, 7 ...... Gain output unit, 8
…… Comparison department.

Claims (1)

[Claims] 1. A light receiving section for converting a light quantity into an electric signal, a pre-stage amplifying section for amplifying an output signal of the light receiving section, and a gain control having a gain control characteristic for changing an amplification degree according to an output of a gain output section. Section, a detection section for converting the output from the gain control section into an output of the gain output section, and a gain output section for outputting a signal from the detection section. The output from the gain output section is returned to the gain control section. A light quantity detection device comprising an amplification section for extracting the output of the gain output section and a comparison section for A / D converting the signals from the amplification section, comparing and outputting the signals.