JPH0726871B2 - Infrared sensor signal processing circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared sensor signal processing circuit for digitizing and processing an output signal of an infrared sensor.

[0002]

2. Description of the Related Art Conventionally, when a signal from an infrared sensor is handled by a digital circuit, it is difficult to digitize the signal as it is because the output signal level of the sensor is extremely small. Therefore, after amplification by an amplifier, A / D conversion is performed. There is. Since infrared sensors generally have variations in sensitivity, when a plurality of infrared sensors are used, sensitivity correction is performed after A / D conversion so that apparently uniform sensitivity is obtained.

[0003]

However, the output signal from the infrared sensor has the property that the portion that contributes as image data is extremely small compared to the amplitude of the entire signal, that is, it contains a large amount of direct current component. Because of its nature, the A / D converter must be of high precision and high resolution because it is A / D converted. Further, since the amplifier needs to amplify the direct current component as well, it is required to have a good linearity.

[0004]

In order to solve such a problem, the present invention provides a DC component determined for each infrared sensor.
Pre-stored when the infrared sensor is selected
Correction DC distribution stored in correspondence with the infrared sensor
Signal and the signal for infrared sensor sensitivity correction
Output correction signal generator and selected infrared sensor output
The correction DC component signal is subtracted from the force and
The result is determined by the signal for infrared sensor sensitivity correction.
And a differential amplifier that amplifies by gain .

[0005]

[Operation] DC component of sensor output signal and correction signal generator
Since the direct current component output from is subtracted by the differential amplifier, only the image signal component remains, only the image signal is amplified, and the amplified signal is A / D converted. Therefore, amplification and A / D conversion are performed. Only the image component needs to be handled, the linearity of the amplifier is small, and the A / D converter with high precision and high resolution is unnecessary.

[0006]

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 1 is an infrared sensor, and there are a plurality of infrared sensors 1, one of which is selected by a drive circuit 2. The output signal of the infrared sensor 1 is supplied to the differential amplifier 3.

The signal output from the infrared sensor 1 is as shown in FIG. 2 (a). FIG. 2 shows that there are three infrared sensors, which are sequentially switched by the drive circuit 2.

The shaded area in FIG. 2 (a) shows the portion that contributes as an image signal component, and the other portions are DC components. This DC component has a unique value for each sensor, and the value is stored in advance in the correction signal generator 4,
The selection is made in synchronization with the selection of the infrared sensor 1 by the drive circuit.

Therefore, the correction signal generator 4 outputs the signal shown in FIG. 2B corresponding to the direct current component of the infrared sensor 1, and the signal is supplied to the differential amplifier 3 via the D / A converter 5. To be done. As a result, the differential amplifier 3 subtracts the signal shown in FIG. 2 (b) from the signal shown in FIG. 2 (a), and outputs the signal shown in FIG. 2 (c).

At this time, the differential amplifier 3 includes the correction signal generator 4
It is set to the degree of amplification determined by the signal given from. This is a correction process performed to match the sensitivities of a plurality of infrared sensors, because the sensitivities of the sensors are not the same.

At this time, the signal stored in the correction signal generator 4 is determined, for example, so that when the infrared sensors detect infrared radiation from the same object, the differential amplifier 3 outputs the same level output signal. ing.

The signal amplified by the differential amplifier 3 is converted into a digital signal by the A / D converter 6, image-corrected by the image correction circuit 7, and converted into a signal suitable for display by the television conversion circuit 8. .

In this device, the signal amplified by the differential amplifier 3 is only the signal of the amplitude that is truly necessary as shown in FIG. 2 (c), and the DC component is not amplified as in the conventional case. This means that if the amplification is the same, the output voltage is low,
The range in which the linearity of the amplifier is secured can be narrower than that of the conventional one.

Also, the A / D converter 6 is not necessary to digitize a large amplitude one as in the prior art, but only a necessary amplitude one is digitized as shown in FIG. 2 (c). The minimum number of bits is sufficient. This is a significant improvement compared to the use of a device having a large number of bits because it has conventionally been necessary to digitize even the DC component. That is, the A / D converter 6 does not need to have high precision and high resolution, which is very economical.

[0015]

As described above, according to the present invention, the direct current component of the infrared sensor is removed and then the amplification and the A / D conversion are performed. Therefore, the linearity realization range of the amplifier may be narrow, and the A / D conversion is possible. Since the device can be improved with a small number of bits, it is possible to provide an economical device.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram showing the waveform of each part.

[Explanation of symbols]

 1 infrared sensor 2 drive circuit 3 differential amplifier 4 correction signal generator 5 D / A converter 6 A / D converter 7 image correction circuit 8 television conversion circuit

Claims (1)

[Claims] 1. A direct current component is removed from outputs of a plurality of infrared sensors.
After removing it, please adjust the sensitivity of each infrared sensor.
In the infrared sensor signal processing circuit that digitizes the data, the direct current component determined for each infrared sensor is stored in advance.
When one infrared sensor is selected, its infrared
The correction DC component signal stored in correspondence with the line sensor
The sensitivity of the selected infrared sensor as well as transmitting
A correction signal generator for outputting a normal use signal, and the selected signal
The correction DC component signal is subtracted from the infrared sensor output.
And the subtraction result is sent to the infrared sensor sensitivity correction signal.
Infrared sensor signal processing circuit, comprising: a differential amplifier that amplifies by a gain determined by the signal.