JPH0426591B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an infrared imaging device, and particularly relates to the transmission of analog video signals between devices, and improves noise resistance by using a direct current regeneration function provided for a temperature measurement function. This provides an excellent signal transmission system free of DC drift.

[Industrial application field]

The present invention relates to a device that detects an infrared signal emitted from an object, converts the detected signal into an image signal, and visualizes the signal.

[Conventional technology]

An overview of an infrared imaging device that is a conventional example of the present invention will be described.

FIG. 4 is a diagram showing the configuration circles of the optical system, in which a linear array photoconductive multi-element infrared detector 1 is used as a sensor, and scanning is performed by a rotating polygon mirror 2. The lens system is composed of a main lens 3 and two lily lenses 4, and forms an image on the sensor. Further, a reference light source 5 is provided to provide a temperature measurement function. This temperature measurement function will be briefly described below.

An easy-to-configure AC amplifier is usually used to amplify the small video signal from the sensor, but in this case the DC component of the signal is lost, so in order to regenerate the DC component, the sensor reference light source must be made to look at the sensor reference light source at a certain moment. After the AC amplifier has reached a sufficiently high signal level, the video signal level at that moment is fixed at a certain DC level (called a clamp level). This operation is called clamping,
The circuit that accomplishes this is called a clamper.

This clamp function will be explained in relation to the temperature measurement principle. The amount of infrared radiation emitted from an object is determined by the so-called Planck's law once the temperature of the object is determined. According to Planck's law, the higher the temperature, the greater the amount of emitted light. The infrared detector receives this infrared emitted light and converts it into an electrical signal, and the greater the amount of light, the greater the photoelectrically converted electrical signal. Therefore, the higher the temperature of an object, the higher the level of the video signal from that object. However, the video signal from an object is obtained as a relative value, and it is impossible for the infrared light incident on the detector to be zero, so if you want to know the temperature from the video signal, you will need to devise something. do. One way to do this is to image a reference object with a known temperature, add this to one end of the video signal, and if this level can be fixed at a certain DC level using an electrical clamper circuit, the image of the actual object being imaged can be The signal level is determined as a relative value from this DC level,
Therefore, since the temperature is uniquely determined by correspondence with Planck's law, temperature measurement becomes possible.

Fig. 4 shows a method of adding this reference light source to the video signal by attaching a claw to the rotating rotor in synchronization with the scanning of the surface of the rotating polygon mirror 2, and using the claw as the reference light source. . The claw portion is placed at the focal point of the main lens 3 to prevent deterioration in the amount of light incident on the sensor due to defocusing.

FIG. 5 shows an example of the relationship between clamp timing (tc) and effective video period (te). In this figure, a is a synchronization signal, b is an effective video period, and c
is a clamp signal, and d is a video signal. Here, the effective video period is a time range in which a video signal is actually adopted as an image, and at this time, the infrared detector must be looking at the object to be imaged. Also, at the clamp timing tc, the infrared detector must be looking at the reference light source. The synchronizing signal a in FIG. 5 is a synchronizing signal that is outputted as one pulse per surface of the rotating polygon mirror 2, and the clamping operation is performed once per scanning of one surface. Tp indicates the period of the synchronization signal. In this way, the DC level of the reference light source after undergoing the clamping operation is constant and does not change with changes in the video signal as with simple AC amplification.

Next, using FIG. 6, a description will be given of how this video signal d is transmitted from the camera section 10 to the data processing section. The amplifier system 12, which has the same number of elements as the detector 11, is composed of N channels. The video signal amplified to an appropriate level by the amplifier 12 is passed through a clamper 13 to provide a temperature measuring function. The clamp level of all channels after passing through the clamper 13 is the level of the reference light source and has a constant DC level.
This is also constant for signals after the video signals of each channel are multiplexed in time series. This figure shows a video signal transmission method according to the conventional method. In the multiplexer 14, the multiplexed signal is simply transmitted to the data processing device side 20 through the line driver 15 by DC coupling, and the data is processed. On the device side 20, both ends of the terminating resistor of the coaxial cable 16 are received by a differential amplifier 17. Although this method simplifies the circuit configuration, it has the drawback of large DC drift because the transmission is based on DC coupling.

[Problem that the invention seeks to solve]

An object of the present invention is to multiplex the clamp function provided to realize the temperature measurement function before and after the video signal path, thereby realizing signal transmission in the transmission path by AC coupling, and eliminating DC drift of the signal. The purpose of the present invention is to provide a video signal transmission method that can be used to store video signals.

[Effect]

The present invention has a function of clamping the video signal level by a reference light source added to add a temperature measurement function to an infrared imaging device, and an operation of aligning the DC level of the video signal of each channel of a multi-element sensing element for temperature measurement. Transmission of video signals between devices
This is done through AC coupling, and is used in addition to reproducing the DC component on the receiving side.

〔Example〕

An embodiment of the present invention will be described using FIGS. 1 and 2. However, in FIG. 1, the signal processing stages preceding the multiplexer 14 in FIG. 6 are omitted.
In comparison with the configuration shown in FIG. 6, in FIG. 1, the output of the line driver 15 is AC-coupled using a capacitor 21, and on the data processing device side, a clamper 22 is inserted after the differential amplifier 17, which is a receiver.
The video signal level of the reference light source is fixed at a certain DC level. FIG. 2 is a time chart showing signal processing of the present invention. If the video signals of Ch1 to N showing the signals of each channel in Fig. 2 are taken from the output stage of the clamper 13 shown in Fig. 6, the signals are processed so that their DC levels within the tc time are constant. be done. Therefore, even after multiplexing these video signals in time series, tc
The DC level within time remains a constant value. This level then becomes the signal level of the reference light source. As a result of multiplexing so that this level is a constant value, as shown in FIG. 1, it becomes possible to regenerate the DC component by transmission by AC coupling and clamping operation on the receiving side.

Here, the signal that is valid as a video signal is shown in Figure 5.
Only the signal for the tc period is necessary; the others are unnecessary.
Therefore, the signal shown in FIG. 5 tc does not necessarily have to be a multiplexed signal of the outputs of channels 1 to N, but may be an output signal of any channel having a good signal-to-noise ratio. Of course, multiplexed output may also be used.

FIG. 3 shows another embodiment of the invention. Figure 3 shows that video signals of positive polarity and negative polarity are simultaneously transmitted from line drivers 15-1 and 15-2, and a differential amplifier is used on the receiving side to detect the difference signal, thereby increasing the level to twice the level. The output signal of this differential amplification is taken out as a signal, and is passed through a clamper 22 since it is an AC coupled signal. The clamp level of the clamper 22 is the video signal level when looking at the reference light source. The method shown in Figure 3 is the first
Compared to the method shown in the figure, this method has the effect of suppressing noise components due to crosstalk from the ground line.

〔Effect of the invention〕

According to the present invention, a clamp function added to provide a temperature measurement function can be used to transfer video signals between devices.
Since it can also be used on the receiving side after transmission by AC coupling, signal transmission with less DC drift of the signal can be performed.

[Brief explanation of drawings]

1 and 3 are examples of the present invention, FIG. 2 is a diagram for explaining an example of the present invention, FIGS. 4 and 6 are conventional examples, and FIG. 5 is a diagram for explaining the conventional example. This is a diagram for In the figure, 11 is an infrared multi-element detector, 12
is an amplifier, 13 is a clamper, 14 is a multiplexer, 15 is a line driver, 21 is a capacitor,
16 is a coaxial cable, 17 is a differential amplifier, and 22 is a clamper.

Claims (1)

[Claims] 1. An infrared imaging device that displays an output signal from an infrared detector as an image, comprising: a first clamp circuit that clamps the level of a reference light source, which is a reference for temperature measurement, to a DC level; and an infrared detector. a transmission line that transmits the output signal from the transmission line and the DC level signal by AC coupling; and a second clamp circuit that receives the signal from the transmission line and clamps the DC level signal to a predetermined DC level. An infrared imaging device characterized by: