JPH0257852B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pyroelectric infrared imaging device for displaying the temperature distribution of an object as a two-dimensional image.

Conventional configurations and their problems There is a pyroelectric infrared imaging tube that uses a pyroelectric material as a target as a method of converting the temperature distribution of an object into a two-dimensional image, and it is noteworthy that it can be imaged using a normal television method. has been done. To explain this operation, infrared rays emitted from the surface of the subject according to its temperature distribution are focused on the target using an optical system, and when an infrared intensity distribution image is formed on the target, the target made of pyroelectric material This causes a temperature change distribution on the target surface, and further induces a charge distribution due to the pyroelectric effect. By reading this by electron beam scanning, a temperature distribution image signal is obtained. By the way, the pyroelectric effect is a phenomenon in which electric charges are induced by temperature changes, so when observing a stationary object, it is necessary to interrupt the incident infrared rays at a rate of several to 10 times per second using a chopper. .

The basic configuration of an imaging device using the above-mentioned pyroelectric infrared imaging tube is shown in FIG. The infrared rays incident on the target 2 of the pyroelectric infrared imaging tube 1 are interrupted by a chopper 4 rotated by a motor 3 to form a charge distribution image on the target 2. This charge distribution image is read out by scanning the target 2 with an electron beam 6 using a deflection coil 5.
The read video signal is amplified by an amplifier 7, subjected to necessary signal processing by a signal processing section 8, and then supplied to a display device 9 for display. Further, a light emitter 10 and a photodetector 11 attached to the chopper 4 detect the chopping timing of the chopper 4, and control the speed of the motor 3 in synchronization with the vertical synchronization of the electron beam. That is, when opening and closing the chopper 4 every 8 fields, for example, a signal obtained by counting down the vertical synchronization signal VD from the television standard synchronization signal generator 12 to 1/16 and a signal from the photodetector 11 are output to the phase comparator circuit 13. The error signal is sent to the motor control circuit 14, and the speed of the motor 3 is controlled so that the chopper 4 is always opened and closed every 8 fields. The VD is sent to the cathode power supply 15, the deflection power supply 16, etc. to control electron beam scanning, and is sent to the signal processing unit 8 to control the signal acquisition timing and the like.

Now, in a pyroelectric infrared imaging device, target 2 has a thermal time constant (the thermal time constant of pyroelectric material is 2
(about 8 seconds), so even if the signal is read out by scanning each field with an electron beam using the standard television method, the charge remaining in the previous field and the target temperature change between each field until the next readout is The sum of the charges induced by this becomes the charge on the target 2, and the magnitude of the read signal amount changes in each field. Also,
There are ways to read signals in any field, such as reading every other field, or reading 1 field but not reading 3 fields, or reading 2 fields but not reading 2 fields, instead of reading the signal every field. The magnitude of the signal output varies for each field depending on the reading method. The maximum signal output field also changes. Furthermore, even if the target pyroelectric material is changed, the content of the signal output and the maximum signal output field will change due to the difference in material constants.

When the contents of the signal output field change in this way, for example, the signal acquisition timing for signal processing in the signal processing section 8 changes, so it is necessary to adjust the timing of the signal processing section 8 each time. Therefore, when changing the signal readout method in the infrared imaging section of the pyroelectric infrared imaging device, a problem arises in that the timing in the signal processing section 8 must be adjusted each time.

On the other hand, from the point of view of delaying the output signal, it is possible to use a delay circuit to change the signal phase, but this would require the current chopping speed of several to 10 times per second. At present, it is difficult to solve the problem of output signal delay because delay element technology for the video signal band that allows delays of 100 msec or more has not yet reached that level.

Purpose of the Invention The present invention provides a pyroelectric infrared imaging device for forming a temperature distribution line of an object by receiving infrared rays emitted from the object. The purpose of this invention is to enable a desired output image signal to always be obtained at a predetermined phase position with respect to the phase of a reference signal, and further to enable signal processing in accordance with changes in the output signal.

Structure of the Invention In order to achieve the above object, the present invention has a reference signal for setting a synchronization signal for each part of an imaging device that captures an infrared image emitted from a subject, and the phase of this reference signal and the phase of a chopper opening/closing signal are provided. By relatively changing the phase of the reference signal and the phase of the chopper opening/closing signal, the phase of the chopper opening/closing signal is always changed to a predetermined phase position with respect to the phase of the desired output image signal. It is something to do.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

For example, when a chopper is opened and closed every 8 fields in a pyroelectric infrared imaging device that captures images using a normal television method, a pulse with a period of 1/60 second shown in FIG. 2a is used as the reference signal. Figures b to e in Figure 2 are pulses counted down to 1/2, 1/4, 1/8, and 1/16 based on this pulse, respectively, and are used for the deflection power supply 16, cathode power supply 15, and signal processing in Figure 1. 8 and the phase comparator circuit 13.

The signal e is used as the reference signal for controlling the motor for opening and closing the chopper, and the signal e is sent from the television synchronization signal generator 12 to the phase comparator circuit 13 for phase comparison, and the motor is controlled. This controls the opening and closing of the tipper. Normally, the relationships among the phases of each part of the imaging device, the opening/closing phase of the chopper, and the phase of the signal output field from the target 2 are as shown in a, b, c, and d in Fig. 3, respectively, with respect to the reference pulse as a reference signal. In a relationship. Here, b is for a part other than the chopper opening/closing synchronization among the parts of the imaging device that are synchronized with reference to the reference pulse, and a synchronization signal for the deflection power source is shown as a typical example. Hereinafter, this signal will be used as a representative synchronization signal for each part of the imaging device.
Furthermore, the signal output field immediately after the chopper is opened is designated as the 1st field, the 2nd field, and the 16th field.
Number the fields as shown in Figure 3 until just before the next shutter opens.

Next, when the phase conversion of the present invention is performed, that is, by changing the opening/closing phase of the chopper by n fields with respect to the reference signal, for example, by delaying it by 2 fields (1/30 seconds), as shown in Fig. 4. With respect to the pulse signal a as a reference signal, the synchronization signal b of each part of the imaging device, the chopper opening/closing c, and the signal output field d have a phase relationship as shown in Fig. 3 when the chopper phase is not changed. When compared, it can be seen that the signal contents change, such as the 15th field enters the first field, the 16th field enters the second field, etc. before changing the phase.

On the other hand, the reference signal itself for opening and closing of the chopper is
By changing the field, for example, by delaying the signal by one field (1/60 second), the phase relationship will become as shown in Figure 5, and if you compare it with the case where the phase of the reference signal in Figure 3 is not changed, , it can be seen that the signal contents change and enter the first field before changing the phase, the second field enters the second field, the third field enters the second field, and so on.

In other words, by changing the opening/closing phase of the chopper or the reference signal phase, the position of the signal output field in normal operation is replaced with a signal output shifted by an arbitrary number of fields.In other words, the phase of the output signal is changed relative to the reference signal. This means that it can be changed.

Example 1 In a pyroelectric infrared imaging device, in the case of the normal operation signal readout method, the phase relationship between the reference pulse a, the chopper opening/closing b, and the output signal c in the continuous field readout method is as shown in FIG. The relationship is as follows, and the signal readout method is as shown in d, in which the signal is read once each during opening and closing of the chopper, with the maximum signal output field. However, the maximum signal output field in case c is the 4th field for the positive image signal and the 12th field for the negative image signal, which do not match the 8th field and 16th field of the maximum signal output field for case d. Therefore, when reading signals once each time the chopper opens and closes, by advancing the phase of the chopper by 4 fields or delaying the phase of the reference pulse as a reference signal by 4 fields, it is possible to relatively read out the signal as a reference signal. With respect to the reference pulse a, the chopper opening/closing phase and the output signal phase are e and f, respectively, and the maximum output field is essentially the same field, and the phase with respect to the reference pulse is always the 4th field and the 12th field. The field of maximum signal output can be located.

Example 2 In the case of a signal readout method for normal operation in a pyroelectric infrared imaging device, as shown in FIG. The phase relationship of the output signal d is determined by reading the maximum signal output field once each time. However, the maximum signal output fields in case c are the 7th field and 15th field for positive and negative image signals, respectively, which do not match the 8th field and 16th field in case d. Therefore, when reading the signal once each time the chopper opens and closes, by advancing the phase of the chopper by 1 field or delaying the phase of the reference pulse as a reference signal by 1 field, it is possible to relatively read the signal as a reference signal. With respect to the reference pulse a, the chopper opening/closing phase and the output signal phase are e and f, respectively, and the maximum output field is essentially the same field, and the phase with respect to the reference pulse is always the 7th field and the output signal phase.
The field with the maximum signal output can be located in 15 fields.

FIG. 8 shows an embodiment of a circuit for performing the above phase conversion. This circuit corresponds to the synchronization signal generator 12 of FIG. In addition, in the present invention, everything other than this part is the same as in FIG. 1. In the figure, 21 is a reference pulse generator that generates a reference pulse 21 with a period of 1/60 seconds. These reference pulses are frequency-divided by frequency dividers 22, 23, 24, and 25 at predetermined frequency division ratios, respectively, and are divided by a deflection power source 16, a cathode power source 15, a signal processing section 8, and a phase comparator circuit 1.
3 synchronization signals are generated. A frequency divider 25 divides the reference pulse into 1/16, a phase shifter 26 changes the phase corresponding to a predetermined number of fields, and the pulse is sent back to the phase comparator circuit 13. The amount of phase shift by the phase shifter 26 is determined as in each of the embodiments described above.

Incidentally, when the reference pulse is phase-shifted, a phase shifter may be used in the same manner.

Effects of the Invention As described above, the present invention is capable of adjusting the phase of the reference signal and the chopper opening/closing phase for setting the synchronization signal of each part of the imaging device when forming a temperature distribution image of the object by receiving infrared rays emitted from the object. This is a pyroelectric infrared imaging device that changes the phase of the output signal relative to the reference signal by changing the phase of the output signal relative to the reference signal, and it always captures the desired signal regardless of the signal charge readout method or the pyroelectric material. An output, for example a maximum signal output field or a high resolution output field, can be taken into the signal processing section. Especially when the signal readout method can be switched in the infrared imaging unit to obtain different infrared signal information, the maximum signal output field or high-resolution output field changes, so the acquisition timing in the signal processing unit changes. However, by using the present invention, at the same time as switching the method of signal readout in the infrared imaging section,
If you set the phase of the maximum signal output field or high-resolution output field to match the timing of the signal processing section capture field position in advance, the maximum output signal of that readout method will be automatically captured by the signal processing section and the signal This produces the effect of processing. Also,
If the output signal phase conversion according to the present invention is performed on an imaging section using any signal readout method, processing can be performed with a single signal processing section, and the effect will be exhibited.

Pyroelectric infrared imaging devices use pyroelectric material as a target, so the response speed is slow.
Signal processing is performed to improve S/N. Signal processing is performed by taking in the output signal, but the effects of the present invention are remarkable in, for example, a system in which signal processing is performed by taking in one field of the maximum signal output depending on whether the chopper opens or closes. .

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a conventional pyroelectric infrared imaging device, Fig. 2 is a waveform diagram of various reference synchronization signals used in the pyroelectric infrared imaging device according to the present invention, and Fig. 3 shows phase conversion. 4 to 7 are waveform diagrams of signal waveforms of the pyroelectric infrared imaging device according to the embodiments of the present invention, and FIG. 8 is a waveform diagram of the signal waveforms during normal operation in which no operation is performed. FIG. 2 is a block diagram showing a synchronization signal generator section of the pyroelectric infrared imaging device. 1...Pyroelectric infrared imaging tube, 2...Target, 3...Motor, 4...Chopper, 8...
Signal processing unit, 9...Display unit, 12...Synchronizing signal generator, 13...Phase comparison circuit, 14...Motor control circuit, 21...Reference pulse generator, 22-2
5... Frequency divider, 26... Phase shifter.

Claims (1)

[Claims] 1. It has a reference signal for setting a synchronization signal for each part of an imaging device that captures an infrared image emitted from a subject, and includes means for relatively changing the phase of the reference signal and the phase of the chopper opening/closing signal. ,
By relatively changing the phase of the reference signal and the phase of the chopper opening/closing signal, a desired output image signal is brought to a predetermined phase position with respect to the phase of the reference signal. Electric type infrared imaging device.