JPS6334964B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that detects an object based on a detection signal from a detector, such as a photodetector that receives light such as infrared rays, ultraviolet rays, and visible light and generates an electrical signal. The present invention relates to a signal processing method for a horizon detector mounted on a spin satellite, a three-axis stable satellite, etc., and detects the edge of the earth using infrared rays, and particularly relates to a signal processing method for improving the minimum detection width of a horizon detector, etc.

The present invention also aims to improve the minimum detection width of the horizon detector without impairing the S/N ratio. An explanation will be given below using a horizon detector as an example.

The horizon detector uses the satellite's spin, self-rotation, and self-scanning to detect the edge of the earth (horizon) with an infrared detector, and detects the flight attitude of the artificial satellite from the time width.

Typically, thermal detectors such as pyroelectric infrared detectors, thermistors, and bolometers are used as these horizon detectors.

The basic configuration of a horizon detector using these thermal detectors is generally as shown in FIG. In the figure, 101 is an infrared detector, 102 is an equalizer, 1
03 is a differentiator, and 104 is a waveform shaper.

Now, suppose that the infrared input a shown in FIG. 2 is input to the infrared detector 101 shown in FIG. can get. This equalizer output is differentiated by a differentiator 103, resulting in a waveform shown in FIG. 2c. The output of this differentiator 103 is supplied to a waveform shaper 104 having a positive comparison level TH1 and a negative comparison level TH2, and outputs the pulse type signal shown in FIG. 2d. The infrared input end is detected by these operations.

Here, steady state waveform 1 of equalizer output waveform b
02a, it can be seen that the differential coefficient in this state is extremely small. Further, the output attenuation waveform 103a of the differentiator 103 is determined by the magnitude of the time constant of the differentiator 103. Therefore, if the time width of the infrared input is smaller than the time constant of the differentiator 103, a fall occurs before the attenuation waveform 103a reaches 0, and the positive and negative waveforms of the output of the differentiator 103 are Becomes asymmetrical. This situation is shown as a damped waveform 103b in FIG. 2c. This attenuation waveform 103b shows the differential output waveform of the differentiator 103 when the infrared input time width in FIG. suddenly becomes negative, and the positive and negative waveforms become asymmetrical. When the differential output is supplied to the waveform shaper 104 in this state, the time Δt
This causes an error in the detection time width of infrared input. In this specification, the minimum time width that does not cause an error in the detection time width is defined as the minimum detection width.

By the way, as described above, the decay time of the output waveform of the differentiator 103 is determined by the time constant of the differentiator 103. The time constant of this differentiator 103 has a mutually contradictory relationship with the S/N ratio and minimum detection width of the horizon detector, and if the time constant of the differentiator 103 is made smaller in order to improve the minimum detection width, the
There was a problem in that the N ratio deteriorated, and conversely, if the time constant of the differentiator 103 was increased in order to improve the S/N ratio, the minimum detection width increased and the resolution decreased. For this reason, conventionally, especially in horizon detectors that handle weak infrared input, it has been difficult to improve the minimum detection width because the S/N ratio must be increased.

The present invention focuses on the fact that the differential coefficient of the steady output waveform 102a of the equalizer 102 described above is extremely small and that the attenuation terms 103a and 103b of the differential output waveform are determined by the time constant of the differentiator 103, and The object edge is detected based on the signal obtained by detecting the maximum value of the differential waveform and improving the minimum detection width without compromising the S/N ratio. An embodiment of the invention will be described in detail with reference to the drawings.

In FIG. 3, 201 is an infrared detector;
Reference numeral 2 denotes an equalizer, which is the same as the infrared detector 101 and equalizer 102 shown in FIG. 203
is a differentiator, resistor R203, capacitor C203
and a switch connected in parallel to resistor R203.
Consists of SW203. The values of resistor R203 and capacitor C203 may be the same as in the case of FIG. 1, and the time constant is not changed. 204 is a buffer amplifier, 20
5 is a positive peak position detection circuit, 206 is a negative peak position detection circuit, and 207 is a peak reset pulse generator. 208 is a waveform shaping circuit having the same configuration as the waveform shaping circuit shown in FIG. Now, suppose that the infrared input shown in FIG. 4a is incident on the infrared detector 201. The output of the infrared detector 201 is sent to the equalizer 2
02 and is guided to a differentiator 203. A switch SW203 connected in parallel to the resistor R203 of this differentiator 203 is normally "open". This SW20
3 is always open, the differentiator output passing through the buffer amplifier 204 is the differentiator output c in FIG.
, as shown in FIG. 4b.

When the waveform shown in FIG. Pulses c and d are generated at the peak positions, respectively.
These pulses c and d are input to the peak reset pulse generator 207 and further converted into a shorter pulse e, which changes the parallel switch SW 203 from the "open" state to the "closed" state for that period of time. As a result,
The charge accumulated in the capacitor C203 of the differentiator 203 is instantly discharged. At the same time, the buffer amplifier 20
The output of 4 suddenly decreases, resulting in the waveform shown by the solid line in FIG. 4f. That is, when the parallel switch SW203 is open, the infrared input rises as shown in FIG. Get closer. However, due to pulse e, the parallel switch
When SW203 is closed, capacitor C203
The accumulated charge instantly becomes 0 and the buffer amplifier 204
The output also suddenly becomes 0. Then, at the next fall or fall of the infrared input, the signal suddenly rises or falls to the positive or negative side again from the 0 position. When this waveform signal f is applied to the waveform shaping circuit 208, the waveform shown in FIG. The minimum detection width can be reduced to approximately the width of each pulsed portion of the signal f in FIG. 4, which is a significant improvement. Therefore, the resolution is significantly improved. In this case, since the time constant of the differentiator 203 is not changed in any way, the S/N ratio is not impaired in any way.

Note that the shaded portion 204a in FIG. 4 shows the waveform before the minimum detection width improvement according to the present invention, and if this waveform is directly supplied to the waveform shaping circuit 208, a measurement error of Δt will occur as described above.

As described above, the present invention detects the maximum value of the differential waveform obtained by differentiating the detection signal from a detector such as an infrared detector in a signal processing method of a device that detects the edge of an object by differentiating the detection signal from a detector such as an infrared detector. This signal processing method detects the edge of an object by resetting the differential waveform and then shaping the waveform.The minimum detection width can be significantly reduced without any loss in the S/N ratio, resulting in a large resolution. improves. Therefore, if used in horizon detectors mounted on artificial satellites, etc.,
The resolution of earth edge detection has been greatly improved and is extremely effective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional horizon detector, FIGS. 2 a to d are waveform diagrams showing the operation of each part in FIG. 1, and FIG. 3 is a horizon detection system using the signal processing method according to the present invention. A block diagram showing the configuration of the device,
FIGS. 4a to 4g are waveform diagrams showing the operation of each part in FIG. 3. 101,201...Infrared detector, 102,2
02...Equalizer, 103,203...Differentiator, 104,208...Waveform shaper, 204...
Buffer amplifier, 205...Positive peak position detector, 2
06... Negative peak position detector, 207... Peak reset pulse generator.

Claims (1)

[Claims] 1. Detecting a signal from an object with a detector, differentiating the obtained detection signal, detecting the maximum value of the differential waveform, resetting the differential waveform, and then shaping the waveform. A signal processing method characterized by 2. The signal processing method according to claim 1, wherein the detector is an infrared detector. 3. The signal processing method according to claim 1, wherein the object is the earth and the detector is an infrared detector.