JPH05347189A - Standard light source - Google Patents

Abstract

PURPOSE:To obtain a standard light source which generates no correcting error even though the luminous wave length distribution is changed, and furthermore, to obtain a standard light source in which the output signal of a light detector is not necessary to transmit to a station on the ground. CONSTITUTION:The light wave length of the output of a light source 1 is limited by using an interference filter 9, or the light wave length is limited by using a laser diode instead of the light source 1 and the interference filter 9. And a part of the light output of the light source or the laser diode is monitored by a light detector 3, and the light source 2 is controlled so as to make its output constant.

Description

Detailed Description of the Invention

[0001]

This invention is mounted on an artificial satellite,
The present invention relates to an improvement of a standard light source for calibrating the sensitivity of a CCD camera sensitive to only one specific wavelength λ in outer space.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an example of calibration and use of a standard light source for sensitivity calibration of a conventional CCD camera. 1 is a halogen lamp, 2 is a power source, 3 is a photodetector, 4 is the earth, 5
Is an optical system, 6 is an optical path switching mirror, 7 is a CCD camera, 8
Is the transmitter.

In FIG. 3, since the optical path switching mirror 6 is normally located at the position indicated by the solid line, the image of the earth 4 is displayed by the optical system 5 as C.
An image is formed on the photosensitive surface of the CD camera 7. This makes the Earth 4
The surface information such as the topography, vegetation distribution, terrain distribution, resource distribution, etc. on the surface of is converted into an electric signal by the CCD camera 7 and transmitted to the ground station by the transmitter 8.

By the way, since the sensitivity of the CCD camera changes due to temperature change, deterioration, etc., the observation result of the ground surface information becomes uncertain. In order to correct this, the optical path switching mirror 6 is set to the position of the dotted line before and after the observation to stabilize the power supply 2.
Then, the light source 1 is turned on, the output light of the light source 1 is guided to the CCD camera 7, and the output of the CCD camera 7 is measured.
Know the sensitivity of the camera 7 and correct the observation result.

However, the halogen lamp 1 also changes in temperature,
The output light intensity changes due to deterioration or the like. So the photo detector 3
A part of the output light from the halogen lamp 1 is monitored by and is transmitted to the ground station by the transmitter 8, the output intensity of the light source 1 is obtained at the ground station, and the sensitivity correction value of the CCD camera 7 is further improved.

[0006]

In the sensitivity correction method of the CCD camera 7 as described above, the halogen lamp 1 has a wide light emission distribution as shown by the solid line in FIG. 4, and the photodetector 3 is as wide as shown in FIG. Because of the sensitivity wavelength distribution, the output of the photodetector 3 is the convolution of FIG. 4 and FIG. However, if the emission wavelength distribution of the halogen lamp 1 changes as shown by the dotted line in FIG. 4, the output of the photodetector 3 changes even though the light output at the wavelength λ at which the CCD camera 7 has the only sensitivity does not change.
If the ground station believes this and corrects the sensitivity of the CCD camera 7, there is a drawback that unnecessary correction, that is, a correction error occurs.

Further, since the output signal of the photodetector 3 is processed by the ground station, the transmitter 8 has one channel for the photodetector 3.
There was a drawback that required extra lines.

The present invention has been made to solve the above problems, and provides a standard light source that does not cause a correction error and does not require an extra channel in the transmitter 8.

[0009]

In the standard light source according to the present invention, in one example, an interference filter is used from the light output of the halogen lamp 1 to extract light of a specific wavelength λ, which CCD has only sensitivity, A power supply control circuit is used so that the output of the photodetector 3 becomes constant.

In another example, as the light source, a laser diode which has a unique sensitivity to CCD and oscillates with light of wavelength λ is used, and a power supply control circuit is used so that the output of the photodetector 3 becomes constant.

[0011]

In one example, since only the light of the specific wavelength λ is extracted from the output light of the halogen lamp through the interference filter, the CCD camera 7 can be used as the standard light source having only the output of the wavelength λ having the sensitivity and the correction. No error will occur. Further, since the power supply control circuit feeds back the power supply 2 so that the output signal of the photodetector 3 becomes constant, the photodetector 3
It is not necessary to transmit the output signal of 1 to the ground station via the transmitter 8, and the number of channels of the transmitter 8 can be reduced by one line.

In another example, since the CCD camera 7 uses a laser diode that oscillates only at the light wavelength λ, which is the only sensitivity, as a light source, no correction error occurs. Furthermore, the number of channels of the transmitter 8 is the same as in the first example,
One line can be reduced.

[0013]

EXAMPLES Example 1. FIG. 1 is a block diagram showing an embodiment of the present invention. 1-3 are the same as the conventional ones, 9 is an interference filter which passes only the component of wavelength .lamda. Which the CCD camera has sensitivity, and 10 is a power supply control circuit. .. In FIG. 1, since the output light from the halogen lamp 1 is taken out through the interference filter 9 that allows only the component of the wavelength λ, which is the only sensitivity of the CCD camera, the wavelength is changed even if the emission wavelength distribution of the light source 1 changes. Corrects with λ light. Further, since the power supply control circuit 10 controls the power supply 2 so that the output of the photodetector 3 becomes constant, the light intensity from the light source 1 after passing through the interference filter 9 becomes constant, and the output of the photodetector 3 becomes equal to the ground level. There is no need to transmit to the station.

Example 2. FIG. 2 shows another embodiment of the present invention, in which 1 is a wavelength λ at which the CCD camera 7 is only sensitive.
The laser diodes 2, 3 oscillate at 1 are the same as those in the prior art, and 10 is the same as in FIG. In FIG. 2, since the laser diode 1 oscillates only at the wavelength λ at which the CCD camera has the only sensitivity, there is no erroneous correction. The effects of the power supply 2, the photodetector 3, and the power supply control circuit 10 are exactly the same as in the first embodiment.

[0015]

As described above, according to the present invention, the wavelength is selected by the interference filter or the wavelength is selected by the laser diode, so that there is no erroneous correction and the light output of the light source is Since the power supply is controlled so that the output of the photodetector to be monitored is constant, there is an effect that it is not necessary to transmit the output of the photodetector to the ground station.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram showing another embodiment of the present invention.

FIG. 3 is a configuration diagram showing a configuration and a usage example of a conventional standard light source.

FIG. 4 is a diagram showing an emission wavelength distribution of a halogen lamp.

FIG. 5 is a diagram showing a sensitivity wavelength distribution of a photodetector.

[Explanation of symbols]

 1 halogen lamp or laser diode 2 power supply 3 photodetector 9 interference filter 10 power supply control circuit

Claims (2)

[Claims] 1. A standard light source equipped with a halogen lamp as a light source, a power source for turning on the halogen lamp, and a photodetector for monitoring a part of the light generated by the halogen lamp, wherein the light generated by the halogen lamp is used. A standard light source, comprising: an interference filter for extracting light of a specific wavelength; and a power supply control circuit for feeding back to the power supply using an output current obtained by the photodetector. 2. A laser diode as a light source for generating light of a predetermined wavelength, a power supply for turning on the laser diode, a photodetector for monitoring a part of the light generated by the laser diode, and the light. A standard light source comprising a power supply control circuit for feeding back the power supply using an output current obtained by a detector.