JPS61709A - Solar sensor - Google Patents

Abstract

PURPOSE:To enable measurement, in a digital value, of an incident angle of the solar beams, by forcing an aperture mask with an extremely fine slit to approach an one-dimensional linear array sensor and detecting incident positions of the solar beams from an output of the linear array sensor. CONSTITUTION:Respecting a incident beam of light that passed through a slit 151 of an aperture mask 15, a distance between a CCD sensor unit 141 and the aperture mask 15 is assumed to be H and the incident angle of the solar beams theta, a position P of the incident position of the solar beams on a light-receiving surface of the CCD sensor unit 141 is located in a position distant from the center O by l(=H/tantheta). This incident beam is enlarged with the Gaussian distribution with the point P as the center of width of a slit 151 and its diffraction action and this condition of distribution is detected by the CCD sensor 141 and transferred to a signal processing circuit 18 as an output. Thus, by detection of the incident position of the solar beams from the output of the linear array sensor, measurement of the incident angles of the solar beams is available as a digital value.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a solar sensor used for determining the attitude of a non-spin type artificial satellite, and in particular, a solar sensor that is not affected by changes in the orbital altitude of the artificial satellite. This article relates to an improved method for accurately measuring the angle of incidence of sunlight.

[Technical background of the invention and its problems] As shown in FIG. 9, a solar sensor generally used in a non-spin type artificial satellite has a mask 12 in which a circular hole 121 is provided on a solar cell 11. in close contact with sunlight S
is irradiated onto the solar cell 11 through the through hole 121 of the 7 screen 12, and the cell output signal I of the solar cell 11 is outputted via the buffer amplifier 13. In this case, when the orbit altitude of the artificial satellite is h, it is known that the output I of the cell 11 is proportional to the COS θ of the incident angle θ of the sunlight S, and is expressed by the following equation.

1 (h) = K (h) cosθ (however, K(h
): proportionality constant, θ: angle of solar incidence) For this reason, with conventional solar sensors, when the orbital altitude of the satellite changes, the detection output of the angle of incidence of sunlight naturally changes, so it is difficult to detect errors in the angle of incidence of sunlight. Not only is the solar cell's protective film discolored by cosmic radiation, but sensitivity is also reduced due to deterioration of the buffer amplifier, which causes measurement errors.

[Purpose of the invention] This invention was made to improve the above-mentioned problems, and provides a solar sensor that can accurately measure the angle of incidence of sunlight without being affected by changes in the altitude of the orbit of an artificial satellite. The purpose is to provide

[Summary of the Invention] That is, the solar sensor according to the present invention brings an aperture mask having an extremely thin slit close to a one-dimensional linear array sensor, and detects the sunlight incident position from the output of the linear array sensor. The angle of incidence of sunlight is measured as a digital value.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 8.

FIG. 1 shows its basic configuration, and reference numeral 14 in the figure is a one-dimensional linear array sensor. This linear array sensor 14 has, for example, a COD of 2048 elements in its center.
CCD sensor section 14 in which (charge transfer elements) are arranged in - rows
1, and the number υ of this linear array sensor 14 is
An aperture mask 15 is arranged above. This aperture mask 15 has a slit 151 with a width of several tens of willows formed in its center in a direction perpendicular to the CCD arrangement direction of the CCD sensor section 141.
This is for irradiating only the sunlight that has passed through the CCD sensor section 141. This CCO sensor section 141
The OD drive circuit 16 constantly sweeps the light at a constant cycle, and when the light receiving surface is irradiated with sunlight, it performs photoelectric conversion and uses the electrical signal as a detection signal for the sunlight incident position and sequentially passes it through the buffer amplifier 17. The signal is then output to the signal processing circuit 18. This signal processing circuit 18 detects the sunlight incident position from the detection signal K and calculates and outputs the sunlight incident angle. Incidentally, timing drive signals, clock signals, etc. necessary for the COD drive circuit 16 and signal processing circuit 18 are generated by a timing generation circuit 19.

That is, regarding the incident light that has passed through the slit 151 of the aperture mask 15, if the distance between the CCD sensor section 141 and the aperture mask 15 is H1 and the sunlight incident angle is θ, then the sunlight incident position on the light receiving surface of the CCD sensor section 141 is As shown in FIG. 2, P is ffi<=l from the center O
-1/lanθ). Due to the width of the slit 151 and the diffraction effect, this incident light spreads in a Gaussian distribution around point P, and this distribution state is detected by the CCD sensor section 141 and transferred and output to the signal processing circuit 18.

Here, the signal processing circuit 18 will be explained with reference to FIGS. 3 to 8.

FIG. 3 shows a specific configuration of the signal processing circuit 18, and reference numeral 181 in the figure is an automatic gain adjustment circuit (hereinafter referred to as AGC circuit). A detection signal K from the CCD sensor section 141 is supplied to this AGC circuit 181 . In other words, this AGC circuit 181 is stable because the output of the CCD sensor section 141 decreases in proportion to COS θ as the sunlight incident angle θ increases, and the amount of attenuation reaches approximately 1/2 when θ = 60°. In order to perform proper signal processing, the input wave height is normalized in advance. This AGC circuit 181 is specifically configured as shown in FIG.

That is, the reference numeral 201 in the figure indicates an AGC amplifier, and 202a to 202a.
202e is a feedback resistor for gain control, 203 is an analog multiplexer, 204a to 204d are analog comparators for input level detection, 205a to 205d are resistors for setting comparison voltages, 206 is an encoder with a latch for storing the input level, 207 is the comparison voltage source, and this v′
The AGC circuit 181 detects the input level of the detection signal in the first scan, stores it in the encoder 206, selects and determines the gain setting feedback resistors 202a to 202e, and performs measurement from the second scan. It is.

The detection signal normalized by the AGC circuit 181 is compared with the reference voltage ECMP by the analog analog comparator 182 and quantized, resulting in binary values of '1' and 'O'.
The output V182 of this comparator 182 is supplied to the reset side end R of a set/reset flip-flop (hereinafter referred to as S/R FF) 183.This S/R-FF 183 A start signal St (generated by the timing generation circuit 19), which is a drive signal for the CCD sensor section 141, is applied to the set side input terminal S of the CCD sensor section 141. It is generated in response to element driving, and the accumulated charge in the CCD sensor section 141 is
This is for transferring to the transfer register inside D. This accumulated charge is sequentially sent out from the CCD sensor section 141 in response to the clock signal CK.

Then, the output V183 of the S/R-FF 183 is supplied to the AND gate 184 together with the clock signal GK (which is the same as the charge transfer lock and corresponds to one pixel of the COD sensor section 141) generated by the timing generation circuit 19. be done. The output of this AND gate 184 is the OR gate 185
CLK of the first counter 186 via
supplied to The start signal St is supplied to the reset input terminal CLR of the first counter 186, and count data from its output terminals 01 to Q11 is supplied to the data input terminal BK of the shift register 181.

On the other hand, the output V182 of the comparator 182 is supplied to the enable input terminal ENB of the second counter 188. The clock input terminal CLK of this second counter 188 receives the clock signal CK from the timing generation circuit 19.
is supplied, and the start signal signal is supplied to the reset input terminal CLR.

The count data from the output IQI of the second counter 188 is supplied to the clock input terminal CLK of the first counter 186 via the OR gate 185, and is also supplied to the data input mA of the shift register 187. Load input terminal LOD of this shift register 187
A load signal from the timing generation circuit 19 is supplied to the timing generating circuit 19. This load signal is transmitted to the CCD sensor section 141.
When the shift register 187 receives this load signal, it inputs data in response to the external read clock signal RCK supplied to the clock input terminal 0LOK. End A~
The data supplied to K is sequentially shifted and output. The output I of this shift register 187 is the sunlight incident angle θ
It is a digitized version of

That is, from the timing generation circuit 19 to FIG.
), (b) when the lock signal GK and start signal St are output, and if the signal processing circuit 18 is supplied with the detection signal K as shown in FIG. 5(C), the comparator 182 Output digital signal v
182 becomes as shown in FIG. 5(d), and as a result, the output v183 of S/R-F F183 becomes as shown in FIG. 5(e).
As shown in FIG. 2, the value is 1'' during the period A from the Oth element output of the CCD sensor unit 141 to the a@th element output hit by the incident light, and is "O" otherwise.

During this period A, the clock signal K from the timing generation circuit 19 is supplied to the clock input terminal CLK of the first counter 186 via the AND gate 184 and the OR gate 185.
IA! + is counted.

On the other hand, in the output period B of the element of the CCD sensor section 141 that is illuminated by the incident light, the output V18 of the comparator 182
2 becomes '1'', the second counter 188 enters a counting state, and the clock signal GK is counted by this second counter 188.The counted value is counted down to 1/2 and then passed through the OR gate 185. The clock signal is supplied to the clock input terminal of the first counter 186 and is counted by the first counter 186.

Here, the 20th counter 188 is a simple DC
It is a mold flip 70 tube. The total counting results of the first counter 186 and the second counter 188 are shown at 181 in FIG.
After being set by the load signal shown in f), the load signal shown in Fig. 5 (q
) are read out sequentially by the external readout signal RCK shown in FIG.

In other words, the feature of this signal processing circuit is that the second
By using the counter 188, even if the count value in period B is an odd value, the position information can be measured at an angle of 1/2 pixel without truncating one digit after the decimal point. Another point is that by employing the AGC circuit 181, the level of the detection signal applied to the comparator 182 is almost constant without being affected by the sunlight incident angle θ, and as a result, the measurement accuracy is constant over the entire measurement range. There are many things that can happen.

The above is done in order to suppress the influence of the dead zone ΔE of the comparator 182 on the measurement as much as possible with respect to the detection signal K extracted and shown in FIG.
When MP is selected as ECMP1 in the middle of the wave height and when MP is selected as ECMP2 near the base of the wave height, the uncertainty in measurement of pulse width B is Δb2>Δb1, so ECM
, P is much larger. Therefore, AGC
If the circuit 181 is not used, the CCD sensor section 14
Since the wave height in the detection signal 1 changes depending on the sunlight incident angle θ, it is necessary to select the reference voltage ECMP of the comparator 182 to the ECMP2 side in order to cover the entire measurement field of view.

Incidentally, by keeping the wave height substantially constant over the entire measurement field of view through AGC operation and approximately calculating the wave height center P using the interpolation method described below, it is possible to obtain a more accurate sunlight incident angle θ.

Figure 7 is for explaining the principle.
) shows each signal waveform of the detection signal K and the reference voltage level ECMP with the horizontal axis as the X coordinate, and FIG.
i, a), (x2.

b) Enlarged view of the vicinity. In other words, if the slope of the tangent line passing through point A and the mouth is k, then the intersection point P of the two straight lines is the center of wave height
It can be approximated as O. Therefore, from the straight line equation, the coordinates of the intersection P are y-a=k (x-xi) ・-(1
)y −b= −k (x−x2 ) −
(23). From this (+), (2j formula, the X coordinate value xO of the intersection point P is calculated as follows:

FIG. 8 shows the configuration of a signal processing circuit that implements the above correction calculation. However, in FIG. 8, the same parts as in FIG. 3 are denoted by the same reference numerals, and only the different parts will be described here.

That is, the reference numeral 30 in the figure is a correction calculation circuit, and this correction calculation circuit 30 includes first and second sample and hold circuits (
S/H) 301, 302, first and second monostables 303, 304, differential amplifier 305, resistance attenuator 306 consisting of resistors R1 and R2, analog-to-digital conversion (ADC > from circuit 307 and adder 308) It is what it is.

First, the detection signal output from the AGC circuit 181 is processed by first and second sample and hold circuits 301 and 30.
2, and the output of comparator 182 ■182
is supplied to the first and second monostables 303 and 304. The first monostable 303 is the comparator 1
A hold signal is generated in the sample-and-hold circuit 301 for storing the wave height value "a" of the coordinate point A (xi coordinate) by triggering at the leading edge of the output (182) of the output section 82. On the other hand, the second monostable 304 tt is similarly triggered by the trailing edge of the output V182 of the comparator 182, and generates a hold signal for the sample and hold circuit 302 that stores the peak value rr b++ of the coordinate point entrance (x2 coordinate). do. These first and second monostables 303
, 304 at the timing according to each hold signal from AG.
First and second sample and hold circuits 301 and 302 that sample and hold the detection signal K from the C circuit 181
The outputs a and b of
u) Gl culm treatment is changed. After being converted into a digital signal by the ADG circuit 307 in the next stage 2, the signal processing shown in FIG. It is read as .

Therefore, the solar sensor configured as described above is not affected by the intensity of sunlight incident due to fluctuations in the orbital altitude of the signal target, and is not affected by the decrease in cell sensitivity due to the deterioration of the cell protective film due to cosmic rays or by the buffer amplifier. This makes it less susceptible to the effects of gain reduction, etc., and by using two sets of counters, bit truncation of sunlight incident angle data can be prevented. Furthermore, by employing an arithmetic processing method based on the interpolation method, it becomes possible to achieve higher resolution than the inherent element resolution of the sensor, and it becomes possible to obtain a more accurate sunlight incident angle.

[Effects of the Invention] As detailed above, according to the present invention, there is provided a sun sensor that can accurately measure the angle of incidence of sunlight without being affected by changes in the altitude of the orbit of an artificial satellite.

can be provided.

[Brief explanation of the drawing]

Fig. 1 is a block circuit diagram showing an embodiment of the solar sensor according to the present invention, Fig. 2 is a diagram for explaining the basic principle of the above embodiment, and Fig. 3 is a signal processing circuit in the above embodiment. 4 is a block circuit diagram showing a specific configuration of an AGC circuit used in the signal processing circuit, and FIGS. 5 and 6 are block circuit diagrams showing a specific configuration of an AGC circuit used in the signal processing circuit. FIG. 7 and FIG. 8 are diagrams for explaining other embodiments of the present invention, respectively, and FIG. 9 is a diagram showing the configuration of a conventional sun sensor. 14...One-dimensional linear array sensor, 141...C
CD sensor section, 15...Aperture mask, 16...
・CCDff1 dynamic circuit, 17...buffer amplifier, 1
8...Signal processing circuit, 181...AGC times 1.18
2...Analog controller 1<rate, 183...S/R
Flip-flop, 186, 188... counter,
187...Shift register, 19...Timing generation circuit. Applicant's representative Patent attorney Takehiko Suzue 311 Figure 3 Figure 4 Figure 5 (a) ---------JLL-J
LfLk-CKFigure 6Figure 8Figure 9

Claims (4)

[Claims] (1) A one-dimensional sensor that arranges multiple photoelectric conversion elements in one direction and transfers and outputs the charges accumulated in the photoelectric conversion elements, and a slit that is placed close to this one-dimensional sensor and located above the center of the sensor. An aperture mask formed by
It is characterized by comprising a signal processing circuit that detects the position of sunlight passing through the slit and irradiating the light receiving surface of the one-dimensional sensor from the output of the one-dimensional sensor and calculating the sunlight incident angle. solar sensor. (2) The signal processing circuit includes an automatic gain control circuit for waveform normalization, an analog comparator for binarizing the input signal, and a clock signal for driving the one-dimensional sensor according to the output of this comparator. 2. The solar sensor according to claim 1, further comprising: position detection means for detecting the position of incidence on the light receiving surface of the one-dimensional sensor corresponding to the angle of incidence of sunlight by counting the angle of incidence of sunlight. (3) The signal processing circuit includes a wave height value of the n-th element output of the one-dimensional sensor corresponding to the leading edge position coordinate of the output of the analog comparator and a one-dimensional signal corresponding to the trailing edge position coordinate of the output of the analog comparator. A patent claim characterized by comprising a correction means for calculating a correction value using the peak value of the m-th element output of the sensor and adding the correction value to the sunlight incident position information determined by the position detection means. 2. The solar sensor according to item 2. (4) The automatic gain control circuit includes a gain control amplifier having a plurality of feedback resistors, an analog comparator that detects the peak value of the output signal of the amplifier, and a peak value detected by the analog comparator. It is equipped with an encoder memory with a latch for storing data, and a loop gain switching multiplexer that switches and connects the plurality of feedback resistors according to the output of the encoder memory, so as to adjust the output change due to the sunlight incident angle of the one-dimensional sensor output. The solar sensor according to claim 2 or 3, characterized in that the solar sensor is removed.