JPH07248225A - Sun sensor - Google Patents

Abstract

PURPOSE:To calculate a direction of the sun accurately without requiring a plurality of optical detectors, by dividing a visual field of a sun sensor into two, enlarging a measuring area, and eliminating a maneuver to catch the sun in the early stage of launching of an artificial satellite. CONSTITUTION:Optical lenses 1, 2 are used to widen a visual field, and a prism 3 is used to bring the light from the two optical lenses 1, 2 into a CCD cell 4. A photodetecting surface of the CCD cell is shifted from focal points of the lenses, so that an image is defocused. A direction of the sun is accurately calculated by a centroid and through corrections/calculations with characteristics of an optical system taken into consideration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sun sensor.

[0002]

2. Description of the Related Art A conventional basic sun sensor is composed of a slit plate 15 having a slit S, a one-dimensional CCD cell 16 and an electric section 17 for calculating the sun direction as shown in FIG. Sunlight through S is one-dimensional C
The direction of the sun is calculated from the location of the CD and the distance from the cell to the slit.

Further, Japanese Unexamined Patent Publication No. 62-73109 discloses an N-shaped slit, Japanese Utility Model Laid-Open No. 63-19209 discloses a scanning line system, and Japanese Utility Model Laid-Open No. 60-168700 uses a two-dimensional CCD. Then, the points for detecting the two axes of the attitude of the artificial satellite are shown. Furthermore, the actual Kaisho 61-12
In 3919, the measurement range of the sun sensor is expanded by increasing the number of light receiving devices.

[0004]

In the conventional sun sensor, as can be seen from FIG. 7, there is a limit in the direction of the sun that can be measured depending on the length of the one-dimensional CCD and the distance to the slit. Further, the solar sensor according to this method has a drawback that the linear region in the visual field is narrow. Further, in order to measure two directions (two axes), the set of FIG. 7, that is, two light receiving elements are required. Furthermore, since the measurement range is limited, a sun capture maneuver (rotating around a single axis or two axes) was required when performing initial sun capture with an artificial satellite or the like. JP-A-62-73109, JP-A-63-19
The sun sensors described in Japanese Patent Publication No. 209 and Japanese Utility Model Laid-Open No. 60-168700 compensate for the drawback that the sun sensor of FIG. 7 can measure only one axis, but increase the linear region and widen the measurement region itself. I can't do that. For this reason,
The sun sensor described in Japanese Utility Model Laid-Open No. 61-123919 aims at expanding the measurement range, but it requires a large number of light receiving elements.

The present invention has been made in order to solve the above-mentioned problems, and eliminates the need to perform sun capturing maneuvers at the initial stage of launch of an artificial satellite by making the field of view two and expanding the measurement region. There is. It is also intended to accurately calculate the sun direction without requiring a plurality of optical detectors.

[0006]

The sun sensor according to the present invention uses two optical lenses and an optical member such as a prism for projecting light from the lenses onto a CCD cell. In addition, a combination of defocus and centroid calculations is used to calculate the position of the sun on the CCD cell.

Further, the present invention uses the light from the lens as a CCD.
A single double-sided mirror and a drive that rotates the mirror are used to project onto the cell.

The present invention uses a combination of polarizing lenses, one half mirror, one mirror, and a driving unit for rotating the polarizing lens to project the light from the lens onto the CCD cell.

[0009]

According to the present invention, the field of view can be expanded by using two optical lenses. Further, since the light from the two lenses can be projected onto the two-dimensional CCD cell by using the prism, only one CCD cell is required. Further, the position of the sun on the CCD cell can be accurately obtained by combining the defocus and the centroid calculation. Furthermore, the optical characteristics of the optical lens can be corrected, and the actual sun direction can be calculated accurately.

Further, it is possible to rotate the double-sided mirror by its mirror driving section and select the light from the optical lens which hits the CCD cell.

According to the present invention, the light from the optical lenses 1 and 2 is polarized by passing through the first polarizing lenses 1 and 2.
The light from one optical lens 2 is reflected by a half mirror and applied to a second polarizing lens. The other optical lens 1
The light from is reflected by the half mirror, then reflected by the plane mirror, transmitted through the half mirror, and applied to the second polarizing lens. CCD by rotating the second polarizing lens
The light from the optical lens that hits the cell can be selected.

[0012]

【Example】

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings. Figure 1
FIG. 3 is a diagram showing Embodiment 1 of the present invention. In FIG. 1, 1 is a first optical lens, 2 is a second optical lens, 3
Is a prism that bends the light from the first optical lens 1 and the second optical lens 2 at a right angle, and 4 is a CCD cell that receives the light from the prism 3 as an input, and the optical lens 1 and the optical lens 2 are It is located at the focus position. 5
Is a signal processing unit for calculating the centroid of the defocused signal from the CCD cell 4, and 6 is the correction of the actual sun direction from the sun position on the CCD cell 4 obtained by the signal processing unit 5. This is the logic part that performs calculations. Reference numerals 23 and 24 respectively represent an output signal from the CCD cell 4 and an output signal from the signal processing unit 5.

Next, the operation of the first embodiment of the present invention will be described. First, in FIG. 1, when the sun is in the field of view, the optical lens 1 transmits the light. The optical lens 2 similarly transmits the light when the sun is in the field of view. The prism 3 bends the light from the optical lens 1 and the optical lens 2 at a right angle and irradiates the CCD cell 4 with the light. The CCD cell 4 is slightly defocused from the optical lenses 1 and 2 and outputs a defocused image signal. The signal processing unit 5 performs centroid calculation from the signal of the defocused image to accurately calculate the center position of the sun on the CCD cell 4. The logic unit 6 calculates the actual direction of the sun by performing correction calculation from the position of the sun on the CCD cell 4 output by the signal processing unit 5 in consideration of the characteristics of the optical lens.

The details will be described below. Figure 4 shows a schematic sketch
Shown in. 18 is imitating an enclosure. FIG. 5 is a diagram showing the result of defocusing. When defocusing is performed, the image 19 of the sun, which was a point image and is not defocused, can be greatly expanded like a defocused image 20.
By expanding the image in this way, the influence of specific noise can be made uniform, and the influence of the dead zone on the CCD cell 21 can be eliminated. The received light intensity 22 on the CCD cell when defocusing is performed can be schematically drawn as shown in FIG. The position of the sun can be accurately determined by obtaining the average position on the CCD using the received light intensity as a weight (that is, by performing centroid calculation). That is, if the vertical position on the CCD cell is X and the horizontal position is Y, the received light intensity is Wa (X, Y), and the number of pixels on the CCD cell is m and n, respectively, the vertical position on the CCD of the sun. The position Xs and the lateral position Ys are respectively calculated as follows.

[0015]

[Equation 1]

At this time, if the sun is on the periphery of the CCD cell, the influence of aberration of the optical lens or the like can be corrected when calculating the direction of the sun. For example, the correction value is δ
Then, if the corrected position of the sun is added with ^, it can be corrected as follows. This correction value can be determined by a sensor unit test or the like.

[0017]

[Equation 2]

By this correction calculation, the influence of the projection on the plane at the peripheral portion is corrected, so that the same effect as expanding the linear region can be expected.

Second Embodiment FIG. 2 is a diagram showing a second embodiment of the present invention. In FIG. 2, reference numeral 1 is an optical lens, 2 is a similar optical lens, 7 is a double-sided mirror whose front and back surfaces are mirrors, and 8 is a double-sided mirror 7.
Is a CCD cell that receives light from the double-sided mirror 7 as input, and the optical lens 1 and the optical lens 2 are arranged at a defocused position. Is a signal processing unit for centroid calculation of the defocused signal from the CCD cell 4 and 6 calculates the actual direction of the sun from the sun position on the CCD cell 4 obtained by the signal processing unit 5. This is a logic unit that performs correction calculation. 23 and 24 are C
An output signal from the CD cell 4 and an output signal from the signal processing unit 5.

Next, the operation of the second embodiment of the present invention will be described. First, in FIG. 2, operations 1, 2, 4, 5, and 6 are the same as the description of the operation of the first embodiment. Here, by rotating the double-sided mirror 7 with the drive unit 8, CC
It is selected whether the light input to the D cell 4 is the light from the optical lens 1 or the light from the optical lens 2.

Third Embodiment FIG. 3 is a diagram showing a third embodiment of the present invention. In FIG. 3, 1 is an optical lens, 2 is a similar optical lens, 9 is a first polarizing lens for the light from the optical lens 1, 10 is a second polarizing lens for the light from the optical lens 2, 11
Is a half mirror that both reflects and transmits incident light, 12 is a plane mirror, 13 is a third polarizing lens for selecting either the light reflected from the half mirror 11 or the light transmitted through it, 4 Is a CCD cell that receives light from the third polarizing lens 13 as an input, and is arranged at a defocused position with respect to the optical lens 1 and the optical lens 2. 14 is a command as required, and the third polarizing lens 13
Is a drive unit for rotating. Reference numeral 5 denotes a signal processing unit for centroid calculation of the defocused signal from the CCD cell 4, and 6 calculates and corrects the actual direction of the sun from the sun position on the CCD cell obtained by the signal processing unit 5. This is the logic part that performs calculations. Reference numerals 23 and 24 respectively represent an output signal from the CCD cell 4 and an output signal from the signal processing unit 5.

Next, the operation of the third embodiment of the present invention will be described. First, in FIG. 3, the operations of 1, 2, 4, 5, and 6 are the same as those of the operation of the first embodiment. Here, the light from the optical lens 1 is polarized by the first polarizing lens 9 and reflected by the half mirror 11. In addition, the light from the optical lens 2 is polarized by the second polarizing lens 10, and the half mirror 1
Reflect at 1. Next, the light reflected by the half mirror 11 of the first polarization lens 9 is reflected by the plane mirror 12 and again transmitted through the half mirror 11, and the third polarization lens 13
To enter. At this time, the reflected light of the second polarizing lens 10 is input to the third polarizing lens 13. By rotating the third polarization lens by the drive unit of 14, that is, by changing the polarization plane, the light input to the CCD cell of 4 is made the light from the optical lens 1 or the optical lens 2 Select whether to use light from 2.

[0023]

According to the present invention, the field of view can be expanded by using two optical lenses. Further, since light from two lenses can be projected onto a two-dimensional CCD cell by using an optical member such as a prism, only one CCD cell is required. Also, by combining defocus and centroid calculation, C
The position of the sun on the CD cell can be accurately determined. Furthermore, the optical characteristics of the optical lens can be corrected, and the actual sun direction can be calculated accurately.

Further, according to the present invention, the double-sided mirror can be rotated by its mirror driving unit to select the light from the optical lens which hits the CCD cell, and the same effect as described above can be obtained.

According to the present invention, it is possible to select whether the light input to the CCD cell is the light from the first optical lens or the light from the second optical lens by changing the polarization plane. Get the effect.

[Brief description of drawings]

FIG. 1 is a diagram showing a sun sensor according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a sun sensor according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a sun sensor according to a third embodiment of the present invention.

FIG. 4 is a sketch showing the outline of the present invention.

FIG. 5 is a diagram showing an outline of defocus.

FIG. 6 is an image diagram of a CCD cell and received light intensity for showing an outline of centroid calculation.

FIG. 7 is a diagram showing a conventional sun sensor.

[Explanation of symbols]

 1 1st optical lens 2 2nd optical lens 3 Prism 4 CCD cell 5 Signal processing part (centroid calculation) 6 Logic part (sun direction calculation) 7 Double-sided mirror 8 Double-sided mirror drive part 9 1st polarizing lens 1 10 Second polarized lens 2 11 Half mirror 12 Plane mirror 13 Third polarized lens 14 Third polarized lens driving section 15 Slit 16 One-dimensional CCD cell 17 Electric section (Sun direction calculation) 18 Case 19 Sun image without defocus 20 Defocused sun image 21 CCD cell 22 Received light intensity 23 CCD output signal 24 Output signal from signal processing unit

Claims (4)

[Claims] 1. The first and second optical lenses, and the first and second optical lenses,
An optical member placed on the optical axis of the optical lens for bending the light passing through the second optical lens in a right angle direction, and defocusing the light bent by the optical member to receive the light C
A light receiving surface of the CD cell, a signal processing unit that performs centroid calculation from the output signal of the light receiving surface, and a logic unit that calculates the sun direction from the result of the centroid calculation and correction calculation of aberration and the like. A solar sensor characterized by. 2. The sun sensor according to claim 1, wherein a prism is used as the optical member. 3. The first and second optical lenses, and the first and second optical lenses,
In order to bend the light passing through the second optical lens at a right angle, the mirror placed on the optical axis of the optical lens has a reflecting surface on both sides, and the mirror is moved to move the first cell to the light receiving surface of the CCD cell.
2. The sun sensor according to claim 1, wherein an optical member is configured by a drive unit for making light passing through either the optical lens 1 or the second optical lens of 1. 4. The first and second optical lenses, and the first and second optical lenses,
The first and second polarizing lenses placed on the optical axis of the optical lens to polarize the light passing through the second optical lens and the light passing through the first and second polarizing lenses at right angles to each other. A half mirror for bending the mirror, a mirror for reflecting the reflected light of the half mirror, a third polarizing lens for selectively transmitting the light from the half mirror, and a CCD by rotating the third polarizing lens. The optical member is constituted by a driving unit for causing the light receiving surface of the cell to be irradiated with either light passing through either the first optical lens or the second optical lens. The sun sensor described.