RU2509290C2 - Method to determine two angular coordinates of glowing reference point and multiple-element photodetector for its realisation - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: result is achieved due to arrangement of elementary photosensitive elements in the space, forming a multi-element photodetector and extraction of information on two angular coordinates of the glowing reference points from their signal values and serial numbers, the value of angular pitch and the angle of inclination of axes of directivity patterns. At the same time the device of the multiple-element photodetector comprises elementary photodetectors arranged with the specified angular pitch relative to a certain axis. The number of elementary photodetectors is at least seven, axes of directivity patterns of elementary photodetectors are arranged at a certain angle different to the straight one and zero one to the axis, relative to which the elementary photodetectors are arranged.

EFFECT: expanded field of view and higher reliability.

3 cl, 7 dwg

Description

The invention relates to instruments for navigating spacecraft, in particular to instruments for determining the angular coordinates of directions to the Sun or other luminous landmark.

A known solar sensor [1], containing a mask with holes, an array photodetector, a signal processing device and an information exchange device.

The principle of operation of the sensor is based on determining the position of the light spot formed by the hole in the opaque mask on the surface of the photodetector, consisting of elementary photodetectors located on a plane in the form of a matrix. Two angular direction coordinates on the Sun are calculated as follows:

$$\alpha =\arctan \frac{X_C}{F}$$

$$\beta =\arctan \frac{Y_{\mathrm{<figure-callout\; id="2"\; label="C\; X\; C"\; filenames="00000009.png,00000010.png"\; state="\{\{state\}\}">C\; </figure-callout>}}}{\sqrt{X_C^{}}}\text{(one)}$$

where X _C and Y _C are the coordinates of the centroid of the light spot on the surface of the matrix photodetector, F is the distance from the mask with the hole to the surface of the matrix photodetector.

Theoretically, the angles α and β can take values in the range from -90 ° to + 90 ° relative to the perpendicular to the surface of the matrix photodetector. However, in practice, since the photosensitive surface of the matrix photodetector has limited dimensions, the mask with the hole has a certain thickness and is located at a certain distance from the matrix photodetector, the range of measurement of angles is smaller. In other words, the field of view of the sensors implementing the indicated measurement method is smaller than the hemisphere and is usually [1], [2] limited to ± (60 ... 64) °.

In addition, taking into account the operating conditions of the sensor, it can be noted that the hole in the screen is a vulnerable point, since the ingress of cosmic dust on the screen can lead to the closing of the hole or a change in its size and, as a result, to disruption of the sensor. It can also be noted that the loss of operability of any elementary photodetectors constituting the matrix will lead to errors in determining the angular coordinates. Thus, the reliability of such a sensor in some cases may be insufficient.

Known panoramic sensor of the angular coordinate of the luminous landmark [2], consisting of a multi-element receiver of optical radiation and a signal processing device. A multi-element optical radiation receiver consists of elementary photodetectors located at a given pitch on a circle.

Solar radiation is incident on a multi-element optical radiation detector, while one part of the elementary photodetectors is illuminated, and the other part is in the shade. The angular coordinate of the Sun is determined by the serial numbers of elementary photodetectors that start and end the group of illuminated photodetectors, or the angular coordinate of a landmark is determined by the ratio of the signal values of any two elementary photodetectors in the group of illuminated ones. The angular coordinate of the Sun is measured in the range of angles from 0 ° to 360 °. However, only one angular coordinate is measured, which is a disadvantage of this sensor.

The aim of the invention is to expand the field of view of a device that implements the measurement of two angular coordinates of a luminous landmark, increasing its reliability.

This goal is achieved by the fact that to determine the angular coordinates, a photodetector consisting of elementary photodetectors is used. Elementary photodetectors are arranged with a given angular pitch relative to some axis so that relative to the plane perpendicular to this axis, the axes of their radiation patterns are directed at a certain angle different from the straight and zero (hereinafter, it is assumed that the axis of the radiation pattern coincides with the direction to a radiation source at which the signal of the photosensitive element has a maximum value).

The above conditions are satisfied, for example, by a photodetector in the form of a truncated cone or a truncated conical polyhedron. The photosensitive surfaces of elementary photodetectors form a conical surface or the surface of a conical polyhedron.

The device of the photodetector is illustrated in Fig.1. The positions denote: 1 - the axis relative to which elementary photodetectors are located; 2 - a plane orthogonal to the axis relative to which elementary photodetectors are located; 3 - axis, relative to which the azimuth and serial numbers of elementary photodetectors are counted; 4 - n-th elementary photodetector; 5 - (n ± 1) -th elementary photodetector; 6 - the angular step of the location of elementary photodetectors; 7 - axis of the radiation pattern of the (n ± k) -th elementary photodetector; 8 - the angle of inclination of the axis of the radiation pattern to a plane orthogonal to the axis relative to which elementary photodetectors are located; 9 - direction to a luminous landmark; 10 - azimuth of direction to a luminous landmark; 11 - the angle of the direction to the luminous landmark.

A plane orthogonal to the axis relative to which elementary photodetectors are located is introduced for clarity. Obviously, the elevation angle and the angle of inclination of the axes of the radiation patterns can be measured directly relative to the axis around which elementary photodetectors are located, this essentially does not change anything.

Figure 2. a receiver is presented in which the photosensitive surfaces of elementary photodetectors form the surface of a conical or conical polyhedral opening. The positions indicated: 1 - n-th elementary photodetector; 2 - (n ± 1) -th elementary photodetector.

When the multi-element photodetector is irradiated with the Sun, a group of illuminated elementary photodetectors can be distinguished. The number of elementary photodetectors in the illuminated group depends on the relative position of the photodetector and the Sun. The signal value of the nth elementary photodetector - I {n) in the group of illuminated is determined as follows:

I (n) = AF (n), F (n)> 0

I (n) = 0, F (n) ≤0 (2)

F (n) = [cos (Ω) cos (Θ) cos (ω) cos (nϑ) + cos (Ω) sin (Θ) cos (ω) sin (ϑ) + sin (Ω) sin (ω)]

where A is the maximum possible value of the signal (occurs when the axis of the radiation pattern of the elementary photodetector coincides with the direction to the Sun), Θ is the azimuth of the direction to the Sun, Ω is the angle of the direction to the Sun, ω is the angle of inclination of the axis of the radiation pattern of the elementary photodetector relative to the plane perpendicular to the axis relative to which elementary photodetectors are located, angle nϑ is the angular coordinate of the nth elementary photodetector in a plane perpendicular to the axis relative to arranged elementary photodetectors, n - sequence number of the elementary photodetector, θ - angular pitch arrangement of elementary photodetectors.

From the expression (2) it follows:

$$\Omega =\arctan \left[\frac{I(n+k)\cos (\Theta -n\vartheta )-I(n)\cos (\Theta -(n+k)\vartheta )}{tg(\omega )(I(n)-I(n+k))}\right]\text{ (4)}$$

где I(n) - величина сигнала n-го элементарного фотоприемника в группе освещенных, I(n+k) - величина сигнала (n+k)-го элементарного фотоприемника в группе освещенных, I(n+l) - величина сигнала (n+l)-го элементарного фотоприемника в группе освещенных. $$\Theta =\arctan \left[\frac{\frac{I(n)-I(n+k)}{I(n)-I(n+l)}\left[\cos (n\vartheta )-\cos ((n+l)\vartheta )\right]-\left[\cos (n\vartheta )-\cos ((n+k)\vartheta )\right]}{\left[\sin (n\vartheta )-\sin ((n+k)\vartheta )\right]-\frac{I(n)-I(n+k)}{I(n)-I(n+l)}\left[\sin (n\vartheta )-\sin ((n+l)\vartheta )\right]}\right]\text{(3)}$$

$$\Omega =\arctan \left[\frac{I(n+k)\cos (\Theta -n\vartheta )-I(n)\cos (\Theta -(n+k)\vartheta )}{tg(\omega )(I(n)-I(n+k))}\right]\text{(four)}$$

where I (n) is the signal magnitude of the nth elementary photodetector in the illuminated group, I (n + k) is the signal magnitude of the (n + k) elementary photodetector in the illuminated group, I (n + l) is the signal magnitude (n + l) -th elementary photodetector in the group of illuminated.

Expressions (3) and (4) allow us to conclude that to determine the angular coordinates of the direction to the Sun, it is enough to have only 3 elementary photodetectors in the group of illuminated ones. For a hemispherical field of view, this condition is satisfied for any directions on the Sun, if the photodetector contains at least 7 elementary photodetectors. However, of interest is a photodetector containing a larger number of elementary photodetectors, for example 1000, since in this case redundancy can be used:

- to increase the accuracy of coordinate measurements by averaging the results;

- to increase the reliability and survivability of the photodetector, since individual or group failures of elementary photodetectors will not be able to interfere with the calculation of the angular coordinates.

In this case, the azimuth Θ directions to the Sun can be determined by finding the centroid, which also simplifies the computational procedure:

$$\Theta =\vartheta \frac{{\displaystyle \sum _{k\mathrm{one}}^{k2}nI(n)}}{{\displaystyle \sum _{k\mathrm{one}}^{k2}I(n)}}\text{(5)}$$

The elevation angle Ω of the direction to the Sun is calculated as follows:

$$\Omega =\arctan \left[\frac{\left[\cos (\Theta -n\vartheta )-\cos (\Theta -(n+l)\vartheta )\right]{\displaystyle \sum _{k\mathrm{one}}^{k2}I(n)}}{(k2-k\mathrm{one}+\mathrm{one})\tan (\omega )(I(n)-I(n+l))}-\frac{{\displaystyle \sum _{k\mathrm{one}}^{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="00000009.png,00000010.png"\; state="\{\{state\}\}">k</figure-callout>}2}\cos (\Theta -n\vartheta )}}{(k2-k\mathrm{one}+\mathrm{one})\tan (\omega )}\right]\text{(6)}$$

where ϑ is the angular step of the arrangement of photosensitive elements; I (n) and I (n + l) are the values of the signals of the nth and (n + l) th illuminated photosensitive elements, respectively, n and (n + l) are selected in the interval from k1 to k2; k1 is the serial number of the first, and k2 is the serial number of the last photosensitive element in the illuminated group, whose signals exceed a predetermined threshold.

In order to facilitate adaptation of the multi-element photodetector device to existing technologies, expression (2) can be represented as follows:

I (n) = I ₁ (n) + I ₂ (n),

I ₁ (n) = B [cos (Ω) cos (Θ) cos (nϑ) + cos (Ω) sin (Θ) sin (nϑ)],

$$I_2(n)=C\sin (\Omega ),\text{(7)}$$

B = Acos (ω), C = Asin (ω)

Expression (7) means that the elementary photodetector consists conditionally of two parts. One part generates a signal I ₂ (n) and is its projection (projection of a photosensitive surface), for example, onto the base of the cylinder, while the other part generates a signal I ₁ (n) and is a projection on a cylindrical surface. C and B are the maximum possible values of the signal values of these parts, respectively.

Figure 3 shows a cross section of the nth elementary photodetector. The positions indicated: 1 - sensitive surface of the nth elementary photodetector; 2 - axis of the radiation pattern of the nth elementary photodetector (perpendicular to the sensitive surface); 3 - the angle of inclination of the axis of the pattern of the nth elementary photodetector relative to a plane perpendicular to the axis relative to which the elementary photodetectors are located; 4 - axis relative to which elementary photodetectors are located; 5 - sensitive surface of the first part of the nth elementary photodetector (projection onto the base of the cylinder); 6 - the axis of the radiation pattern of the first part of the elementary photodetector, parallel to the axis, relative to which the elementary photodetectors are located; 7 - sensitive surface of the second part of the nth elementary photodetector (projection onto a cylindrical surface); 8 - axis of the radiation pattern of the second part of the elementary photodetector, perpendicular to the axis relative to which the elementary photodetectors are located.

Projections can also be viewed on the basis of a polyhedron and a polyhedral surface, respectively.

From the expression (7) and Figure 3 it follows that the radiation pattern of each elementary photodetector is a superposition of the radiation patterns of the first and second parts, and the angle of inclination of the axis of the radiation pattern is determined by the ratio of the maximum values of the signals of these parts.

A practical implementation of a photodetector based on such a division is shown in FIG. 4. The positions denote: 1 - the first sensitive surface of the nth elementary photodetector (projection onto the base of the cylinder); 2 - the second sensitive surface of the nth elementary photodetector (projection onto a cylindrical surface).

Another option is the design of the photodetector in accordance with Figure 5. The positions denote: 1 - the first sensitive surface of the nth elementary photodetector (projection onto the base of the cylinder); 2 - the second sensitive surface of the nth elementary photodetector (projection onto a cylindrical surface); 3 and 4 - hoods that limit the field of view of the cylindrical and flat parts, respectively, and allow you to get the radiation pattern of a composite elementary photodetector, similar to the radiation pattern of an elementary photodetector in figure 1.

The use of optical elements that change the direction of the light rays (prisms or mirrors) allows you to place both parts of an elementary photodetector on one surface, in particular on a plane. The cross section of such an elementary photodetector is shown in Fig.6. The positions indicated: 1 - n-th elementary photodetector; 2 - the first sensitive surface of the nth elementary photodetector, the axis of the radiation pattern of which is parallel to the axis relative to which elementary photodetectors are located; 3 - the second sensitive surface of the nth elementary photodetector, the axis of the radiation pattern of which is perpendicular to the axis relative to which elementary photodetectors are located; 4 - axis of the radiation pattern of the first sensitive surface; 5 - axis of the radiation pattern of the second sensitive surface; 6 - axis relative to which elementary photodetectors are located; 7 - a prism; 8 - opaque coating.

The approach based on the decomposition of the photosensitive surface of an elementary photodetector into orthogonal projections and the superposition of their radiation patterns is also applicable to the case when the axes of the radiation patterns of two parts of an elementary photodetector are directed at different angles other than straight and zero to the axis relative to which elementary photodetectors are located . 7. The section of this element is shown. The positions indicated: 1 - n-th elementary photodetector; 2 - the first sensitive surface of the nth elementary photodetector; 3 - the second sensitive surface of the nth elementary photodetector; 4 - axis of the radiation pattern of the first sensitive surface; 5 - axis of the radiation pattern of the second sensitive surface; 6 - axis, relative to which elementary photodetectors are located.

The first part can be represented as two orthogonal projections. Similarly, the second part is also represented in the form of two orthogonal projections. Four parts are obtained, two of which have parallel beam axes, and the other two have beam axes perpendicular to the axis relative to which elementary photodetectors are located. Two parts that have axes of radiation patterns parallel to the axis relative to which elementary photodetectors are located can be considered as one part whose signal is equal to the sum of the signals of its constituent parts. Two parts that have the axis of the radiation patterns perpendicular to the axis relative to which the elementary photodetectors are located can similarly be replaced by one. The resulting new two parts are orthogonal projections of some elementary photodetector, for which, as already noted in the explanation to Figure 3, the angle of inclination of the axis of the resulting radiation pattern is determined by the ratio of the maximum values of the signals of its orthogonal projections.

Therefore, the proposed method for determining the two angular coordinates of a luminous landmark can be implemented using a photodetector containing elementary photodetectors, the axis of the radiation patterns of which are inclined at a certain angle other than straight and zero to the axis relative to which they are located, and containing elementary photodetectors , each of which consists of two parts, and the axes of the radiation patterns of these parts are tilted at a certain angle to the axis relative to which ementarnye photodetectors.

From the above formulas and the device of the multi-element photodetector in figure 1 it follows that the angular coordinate - Θ can be calculated in the range from 0 ° to 360 °, and the angular coordinate - Ω can be calculated in the range from + 90 ° to - (90 ° - ω). Thus, the proposed photodetector, in contrast to the prototype [1], allows you to determine two angular coordinates of the Sun located at any point in the sphere relative to its center, except for the spherical segment cut off by a cone with an angle at the apex — ω, whose axis coincides with the axis relative to which elementary photodetectors.

It should also be noted that in the inventive multi-element photodetector, elementary photodetectors directly perceive solar radiation, so there are no masks that form and direct the light flux. As a result, the mass and dimensions of the device are reduced, and reliability is increased. In addition, due to the elimination of the need to set a certain spatial position of the mask and photodetectors, the manufacturability of the angular coordinate sensors is improved and the stability of their metrological characteristics is increased.

The device of the inventive photodetector allows to produce it in the form of an integrated circuit. As elementary photodetectors, you can use photodiodes, which are formed using the technology of APS (Active Pixel Sensor), laser micro-milling and etching. In this case, for example, in the case of FIG. 5, the first sensitive surface corresponds to a crystal surface parallel to the pn junction, and the second sensitive surface corresponds to a surface perpendicular to the pn junction of the photodiode.

In addition, since elementary photodetectors, for example, in accordance with FIG. 4 and FIG. 5, occupy the peripheral part of the crystal, its inner part can be used to accommodate an analog-to-digital converter, a computing device, a control device, and an information exchange device. Thus, it turns out not just a photodetector, but a complete sensor of angular coordinates. The electrical connection of such a sensor is carried out through one or more holes obtained with a laser on the inside of the crystal.

Information sources

1. US patent for the invention No. 7552026, IPC G06F 3/00, 2009.

2. The Officine Galileo Digital Sun Sensor, F. Boldrini, E. Monini, IAA-B3-1308P, 3rd IAA Symposium on Small Sattelite for Earth Observation, Berlin, 2001.

3. Patent for the invention of the Russian Federation No. 23237952, IPC G01B 11/26, 2006.

Claims (4)

1. The method of determining the two angular coordinates of a luminous landmark using a multi-element photodetector, which consists in the fact that the elementary photodetectors are located in the radiation flux of the luminous landmark with a given angular pitch relative to some axis, while the axes of the radiation patterns of elementary photodetectors are tilted at an angle to the axis, relative to which elementary photodetectors are located, the values of the signals of elementary photodetectors due to luminous radiation are determined Osya guide, from the values of the signals, the sequence number value of the angular pitch location and magnitude of the inclination angle of the axes of the elementary photodetectors directivity patterns are calculated corner coordinates of the luminous guide. 2. The use for determining the two angular coordinates of the luminous landmark of a multi-element photodetector, which consists of at least seven elementary photodetectors located at a given angular pitch relative to a certain axis, the angle of which to which the axes of the radiation patterns of elementary photodetectors are different from direct and zero. 3. A multi-element photodetector consisting of elementary photodetectors located with a given angular pitch relative to a certain axis, characterized in that the number of elementary photodetectors is not less than seven, the axes of the radiation patterns of elementary photodetectors are located at a certain angle other than straight and zero, relative to the axis, with respect to which elementary photodetectors are located. 4. A multi-element photodetector consisting of elementary photodetectors located with a given angular pitch relative to a certain axis, characterized in that the number of elementary photodetectors is at least seven, each elementary photodetector consists of two parts, the axis of the radiation patterns of these parts are located at certain angles to the axis, regarding which elementary photodetectors are located.

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