RU2399063C1 - Optical source angular position sensor - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: detector has a computing unit, at least two photodetectors connected to the computing unit and at least two transparent scattering plates illuminated by radiation flux from an optical source and lying in different planes at an angle to each other. Brightness of the surface of the plate far from the optical source depends on the angle of incidence of the radiation flux on the plate. Each plate is placed in front of the corresponding photodetector which is made with possibility of recording brightness of the rear surface of the plate and transmitting the brightness signal to the computing unit which is made with possibility of calculating the angular position of the optical source based on the brightness signals received from the photodetectors.

EFFECT: higher accuracy and wider direction finding sector.

8 cl, 4 dwg

Description

The invention relates to detectors of the angular position (direction finding) of an optical source and can be used in devices for determining the position of sources of contrast radiation (not only the visible range, but also close to it ranges), for example, infrared radiation sources such as infrared remote control.

Known radiation detectors are usually based on a variety of photodetectors, with an artificially limited field of view of each, which rather roughly determine the angular position of the optical source.

US Pat. No. 7,319,228 [1] discloses a passive infrared detector comprising at least three sub-detectors for receiving infrared (IR) radiation from the corresponding at least one of the three viewing subsectors, each viewing subsector being covered by one an optical element that does not capture any other viewing sectors, and the viewing subsectors are located at an angle to each other with an interval between adjacent sectors of not more than 30 degrees.

The main disadvantage of this detector, which is sensitive to the angular position of the IR source, is that it has a low accuracy in determining the angular position, which can only be increased by using a large number of separate IR detectors, which complicates the design of the detector and increases its cost.

Closest to the claimed invention is an IR detector for determining the position of an infrared remote control for a video camera, proposed in Japanese patent No. 1109872 [2], which contains three IR photodetectors (PD) with reflectors for the formation of three narrow sensitivity rays in the azimuthal plane. This detector is selected as a prototype of the claimed invention.

As in other solutions known from the prior art, the disadvantage of the prototype detector is that it operates on the basis of three photodetectors with narrow viewing angles and, therefore, has a very limited angular sector of approximate direction finding and works only in one plane (two-dimensional case).

The problem to which the invention is directed is to create an optical source, which is easy to manufacture, of a detector of angular position (direction finding), which with a minimum number of PDs has good accuracy and a relatively wide direction finding sector.

The technical result is achieved by creating a detector of the angular position (direction finding) of an optical source containing a computing unit, at least two photodetectors connected to the computing unit, and at least two transparent scattering plates illuminated by the radiation flux from the optical source and located in different planes at an angle to each other, while the brightness of the back (farthest from the optical source) surface of the plate depends on the angle of incidence of the radiation flux on the plates , Each plate is placed before the corresponding photodetector arranged to the rear registration plate and the surface brightness of the transmission luminance signal computing unit configured to calculate the angular position of the optical source based on brightness signals obtained from the photodetectors.

In a preferred embodiment of the inventive detector, its design included a base, two photodetectors and two scattering plates forming a prism with a base with a section in the shape of an isosceles triangle with equal angles adjacent to the base, while the computing unit was able to calculate the angular position of the optical source in one plane (for example, azimuthal or elevation) based on the brightness signals of the rear surfaces of the plates received from two photodetectors.

In an alternative design of the inventive detector, it included a base, four photodetectors and four scattering plates forming a tetrahedral pyramid with equal angles adjacent to the base, while the computing unit was able to calculate the angular position of the optical source in two perpendicular planes (for example , azimuthal and elevation) based on the brightness signals of the rear surfaces of the plates obtained from four photodetectors.

For the detector to function, it makes sense that it additionally contains partitions located between the pairs of the photodetector - scattering plate and configured to separate the radiation receiving channels.

For the detector to function, it makes sense that the axis of the detector is located in the middle of its viewing sector normal to the base, while the computing unit should be able to calculate the angular position of the optical source from the axis of the detector based on the direction-finding characteristic.

For the detector to function, it makes sense that the computing unit is capable of calculating the angular position (angle φ) of the optical source based on the direction-finding characteristic in the measurement plane P (φ) = (A1-A2) / (A1 + A2),

where A1 and A2 are the amplitudes of the photodetector signals, and the angle φ is in the measurement plane perpendicular to both scattering plates.

For the detector to function, it makes sense that the computing unit is capable of calculating the azimuthal position (angle φ) and elevation position (angle θ) of the optical source in the form of, respectively, an azimuthal direction-finding characteristic

P (φ) = (S13-S24) / (S13 + S24);

and elevation direction finding characteristic

P (θ) = (S12-S34) / (S12 + S34), where S13 = A1 + A3, S24 = A2 + A4 are the sums of amplitudes of the left and right pairs of signals;

S12 = Al + A2, S34 = A3 + A4 - the sum of the amplitudes of the upper and lower pairs of signals;

A1-A4 - the amplitudes of the signals of the photo detectors.

For the detector to function, it makes sense that the scattering plates are made of frosted glass, made with the possibility of diffuse scattering of transmitted radiation from the direction finding source.

For a better understanding of the proposed invention the following is a detailed description with the corresponding drawings.

Figure 1. Scheme of a "two-dimensional" detector of the angular position (direction finding) of an optical source with two photodetectors and diffusing plates of frosted glass, according to the invention. The angles between the plates and the base of the detector are ± β.

Figure 2. The graph of the direction-finding characteristic P (φ) (dependence of P = DELTA / SIGMA signal on the measured angle - φ), according to the invention.

Figure 3. Graph of direction-finding sensitivity (derivative of direction-finding characteristic, dP / dφ).

Figure 4. Scheme of a "three-dimensional" detector of the angular position (direction finding) of an optical source, the four inclined scattering plates of which form a tetrahedral pyramid (view along the axis of the pyramid), according to the invention.

In the claimed invention, the idea of creating a detector of the angular position (direction finding) of an optical source based on two (for a "two-dimensional" detector) or four (for a "three-dimensional" detector) elements illuminated by the detected optical source, transparent scattering plates (which can be made of frosted glasses) is realized ) located not in one plane, which leads to different brightness of their rear surfaces, if the direction to the optical source does not coincide with the axis of the detector. In this case, photodetectors (PDs) located behind the scattering plates will generate signals whose ratio depends on the angular position of the optical source, and the angle (s) of direction to the optical source can be measured (s) after appropriate processing of the PD signals.

The PD signal processing algorithm in the computing unit is similar to the algorithm used in monopulse radars to determine the angle (see "How The Tracking Radar Points at an Object" - http://ed-thelen.org/ifc_track.html#point) [ 3].

Consider the design and method of operation of the claimed invention on the example of a "two-dimensional" detector (Figure 1). The main elements of the detector are two transparent plates 1 with diffused light transmission (scattering plates). The transparency and scattering properties of the plates should correspond to the radiation wavelength range of the optical source, while the radiation intensity of the source should be much greater than the background illumination in the same range (the background radiation of other wavelengths can be filtered out).

The brightness of the back surface of each diffusing plate 1 depends on the angle of illumination of the plate (angle φ between the normal to the plate and the direction of the incident radiation flux) according to the cosine function, since this function determines the cross section of the radiation flux that falls on the plate.

Photodetector 2, located behind the plate, generates a signal proportional to the brightness of the radiation that emanates from the rear surface of plate 1. (The detector must have a baffle 3 between two photodetectors 2 to prevent cross-illumination of photodetectors 2).

The signals of the photodetectors 2 are described by the following formulas:

A1 ~ cos (β-φ)

A2 ~ cos (β + φ)

Where:

β is the angle between each plate 1 and the base 4 of the detector;

φ is the detected angle (angular position of the optical source) between the axis

detector (normal to base 4) and the direction of the radiation flux.

The angular position of the optical source is calculated in the processing unit 5 based on the signals of the photo detectors 2. To calculate the angle φ, use the direction-finding characteristic, the well-known ratio function P = DELTA / SIGMA

P (φ) = (A1-A2) / (A1 + A2)

Graphs of this function for several values of the angle (3 as a parameter (15 °, 30 °, 45 ° and 60 °) are presented in Figure 2. The correspondence between the calculated value of P and the angle φ to be determined is shown for a fixed value of the angle β ( direction finding characteristic).

Similar calculation methods are used in radars to determine the angular position of objects, in the reading heads of optical disks to hold the laser beam on the track of the disk, as well as in other devices.

The direction-finding characteristic P (φ) uniquely determines the angle φ in the measurement sector (SI) 6, when both scattering plates 1 are illuminated, and the angle can be measured.

Outside this sector 6, only one plate is illuminated (the other plate is in the "shaded" area), and the value of the function P is "1" or "-1".

Sector 6 measurement is defined as:

SI = 2x (90-β)

The accuracy of the angle measurement depends on the direction-finding sensitivity, which is a derivative of the direction-finding characteristic. The greater the sensitivity, the higher the accuracy.

Figure 3 shows a graph of direction-finding sensitivity as a function of angle β.

Thus, as β increases, direction-finding sensitivity also increases (which is a positive factor), but the “measurement sector” decreases (which is a negative factor).

To select the angle β, an additional condition can be imposed, for example, on the minimum signal (A1 or A2), when the radiation flux is parallel to the base 4 of the detector (that is, when the direction to the optical source deviates from the detector axis by 90 °).

If we assume, for example, that the minimum signal should not be less than half of its maximum value when the illumination is directed normal to the plate 1, then the following inequality should be fulfilled:

cos (90-β)> 0.5 or sin β> 0.5

This means that the angle β must be at least 30 °.

With the above set of conditions, it is possible to recommend an angle β of 30 °.

For this value, the measurement sector 6 is 120 °, and the direction-finding sensitivity according to FIG. 3 is 0.01, that is, the value of the direction-finding characteristic changes by 1% when the angle φ is changed by 1 °.

By using the “two-dimensional” detector of the angular position (direction finding) of the optical source described above, only one angle can be measured (an angle in one plane, for example, azimuth).

The "three-dimensional" detector for measuring two angles can be made in the form of a tetrahedral pyramid (Figure 4) with faces formed by scattering plates 1. The "three-dimensional" detector contains four photodetectors located under the faces of the pyramid, with each pair "face and photodetector" separated from other pairs by partitions forming separate radiation receiving channels.

In the case of a “three-dimensional” detector, the PD signals must be paired to obtain both the “bearing direction bearing in azimuth” (left and right pairs of signals) and the “direction finding characteristic in elevation” (upper and lower pairs of signals):

S13 = A1 + A3; S24 = A2 + A4 - left and right pairs of signals,

S12 = A1 + A2; S34 = A3 + A4 - the upper and lower pairs of signals,

P (φ) = (S13-S24) / (S13 + S24) - azimuthal (φ) direction-finding characteristic,

P (θ) = (S12- S34) / (S12 + S34) - elevation (θ) direction-finding characteristic.

Although the above embodiment has been set forth to illustrate the present invention, it is clear to those skilled in the art that various modifications, additions and substitutions are possible without departing from the scope and meaning of the present invention as claimed in the appended claims.

Claims (8)

1. The detector of the angular position (direction finding) of an optical source, comprising a computing unit, at least two photodetectors connected to the computing unit, and at least two transparent scattering plates illuminated by the radiation flux from the optical source and located in different planes under angle to each other, while the brightness of the plate surface farthest from the optical source depends on the angle of incidence of the radiation flux onto the plate, with each plate placed in front of the corresponding photodetector, in made with the possibility of registering the brightness of the back surface of the plate and transmitting the brightness signal to a computing unit configured to calculate the angular position of the optical source based on the brightness signals received from photodetectors. 2. The detector according to claim 1, characterized in that it contains a base on which two photodetectors and two scattering plates are placed, forming with a base a prism with a cross section in the shape of an isosceles triangle with equal angles adjacent to the base, while the computing unit is configured to calculating the angular position of the optical source in one plane based on the luminance signals of the wafer surfaces farthest from the light source obtained from two photodetectors. 3. The detector according to claim 1, characterized in that it further comprises two photodetectors and two scattering plates, forming with the base a tetrahedral pyramid with equal angles adjacent to the base, while the computing unit is configured to calculate the angular position of the optical source in two perpendicular planes based on the brightness signals of the wafer surfaces farthest from the light source obtained from four photodetectors. 4. The detector according to any one of claims 1 and 2, characterized in that the axis of the detector is located in the middle of its viewing sector normal to the base, while the computing unit is configured to calculate the angular position of the optical source from the axis of the detector based on the direction-finding characteristic. 5. The detector according to any one of claims 1, 2 and 3, characterized in that it further comprises partitions located between the pairs of the photodetector - scattering plate and configured to separate the radiation receiving channels. 6. The detector according to any one of claims 1, 2 and 3, characterized in that the scattering plates are made of frosted glass with the possibility of diffuse scattering of transmitted radiation from the direction finding source. 7. The detector according to claim 1, characterized in that the computing unit is configured to calculate the angular position (angle φ) of the optical source based on the direction-finding characteristic in the measurement plane P (φ) = (A1-A2) / (A1 + A2), where A1 and A2 are the amplitudes of the photodetector signals, and the angle φ is in the measurement plane perpendicular to both scattering plates. 8. The detector according to claim 1, characterized in that the computing unit is configured to calculate the azimuthal position (angle φ) and elevation position (angle θ) of the optical source in the form of, respectively, azimuthal direction-finding characteristic
P (φ) = (S13-S24) / (S13 + S24); and elevation direction finding characteristic
P (θ) = (S12-S34) / (S12 + S34),
where S13 = A1 + A3, S24 = A2 + A4 - the sum of the amplitudes of the left and right pairs of signals;
S12 = A1 + A2, S34 = A3 + A4 - the sum of the amplitudes of the upper and lower pairs of signals;
A1-A4 are the amplitudes of the photodetector signals.

Images