RU2422864C1 - Optical scanning system - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: optical scanning system comprises two identical channels, each having a semiconductor laser and a collimating component, and an optical scanner which is common for both channels, a system for outputting radiation of the two channels onto a single optical axis and a zoom lens. The optical scanner is in form of a disc which can rotate and has on its edges a working surface which is perpendicular to the axis of the disc, a closed circular region in form of dihedral elements lying on a circle at equal angular distances in form of steps whose radial dimensions are limited by inner and outer diameters of the circular region. ^ EFFECT: high energy margin, noise immunity and high speed of operation of the system, high accuracy of determining coordinates of an object, possibility of applying different functional laws of scanning, including the linear law. ^ 6 dwg

Description

The invention relates to the field of optical instrumentation, and in particular to optical systems that form an information field with a beam of optical rays. In such devices, optical radiation from a source, mainly a continuous solid-state laser, is generated by the optical system and modulated in a certain way, creating an optical information field within which each point corresponds to a certain value of an informative parameter, for example, the modulation frequency, with which the position is determined, i.e. . coordinates of the object, relative to the optical axis of the system.

Devices using an optical information field not only for detecting and determining the position, speed of movement and acceleration of an object, but also for teleorienting controlled objects have found widespread use in modern technology. The device generates electrical signals proportional to the measured coordinates of the object, and sends them to the actuator, bringing the controlled object to the optical axis of the system.

A known optical system [1], which includes a searchlight that collimates the laser radiation, a modulator and an optical sight located coaxially with it, orienting it in the desired direction. Formed by the searchlight and the modulated stream of optical radiation simultaneously irradiates the entire optical information field (circle with a diameter of 6-8 m), within which the coordinates of the controlled object are determined, and it is held on the optical axis of the system. The disadvantages of this system are the low energy supply and noise immunity at long distances, as well as the large size and the need for liquid cooling of a powerful solid-state laser.

Known optical system [2], containing a searchlight and a sight mounted coaxially with each other. The searchlight contains two identical channels, each of which serves to determine the coordinate along one of the coordinate axes. The channel includes a semiconductor laser mounted near the common front focal plane of the cylindrical lens and lens, forming a narrow beam of laser beams with a ratio of length to width of 20 or more. The beam length corresponds to the size of the optical information field.

Such bundles are called knife, fan, etc. Their formation is facilitated by the ratio of the sizes of the emitting regions (pn junctions) of the lasers, which constitute 200 (100) × 1 μm in modern semiconductor laser structures.

Devices that form an optical information field due to scanning by two narrow beams of rays along the field of view in two mutually perpendicular directions, as in the system [2], have been widely used in recent years due to the appearance of continuous semiconductor lasers comparable in power to solid-state lasers and having higher efficiency.

The role of the deflecting (scanning) elements in the system [2] is performed by two cylindrical lenses mounted on a common frame mounted on the crankshaft in the housing, which, in turn, are mounted in ball bearings, which allows the frame with cylindrical lenses to be able to move plane-parallel in a circle. Since the generators of cylindrical lenses are parallel to the pn radiating transitions of each channel and are perpendicular to each other, knife beam beams are scanned along the field of view of the spotlight: horizontal moves vertically and serves to generate signals that determine the coordinates along the OY axis, the vertical beam moves horizontally and serves to form signals that determine the coordinates along the OX axis. Scanning by beams of rays along the coordinate axes occurs with a mutual time shift of a quarter of the period relative to the axis of sight according to a sinusoidal law.

Thanks to scanning, the energy reserve and noise immunity in the system [2] are significantly higher compared to [1]. However, its disadvantages are not only the complex and inertial optical-mechanical design of the scanning unit, limiting the scanning frequency, but also a small range due to the fixed angular divergence of the radiation, which increases the size of the optical information field and, accordingly, decreases its power density with distance from the control point.

Closest to the claimed invention is an optical scanning system for semiconductor lasers [3], including two identical channels, each of which contains a semiconductor laser, a component that collimates the radiation of a semiconductor laser, and an optical scanner common to both channels, a system for outputting radiation of two channels into a single optical axis and pan-optical lens. In this case, the mutual arrangement of semiconductor lasers is such that their emitting regions (pn junctions) are perpendicular both to each other and to the axes of the measured coordinates.

The output system of the radiation of two channels on a single optical axis is made in the form of a polarizing prism-cube, the scanner is made in the form of a rotating prism, the axis of rotation of which coincides with the axis of the pancratic lens. This ensures, in comparison with [2], the reliability of the system and a higher scanner speed (frame rate). However, the rotation frequency in the system [3] has limitations due to the complexity of the design of the mechanism that transmits rotation from the motor shaft to the frame of the scanning prism, which significantly reduces the dynamic characteristics of the system and requires the use of more powerful electric motors.

A polarizing prism-cube, consisting of two identical AR-90 ° prisms glued together by hypotenuse faces, on one of which a polarizing coating is applied, allows simultaneously outputting linearly polarized radiation from both semiconductor lasers emitting regions and planes onto the optical axis of the pan-optical lens whose polarizations are respectively orthogonal to each other.

The use of a pancratic lens allows one to reduce the angular divergence of radiation in proportion to the range and thereby maintain a fixed optical control field size at all ranges. Due to this, a gain in energy is obtained in comparison with [2] and an increase in the control range.

The simplicity of scanning with a rotating prism in the system [3] is at the same time a drawback, because the projections of the rays into the picture plane form a cross, which performs plane-parallel circular motion. The center of the cross describes a circle with a radius equal to half the size of the optical information field, and the length of each scanning beam should accordingly be twice the size of the field. This means a loss of half the laser radiation power, i.e. reduces the energy supply and noise immunity of the system.

In addition, the scanning scheme in [3] imposes significant restrictions on the possible methods for determining the coordinates of the control object.

The time dependence of the deviation of the position of the beam of rays h (t) from the optical axis along the coordinates OX and OY in systems [2] and [3] is sinusoidal and is determined by the expressions:

where h _x (t) and h _y (t) are the deviations of the position of the beam of rays from the optical axis in two coordinates,

H is the size of the optical control field,

T - period of rotation of the scanner (time of formation of the frame).

The accuracy of determining coordinates when coding by two pulses is determined by two factors:

- the maximum possible time interval between pulses in the two;

- the possibility of the maximum number of packages of twos during the scanning period.

It can be seen from the above formulas that the accuracy of determining coordinates when coding by pulses of pulses would be significantly higher in the case of a linear dependence h (t).

The objective of the proposed technical solution is to increase, compared with the prototype, the energy supply, noise immunity and system speed, increase the accuracy of determining coordinates, and also the possibility of applying various functional laws of scanning, including linear.

The problem is solved in that an optical scanning system is proposed that includes two identical channels, each of which contains a semiconductor laser and a collimating component, and an optical scanner common to both channels, a system for outputting radiation from two channels to a single optical axis and a pan-optical lens, while the arrangement of the two channels is such that the pn-emitting semiconductor laser transitions are perpendicular to each other.

The system differs from the prototype in that the optical scanner is located behind the collimating components of both channels along the rays and is made in the form of a disk mounted for rotation and containing a closed annular region along the edge of the working surface perpendicular to the axis of the disk through equal angular gaps of dihedral elements in the form of steps, the radial dimensions of which are limited by the inner and outer diameters of the annular region, the protruding edge of each dihedral the element lies in one plane perpendicular to the axis of the disk with the corresponding edges of other dihedral elements and makes an angle π / 4 with a radius drawn from the axis of the disk to the point of contact of the edge with the outer diameter of the annular region. In this case, one of the corresponding faces of each dihedral element of the optical scanner is made mirror-reflecting and tilted relative to the plane of the disk at its angle β, discretely changing from one dihedral element to another according to a given functional law depending on the central angle of the disk α, at values of the angle α from 0 up to π, the angle β increases from the minimum value (β ₀ -γ) to the maximum (β ₀ + γ), for values of the angle α from π to 2π, the angle β decreases from the maximum value (β ₀ + γ) to the minimum (β _0- γ ),

where β ₀ is the average value of the angle of inclination to the plane of the disk for two diametrically located mirror-reflecting faces,

γ is the maximum change in the angle β of the slope of the mirror reflecting face from the average value of β ₀ .

In this case, both channels with collimating components are located relative to the optical scanner in such a way that the optical axes of each of them make an angle δ = (π / 2-2β ₀ ) with the disk plane along the path of the optical scanner and intersect with the mirror-reflecting faces of dihedral elements in points spaced one from the other by the central angle of the disk α equal to π / 2. The output system of the radiation of two channels on a single optical axis, made in the form of a prism-rhombus BS-0 ° and prism AR-90 °, glued together by hypotenuse faces, on one of which a polarization coating is applied, is located behind the optical scanner along the rays in this way that the input faces of both prisms are parallel to the plane of the disk of the optical scanner, and are optically connected with it and with the collimating components of both channels by means of mirror-reflecting faces of its dihedral elements so that the optical axis of one channel crosses It is connected with the input face of the BS-0 ° diamond prism, and the optical axis of the other channel with the input face of the AP-90 ° prism, on the edge with a polarization coating, the optical axes of both channels intersect at one point, and they coincide behind the prisms along the rays as between each other, and with the axis of the pancratic lens, located along the rays behind the output system of the radiation of two channels on a single optical axis.

The proposed technical solution allows you to:

- significantly increase the energy supply and noise immunity of the system compared to the prototype due to the fact that the design of the optical scanner provides reciprocating motion of each of the two scanning beams of rays along direct mutually orthogonal trajectories from one to the other edge of the optical information field, the area of which is determined in the proposed system the product of the lengths of the scanning beam of rays, while in the prototype the length of each knife beam is twice the size of the field;

- increase the system speed and accuracy of determining the coordinates of the object due to the simplicity, reliability and low inertia of the optical scanner design, which eliminates the need for reducers, which eliminates a number of mechanical errors, as well as through the use of a given functional scanning law, including linear.

Thus, the claimed optical scanning system allows you to completely solve the problem.

Figure 1 presents a structural diagram of an optical scanning system, front view.

Figure 2 presents a structural diagram of an optical scanning system, top view.

Figure 3 presents a possible embodiment of the dihedral elements of the optical scanner, type A.

Figure 4 shows the dependence of the angle β of the slope of the mirror reflecting faces to the plane of the disk from the central angle of the disk α.

Figure 5 shows the scanning scheme of narrow beams of rays in the picture plane of the optical information field.

Figure 6 shows the principle of determining the coordinates of an object with a linear law of scanning.

The optical scanning system (FIGS. 1, 2) includes two identical channels 1, each of which contains a semiconductor laser and a collimating component, and an optical scanner 2 common to both channels, a radiation output system 3, 4 on a single optical axis, and a pan-optical lens 5. The mutual arrangement of the channels 1 is such that the emitting pn junctions 6 of the semiconductor lasers are perpendicular to each other.

The optical scanner 2 is located behind the collimating components of both channels 1 along the rays and is made in the form of a disk mounted for rotation and containing on the edge of the working surface perpendicular to the axis 7 of the disk, a closed annular region 8 (figure 2). The annular region 8 is made in the form of steps arranged along a circle at equal angular intervals of the dihedral elements 9 (Figs. 2, 3) in the form of steps whose radial dimensions are limited by the inner and outer diameters of the annular region 8. The protruding rib between the faces of each dihedral element 9 lies in one plane perpendicular to the axis 7 of the disk, with the corresponding edges of other dihedral elements and makes an angle π / 4 with a radius drawn from the axis 7 of the disk to the point of contact of the ribs with the outer diameter of the annular region 8 (figure 2).

One of the corresponding faces of each dihedral element 9 is made mirror-reflecting and tilted relative to the plane of the disk at its angle β, discretely changing from one dihedral element to another according to a given functional law depending on the central angle of the disk α, with the values of angle α from 0 to π, the angle β increases from the minimum value (β ₀ -γ) to the maximum (β ₀ + γ), for values of the angle α from π to 2π, the angle β decreases from the maximum value (β ₀ + γ) to the minimum (β ₀ -γ),

where β ₀ is the average value of the angle of inclination to the plane of the disk for two diametrically located mirror-reflecting faces (figure 3),

γ is the maximum change in the angle β of the slope of the mirror reflecting face from the average value of β ₀ .

In particular, with a linear scanning law for which the condition is fulfilled: Δγ = 4γ / n = const (Δγ is the difference of angles β for adjacent dihedral elements 9, n is the total number of dihedral elements on the scanner), the dependence of the angle β of the slope of the mirror reflecting face of the dihedral element 9 to the plane of the disk from the Central angle of the disk α is shown in figure 4 and is determined by the expressions:

Both channels 1 with collimating components are located relative to the optical scanner 2 in such a way that the optical axes of each of them make an angle δ = (π / 2-2β ₀ ) with the plane of the disk along the path of the rays (Figs. 1, 3) and intersect with mirror-reflecting faces of dihedral elements 9 at points 10 spaced one from the other by the central disk angle α equal to π / 2.

The output system of the radiation of two channels on a single optical axis, made in the form of a prism-rhombus BS-0 ° 3 and prism AP-90 ° 4 glued together by hypotenuse faces, on one of which a polarizing coating 11 is applied, is located behind the optical scanner 2 the path of the rays (Fig.1, 2) in such a way that the input faces of both prisms are parallel to the plane of the disk of the optical scanner, and are optically connected with it and with the collimating components of both channels 1 by means of mirror-reflecting faces of dihedral elements 9 in such a way that behind the optical by the caner 2 along the rays the optical axis of one channel intersects with the input face of the prism-rhombus BS-0 ° 3, and the optical axis of the other channel intersects with the input face of the prism AR-90 ° 4, on the face with a polarizing coating 11 the optical axes of both channels intersect one point, and behind the prisms along the rays they coincide both with each other and with the axis 12 of the pancratic lens 5 located along the rays behind the system 3, 4 output radiation of two channels on a single optical axis.

The dihedral elements 9 of the optical scanner 2, in the General case, can be made in such a way that the protruding edge in each of them can be an angle π / 4 with a radius drawn from the disk axis 7 to the point of contact with the outer diameter of the annular region 8 , and any angle ε, where ε lies in the interval from 0 to π / 2. However, this will inevitably lead to a constructive complication of the system 3, 4 of outputting the radiation of two channels to a single optical axis, namely, the need to introduce an additional optical prism into it, for example, another BS-0 ° diamond prism.

Figure 5 shows the projections of the scanning knife beams of the rays 13 and 14 of both channels 1 for various values of the central angle of the disk α from 0 to 2π in the picture plane of the optical information field 15, as well as the position of the control object 16 therein.

The system operates as follows.

Linearly polarized radiation from semiconductor lasers (Figs. 1-3), emitting pn junctions 6 of which are in the form of a luminous line 200 (100) × 1 μm, in each of the two channels 1 passes through a collimating component and in the form of two collimated narrow beams with a cross section close to a circular one, falls at an angle δ = (π / 2-2β ₀ ) onto the annular region 8 of the optical scanner 2, intersecting with the reflecting faces of the dihedral elements 9 at two points 10 spaced apart from each other by the central angle of the disk α equal to π / 2. Since the inclination angles β of the reflecting faces of each dihedral element 9 are discretely changed from one element to another according to a given functional law within the limits indicated in expressions (3), (4), then during the rotation of the optical scanner 2 both laser beams are reflected sequentially from the mirror faces of each dihedral element 9, for one revolution of the disk deviate symmetrically from the optical axis by angles ± 2γ in two orthogonal directions with a phase difference π / 2.

Further, the orthogonally polarized radiation beams of both semiconductor lasers fall into the radiation output system 3, 4 on a single optical axis, namely: the radiation of one channel passes through the BS-0 ° 3 diamond prism and falls at an angle π / 4 onto the hypotenuse face with a polarization coating 11, the radiation of the second channel passes through the prism - AP-90 ° 4 and also falls at an angle π / 4 on the hypotenuse face with a polarizing coating 11. The polarizing coating 11 is made so that it completely passes the radiation of one channel polarized in the sharpness of the incidence on the hypotenuse face (p-component), and fully reflects the radiation of another channel polarized in the orthogonal plane (s-component). Thus, the radiation of both semiconductor lasers emitting p-n junctions 6 and the polarization planes of which are respectively orthogonal to each other is completely, losslessly output to a single optical axis 12 and sent to the pan-optical lens 5.

The radiation beams of both semiconductor lasers are formed by a pancratic lens 5 (Figs. 1, 2) into narrow knife mutually perpendicular beams 13 and 14 in the picture plane of the optical information field 15 (Fig. 5) so that the long side of each beam corresponds to the size of the optical information field H, and the amplitude deviation angle of each beam along its short side from the optical axis 12, equal to ± 2γ, corresponds to a linear deviation of ± H / 2.

The beams 13 and 14 make a reciprocating rectilinear motion each along its coordinate, as shown in Fig. 5, deviating symmetrically with respect to the center of the optical information field (optical axis 12) with the phase difference π / 2 according to the same functional law, twice for one revolution of the scanner 2 bypassing the optical information field.

In the case of a linear scanning law, the dependence on the time t of the deviation of the position of the beams 13 and 14 from the center of the optical information field along the coordinates OX and OY is shown in Fig.6 and is determined by the expressions:

- along the coordinate OX (beam 13):

- OY coordinate (beam 14):

where hx (t) and hy (t) are the deviations of the beam position from the center of the optical information field (from the optical axis of the system) in two coordinates,

H is the size of the optical information field,

T - period of rotation of the scanner (time of formation of the frame).

In this case, each beam is illuminated twice in one period by a packet of short pulses of the photodetector of the control object 16 (Fig. 5).

As shown in Fig.6, the coordinates of the control object along the OX and OY axes or, otherwise, deviations from the center of the optical information field (from the optical axis of the system 12) x _a and y _a linearly depend on the time intervals Δt _x and Δt _y between the illuminations of the photodetector of the control object 16 with the corresponding laser beams during their forward and reverse travel, more precisely, Δt _x and Δt _{y are} proportional to the deviation of the control object from the edge of the optical information field and are determined by the expressions:

Electrical signals proportional to the measured time intervals Δt _x and Δt _y between the flashes of the photodetector are sent to the actuator, leading the control object to the optical axis 12 of the system.

Literature

1. Zuckerman S.T., Gridin A.S. Machine control with an optical beam. L .: Engineering, 1969

2. Patent RU 2100745 C1, IPC F41G 7/26, publ. 12/27/1997

3. Patent RU 2228505 C2, IPC F41G 7/26, publ. 05/10/2004, the prototype.

Claims (1)

An optical scanning system comprising two identical channels, each of which contains a semiconductor laser and a collimating component, and an optical scanner common to both channels, a system for outputting radiation from two channels to a single optical axis and a pan-objective lens, while the relative position of the two channels is such that pn junctions of semiconductor lasers are perpendicular to each other, characterized in that the optical scanner is located behind the collimating components of both channels along the rays and is made in the form e of the disk mounted for rotation and containing a closed annular region made along the edge of the working surface perpendicular to the axis of the disk, made in the form of steps of dihedral elements arranged around a circle at equal angular intervals, the radial dimensions of which are limited by the inner and outer diameters of the annular region, protruding the edge of each dihedral element lies in one plane perpendicular to the axis of the disk, with the corresponding edges of other dihedral elements and makes an angle π / 4 with the radius som drawn from the axis of the disk to the point of contact of the rib with the outer diameter of the annular region, while one of the corresponding faces of each dihedral element of the optical scanner is made mirror-like and tilted relative to the plane of the disk at its angle β, discretely changing from one dihedral element to another according to a given functional law, depending on the central angle of the disk α, for values of the angle α from 0 to π, the angle β increases from the minimum value (β ₀ -γ) to the maximum value (β ₀ + γ), for values of the angle α from π d about 2π the angle β decreases from the maximum value (β ₀ + γ) to the minimum (β ₀ -γ),
where β ₀ is the average value of the angle of inclination to the plane of the disk for two diametrically located mirror-reflecting faces,
γ is the maximum change in the angle β of the slope of the specular face from the average value β ₀ ,
in this case, both channels with collimating components are located relative to the optical scanner in such a way that the optical axes of each of them make an angle δ = (π / 2) -2β ₀ ) with the plane of the disk along the path of the rays and intersect with the mirror-reflecting faces of dihedral elements at points spaced one from the other by the central disk angle α equal to π / 2, the system for outputting the radiation of two channels onto a single optical axis, made in the form of a prism - rhombus BS-0 ° and prism AP-90 ° glued together hypotenuse faces on one of of which the polarization coating is applied, is located behind the optical scanner along the rays in such a way that the input faces of both prisms are parallel to the plane of the disk of the optical scanner, and are optically connected with it and with the collimating components of both channels by means of mirror-reflecting faces of its dihedral elements so that the optical axis of one the channel intersects with the input face of the prism - rhombus BS-0 °, and the optical axis of the other channel - with the input face of the prism AP-90 °, on the edge with a polarization coating, the optical axes of both channels intersect at one point, and behind the prisms along the rays they coincide both with each other and with the axis of the pancratic lens located along the rays behind the system for outputting the radiation of two channels to a single optical axis.

Images