JPS59166914A - Method of stabilizing light beam and light beam stabilizer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD This invention relates to a light beam stabilizer, and more particularly, to a stabilizer that senses and reduces angular deviation of a light beam from its intended path. Regarding.

BACKGROUND OF THE INVENTION At any given time, a light beam projected from a laser may exhibit sporadic deviations in its angular direction. Other lasers also experience such deviations, but primarily during warm-up. This deviation is commonly referred to as "pointing instability."

Although such instability is generally small, on the order of 10 milliradians, it becomes a problem in precision optical machining.

OBJECTS OF THE INVENTION It is an object of this invention to provide a new and improved optical beam stabilizer.

Another object of the invention is to provide a new and improved optical beam stabilizer that reduces the effects of pointing instability in the laser.

SUMMARY OF THE INVENTION In one form of the invention, detection means detects the angular deviation of the incoming light beam and generates an error signal accordingly. A correction means coupled to the detection means receives the error signal and acts to reduce the angular deviation.

As shown in FIG. 1, an incoming light beam 3, which is preferably a laser light beam and is highly collimated, is focused as a convergent beam 5 by first lens means 9. Focused on 7. The light from the focal point 7 is directed as a diverging light beam 15 to the second lens means 12 and is collimated by the second lens means 12 again into an output beam 18 . In the exit beam, rays 18A and 18B
Rays such as are substantially parallel, ie, collimated. A portion 21 of the output beam 18 is diverted from the output beam 18 by a redirecting means such as a beam splitter 23, focused by a third lens 23A, and directed to a photosensitizing device 26 at dashed line 27. The third shown
A rim is formed on the focal plane of the lens 23A.

Preferably, the photosensitive device 26 comprises two photosensitive devices 26A, 26B separated by a space 26G. The output of each photosensitive device 26A, 26B is connected to a servo amplifier 30.
are connected to respective inputs 28A and 28B of. This amplifier responds to the difference in signals applied to inputs 28A, 28B. The output 33 of the servo amplifier 30 is connected to actuation means, such as an electric motor 36 in the form of a d'Arson-Barr machine.

An electric motor 36 acts to rotate a directing means, such as a dielectric parallel plate 39, positioned in the path of the convergent beam 5. Preferably, the parallel plate is an optically flat thin glass plate. For this reason, the parallel plate 39 is connected to the broken lines 39A, 3
In addition to the position not shown in 9B, it can also occupy intermediate positions.

The first and second lens means 9.12 have a common focal point 40, called a confocal point. That is, the distance 43 is the distance 1i1
t46, and these distances are equal to each lens means 9.
equal to 12 focal lengths. Furthermore, a first lens means 9,
The confocal 40 and the second lens means 12 share a common optical axis 49
on top and therefore coaxial. Furthermore, as shown in Figure 1,
At the particular position of the component shown in FIG. 1 and the position of the incoming light beam 3, the confocal point 40 spatially coincides with the focal point 7.

The invention will now be described in detail with reference to FIG.

If the incoming light beam 3 shown in FIG. 1 deviates from its intended path, such as the path shown by axis 49, and instead follows a staggered path shown at 3A, then the incoming light beam 3A
is focused by the first lens means 9 into a convergent beam 5A. The convergent beam 5A is a different beam from the convergent beam 5 shown in FIG.

After passing through the parallel plate 39, the convergent beam 5A of FIG.
It is focused on a focal point 7A that does not coincide with the focal point 40. For this reason,
The focal point 7A of the deviated incoming beam 3A deviates from the confocal point 40. This deviation causes divergent beam 15A to follow the path shown, resulting in output beam 18A being a different beam than output beam 18 of FIG. Therefore, the portion 21A of the light beam deflected by the beam splitter 23 is shifted and follows a path as shown at 21A.

As shown in FIG. 2, deflected portion 21A of beam 19A does not intersect photosensitive device 26. As shown in FIG.

In FIG. 2, the illustration is exaggerated for ease of viewing.

The deflected portion 21A is the deflected portion 21
As shown at B, it is preferred that the light sensitive devices 26A, 26B, slightly offset on the light sensitive button device 26, generate unequal signals due to unequal illumination. Otherwise, 2
A deflected beam such as that shown in Figure 1'A will not be incident on either photosensitive device, so that the difference signal will be zero, and the photosensitive devices in Fig. 1 will be equally illuminated. (a difference signal of zero is generated) is used to be confused.

The difference in the output signals is amplified by the servo amplifier 30 and the amplified difference is transmitted to the actuating means 36 .
The parallel plate 39 is rotated to the position shown by the broken line 39B. The direction of rotation follows the algebraic sign of the difference signal. This rotation changes the angle at which the convergent beam 5A enters the three plates, and at the same time changes the angle at which the convergent beam 5A enters the three plates.
By changing the amount through which the convergent beam 5 passes, the convergent beam 5 is moved to a position such that the focal point 7A in FIG.
Orient A. An intermediate stage in this process is shown in FIG. 2 as focal point 7B on the way to focal point 40. 1st
The focal point 7B, the diverging beam 15B1, the outgoing beam 18B and the deflected beam portion 21B, while moving towards the solid line 7, 15, 18, 21 shown in the figure, are all shown in broken lines in FIG.

Therefore, as shown in FIG.
B moves in the direction shown by the -C1 arrow 101 due to the rotation of the plate 39. Therefore, the diverging beam 15A also moves in the direction of the arrow 101 due to the rotation of the parallel plate 39, and almost the same light enters both the photosensitizers 26A and 26B in FIG.
Therefore, the difference between those output signals becomes zero, and therefore the output of the servo amplifier 30 also becomes zero. At this point, the movement of the parallel plates is stopped.

As shown in FIG. 2, the plate 39 moves the beam 15A to the position 15B by rotating to the three positions indicated by the dashed lines.
but in this case position 15B is closer to light +1'llll 49 than beam 15A. Furthermore, as the incoming light beam 3A of FIG. 2 travels to the right, it travels upward in the diagram. Therefore, the convergent beam 5A and the diverging beam 15A also move upward. In this state, in order to move the focal point 7A to coincide with the confocal point 40, the portion 5B of the convergent beam 5A that moves in the direction of the arrow 101 must be moved toward the optical axis 49. Therefore, some portion of portion 5B must intersect optical axis 49. As shown in FIG. 2A, when the three plates rotate to position 39B, the portion 103 of the convergent beam 5A that was below the optical axis 49 before rotation
The portion of the converging beam 5A (portion 102
) moves below the optical axis 49. The reason for this is obvious.

The convergent light beam 5A travels upward as it advances to the right toward the focal point 7A, and the convergent light beam 5A is transformed by the rotation of the parallel plate 39.
Since A moves in parallel (to the dashed line position 5AA), the focal point 7A
In order to focus on a focal point 7B that is closer to the confocal point 40 than the convergent beam 5AA, the portion 102 of the converging beam 5AA must be moved across the optical axis 49. In other words, the ray at the center of the convergent beam 5A (not shown) is on the optical axis 49.
and within the plate 39 itself. Otherwise, this central ray would not intersect confocal 40 as it travels up and to the right. The three plates must be thick enough and rotated enough to allow this movement of the central ray.

As shown in FIG. 3, a d'Arlembard mechanism 104 supports three parallel plates. This d'Arson-Barr machine is shown diagrammatically in FIG. 1 as a pair of gears 105 driven by an electric motor 36.

Plate 39 is supported by shaft 106 and 'Nl 1
06 is supported by a bearing such as a watch jewel (not shown) housed in a housing 109.The shaft 106 is rotatable around an axis 107 that intersects the optical axis 49.A permanent magnet 112 surrounds @ 106 without contacting it. A permanent magnet 112 generates a first constant magnetic field vector, not shown by arrow 113. A wire coil 115 is coupled to shaft 106. permanent magnet 11
The servo amplifier 30 of FIG.
is electrically connected to output 33 of. (This connection is not shown in Figure 3. ) Coil 115 generates a second rotatable magnetic field vector 116 in response to the current at output 33 .

As the nature of the magnetic field, the first and second magnetic fields 113.116
tend to point in the same direction, so that the second magnetic field 116
has a tendency to rotate the plate 39. However, a spring (not shown) applies a force that biases plate 39 into a position perpendicular to optical axis 49. Therefore, in order for the plate 39 to rotate, the second magnetic field vector 116 must overcome the force of this spring. The rotation continues until the force overcomes, because the rotation tightens the spring, thereby increasing its force.

A schematic diagram illustrating the operation of the invention in some detail is shown in FIGS. 4A-4C. In FIG. 4A, the incoming light beams 3C-3F are shown following different paths with angular deviations from the optical axis 49. This may occur due to directivity instability when using laser light.

The light beams 3C to 3F rotate around the fact-L point 3. Beams 3C to 3F are focused by first lens means 9 into convergent beams 5C to 5F (shown as a single line rather than a pair of convergent lines as in FIG. 1) and their focal point 7C. 7F are in a confocal plane 133 that is perpendicular to the optical axis 49 and intersects the confocal point 40. The convergent beams 5C to 5F pass through respective focal points 7C to 7F as divergent beams 15C to 15F, and the divergent beams 15C to 15F pass through the corresponding incoming beams 3C to 3F.
The output beams 18C to 18F are collimated substantially parallel to the output beams 18C to 18F. (For clarity of drawing, it is not specifically shown that these are parallel.) The beam splitter 23 deflects the output beams 18C to 18F to the corresponding deflection portions 21C to 21.
F are deflected so that they project images (not shown) at different positions on the light sensing device 26 (not shown in FIG. 4A).

As shown in FIG. 4B, surfaces 144, 146 of parallel plate 39 are parallel. Therefore, when a convergent beam such as that shown at 50C exits plate 39 as convergent beam 50CC, it travels in generally the same direction as convergent beam 50C, but in plane 144.
It is moved or directed in the direction of arrow 148 parallel to 146 .

Furthermore, the greater the angle of incidence 150 that convergent beam 50C makes with the normal 152 to this surface, the greater the movement of beam 5CCC in the direction of arrow 148.

One reason for this is that the amount of material in plate 39 that converging beam 50C must pass through is greater.

For this reason, the incoming beam 3C in FIGS. 4A-4B
Regarding 3F to 3F, the convergent beams 5C to I5F and 50C are brought to the same number at the confocal point 40 by rotation of the plate 39 to the positions indicated by the dashed lines 39C to 39F. After passing through the confocal point, the convergent beams 5CC to 5FF are converted into an output beam 18 by the second lens means 12.
C to 18 F, these beams are approximately parallel to the optical axis 49 but slightly displaced on either side of the optical axis 49.

Of course, the light beam actually used is the 5 beam mentioned in the above explanation.
It does not look like a geometrically perfect line as shown in C. That is, what was explained in FIGS. 4A to 4C is as follows.
It is a theoretical ideal for explanation.

For this reason, from one point of view, the rotatable plate 39
9 and also intersects the optical axis 49, in the vicinity of the first magnetic field vector 113. The rotatable plate 39 has a second magnetic field vector 116
are associated, and the tendency of the second magnetic field vector 116 to be in the same orientation as the first magnetic field vector 113 causes rotation of the plate 39. Second vector 116 is rotatable and can change magnitude and direction.

This magnitude and direction are related to the amplified difference signal generated by the servo amplifier 30, which amplified difference signal represents the degree of angular deviation of the light beam 3 from the optical axis 49. Rotation of the rotatable plate 39 reduces the effect that angular deviations of the incoming light beam 3 have on the outgoing beam 18 of FIG. This rotation causes the deflected light beam 21 created by the output beam 18 to be transmitted to both light sensing devices 26.
It continues until it enters A and 26B in the same way.

Two light sensing devices 26A126B separated by space 26C
I mentioned using . The space 26C acts as a dead zone in the sense that no signal is generated for light incident on this dead zone. Thus, in one form of the invention, if the image projected by a properly aligned output beam 18 is small enough to fall entirely within the dead zone, no signal is generated by either photosensitive device 26A, 26B.

In situations where high accuracy is desired, it is desirable to have this condition in order to reduce vibration. Furthermore, the photosensitizing device M26A, 26B typically has different sheet resistances at different locations on its surface, and more generally has a temperature gradient across its surface, resulting in different Fermi regions of the photosensitizing device.・Different levels. For this reason, even if the same light is incident on both photosensitive devices, there is likely to be a slight difference in the signals generated. Therefore, the photosensitive device 26A also has 2
It is preferable to treat the output beam 18 as correctly positioned when the deflected beam portion 21 is incident on the dead zone so that no light enters 6B. Therefore, the zero output signal from both photosensing devices 26A, 26B is
The exceptions previously noted for exit beam 18A of FIG. 2 are taken to indicate that exit beam 18 is properly aligned. However, it is contemplated that improved photosensitizers (as improved photosensitizers will be developed in the future) may be able to use photosensitizers without dead zones. However, it now appears that there is no way to eliminate the dead zone without sacrificing some accuracy.

In one aspect, the first and second lens means 9-112, beam splitter 23 and photosensitizing device 26 of FIG. 1 detect the angular position of the output beam 18 with respect to the optical axis 49 as a reference. constitute a sensing means. This corresponds to detecting the position of the focal point 7. The servo amplifier 30, electric motor 36 and plate 39 adjust the angular deviation of the incoming light beam 3 with respect to the outgoing beam 18 without affecting the position of the incoming light beam 3 (not shown). It can be regarded as a correction means to reduce the influence of Output beam 1
8 is determined by the position of image 27 at the intersection of exit beam 18 and photosensitive device 16. Therefore, insofar as the plane 123 shown in FIG. 2 of the photosensitizing device 26 can be considered as a geometrical plane, the angular displacement of the incoming beam 3 will correspond to the lateral displacement of the image in one plane. converted.

This geometric plane associated with the photosensitizing device 26 is not within the output beam 18 itself, but from the position of the photosensitizing device 26 shown in FIG. 1 and the position indicated by the dashed line 126 in FIG. Look, there's no difference in principle. Of course, if the photosensitizing device 26 is in the position of the dashed line 126, at least a portion of the output beam 18 will be blocked.

The parallel plate 39 is not on the side indicated by the solid line 39, but on the confocal side 40.
It may also be at a position opposite to , that is, a position indicated by a broken line 129.

This invention is based on applicant's pending 1983 U.S. Patent Application No. 4
No. 66.741 and 1983 U.S. Patent Application No. 466.
It can be used in connection with the invention described in No. 7'57@.

As described above, by sensing the angular deviation of the incoming light beam from its intended path, and in response, modifying the incoming and eastward beam, and then extracting the light beam, the outgoing beam 1.
No. 8, an invention has been described which produces a light beam that travels along and is generally parallel to a predetermined path or optical axis 49. Various modifications can be made within the scope of the invention, including using lenses 9.12 of different dimensions. Furthermore, what has been described above is a stabilizer that stabilizes the incoming light beam 3 with respect to angular deviations within a single plane, ie the plane of FIG. If a second plate similar to plate 39 is additionally placed at the position of broken line 129, it can work together with plate 31 to stabilize the deviation of the light beam 3 in all planes. . A second plate (not shown) rotates about an axis perpendicular to the root three axes. The photosensing device 26 has four elements and a four-quadrant photosensing device ff (see FIG. Two of these elements are connected to a servo amplifier 30 which controls the rotation of plate 39.The remaining two are replaced by actuating means similar to actuating means 36 (not shown). ) is connected to a similar servo amplifier (not shown) which drives the actuating means 36.
rotates plate 39 about an axis, and similar actuating means rotates a similar plate about an axis perpendicular to the axis of plate 39. This makes it possible to compensate for angular deviations of the incoming beam 3 in any plane.

The first and second lens means 9.12 have been described as being coaxial. This is not a strict requirement.

The other two arrangements and possibly other arrangements are also sufficient. One arrangement is to position these two lenses so that their focal planes coincide, so that both optical axes are coincident or parallel. The second arrangement positions the two lenses so that their focal points coincide and thus both optical axes are aligned or intersect.

[Brief explanation of the drawing]

1 is a schematic diagram of one form of the invention; FIG. 2 is a partial view of the apparatus of FIG. 1; FIG. 2A is a diagram showing the movement of a light beam by the parallel plates of the invention; FIG. 4A and 4B are views showing the optical path of the apparatus shown in FIG. 1, and FIG. 4C is a perspective view of one type of the invention, and FIG.
FIG. 3: Incoming light beam, 9.12: Lens, 23: Beam splitter, 26: Light sensing device, 36: Actuation means, 39: Parallel plate. patent applicant

Claims (1)

Claims: 1) detection means for detecting an angular deviation of an incoming light beam from a predetermined reference and generating an error signal accordingly; and compensation means responsive to said incoming light beam to substantially remove the effects of angular deviations in a light beam extracted from said incoming light beam. 2. In the light beam stabilizer according to claim 1), the detection means has first and second lens means having a confocal focus, and the first lens has a confocal shape. light sensing for receiving an incoming light beam, said second lens means transmitting said extracted light beam, and said detection means generates a signal indicative of the intersection position of said extracted light beam with a predetermined reference plane. A light beam stabilizer with an element. 3) The light beam stabilizer according to claim 2), wherein the correction means includes a Darson-Bar mechanism that drives a rotatable parallel plate through which the incoming light beam passes. vessel. 4) A device for stabilizing an incoming light beam having an optical axis, comprising a first lens means for focusing the incoming light beam to a focal point on a confocal plane; the position of the focal point is determined by the angle between the incoming light beam and the optical axis; and sensing means for sensing the position of said focus and generating an error signal representative thereof; a second lens means for transmitting the received light as a substantially collimated beam of light; and a steering means for directing the light focused by the first lens means to a predetermined point in response to the error signal. an apparatus having means. 5) in an apparatus for stabilizing a light beam generated by a source, sensing means for sensing an angular deviation of the path of the light beam from a predetermined path; and coupled to the sensing means;
and correcting means for directing the light beam towards a predetermined path without moving the light source in response to the sensed deviation. 6) The apparatus according to claim 5), wherein the sensing means comprises a deflector for deflecting a portion of the light beam along a second path and for detecting a displacement of the deflected portion from a predetermined position. A device consisting of a light detection means for detecting light. 7) The device according to claim 5), wherein the correction means is constituted by a rotatable parallel plate. 8) In a device for stabilizing an incoming light beam having an optical axis, the incoming light beam is directed to a point whose position depends on the angle between the incoming light beam and the optical axis. first lens means for focusing and sensing means for receiving the focused light beam and transmitting it as a substantially collimated output beam and sensing the position of said point and generating an error signal representative thereof; and correction means for directing said incoming light beam to a predetermined point in response to said error signal. 9> In an apparatus for stabilizing an incoming light beam having an optical axis, first lens means responsive to the incoming light beam generates a focused beam; second lens means for generating a substantially collimated beam; and second lens means positioned within the path of said collimated beam for directing a portion of the collimated beam away from the optical axis of the incoming optical beam. a beam splitter for redirecting to a light sensing means capable of generating an error signal in response to an angular deviation of the beam; and an amplifier coupled to the light sensing means for generating an output signal in response to the error signal; a rotatable plate positioned in a path of the focused beam and coupled to the amplifier for rotating the focused beam in response to the output signal. 10) An apparatus according to claim 9, wherein said first and second lens means have the same focal length. 11) The apparatus according to claim 10, wherein said first and second lens means are coaxial and have a common focus. 12. The device according to claim 9), wherein the rotatable plate is an optically flat glass plate. 13) The device according to claim 9, wherein the light sensing means comprises two light sensing means separated by space and having a difference representing a deviation from the intended path of the redirected beam. A device containing two light-sensitive elements that generate a signal as an output signal. 14) A method for stabilizing a light beam, comprising focusing the light beam through a plate using a first lens means to a focal point on a confocal plane, and then focusing the light beam onto the lens means of the tube 2 and outputting the light beam. A method comprising transmitting an incident beam of light, sensing deviations of said focus from a predetermined point, and rotating a plate in response to said deviations to reduce the deviations. 15) A method according to claim 14, in which the plate has two parallel surfaces. 16) A method as claimed in claim 14, wherein said first and second lens means are positioned at a distance from said confocal plane equal to their respective focal lengths. 17) The method of claim 14, wherein the sensing step includes deflecting a portion of the output beam to a light sensing device. 18) A method as claimed in claim 14, wherein the light sensing device comprises two light sensitive elements each generating a signal, and the difference between the signals represents said deviation.