JPH03237303A - Measuring head structure for speckle length measuring instrument - Google Patents

Abstract

PURPOSE:To hole the measurement sensitivity constant even if the distance between a measuring head and an object body s different by providing a window where the laser beam from a collimator lens should be projected in a casing and arranging an image sensor opposite the window. CONSTITUTION:A semiconductor laser 21, the collimator lens 25, and a tempera ture sensor 6 are stored in a temperature control housing 22 and an electronic cooling device 3 is installed in contact with the housing 22 to hold not only the laser 21, but also the lens 25 accurately at constant temperature, so that there is no focal length, etc., even when a plastic lens 25 is used. Further, even when the temperature of a measurement atmosphere drops, the temperature in the casing 10 is held proper and the lens 25 is prevented from clouding owing to dew condensation. Then the interval between the laser 21 and lens 25 is so adjusted and set as to obtain a parallel beam as the laser beam projected from the lens 25, and then the measurement sensitivity can be held constant irrelevantly to the distance between the measuring head 1 and object body.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a speckle length measuring device that measures the amount of movement of an object by using a speckle pattern generated by diffused light from the surface of an object irradiated with laser light. It is related to the structure of

(Prior Art) Conventionally, a target object is irradiated with a laser beam emitted from a semiconductor laser, and the speckle pattern generated by the diffused light from the object surface is observed, and the speckle pattern caused by movement, deformation, etc. of the object is observed. The amount of movement of the object based on the change,
Methods for measuring the amount of deformation, etc. are known (for example, "Optical Measurement Handbook" published by Shokusen Shoten, pp. 234-24).
(page 5).

By the way, in the technical field of video processing, COD, which exhibits high resolution, has been put into practical use as an image sensor that replaces conventional image pickup tubes, and by applying this COD as a speckle pattern detection sensor, it is possible to achieve high precision. Measurement is possible.

(Question to be solved @) However, until now, only the principle of the above measurement method and the basic equipment configuration have been clarified, and only the specific arrangement of equipment and details to improve measurement accuracy have been clarified. The structure, etc., has not yet been sufficiently researched, and it has not yet been put into practical use.

For example, when putting a speckle length meter into practical use to measure the amount of movement of an object, a semiconductor laser, a collimator lens,
It is necessary to install component parts such as an image sensor with high precision, but in the past, these parts were positioned independently, making it difficult to position them with high precision. or,
Depending on the location where the semiconductor laser is installed, temperature changes may be severe, and this may cause mode hopping in the semiconductor laser, resulting in a problem in which the sameness of the speckle pattern on the same laser irradiation surface cannot be maintained. Furthermore, measurement accuracy may deteriorate due to disturbance light other than laser light entering the image sensor.

The purpose of the present invention is to put a speckle length measuring meter into practical use.
It is an object of the present invention to provide a measurement head structure that allows each component device to be positioned easily and with high accuracy, and that provides high measurement accuracy regardless of the measurement atmosphere.

(Means for Solving the Problems) The measurement head structure of the speckle length measuring meter according to the present invention includes a semiconductor laser (21) in a sealed casing (10),
a collimator lens (25) that condenses laser light from the semiconductor laser (21) to form a laser beam; an electronic cooling device (3) that controls the temperature of the semiconductor laser (21) to be constant; and the temperature control device. A temperature sensor (6) that measures the temperature of the semiconductor laser (21) and an image sensor (4) that photoelectrically converts the speckle pattern into an image signal are housed and fixed at predetermined positions, respectively, and the unit A measuring head (1) was constructed. Casing (1
0) is provided with a window (14) through which the laser beam from the collimator lens (25) should exit, and the image sensor (
4) is placed facing the window (14).

The semiconductor laser (21), the collimator lens (25), and the temperature sensor (6) are arranged in a housing chamber (23) provided in an integrated temperature control housing (22), and are arranged on the outer surface of the temperature control housing (22). An electronic cooling device (3) is installed closely.

The distance between the semiconductor laser (21) and the collimator lens (25) is set so that the laser beam emitted from the collimator lens (25) becomes a parallel beam.

The position of the image sensor (4) is defined so that the scanning area during photoelectric conversion is symmetrical about a plane containing the optical axis of the laser beam.

The window (14) of the casing (10) is formed by an optical filter that allows frequency components of the laser beam and frequency components in the vicinity thereof to pass, and is formed by a collimator lens (25).
The laser beam is placed at a slight angle with respect to the optical axis of the laser beam emitted from the laser beam.

The semiconductor laser (21) and the temperature sensor (6) are attached to a common substrate (5).

In addition, there is a laser beam aperture hole (2
8) is installed.

(Functions and Effects) During length measurement, the measuring head (1) is installed so that the optical axis of the laser beam emitted from the window (14) is perpendicular to the surface of the target object, and the measuring head (1)
An external circuit for processing the image signal obtained from the image sensor (4) is connected to. Further, the temperature sensor (6) of the measuring head (1) is connected to a well-known temperature control circuit, and the output end of the control circuit is connected to the electronic cooling device (3).
The temperature of the semiconductor laser (21) is thereby controlled to be constant.

The laser light from the semiconductor laser (21) passes through the collimator lens (25) and becomes a laser beam, which is emitted from the window (14) of the casing (10) toward the moving object.

The reflected and diffused light from the surface of the moving object is reflected by the casing (10)
The speckle pattern is transmitted through the window (14) and incident on the image sensor (4), whereby the speckle pattern is converted into an image signal, and the image signal is sent to the external circuit,
Arithmetic processing is performed to calculate the distance traveled by the moving object.

According to the above measurement head structure, if the casing (10) of the measurement head (1) is installed with high precision, each component within the casing (10) can be positioned with high precision at the same time, resulting in highly accurate length measurement. is possible. Further, since the inside of the casing (10) is maintained at an appropriate temperature by the operation of the temperature sensor (6) and the electronic cooling device (3), high measurement accuracy can be obtained regardless of the measurement atmosphere.

The semiconductor laser (21), collimator lens (25) and temperature sensor (6) are connected to the temperature control housing (2).
If the electronic cooling bag W (3) is placed in close contact with the housing (22), the semiconductor laser (2)
In addition to 1), the collimator lens (25) is also maintained at a constant temperature with high precision, and optical characteristics such as focal length do not change even when a plastic collimator lens (25) is used. Further, even when the temperature of the measurement atmosphere decreases, the inside of the casing (10) is maintained at an appropriate temperature, and the collimator lens (25) is prevented from fogging due to dew condensation.

When the semiconductor laser (21) and the temperature sensor (6) are mounted on a common substrate (5), heat is conducted through the substrate (5), so that the temperature sensor (6) can control the temperature of the semiconductor laser (21). Temperature detection accuracy can be improved.

If the distance between the semiconductor laser (21) and the collimator lens (25) is adjusted so that the laser beam emitted from the collimator lens (25) becomes a parallel beam, the measurement head (1) and the target object The measurement sensitivity can be maintained constant regardless of the distance, which is advantageous for the signal processing required to calculate the amount of object movement.

Furthermore, as described above, by installing the image sensor (4) in a position symmetrical to the plane containing the optical axis of the laser beam, the speckle pattern imaged on the image sensor (4) can be The light intensity distribution, that is, the level of the image signal obtained from the image sensor (4) is made uniform, which is convenient for signal processing such as sampling of the image signal.

Furthermore, this arrangement allows the amount of object movement and the image sensor (
4) The relationship with the amount of movement of the speckle pattern above can be simplified.

By forming the window (14) of the casing (10) with an optical filter, disturbance light that enters the window (14) from the outside is blocked, and the measurement results from the disturbance light entering the image sensor (4). A decrease in accuracy is prevented.

When the window (14) is arranged at a slight inclination with respect to the optical axis of the laser beam, even if the laser beam from the collimator lens (25) is reflected by the window (14), the optical path of the reflected light will be Semiconductor laser (21) depending on the tilt
Therefore, mode hop caused by the reflected light entering the semiconductor laser is prevented.

In addition, by installing a slit plate (27) in the laser beam optical path and focusing the laser beam from the collimator lens (25) to a predetermined diameter, the pixel pitch of the image sensor (4) and the speckle between the paths can be reduced. This makes it possible to increase the contrast of the speckle pattern on the image sensor (4) and at the same time efficiently detect the characteristics of the speckle pattern.

Therefore, according to the above measurement head structure, the measurement head (1)
Not only is it easy to handle due to its unitization, but the configuration of each part as described above provides high measurement accuracy.
It is fully possible to put it into practical use.

(Example) Hereinafter, the specific configuration of the measurement head structure according to the present invention will be described along with the drawings. It should be noted that the examples are for illustrating the present invention, and should not be construed as limiting the invention described in the claims or reducing its scope.

As shown in FIG. 1, the measurement head (1) includes a semiconductor laser unit (2), an electronic cooling device (3), and an image sensor (4) arranged in one dimension in a sealed casing (10). etc., to form a unit.

As shown in the figure, the casing (10) has a rectangular parallelepiped-shaped main body with an opening on one side, and a rubber gasket (11) that closes the opening.
and a cover (12) are fixed with screws to form a closed container. A window (14) for laser beam emission is provided in the front wall of the casing (10).

As shown in FIG. 2, the semiconductor laser unit (2) has a laser beam generation section consisting of a semiconductor laser (21), a collimator lens (25), etc., mounted in a temperature control housing (
22) and are integrated into one. The semiconductor laser (21) is mounted on the first substrate (5) together with the temperature sensor (6), and the substrate is screwed and fixed to the back of the temperature control housing (22) to connect the semiconductor laser (21> and the temperature sensor). The sensor (6) is housed in a housing chamber (23) within the temperature control housing (22).Furthermore, the temperature control housing (22) has a screw hole (24) that communicates with the housing chamber (23). It is formed.

The collimator lens (25) is fixed to the end of a beam adjusting screw tube (26) formed with an external thread, and is attached to the screw tube (26).
6) into the screw hole (24) of the temperature control housing (22), the collimator lens (25) is inserted into the storage chamber (23) or the screw hole (24).
contained within.

As a result, the accommodation chamber (23) of the temperature control housing (22) contains the substrate (5) and the collimator lens (25).
The semiconductor laser (21
) and a temperature sensor (6) will be placed. Therefore, the temperature sensor (6) and the semiconductor laser (21) are always maintained at the same temperature, and the temperature control of the semiconductor laser (21) is performed accurately without error.

The semiconductor laser (21) and collimator lens (2) can be adjusted by rotating the beam adjusting screw tube (26) in the temperature control housing (22) in forward and reverse directions.
5) can be adjusted, and here, as shown in FIG. 3, the spacing is set so that the laser beam (8) emitted from the collimator lens (25) becomes a parallel beam.

As a result, the radius of curvature Ls of the laser beam on the target object (7) in FIG. 9 becomes infinite, and the measurement sensitivity can be kept constant regardless of the difference in distance between the measurement head and the target object. In addition, in FIG. 9, the following formula holds true.

X ” ((L a'cO8”θs/ L 5-cos
θo) + cosθoix where: X: Amount of movement of the speckle pattern on the image sensor Lo: Distance between the target object and the image sensor
) A slit plate (27>) having a laser beam aperture hole (28) is fixed to the end opposite to the laser beam aperture hole (28). The diameter α is approximately the same as the arrangement pitch (e.g. 13 μm) of the CCDs constituting the one-dimensional image sensor (4).
1 or slightly larger.

The average speckle diameter α is α=1.22λZ/L based on the wavelength λ of the laser beam and the distance L0 between the -dimensional image sensor (4) and the target object.

For example, when the wavelength λ of the laser beam is 780 nm and the distance L0 between the -dimensional image sensor (4) and the target object is approximately 25 to 75 mm, the laser beam aperture (28) is The inner diameter is set to approximately 2 mm.

As shown in FIG. 1, a flat electronic cooling device (3) is installed on a base (13) fixed to the bottom surface of the casing (10), and the semiconductor laser is placed in close contact with the top surface of the electronic cooling device (3). Unit (2) is fixed.

As shown in FIG. 6, the electronic cooling device (3) has a large number of P-type semiconductors (33) between a pair of ceramic plates (31, 32).
) and N-type semiconductors (34) are arranged alternately, and these are connected in -rows by electrode plates (35) to form electrode plates (34) at both ends.
It has a well-known structure in which lead wires (36) are connected to the terminals (35) and 35), respectively.

As shown in FIG. 1, the base (13) has a second substrate (51) at its end on the window (14) side, which has a through hole (53) through which the laser beam from the semiconductor laser unit (2) passes. A dimensional image sensor (4) is installed on the substrate (51).
) is fixed.

As shown in FIG. 4 and FIG.
), the arrangement directions of the CCDs constituting the detection unit (41), that is, the scanning direction S, are orthogonal to each other, and the center position (0 point) of the scanning area of the detection unit (41) is aligned with the optical axis of the laser beam. It is positioned so as to be placed on a plane P that includes the scanning direction S and is perpendicular to the scanning direction S.

Therefore, the diffused laser light reflected by the target object and incident on the one-dimensional image sensor (4) is symmetrical and approximately uniform with respect to the center position (point 0) of the signal scanning area as shown in FIG. This results in a strong intensity distribution. In such a distribution, all the signals to be sampled when binarizing the image signal exceed the lowest level at which signal processing is possible, and highly accurate length measurement is possible.

Furthermore, in FIG. 9, COS θ5=eO3θo=1, and the amount of movement of the target object (7) and the image signal can be handled in a simple relationship.

The window (14) of the casing (10) shown in FIG. 1 is formed of a glass plate that transmits only infrared rays, and external light other than laser light is blocked by the window (14). Further, as shown in FIG. 4, the glass plate is mounted in an attitude inclined at a slight angle θ (approximately 2 degrees) with respect to a plane perpendicular to the optical axis of the laser beam. Therefore, the semiconductor laser unit (2
) is reflected on the inner surface of the window (14), the reflected light will travel along an optical path away from the semiconductor laser, and there is no risk of it directly entering the semiconductor laser (21). Therefore, the semiconductor laser (21) does not cause mode hops due to reflected light.

As shown in FIG. 1, inside the casing (10) there is a third substrate (52) above the semiconductor laser unit (2).
is fixed.

In addition to the circuit for driving the semiconductor laser (21), the first to third substrates (5), (51, and 52) are directly connected to the one-dimensional image sensor (4) as shown in FIG. A first stage amplifier (9) and a buffer amplifier (90) are formed.

FIG. 7 shows an example of the configuration of an external circuit connected to the measurement head (1) to calculate and display the amount of movement of an object based on the image signal from the -dimensional image sensor (4). It shows.

As is well known, the dimensional image sensor (4) repeats scanning in the COD array direction at regular intervals in response to a reset signal, a start signal, and a shift signal sent from the buffer amplifier (90). The output signal of the sensor (4) is sent to the sample hold circuit (91) via the first stage amplifier (9).
This eliminates noise specific to CCDs.

The output signal of the sample and hold circuit (91) is sent to the binarization circuit (93) via the gain control amplifier (92), whereby the image signal as shown in Fig. 8 is binarized, and further the binarization The signal is sent to a correlator (94), and the cross-correlation function between the speckle pattern at the reference position of the target object and the speckle pattern after movement is sequentially calculated while shifting the reference position, and the calculation results are It is sent to the computer (96). The microcomputer (96) calculates the moving distance of the object from the peak position of the cross-correlation function, and displays the result digitally on the display (97).

Further, the operations of the buffer 7 amplifier (90), sample hold circuit (91), binarization circuit (93), and correlator (94) are controlled by timing signals supplied from a timing generator (95). There is.

During measurement, the measurement head (1) shown in FIG. ) is installed parallel to the direction of movement.

In this state, the circuit shown in FIG. 7 is operated to measure the moving distance of the target object.

According to the above speckle length measuring meter, by accurately installing the casing (10) of the measuring head (1), the semiconductor laser (21), collimator lens (25) and -dimensional image sensor in the casing (10) can be simultaneously installed. −(
4) can be positioned with high accuracy, and high-precision length measurement is possible without being affected by the measurement atmosphere etc. due to the above-mentioned configuration of each part.

The above description of the embodiments is for illustrating the present invention, and should not be construed to limit or reduce the scope of the invention described in the claims.

Further, it goes without saying that the configuration of each part of the present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the technical scope of the claims.

For example, the external circuit to be connected to the measurement head (1) is not limited to the one shown in FIG. 7, and various known circuits that calculate the moving distance based on the speckle pattern can be employed.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway exploded perspective view of a measuring head according to the present invention, FIG. 2 is an exploded perspective view of a semiconductor laser unit, FIG. 3 is a side view illustrating the positional relationship between the semiconductor laser and the collimator lens, and FIG. Figure 5 is a side view explaining the tilted state of the window, Figure 5 is a front view explaining the position of the one-dimensional image sensor, Figure 6 is a sectional view of the electronic cooling device, Figure 7 is a block diagram of the external circuit, FIG. 8 is a graph showing the light intensity distribution on the one-dimensional image sensor, and FIG. 9 is a diagram explaining the relationship between the amount of movement of the target object and the amount of movement of the speckle pattern on the image sensor.

Claims (1)

[Claims] [1] Irradiating the surface of a moving object to be measured with a laser beam, photoelectrically converting a speckle pattern appearing on an observation surface opposite to the laser irradiation surface of the object into an image signal, In a speckle length measuring meter that measures the amount of movement of an object based on a change in the image signal as the object moves, a semiconductor laser (2
1) and a collimator lens (25) that focuses the laser light from the semiconductor laser (21) to form a laser beam.
, an electronic cooling device (3) that controls the temperature of the semiconductor laser (21) constant, and a semiconductor laser (21) for controlling the temperature.
A measurement head (1) is constituted by accommodating a temperature sensor (6) that measures the temperature of 21) and an image sensor (4) that converts the speckle pattern into an image signal,
The casing (10) is provided with a window (14) through which the laser beam from the collimator lens (25) should be emitted, and the image sensor (4) is arranged facing the window (14). Measuring head structure of Le length meter. [2] Semiconductor laser (21), collimator lens (25)
) and the temperature sensor (6) are arranged in a storage chamber (23) provided in the integrated temperature control housing (22), and the electronic cooling device (3) is placed in close contact with the outer surface of the temperature control housing (22). A measurement head structure according to claim 1 installed. [3] Semiconductor laser (21) and collimator lens (25)
2. The measurement head structure according to claim 1, wherein the interval between the collimator lenses (25) is set so that the laser beam emitted from the collimator lens (25) becomes a parallel beam. [4] The measurement head according to claim 1, wherein the image sensor (4) is positioned so that the scanning area during photoelectric conversion is symmetrical about a plane containing the optical axis of the laser beam. structure. [5] The measurement head structure according to claim 1, wherein the window (14) is provided obliquely with respect to the optical axis of the laser beam. [6] The measurement head structure according to claim 1, wherein the window (14) is formed by an optical filter that allows frequency components of the laser beam and frequency components in the vicinity thereof to pass through. [7] The measurement head structure according to claim 1, wherein the semiconductor laser (21) and the temperature sensor (6) are mounted closely on a common substrate (5). [8] A slit plate (27) having an aperture hole (28) for narrowing the laser beam to a predetermined diameter in the optical path of the laser beam.
) is installed in the measuring head structure according to claim 1.