JPH0625659B2 - Attitude sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) To perform processing operations such as cutting and welding of materials using a high energy beam such as a laser beam and an ion beam, as shown in FIG. It is necessary to keep the axis Z of the processing machine head such as a laser beam gun perpendicular to the workpiece surface J and to keep the gap d between the tip of the processing machine head and the workpiece surface J constant. The attitude sensor of the present invention is mounted on the processing machine head to automatically detect the attitude (inclination and gap) of the processing machine head with respect to the workpiece surface J, and generate control information for automatically controlling to a regular attitude. It is a thing.

(Prior Art) A conventional technology used for detecting the attitude of a processing machine head (hereinafter referred to as a laser gun) G of a typical laser processing machine will be described with reference to FIG. In the conventional laser gun, a plate-shaped electrode C is attached to the tip of the laser gun G to form an electrostatic capacitance between the plate-shaped electrode C and the surface J of the workpiece, and the plate-shaped electrode C is formed.
The change in the capacitance due to the change in the gap d between the workpiece and the surface J of the workpiece is detected as the amount of electrical change such as the voltage or the oscillation frequency. With this method, the average value of the gap d can be obtained, but the inclination between the Z axis, which is the central axis of the laser gun G, and the workpiece surface J is unknown.

(Problems to be Solved by the Invention) Problems to be solved by the present invention are (1) to realize an attitude detector capable of automatically detecting the attitude of the laser gun G. For example, in FIG. 8, laser gun G
At which angle the central axis Z of the object is attached to the surface J of the work piece (often perpendicular to the surface), and whether the gap d conforms to the specified value that is prevailing during processing. That is.

(2) The posture detector can be installed without increasing the total weight and external dimensions of the laser gun G.

(Means and Embodiments for Solving Problems) An embodiment of a laser gun G equipped with the attitude sensor of the present invention is shown in FIG. In this attitude sensor, a plurality of measuring units M ₁ , M ₂ , ..., M _n are arranged around the center Z of the laser gun G. Usually, 3 to 4 is sufficient for n.

As shown in FIG. 1, the casing of the laser gun G is vertically divided into B ₁ and B _2, and an annular light receiving lens L _R is provided between them. The optical axis of the light receiving lens L _R coincides with the Z axis.
The light source is guided by an optical fiber code I _j provided along the generatrix on the outer periphery of the housing B ₁ , and the light emitted from the fiber end is condensed into a thin parallel beam by the minute condenser lens L _f . The light beam condensed in this way is Z-shaped as shown in FIG.
It is incident on the surface J of the work piece from an angle direction of 90 ° -α with respect to the axis, and produces bright points a _i . The light receiving system captures the diffusely reflected light from a _i . The light condensed by the light receiving lens L _R is incident on the light receiving element S _i provided in the housing B ₁ and is converted from an optical signal to an electric signal to obtain an electric output. Light receiving element S _i
Are arranged on the image _forming surface S or S ′ including the image B _io of the brightness a _io when the distance between the laser gun G and the surface J of the workpiece is a specified value. The distance b _i between the image B _i and the center plane of the lens is the imaging formula of the lens. Required by. As shown in FIG. 2, _S'is an image forming plane which always satisfies the above formula for l _ai . When the distance l _ai between the light receiving lens L _R and the bright point a _i deviates from the specified value,
position which the reflected light is incident to the light receiving element S _i from changes a _i position of a _i is changed. The change in the position of point a _i is
In a general processing machine head, the incident angle α is 70 ° to 85 °, and the change amount of l _ai is at most several mm, so it is only about 1 mm.

The light-receiving lens L _R is shared by the measurement units M _i (i = 1,2, ...), which is useful for simplifying the structure and reducing the price.

The light receiving element S _i is an element that has a linear elongated shape, generates an electrical output when light is incident, and can know the incident position of the light from the output. For example, a commercially available PSD (photosensing device), a silicon photodiode array, or the like, or one end of a plurality of optical fibers is closely arranged on a straight line to form a light receiving portion, and the received signal light is relayed by an optical fiber to a laser gun. Outside the
You may use what provided the photodiode array for light reception in the other end.

Next, the optical measurement principle of one measurement unit M _i will be described with reference to FIGS. 2 to 4.

In the structure of FIG. 1, the lower housing B ₂ blocks the diffused reflection light of the bright point a _{i from} entering the portion on the opposite side of the light receiving lens L _R ,
Furthermore, since used as a thin linear such as one-dimensional PSD as the light receiving element S _i, how the irregular reflection light from bright points a _i in the measurement unit M _i is incident on the light receiving element S _i is
Approximately, it may be treated as a phenomenon in a plane including the optical axis Z of the light receiving element S _i and the light receiving lens L _R. Further, the light receiving element S _i may be mounted so as to face the object to be measured, but in order to improve the accuracy, as shown in FIG. 2, the incident angle with respect to the Z axis is 90 ° −α. Tanβ = M · tanα where M is a light receiving element S _i which is inclined by 90 ° -β with respect to the Z axis so that M satisfies the magnification of the lens (M = f / ( _lao- f)).

The radius of the inner edge of the annular light receiving lens L _R is r _i , the radius of the outer edge thereof is r ₂ , the distance between the Z axis and the bright point a _i is r _L , and the light receiving lens L _R
Let l _ai be the distance between the center plane of the and the bright point a _i , then r _L , l
The manner in which the bright spot reflected light on the light receiving element S _i changes with the change in _ai is as follows.

In FIGS. 3 and 4, a _io is a bright spot at a specified position from the light receiving lens L _R , a _i1 is a bright spot far from the specified position, and a _i2 is a bright spot near the specified position. Shows,
_These images are shown by B _i0 , B _i1 , and B _i2 . l _aij (j =
0, 1, 2) are the center plane of the light receiving lens L _R and the bright point a _{ij, respectively.}
(J = 0,1,2).

It is desirable that r _L be near the processing point, but here, the movement of the image forming point when the distance from the sensor to the object changes in r ₁ <r _L <r ₂ which is considered to be a practical range will be described.

FIG. 3 shows the case where r ₁ <r _L <r ₂ . The bright point a _io on the reference work surface A is imaged on B _io on the image surface S. When the work surface moves away from A to A ', the bright spot moves to a _i1 and the received image is formed on B _i1 as shown in FIG. An image _{B'i1 with} is formed. In this case, the image position moves from B _i0 to B ′ _i1 to the right on the S surface. Since it can be considered that the light receiving element rows are arranged on the S surface, the position of the light receiving element is determined by the output signal (B ′ _i1
If it is known from the average value of, the change amount of the distance to the work surface can be obtained. Next, when the work surface approaches the position from A to A ″, the imaging position moves left on the S surface as shown in FIG. 3 (b), and the movement amount corresponds to the distance change amount. .

FIG. 4 shows an example in which a _i0 occurs at r _L = r ₁ . When the work surface is far from the reference surface A to A '(Fig. 4
(a)), the image B _i0 moves to the right on the S surface and moves to B ′ _i1 . Conversely, when the image approaches from A to A ″ (FIG. 4 (b)), the image B _i0
Moves to the left on the S surface to become _B'i2 , and each represents the change in the distance from the work surface, as in FIG.

In FIGS. 3 and 4, the image forming plane S is represented by S ′, and the image _forming points B _i0 , a _i0 , a _i1 and a _i2 described in FIG.
The line connecting B _i1, B _i2, if provided light receiving element S _i, B _i1, since B _i2 is not affected by the lens size r ₁ and r _2, image blur when viewing on S plane Therefore, the accuracy of distance detection can be significantly improved.

As an example of the light receiving characteristic of the measurement unit, an experimental result when a laser with a light output of about 1 mw is used as a light source and a light beam is obliquely incident on an object is shown. A metal surface was measured using a PSD as a light receiving element with α = 80 °, _la0 = 80 mm, and lens magnification M = 1/6. As for the light receiving characteristic, as shown in FIG. 6, an output voltage with good linearity was obtained with respect to the variation amount Z of the distance to the work surface.

The measuring unit M _i is shifted around the central axis Z of the laser gun G by a constant angle, for example, by 90 °.
If the number (M ₁ , M ₂ , M ₃ , M ₄ ) is arranged, how the distance between the four bright points a _i (i = 1 to 4) and the light receiving lens _LR is calculated from the measured value _la0. Since it is possible to know whether there is a deviation, the posture of the laser gun G can be corrected. In this case, if the attitude of the laser gun G is controlled so that the distance data of the four units are matched, the Z axis of the laser gun G is kept perpendicular to the workpiece surface J, and the distance of the four units is The Z axis of the laser gun G can be kept at a constant inclination with respect to the workpiece surface J by appropriately setting the reference value of l _ai and performing calculation with the measured value.

Next, noise detection will be described. With a laser machine,
There are countless interferences such as reflection and scattering at a processing point of a processing laser beam such as CO _2, measurement interference due to noise light from various light sources in a factory, induction from an ultrasonic processing machine or a washing machine, and radiation. However, these frequency ranges are at most 10 ~
Since it is 30 KHz, the signal light beam used for measurement is 30 KHz.
If modulated at a high frequency of Hz or higher, a noise component can be removed and its measurement interference can be removed by using a bandpass filter or a highpass filter on the electric output side of the light receiving element.

The attitude detection system according to the present invention will be described with reference to FIG.

The OPS is a high-frequency modulated signal light generator, which sends the signal to the laser gun G through the optical fiber I _i (i = 1, 2, ...).
Assembling the sensor of the laser gun G is as described above, but if the light emitting end of the light beam uses a cylindrical lens having a cosine refractive index distribution in the radial direction of the diameter from the center, it can be matched with the optical fiber code diameter. Since it can be configured to have a diameter of 1 to 2 mm, it is possible to form a groove in the generatrix direction on the outer circumference of the laser gun G and embed it together with the fiber. Its structure is as shown in FIG.

DET _i (i = 1, 2, ...) Is a signal detection circuit of the light receiving system.

After signal converted from light into electrical output V _i by the light receiving element S _i is amplified to Josa noise component by the filter, is output as a digital signal. The output data, that is, the sign indicating whether the bright point a _i is on the light receiving element S _i on the far side or the near side with respect to the normal position, and the information such as the change amount of the distance are transmitted via an interface such as RS-232C. , Sent to the sensor computer SPC. The sensor computer SPC calculates the four measurement data in real time and transfers the attitude control data to the controller MCP of the processing machine. Based on this information, the controller MCP of the processing machine generates drive power for the posture control, and corrects the posture of the laser gun G correctly.

(Effects of the Invention) As described above, the processing machine head incorporating the attitude sensor of the present invention is small, lightweight and low in price, and does not change the conventional working space of the processing machine head, and it has a complicated recess. It can also be applied to various types of work such as in the office. In addition, the use of this attitude sensor enables automatic attitude control during work, and will greatly contribute to the promotion of automation of work such as automatic tracing in the future. In particular, it is effective for controlling the attitude of the gun in the laser processing machine.

[Brief description of drawings]

FIG. 1 is a diagram showing a laser processing machine head equipped with an attitude sensor of the present invention. 2 to 4 are views showing an optical system of the attitude sensor of the present invention. FIG. 5 is a measuring circuit for measuring the detection characteristic of the present invention. FIG. 6 is a diagram showing the detection characteristics of the light receiving system of the present invention. FIG. 7 is a diagram showing a posture detection system of the present invention. FIG. 8 is a view showing the structure of the laser processing machine head of the present invention.

Claims (1)

[Claims] 1. An annular light-receiving lens, and means for generating a plurality of thin signal light beams which are arranged around the optical axis of the light-receiving lens and are emitted in a direction converging on the optical axis. And a means for detecting the light receiving position at the image forming point of the image of the spot formed by the light receiving lens when the spot formed by the signal light beam on the surface of the workpiece and the light receiving lens have a predetermined distance. Equipped with a long and narrow linear light receiving element array,
In the case of attitude detection, the incident section of the reflected light from the spot incident on the light receiving element is provided with an electric circuit for discriminating which side of the spot image formation point in the case of the predetermined distance,
An attitude sensor, which detects an attitude of a processing machine head with respect to a surface of a workpiece from a plurality of outputs of the electric circuit.