DE102014116621A1 - Two-dimensional light section sensor with UV laser light - Google Patents

Abstract

A two-dimensional light section sensor for measuring the surface contour of an object has a UV laser light source (21), a visible light laser light source (22), a first optical system (25) which transmits the beam path (3a) of the light from the UV laser light source (21). and converging the optical path (3b) of the light from the visible light laser source (22) to a common optical path (3), second optics (26) for projecting the light from the UV laser light source (21) and the light from the laser light source (22) for visible light in the common beam path (3) as a light line (4) on a surface of the object, a two-dimensional light sensor (8), and a third optical system (7) for imaging the light line (4, 4a, 4b, 4c ) on the object on the two-dimensional light sensor (8). This provides a two-dimensional light section sensor with UV laser light with high reliability.

Description

The present invention relates to a two-dimensional light section sensor with UV laser light, with which a height contour of the surface of an object can be determined according to the measuring principle of triangulation.

Optical distance sensors have the advantage that a non-contact distance measurement is possible with them. Known measurement principles for optical distance measurement are triangulation and chromatic confocal distance measurement. In this case, two-dimensional light-section sensors can simultaneously record the entire height contour along a line with a single measurement. For this purpose it is necessary to project a line of light onto the object whose distance to the distance sensor is to be measured.

Particularly suitable for producing a fine light line is the use of a laser light source in the two-dimensional light section sensors. The fine light line projected onto the surface to be measured is detected laterally with an optical system and projected onto a two-dimensional light sensor. From the signal of the two-dimensional light sensor, the height contour of the surface is then determined with the evaluation principle of triangulation using an evaluation logic. The image on the two-dimensional light sensor is geometrically distorted and therefore usually first has to be linearized in a subsequent logic.

Depending on the laser power, the laser light sources used in two-dimensional light-section sensors become protection classes 1 . 2 . 3R and 3B assigned. From the laser protection class 3R is the accessible laser radiation for the eye and the laser protection class 3B possibly also dangerous for the skin. According to existing health and safety regulations, it is from the laser protection class 3R necessary to have the application monitored by a laser safety officer. Therefore, two-dimensional light section sensors with laser light sources of the laser protection classes 3R and 3B for industrial applications rarely and then only used with strict safety requirements.

In the case of two-dimensional light-section sensors, laser wavelengths in a range from 400 to 900 nm are mostly used. The use of UV laser light with wavelengths below 400 nm is basically possible, but to be used UV laser light sources fall into the laser protection class 3B so that their application is avoided in practice.

It is known that the human eye shows a blinking reflex with strong light stimulation with visible light. It manifests itself by a rapid closure of the eyelids within milliseconds and serves to protect the eye. However, there is no blinking reflex when UV light is applied to the eye. The eyelid reflex can only be observed with a light stimulus with visible light.

In the case of objects that are transparent to visible light, the surface of this object can not be measured, or at any rate only with a large error, using a two-dimensional light-section sensor that works with visible light (wavelength range from 400 nm to 790 nm). So z. B. the surfaces of car headlights, which are made of plastic and are transparent to visible light, are measured not with visible light but only with UV light.

It is an object of the invention to provide a two-dimensional light section sensor with high reliability, with the surfaces of objects can be reliably and accurately measured, which are transparent to visible light, such. B. headlight washers.

The object is achieved by a two-dimensional light section sensor according to claim 1.

In the two-dimensional light section sensor, the beam path of the UV light from the UV laser light source is combined with the beam path of the light from the laser light source for visible light to form a common beam path. When a user is exposed to the light in the common optical path, the light from the visible light laser source results in a blinking reflex which reliably protects the user's eye from the harmful effects of light from the UV laser source and from the visible light laser source , Therefore, the two-dimensional light section sensor according to the invention has a higher reliability than a comparable two-dimensional light section sensor, which works exclusively with UV light, which can not trigger the eye closure reflex. The use of the UV laser light source allows the two-dimensional light section sensor according to the invention to measure the surface of an object transparent to visible light, provided that the object is made of a material which is impermeable to the light from the UV laser light source.

Further developments of the invention are specified in the subclaims.

In a preferred embodiment, the conditions for the laser class are for the light in the common beam path 2 Fulfills. Thus, the two-dimensional laser cutting sensor meets high Operational safety criteria and can be operated without complex security measures.

In a preferred embodiment, the two-dimensional light section sensor has a control which only releases the emission of the light from the UV laser light source when a surface contour has been detected with the light from the laser light source for visible light. Although the surface contour detected alone with the visible light may be very defective in measuring visible light transmissive material, the detection of this defective surface contour may still be used to ensure that the common beam path is uninterrupted and, in particular, no body part such as B. the head is located with the most vulnerable eye of a user in the common beam path.

In a preferred embodiment, the first optic comprises a dichroic filter / mirror which is transparent to the light from the visible light laser light source and reflective to the light from the UV laser light source. In an alternative preferred embodiment, the first optic comprises a dichroic filter / mirror that is transmissive to the light from the UV laser light source and that is reflective to the light from the visible light laser light source. With the two last-mentioned alternative preferred embodiments, the common beam path can be generated in a simple manner with high accuracy and with low losses.

In a preferred embodiment, the UV laser light source and the visible light laser light source are each formed as a laser diode. Laser diodes are particularly space-saving, inexpensive laser light sources that can provide sufficient intensities for use in a two-dimensional light section sensor.

In a preferred embodiment, the wavelength of the light from the visible light laser light source is in a range of 500 nm to 790 nm and more preferably in a range of 600 nm to 700 nm. In these wavelength ranges, the blinking reflex can be triggered particularly reliably, whereby the Operating safety is increased.

In a preferred embodiment, the wavelength of the light from the UV laser light source is above 200 nm, and more preferably in a range above 300 nm. These wavelengths are particularly well suited to the measurement of most visible light transparent materials.

In a preferred embodiment, the two-dimensional light section sensor has a housing which inaccessibly covers the beam path of the light from the UV laser light source to the exit from the first optics to the user, thus ensuring that a user only the light from the UV laser light source can be exposed in the common beam path. This significantly increases the reliability of the two-dimensional light section sensor.

Further advantages and effects of the invention will be explained and illustrated with reference to the detailed description of an embodiment shown in the figures. In the figures show:

1 a two-dimensional light section sensor according to the invention; and

2 a light source portion of the light section sensor according to the invention

1 with an optical system for generating a common beam path for visible light and UV light.

The in 1 illustrated light section sensor according to the invention 1 According to an embodiment of the invention comprises a light source section 2 , a lens 7 , a two-dimensional light sensor 8th and a controller 9 on. The light source section 2 points as in 2 illustrated a UV laser diode 21 with a corresponding first laser optics 23 , a red laser diode 22 with a corresponding second laser optics 24 , a dichroic filter / mirror 25 , a line optic and a housing 20 with a light exit opening 27 on.

The UV laser diode 21 generates UV light with a wavelength of 375 nm. With the first laser optics 23 becomes the UV laser beam 3a bundled to focus on an object surface. After the exit of the bundled UV laser beam 3a from the laser optics 23 this applies to the UV laser beam 3a slanted dichroic filter / mirror 25 and is by this with a small loss of 1% towards line optics 26 reflected. The red laser diode 22 produces visible, red laser light with a wavelength of 635 nm, which is suitable for triggering a blinking reflex in the case of a user looking into the laser beam. With the second laser optics 24 The red laser beam is focused to focus on the object surface. After the exit of the bundled red laser beam from the laser optics 22 this hits the dichroic filter / mirror tilted to the red laser beam 25 , which now acts as a filter, and is characterized by this with a small loss of 4% towards line optics 26 passed without distraction, so by means of the dichroic filter / mirror 25 the beam path 3b of the red laser beam with the beam path 3a of the UV laser beam to a common beam path 3 is merged.

The line optics 26 generated from the laser beam, which is composed of the red laser beam and the UV laser beam, by widening in the x direction in 1 a thin, in the y-direction perpendicular to the expansion direction focused light line 4 on the object surface. The line optics can z. B. be a cylindrical lens.

With the side-mounted lens 7 becomes the light line 4 on the object surface on the two-dimensional light sensor 8th displayed. The two-dimensional light sensor 8th is designed as a spatially resolving CMOS sensor. An evaluation logic in the controller 9 calculated from the signal of the light sensor 8th Using the measuring principle of triangulation, a contour of the surface along the light line 4 , As in 1 illustrates the position of the image of the light beam depends 4 on the two-dimensional light sensor 8th from the position of the light line in the z direction (ie, the height of the surface). In 1 are three lines of light 4a . 4b and 4c represented, which are arranged at different positions in the z-direction. The light line 4b represents the (in y-direction) exactly focused on the surface light line, while the light lines 4a and 4b the light lines with just tolerable blur in y-direction represent, so the area between the light lines 4a and 4c the maximum measuring range 5 the device is in the z direction. In 1 is still the maximum measuring range 6 the device in the x-direction, which by the length of the light line 4 is determined.

In order to measure a three-dimensional surface profile consisting of a multiplicity of surface contours respectively recorded along a line in the x direction, the object whose surface is to be measured is relative to the two-dimensional light section sensor 1 along the y-direction, ie perpendicular to the light line 4 method. The surface profile can then be composed of surface contours recorded at different times.

The light line 4 has the light content of the red beam and the laser beam. In particular, light is from the UV laser diode 21 after merging the beam path 3b of the red laser beam with the beam path 3a of the UV laser beam to a common beam path 3 mixed with light from the red laser diode everywhere. The areas covered by the red laser beam therefore contain all areas swept by the UV laser beam after the merging of the two laser beams. Ideally, both laser beams cover exactly the same area. The intensity of the red laser diode 22 and the UV laser diode 21 are selected so that the mixed light in the common beam path 3 the conditions of the laser protection class 2 Fulfills. When determining the laser protection class of the light in the common beam path 3 It can be assumed that the eye has a very short exposure time, since the eye blinking reflex limits the exposure of the sensitive retina. When looking into the light of the common beam path 3 the red eye is triggered by the red-eye reflection, and the retina is protected by closing the eyelid within milliseconds of exposure.

To before turning on the UV laser diode 21 make sure the beam path 3 is free and in particular no body part such. B. the head of the user in the beam path 3 is located, initially only the red laser diode 22 switched on and only with the visible red light from the red laser diode 22 made a surface contour measurement. Only after the controller 9 has detected a certain surface contour, gives the controller 9 turning on the UV laser diode 21 free. The surface contour of a surface is determined by the controller 9 only recognized if the surface is in the maximum measuring range 5 located in z-direction. Is z. B. the head of a user in the beam path 3 , so the line of light on the user's head is outside the maximum measuring range 5 be in the z-direction and therefore from the controller 9 no elevation profile can be detected.

Further, the reliability of the two-dimensional light section sensor according to the present embodiment is increased by the housing 20 , which detects the beam path of the light from the UV laser diode 21 to the outlet 27 covering the user inaccessible to ensure that a user is exposed to the light from the UV laser diode 21 only in the common beam path 3 can be exposed.

The two-dimensional light section sensor according to the invention 1 can be used to measure surfaces that are transparent to visible light but impermeable to UV light. The two-dimensional light section sensor 1 can z. B. used to measure a surface contour of a headlight lens made of plastic. In order to prevent yellowing of this clear plastic headlamp lens, the surface of the headlamp lens is provided with a two-dimensional light-section sensor before the measurement with a UV-opaque coating.

Modifications of the above-described embodiment of a two-dimensional light section sensor are possible.

In the embodiment described above, the use of a red laser diode emitting visible light having a wavelength of 635 nm has been described. However, other visible light laser light sources may be used. In particular, another laser light source that emits light having a wavelength in a range of 400 nm to 790 nm may also be used. Preferred is a laser light source that emits light having a wavelength in a range of 500 nm to 790 nm, and particularly preferred is a laser light source that emits light in a range of 600 nm to 700 nm.

In the embodiment described above, the use of a UV laser diode emitting UV light having a wavelength of 375 nm has been described. However, other laser light sources may also be used for UV light. In particular, it is also possible to use another laser light source which emits UV light having a wavelength of more than 200 nm. Preferred is a laser light source that emits UV light having a wavelength of more than 300 nm.

As a two-dimensional light sensor, in the above embodiment, the use of a two-dimensional CMOS sensor has been described. However, it is also the use of another two-dimensional light sensor, such. B. a CCD sensor possible, which can measure the light intensity spatially resolved.

As line optics, the use of a cylindrical lens has been described in the above embodiment. However, any other optics suitable for projecting the light from the UV laser light source and the light from the visible light laser light source in the common optical path as a light line onto a surface of the object may also be used.

Likewise, instead of the dichroic filter / mirror, another optical system can be used, which is suitable for combining the optical path of the light from the UV laser light source and the optical path of the light from the laser light source for visible light to form a common optical path.

LIST OF REFERENCE NUMBERS

1

two-dimensional light-section sensor

2

Light source section

3

common beam path

4

light line

4a

Light line at the upper end of the measuring range

4b

Light line at the focal point of the line-generating optics

4c

Light line at the lower end of the measuring range

5

Measuring range in z-direction (height)

6

Measuring range in x-direction

7

lens

8th

two-dimensional light sensor

9

control

20

casing

21

UV laser diode

22

red laser diode

23

first laser optics

24

second laser optics

25

dichroic filter / mirror

26

line optics

27

outlet opening

Claims (10)

Two-dimensional light section sensor for measuring the surface contour of an object, comprising: a UV laser light source ( 21 ), the light from the UV laser light source ( 21 ) has a wavelength below 400 nm; a laser light source ( 22 ) for visible light, the light from the laser light source ( 22 ) for visible light has a wavelength in a range from 400 nm to 790 nm; a first optic ( 25 ), which the beam path ( 3a ) of the light from the UV laser light source ( 21 ) and the beam path ( 3b ) of the light from the laser light source ( 22 ) for visible light to a common beam path ( 3 ) merges; a second optic ( 26 ) for projecting the light from the UV laser light source ( 21 ) and the light from the laser light source ( 22 ) for visible light in the common beam path ( 3 ) as a light line ( 4 . 4a . 4b . 4c on a surface of the object; a two-dimensional light sensor ( 8th ); and a third optic ( 7 ) for imaging the light line ( 4 . 4a . 4b . 4c ) on the object on the two-dimensional light sensor ( 8th ). Two-dimensional light section sensor according to claim 1, wherein for the light in the common beam path ( 3 ) the conditions for the laser class 2M are met. Two-dimensional light section sensor according to claim 1 or 2 with a controller ( 9 ), which control the emission of light from the UV laser light source ( 21 ) releases only when with the light from the laser light source ( 22 ) a surface contour was detected for visible light. Two-dimensional light section sensor according to one of claims 1 to 3, wherein the first optics ( 25 ) has a dichroic filter / mirror that is transparent to the light from the laser light source ( 22 ) for visible light and is reflective for the light from the UV laser light source ( 21 ). Two-dimensional light section sensor according to one of claims 1 to 3, wherein the first optics ( 25 ) has a dichroic filter / mirror that is transparent to that for light from the UV laser light source ( 21 ) and is reflective of the light from the laser light source ( 22 ) for visible light. Two-dimensional light section sensor according to one of claims 1 to 5, wherein the UV laser light source ( 21 ) is a UV laser diode. Two-dimensional light section sensor according to one of claims 1 to 6, wherein the laser light source ( 22 ) is a laser diode for visible light. Two-dimensional light section sensor according to one of claims 1 to 7, wherein the wavelength of the light from the laser light source ( 22 ) for visible light in a range of 500 nm to 790 nm, and more preferably in a range of 550 nm to 650 nm. Two-dimensional light section sensor according to one of claims 1 to 8, wherein the wavelength of the light from the UV laser light source ( 21 ) is greater than 200 nm, and more preferably more than 300 nm. Two-dimensional light-section sensor according to one of Claims 1 to 9, having a housing ( 20 ) which the beam path ( 3a ) of the light from the UV laser light source ( 21 ) until the exit from the first optic ( 25 ) is inaccessible to a user such that, during operation of the two-dimensional light slit sensor, the user is exposed to the light from the UV laser light source (FIG. 21 ) only in the common beam path ( 3 ) may be exposed.

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