OPTOELECTRONIC APPARATUS FOR SECURING A SOURCE OF DANGER

Abstract

An optoelectronic apparatus for securing a source of danger in a spatial zone includes at least one image sensor that works in the infrared spectrum and that can generate range-resolved data of the spatial zone as well as an evaluation unit that is configured for the evaluation of the data for the detection of objects in a three-dimensional protected space within the spatial zone, wherein the source of danger is additionally at least partly secured by a mechanical partition that is at least very largely permeable to visually visible light. To provide a solution that prevents or at least reduces disturbing optical influences from outside the partition, it is proposed that the partition is coated with a layer such that the non-coated layer that is at least partly transparent for the image sensor is visible for the image sensor in a defined manner through the layer and is opaque.

Claims

1. An optoelectronic apparatus for securing a source of danger in a spatial zone, the optoelectronic apparatus having at least one sensor that works in the infrared spectrum and that can generate range-resolved data of the spatial zone, as well as an evaluation unit that is configured for the evaluation of the data for the detection of objects in a three-dimensional protected space within the spatial zone, wherein the source of danger is additionally at least partly secured by a mechanical partition that is at least very largely permeable for visually visible light, and wherein the partition is coated with a layer in such a way that the non-coated partition that is at least partly transparent for the sensor becomes visible for the sensor in a defined manner and becomes opaque in the infrared spectrum by means of the layer.

2. The apparatus in accordance with claim 1, wherein the layer is a reflective film.

3. The apparatus in accordance with claim 2, wherein the reflective film includes a proportion of particles that are retroreflective in the infrared spectrum and a proportion of light-absorbing particles.

4. The apparatus in accordance with claim 2, wherein the reflective film is of a multilayer structure and has a first optically transparent film layer having IR-retroreflective particles and has a second film layer that is likewise optically transparent, but IR absorbing.

5. The apparatus in accordance with claim 2, wherein the reflective film is of a multilayer structure, with particles that are retroreflective in the infrared spectrum being held between two film layers.

6. The apparatus in accordance with claim 1, wherein the layer comprises sprayed on IR-retroreflective particles.

Description

[0020] The invention will be explained in more detail in the following also with respect to further features and advantages by way of example with reference to embodiments and to the enclosed drawing. The Figures of the drawing show in:

[0021] FIG. 1 a schematic three-dimensional representation of an apparatus in accordance with the invention; and

[0022] FIGS. 2 to 4 side views of a camera, monitored protected space, partition and object.

[0023] FIG. 1 shows in a schematic three-dimensional representation the structure of an embodiment of the apparatus 11 in accordance with the invention on the basis of a three-dimensional stereoscopic camera 10. Two camera modules 12, 12′ are mounted at a known, fixed spacing from one another. Both cameras 12, 12′ each record the image of a monitored zone 14. The cameras 12, 12′ have an objective 16, 16′, only indicated, having an imaging optics. The angle of view of the this optics is shown by dashed lines in FIG. 1, which each form a visual pyramid, and amounts to 45° , for example. An image sensor 13, 13′ is provided in each camera 12, 12′. This image sensor 13, 13′ is a matrix-shaped imaging chip that records a rectangular pixel image and can, for example, be a CCD sensor or a CMOS sensor.

[0024] An illumination source 18 is arranged at the center between the two cameras 12, 12′. A laser having a power between 1 and 8 W serves as a light source for the illumination source 18. The laser of the illumination source 18 generates pulses of a length of 1-10 ms. The laser power can also be higher, provided that the protection rating allows it and the higher costs can be accepted. The use of one or more LEDs is alternatively also conceivable.

[0025] A diffractive optical element 20 is arranged downstream of the illumination source 18 in the optical axis to generate an illumination pattern in the monitored zone 14. The illumination source 18 generates light of a predefined and known wavelength that is in the infrared range. The diffractive optical element 20 deflects, selectively for the wavelength, the light incident from the illumination source 18 only into specific regions of the monitored zone 14. The arising illumination pattern can be a spot pattern or circular pattern arranged in a regular, that is matrix-like, form.

[0026] Different illumination patterns can also be generated using a different diffractive optical element 20. Different pattern generation methods are also conceivable, e.g. by means of a stochastic microlens array. In this respect, any desired pattern can be generated that is helpful and of high contrast for the evaluation, e.g. a linear pattern, a checkerboard pattern or a grid pattern. In principle, a mask can also be used instead of a diffractive optical element 20. This is, however, less advantageous since a portion of the light energy scattered in is lost in the mask. Alternatively to a regular pattern, an irregular pattern can be provided that can therefore not be cast back onto itself in any region by geometrical operations such as displacement, reflection or rotation. A conclusion can then be drawn from the pattern zone on the position in space, whereas a regular pattern does not allow this due to ambiguities.

[0027] A control and evaluation unit 22 is connected to the two cameras 12, 12′ and to the illumination source 18. The unit 22 switches the light pulses of the illumination source 18 and receives image signals from the two cameras 12, 12′. The control and evaluation unit 22 furthermore calculates three-dimensional image data of the spatial zone 14 with the aid of a stereoscopic disparity estimate.

[0028] A robot arm 24, which represents a source of danger, is located in the spatial zone 14 monitored by the apparatus 11. When the robot 24 moves, no unauthorized object and in particular no body part of an operator may be located in its radius of movement. A virtual three-dimensional protected space 26 is therefore laid around the robot arm 24. The evaluation unit 22 evaluates the image data in this protected space 26 to recognize unauthorized object intrusions.

[0029] If the evaluation unit 22 recognizes an unauthorized intrusion into the protected zone, a warning is output via a warning or shutdown device 28 or the source of danger is secured, that is the robot arm 24 is stopped in the example shown. In this respect, it depends on the application whether a warning is sufficient or a two-stage security is provided in which a warning is initially given and a shutdown is only made on a continued object intrusion or an even deeper penetration.

[0030] The safety sensor 10 is configured as fail-safe for applications in safety engineering. This inter alia means that the safety sensor 10 can test itself in cycles under the required response time and that the output to the warning and shutdown device and the warning and shutdown device 28 is designed as fail-safe, for example as dual channel. The control and evaluation unit 22 is equally also fail-safe, that is it evaluates over dual channels and/or uses algorithms that can test themselves.

[0031] Instead of the shown stereoscopic method, the invention also comprises further three-dimensional camera systems, for instance a time-of-flight camera that transmits light pulses or modulated light and draws conclusions on distances from the time of flight of light or actively triangulating cameras that utilize distortions in the structure of the illumination pattern or the position of parts of the illumination pattern in the recorded image for the calculation of distance data. In principle, the use of light field cameras would also be possible.

[0032] In addition to this securing with the virtual protected space 26, the apparatus has a mechanical partition 30 that mechanically separates a freely accessible outer zone 32 from the protected zone 26. The partition 30 is visually transparent, that is permeable in the visible light, so that an operator can observe the robot 24 from the outer zone 32. The partition 30 can e.g. comprise acrylic glass or a metal grating for this purpose.

[0033] In accordance with the invention, the partition 30 is coated with a layer 34 (FIGS. 2 and 3) such that the non-coated partition 30 that is at least partly transparent for the camera 10 is visible for the camera in a defined manner through the layer 34 and is opaque. Objects that are located in the freely accessible zone 32 can then no longer disturb the camera 10, on the one hand, and it is ensured, on the other hand, that the camera 10 can always “see” the partition 30 as a full-area (in contrast with gratings), opaque wall.

[0034] The layer 34 in an embodiment of the invention comprises a film 36 that has a sufficient remission or retroflection in the direction of the camera 10 in the IR spectrum. In this context, sufficient means that the wanted signal strength is large enough in comparison with the unwanted signal strength to carry out a signal evaluation. The film 36 can be adhered to the partition 30 or can be hung when the partition 30 is configured as a metal grating. The film 36 is transparent visually, that is in the visible spectral range.

[0035] So that the film does not reflect the IR light, it includes a functional particle mixture comprising a proportion of IR-retroreflective particles 40 (e.g. microspheres) and a proportion of IR-absorbing and simultaneously visually transparent particles 42 (e.g. ITO particles). The particles 40, 42 can either be applied onto the film 36 or can be admixed to a melt for the film manufacture. The particles 40 have the properties that they are transparent in the visual light spectrum and are remitting in the IR spectrum.

[0036] The proportion of the remitted IR light and simultaneously of the transmitted visible light can be controlled with the aid of the particle concentration. It applies in this respect that the higher the particle concentration, the higher the proportion of remitted IR light and the smaller the proportion of transmitted visible light. A good particle concentration produces a sufficient proportion of the IR light reflected back to the light source and a sufficient transparency (of the visible light). It is sensible to provide different films to be able to take account of the lighting conditions on site.

[0037] In another embodiment of the film 36 (FIG. 4), the latter can be formed as a multilayer film 44 and can have a layer 46 having a visually transparent and IR-absorbing property on which a further layer 48 is applied that is visually transparent and includes IR-retroreflective particles.