DE202019103270U1 - Triangulation light scanner - Google Patents

Abstract

Triangulation light button (1) with
a first light transmitter (2) for emitting transmitted light into a detection zone (3), the first light transmitter (2) being preceded by a transmission optics (4), in particular a lens,
at least one first light receiver (6) with at least one receiver line with receiving elements (5) for receiving light from the detection zone (3) which is remitted by an object (7) to be detected, the receiving elements (5) generating respective received signals,
a receiving optics (8) arranged in the beam path between the detection zone (3) and the first light receiver (6) for generating a light spot from the remitted light on the first light receiver (6), the position of the light spot on the first light receiver (6) being in the Triangulation direction depending on the distance of the object (7) results, and a control and evaluation unit (9) for generating a detection signal from the received signals on the basis of the position of the light spot on the first light receiver (6), with a further second light transmitter ( 11) is provided as a reference light transmitter (12) for safety-related self-testing, characterized in that a first mirror (13) is arranged to direct the light beams from the reference light transmitter (12) onto the first light receiver (6), the first mirror (13 ) is a concave mirror (17).

Description

The present invention relates to a triangulation light scanner according to the preamble of claim 1.

It is known to determine the presence and / or distance of objects in a monitored area with light sensors that work according to the triangulation principle. Such a triangulation sensor comprises a light transmitter, for example a light-emitting diode or a laser, and optionally a transmission optics to send a transmission light beam into a detection zone to an object to be detected that may be located there. The transmitted light can be remitted by such an object, i. H. Diffuse or specularly reflected and detected by a light receiver, which together with a receiving optics forms a receiving unit. In known solutions, the light receiver consists of at least one row of photosensitive receiving elements.

Depending on the distance between the triangulation probe and the remitted object, the position of a light spot generated by the remitted light on the light receiver changes in the so-called triangulation direction. There is a clear geometric relationship between the point of impact on the light receiver and the distance of the detected object. By evaluating a light distribution on the light receiver, the distance between the object and the light scanner can be determined. Furthermore, with a corresponding evaluation of the light distribution on the light receiver, it can be determined whether an object is located inside or outside a predetermined limit, also referred to as the scanning range.

In order, in particular, to achieve a high level of accuracy in determining the distance, such a light receiver must have a large number of photosensitive receiving elements which are arranged next to one another in the triangulation direction.

In triangulation light scanners with background suppression, the light receiver comprises at least two receiving elements, a so-called near element being arranged in such a way that it is hit by a light beam when it is reflected from an object that is located within a close range in front of the triangulation light scanner. By definition, the far range is further away from the triangulation probe than the near range. For signal evaluation, a difference is formed between the photodiode currents in these two areas.

The structure of a light barrier according to the state of the art for an industrial application is described below. One task is the object detection in a surveillance room or a surveillance area. A transmission pulse generator generates a periodic, digital control signal for the transmission stage. The control signal can, for. B. consist of simple or complex pulse patterns. The transmission stage generates a transmission current that varies over time from the digital control signal. The amplitude of the transmission current can usually be parameterized. The transmission diode converts transmission current into optical power. The transmission optics contain a transmission tube, screens, a transmission lens and a front pane. The monitoring space contains the entire space to be monitored in front of the sensor and can contain the object to be detected, a background object, a reflector or other, also disruptive objects such as mirrors, lamps or external light sources.

Receiver optics contain a receiver tube, diaphragms, a receiver lens and the front screen. The receiver elements are a plurality of photodiodes for converting optical power into electricity and are e.g. B. arranged as a line. An evaluation circuit calculates an object detection signal from the time course of the signal from the receiver elements and the knowledge of the control signals of the transmission stage. The object detection signal is output via a physical switching output.

If this light barrier is used in the form of a light switch, it should be recognized whether there is an object on the transmission axis within a previously defined distance, namely in the monitoring area. This object can be, for. B. act about a person. If this person could be injured by the effects of a machine within the monitoring area and the light barrier is intended to reduce this risk by switching off the machine, then the safety of the overall system of machine, control and light barrier must be considered. This consideration is simplified if the light barrier monitors its function itself and switches to the safe state in the event of an error.

The prior art shown has the disadvantage that the entire signal flow runs through the monitoring area. It is therefore not possible to test the blocks transmitting stage, transmitting diode, transmitting optics, receiving optics and receiver elements without a known, well-defined monitoring area.

The problem can be solved by introducing a reference object cyclically into the beam path and in this state the monitoring space block is well defined. In this Operating status can then z. B. the output signals of the receiver elements and / or downstream blocks are compared in the evaluation circuit with reference signals. In the event of deviations, a safe state is activated.

The disadvantage of this solution is the effort required to develop and create this solution and the reduction in machine throughput, since part of the productive time has to be used for reference runs and reference measurements.

One object of the invention is to provide a safe triangulation light scanner in terms of machine safety.

The object is achieved according to claim 1 by a triangulation light scanner with a first light transmitter for emitting transmitted light into a detection zone, the light transmitter being preceded by a transmitting optics, in particular a lens, at least one first light receiver with at least one receiver line with receiving elements for receiving light from the Detection zone which is remitted by an object to be detected, the receiving elements generating respective received signals, receiving optics arranged in the beam path between the detection zone and the first light receiver for generating a light spot from the reflected light on the first light receiver, the position of the light spot being on the first Light receiver in the triangulation direction depending on the distance of the object results, and a control and evaluation unit for generating a detection signal from the received signals on the basis of the position of the light spot on the first light receiver, a further second light transmitter being provided as a reference light transmitter (14) for safety-related self-testing, a first mirror being arranged to direct the light beams of the reference light transmitter onto the first light receiver, the first mirror being a concave mirror.

The triangulation light scanner is a safety sensor. A safety sensor should have the highest possible safety integrity level (SIL) in accordance with IEC 61508 / IEC 61511. According to the present invention, safety is safety in the sense of machine safety. For example, the EN / IEC 61496 standard regulates the requirements for a safe sensor or a safe electro-sensitive protective device (ESPE) to protect danger areas. Machine safety is regulated in the EN 13849 standard. Safety is guaranteed, for example, by a two-channel or two-channel diverse structure of the control and evaluation unit for fault detection and functional testing. The distance measuring triangulation light scanner or distance sensor according to the present invention is designed, for example, to be intrinsically safe and detects internal errors. If an error is discovered, an error signal is generated, for example. The triangulation light button or distance sensor also has sensor testing. The triangulation light scanner at hand has self-monitoring through internal reference paths.

The control and evaluation unit detects objects in the detection zone or protective field violations by an object or a person and can output a safety-related switch-off signal in order to stop a dangerous movement of a machine or a vehicle or a part of a machine or the machine that is part of the Braking the machine or the vehicle. This can e.g. B. via safe switching signals z. B. OSSD signals (Output Safety Switching Device signals) or safe distance data, distance data or safe location data of the intervention event can be implemented.

According to the invention, a second light transmitter is provided as a reference light transmitter for safety-related self-testing. The reference light transmitter can be integrated next to the light receiver for testing the light receiver. In this way, the receiving channel can be tested for the time behavior or timing as well as signal level-dependent effects. The reference light transmitter is preferably attached close to the light receiver and illuminates the light receiver.

Due to the spatial proximity, the additional reference light transmitter can be implemented with a less powerful and therefore more cost-effective light transmitter. The transmission power of the reference light transmitter is set, for example, so that the signal level corresponds to the actual received signals of the light receiver. The same applies to the timing of the transmission signal from the reference light transmitter.

Optical light intensities with different intensity profiles or amplitudes can be used to test the light receiver. Overload measurements in particular can be carried out easily in this way.

The dynamics of the light receiver can be tested via an adjustable signal level of the reference light transmitter. The reference light transmitter can be built with a less powerful and therefore more cost-effective transmitter diode, since the spatial proximity means that a lower transmitter power is sufficient to generate comparable signals on the receiver.

By measuring the signal height with different reference amplitudes, the dynamics and sensitivity of the light receiver can be checked. The measurements can also be used to compensate for aging effects or degradation or to compensate for temperature effects. For this purpose, additional reference targets are arranged in the light scanner, for example, and the corresponding measurement signals are measured once cyclically.

In addition, all receiving elements of the light receiver can be tested, since all receiving elements can be exposed to the light from the reference light transmitter.

If an error occurs during testing with the reference light transmitter, this is recognized and the sensor can assume a safe state, after which, for example, no object detection signal is output or an error message is output, for example.

A plurality of receiving elements are provided. Each receiving element has an individual current / voltage converter with a connected sample & hold element (receiving converter). In the simplest case, these two elements consist of a capacitor with appropriate switches. If the charging switch is closed, the photodiode charges. With a reset switch, the capacitor can be drained before charging. All of these reception converter blocks are connected to a multiplexer, which allows the sequential readout of all reception converters. The output of the multiplexer is routed to an analog / digital converter. A downstream control and evaluation unit determines the light spot position from the signal distribution of the line.

The control and evaluation unit is also connected to the light transmitter and the reference light transmitter in order to control them.

According to the invention, a first mirror is arranged to direct the light beams of the reference light transmitter onto the first light receiver. As a result, the reference light transmitter and the light receiver can be arranged on one side and only a passive mirror is necessary as a deflecting element. The mirror can be integrated into the housing of the triangulation light scanner. The mirror can thus be a simple reflective surface of the housing.

According to the invention, the first mirror is a concave mirror. In the case of the first concave mirror, which is provided to deflect light beams between the reference light transmitter and the light receiver, the light is expanded onto the receiving elements so that all the receiving elements of the light receiver can be illuminated by the reference light transmitter.

In a further development of the invention, a further second light receiver is provided as a reference light receiver as a second receiving channel for safety-related self-testing.

The reference light receiver is arranged next to the light transmitter. The reference light receiver can be designed as a photodiode.

The reference light receiver enables the following self-tests to check the function of the triangulation light switch.

First, the power, in particular the laser power of the light transmitter, can be monitored in each measurement cycle via scattered light within the housing of the triangulation light scanner in the reference light receiver. Large deviations or a failure of the light transmitter can be detected in this way.

Second, the exact timing of the light transmitter can be monitored and any offsets that may occur can be corrected, e.g. B. in the case of temperature influences.

Thirdly, in the phases in which no light is emitted, the external light level can be measured at the reference light receiver. The corresponding measurement signal can be compared with the signal of the light receiver, whereby the sensitivity of the light receiver can be verified and, with optional other scaling, used to check the necessary signal-to-noise ratio in the actual measurement channel.

Additional measured values, which are generated on the light receiver and the reference light receiver, allow a safety assessment of the functionality.

A direct measurement of the external light level on the light receiver and possibly on the reference light receiver enables a good determination of the signal-to-noise ratio and enables a safety-related sensitivity of the system.

If an error occurs during testing with the reference light receiver, this is recognized and the sensor can assume a safe state, after which, for example, no more object detection signal is output or, for example, an error message is output.

In a further development of the invention, a second mirror is arranged in order to direct the light beams from the first light transmitter towards the reference light receiver to steer. As a result, the light transmitter and the reference light receiver can be arranged on one side and only a passive mirror is necessary as a deflecting element. The mirror can also be integrated into the housing of the triangulation light scanner. The mirror can thus be a simple reflective surface of the housing.

In a further development of the invention, the second mirror is a concave mirror. In the case of the second concave mirror, which is provided to deflect light between the light transmitter and the reference light receiver, the light is focused on the reference light receiver.

In a further development of the invention, the first light receiver and the reference light transmitter are arranged in a first tube, whereby the light receiver and the reference light transmitter are spatially and optically associated, but the light transmitter is arranged optically outside the first tube.

In a further development of the invention, the first light transmitter and the reference light receiver are arranged in a second tube, whereby the light transmitter and the reference light receiver are spatially and optically associated, but the light receiver is arranged optically outside the second tube.

In a further development of the invention, the first light transmitter and the reference light transmitter are activated alternately, so that mutual influencing is excluded.

In a further development of the invention, a front pane is arranged in front of the transmitting optics and in front of the receiving optics, the light from the reference light transmitter striking the front pane and reflected light reaching the light receiver and / or the light from the first light transmitter striking the front pane and reflected light striking the Reference light receiver hits.

As a result, a soiled front screen of the light scanner can be detected via a change in the light caused by backscattering from the dirt particles on the front screen.

In the following, the invention will also be explained with regard to further advantages and features with reference to the accompanying drawings using exemplary embodiments.

• 1 einen ersten schematisch dargestellten Triangulationslichttaster;
• 2 einen zweiten schematisch dargestellten Triangulationslichttaster.

The figures in the drawing show in:

• 1 a first schematically illustrated triangulation light scanner;
• 2 a second schematically illustrated triangulation light scanner.

In the following figures, identical parts are provided with identical reference symbols.

1 shows triangulation light scanner 1 with a first light transmitter 2 for emitting transmitted light into a detection zone 3 , being the light transmitter 2 a transmission optics 4th , in particular a lens is arranged in front of a first light receiver 6 with at least one receiver line with receiver elements 5 to receive light from the detection zone 3 , which of an object to be detected 7th is remitted, the receiving elements 5 generate respective received signals, one in the beam path between the detection zone 3 and first light receiver 6 arranged receiving optics 8th for generating a light spot from the reflected light on the first light receiver 6 , the position of the light spot on the first light receiver 6 in the triangulation direction depending on the distance of the object 7th results, and a control and evaluation unit 9 for generating a detection signal from the received signals on the basis of the position of the light spot on the first light receiver 6 , with another second light transmitter 11 as a reference light transmitter 12 is intended for safety-related self-testing.

The receiver line has, for example, 320, 640, 960, 1024 or some other number of receiving elements 5 on. The receiving elements 5 the receiver line or receiver row is, for example, approximately 12.7 µm x 600 µm. The receiving elements 5 are arranged in a row or a row.

Safety is ensured, for example, by a two-channel or two-channel diverse structure of the control and evaluation unit 9 for fault detection and functional testing guaranteed.

The control and evaluation unit 9 recognizes objects 7th in the detection zone 3 or protective field violations by an object 7th or a person and can send a safety-related shutdown signal or an object detection signal 25th output to stop a dangerous movement of a machine or a vehicle or a part of a machine or to brake the machine, the part of the machine or the vehicle. This can e.g. B. via safe switching signals z. B. OSSD signals (Output Safety Switching Device signals) take place.

The reference light transmitter 12 can be used to test the light receiver 6 next to the Light receiver 6 to get integrated. The reference light transmitter 12 is preferably close to the light receiver 6 attached and illuminates the light receiver 6 .

For testing the light receiver 6 optical light intensities with different intensity profiles or amplitudes can be used.

Via an adjustable signal level of the reference light transmitter 12 the dynamics of the light receiver 6 testing.

By measuring the signal height with different reference amplitudes, the dynamics and the sensitivity of the light receiver 6 be checked.

All receiving elements can 5 of the light receiver 6 be tested as all receiving elements 5 with the light of the reference light transmitter 12 can be applied.

For example, the receiver line is read out once in each measurement cycle without a transmission pulse from the light transmitter 2 to determine an offset by the ambient light. For example, in the event that the sensor is operated in the dark and the pixel-dependent offset or of the receiving elements 5 dependent offset is below a limit value, reference lighting is provided by the reference light transmitter 12 switched on. If the offset is still below the limit value, the sensor would be defective and go into the safe state.

There are a variety of receiving elements 5 intended. The receiving elements 5 are each connected to a current / voltage converter with a downstream sample & hold element 22nd or connected to a transimpedance amplifier with a downstream sample & hold element or to an integrator. The outputs of the current / voltage converter with downstream sample & hold element 22nd are to a multiplexer 21st connected. The output of the multiplexer 21st is to an analog / digital converter 23 guided.

The output of the analog / digital converter 23 becomes the control and evaluation unit 9 fed. The control and evaluation unit 9 continues with the first light transmitter 2 and the reference light transmitter 12 connected to control them.

According to 1 is a first mirror 13 arranged to the light beams of the reference light transmitter 12 at the first light receiver 6 to steer. This allows the reference light transmitter 12 and the light receiver 6 be placed on one side and it is just a passive mirror 13 necessary as a deflection element.

According to 1 is a second light receiver 14th as a reference light receiver 15th intended as a second receiving channel for safety-related self-testing.

The reference light receiver 15th is next to the first light transmitter 2 arranged. The reference light receiver 15th can be designed as a photodiode. The reference light receiver 15th enables a self-test to check the function of the triangulation light button 1 . The reference light receiver 15th can according to the dashed alternative representation in 1 also via a current / voltage converter 22nd and an analog / digital converter 23 to the control and evaluation unit 9 connected.

According to 1 is a second mirror 16 arranged to the light beams of the first light transmitter 2 on the reference light receiver 15th to steer.

According to 1 are the first mirror 13 and the second mirror 16 a concave mirror 17th . In the case of the second concave mirror 17th that is used to redirect light between light emitters 2 and reference light receiver 15th is provided, the light is on the reference light receiver 15th bundled.

In the case of the first concave mirror 17th which is used to deflect light beams between reference light transmitters 12 and light receivers 6 is provided, the light is on the receiving elements 5 expanded so that all receiving elements 5 of the light receiver 6 by the reference light transmitter 12 can be illuminated.

According to 1 are the first light receiver 6 and the reference light transmitter 12 in a first tube 18th arranged, whereby the light receiver 6 and the reference light transmitter 12 are spatially and optically associated, but the first light transmitter 2 optically outside the first tube 18th is arranged.

According to 1 are the first light transmitter 2 and the reference light receiver 15th in a second tube 19th arranged, whereby the light transmitter 2 and the reference light receiver 15th are spatially and optically associated, but the light receiver 6 optically outside the second tube 19th is arranged.

According to 1 are the first light transmitter 2 and the reference light transmitter 12 activated alternately, whereby mutual interference is excluded.

According to 1 is in front of the transmission optics 4th and in front of the receiving optics 8th a windshield 20th arranged, the light of the reference light transmitter 12 on the windshield 20th and reflected light hits the light receiver 6 arrives and / or that the light of the first light transmitter 2 on the windshield 20th and reflected light hits the reference light receiver 15th meets.

2 shows the triangulation light scanner 1 in a schematic representation for the formation of an object detection signal 25th . A transmit pulse generator 27 which part of the control and evaluation unit 9 is, controls the transmission levels 26th the first light transmitter 2 and the reference light transmitter 12 on. The light of the reference light receiver 15th reaches the receiving elements directly 5 . The light of the first light transmitter 2 goes directly to the reference light receiver 15th . The reference light receiver 15th and the receiving elements 5 are connected to the control and evaluation unit via electronic stages 9 connected which the object detection signal 25th generated. The light of the first light transmitter 2 reaches the transmission optics 4th into the detection zone 3 and from there over an object 7th on the receiving optics 8th and then on the receiving elements 5 .

List of reference symbols

1

Triangulation light scanner

2

first light transmitter

3

Detection zone

4th

Transmission optics

5

Receiving elements

6th

first light receiver

7th

object

8th

Receiving optics

9

Control and evaluation unit

11

second light transmitter

12

Reference light transmitter

13

first mirror

14th

second light receiver

15th

Reference light receiver

16

second mirror

17th

Concave mirror

18th

first tube

19th

second tube

20th

Windshield

21st

multiplexer

22nd

Current / voltage converter with sample & hold element

23

Analog / digital converter

25th

Object detection signal

26th

Broadcast level

27

Send pulse generator

Claims (8)

Triangulation light sensor (1) with a first light transmitter (2) for emitting transmitted light into a detection zone (3), the first light transmitter (2) being preceded by transmission optics (4), in particular a lens, at least one first light receiver (6) with at least a receiver line with receiving elements (5) for receiving light from the detection zone (3), which is remitted by an object (7) to be detected, the receiving elements (5) generating respective received signals, one in the beam path between the detection zone (3) and the first Receiving optics (8) arranged on the light receiver (6) for generating a light spot from the reflected light on the first light receiver (6), the position of the light spot on the first light receiver (6) in the triangulation direction depending on the distance of the object (7 ) and a control and evaluation unit (9) for generating a detection signal from the received signals on the basis of the Po position of the light spot on the first light receiver (6), with a further second light transmitter (11) being provided as a reference light transmitter (12) for safety-related self-testing, characterized in that a first mirror (13) is arranged to surround the light beams from the reference light transmitter (12) ) to direct the first light receiver (6), wherein the first mirror (13) is a concave mirror (17). Triangulation light button (1) Claim 1 , characterized in that a further second light receiver (14) is provided as a reference light receiver (15) as a second receiving channel for safety-related self-testing. Triangulation light button (1) Claim 2 , characterized in that a second mirror (16) is arranged to direct the light beams from the first light transmitter (2) onto the reference light receiver (15). Triangulation light button (1) Claim 3 , characterized in that the second mirror (16) is a concave mirror (17). Triangulation light scanner (1) according to at least one of the preceding claims, characterized in that the first light receiver (6) and the reference light transmitter (12) are arranged in a first tube (18). Triangulation light scanner (1) according to at least one of the preceding Claims 2 to 5 , characterized in that the first light transmitter (2) and the reference light receiver (15) are arranged in a second tube (19). Triangulation light scanner (1) according to at least one of the preceding claims, characterized in that the first light transmitter (2) and the reference light transmitter (12) are activated alternately. Triangulation light scanner (1) according to at least one of the preceding Claims 2 to 7th , characterized in that a front panel (20) is arranged in front of the transmitting optics (4) and in front of the receiving optics (8), the light from the reference light transmitter (12) striking the front panel (20) and the reflected light striking the first light receiver (6 ) and / or that the light from the first light transmitter (2) hits the front pane (20) and reflected light hits the reference light receiver (15).

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