CONTRAST SENSOR

Abstract

A contrast sensor for evaluating identification markings and a method of evaluating identification markings on detecting objects using a contrast sensor, having at least one light transmitter and at least one light receiver, with the light receiver having a single photodiode; having a control and evaluation unit for evaluating the light receiver signal of the light receiver, and having an output for a sensor signal that is formed by the control and evaluation unit on the basis of the light receiver signal, wherein the identification marking has lettering or a marking; an elongate illumination field is projected by the light transmitter onto a region of the identification marking narrow in the direction of movement; and the control and evaluation unit compares a reception signal sequence having a plurality of contrast transitions with a stored reception signal sequence and outputs the sensor signal in dependence on the comparison.

Claims

1. A contrast sensor for evaluating identification markings on detection objects, the contrast sensor comprising: at least one light transmitter and at least one light receiver, wherein the light receiver has a single photodiode; a control and evaluation unit for evaluating the light receiver signal of the light receiver; and an output for a sensor signal that is formed by the control and evaluation unit on the basis of the light receiver signal, wherein the detection object has lettering or a marking as the identification marking; wherein an illumination field is projected by the light transmitter onto a region of the identification marking narrow in the direction of movement; and wherein the control and evaluation unit is configured to compare a reception signal sequence having a plurality of contrast transitions with a stored reception signal sequence and the sensor signal can be output in dependence on the comparison result.

2. The contrast sensor in accordance with claim 1, wherein at least two light transmitters are arranged in a row so that a geometry of the illumination field can be adapted by an engaging or disengaging of light transmitters.

3. The contrast sensor in accordance with claim 2, wherein at least three light transmitters are arranged in a row so that a geometry of the illumination field can be adapted by an engaging or disengaging of light transmitters.

4. The contrast sensor in accordance with claim 1, wherein a width of the illumination field has a structural size that at most corresponds to the structural size of the identification marking and at least corresponds to a dot or line thickness of the identification marking.

5. The contrast sensor in accordance with claim 1, wherein a detection accuracy, that is the degree of agreement between the reception signal sequence and a stored reception signal sequence, can be set.

6. The contrast sensor in accordance with claim 1, wherein a background signal is stored.

7. The contrast sensor in accordance with claim 1, wherein the control and evaluation unit is configured to determine at least one start trigger from the identification marking, with the reception signal sequence being able to be evaluated for a constant time period from the start trigger onward.

8. The contrast sensor in accordance with claim 1, wherein the control and evaluation unit is configured to determine at least one start trigger from an input signal, with the reception signal sequence being evaluated for a constant time period from the start trigger onward.

9. The contrast sensor in accordance with claim 1, wherein the control and evaluation unit is configured to determine at least one start trigger and one end trigger from an input signal, with the reception signal sequence between sequential start and end triggers being evaluated.

10. A method of evaluating identification markings of detection objects, wherein at least one light transmitter and at least one light receiver; a control and evaluation unit for evaluating the light receiver signal of the light receiver, and an output for a sensor signal that is formed by the control and evaluation unit on the basis of the light receiver signal are provided, wherein the identification marking has lettering or a marking; an elongate illumination field is projected by the light transmitter onto a region of the identification marking narrow in the direction of movement; and wherein the control and evaluation unit compares a reception signal sequence having a plurality of contrast transitions with a stored reception signal sequence and outputs the sensor signal in dependence on the comparison.

11. The method in accordance with claim 10, wherein the geometry of the illumination field can be adapted by the engaging and disengaging of light transmitters.

12. The method in accordance with claim 10, wherein the detection accuracy, that is the degree of agreement between the reception signal sequence and a stored reception signal sequence, can be set.

13. The method in accordance with claim 10, wherein a background signal is stored.

14. The method in accordance with claim 10, wherein at least one start trigger is determined from the identification marking, with the reception signal sequence being evaluated for a constant time period from the start trigger onward.

15. The method in accordance with claim 10, wherein at least one start trigger is determined from an input signal, with the reception signal sequence being evaluated for a constant time period from the start trigger onward.

16. The method in accordance with claim 10, wherein at least one start trigger and one end trigger is determined from an input signal, with the reception signal sequence between successive start and end triggers being evaluated.

Description

[0062] The invention will also be explained in the following with respect to further advantages and features with reference to the enclosed drawing and to embodiments. The Figures of the drawing show in:

[0063] FIG. 1 a contrast sensor;

[0064] FIG. 2 to FIG. 5 a respective identification marking on an object or article;

[0065] FIG. 6 an identification marking during teaching and during a detection;

[0066] FIG. 8 a first threshold and a contrast signal; and

[0067] FIG. 9 a second threshold and a contrast signal.

[0068] FIG. 1 shows a contrast sensor 1 for evaluating an identification marking 2 of detection objects 7 having at least one light transmitter 3 and at least one light receiver 4, wherein the light receiver 4 has a single photodiode; having a control and evaluation unit 5 for evaluating the light receiver signal of the light receiver 4; and having an output 6 for a sensor signal that is formed by the control and evaluation unit 5 on the basis of the light receiver signal, wherein the identification marking has lettering or a mark, an elongate illumination field 8 is projected by the at least one light transmitter 3 onto at least a part of the identification marking 2 and the control and evaluation unit 5 is configured to compare reception signal sequences having a plurality of contrast transitions with a stored reception signal sequence and the sensor signal can be output in dependence on the comparison.

[0069] The contrast sensor 1 is arranged, for example, at a printing machine, at a packaging machine, at a processing machine for products, etc.

[0070] The light transmitter 3 is, for example, formed by one or more light emitting diodes or laser diodes. The light receiver 4 is, for example, formed by one or more photodiodes. The contrast sensor 1 can, for example, be configured as a light sensor, according to which the light transmitter 3 and the light receiver 4 are arranged in a common housing in which the control and evaluation unit 5 is also arranged.

[0071] FIG. 2 to FIG. 5 show different identification markings 2 on different objects or detection objects 7.

[0072] FIG. 2 shows an identification marking 2 with a one-line data indication and a time that is, for example, printed on a beverage packaging with an image as the background.

[0073] FIG. 3 shows an identification marking 2 with two-line lettering, for example a data indication in a first line and additional lettering in a second line with a serial number, for example. Image elements, for example a dcor of a yoghurt lid are likewise located in the background.

[0074] FIG. 4 shows a cap of a bottle having a two-dimensional dot code or a data matrix code as the identification marking 2. The identification marking 2 is in this respect outwardly curved and is arranged on a partly shiny background.

[0075] FIG. 5 in turn shows an identification marking 2 with two-line lettering, for example a data indication in a first line and additional lettering in a second line with a serial number, for example. The identification marking 2 is in this respect inwardly curved and is located, for example, at a base of an aluminum beverage can so that the background is partly shiny.

[0076] FIG. 6 shows a first identification marking 2 without lettering to be scanned that is used to teach a background in a first teaching step. The region 12 is continuously scanned by the illumination field during the detection window 13.

[0077] FIG. 6 further shows a second Figure identification marking 2 having lettering to be scanned that is used to teach the lettering together with the background in a second teaching step. The region 12 is in turn continuously illuminated by the illumination field and is scanned by the light receiver and the control and evaluation unit during the detection window.

[0078] FIG. 6 further shows the second identification marking 2 with the lettering to be scanned to detect the lettering of the identification marking and to analyze whether the identification marking is present or not.

[0079] In FIG. 6, a first input signal ET and a second input signal WND, standing for window, is shown. The first input signal ET stands for teaching and indicates that the sensor should learn the detected identification marking 2. The second input signal WND indicates when the detection window 13 should be activated and when not. An output signal A is further indicated that indicates a validly detected identification marking 2, with the output signal being output, for example, within 10 ms after a detection has taken place.

[0080] FIG. 7 shows a further identification marking 2 having lettering and a background, with the signals detected by the contrast sensor being shown in FIG. 8 and FIG. 9.

[0081] FIG. 8 shows a scanning signal or contrast signal or light receiver signal 16 that is compared with a first threshold 14. The first threshold 14 is a threshold automatically tracked by the control and evaluation unit. A result signal is produced from this and has the recognized features as a binary signal or as the reception signal sequence 9.

[0082] FIG. 9 shows a scanning signal or contrast signal or light receiver signal 16 that is compared with a second, more sensitive threshold 15. The second threshold 15 is likewise a threshold automatically tracked by the control and evaluation unit. A result signal is produced from this that has the recognized features as a binary signal or as the reception signal sequence 9, with more features having been recognized than in the example in accordance with FIG. 8.

TABLE-US-00001 Reference numerals: 1 contrast sensor 2 identification marking 3 light transmitter 4 light receiver 5 control and evaluation unit 6 output 7 detection object 8 elongate illumination field 9 reception signal sequence 10 contrast transitions 11 memory 12 region 13 detection window 14 first threshold 15 second threshold 16 light reception signal