Control interface for a machine-vision lighting device

Abstract

A machine-vision device including a camera system, with a camera and an integrated origin light source that is integrated into the camera system, and a lighting device with: control interface including: a plurality of light sensors each for capturing a respective origin light signal, and emitting a respective sensor signal, and an electronic unit for processing the sensor signal configured so as to transmit a respective control signal to a respective output of the processing electronic unit. The lighting device with one or more automatically controlled light sources that are external to the camera system, each connected to one respective output of the processing electronic unit by respective connection, so as to be controlled with the control signal delivered to the output. At least one light sensor is placed so as to directly capture the light emitted by one origin light source.

Claims

1. A machine-vision device comprising: a camera system comprising a camera and at least one origin light source that is integrated into the camera system; and a lighting device comprising: a control interface comprising: a plurality of light sensors each for capturing a respective origin light signal, and emitting a respective sensor signal in response to the capture of said respective origin light signal; an electronic unit for processing said respective sensor signal, configured so as to transmit, as a consequence of said processing, a respective control signal to at least one respective output of the processing electronic unit, one or more automatically controlled light sources that are external to said camera system, each connected to one respective output of the processing electronic unit by respective connecting means, so as to be controlled with the control signal delivered to said output, at least one light sensor being placed so as to directly capture the light emitted by one origin light source, wherein the light sensors are configured to detect only a light spectrum of a width smaller than 100 nm.

2. The machine-vision device as claimed in claim 1, wherein the electronic unit is configured so as to identify an automatically controlled light source to be controlled with said control signal and so as to generate said control signal depending on a light intensity and/or a color to be emitted by said automatically controlled light source.

3. The machine-vision device as claimed in claim 2, wherein the electronic unit is configured so that the magnitude of said control signal is proportional to the intensity of said origin light signal.

4. The machine-vision device as claimed in claim 1, wherein the electronic unit is configured so as to drive the automatically controlled light sources depending on the timing of the sensor signals received by the electronic unit, and/or on the origin of the sensor signals received by the electronic unit, and/or on the color of the origin light signals received by said sensors.

5. The machine-vision device as claimed in claim 1, wherein the light sensors are distributed over a sensor holder having a sensor-holder aperture of radius larger than 12 mm and smaller than 30 mm.

6. The machine-vision device as claimed in claim 1, wherein the one or more automatically controlled light sources are each a light-emitting diode or a group of light-emitting diodes.

7. The machine-vision device as claimed in claim 1, wherein the automatically controlled light sources are fastened to an automatically-controlled-light-source holder that is equipped with an automatically-controlled-light-source-holder aperture, and the light sensors are fastened to a sensor holder having a sensor-holder aperture that is coaxial with said automatically-controlled-light-source-holder aperture.

8. The machine-vision device as claimed in claim 1, wherein the one or more automatically controlled light sources are configured to emit flashes of a duration shorter than 10 ms and/or a light spectrum of a width smaller than 100 nm.

9. The machine-vision device as claimed in claim 1, wherein the electronic unit is configured so as to drive the automatically controlled light sources depending on the timing of the sensor signals received by the electronic unit, and/or on the origin of the sensor signals received by the electronic unit, and/or on the color of the origin light signals received by said light sensors.

10. The machine-vision device as claimed in claim 1, wherein the light sensors are fastened to a sensor holder with a density of at least one light sensor per 9 mm.sup.2 and of at most one light sensor per mm.sup.2.

11. The machine-vision device as claimed in claim 1, wherein each light sensor is placed so as to directly capture the light emitted by a single respective origin light source or by a single group of origin light sources that emit synchronously.

12. The machine-vision device as claimed in claim 1, wherein the camera system is independent of the lighting device.

13. The machine-vision device as claimed in claim 1, including a plurality of light sensors and a plurality of origin light sources, the light sensors being oriented toward the origin light sources.

14. The machine-vision device as claimed in claim 1, wherein the light sensors are provided only facing origin light sources.

15. A device for conveying items, comprising at least: an item-conveying track, and a machine-vision device as claimed in any one of the preceding claims, the automatically controlled light sources being suitable for illuminating at least one segment of the item-conveying track.

16. The machine-vision as claimed in claim 1, wherein said light spectrum is centered on a discrete wavelength chosen among 470 nm, 525 nm, 635 nm, 660 nm, 850 nm and 880 nm.

17. The machine-vision as claimed in claim 1, wherein at least one output is an electrical terminal and the means of connection are electric cables.

18. The machine-vision as claimed in claim 1, wherein at least one of said light sensors is configured so as to detect only a light spectrum of a width smaller than 50 nm.

19. A method for controlling lighting for a machine-vision device, comprising the steps of: i) emitting origin light signals; ii) capturing the emitted origin light signals; iii) processing the captured origin light signals in order to deduce therefrom the way in which to control one or more automatically controlled light sources; iv) controlling one or more automatically controlled light sources in the way deduced in step iii).

20. A method as claimed in claim 19, wherein said method comprises the following steps: a) determine a light intensity and/or a color for the light to be produced; b) identify one or several automatically controlled light sources to command, depending on its or their position and/or on the captured origin light signals in order to obtain the light intensity and/or color for the light to be produced; c) command one or several automatically controlled light sources, depending on its or theirs position and/or on the captured origin light signals in order to obtain the light intensity and/or color for the light to be produced.

21. A method as claimed in claim 19, wherein said method comprises the step of commanding a respective automatically controlled light source depending on a respective light signal from a respective origin light source received by a respective sensor.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Other features and advantages of the invention will become apparent on reading the following detailed description, which description makes reference to the appended drawings, in which:

(2) FIG. 1 schematically shows a machine-vision device;

(3) FIG. 2 illustrates a camera system able to be implemented in the machine-vision device of FIG. 1;

(4) FIG. 3 schematically shows a control interface for a lighting device able to be controlled using the camera system of FIG. 2;

(5) FIG. 4 illustrates a camera system and a control interface able to be implemented in the machine-vision device of FIG. 1;

(6) FIG. 5 illustrates the control of LEDs using the control interface of FIG. 3;

(7) FIG. 6 schematically shows a variant lighting device for a machine-vision device;

(8) FIG. 7 schematically shows a device for conveying items;

(9) FIG. 8 shows a flowchart of an example of a method for conveying items; and

(10) FIG. 9 schematically shows timing diagrams showing the intensity i of the light emitted by an origin light source (top graph) and by the corresponding automatically controlled light source (bottom graph), as a function of time t.

(11) In the present description, elements that are identical or that perform identical functions have been given the same reference signs. For the sake of conciseness of the description, these elements are not described for each figure.

DETAILED DESCRIPTION

(12) FIG. 1 shows an example of a machine-vision device 10. This device 10 comprises a lighting device 12, for illuminating a zone of interest, for example a segment of a conveyor belt. The lighting device 12 here comprises four automatically-controlled-light-source holders 14 (14a-14d) to each of which five respective automatically controlled light sources 16 (16a-16d), in the present case LEDs or groups of LEDs that operate synchronously, are fastened.

(13) The machine-vision device 10 also comprises a camera system 18 that is independent of the lighting device 12, in order to capture an image of the zone of interest illuminated by the lighting device 12. The camera system is for example connected to a unit for processing the images captured by the camera, in order to identify items located in the illuminated zone of interest and to detect items that do not meet a defined criterion.

(14) The camera system 18, which is shown in more detail in FIGS. 2 and 4, comprises an objective 20 that is composed of an optical lens or of a plurality of optical lenses, which objective is associated with an optical sensor 22 for capturing the image of the zone of interest illuminated by the automatically controlled light sources 16. The optical sensor 22 is connected to an electronic board 24, in particular in order to process information originating from the optical sensor 22 and to deduce therefrom a digitized image of the zone of interest.

(15) The camera system 18 further comprises a plurality of origin light sources 26, which are controlled by the electronic board 24. These origin light sources 26 may be of different colors and/or oriented in different emission directions. Often, the origin light sources 26 do not allow satisfactory illumination of the zone of interest to be achieved, i.e. an illumination that allows the machine-vision device 10 to identify and, for example, to sort the items present in the zone of interest.

(16) For this reason, the machine-vision device 10 further includes an interface 28 for controlling the lighting device 12, which interface is shown in more detail in FIGS. 3 and 4. This interface 28 is here formed from a sensor holder 30 to one face of which light sensors 32 are fastened. The sensor holder 30 is here planar, of substantially rectangular shape, and has a circular aperture 34 in its center. The circular aperture 34 allows the camera system 18 to capture images of the zone of interest illuminated by the lighting device 22, through the sensor holder 30. The dimensions of the holder 30 are for example: a length larger than 50 mm and/or smaller than 90 mm, and preferably equal to 70 mm 70 mm; a width larger than 30 mm and/or smaller than 60 mm, and preferably equal to 45 mm.

(17) The circular aperture 34 is for example of radius larger than 12 mm and/or smaller than 30 mm. The interface is for example placed at a distance smaller than 50 mm from the camera system 18, for example at a distance of 20 mm.

(18) The light sensors 32, which are preferably oriented toward the origin light sources 26, are here uniformly distributed. The density of light sensors may in particular be higher than one sensor per 9 mm.sup.2 and/or lower than one light sensor per mm.sup.2. It may preferably have a relatively low density of light sensors so that the light emitted by one origin light source 26 is captured substantially only by one light sensor 32. Specifically, this allows, as will be seen below, the automatically controlled light sources 16 that illuminate the zone of interest to be controlled independently. However, the higher the number of light sensors 32, the greater the number and complexity of possible controls. In one embodiment, light sensors 32 are provided only facing origin light sources 26, in an amount of, for example, one light sensor 32 per origin light source 26.

(19) The light sensors 32 are for example of square shape, and of 1 mm side length.

(20) As schematically illustrated by FIG. 5, the light sensors 32 are connected to an electronic unit 36 32. The processing electronic unit 36 processes the signals S32 delivered as output by the light sensors 32 and converts them into control signals S.sub.36 for the automatically controlled light sources 16 of the lighting device 12. To do this, the interface 28 includes means 38 for connecting outputs 40 of the processing electronic unit 36 to one or more automatically controlled light sources 16 of the lighting device 12, allowing said automatically controlled light sources 16 to be controlled depending on the origin light signals S.sub.26 emitted by the origin light sources 26 of the camera system. The origin light signals may thus indirectly control the automatically controlled light sources 16 of the lighting device 12.

(21) Preferably, the electronic unit 36 determines, depending on the signals S32 received from the light sensors, the identification of one or more automatically controlled light sources 16 to be controlled and, for each of these automatically controlled light sources 16, a light intensity and/or a color for the light to be produced.

(22) Preferably, the automatically controlled light sources 16 are controlled to emit intermittently, and preferably to emit flashes of a duration shorter than 10 ms, preferably shorter than 3 ms and preferentially shorter than 200 s. Advantageously, intermittent illumination avoids the creation of blur in the images during the movement of the parts.

(23) With each output 40 is associated one automatically controlled light source, preferably one or more LEDs, and one control signal for said automatically controlled light source.

(24) The outputs 40 may be single electrical terminals, and the connecting means 38 may be electrical cables. Preferably, the electronic unit 36 delivers, to each output, a supply current for one automatically controlled light source 16 of the lighting device 12.

(25) Advantageously, the processing electronic unit 36 is divided into modules, in particular independent modules, which each control, preferably depending on a respective light emission received from a respective origin light source 26, a respective automatically controlled light source 16 (in particular an LED or a group of LEDs) of the lighting device 12, independently. Thus, for example, one light sensor 32, or a group of light sensors 32, may be functionally connected to such an independent module, in order to control one LED or one group of LEDs of the lighting device 12. Each module may advantageously consist of a field programmable gate array (FPGA), which ensures a reduced processing time.

(26) Preferably, the processing electronic unit includes more than 3, more than 7, more than 15, or more than 127 outputs 40.

(27) FIG. 6 illustrates a variant lighting device 52. The latter differs from the lighting device 12 of FIGS. 3 and 4 essentially in that it includes a single light-source holder 14 of hemispherical shape. An aperture 54, which is preferably circular, is provided in the holder 14 at its apex, so as to be placed facing the aperture 34 of the sensor holder 30 of the interface 28. The apertures 34 and 54 are coaxial, and of axis A.

(28) Automatically controlled light sources 16a are preferably placed in a ring around the aperture 54 of the holder 14. Furthermore, automatically controlled light sources 16b and 16c are preferably placed in a ring on the base 56 of the holder 14. Automatically controlled light sources 16b may be oriented radially toward the axis A of the hemispherical holder, parallel to the axis A (16c) and/or toward the apex of the holder 14. A hemispherical holder 14 generally allows more uniform illumination of the zones of interest of a machine-vision device than is possible with a lighting device the holder 14 of which is planar.

(29) FIG. 7 schematically illustrates a device 100 for conveying industrial items 112. This conveying device 100 comprises a conveying track 114 that conveys the items 112 in the direction D. The conveying track 114 is for example a conveyor belt. The conveying device 100 comprises a machine-vision device 116, the lighting device 12, 52 of which may in particular be such as described above with reference to FIGS. 1 to 6. The lighting device 12, 52 illuminates a zone of interest 118 formed by a section of the conveying track 114, through which the items 112 pass.

(30) The machine-vision device is known per se. It may in particular include a board (also known as a frame grabber) for interfacing between a computer and the camera in order to digitize the images if the camera is not suitable for digitizing the captured images directly. The camera may be directly connected to a communication bus (TCP-IP, USB, IEEE-1394 etc.). A processing unit, often a microcomputer or a system with an integrated processor (such as a DSP), makes it possible to determine, using image-processing software, items present in the captured image that do not correspond to the sorting criteria. A synchronizing sensor, which is often optical or magnetic, or encoders, may also be provided, in order to trigger the camera when an item passes into its field of view. A system of digital inputs/outputs, or a standard communication system, for example a network connection or an RS-232 connection or most often an RS-485 connection for long distances, may be provided in order to transmit the data between the various elements of the machine-vision device.

(31) The conveying device 100 further comprises a sorting unit 120 for removing from the conveying track 114 the selected items 112, for example items the inspection of which by the machine-vision device has revealed a defect. In the present case, this sorting unit consists of a movable arm 120 for removing items 112 from the conveying track 114.

(32) FIG. 8 illustrates an industrial conveying method 200 able to be implemented, for example, in an industrial conveying device such as illustrated in FIG. 7.

(33) In this conveying method 200, a step 202 of conveying items to a zone of interest 118 is first carried out.

(34) Origin light signals S.sub.26 are emitted, in a step 204, by origin light sources 26 of the camera system 18.

(35) These origin light signals are captured, in a step 206, by the light sensors 32 of the interface 28.

(36) In the following step 208, the signals emitted by the light sensors 32 in response to the reception of these origin light signals S.sub.26 are processed in order to deduce therefrom control signals S.sub.36 for one or more automatically controlled light sources 16 of the lighting device 12. This control is carried out according to a protocol, depending on the emitted color and on the position of the one or more origin light sources 26 in question.

(37) For example, a camera comprising 4 groups of integrated multi-colored LEDs able to emit red, green or blue light allows at least 2{circumflex over ()}32{circumflex over ()}4=816=128 different illuminations to be produced.

(38) It is thus possible to drive, using the interface according to the invention placed in front of a camera 18 comprising such integrated lights, at least 128 automatically controlled light sources, or at least 128 combinations of sectors and of different colors. The automatically controlled light sources preferably belong to an external set of lights (i.e. a set of lights not included in the camera system 18). It is thus possible to produce complex lighting sequences as though the automatically controlled light sources were driven directly by the software of the camera system 18.

(39) In the step 210, the zone of interest 118 is illuminated by the lighting device 12, 52 in the way deduced in step 208.

(40) As shown in FIG. 9, in one embodiment the timing diagram of the power of the light emitted by one origin light source 26 (top graph) is used to control an automatically controlled light source 16 so that it emits with the same timing diagram (bottom graph). The temporal offset between the two curves may be smaller than 50 s, preferably smaller than 10 s, and preferably smaller than 5 s.

(41) Next there follows a step 212 of capturing an image of the zone of interest 118 with the camera system 18, this image then being interpreted, in a way known per se, in order to deduce therefrom information on the conveyed items passing through the zone of interest 118. Items that do not meet a defined criterion may then be removed (sorting step 214).

(42) The method 200 may then be reiterated.

(43) As should be clear by now, the invention provides a simple and flexible solution allowing lighting to be optimally adapted.

(44) The invention is not limited to only the examples that were described above and those skilled in the art will be able to envision many variants thereof.

(45) Thus, the camera system used may include one or more digital or analog, monochrome or color, cameras equipped with an objective suitable for the conditions of the image capture, in particular for the distance and size of the zone to be imaged and/or for the conveyed items to be identified in this image.

(46) The applications are not limited to an industrial conveying device.