Diode light source for a line scan camera

Important NOTE:

The claims contained in this utility model were only submitted by the applicant after the search report had been served (Section 19 (4) GMG) and were therefore not the basis for the search report. The version of the claims on which the search report is based can be inspected at the Austrian Patent Office during office hours.

AT 004 889 Ul

The invention relates to a device according to the

Preamble of claim 1.

In devices of this type for capturing and recognizing objects, for example in sorting systems, cameras, mostly line cameras, are used, past which objects of a material flow are passed and are recognized and assigned accordingly by the cameras. This recognition and assignment can relate to various properties of the objects, such as material composition, color, size or the like. The information obtained in this way is then used to control subsequent process sequences or to control a separating device that sorts the objects into different fractions.

See-through is very often used for transparent or translucent goods. The light source shines through the material to be analyzed, which enables more reliable detection, for example of the individual fractions of a material to be sorted. Fluorescent tubes are usually used as the light source for the transillumination, which extend completely or partially over the width of the relevant system section, for example the chute of a sorting system. Uniform light is thus generated over a restricted area that is captured by a line camera, which ensures constant lighting conditions within the area captured by the camera.

The disadvantage of using a fluorescent tube is that a decreasing light intensity can be determined at both ends of a fluorescent tube, so that only a limited area of ​​the fluorescent tubes can be used. This means that lighting devices of this type have to be used

AT 004 889 Ul build much wider than the detection area of ​​the line scan cameras. If, for example, several fluorescent tubes are used for use with several line cameras, the result is a total width of the relevant system section which is significantly larger than the detection area of ​​the cameras. Even if, for example, a long fluorescent tube is used as a light source for the areas of several line cameras, there are still areas at the two ends of the fluorescent tube that can no longer be used by the cameras for reliable detection. the

The lighting device must be much wider than the relevant section of the system. Another disadvantage arises from the fact that the brightness of the light source can only be controlled, so that on the individual via the

Line scan cameras distributed across the plant section cannot be influenced.

changed as a whole or any differences

AT 001 2 64 Ul proposes a measuring system for the contactless scanning of the surface of glass plates with the help of infrared LEDs (“Light Emitting Diodes). IR photodiodes or transistors are used as receiver elements. However, due to the preferred use of light in the infrared spectral range, no optical devices are provided between the infrared LEDs and the material flow or the material flow and the receiver elements.

Infrared light is also used in US Pat. No. 3,859,538, so that no optical devices whatsoever are provided for homogenizing the lighting. Otherwise, this document relates to an electronic circuit for amplifying the signal of photoelectronic components.

AT 004 889 Ul

In US 5 365 084 a lighting system for high speed video inspections is disclosed. LEDs arranged in rows with different wavelengths of the emitted light are used. Although this document suggests improvements in signal processing, it does not contain any information on improving the illumination with the help of optical measures.

DE 24 26 866 B2 also shows LEDs arranged in rows, but otherwise relates to the electronic one

Here, too, there are intensity minima in the between each two LEDs, which sometimes

Can cause problems with the precise identification of elements of the material flow.

Data evaluation. Planes of symmetry

The aim of the invention is to eliminate these disadvantages and to develop a compact detection unit with versatile setting and control options, which ensures uniform lighting of the relevant system section. According to the invention, this is achieved by the characterizing features of claim 1.

Claim 1 relates to the use of several diodes, which are arranged in the form of one or more rows next to one another over the entire width of a system section for the detection of objects, such as the chute of a sorting system, or parts thereof. These diodes can be regulated separately from one another so that the brightness or the frequency of the emitted light can be varied in sections along the diodes arranged in rows. Depending on requirements, however, several diodes can also be subject to a common control.

AT 004 889 Ul

Since the diodes represent approximately point-like light sources, it is crucial, however, for uniform illumination of the relevant section of the system to use an optical device that makes the light emitted by the diodes appear diffuse. This enables uniform illumination of the areas captured by the line scan cameras. The optical device described in claim 1 achieves this equalization of the light emitted by the diodes and thus ensures reliable detection of the items to be sorted and their detection by cameras.

In systems for recognizing and capturing objects in a material flow, such as items to be sorted, it is in principle possible either to irradiate the material flow with light and thus ensure the brightness required for detection by cameras, or to illuminate it with light, which is particularly important see-through or transparent objects is advantageous.

Claim 2 describes a camera used in the lighting device and preferably the

Claim 3

Arrangement of the invention a favorable

Embodiment of the diodes used.

The invention will now be explained in more detail with reference to the accompanying drawings. Figure 1 shows the relative arrangement of cameras, diodes, material flow and the optical device, consisting of the two diffusers and a lens. FIG. 2 shows an overview sketch to illustrate the use of the invention, for example in connection with a downstream sorting device.

AT 004 889 Ul

Figure 1 shows schematically the lighting device according to the invention for the detection area 1 of a line camera 2. Along the entire width of a system section 3, e.g. the chute of a sorting system, for detecting objects of a material flow, line cameras are arranged next to one another in such a way that the detection areas 1 of adjacent cameras 2 overlap in the plane of the system section 3. The system section 3 is made of transparent or transparent material.

Diodes 4, preferably white light diodes, are in the form of one or more rows across the whole

broad

Plant section 3 or partially arranged thereof, des

These

Diodes 4 serve as light sources for the illustrated embodiment as transillumination through transparent or translucent objects 5 and are therefore arranged in such a way that they are located behind the system section 3 as seen from the line scan cameras. The diodes 4 can be controlled individually by a control device 9. It is thus possible to regulate the amount of emitted light individually for each diode along the width of the system section in order to be able to adapt the brightness to the requirements in sections.

An optical unit, consisting of a diode-side diffuser 6, an object-side diffuser 7 and an intermediate lens 8, converts the light emitted by the approximately punctiform diode light sources into diffuse light. The lens 8 serves to control the light intensity of the light emitted by the diode-side diffuser, but also to make it more uniform. The material and dimensions of the diffusers and the lens are selected so that the most uniform possible illumination of the detection area 1

AT 004 889 Ul is guaranteed and depends on the respective application, so for example on the optical density of the objects 5 and the

Plant section 3, distance between camera 2 and

Plant section 3 as well as between plant section 3 and

Diodes 4 and much more.

During operation, transparent or transparent objects 5 of a material flow, e.g. items to be sorted, run through the system and hit the system section 3 captured by line cameras 2. An object 5 is illuminated by diffuse light that is emitted by the lighting device according to the invention. The modifications of the light emitted by the diodes caused by the passing of the object 5 are recorded by the line cameras 2, with which information about various properties of the object 5, such as material composition, color, size or the like, can be obtained. A signal controlled by the detection process of this camera finally regulates a downstream process step or a downstream separating device 10.

Since, in systems with line cameras 2, several such cameras are usually arranged across the width of the sorting system section 3, each of which observes a section of the width and controls downstream separating devices 10, it is easily possible with the lighting arrangement according to the invention to adapt them section by section to the conditions of the line camera 2. This is not possible with a fluorescent tube that extends over the entire width of the system section. The invention thus represents a compact detection unit with versatile setting and control options.