DE102010032469A1 - Code reader for reading codes in examination region on surface of e.g. silicon wafer, has image evaluation computer obtaining captured images from electronic controller via interface and including unit for decoding recorded codes - Google Patents

Abstract

The reader (1) has illumination devices (4, 4', 4'') including radiating light sources (6, 6'') emitting light in two incompletely overlapping wavelength ranges between UV and near infrared lights (NIR). An electronic controller automatically successively adjusts a preset selection of combinations of recording optical paths, illumination optical paths and the wavelength ranges of the sources, and records associated images. An image evaluation computer obtains captured images from the controller via an interface and includes a unit for decoding recorded codes. An independent claim is also included for a method for using a device for reading codes in an examination region on a surface of a solar cell wafer.

Description

In order to be able to reliably identify solar cells, which are preferably produced using silicon substrates, throughout their production chain, it is known to apply a code, preferably an optically readable 2D code, to the solar cell.

The application of this coding takes place on the raw wafer of monocrystalline or polycrystalline silicon and can by a common marking method, for. B. laser marking done. The raw wafer is exposed to various surface-altering processes in the solar cell manufacturing process. These are, for example, etching, structuring and coating processes. At the end of the process chain is then still the metallization, d. h., Fine tracks are applied to the surface, which can partially cover or interfere with the coding. In solar cell production, a distinction is made between monocrystalline and multicrystalline cells. The process steps of these cells differ in part; In particular, in the case of monocrystalline cells, a microstructuring of the surface is carried out (for example, from juxtaposed micropyramides). All these factors require in the code reading systems a special adaptation of the illumination and image recording device to the respective process step in order to achieve an image contrast of the codes to the background and thus make the codes visible and readable.

Optical reading systems for examining properties of a solar cell and / or for reading an applied code and / or defects on a substrate are known from the patent literature.

From the DE 10 2009 010 369 A1 For example, an image pickup device and a method for optical testing of solar cells are known. In this case, a bias voltage directed in the reverse direction is applied to the solar cell and a thermal image and an image in the visible wavelength range are recorded by the solar cell and superimposed for purposes of error localization using an image processing device.

From the German patent application DE 10 2008 90 43 750 A1 is a method for marking and coding a solar cell with optically readable encodings known.

From the German patent DE3540288C2 An optical control device is known for checking solder joints on a printed circuit, in which a lighting device with a plurality of illumination sources on a hemisphere and a camera with an optical axis perpendicular to the examination plane is provided, wherein the illumination sources selectively on and off sequentially can be recorded and evaluated a variety of images with different lighting devices.

From the German patent DE10142165B4 a device is known for the optical examination of a surface, in which a lighting device is provided with at least one illuminating unit, which can be varied with respect to the illumination intensity, the illumination direction and / or the spectral composition, and a camera with an optical axis perpendicular to the examination plane.

From the German patent DE10162270B4 For example, an optical sensor device with two illumination units is known which illuminates an examination object at different angles of incidence.

From the German patent application DE102005005536A1 is an optical code reader with an integrated light source is known in which an examination surface can be illuminated at different illumination angles from the European patent EP0685140B1 a method and a device for continuous diffuse illumination of an examination area is known in which images of the diffusely illuminated examination area are taken with a plurality of cameras at different angles.

From the US patent US6105869A An optical code reader is known in which an examination area is illuminated at different angles of incidence.

From the PCT application WO99049347A1 For example, an illumination device for an optical examination device is known, in which an examination region is illuminated at different angles of incidence.

According to the state of the art, a reading system is selected according to the reading situation or individually adapted to it. This adaptation of the reading system to the respective reading situation may include a change in the illumination geometry or the spectral properties of the illumination, or both. Under illumination geometry, inter alia, the angle of incidence of the light source to the surface of the wafer or the solar cell, whether it is a collimated or diffuse emitting light source, and to understand the spatial distribution of the beam sources. Furthermore, it must be distinguished whether it is coherent or incoherent light sources. The spectral properties include both the wavelength of the light source and the bandwidth. There are light sources in the UV to infrared range in question. The adaptation of the reading system to the respective reading situation may include, in addition to the adjustments of the lighting, an adaptation of the imaging beam path. Here is an example of the observation angle to the surface and the characteristic of the beam path, z. As telecentric, divergent or convergent to call. According to the state of the art, the reading situation is evaluated according to the process state of the wafer or solar cell (examples: mono- or multicrystalline wafers, raw wafers, etched, SiN-coated, metallized, etc.) and the reading system meets the requirements for illumination, objective, optical path and Arrangement adapted individually.

The object of the invention is to provide a device which can be used universally for reading codes on solar cell wafers in all stages of the production process and a method which automatically or manually controls all lighting and lighting required to produce a decodable image of the examination region containing the code Imaging arrangements realized.

The object of the invention is achieved by a device having at least one camera directed onto an area provided with an encoding and a lighting device having a plurality of light sources of different emission spectra arranged on a hemisphere directed onto the examination area, at least two images of the examination area having at least one Camera under at least two different recording geometries (azimuth and Elongationswinkel the optical axis of the camera to the surface of the examination area) are recorded.

The invention will be explained in more detail with reference to the figures.

In 1 is a code reader ( 1 ), consisting of an arrangement of two cameras ( 8th . 8th' ) with non-parallel optical axes ( 20 . 20 ' ) representing an examination area ( 3 ) on a surface ( 2 ) of the substrate (not shown) to the individual cameras ( 8th . 8th' ) associated image planes ( 5 . 5 ' ) by means of the objectives ( 9 . 9 ' ) maps. In the picture plane ( 5 . 5 ' ) is the camera ( 8th . 8th' ) each have an image sensor ( 10 . 10 ' ) arranged. As an image sensor ( 10 . 10 ' ), a CCD or CMOS image sensor is preferably used. The code reader ( 1 ) has a plurality of lighting devices ( 4 . 4 ' . 4 '' ), which consists of an array of directionally radiating light sources ( 6 . 6 '' ), which are based on the study area ( 3 ) exist. As directed radiating light sources ( 6 . 6 '' ), light-emitting semiconductor elements (LED) with integrated lens or laser diodes can be used. The image levels ( 5 . 5 ' ), as in 1 represented perpendicular to the respective optical axis ( 20 . 20 ' ) the camera ( 8th . 8th' ) or inclined to it. A pan double arrow at the image plane ( 5 ' ) indicates that, for example, to realize a Scheimpflug condition the image plane ( 5 ' ) with the image sensor ( 10 ' ) relative to the optical axis ( 20 ' ) the camera ( 8th' ) is pivotable.

In 2 is a code reader according to the invention ( 1 ), in which unlike the 1 the optical axes ( 20 . 20 ' ) of the cameras ( 8th . 8th' ) are arranged parallel to each other. The image of the examination area ( 3 ) on the image plane ( 5 ' ) the camera ( 8th' ) via a mirror ( 7 ). The lighting device ( 4 '' ) serves the approximate realization of a bright field illumination of the examination area ( 3 ) with respect to the camera ( 8th' ) The 3 shows the same beam paths of the cameras ( 8th . 8th' ) as in 2 ; different here is the lighting device ( 4 '' ) with respect to the surface ( 2 ) arranged. The directionally radiating light source ( 6 '' ) is here via a mirror ( 7 ' ) to the examination area ( 3 ). It can be seen that all image levels ( 5 . 5 ' ) and all levels of lighting devices ( 4 . 4 ' . 4 '' ) parallel to the surface ( 2 ), which results in the realization of the code reader ( 1 ) can lead to significant cost advantages.

In 4 is a modification of the arrangement 3 shown. The arrangements of the cameras ( 8th . 8th' ) and the lighting devices ( 4 . 4 ' . 4 '' ) are identical as in 3 ; the mirror ( 7 . 7 ' . 7 '' ) are, however, opposite the surface ( 2 ) arranged displaceably and rotatably. For example, if the mirror ( 7 ) from the surface ( 2 ) moved parallel away and simultaneously in the direction of the optical axis ( 20 ' ) in the position of the mirror ( 7 '' ) is pivoted, then with the fixed camera ( 8th' ) the examination area ( 3 ) recorded at different angles. It is provided within the scope of the invention, the mirrors with their normal not only in the by the optical axes ( 20 . 20 ' ) but free to shift in space. The same goes for the mirror ( 7 ' ), the lighting device ( 4 '' ) to the examination area ( 3 ) reflects. The displacements of the mirrors are only limited by the fact that the illumination and camera beam paths the examination area ( 3 ).

In 5 is an arrangement with beam paths similar to in 3 shown, wherein for the two recording beam paths only one camera ( 8th ), The camera ( 8th ) has two lenses ( 9 . 9 ' ) and two deflecting prisms ( 15 . 15 ' ), by means of which the examination area ( 3 ) via two different beam paths on a single image sensor ( 10 ) are displayed side by side.

It is within the scope of the invention to provide more than two different images of the examination area ( 3 ) on a single image sensor ( 10 ).

In 6 - 8th are technical implementations of the code reader ( 1 ). In 6 are two cameras ( 8th . 8th' ), which depict an examination area, not shown. The examination area is illuminated by a lighting device which is connected to a hemisphere with a multiplicity of individual, directed light sources ( 6 . 6 ' . 6 '' ) is approximated. The light sources are on lighting boards ( 12 ) and ( 16 . 16 ' . 16 '' . 16 ''' ), the light sources having punctiform light sources with a large opening angle or directionally emitting light sources (US Pat. 6 . 6 ' . 6 '' ) could be. In 6 is around the camera window ( 17 ) the camera ( 8th ) a lighting board with an array of light sources ( 13 ), which have a small emission angle and thus emit light directed, but the light sources ( 13 ) are not aligned with respect to the examination area, not shown. To that of the light sources ( 13 ) emitted light on the examination area ( 3 ) is in a small distance in front of the illumination board in comparison to the focal length ( 12 ) as a Fresnel lens ( 11 ) formed collecting lens provided by the prismatic effect of the Fresnel lens ( 11 ) that of the light sources ( 13 ) emitted light on the examination area, not shown ( 3 ).

The lighting boards ( 16 . 16 ' . 16 '' . 16 ''' ) are aligned with their normal to the examination area and with directional emitting LEDs with integrated lenses ( 18 ) equipped. The lighting board ( 16 ''' ) carries a camera window ( 17 ' ) for the camera ( 8th' ) through which the camera ( 8th' ) looks at the examination area, not shown. In 7 is the arrangement off 6 schematically from the direction of the examination area ( 3 ).

In 8th is a code reader ( 1 ) with lighting boards ( 12 ' . 12 '' . 12 ''' . 12 '''' ) whose normals are aligned parallel to the examination area (not shown) and which are aligned with light sources ( 13 ' . 13 '' . 13 ''' . 13 '''' ) are equipped. It is planned, in front of the lighting boards ( 12 ' . 12 '' . 12 ''' . 12 '''' ) Segments ( 14 ) Fresnel lenses ( 11 ) such that the optical axis of the Fresnel lens ( 11 ) lies approximately in the plane of the examination area and contains it. The lens segments of the Fresnel lens ( 11 ) in front of the lighting boards ( 12 '' . 12 ''' . 12 '''' ) were provided in 8th the clarity omitted. The location-dependent prism effect of the segments ( 14 ) of the Fresnel lens ( 11 ) causes a deflection of the light sources ( 13 ) emitted light in the direction of the examination area, not shown.

The lighting board ( 12 ' ) with the light sources ( 13 ' ) and the segment ( 14 ) a Fresnel lens ( 11 ) is in 10 shown. In 9 is shown schematically how the lens segment ( 14 ) within the Fresnel lens ( 11 ) is arranged.

The lighting device according to the invention assumes that the examination area ( 3 ) is irradiated, be it by the fact that each individual light source directed to the examination area radiate or that a flat array of light sources of small size is imaged or deflected on the examination area. It is envisaged to make the light sources changeable in their spectral properties or to construct the illumination devices from light sources with different emission spectra in such a way that the different light sources, each with the same spectral distribution, are distributed approximately uniformly over the hemisphere and can be controlled individually or in groups by means of a control ,

It has been shown in practice that at least two different light sources, namely those emitting in the red, infrared (IR) or near infrared (NIR) wavelength range and emitting in the blue wavelength range light sources must be distributed over the hemisphere of the lighting devices in order to different Illumination and recording geometries to achieve at least one image with optimal image contrast.

A desirable, universal illumination geometry would be given by the fact that a hemisphere would be completely equipped with light sources directed onto the examination area, which could be controlled individually or in groups. Thus, each azimuth and each Elongationswinkel for illuminating the examination area on the wafer surface would be possible. This structure is technically difficult to realize in a manageable budget. It has been shown in practice that it is sufficient for silicon wafers for solar cells in all stages of processing to be able to individually control individual light sources or a few groups of light sources, namely, for example, an illumination approximately perpendicularly from above to the examination area of the wafer surface and at least each four ring segments, from which the wafer surface is irradiated directed at different Azimuthwinkeln.

It is envisaged to arrange on the illumination boards, which approximate the hemisphere approximately through a half-space of a decaeled, light sources, which radiate directed at the examination area. As such, LEDs with integrated lenses are preferably used.

It is provided in the context of the invention to arrange light sources with different opening angles on the illumination boards and to image or redirect these light sources with attachment optics, for example by means of Fresnel lenses or segments of Fresnel lenses on the examination area. The individual light sources or groups of light sources can be switched individually and regulated in their brightness. It is intended to make the lighting devices programmable with regard to their spectral properties. It has been shown in practice that to achieve sufficient image contrast at least two types of light, such as blue and near IR light (NIR) are necessary.

The code reader according to the invention has at least two imaging beam paths with different recording geometries. Due to the different wafer properties during the machining process, a vertical and under a certain azimuth or Elongationswinkel taking place is necessary to achieve a sufficient image contrast.

The optimal acquisition geometries and illumination scenarios are preferably selected by preliminary experiments from a large number of possible acquisition geometries and illumination scenarios. In order to identify the wafers by recognizing and decoding the code during solar cell production, preferably only the selected acquisition geometries and illumination scenarios are used.

A preferred arrangement of the code reader ( 1 ) provides that the at least one camera ( 8th ) receives the examination area at an azimuth angle of 90 ° and a second camera ( 8th' ) the examination area at an azimuth angle of less than 60 ° to the surface ( 2 ) of the solar cell wafer.

A further preferred arrangement of the code reader (!) Provides that the at least one camera ( 8th ) the examination area ( 3 ) at an azimuth angle of 90 ° and on a part of the image sensor ( 10 ) and that on a second part of the image sensor ( 10 ) via a deflection prism ( 15 . 15 ' ) or a mirror ( 7 . 7 ' . 7 '' ) the examination area ( 3 ) at an azimuth angle of less than 60 ° to the plane of the solar cell wafer on a second part of the image sensor.

Another preferred arrangement of the code reader ( 1 ) provides that the at least one camera ( 8th . 8th' . 8th'' ) with a lens ( 9 . 9 ' . 9 '' ) and a mirror ( 7 . 7 ' . 7 '' ) the examination area ( 3 ) on the image sensor ( 10 . 10 ' . 10 '' ) and at least two images of the examination area ( 3 ) each having different azimuth angles to the surface ( 2 ) are produced by the mirror ( 7 . 7 ' . 7 '' ) is rotatably and displaceably mounted and automatically adjustable by means of the control and the images after the changed setting of the mirror ( 7 . 7 ' . 7 '' ).

Another preferred arrangement of the code reader ( 1 ) provides that the illumination hemisphere consists of at least five illumination plates arranged tangentially to the hemisphere ( 16 . 16 ' . 16 '' . 16 ''' ) and in each case at least two of the lighting boards ( 16 . 16 ' . 16 '' . 16 ''' ) a camera window ( 17 . 17 ' ) for the camera beam path, wherein the light sources of the lighting boards can each be controlled individually or in any groups.

Another preferred arrangement of the code reader ( 1 ) provides that on the lighting boards ( 16 . 16 ' . 16 '' . 16 ''' ) arranged in at least two different wavelength ranges irradiated light sources ( 6 . 6 ' . 6 '' ) evenly across the lighting boards ( 16 . 16 ' . 16 '' . 16 ''' ) are distributed and can be controlled individually or in any groups.

Another preferred arrangement of the code reader ( 1 ) provides that the lighting boards ( 16 . 16 ' . 16 '' . 16 ''' ) in addition to the light sources directed in the blue and near infrared wavelength range (US Pat. 6 . 6 ' . 6 '' ) further diffuse or directed in other wavelength ranges radiating light sources ( 6 . 6 ' . 6 '' ) having.

Another preferred arrangement of the code reader ( 1 ) provides that the five lighting boards ( 16 . 16 ' . 16 '' . 16 ''' ) represent the sides of a cube open to the examination area and that between the illumination boards ( 16 . 16 ' . 16 '' . 16 ''' ) and the examination area ( 3 ) each a lens segment ( 14 . 14 ' . 14 '' . 14 ''' . 14 '''' ) as a Fresnel lens ( 11 ) trained converging lens with the respective focal point in the examination area ( 3 ) is arranged.

A method using the code reader ( 1 ) provides the captured images in the Evaluate the image processing computer sequentially that the individual images are searched sequentially for the presence of codes or code fragments and found code fragments of individual images to undisturbed, readable codes are composed.

It is envisaged that the electronic controller will control the light sources (at least in the blue and near infrared (NIR) wavelength range 6 . 6 ' . 6 '' ), in each case according to wavelength ranges separately controlled, for each wavelength range light sources with different illumination angles are each controlled individually or in predetermined selection groups, whereby each a clearly writable and reproducible lighting scenario is generated.

It is intended to select a small selection of lighting scenarios and recording geometries by preliminary tests from the large number of possible lighting scenarios and recording geometries and to store the specifications for the electronic control in a look-up table so that they can be recalled at any time.

LIST OF REFERENCE NUMBERS

1

code reader

2

surface

3

study area

4, 4 ', 4' '

lighting device

5, 5 ', 5' '

image plane

6, 6 ', 6' '

directed radiating light source

7, 7 ', 7' '

mirror

8, 8 ', 8' '

camera

9, 9 ', 9' '

lens

10, 10 ', 10' '

Image sensor

11

Fresnel lens

12

lighting board

13, 13 ', 13' ', 13' '', 13 '' ''

light source

14, 14 ', 14' ', 14' '', 14 '' ''

lens segment

15, 15 '

deflecting prism

16, 16 ', 16' ', 16' ''

lighting board

17, 17 '

camera window

18, 18 ', 18' ', 18' ''

LED with integrated lens

20, 20 '

Optical axis of the camera

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009010369 A1 [0004]
• DE 1020089043750 A1 [0005]
• DE 3540288 C2 [0006]
• DE 10142165 B4 [0007]
• DE 10162270 B4 [0008]
• DE 102005005536 A1 [0009]
• EP 0685140 B1 [0009]
• US 6105869 A [0010]
• WO 99049347 A1 [0011]

Claims (10)

Device for reading codes in an examination area ( 3 ) on the surface ( 2 ) of a solar cell wafer, the device comprising: • at least one camera ( 8th . 8th' . 8th'' ) with a lens ( 9 . 9 ' . 9 '' ) and an image sensor ( 10 . 10 ' . 10 '' ) for taking at least two images of the examination area ( 3 ) each with different recording beam paths, • a lighting device ( 4 . 4 ' . 4 '' ) for illuminating the examination area ( 3 ) comprising a plurality of individually irradiated or selectable in predetermined selection groups, directionally radiating light sources ( 6 . 6 ' . 6 '' ) on an illumination hemisphere with one in the examination area ( 3 ) and emit light in at least two incompletely overlapping wavelength ranges from the ultraviolet (UV) to near-infrared (NIR) wavelength range; an electronic control comprising a predetermined selection of combinations of pick-up beam paths, illumination beam paths and wavelength ranges of the directionally-radiated ones Light sources ( 6 . 6 ' . 6 '' ) automatically sets one after the other and picks up the respectively associated images, and • an image evaluation computer, which receives the recorded images via an interface from the controller and has the means for decoding the recorded codes. Apparatus according to claim 1, characterized in that the at least one camera ( 8th ) receives the examination area at an azimuth angle of 90 ° and a second camera ( 8th' ) the examination area at an azimuth angle of less than 60 ° to the surface ( 2 ) of the solar cell wafer. Apparatus according to claim 1, characterized in that the at least one camera ( 8th ) the examination area ( 3 ) at an azimuth angle of 90 ° and on a part of the image sensor ( 10 ) and that on a second part of the image sensor ( 10 ) via a deflection prism ( 15 . 15 ' ) or a mirror ( 7 . 7 ' . 7 '' ) the examination area ( 3 ) at an azimuth angle of less than 60 ° to the plane of the solar cell wafer on a second part of the image sensor. Apparatus according to claim 3, characterized in that the at least one camera ( 8th . 8th' . 8th'' ) with a lens ( 9 . 9 ' . 9 '' ) and a mirror ( 7 . 7 ' . 7 '' ) the examination area ( 3 ) on the image sensor ( 10 . 10 ' . 10 '' ) and at least two images of the examination area ( 3 ) each having different azimuth angles to the surface ( 2 ) are produced by the mirror ( 7 . 7 ' . 7 '' ) is rotatably and displaceably mounted and automatically adjustable by means of the control and the images after the changed setting of the mirror ( 7 . 7 ' . 7 '' ). Device according to one of claims 1-4, characterized in that the illumination hemisphere consists of at least five illumination plates arranged tangentially to the hemisphere ( 16 . 16 ' . 16 '' . 16 ''' ) and in each case at least two of the lighting boards ( 16 . 16 ' . 16 '' . 16 ''' ) a camera window ( 17 . 17 ' ) for the camera beam path. Device according to one of claims 1-5, characterized in that the on the lighting boards ( 16 . 16 ' . 16 '' . 16 ''' ) arranged in at least two different wavelength ranges irradiated light sources ( 6 . 6 ' . 6 '' ) evenly across the lighting boards ( 16 . 16 ' . 16 '' . 16 ''' ). Device according to one of claims 1-6, characterized in that the lighting boards ( 16 . 16 ' . 16 '' . 16 ''' ) in the blue and near infrared wavelengths directed light sources ( 6 . 6 ' . 6 '' ) and in addition to these further diffused or directed in other wavelength ranges light sources ( 6 . 6 ' . 6 '' ) exhibit. Device according to one of claims 1-7, characterized in that the five lighting boards ( 16 . 16 ' . 16 '' . 16 ''' ) represent the sides of a cube open to the examination area and that between the illumination boards ( 16 . 16 ' . 16 '' . 16 ''' ) and the examination area ( 3 ) each a lens segment ( 14 . 14 ' . 14 '' . 14 ''' . 14 '''' ) as a Fresnel lens ( 11 ) trained converging lens with the respective focal point in the examination area ( 3 ) is arranged. Method using the device according to any one of claims 1-8, characterized in that the electronic control, the at least in two wavelength ranges from the wavelength range between UV and NIR directed radiating light sources ( 6 . 6 ' . 6 '' ), in each case separated according to wavelength ranges and illumination geometries, one after the other in each case individually or in predetermined selection groups and thereby each generates a lighting scenario and that for each lighting scenario with the at least one camera ( 8th ) At least one recording is generated, which is forwarded to the image analysis computer. Method using the device according to one of claims 1-9, characterized in that the recorded images in Image evaluation to be sequentially evaluated so that the individual images are evaluated sequentially for the presence of codes or code fragments and found code fragments of individual images to undisturbed, readable codes are composed.

Images