Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – In combination with or also constituting light responsive...
Reexamination Certificate
2002-02-15
2003-09-16
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
In combination with or also constituting light responsive...
C257S082000, C257S084000, C438S024000, C438S025000, C438S026000, C438S027000, C250S23700G
Reexamination Certificate
active
06621104
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an integrated optoelectronic thin-film sensor for a measuring system, and a method for producing it.
2. Description of the Related Art
A measuring system is known from GB 1,504,691 and corresponding DE 25 11 350 A1, wherein the displacement of a first component in relation to a second component is a determined. Two gratings are provided for this, which are at a constant distance from each other and each one of which is respectively fastened on one component. If the second grating is illuminated with divergent light, the first grating generates a periodic image of the second grating, which image moves if there is a relative movement between the two components. Photodetectors, which have a periodic structure and are fixedly connected with the second component, are furthermore provided. In this case the first one is a reflecting grating, and the second grating and the photodetectors are essentially located in one plane. The light source and the second grating can also be replaced by a structured light source, which generates the same image as a conventional light source and a grating. The structure of the photodetectors interacts with the image in such a way that a periodic change of the output signal from the photodetector occurs if a relative movement exists between the first and second components.
It is disadvantageous here that the individual components are discretely and separately provided. Because of this, a relatively large installation space is required for the entire arrangement.
It is known from DE 197 01 941 A1 that a scanning grating is arranged on the side of a transparent substrate facing a scale. The scanning grating is illuminated by a light source in such a way that an image of the grating is projected onto the scale. A second grating is located on the scale, which reflects the image onto a structured photodetector. In this case the transparent substrate for the first grating is connected with the semiconductor material from which the structured photodetector is made in such a way that the scanning grating and the photodetector are exclusively offset from each other in the measuring direction, but are at the same distance from the scale. In a second embodiment of DE 197 01 941 A1, the scanning grating is arranged on the side of the transparent substrate which is facing away from the scale. An optical chip, which contains the photodetector, is arranged on the same side of the same transparent substrate as the scanning grating. By means of this arrangement it is also achieved that the scanning grating and the structured photodetector have approximately the same distance from the scale.
In connection with the first embodiment there is the disadvantage that the transparent substrate to which the scanning grating is applied must be connected with the semiconductor material of which the structured photodetector is made. This connection must be performed very accurately, so that the structure of the photodetector is aligned parallel with the grating, and that the structure and the grating have the same distance from the scale. This exact connection between the substrate and the semiconductor material is therefore very difficult to provide. Furthermore, the second embodiment has the disadvantage that an optical chip must be fastened on the transparent substrate. Because of the attachment by means of a chip-on-glass technique, a space unavoidably exists between the optical chip and the substrate, because of which the distances between the transmitting grating and the scale, as well as between the photodetector and the scale, differ considerably, which results in a clear decrease of the optical properties of the arrangement.
It is known from DE 40 91 517 T1 to make a sensor for a measuring system out of a single block of semiconductor material. Here, photo elements designed as grating lines are provided on the surface of a flat-designed light-emitting diode, through which the light-emitting diode cannot radiate. A structured photodetector is created in this way, above or below of which a structured light source is arranged.
This sensor has the disadvantage that the photodetector structure and the structured light source unavoidably cannot have the same distance from a scale, since the light-emitting diode and the photodetector are placed on top of each other. This difference in the distance from the scale also clearly decreases the optical properties of the sensor.
It is known from EP 543 513 A1 to provide a structured photodetector, as well as a structured light source in the form of at least one light-emitting diode of a sensor on a common semiconductor layer of III/V semiconductor material, for example gallium arsenide GaAs. It is possible by means of providing the structured light source and the structured photodetector on a common semiconductor material to meet the requirement of providing the transmitting and receiving structures possibly in one plane very satisfactorily. Moreover, single field scanning takes place, wherein the photo elements are offset by 90°+k*360°, where k is a whole number. Thus, several photo elements are arranged offset in the measuring direction by ninety degrees of angle plus whole-number multiples of three hundred sixty degrees of angle. Because of this, scanning becomes particularly insensitive to interferences.
The disadvantage here is that it is not described how the production of the structured photodetector and the structured light source on a common semiconductor material of GaAs takes place. If technique known from the prior art are used for producing the semiconductor, this manufacturing process is very elaborate and therefore expensive.
An optical sensor for a measuring system, having a light-receiving component and at least one optical component which acts on the light beam transmitted by the component emitting the light before it arrives at the component receiving the light, is known from EP 720 005 A2. This sensor has a spacer element, which defines the distance between the component emitting, or respectively receiving, light, and the optical components. In this case the spacer element is embodied in such a way that it is connected with another component. It is achieved by means of this that the optical sensor transmits and receives optical signals on one of its sides, because of which optical elements are arranged on this side, and has conductors for electrical signals on the other of its sides.
In connection with this it is disadvantageous that the component receiving light, the component transmitting light, the at least one optical component and the spacer element are all separate components, which must be produced and assembled separately. This is very expensive in view of the required accuracy of optical sensors in measuring systems. Moreover, the optical sensor is rather voluminous, since the individual components also must be separately handled.
An electronic hybrid component is known from DE 197 20 300 A1, wherein an implanted chip is placed in a chip-on-chip arrangement on a support substrate. To this end, the support substrate has at least one cavity, in which an electrical insulation layer with a metal layer on top of it is located. The chip implanted in the cavity is connected to the metal layer, because of which the latter is used as an electrical conductor. If the implanted chip is a light-emitting diode, the metallized layer can also be used for reflecting the radiation from the latter at the walls of the cavity.
This arrangement has the disadvantage that the direction of radiation from the light-emitting diode, as well as its electrical contacts, are arranged on one side of the semiconductor layer, or are emitted from this one side.
A radiation-sensitive detector element with an active area is known from DE 196 18 593 A1, wherein the active area is formed between two adjoining layer areas of a layer arrangement of different charge substrates, in which a conversion of incident electromagnetic radiation into electrical sign
Michel Dieter
Speckbacher Peter
Brinks Hofer Gilson & Lione
Dr. Johannes Heidenhain GmbH
Kang Donghee
Thomas Tom
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