Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-12-21
2002-11-26
Allen, Stephone (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S231160
Reexamination Certificate
active
06486467
ABSTRACT:
The present invention relates to an integrated optoelectronic sensor of a measuring system for scanning a scale with graduation markings, and to a method for manufacturing such sensor.
DESCRIPTION OF RELATED ART
British Patent 1,504,691 and a corresponding German Patent Application 25 11 350 A1 describe a measuring system in which the movement of a first assembly relative to a second assembly is detected. For this purpose, there are two gratings, which are at a constant distance from each other, each being attached to one assembly, When the second grating is illuminated by the divergent light of a light source, the first grating generates a periodic image of the second grating. The image is not stationary if there is a relative motion between the two assemblies.
Photo detectors are also included, which have a periodic pattern and are fixedly joined to the second assembly. The first grating is a reflecting grating, and the second grating as well as the photo detectors are essentially in the same plane. The light source and the second grating can also be replaced by a pattern-generating light source, which generates the same image as would a conventional light source and a grating. The pattern of the photo detectors interacts with the image such that a periodic change of the output signal of the photo detectors occurs if there is a relative movement between the first and second assemblies.
One are disadvantage of this system is that the two assemblies are formed individually, separately from one another. As a result, a relatively large space is required to assemble the entire arrangement.
German Patent Application 197 01 941 A1, describes arranging a scanning grating on the side of a light-transmissive carrier that is facing a scale. The scanning grating is illuminated by a light source such 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 pattern-generating photo detector. The light-transmissive carrier for the first grating is connected to the semiconductor material in which the pattern-generating photo detector is formed, so that the scanning grating and the photo detector are shifted exclusively in the measuring direction with respect to each other. The scanning grating and photo detector are at the same distance from the scale. German Patent Application 197 01 941 A1 also describes a scanning grating arranged on the side of the light-transmissive carrier that is facing away from the scale. An optical chip is arranged on the same light-transmissive carrier that contains the photo detector, on the same side as the scanning grating. This arrangement makes it possible to place the scanning grating and the pattern-generating photo detector at approximately the same distance from the scale.
The described system has the disadvantage that the light-transmissive carrier, on which the scanning grating is applied, must be joined to the semiconductor material in which the pattern-generating photo detector is formed. This connection must be carried out very precisely so that the pattern of the photo detector is aligned parallel to the grating, and the pattern and the grating have the same distance from the scale, This exact connection between carrier and semiconductor material is therefore very difficult to form.
The system also has the disadvantage that an optical chip has to be secured on the light-transmissive carrier. By securing the chip using chip-on-glass technology, it is inevitable that a distance will exist between the optical chip and the carrier. Because of this arrangement, the distances between the scanning grating and the scale, and between the photo detector and the scale significantly deviate from each other, which leads to a significant degradation of the optical properties of the arrangement.
German Patent 40 91 517 T1, describes a sensor for a measuring system made from a single block of semiconductor material. On the surface of a planar-configured light-emitting diode, there are photo elements configured as grating lines, through which the light-emitting diode can shine. In this way, a pattern-generating photo detector is formed, above or below which a pattern-generating light source is arranged.
One disadvantage of this sensor is that the photo detector pattern and the pattern-generating light source cannot have the same distance from a scale, since the light-emitting diode and the photo detector are disposed on top of each other. This varying distance to the scale in turn impairs the optical properties of the sensor.
European Patent Application 543 513 A1, describes a common semiconductor substrate made of III/V semiconductor material, such as gallium arsenide GaAs, having both a pattern-generating photo detector as well as a pattern-generating light source. Both of these components can be formed by a light-emitting diode and a sensor. By forming the pattern-generating light source and the pattern-generating photo detector on a common semiconductor material, the transmitting and receiving structuring can easily be placed as closely as possible in the same plane. Furthermore, a single-field scanning takes place in which the photo elements are shifted by [90°+(k*360)] degrees, with k being an integer. Therefore, a plurality of photo elements can be arranged so as to be shifted with respect to each other, in the measuring direction, by ninety degrees of angle plus whole-number multiples of three hundred sixty degrees of angle. In this ways the scanning becomes particularly insensitive to disturbances.
A disadvantage of this design is that there is no description how the pattern-generating photo detector and the pattern-generating light source can be manufactured on a common semiconductor material made of GaAs. If known technologies of semiconductor manufacturing from the related art are applied, this manufacturing process is very cumbersome and therefore expensive.
European Patent Application 720 005 A2 describes an optical sensor for a measuring system, which has a light-emitting component, a light-receiving component, and at least one optical component, which influences the beam of light emitted by the light-emitting component before the beam of light reaches the light-receiving component. This sensor has a distancing element, which defines a distance between the light-emitting or the light-receiving component and the optical component. According to the design, the optical sensor emits and receives optical signals on its side, so that all optical assemblies are arranged on the same side, and the leads for electrical signals are on the opposite side of the sensor.
One disadvantage of this system is that the light-receiving component, the light-emitting component, the at least one optical component, and the distancing element are all made as separate components, which must be manufactured and assembled separately. In view of the required tolerances for optical sensors of measuring systems, this process is very expensive. Furthermore, the optical sensor is relatively bulky, because the individual components must also be manipulated separately.
German Patent Application 197 20 300 A1 describes an electronic hybrid structural component with a chip-on-chip arrangement, where an implanted chip is arranged on a carrier substrate. For this purpose, the carrier substrate has at least one cavity in which is located an electrical insulating layer having a metallic layer on top of it. The chip implanted in the cavity contacts the metallic layer, as a result of which the latter is used as an electrical lead. If the implanted chip is a light-emitting diode, the metallization layer can also be used to reflect its beam on the walls of the cavity.
This arrangement has the disadvantage that both the illuminating direction of the light-emitting diode as well as its electrical contacts are arranged on one side of the semiconductor substrate, and light is only emitted on this one side.
German Patent Application 196 18 593 A1 describes a photo-sensitive detector element having an active reg
Michel Dieter
Speckbacher Peter
Allen Stephone
Dr. Johannes Heiden Hain GmbH
Hill Bradford
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