Patent Application
20080304076
Currently there are two optical sensors used with ring laser gyros (RLG). One of the sensors is a readout sensor and the other is a laser intensity monitor (LIM) sensor. Each of these sensors is produced in its own package. The RLG produces two laser beams at its sensing mirror and each of these sensors must be individually attached and aligned at the sensing mirror. Attachment of both of these sensors is time consuming and thereby costly.
Therefore, there exists a need for improving the efficiency of manufacturing RLGs.
The present invention provides methods and apparatus for applying sensors to a ring laser gyro. An example apparatus includes a housing having a cavity, a laser intensity monitor (LIM) sensor mechanically and electrically connected within the cavity of the housing, and a readout sensor mechanically and electrically connected within the cavity of the housing. The LIM sensor and readout sensor are connected within the housing based on predetermined light output properties of a sensor mirror of a ring laser gyro. When the readout sensor is properly aligned with the sensor mirror, then the LIM sensor is automatically aligned with the sensor mirror and output laser beam.
In one aspect of the invention, the housing is a ceramic case having embedded conductive paths.
In another aspect of the invention, the readout sensor includes two photo detectors and the LIM sensor includes one photo detector. The photo detectors are photodiodes.
Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings:
The LIM and readout sensor package 30 includes a housing 32 that includes electrical leads (not shown). The package 30 includes an LIM sensor 34 and a readout sensor 36. The LIM sensor 34 and the readout sensor 36 are electrically connected to an output device 42 via the leads within the housing 32. An example of the output device 42 is an oscilloscope or other type of processing device.
The exact location of where light beams 44 within the LBA 46 will exit the mirror 22 is known. The size of the housing 32 and the location of the LIM sensor 34 and the readout sensor 36 within the housing 32 are determined according to the exit information of the light beams.
In order to align the package 30 with the mirror 22, first, a light (laser) source is activated within the LBA 46. Next, the package 30 is attached to the sensing mirror 22 using an optical adhesive 40. Before the adhesive 40 sets, the package 30 is rotated until a signal outputted by the readout sensor 36, as processed and presented on the output device 42, indicates optimal alignment. Once the package 30 has been optimally aligned, it is maintained in this position until the optical adhesive 40 sets. The LIM sensor 34 is attached within the housing 32 such that when the readout sensor 36 becomes aligned with the mirror 22 and light beams 44, the LIM sensor 34 becomes aligned. Thus, only one step is needed for aligning both sensors 34 and 36. For example, the sensors 34 and 36 are oriented relative to one another within the cavity of the housing 32 in such a way that when the readout sensor 36 is rotated to produce a lissajous pattern as determined at the output device 42, the LIM sensor 34 is automatically aligned. The lissajous pattern is a nominal 90° phase shift between the two sensing elements of the readout sensor 36. In one embodiment, the LIM sensor 34 is rectangular shaped and sized to allow for accurate reception of the light beam outputted by the mirror 22 to compensate for any errors that might occur in misalignment of the readout sensor 36.
As shown in
In one embodiment, the readout sensor 36 includes two sensing elements (photo detectors, such as photodiodes). The LIM sensor 34 includes a single photo detector (photodiode).
In one embodiment, the readout sensor 36 is a dual sensing element having chrome grid lines, such as that described in U.S. Pat. No. 4,871,253, which is hereby incorporated by reference. The photodetector sensors 34 and 36 are attached to the housing 32 using epoxy, solder, or other standard methods known to those skilled in the art of packaging semiconductor devices.
In one embodiment, the housing 32 is a ceramic case that includes conductive traces that connect leads (not shown) within to a cavity 48 to the leads 38. The cavity 48 receives the sensors 34 and 36 and is surrounded by a raised wall 50 that receives an optically clear window (60,
While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.
