Abstract: Apparatus (10) and method (100) for inscribing a clock pattern (14), detecting the clock pattern (14) optically, and using the clock pattern (14) to write a sevo pattern in an information storage unit (12), such as a computer hard drive. The clock pattern (14) is inscribed using a marking system (64), which may include a laser (66) or employ other, even non-optical, methods. The clock pattern (14) is inscribable into various locations on a disk platter (16) inside the storage unit (12), including many outside the media surface (26) conventionally used for such in data storage units. While the disk platter (16) is rotating, the clock pattern (14) is on detected using an detection subsystem (46), if desired through a transparent window (36) in a hermetically sealed housing (34) of the storage unit (12), for use in writing the servo pattern with less sector-inconsistency error and off-track error.

Abstract: A position determining system (10) particularly useful for translation and rotation measurement. The position of a stage (12) is optically detected using light beams (124) and sensors (132) in a detection section (112). In a control section (114), electronic processing using amplifiers (152, 166), phase-sensitive synchronous demodulators (158, 168), and filters (160, 170) then produces position signals (162, 172) which a logic unit (174) processes into a results signal (180) which is communicated via a communications link (176) to an external system (22). The external system (22) may then display the measurement results for a human user or use them as feedback to control movement of the stage (12). Optionally, the external system (22) may send instruction signals (178) via the communications link (176) to the logic unit (174) to control the operation of the position determining system (10).

Abstract: A measurement apparatus (10, 110) and methods to perform positional types of measurement with normalization respective to either or both of light beam (16, 116) intensity and measurement target (12, 112) reflectivity. A light source, such as a laser diode (14, 114), produces a light beam (16, 116) which is directed at the measurement target (12, 112). One or more beamsplitters (28, 120, 124) in the path of the light beam (16, 116) direct sample portions into one or more photodetectors (32, 36, 122, 128) to obtain either or both of illumination and reflectivity sample values. A portion of the light beam (16, 116) which is reflected by the measurement target (12, 112) is passed through and restricted by an aperture (26, 132) and then detected by a position sensitive detector (38, 134) to obtain a position value. The position value may then be normalized based on either or both of the illumination and reflectivity sample values.

Abstract: Apparatus (10) and method (100) for inscribing a clock pattern (14), detecting the clock pattern (14) optically, and using the clock pattern (14) to write a sevo pattern in an information storage unit (12), such as a computer hard drive. The clock pattern (14) is inscribed using a marking system (64), which may include a laser (66) or employ other, even non-optical, methods. The clock pattern (14) is inscribable into various locations on a disk platter (16) inside the storage unit (12), including many outside the media surface (26) conventionally used for such in data storage units. While the disk platter (16) is rotating, the clock pattern (14) is on detected using an detection subsystem (46), if desired through a transparent window (36) in a hermetically sealed housing (34) of the storage unit (12), for use in writing the servo pattern with less sector-inconsistency error and off-track error.

Abstract: The present invention is a laser system (10, 100, 200) employing paired simple lasers (12, 16) or paired Zeeman type lasers (102, 112 or 202, 204). Systems of beambenders (20, 108, 210, 212, 214), half-wave plates (106, 116), and polarizing beamsplitters (22, 104, 114, 118, 216) pair the frequency component of one laser (12, 16, 102, 112, 202, 204) with that of another to produce one or more measurement beams (24, 150, 160, 228, 230) having orthogonally polarized frequency components. Systems of beamsplitters (26, 120, 124, 218, 220) and photodetectors (30, 122, 126, 206, 208) provide reference information about the frequency difference (196, 198) between the respective frequency components in the measurement beams (24, 150, 160, 228, 230). The frequency difference (196, 198) is tunable across a wide range, specifically including 4 MHz to 40 MHz when the lasers (12, 16, 102, 112, 202, 204) are conventional He--Ne types.

Abstract: The present invention is a laser (12) having a resonator (28) between an output coupling mirror (20) and a high-reflection mirror (26). A photoelastic plate (38) is incorporated in a photoelastic cell (24), or a photoelastic mirror (36) used in place of the high-reflection mirror (26). The photoelastic plate (38) is placed in the resonator (28) and introduces an artificial anisotropy to the laser (12). The photoelastic plate (38) has privileged directions (34), which are aligned with the axes of the artificial anisotropy. A magnetic field (32) is applied transversely to the resonator (28), in alignment with one of the privileged directions (34), to produce two orthogonal linearly polarized frequencies in an output beam (30) with the Zeeman effect.

Abstract: A servotrack writing apparatus (10) for use on computer disk drive workpieces (12). A writer controller (58) puts the writing apparatus (10) in the role of master to direct the workpiece (12) as a slave to position its read-write head (36) and to write the servotracks. A tracking section (54) provides a modulated light beam (72) from which a reflected portion is detected by a bi-cell photo sensor (70) and processed in the writer controller (58) to determine the position of a thru-hole (40) or a detection region (42) in the actuator arm (24) of the workpiece (12). The writer controller (58) may use a lock-in amplifier (102, 104) for the processing the reflected portion of the light beam (72). A reference arm (44) is locked and moved in a synchronous relationship with the actuator arm (24).

Abstract: An environmental metrology device (10) containing sensor (12) elements which include a pressure sensor (20), a temperature sensor (22), and a humidity sensor (24) all located in close proximity within a housing (18). Control circuitry (16) is further provided to direct operation of the sensors (12) and to communicate with an interferometer controller (42) via a signal port (14) and a cable (92). Additional instances of the device (10) may be connected in a daisy-chain network configuration via additional signal ports (14) and cables (90). One or more instances of the device (10) permit highly localized characterization of atmospheric index of refraction in the measurement region (60) of a laser interferometer (30). The interferometer controller (42) is thereby able to compensate measurements performed by the laser interferometer (30) before they are passed onto manufacturing process controls (48).

Abstract: A servotrack writing apparatus (10) having a reference section (30), a workpiece section (32), and a tracking section (34). With the reference section (30) a standard is established without a disk drive workpiece (12) mounted. A workpiece (12) is then mounted in the workpiece section (32) with a beamsplitter-reflector unit (52) attached to the actuator arm (20) bearing the read-write head (18) which is to be used for servotrack writing, and verification information is obtained for comparison with the standard. Based upon this comparison, correction of workpiece (12) mounting offset and eccentricity of beamsplitter-reflector unit (52) mounting may then be performed before servotracks are written, or compensation for such offset and eccentricity may be performed while servotracks are written.

Abstract: An improved laser refractometer (10) employing a interferometer optical component (12), an object mirror (14) and an etalon (16). The etalon (16) is moved in the path of a plurality of reference beams (22, 24) and a plurality of measurement beams (26, 28) such that the reference beams (22, 24) travel through a vacuum within the etalon while the measurement beams (26, 28) travel a like distance through the etalon (16) in ambient air. In varying the distance traveled by the laser beams (22, 24, 26, 28) within the etalon (16) any interference fringes detected by an interference fringe detection device (20) are attributable to differences in the optical paths of the measurement beams (26, 28) as compared to that of the reference beams (22, 24) which, in turn, is entirely attributable to the ambient index of refraction. In a first preferred embodiment of the improved refractometer (10) the angular distance between a pair of plates (30, 32) is varied by rotation of the etalon (16).

Abstract: What is disclosed is an improved high resolution laser interferometer (10) which gains an increase accuracy through elimination of a source of temperature change error by causing a reference laser beam (16) to traverse the same distance within glass as does a measurement laser beam (18). The inventive arrangement of optics combines a polarizing cube (24), a cube corner retroreflector (28), a right angle reflector (30), and two or more quarter wave plates (32), (34) and (36)to produce the desired result. An equally preferred alternate embodiment (210) of the invention combines the first preferred embodiment (10) with an etalon (240) to directly measure the refractive index of air. This measurement is then used to adjust readings obtained using the first preferred embodiment (10) to further improve accuracy.

Abstract: A servo track writing apparatus (10, 210) for writing servo tracks (16) on a media disk (14) of a disk drive assembly (12), the servo track writing apparatus (10, 210) having a laser interferometer (30) for positioning a remote servo track positioning arm (48, 248) with a second cube corner retroreflector (46) attached thereto. A relationship determining apparatus (56, 256) determines the physical relationship between the track positioning arm (48, 248) and a head positioning arm (22) or linear head actuator (220) using a light emitting device (58) and a photosensitive diode array (60).

Abstract: What is disclosed is an improved high resolution laser interferometer (10) which gains an increase in available resolution by means of increasing the number of reflections of a measurement laser beam (16) from a plane mirror (20) and thus by increasing the number of Doppler shifts undergone by the measurement laser beam (16). The inventive arrangement of optics combines a polarizing cube (24), a cube corner retroreflector (28), a right angle reflector (30), and one or more quarter wave plates (32) and (34) to produce the desired result. In the practice of the present invention, the measurement laser beam (16) is directed from a laser head (12) such that it is affected four times by any movement of the objective plane mirror (20) in a measurement plane (22) before being compared to a reference laser beam (16) in a signal analysis unit (14). The reference laser beam (16) is routed in a conventional manner to the signal analysis unit (14).