Patent ID: 11874144
Assignee: LI LIN
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 22:
23. A displacement measuring system with a control loop formed with a code carrier, an optical laser assembly, a signal processing unit, and a power driver, wherein the code carrier comprises:
an optical data-storage medium,
an absolute position reference code channel (APRCC) comprising at least one pit line or one missing pit line, which is uniquely distributed among one or more neighboring pit lines, and
a relative displacement measurement code channel (RDMCC) consisting of a continuous alternating uniform arrangement of a plurality of pit lines in a circumferential direction with equal depth, wherein edges of the plurality of pit lines form a plurality of bump lines, wherein the optical laser assembly comprises:
a laser diode,
an objective lens,
a coil actuator configured to drive an objective lens of the OLA to a position on top of the APRCC to read a first group of RF signals for the absolute position reference, focus a laser beam on the one or more bump lines and the one or more pit lines in a direction perpendicular to a surface of the data storage medium, and decode, with a photo detector, the laser beam reflected off the one or more bump lines and the one or more pit lines in the APRCC to generate a plurality of electronic signals and to obtain relative displacement reference information, and drive the objective lens of the OLA to a position on top of the RDMCC to read a second group of RF signals for an incremental displacement measurement; and
a photo detector, the photo detector comprising multiple light-sensitive elements arranged in a four-quadrant arrangement, wherein the multiple light sensitive elements are configured to sense light from the plurality of bump lines and the plurality of pit lines of the RDMCC to generate a plurality of electrical signals, the plurality of electrical signals from diagonal quadrants of the four-quadrant arrangement are added together and then subtracted from each other according to a function G1*(a+c)−(b+d) to generate a control signal for the purpose of auto-focusing, G1 is a parameter determined based on the electrical signals, and the power driver is configured to receive the control signal to power the coil actuator in the optical laser assembly to drive the objective lens to accomplish auto focusing.