Abstract: The characteristic test device 1 supplies the output from the photo detector of the optical pickup 2, as signals A to F, directly to the sample hold circuits 8a-8f. The sample hold circuits 8a-8f, the multiplexer 9, and the second analog/digital converting circuit 10 convert the signals A to F into digital data with the sampling frequency of 50 KHz or more. In the computer 12, the processing division 12d reads out the indicated program from the data storage division 12b, where the program P for measuring the level of RF signal, is stored. The processing division 12d performs the operation of the indicated measurement items, based on the digital data stored in the second memory 11, then measures the characteristic of the optical pickup 2.

Abstract: A jitter measurement device for reproducing a signal from an optical disc, which has simple circuit configuration and can effectively measure the jitter component. A matrix circuit 4 supplies the RF signals to the analog/digital converting circuit 6. Second, the computer 8 computes the slice level from the digitized data of the RF signals. Computer 8 computes the time point at which the RF signals become the indicated slice level, by interpolating, based on the digital data at the sampling point in the neighborhood of the said slice level, and the sampling frequency of the analog/digital converting circuit 6. A computer 8 computes each time breadth between the time points at which the RF signals become the slice level, then computes the jitter component of the reproduced signal, based on the each time breadth.

Abstract: A device for measuring focusing characteristics of an optical pickup and/or an optical disc capable of measuring characteristics of focusing states with high accuracy by a simplified circuit. An arithmetic-logic unit 12d controls an offset supplying circuit 23 for applying an offset voltage to a focusing servo control signal. This arithmetic-logic unit 12d detects an error rate of the playback data in such a state in which the focusing position of the laser light is deviated by a pre-set offset amount. The arithmetic-logic unit 12d sequentially varies the offset voltage to repeat the above processing for detecting the error rate. The arithmetic-logic unit 12d approximates the relationship of the error rate to the offset amount by a quadratic curve based on detected data. The offset amount which minimizes the error rate is found from this equation of approximation.

Abstract: A device for measuring characteristics of an optical pickup and/or an optical disc by which characteristics of tracking signals can be measured accurately in a noise-free manner. The measurement device 1 has a sample-and-hold circuit 8 and an analog-to-digital converter 10 for directly sampling an output of an optical pickup 2 as signals A to F in order to store the resulting digital data in a second memory 11. An arithmetic-logic unit 12d measures tracking error signals based on the digital data stored in the second memory 11. The arithmetic-logic unit 12d eliminates unstable portions of the tracking signals generated responsive to rotational eccentricity of the optical disc to find data.

Abstract: A device for measuring characteristic values of an optical pickup and/or an optical disc capable of detecting tracking signals for measuring characteristic values even if optical disc rotation is not subjected to eccentricity. The device for measuring characteristic values of an optical pickup and/or an optical disc 1 samples outputs of photodetectors of an optical pickup 2 as signals A to F directly by a sample-and-hold circuit 8 and an analog-to-digital converter 10 to store the resulting digital data in a second memory 11. An arithmetic-logic unit 12d measures tracking error signals based on the digital data stored in the second memory 11. A signal generating circuit 25 then sends a sine wave signal to a tracking coil 2b for moving the laser light illuminated on the optical disc along the radius of the disc.