A light beam is projected on a reference plane and an object to-be-measured, a phase difference between reflected lights from them is changed by a phase shifter, a drive voltage for causing the change of the phase difference is applied to the phase shifter, a magnitude of phase shift of the phase of the reflected lights is detected by a phase shift detector on the basis of the drive voltage at a point of time at which the change of the phase difference of the reflected lights has been compensated, and an up pulse or down pulse is generated by an up-down pulse generator upon detecting a discontinuous change in the magnitude of phase shift attributed to the displacement of the object to-be-measured, while a pulse is generated by another pulse generator upon sensing a change in brightness of an interference signal of the reflected lights attributed to the displacement of the object to-be-measured. Besides, a mode selecting circuit supplies the output of the up-down pulse generator to a counter when a displacement speed of the object to-be-measured is lower than a reference speed, whereas it supplies the output of the other pulse generator to the counter when the displacement speed is higher than the reference speed. The displacement of the object to-be-measured is measured by utilizing an output of the counter.
A liquid-crystal display device performs a feedback process. A video signal is written on pixels on a unit by unit basis, each unit including a plurality of pixels (six pixels, for example). Scan pulses output from RGB LCD panels are supplied to a driver IC that supplies the RGB LCD panels with a variety of timing signals. A delay amount from the scan pulses from the optimum state thereof is measured. The delay amount is accounted for in a pulse that samples and holds the video signal, i.e., a pulsewidth control clock pulse.
In apparatus and method for measuring a displacement of an object to be measured, a magnitude of the displacement is derived on the basis of a difference in periods of a phase modulated signal and a reference signal, a ratio between the periods of a basic clock and of an interpolation clock which is varied according to the magnitude of the displacement, a clock signal whose period is a multiplication of a period of the basic clock by the ratio as a multiplier, a pulse train signal is created whose number of pulses are given by the magnitude of the displacement and supplied to an A/B phase converter.
In order to measure a phase difference of an opto-magnetic disk having a substrate and a magnetic record layer, linearly polarized light is made incident upon the magnetic layer of the disk from the side of the substrate and light reflected by the disk is received to derive an information signal recorded in the disk, while the opto-magnetic disk is rotated at a usual reproducing speed. A phase compensator arranged in an optical path of the light reflected by the disk is adjusted to change a phase difference introduced by the phase compensator into the light reflected by the disk, while a level of amplitude and/or C/N of the reproduced information signal is monitored. A value of the phase difference introduced by the phase compensator when the amplitude and/or C/N of the reproduced information signal becomes maximum is derived as a measured phase difference of the opto-magnetic disk.
Techniques to adjust sampling times of an input signal. The techniques may utilize multi-level modification of the phase of a sampling clock. For example, the level of modification of the phase of the sampling clock may depend on the phase angle of the sampling clock in which transitions of the input signal occur.
