Abstract: Optical recording method and apparatus using this method. An optical recording method and recording apparatus using this method is described in which an optimum write power of a radiation beam in the apparatus is set by writing a series of test patterns on an optical recordable medium, forming a read signal from the patterns, reading a preset value of the derivative of the modulation of the read signal with respect to the write power from the medium, and processing the read signal together with the preset value to derive an optimum value of the write power.

Abstract: An optical recording method and recording apparatus using this method is described in which an optimum write power of a radiation beam in the apparatus is set by writing a series of test patterns on an optical recordable medium, forming a read signal from the patterns, reading a preset value of the derivative of the modulation of the read signal with respect to the write power from the medium, and processing the read signal together with the preset value to derive an optimum value of the write power.

Abstract: In an interferometric alignment system provides an alignment signal for reproducibly registering a reticle 10 with a wafer 12. The radiation from a laser 50, which is the illumination source for the interferometer, is modulated by a phase modulator 52 to eliminate spurious noise from the alignment signal.

Abstract: A method is described for setting an optimum write power for recording information on an optical recording medium. First a series of test patterns is written on the medium, each test pattern being written with a different write power. On reading the test patterns, the modulation of each read signal is determined. The modulations as a function of write power are curve-fitted to an analytic function. The normalised derivative of this function is determined analytically and is used to determine the value of the optimum write power for the medium.

Abstract: A method and apparatus for writing information on an optical recording medium by setting an optimum write power for recording information on the optical recording medium. First a series of test patterns is written on the medium, each test pattern being written with a different write power. On reading the test patterns, the modulation of each read signal is determined. The modulations as a function of write power are curve-fitted to an analytic function. The normalised derivative of this function is determined analytically and is used to determine the value of the optimum write power for the medium.

Abstract: An optical distance or profile meter in which radiation reflected from a surface (630) is projected onto a radiation-sensitive dectection system via an optical system (641, 642) comprises a radiation-blocking plate (250) formed with radiation windows (651). The radiation-blocking plate only transmit radiation which is reflected from the surface at an angle relative to the optical axis of the optical system. The extent of the pattern of radiation spots thus formed on the detection system is a measure of the distance (.DELTA.h) from the surface. The detection system may comprise a semitransparent filter(660) whose transmission coefficient exhibits a position-dependent variation. This enables the radiation-sensitive element to be constructed as a single element (661) and the effects of speckle noise to be reduced substantially.