Abstract: A height adjusting device for adjusting the height of a pickup, comprises a support mechanism for supporting the pickup on the carriage in a manner that a position of the pickup along the axis of rotation of the turntable of the optical disc player is adjustable and an adjusting device for driving the support mechanism to adjust the position of the pickup. The adjusting device generates a height position signal indicative of the position of the pickup and the support mechanism is driven in response to the magnitude of the height position signal only when the magnitude of the height position signal is greater than a predetermined level. According to the other aspect of the invention, a compensated height position signal is generated by superimposing a compensating signal indicative of the position of the optical system of the pickup relative to the housing of the pickup on the height position signal, and the support mechanism is driven in response to the magnitude of the compensated height position signal.

Abstract: A clamp mechanism for clamping an information recording disk such as a compact disk or a video disk to a turntable and which provides a strong and reliable clamping force despite variations in the thicknesses of the disks to be reproduced. The clamp mechanism includes a clamper including a magnet retaining member, a ring-like pressing member arranged to abut the information recording disk, and a plate spring member interconnecting the retaining member and the pressing member in such a manner that the retaining member and the pressing member are vertically movable relative to each other.

Abstract: A focus error detection device to be used in an optical system for recording and/or playing back information, including a light detector made up of four light receiving elements arranged symmetrically with respect to the center of the light detector, a multiplication means for generating a pair of multiplication signal by multiplying output signals of two light receiving elements which are arranged symmetrically with respect to the center of the light detector. The multiplication signals are applied to a subtraction means where the focus error signal is generated by the subtraction between the multiplication signals. Thereby the off-set of the focus error signal which has been caused by the deviation of the position of the center of the light beam from the center of the light detector is by far reduced.

Abstract: A focus error detection device to be used in an optical system for recording and/or playing back information, including a light detector made up of four light receiving elements arranged symmetrically with respect to the center of the light detector, a first operation circuit means connected to the light receiving elements for generating a focus error signal, and a second operation circuit means also connected to the light receiving elements for generating an off-set compensation signal. With this construction, and off-set of the focus error signal due to the deviation of the position of the reflection light beam is by far reduced as compared with the conventional devices.