Abstract: In recent years, it has been desired to further shorten the dead time. Provided is a driving device that drives on/off a main switching element to which a free wheeling diode is anti-parallel connected, wherein the driving device includes a determination unit configured to output a determination signal indicating whether free wheeling current is flowing from a source terminal to a drain terminal of the main switching element; and a drive control unit configured to reduce a switching speed when the main switching element is driven from an on-state to an off-state on condition that the determination signal indicating that the free wheeling current is flowing is output.

Abstract: A driving device is provided, which drives on/off a main switching element to which a diode is anti-parallel connected, wherein the driving device includes a detection unit configured to detect a voltage between a drain terminal and a source terminal; a determination unit configured to output a determination signal indicating whether a free wheeling current is flowing from the source terminal to the drain terminal based on a detected voltage detected by the detection unit; and a drive control unit configured to perform control such that the main switching element is set in an on-state on condition that an on command signal for turning on the main switching element is input and on condition that the determination signal indicating that the free wheeling current is flowing is output.

Abstract: A driving device is provided, which drives on/off a main switching element to which a diode is anti-parallel connected, wherein the driving device includes a detection unit configured to detect a voltage between a drain terminal and a source terminal; a determination unit configured to output a determination signal indicating whether a free wheeling current is flowing from the source terminal to the drain terminal based on a detected voltage detected by the detection unit; and a drive control unit configured to perform control such that the main switching element is set in an on-state on condition that an on command signal for turning on the main switching element is input and on condition that the determination signal indicating that the free wheeling current is flowing is output.

Abstract: A driving apparatus is provided, the driving apparatus including: a gate driving unit that drives a semiconductor element; a sampling unit that samples, in an on-period of the semiconductor element, an observation value that changes according to an on-current flowing through the semiconductor element; and a changing unit that changes a driving condition under which the gate driving unit drives a gate of the semiconductor element when the semiconductor element is turned off according to the observation value sampled in an on-period of the semiconductor element.

Abstract: The optical level control device independently controls the intensities of two beams having different wavelengths that are emitted from a laser oscillator, and the optical level control device includes a wavelength-dependent wavelength plate and a polarization beam splitter. The wavelength-dependent wavelength plate functions as a half-wave plate with respect to the first light wave and as a full-wave plate with respect to the second light wave. Only the rotation angle of the polarization beam splitter about the optical axis is adjusted to set the intensity of the second light wave transmitted rectilinearly through the polarization beam splitter. The polarization beam splitter is then fixed at the adjusted angle, and the rotation angle of the wavelength plate about the optical axis is adjusted to set the intensity of the first light wave.

Abstract: The optical level control device independently controls the intensities of two beams having different wavelengths that are emitted from a laser oscillator, and the optical level control device includes a wavelength-dependent wavelength plate and a polarization beam splitter. The wavelength-dependent wavelength plate functions as a half-wave plate with respect to the first light wave and as a full-wave plate with respect to the second light wave. Only the rotation angle of the polarization beam splitter about the optical axis is adjusted to set the intensity of the second light wave transmitted rectilinearly through the polarization beam splitter. The polarization beam splitter is then fixed at the adjusted angle, and the rotation angle of the wavelength plate about the optical axis is adjusted to set the intensity of the first light wave.

Abstract: The optical level control device independently controls the intensities of two beams having different wavelengths that are emitted from a laser oscillator, and the optical level control device comprises a wavelength-dependent wavelength plate and a polarization beam splitter. The wavelength-dependent wavelength plate functions as a half-wave plate with respect to the first light wave and as a full-wave plate with respect to the second light wave. Only the rotation angle of the polarization beam splitter about the optical axis is adjusted to set the intensity of the second light wave transmitted rectilinearly through the polarization beam splitter. The polarization beam splitter is then fixed at the adjusted angle, and the rotation angle of the wavelength plate about the optical axis is adjusted to set the intensity of the first light wave.

Abstract: The optical level control device independently controls the intensities of two beams having different wavelengths that are emitted from a laser oscillator, and the optical level control device comprises a wavelength-dependent wavelength plate and a polarization beam splitter. The wavelength-dependent wavelength plate functions as a half-wave plate with respect to the first light wave and as a full-wave plate with respect to the second light wave. Only the rotation angle of the polarization beam splitter about the optical axis is adjusted to set the intensity of the second light wave transmitted rectilinearly through the polarization beam splitter. The polarization beam splitter is then fixed at the adjusted angle, and the rotation angle of the wavelength plate about the optical axis is adjusted to set the intensity of the first light wave.

Abstract: There is provided an optical head including a laser diode chip, a lens for focusing lights onto an object, an optical separator for separating lights reflected from the object, from an optical axis of a light directing towards the lens from the laser diode chip, and a photodiode chip receiving lights having been separated from the optical axis by the optical separator. The optical separator is defined by first and second sidewalls, and first to fourth outer surfaces, and has first and second inner planes both being inclined relative to the first outer surface. A light enters the first outer surface, passes through the first and second inner planes, leaves the optical separator at the third outer surface, and is focused onto the object by the lens. The light having been reflected by the object enters the third outer surface, and is reflected at the second inner plane by the remaining half.

Abstract: Disclosed is an optical head, which has: a light generator which emits linearly polarized light; a lens which converges the light emitted from the light generator on a medium; a light detector which receives the light reflected on the medium; a quarter-wave plate which is disposed between the light generator and the lens and rotates by .pi.

Abstract: Disclosed is a focusing error detecting equipment, which has a light-generating device; an image-forming device for converging light to be emitted from the light-generating means upon a focusing error detected object; a diffraction element for diffracting light to be reflected on the focusing error detected object; and a light-detecting device for receiving lights to be separated by the diffraction element; wherein the diffraction element is divided into four regions a, b, c and d by a boundary plane .alpha. and a boundary plane .beta., the regions a and c to be located diagonally diffracting the reflected light into lights with a convergence point before the light-detecting device and the regions b and d to be located diagonally diffracting the reflected light into lights with a convergence point behind the light-detecting device, the light-detecting device has light-receiving parts ea and eb which are divided by a division line e parallel with the boundary plane .alpha.

Abstract: The optical head has a radiating light source for emitting a beam, and a finite lens for focusing the beam onto a recording medium, and a slab type waveguide for guiding light. The optical head includes a holographic coupler and a plurality of photo-detectors. The holographic coupler which lacks a lens effect is provided in the slab type waveguide between the radiating light source and the finite lens. The holographic coupler transmits the beam going from the radiating light source toward the finite lens and diffracts a beam returning from the finite lens toward the radiating light source after being reflected at the recording medium. The photo-detectors detect the beam which is diffracted by the holographic coupler and coupled to and guided by the slab type waveguide. Since the holographic coupler does not have a lens effect, even if the wavelength of the light changes, there is no deviation of the position of the focused point from the optical axis within the slab type waveguide.

Abstract: An optical head includes a beam-generator, a slab type waveguide, an output hologram coupler, a focal lens, an input hologram coupler, and a photoelectric transducer. The slab type waveguide has a cladding, and a first core and a second core formed on opposite side surfaces of the cladding. The output hologram coupler is provided on the slab type waveguide for decoupling a beam emitted from the beam-generator and guided through the second core. The focal lens focuses a beam decoupled in the output coupler and transmitted through the cladding and the first core onto an optical recording medium. The input hologram coupler is provided on the slab type waveguide for coupling to the first core a beam reflected from the optical recording medium and led to the lens. The photoelectric transducer detects the beam coupled to the input coupler and guided through the first core.

Abstract: It is the object of the invention to provide an optical head, which can be assembled with high accuracy and operates with high stability. A laser diode is fixed on a heat sink, which is fixed on the photodiode chip. The laser diode chip emits the light in the both forward and backward directions. A mirror, which reflects the forward emitted light, are formed on a heat sink. The forward emitted light is reflected by the mirror, passes through a holographic optical element and a lens, and is focused on an optical disc (not shown). The reflected light from the optical disc proceeds along the same path in the opposite direction, is diffracted by the holographic optical element, and detected by the light detecting portions 2a to 2h on the photodiode chip. In order to control an injection current and keep the power of the emitted light constant, the backward emitted light is detected by the light detecting portion 2i on a photodiode chip 2.