Pentax Corporation

Asahi Kogaku Kogyo Kabushiki Kaisha

Shoji Iwazaki

Mitsunori Iima

Tadashi Minakuchi

Toshimitsu Saito

A multi-beam scanning device includes a light source for emitting a plurality of laser beams, a polygon mirror for deflecting the laser beams so that the laser beams scan across an object surface in a main scanning direction, an f&#x3b8; lens disposed between the polygon mirror and the object surface, and a cylindrical lens that converges each laser beam in a vicinity of the polygon mirror in the auxiliary direction. A mirror is disposed between the light source and the cylindrical lens which deflects the laser beams in the auxiliary scanning direction. The mirror is rotatably supported by a mirror holder such that the traveling direction of the laser beams deflected by the mirror can be adjusted.

Multi-beam scanning device

A drive control circuit for an electromagnetic driving device includes a magnet and a drive coil, which moves due to an electromagnetic force when an electrical current flows therethrough. The drive control circuit may include (1) a drive circuit that feeds an electrical current to the drive coil, the drive circuit including at least one voltage source, and (2) a short-circuit system that short-circuits the drive coil. The short-circuit system releases the short-circuited condition of the drive coil in accordance with an output voltage of the at least one voltage source.

Electromagnetic drive control device

A semiconductor laser device comprises a semiconductor laser, a photo-diode, a first input terminal and a second input terminal. A sample hold circuit, having a first switch and a capacitor, is provided between the first input terminal and the semiconductor laser. A second switch is provided between the second input terminal and the semiconductor laser. A drive current is supplied to the semiconductor laser based on a light radiation level command signal input to the first input terminal. A constant current is generated based on a signal input through the second input terminal. In a sampling mode, the first and second switches are turned ON, and thus, a control current, which is obtained by subtracting the constant current from the drive current, is sampled by the sample hold circuit. In a holding mode, one of a bias current, obtained based on the control current and the constant current, or the drive current are supplied to the semiconductor laser, in accordance with ON/OFF of the second switch.

Semiconductor laser drive device

A laser beam emitting device includes a laser diode, a drive current supply circuit, a laser power detection circuit, a first differential amplifier that outputs a first differential signal corresponding to a difference between the laser power detection signal and a reference value. A laser diode deterioration detection circuit includes a biasing circuit that modifies the laser power detection signal or the reference value upon issuance of deterioration detection command. A sample-hold circuit samples and holds the first differential signal just before the deterioration detection command is issued. A second differential amplifier outputs a second differential signal corresponding to a difference between the first differential signal after the deterioration detection command is issued and the signal held by said sample-hold circuit. A deterioration determining circuit compares the second differential signal and a deterioration detection reference value, and determines whether the laser diode is deteriorated based on the comparison result.

Laser diode deterioration detecting device

A laser modulating device is provided with a monitoring system that outputs a detection voltage signal corresponding to the output power, a minimum output level setting system that outputs a minimum level voltage signal, a modulating voltage signal generating system, a first adder that outputs a reference voltage signal corresponding to a sum of the minimum level voltage signal and the modulating voltage signal, a comparing system that outputs a driving voltage signal corresponding to a difference between the reference voltage signal and the detection voltage signal, a first V/I converting system that converts the driving voltage signal to a first driving current, the first driving current being supplied to the laser diode, a second V/I converting system, and a circuit that directly supplies the modulating voltage signal from the modulating voltage signal generating system to the second voltage to current converting system, the second voltage to current converting system converting the modulating voltage signal into a second driving signal, the second driving signal being supplied to the laser diode.

Laser modulating device

In a light power modulating system for modulating output power of a laser diode, an output power of the laser diode is monitored and a voltage signal corresponding to the detected output power is output. An image signal output system is provided to form an image signal representative of a thickness density of an image to be formed, and a modifying system modifies the image signal such that a changing rate of the image signal between a lower value and a higher value is lowered. A differential amplifier outputs an amplified difference between the modified image signal and the voltage signal, and a driving current to be supplied to the laser diode is generated based on the amplified difference output by the differential amplifier.

Growing community of inventors

Tokyo, Japan

Shoji Iwazaki