Apparatus for controlling semiconductor laser operating temperature

Claim 2

An apparatus as set forth in claim 1, wherein said temperature control element is formed by a Peltier element, a predetermined current being delivered from said temperature control means to said Peltier element on the basis of a detection signal.

Claim 3

An apparatus as set forth in claim 1, wherein said laser beam detection means comprises a first detector for detecting a laser beam reflected from a filter which transmits only a light beam of a specific wavelength to output a first detection signal and a second detector for detecting laser beams transmitted through the filter to output a second detection signal, said temperature control means discriminating a shift of a wavelength of the laser beam emitted from the semiconductor laser on the basis of a change of the first and second detection signals to control the temperature control element.

Claim 4

An apparatus as set forth in claim 1, wherein said laser beam detection means includes a wavelength detection/comparison unit for detecting a wavelength of a laser beam emitted from a backward cleavage plane of said semiconductor laser to compare a wavelength of the detected laser beam with a reference wavelength.

Claim 5

An apparatus as set forth in claim 4, wherein said unit comprises: a plurality of filters to receive a laser beam emitted from said semiconductor laser to emit laser beams having different wavelenghs to be transmitted therethrough; a plurality of photo-diodes to detect said laser beams emitted from said plurality of filters to apply photoelectric conversion thereto; a calculation unit for calculating a difference between respective electric signals from said plurality of photo-diodes; and a comparison unit for making a comparison between a calculated result by said calculation unit and a reference value set in advance to output a control signal to control said temperature control means.

Claim 6

An apparatus as set forth in claim 4, wherein said wavelength detection/comparison unit comprises: a filter for reflecting and transmitting the laser beam emitted from said semiconductor laser; two photo-diodes to detect a reflected laser beam and a transmitted laser beam, respectively; a calculation unit for calculating a difference between respective electric signals from the photo-diodes; and a comparison unit for making a comparison between a calculated result by said calculation unit and a reference value set in advance to output a control signal to control said temperature control means.

Claim 7

An apparatus as set forth in claim 4, wherein said wavelength detection/comparison unit comprises: spectral means for emitting a laser beam from the backward cleavage plane of said semiconductor laser at an emission angle varying in correspondence with a wavelengh of said laser beam; photodetector means adapted to detect a laser beam emitted from said spectral means at positions varying in dependence on the wavelengh thereof; and a comparison unit for making a comparison between an output from said photodetector means and a reference value set in advance to output a control signal to control said temperature control means.

Claim 8

An apparatus as set forth in claim 7, wherein said spectral means comprises a reflective diffraction grating, and said photodetector means comprises a line sensor.

Claim 9

An apparatus as set forth in claim 7, wherein said spectral means comprises a prism and a converging lens, and said photodetector means comprises a line sensor.

Claim 10

An apparatus as set forth in claim 4, wherein said wavelength detection/comparison unit comprises: a transmissive diffraction grating for transmitting and diffracting the laser beam from the semiconductor laser therethrough; a plurality of photo-diodes to detect the laser beams emitted from the transmissive diffraction grating, a calculation unit for calculating a difference between respective electric signals from said plurality of photo-diodes; and a comparison unit for making a comparison between a calculated result by said calculation unit and a reference value set in advance to output a control signal to control said temperature control means.

Claim 11

An apparatus as set forth in claim 1, wherein said wavelength detection/comprison unit comprises: an electro optic crystal for emitting a circularly polarized laser beam in such a manner that an ordinary ray component or extraordinary ray component in a linearly polarized laser beam emitted from the backward cleavage plane of said semiconductor laser is shifted by λ/2; a Wollastone prism for separating said circularly polarized laser beam into an ordinary ray component and an extraordinary ray component to emit them; photo-diodes for detecting said respective separated laser beams to apply photo electric conversion thereto; a calculation unit for calculating a difference between respective electric signals outputted from said photo-diodes; a voltage control unit for outputting, to said electro optic crystal, such a voltage to allow a difference signal outputted from said calculation unit to have "0" level; and a comparison unit for comparing an output from said voltage control unit with a reference value set in advance to output a control signal.

Claim 12

An apparatus as set forth in claim 1, wherein said semiconductor laser is a light source of an optical pick-up for recording information onto a recording medium and reproducing it therefrom.