Method of and apparatus for stabilizing output light of a current modulation laser device whose output is changed by changing an anode current

Claim 1

A method of stabilizing output light of a current modulation laser device whose output is changed by changing an anode current, comprising detecting a part of a laser output light and converting that part of the laser output light which is detected into an electric signal, comparing said electric signal with a modulating input signal to obtain an analog signal corresponding to a difference between said two signals, controlling a gain of said modulating input signal by means of said analog signal, and feeding back said gain controlled modulating input signal to an input terminal of a laser device, whereby the output light of said laser device is made proportional to said modulating current, said input signal being a picture signal, said input signal having a random-shaped waveform, said input signal being modified by an amount opposite in direction to the amount detected in said comparing step, said current changing the laser output monotonously, said output being correspondingly variable with said input signal.

Claim 2

A method of stabilizing output light of a current modulation laser device whose output is changed by changing an anode current, comprising detecting a part of a laser output light and converting that part of the laser output light which is detected into an electric signal, comparing said electric signal with a modulating input signal to obtain an analog signal corresponding to a difference between said two signals, controlling a gain of said modulating input signal by means of said analog signal, and feeding back said gain controlled modulating input signal to an input terminal of a laser device, whereby the output light of said laser device is made proportional to said modulating current, said input signal being a picture signal, said input signal having a random-shaped waveform, said input signal being modified by an amount opposite in direction to the amount detected in said comparing step, said current changing the laser output monotonously, said output being correspondingly variable with said input signal.

Claim 3

An apparatus for stabilizing output light of a current modulation laser device whose output is changed by changing an anode current, comprising a current modulation laser device including a direct current supply source connected to an anode for supplying discharge current to the laser, resistors connected in series with the direct current supply source and a switching transistor connected in parallel with one of the resistors, said switching transistor being controlled by an input modulating signal supplied to an input terminal so as to control an anode current within a range from a first current value at which the laser output light becomes a maximum to a second current value which is larger than said first current value, whereby the intensity of output light of the laser is modulated, a detector including a semi-reflecting mirror for reflecting a part of a laser output light and a photodiode for converting that part of the laser output light which is reflected by said semi-reflecting mirror into an electric signal, a comparison circuit connected to both said photodiode and an input terminal for receiving a modulating input signal and for comparing said electric signal with said modulating input signal to obtain an analog signal corresponding to a difference between said two signals, and a gain control circuit connected between said input terminal and the output of said comparison circuit and for controlling a gain of said modulating input signal by means of said analog signal, whereby the output light of said laser device is made proportional to said modulating input signal, said input signal being a picture signal, said input signal having a random-shaped waveform, said input signal being modified by an amount opposite in direction to the amount detected in said comparing step, said current changing the laser output monotonously, said output being correspondingly variable with said input signal.

Claim 4

An apparatus for stabilizing output light of a current modulation laser device whose output is changed by changing an anode current, comprising a current modulation laser device including a direct current supply source connected to an anode for supplying discharge current to the laser, resistors connected in series with the direct current supply source and a switching transistor connected in parallel with one of the resistors, said switching transistor being controlled by an input modulating signal supplied to an input terminal so as to control an anode current within a range from a first current value at which the laser output light becomes a maximum to a second current value which is larger than said first current value, whereby the intensity of output light of the laser is modulated, a detector including a semi-reflecting mirror for reflecting a part of a laser output light and a photodiode for converting that part of the laser output light which is reflected by said semi-reflecting mirror into an electric signal, a comparison circuit connected to both said photodiode and an input terminal for receiving a modulating input signal and for comparing said electric signal with said modulating input signal to obtain an analog signal corresponding to a difference between said two signals, and a gain control circuit connected between said input terminal and the output of said comparison circuit and for controlling a gain of said modulating input signal by means of said analog signal, whereby the output light of said laser device is made proportional to said modulating input signal, said input signal being a picture signal, said input signal having a random-shaped waveform, said input signal being modified by an amount opposite in direction to the amount detected in said comparing step, said current changing the laser output monotonously, said output being correspondingly variable with said input signal.