Laser driving apparatus
View Patent ↗Laser driving apparatus in which a temperature is controlled such that an optical output is maximum, even when a laser device using an optical wavelength conversion element is used in a backlight source of a liquid crystal display that adjusts light dynamically. Current detection section 5 detects an average value of a driving current by which laser device 1 is pulse-driven. Optical detection section 3 detects an average value of an optical output from laser device 1 . Efficiency detection section 9 calculates a ratio of an output from optical detection section 3 to an output from current detection section 5 . A temperature setting value at which an efficiency value which is a result of the computation is maximum is provided to temperature control section 7 and a temperature of nonlinear optical crystal 12 of laser device 1 is controlled, whereby laser device 1 is driven such that the optical output from laser device 1 is always maximum.
1. A laser driving apparatus comprising:
a laser device that includes an excitation laser unit that emits excited laser light and an optical wavelength conversion element that converts the excited laser light, as a fundamental wave, to laser light having a predetermined wavelength, and that emits the laser light, as an optical output, whose wavelength is converted by the optical wavelength conversion element;
a driving section that drives the excitation laser unit of the laser device by a pulse current;
an optical detecting section that detects an average value of the optical output in a pulse form emitted from the laser device and outputs the average value as an optical detection value;
a current detecting section that detects a value corresponding to an average value of the pulse current and outputs the value as a current detection value;
an efficiency detecting section that outputs, as an efficiency value, a value obtained by dividing the optical detection value by the current detection value;
a maximization control section that receives as input the efficiency value and derives a temperature setting value such that the efficiency value is maximum;
a temperature control section that controls a temperature of the optical wavelength conversion element to reach the temperature setting value;
wherein the maximization control section holds in advance a characteristic of the efficiency value for the temperature setting value and sets, as Tm, the temperature setting value at which the efficiency value in the characteristic is maximum, then the maximization control section first outputs a temperature setting value T 1 which is lower or higher than Tm by a predetermined temperature, sets, as T 2 , a temperature setting value obtained by applying an efficiency value input as a result of outputting the temperature setting value T 1 to the characteristic, and derives Tm+(T 1 −T 2 ) as a temperature setting value at which the efficiency value is maximum.
2. A laser driving apparatus comprising:
a laser device that includes an excitation laser unit that emits excited laser light and an optical wavelength conversion element that converts the excited laser light, as a fundamental wave, to laser light having a predetermined wavelength, and that emits the laser light, as an optical output, whose wavelength is converted by the optical wavelength conversion element;
a driving section that drives the excitation laser unit of the laser device by a pulse current;
an optical detecting section that detects an average value of the optical output in a pulse form emitted from the laser device and outputs the average value as an optical detection value;
a current detecting section that detects a value corresponding to an average value of the pulse current and outputs the value as a current detection value;
an efficiency detecting section that outputs, as an efficiency value, a value obtained by dividing the optical detection value by the current detection value;
a maximization control section that receives as input the efficiency value and derives a temperature setting value such that the efficiency value is maximum;
a temperature control section that controls a temperature of the optical wavelength conversion element to reach the temperature setting value;
wherein the maximization control section first receives as input an efficiency value E 0 for a current temperature setting value T 0 , then outputs a temperature setting value T 0 +ΔT obtained by changing the temperature setting value T 0 by a micro value ΔT and receives as input an efficiency value E 1 , either holds T 0 +ΔT as the temperature setting value or resets the temperature setting value to T 0 and holds T 0 , based on a result of a comparison between E 1 and E 0 , thereby deriving a temperature setting value at which the efficiency value is maximum.
3. A laser driving apparatus comprising:
a laser device that includes an excitation laser unit that emits excited laser light and an optical wavelength conversion element that converts the excited laser light, as a fundamental wave, to laser light having a predetermined wavelength, and that emits the laser light, as an optical output, whose wavelength is converted by the optical wavelength conversion element;
a driving section that drives the excitation laser unit of the laser device by a pulse current;
an efficiency detecting section that detects an amplitude value of the optical output in a pulsed form emitted from the laser device and outputs the amplitude value as an efficiency value;
a maximization control section that receives as input the efficiency value and derives a temperature setting value such that the efficiency value is maximum; and
a temperature control section that controls a temperature of the optical wavelength conversion element to reach the temperature setting value;
wherein the maximization control section holds in advance a characteristic of the efficiency value for the temperature setting value and sets, as Tm, the temperature setting value at which the efficiency value in the characteristic is maximum, then the maximization control section first outputs a temperature setting value T 1 which is lower or higher than Tm by a predetermined temperature, sets, as T 2 , a temperature setting value obtained by applying an efficiency value input as a result of outputting the temperature setting value T 1 to the characteristic, and derives Tm+(T 1 −T 2 ) as a temperature setting value at which the efficiency value is maximum.
4. A laser driving apparatus comprising:
a laser device that includes an excitation laser unit that emits excited laser light and an optical wavelength conversion element that converts the excited laser light, as a fundamental wave, to laser light having a predetermined wavelength, and that emits the laser light, as an optical output, whose wavelength is converted by the optical wavelength conversion element;
a driving section that drives the excitation laser unit of the laser device by a pulse current;
an efficiency detecting section that detects an amplitude value of the optical output in a pulsed form emitted from the laser device and outputs the amplitude value as an efficiency value;
a maximization control section that receives as input the efficiency value and derives a temperature setting value such that the efficiency value is maximum;
a temperature control section that controls a temperature of the optical wavelength conversion element to reach the temperature setting value;
wherein the maximization control section first receives as input an efficiency value E 0 for a current temperature setting value T 0 , then outputs a temperature setting value T 0 +ΔT obtained by changing the temperature setting value T 0 by a micro value ΔT and receives as input an efficiency value E 1 , either holds T 0 +ΔT as the temperature setting value or resets the temperature setting value to T 0 and holds T 0 , based on a result of a comparison between E 1 and E 0 , thereby deriving a temperature setting value at which the efficiency value is maximum.