Day/night viewing device with laser range finder utilizing two wavelengths of laser light, and method of its operation

A method of operating a viewing device, said method comprising steps of:

• providing a tube device for receiving light from a distant scene and utilizing said tube device to responsively providing an output;
• providing a laser having a temperature of operation and projecting laser light into the distant scene;
• utilizing the temperature of operation of said laser to control the wavelength of laser light produced by said laser, and controlling said temperature of operation of said laser substantially to a selected one of at least two differing temperatures, said laser providing laser light of a corresponding one of two differing wavelengths;
• providing at least a pair of optical band-pass filters each passing a respective wavelength of light corresponding to a respective one of said two differing wavelengths.

An observation device including a laser having a temperature of operation and projecting laser light into a scene to provide an image by operation of the device, the laser light having a wavelength dependent upon said temperature of operation of the laser;

• said observation device comprising:
• an objective lens receiving light from the scene;
• an image intensifier tube receiving light from the scene via the objective lens, and responsively providing a visible image;
• an eyepiece lens providing the visible image to a user of the device;
• said laser projecting pulses of laser light into the scene to illuminate this scene and provide an image;
• at least a duality of spectral band-pass optical filters selectively movable to pass light between said objective lens and said image intensifier tube;
• and
• heat control means responsive to ambient temperature to control said temperature of operation of said laser above ambient temperature to one of at least a duality of temperatures;
• whereby said operating temperature of said laser is controlled to one of said at least a duality of temperatures dependent upon ambient temperature in order to decrease heat loss from said laser and said heat control means to ambient.