Method and apparatus for generating an infrared illumination beam with a variable illumination pattern

An apparatus for illuminating a scene to be imaged with infrared (IR) radiation, comprising:

• (a) at least two IR emitters, including a first IR emitter operable to emit a wide beam component of the IR beam, and a second IR emitter operable to emit a narrow beam component of the IR beam, wherein the wide beam component has a linear profile that has a lower standard deviation than a linear profile of the narrow beam component;
• (b) at least two current drivers, including a first current driver coupled to the first IR emitter, and a second current driver coupled to the second IR emitter;
• and
• (c) processing circuitry communicative with the current drivers to instruct each current driver to deliver a selected amount of power to the coupled IR emitter, and comprising a processor and a memory having encoded thereon:
• (i) a beam profile-to-focal length map comprising a series of focal length increments and their corresponding power ratios, wherein each power ratio is a ratio of power directed to the first IR emitter and power directed to the second IR emitter that produces an IR beam with a desired linear profile for the corresponding focal length increment when the narrow beam component and wide beam component are combined;
• and
• (ii) program code executable by the processor to select a power ratio for a determined current focal length by selecting from the beam profile-to-focal length map the power ratio corresponding to the focal length increment matching the determined current focal length:
• and control the current drivers to direct power to the first and second IR emitters at the selected power ratio to generate the wide and narrow beam components and combine the generated wide and narrow beam components.

A method for generating a beam profile-to-focal length map for use in an apparatus that illuminates a scene with an infrared (IR) beam composed of a wide beam component and a narrow beam component, wherein the apparatus comprises at least a first IR emitter operable to emit the wide beam component and a second IR emitter operable to emit the narrow beam component, and wherein the wide beam component has a linear profile that has a lower standard deviation than a linear profile of the narrow beam component;

• the method comprising:
• (a) for each focal length increment in a group of focal length increments, determining a suitable wide beam-to-narrow beam power ratio of power directed to the first IR emitter and power directed to the second IR emitter that produces an IR beam with a desired linear profile for the focal length increment when the narrow beam component and wide beam component are combined;
• and
• (b) storing the determined suitable wide-beam-to-narrow-beam power ratio and corresponding focal length increment in a database readable by the apparatus.

An apparatus for illuminating a scene to be imaged with infrared (IR) radiation, comprising:

• (a) at least two IR emitters, including a first IR emitter operable to emit a wide beam component of the IR beam, and a second IR emitter operable to emit a narrow beam component of the IR beam, wherein the wide beam component has a linear profile that has a lower standard deviation than a linear profile of the narrow beam component;
• (b) at least two current drivers, including a first current driver coupled to the first IR emitter, and a second current driver coupled to the second IR emitter;
• and
• (c) processing circuitry communicative with the current drivers to instruct each current driver to deliver a selected amount of power to the coupled IR emitter, and comprising a processor and a memory having encoded thereon program code for generating a beam profile-to-focal length map, and for using the map to instruct the IR emitters to produce an IR beam with a suitable wide beam-to-narrow beam power ratio of power directed to the first IR emitter and power directed to the second IR emitter, wherein the program code for generating the map comprises:
• (i) for each focal length increment in a group of focal length increments, determining a wide beam-to-narrow beam power ratio that produces an IR beam with a desired linear profile for the focal length increment when the narrow beam component and wide beam component are combined and selecting this determined power ratio as the suitable wide beam-to-narrow beam power ratio;
• and
• (ii) storing the suitable wide beam-to-narrow beam power ratio and corresponding focal length increment in a database readable by the processing circuitry.