Night vision touchscreen
A touchscreen system for locating an opaque object in a target region, detects interruption of light beams. Each of the touchscreens have one or more optical emitters to create the beams, and one or more optical detectors to provide detection signals arranged to use emission wavelengths which are compatible with night vision apparatus, and having an NVIS radiance smaller than 1.7×10 −11 NR.
1. A touchscreen for use with cameras, sights or night vision goggles, said Touchscreen being for locating an opaque object in a target region, by detecting interruption of light beams, the touchscreen comprising:
one or more optical emitters arranged to create said light beams, and one or more optical detectors arranged to provide detection signals, said optical emitters emitting wavelengths which do not interfere with said cameras, sights or goggles, whereby a substantial peak of the spectrum of the said optical emitters is not below 900 nm.
2. The touchscreen of claim 1 , further comprising drive circuitry arranged to modulate the optical emitters and detection circuitry to detect the same modulation in the detection signals.
3. The touchscreen of claim 2 wherein the detection circuitry is synchronized to the drive circuitry.
4. The touchscreen of claim 3 , wherein the detection circuitry comprises an integrator coupled to an output of a switching inverter, the switching inverter being arranged to switch between outputting an inverted or non-inverted version of a given detection signal, the switching being arranged to be in phase with the modulation of the corresponding emitters.
5. The touchscreen of claim 4 , the detection circuitry having a comparator arranged to compare an output of the integrator with one or more thresholds, to determine an interruption of the corresponding beam and therefore indicate a touch.
6. The touchscreen of claim 1 , including circuitry for controlling an emission power of the emitters according to an output of the detection circuitry.
7. The touchscreen of claim 1 , wherein said light beams are configured to cover a planar target area.
8. The touchscreen of claim 7 , wherein the emitters and detectors are mounted on a frame around the planar target area.
9. The touchscreen of claim 1 , further comprising at least one interference filter arranged in front of the one or more optical detectors.
10. The touchscreen of claim 9 wherein the at least one interference filter has a steep cut-off from 0% transparency below 1000 nm and at least 90% transparency above 1005 nm for angles larger than 85°.
11. The touchscreen of claim 9 further comprising means to guarantee that any light rays that are incident on the filter are at angles larger than 85 degrees.
12. The touchscreen of claim 11 wherein said means to guarantee that any light rays that are incident on the filter are at angles larger than 85 degrees comprises mechanical construction and components location.