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 ( 10 ) to create the beams, and one or more optical detectors ( 30 ) 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 locating an opaque object in a target region, by detecting interruption of light beams, comprising one or more optical emitters arranged to create light beams, and one or more optical detectors arranged to provide detection signals, said detectors arranged to use emission wavelengths which are compatible with night vision apparatus, and having an NVIS radiance smaller than 1.7×10 −11 NR when measured in accordance with the following equation:
NVIS radiance (NR)=G(λ) max ∫ 450 930 G(λ)SN(λ)dλ,
wherein G(λ) is a relative NVIS response of Class A or B equipment according to MIL-L-85762A, N(λ) is a spectral radiance of lighting component, S is a scaling factor, G(λ) max is 1 mA/W, and dλ is 5 nm.
2. The touchscreen of claim 1 , including drive circuitry arranged to modulate the emitters, and detection circuitry to detect the same modulation in the detection signals.
3. The touchscreen of claim 2 , wherein the detection circuitry of a given one of the touchscreens is synchronized to the drive circuitry.
4. The touchscreen of claim 3 , the detection circuitry having an integrator coupled to an output of a switching inverter, the switching inverter being arranged to switch between outputting an inverted or not 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 , said light beams 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 cutoff from 0% transparency below 1000 nm and at least 90% transparency above 1005 nm for incident angles larger than 85°.
11. A night vision imaging system comprising:
a touchscreen for locating an opaque object in a target region, by detecting interruption of light beams, comprising one or more optical emitters arranged to create light beams, and one or more optical detectors arranged to provide detection signals, said detectors arranged to use emission wavelengths having an NVIS radiance smaller than 1.7×10 −11 NR when measured in accordance with the following equation:
NVIS radiance (NR)=G(λ) max ∫ 450 930 G(λ)SN(λ)dλ,
wherein G(λ) is a relative NVIS response of Class A or B equipment according to MIL-L-85762A, N(λ) is a spectral radiance of lighting component, S is a scaling factor, G(λ) max is 1 mA/W, and dλ is 5 nm; and
at least one night vision goggle compatible with an NVIS radiance smaller than 1.7×10 −11 NR.
12. The night vision imaging system of claim 11 , further comprising at least one interference filter arranged in front of the one or more optical detectors.