Wavelength extension for backthinned silicon image arrays
View Patent ↗There is described a back thinned sensor in which a material is added on the front surface to extend the wavelength of the sensor into wavelengths it normally does not reach. In the preferred embodiment, the back-thinned layer comprises silicon and is the base for a CMOS device or a CCD. The photocathode in a night vision device comprises in the preferred unit GaAs.
1. An imaging device including a back-thinned silicon focal plane array, the improvement comprising positioning an up-converter layer on the front surface of said backside-thinned focal plane array.
2. A CCD with improved wavelength response comprising a back-thinned silicon surface layer, a focal plane array and an up-conversion layer positioned on the front surface of said array.
3. A CMOS imaging device with improved wavelength response comprising a back-thinned silicon surface layer, a focal plane array and an up-conversion layer positioned on the front surface of said focal plane array.
4. An imaging device in accordance with claim 3 in which a said back-thinned silicon surface layer is positioned in a package facing a photocathode across a vacuum and in which said up-conversion layer is selected to detect wavelengths in the range of ~1000 to 2000 nanometers.
5. An imaging device in accordance with claim 4 in which the CMOS includes active pixel sensors.
6. An imaging device in accordance with claim 4 in which the CMOS includes passive pixel sensors.
7. An imaging device in accordance with claim 4 in which the photocathode comprises GaAs.
8. An imaging device in accordance with claim 1 including an up-converter layer on the front surface of the back-thinned silicon focal plane array comprising a phosphor.
9. An imaging device in accordance with claim 8 in which the up-converting layer comprises two distinct phosphor layers, each having different wavelength responses.
10. An imaging device in accordance with claim 1 including a transparent cap overlying the up-converting material and said focal plane array.
11. An imaging device in accordance with claim 10 including a reflective layer adjacent to said transparent cap to reflect image information to said focal plane array.
12. An imaging device in accordance with claim 1 in which the focal plane array comprises a CMOS device.
13. A sensor in accordance with claim 12 in which a photocathode is spaced by a vacuum from said CMOS device with said photocathode facing said silicon surface layer of said CMOS device.
14. A sensor in accordance with claim 8 in which the output of the focal plane array is displayed as false colors.
15. The sensor of claim 1 in which the phosphor enables detection of an aiming beam at ~1.5 microns.
16. The sensor in accordance with claim 1 in which the up converter comprises a material having a sensitivity to light in the range of 1100 to 2000 nm and the capability to re-emit light in the 400–1100 nm range.
17. The method of extending the sensitivity of a back-thinned silicon layer of a focal plane array comprising placing an up-converting layer on the front surface of said focal plane array.
18. The method of claim 17 in which said focal plane array comprises active pixel sensors of a CMOS device.
19. The method of claim 17 in which pixels of said focal plane array are covered with up-conversion material in a predetermined pattern to create a sensor that outputs a signal that can be displayed in a false color image.
20. A sensor in accordance with claim 14 in which pixels of said focal plane array are coated in a predetermined pattern with an up-conversion material.
21. A sensor in accordance with claim 1 comprising at least a first type of up-conversion material positioned coating a fraction of the pixels of said imaging device.
22. A sensor in accordance with claim 21 in which another up-conversion material is positioned coating another fraction of the pixels of said imaging device in a predetermined pattern and in a pattern that differs from the pattern covered by said first type of up-conversion material.
23. A sensor in accordance with claim 1 including filters positioned covering a fraction of the pixels of said focal plane array in a regular pattern.
24. A sensor in accordance with claim 1 comprising a first coating of a fraction of the pixels with a first type of up-conversion material and an uncoated second fraction of the pixels are in a regular pattern.
25. A sensor in accordance with claim 1 in which filters are deposited on a fraction of the pixels in a predetermined pattern.
26. A sensor in accordance with claim 25 in which the filter comprises aluminum.
27. A sensor in accordance with claim 14 in which said phosphor is coated on a stacked photodiode pixilated sensor such that the output of the focal plane array can be displayed as a false-color image.