Device and method for spatially resolved photodetection and demodulation of modulated electromagnetic waves
View Patent ↗A device and method for spatially resolved photodetection and demodulation of temporally modulated electromagnetic waves makes it possible to measure phase, amplitude and offset of a temporally modulated, spatially coded radiation field. A micro-optical element ( 41 ) spatially averages a portion ( 30 ) of the scene and equally distributes the averaged intensity on two photo sites ( 51.1.51.2 ) close to each other. Adjacent to each of these photo sites ( 51.1 ) are two storage areas ( 54.1, 54.2 ) into which charge from the photo site can be moved quickly (with a speed of several MHz to several tens or even hundreds of MHz) and accumulated essentially free of noise. This is possible by employing the charge-coupled device (CCD) principle. The device combines a high optical fill factor, insensitivity to offset errors, high sensitivity even with little light, simultaneous data acquisition, small pixel size, and maximum efficiency in use of available signal photons for sinusoidal as well as pulsed radiation signals. The device and method may be used in a time-of-flight (TOF) range imaging system without moving parts, offering 2D or 3D range data.
1. A device for spatially resolved photodetection and demodulation of temporally modulated electromagnetic waves, comprising:
a one-dimensional or two-dimensional array of pixels ( 50 ), each pixel ( 50 ) comprising:
at least two transducer elements ( 51 . 1 , 51 . 2 ) for transducing incident electromagnetic radiation into an electric signal, each transducer element ( 51 . 1 , 51 . 2 ) being associated with:
at least one storage element ( 54 . 1 – 54 . 4 ) for storing said electric signal, said at least one storage element ( 54 . 1 – 54 . 4 ) being inaccessible or insensitive to incident electromagnetic radiation;
wherein each pixel ( 50 ) comprises an optical element ( 41 ) for spatially averaging the electromagnetic radiation incident on the pixel ( 50 ) and equally distributing the averaged electromagnetic radiation onto said transducer elements ( 51 . 1 , 51 . 2 ) of the pixel ( 50 ).
2. The device according to claim 1 , wherein said optical element ( 41 ) comprises at least one of a refractive element and a diffractive optical element.
3. The device according to claim 1 , wherein each pixel ( 50 ) has two transducer elements ( 51 . 1 , 51 . 2 ).
4. The device according to claim 1 , wherein each transducer element ( 51 . 1 ) is associated with two storage elements ( 54 . 1 , 54 . 2 ).
5. The device according to claim 1 , wherein said arrangement of pixels ( 50 ) is realized in CCD or in CMOS-APS/CCD technology.
6. A method for spatially resolved photodetection and demodulation of temporally modulated electromagnetic waves, comprising the steps of:
impinging electromagnetic radiation onto a one-dimensional or two-dimensional array of pixels ( 50 );
spatially averaging the electromagnetic radiation incident on each pixel ( 50 );
equally distributing the averaged electromagnetic radiation onto at least two transducer elements ( 51 . 1 51 . 2 ) of the pixel ( 50 );
transducing the equally distributed averaged electromagnetic radiation incident on each pixel ( 50 ) into at least two electric signals in at least two transducer elements ( 51 . 1 , 51 . 2 ); and,
storing each of said at least two electric signals in at least one storage element ( 54 . 1 – 54 . 4 ).
7. The method according to claim 6 , wherein said at least two transducer elements ( 51 . 1 , 51 . 2 ) of a pixel ( 50 ) are operated with a 90° phase shift with respect to each other.
8. The method according to claim 6 , wherein each pixel ( 50 ) is addressed and read out individually.