Programmable lens assemblies and optical systems incorporating them
View Patent ↗An imaging system ( 10 ) has a fixed lens combination ( 22 ), a spatial light modulator (SLM) ( 20 ) and a linear detector array ( 12 ). A scene image is scanned across a simple array ( 12 ) in a direction perpendicular to the array ( 12 ) by the SLM ( 20 ). This is achieved by displaying a diffraction pattern on the SLM that changes to achieve the scanning. The diffraction pattern displayed typically has a linear element ( 40 ) and a quadratic element (42). By having a programmably changed combined chirp pattern ( 36 ) displayed on the SLM, and by being able to change it thousands of times a second, an army with fast read out can take the place of a 2-D imaging array.
1. An optical assembly for observing a scene comprising an optical input to the assembly, said assembly comprising:
a spatial light modulator (SLM),
a controller controlling the display of the SLM, and
a detector; wherein the controller modifies a pattern displayed on the SLM to sequentially scan radiation from said observed scene across the detector, said radiation scanned from a plurality of different angular regions or depth regions in 3-D space of the scene or a surface region through the 3-D space that the optical assembly is observing, wherein the pattern displayed on the SLM has a component comprised of a substantially linear diffraction grating pattern and a component comprised of a substantially chirp function.
2. An assembly according to claim 1 in which the controller controls the SLM so as to scan different angular portions of the scene (angularly disposed in azimuth and/or ascension relative to the optical axis of the assembly).
3. An assembly according to claim 1 or claim 2 in which the controller controls the SLM so as to focus different depth regions of 3-D scene space over the detector.
4. An assembly according to claim 1 in which angular portions are scanned by modifying the linear component of a combined linear function and chirp function.
5. An assembly according to claim 1 in which different depth regions are focused by displaying patterns with different combined chirp functions.
6. An assembly according to claim 1 in which the controller has a library of possible linear and/or quadratic or higher order functions and a selected combination of linear and quadratic or higher order functions from the library are, in use, applied to the SLM.
7. An assembly according to claim 1 in which the detector comprises a line array of detector elements or a simple array of detector elements and the controller is adapted to control the display on the SLM to scan the scene image over the detector array in a direction generally transverse to the direction of the line array, or transverse to the elongate direction.
8. An assembly according to claim 1 in which the radiation from the selected surface or region in 3-D space in the scene is focused onto the detector.
9. An assembly according to claim 1 in which the pattern on the SLM is capable of being changed at least a thousand times a second.
10. An assembly according to claim 1 in which points in 3-D space are sequentially in time directed, or focused, onto a detector, the SLM being programmed by the controller to direct, or focus, different points in space onto the detector at different times.
11. A method of directing a scene image onto a detector comprising using a programmed SLM controlled by a controller to control the x-y part of the scene image that is directed onto the detector and/or the imaged plane of the scene in the z direction that is in focus, the direction between the scene and the detector being in the z direction, in which the display on the SLM is programmably controlled by a controller by application of a chirp and/or a linear grating to the SLM so as to scan the scene image over the detector over time, with the controller taking time-spaced records of what the detector detects.
12. A method according to claim 11 in which the orientation of a linear grating and/or the spacing of the lines of the grating are controlled so as to control the location of the region of the scene that is directed onto the detector.
13. A method according to claim 11 in which the chirp is used to determine the distance from the detector of the plane in 3-D space in the scene that is focused to the detector.
14. A method according to claim 11 in which the programmed SLM compensates for aberration in an optical system.