A laser designator system using modulated CW laser diodes and a conventional high pixel count image sensor array, such as CCD or CMOS array. These two technologies, diode lasers and imaging sensor arrays are reliable, widely used and inexpensive technologies, as compared with prior art pulsed laser
A laser designator system using modulated CW laser diodes and a conventional high pixel count image sensor array, such as CCD or CMOS array. These two technologies, diode lasers and imaging sensor arrays are reliable, widely used and inexpensive technologies, as compared with prior art pulsed laser systems. These systems are distinguished from the prior art systems in that they filter the laser signal spatially, by collecting light over a comparatively long period of time from a very few pixels out of the entire field of view of the image sensor array. This is in contrast to the prior art systems where the laser signal is filtered temporarily, over a very short time span, but over a large fraction of the field of view. By spatially filtering the signal outputs of the individual pixels, it becomes possible to subtract the background illumination from the illuminated laser spot.
대표청구항▼
1. A method of imaging a field of view, the method comprising: illuminating the field of view by means of a continuous wave (CW) laser, modulated at a first rate to provide a stream of laser pulses; imaging the field of view using a multi-pixel sensor array;accumulating signals obtained from pixels
1. A method of imaging a field of view, the method comprising: illuminating the field of view by means of a continuous wave (CW) laser, modulated at a first rate to provide a stream of laser pulses; imaging the field of view using a multi-pixel sensor array;accumulating signals obtained from pixels of said multi-pixel sensor array during detection of a predetermined plurality of said laser pulses reflected from said field of view in a first set of pixel signal accumulators, to obtain from those pixels a first set of accumulated pixel signals arising from said predetermined plurality of said reflected laser pulses;reading out said first set of accumulated pixel signals to image said field of view, after completion of detection of said predetermined plurality of laser pulses; andrepeating the accumulating of signals obtained from pixels of said multi-pixel sensor array for further durations of said predetermined plurality of laser pulses, to obtain further sets of accumulated pixel signals, and reading out said further sets of accumulated pixel signals at a second rate significantly lower than said first rate. 2. The method according to claim 1, wherein said first rate is varied according to a predetermined coding scheme. 3. The method according to claim 1, wherein said accumulating is performed in charge registers of a multi-pixel CCD or CMOS array. 4. The method according to claim 1, wherein said first rate is higher than an expected environmental rate of change in said imaged field of view. 5. The method according to claim 4, where said expected environmental rate of change in said imaged field of view is that arising from any of natural movements, personnel movements, vehicular movements or atmospheric turbulence occurring in said field of view. 6. The method according to claim 1, wherein said second rate is sufficiently low that it is compatible with a frame rate of standard CCD or CMOS devices. 7. The method according to claim 1, wherein said second rate is in the tens of Hz. range. 8. The method according to claim 1, further comprising a step of accumulating signals obtained from said pixels of said multi-pixel sensor array in periods between the detection of laser pulses reflected from said field of view, in a second set of pixel signal accumulators, for said duration of said predetermined plurality of pulses, to obtain from those pixels of said multi-pixel sensor array a second set of accumulated pixel signals; and reading out said second set of accumulated pixel signals after completion of said predetermined plurality of pulses. 9. The method according to claim 8, wherein said first and said second sets of accumulated pixel signals are read out separately after completion of said predetermined plurality of pulses, at said second rate significantly lower than said first rate. 10. The method according to claim 8, wherein said first and second sets of pixel signal accumulators are sets of charge registers of an interlaced CCD or CMOS image sensor, with said first set being associated with charges collected from said pixels of said multi-pixel sensor array, arising from laser pulses reflected from said field of view and said second set being associated with charges collected from said pixels of said multi-pixel sensor array in periods between the detection of pulses reflected from said field of view. 11. The method according to claim 8, wherein said first and second sets of pixel signal accumulators are sets of charge registers of a CMOS or CCD image sensor, each pixel of said multi-pixel sensor array having two isolated charge sensors, with said first set being associated with charges collected from said pixels of said multi-pixel sensor array arising from laser pulses reflected from said field of view, and said second set being associated with charges collected from said pixels of said multi-pixel sensor array in periods between the detection of laser pulses reflected from said field of view. 12. The method according to claim 8, wherein said first and second sets of pixel signal accumulators are sets of adjacent charge registers of a progressive scan CMOS or CCD image sensor, the signal from each pixel of said multi-pixel sensor array being accumulated in either of said two sets of adjacent charge registers according to a shifted position of the vertical register, with said first set being associated with charges collected from said pixels of said multi-pixel sensor array arising from laser pulses reflected from said field of view, and said second set being associated with charges collected from said pixels of said multi-pixel sensor array in periods between detection of laser pulses reflected from said field of view. 13. The method according to claim 8, wherein said pixel signals accumulated in each of said first and second sets of pixel signal accumulators and read out therefrom, are subtracted, to generate image signals of said field of view in which an effect of background illumination is subtracted out. 14. The method according to claim 13, wherein said subtraction of the effect of background illumination enables a point of impingement of said stream of laser pulses to be determined in said image of said field of view, even if said background illumination dominates the intensity of said point of impingement of said stream of laser pulses. 15. The method according to claim 14, further comprising the step of: adding said signals accumulated in said first and second sets of signal accumulators and read out therefrom, to provide an additive image of said field of view; andimpressing on said additive image of said field of view, said image of said field of view with the point of impingement of said laser pulses accentuated therein, to obtain an indication of the position of impingement of said laser pulses on an image of said field of view. 16. The method according to claim 1, wherein said continuous wave (CW) laser is a diode laser. 17. A method for determining a range of an object, comprising: illuminating the object by means of a continuous wave (CW) laser, modulated at a first rate to provide a stream of transmitted laser pulses;imaging the field of view using a multi-pixel sensor array;accumulating signals obtained from pixels of said multi-pixel sensor array during detection of a predetermined plurality of said laser pulses reflected from said field of view at a second rate differing from the first rate by substantially less than either of said first and said second rates, to obtain from said pixels of said multi-pixel sensor array a first set of accumulated pixel signals arising from said predetermined plurality of said reflected laser pulses modulated at the rate equal to the difference between the first and second rates;reading out said first set of accumulated pixel signals after completion of said predetermined plurality of laser pulses;repeating said steps of accumulating and reading out for further durations of said predetermined plurality of pulses, to obtain further sets of accumulated pixel signals arising from said reflected laser pulses; said reading out of said further sets of accumulated pixel signals being performed at a rate significantly lower than that of said first rate;obtaining from said repeated accumulating and reading out, a train of image signal outputs of said object modulated at a rate equal to the difference between said first and second rates; anddetermining the range of said object from the difference in phase detected between said train of image signal outputs of said object and said modulated stream of transmitted laser pulses, said determining being performed at a rate equal to the difference between the first and second rates. 18. The method according to claim 17, wherein said difference between said first and second rates is sufficiently small that said phase difference can be measured electronically concurrently for millions of pixels of an imaging array. 19. The method according to claim 17, wherein said accumulating of pixel signals is performed in the charge registers of a multi-pixel CCD or CMOS array. 20. The method according to claim 17, wherein said reading out rate is sufficiently low that it is compatible with the frame rate of standard CCD or CMOS devices. 21. The method according to claim 17, wherein said second rate is in the tens of Hz. range. 22. The method according to claim 17, wherein said continuous wave (CW) laser is a diode laser.
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이 특허에 인용된 특허 (1)
Cameron Evan S. (Midland CAX) Szumski Ronald P. (Raleigh MI GB2) West James K. (Farmington Hills MI), Lidar scanning system.
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