Device and method for recording distance-measuring images
A recording device for distance images becomes multi-target-enabled by means of the arrival of light pulses reflected at object regions at different distances being temporally resolved. This is done using extrema of the gradient of a correlation function between the received light pulses and a time window during which sensor elements of a camera are activated.
1. A device for recording distance-measuring images, comprising:
a light source to emit light pulses;
a photodetector to integrate a light stream of a light pulse, wherein the light stream is reflected on an object region via a time window whose time interval is variable in relation to the process of emission of the light pulse, into a multiplicity of light quantity values; and
an evaluation unit to determine a distance to the object region based upon a correlation function formed by the light quantity values,
wherein the evaluation unit determines extreme values of a gradient of the correlation function and determines therefrom the distances of differently distant object regions,
wherein the evaluation unit determines the position of the extreme values of the gradient based upon a difference function of the correlation function, and
wherein the difference function contains the differences between a determined value of the correlation function and an adjacent value of the correlation function.
2. The device as claimed in claim 1 , wherein the evaluation unit is connected downstream of the photodetector.
3. The device as claimed in claim 1 , wherein a duration of the emitted light pulses is less than or equal to the time which light needs for covering a distance difference to be resolved.
4. The device as claimed in claim 1 , wherein the time interval between the process of emission of the light pulse and the time window are varied by time spans which are less than the half-amplitude duration of the emitted light pulse.
5. The device as claimed in claim 1 , wherein the time interval between the determined value and the adjacent value of the correlation function is less than double the half-amplitude duration of the emitted light pulses.
6. The device as claimed in claim 1 , wherein the time interval between the determined value and the adjacent value of the correlation function is greater than or equal to half the half-amplitude duration of the emitted light pulses.
7. The device as claimed in claim 1 , wherein the device has an intermediate memory to file the values of the correlation function for processing by the evaluation unit.
8. The device as claimed in claim 1 , wherein pairs of adjacent sensor elements respectively have offset time windows, and wherein a difference-forming unit connected downstream determines the values of the difference function.
9. The device as claimed in claim 1 , wherein the emitted light pulses and the reflected light pulses respectively pass through a protective surface arranged in front of the light source, and in front of the photodetector, wherein the evaluation unit monitors for interfering reflective objects.
10. The device as claimed in claim 1 , wherein the evaluation unit generates a distance-measuring image with enhanced resolution, wherein the evaluation unit subdivides image elements which map a plurality of differently distant object regions and assigns the partial areas to the adjacent image elements according to their distance values.
11. The device as claimed in claim 1 , wherein the evaluation unit generates a distance-measuring image with enhanced resolution, wherein the evaluation unit adapts the distance-measuring image to a model of a previously known object region.
12. The method as claimed in claim 1 , wherein the correlation function is determined by the light-propagation-time-measuring device based upon a short-term integration.
13. The method as claimed in claim 12 , wherein partially concealed objects are detected.
14. A method for recording distance-measuring images, comprising:
determining a correlation function between light pulses reflected on an object region and a time window of a light-propagation-time-measuring device; and
determining the distances of differently distant object regions based upon extreme values of a gradient of the correlation function,
wherein the extreme values of the gradient of the correlation function are determined based upon extreme values of a difference function derived from the correlation function, and
wherein the difference function contains the differences between a determined value of the correlation function and an adjacent value of the correlation function.
15. The method as claimed in claim 14 , wherein partially concealed objects are detected.