Image analysis apparatus

• US 20040151345A1
• Filed: 03/29/2004
• Published: 08/05/2004
• Est. Priority Date: 04/04/2001
• Status: Active Grant

• Current Assignee: Instro Precision Limited (S. Reisman Ltd.)
• Original Assignee: Instro Precision Limited (S. Reisman Ltd.)
• Inventors: Morcom, Christopher John
• Granted Patent: US 7,319,777 B2
• Time in Patent Office: Days
• US Class Current: 382/104
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/26 wherein the transmitted pulses use a frequency-modulated or phase-modulated carrier wave, e.g. for pulse compression of received signals
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/894 3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection
• CPC Class Codes: G01S 7/51 Display arrangements
• CPC Class Codes: G05D 1/024 in combination with a laser lasers per se H01S
• CPC Class Codes: G05D 1/0246 using a video camera in combination with image processing means
• CPC Class Codes: G05D 1/0248 in combination with a laser lasers per se H01S
• CPC Class Codes: G05D 1/027 comprising intertial navigation means, e.g. azimuth detector inertial navigation G01C21/16; inertial navigation combined with non-inertial navigation instruments G01C21/165
• CPC Class Codes: G05D 1/0272 comprising means for registering the travel distance, e.g. revolutions of wheels measuring distance traversed on the ground by vehicles, e.g. using odometers G01C22/00
• CPC Class Codes: G05D 1/0274 using mapping information stored in a memory device navigation using map-matching G01C21/30
• CPC Class Codes: G08G 1/166 for active traffic, e.g. moving vehicles, pedestrians, bikes
• CPC Class Codes: G08G 1/167 Driving aids for lane monitoring, lane changing, e.g. blind spot detection

Abstract

An Image analysis system uses a multiple-region light detector for detecting light received from the receiving optics, wherein different regions of the light detector can be actuated separately. Control electronics synchronises the timing and direction of illumination of the light source and the actuation of the light detector. The time of light of light signals from the light source to the actuated portion of the detector for all illuminated directions is measured, and distances are derived. A warning is generated if the derived distance is less than a predetermined threshold.

Claims

1. An image analysis system comprising:

a light source;

means for illuminating the field of view of interest with the light source;

receiving optics for receiving light reflected from the field of view to be analysed;

a multiple-region light detector for detecting light received from the receiving optics, wherein different regions of the light detector can be actuated separately;

control electronics to synchronise the timing and direction of illumination of the light source and the actuation of the light detector;

processing means for measuring the time of flight of light signals from the light source to the actuated portion of the detector for all illuminated directions and deriving distances from the times of flight; and

means for generating a warning if the derived distance is less than a predetermined threshold.

2. A system as claimed in claim 1, further comprising a speed sensor, and further comprising means for calculating a safe distance as the predetermined threshold based on the output of the speed sensor.

3. A system as claimed in claim 2, further comprising a road condition sensor, and wherein the safe distance is calculated based additionally on the road condition sensor output.

4. A system as claimed in any preceding claim, further comprising an image capture system capturing an image and displaying the image to a user, the field of view of which is aligned with the field of view of the two dimensional light detector.

5. A system as claimed in claim 4, wherein the two dimensional light detector is used as the detector for the image capture system.

6. A system as claimed in claim 4 or 5, further comprising means for modifying the image displayed by the image capture system in response to the derived distance.

7. A system as claimed in claim 6, wherein the image displayed by the image capture system is modified when a distance to a region of the image is less than the predetermined threshold distance.

8. A system as claimed in claim 7, wherein the image displayed by the image capture system is modified by changing the colour in parts of the image displayed corresponding to selected regions of the image to be analysed.

9. A system as claimed in any preceding claim, further comprising means for determining the trajectory of a body carrying the image analysis system.

10. A system as claimed in claim 6, 7 or 8, further comprising means for determining the trajectory of a body carrying the image analysis system, and wherein the output for modifying the image displayed by the image capture system is created only for regions of the image to be analysed lying within the trajectory of the body.

11. A system as claimed in claim 9 or 10, wherein the trajectory is obtained from speed and direction information.

12. A system as claimed in any one of claims 9 to 11, further comprising means for determining the distance to the nearest object within the trajectory.

13. A system as claimed in any preceding claim, wherein the multiple-region light detector comprises a linear or two dimensional photodiode array.

14. A system as claimed in claim 13, wherein the photodiode array is operable in a first mode in which charges are stored on all photodiodes of the array in response to light input and read out to capture image data, and a second mode in which the signals from selected individual photodiodes or sub-groups of photodiodes are routed, in a sequence, to the processing means.

15. A system as claimed in any preceding claim, further comprising a maximal length sequence generator for generating a modulation signal, and a cross-correlator for obtaining the time delay of a time delayed reflected modulation signal from a comparison of the modulation signal and the time delayed reflected modulation signal.

16. A system as claimed in claim 15, wherein the cross correlator is arranged to carry out the steps of:

determining, at a coarse resolution, the time delay of the modulation signal needed to maximise the correlation between the time delayed modulation signal and the modulation signal,

determining at a finer resolution than the coarse resolution, the correlation between the time delayed modulation signal and modulation signal as a function of the time delay of the time delayed modulation signal with respect to the modulation signal in a time delay range around the determined time delay, and

outputting a measure of distance calculated from the time delay of the modulation signal needed to maximise the correlation between the time delayed modulation signal and the modulation signal.

17. A system as claimed in claim 15 or 16, wherein the cross-correlator comprises:

a coarse cross-correlator for coarsely determining the time delay of the modulation signal needed to maximise the correlation between the time delayed modulation signal and the modulation signal, and

a fine cross-correlator for calculating the correlation between the time delayed modulation signal and the modulation signal as a function of the time delay of the modulation signal with respect to the received signal in a time delay range around the time shift determined by the coarse cross-correlator.

18. A system as claimed in claims 17, wherein the ratio of coarse cross correlator and fine cross-correlator operating frequencies is adjusted to minimise interference between adjacent systems.

19. A system as claimed in claim 17 or 18, wherein the coarse cross correlator is clocked at a first frequency and the fine cross-correlator is clocked at a higher second frequency.

20. A system as claimed in any of claims 15 to 19, wherein the parameters of the maximal length sequence and cross-correlator are adjusted to minimise interference between adjacent systems.