Method and arrangement for measuring the distance to an object

• US 20070182949A1
• Filed: 12/20/2006
• Published: 08/09/2007
• Est. Priority Date: 12/21/2005
• Status: Active Grant

• Current Assignee: Ecole polytechnique fãdãrale de lausanne epfl (Schweizerische Eidgenossenschaft)
• Original Assignee: Ecole polytechnique fãdãrale de lausanne epfl (Schweizerische Eidgenossenschaft)
• Inventors: Niclass, Cristiano
• Granted Patent: US 8,355,117 B2
• Time in Patent Office: Days
• US Class Current: 356/3
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• 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 7/491 Details of non-pulse systems
• CPC Class Codes: G01S 7/493 Extracting wanted echo signals

Abstract

Arrangement (10) for measuring the distance to an object, comprising: a photonic source for illuminating said object using a continuous modulated photonic wave, a solid-state image sensor, comprising an array of avalanche photodiodes and a plurality of circuits for processing signals output by said avalanche photodiodes to yield data depending on the photonic wave reflected by said object onto said photodiodes. The circuit may comprise a multiplexer at the pixel level arranged so as to accumulate the signal output by the avalanche photodiode during different sub-periods in different storage devices.

Claims

1. An arrangement (10) for measuring the distance to an object, comprising:

a photonic source for illuminating said object using a continuous modulated photonic wave,

a solid-state image sensor, comprising an array with WXH avalanche photodiodes with W≧

1 and H≧

1 and a circuit for processing signals output by said avalanche photodiodes to yield data depending on the photonic wave reflected by said object onto said photodiodes.

2. The arrangement of claim 1, said sensor comprising one said circuit for each avalanche photodiode.

3. The arrangement of claim 1, said sensor comprising at least one said circuit for processing signals output by a plurality of avalanche photodiodes.

4. The arrangement of claim 1, wherein said photonic wave is periodically modulated,

and wherein said circuit yields data proportional to the phase and/or amplitude of said reflected photonic wave.

5. The arrangement of claim 1, wherein said solid-state image sensor is fabricated on a monolithic integrated CMOS circuit chip, and wherein said avalanche photodiodes are reverse biased above their breakdown voltage, thus operating in Geiger mode.

6. The arrangement of claim 1, wherein each said circuit comprises at least one multiplexer, one or more storage devices, and a readout circuit,

wherein each independent multiplexer output is connected to an independent storage device,

wherein at least one selection input of said multiplexer is periodically modulated so as to accumulate into said storage devices the signal output by at least one connected avalanche photodiode during a given period of time defined as the integration time.

7. The arrangement of claim 6, wherein each storage device comprises at least one counter,

and wherein each counter is connected to readout circuit allowing the contents of each counter to be read simultaneously and/or consecutively synchronously to an global clock signal or asynchronously via a read request signal.

8. The arrangement of claim 7, wherein the content of said counter is read and reset many times during each integration time so that the capacity of said counter can be reduced.

9. The arrangement of claim 7, wherein the output of said avalanche photodiode circuit and/or the outputs of said multiplexer are held to an inactive state as soon as the full capacity of one of said counters is reached, using an overflow signal provided by each counter.

10. The arrangement of claim 7, wherein said multiplexer holds its state when the avalanche photodiode circuit output is active so that only the counter connected to the multiplexer output that was selected during the photo detection is incremented on the leading edge of said digital pulse.

11. The arrangement of claim 10, wherein each periodically modulated selection input of said multiplexer is connected through a digital latch, the clock signal of said latch is synchronized with the digital signal of the avalanche photodiode circuit so that when the digital pulse is at its active level, the latch is blocked and so is each multiplexer selection input.

12. The arrangement of claim 1, said solid-state image sensor comprising an array of pixels, each pixel comprising:

(a) one of said avalanche photodiodes;

(b) one multiplexer with one common input, one selection input, and at least two outputs;

(c) at least two digital counters with an overflow output signal; and

(d) a readout circuit that allows the contents of said at least two counters to be read and reset.

13. The arrangement of claim 1, said solid-state image sensor comprising an array of pixels and means for combining the signals of two or more avalanche photodiodes within a pixel to increase the sensitivity of the pixel to the photonic wave.

14. The arrangement of claim 13, wherein each pixel comprises a plurality of avalanche photodiode and a plurality of storage devices, different avalanche photodiodes and/or different storage devices of one pixel being periodically activated and deactivated at different instants of one cycle of said photonic wave.

15. The arrangement of claim 14, wherein each pixel comprises:

(a) two avalanche photodiodes;

(b) two digital counters; and

(c) one readout circuit,

wherein each counter is connected to one avalanche photodiode,

wherein said avalanche photodiode outputs and/or digital counters inputs are periodically activated and deactivated in synchronization with said photonic wave via a logic gate,

wherein when one counter is activated, the other counter is deactivated.

16. The arrangement of claim 1, comprising a plurality of integrated focusing elements for focusing light into the light sensitive part of each photodiode.

17. The arrangement of claim 1, comprising a plurality of colour filters with different colours to generate colour intensity images.

18. The arrangement of claim 1, comprising a circuit for compensating the effects of timing and/or amplitude shifts or timing jitter depending on the signal output by at least one reference photodiode.

19. The arrangement of claim 1, comprising a circuit for changing the modulation frequency used for modulating said photonic wave.

20. A method for measuring the distance to an object, comprising the steps of:

illuminating said object with a continuous modulated photonic wave,

determining said distance from signals delivered at the outputs of avalanche photodiodes arranged in an array on a solid-state sensor.

21. The method of claim 20, wherein said photonic wave is periodically modulated,

and wherein said distance is determined from the phase and/or amplitude of the photonic wave reflected onto said photodiode.

22. The method of claim 20, comprising a step of operating a plurality of avalanche photodiodes in Geiger mode on a monolithic integrated CMOS solid-state sensor.

23. The method of claim 20, comprising the steps of:

illuminating said object with a periodic photonic wave having a period (P);

counting pulses generated by said avalanche photodiodes during each of a plurality of fractions of said period (P),

determining said distance from the amounts of counted pulses during each of said fractions of said period.

24. The method of claim 23, comprising a step of multiplexing the output of said avalanche photodiode so as to connect the output of said avalanche photodiode with different storage devices during said different fractions of said period.

25. The method of claim 24, comprising the steps of:

(a) choosing a total integration time longer than said period,

(b) dividing said total integration time into a plurality of fractions of the integration time;

(c) commanding a selection input of a multiplexer with selection signals having different phases during said fractions of the integration time,

(d) during each fraction of the integration time, separately accumulating the number of pulses generated over a plurality of periods by said avalanche photodiodes during each fraction of period.

26. The method of claim 25, wherein said integration time is divided into an even number of intervals of the integration time larger than two, the method consisting of using all the odd intervals of the integration time to form a first fraction of the integration time and all the even intervals to form a second fraction of the integration time.

27. The method of claim 20, comprising a step of determining the lifespan of a fluorophore attached to a given molecule under investigation from the phase of a photonic wave received by said avalanche photodiode.

28. A circuit comprising:

an integrated array of WXH avalanche photodiodes with W≧

1 and H≧

1.

a circuit connected to said array for generating signals depending on the phase and/or amplitude of a continuous photonic wave received by each photodiodes.

29. A solid-state image sensor comprising:

an array of avalanche photodiodes;

a plurality of counters connected to the output of said photodiodes for accumulating the photocharges received during a plurality of successive sampling intervals.