TOF rangefinding with large dynamic range and enhanced background radiation suppression

• US 20070296951A1
• Filed: 08/09/2007
• Published: 12/27/2007
• Est. Priority Date: 07/01/2004
• Status: Active Grant

• Current Assignee: Optrima NV (Sony Group Corp.)
• Original Assignee: Vrije Universiteit Brussel
• Inventors: Kuijk, Maarten, Van Nieuwenhove, Daniel
• Granted Patent: US 7,852,464 B2
• Time in Patent Office: Days
• US Class Current: 356/5.02
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• 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 7/4868 Controlling received signal intensity or exposure of sensor
• CPC Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection

Abstract

A method for measuring time of flight of radiation comprises emitting modulated radiation in response to a first modulation signal, projecting the modulated radiation onto a scene, receiving radiation, the received radiation comprising a first portion being the modulated radiation reflected by the scene and a second portion being background radiation, converting the received radiation into a signal on a conversion node, the signal on the conversion node having a first and a second signal component, the first signal component being indicative of the background radiation and the second signal component being dependent on the reflected modulated radiation, and determining the time of flight of the radiation based on the second signal component. A corresponding device is also provided.

Claims

1. A low-pass filter with an input node and an output node, the filter comprising

a voltage follower connected to the input node, the voltage follower being adapted for providing a controlled voltage drop with respect to an input voltage applied to the input node, and

an output transistor connected between the voltage follower and the output node.

2. A low-pass filter according to claim 1, wherein the voltage follower comprises a series connection of a current source and an input transistor, the input transistor having a gate connected to the input node.

3. A low-pass filter according to claim 2, wherein the −

3 dB frequency of the low-pass filter is tuneable by setting the current of the current source.

4. A low-pass filter according to claim 2, the input transistor having a source, wherein the current source is adapted to deliver a low current so that the voltage over the input transistor between gate and source is below threshold.

5. A low-pass filter according to claim 2, the output transistor having a gate, wherein the input and output transistors are coupled with their gates to each other.

6. A low-pass filter according to claim 2, wherein the input and output transistors are of a same type.

7. A low-pass filter according to claim 6, wherein the input and output transistors are p-type transistors.

8. A low-pass filter according to claim 7, the output transistor having a drain and a source, wherein the source of the output transistor is connected to an output node of the voltage follower, and the drain of the output transistor is connected to the output node of the filter.

9. A low-pass filter according to claim 1, wherein the W/L ratio of the first transistor is adapted to be larger than five.

10. A low-pass filter according to claim 1, furthermore comprising a capacitor connected between the output node and a power supply.

11. A low-pass filter according to claim 10 for use in a 3D camera system capturing incident light, wherein the capacitor is partly transparent for the incident light.

12. A 3D camera system comprising a low-pass filter according to claim 1.