Integrated motion vision sensor

• US 6,253,161 B1
• Filed: 07/09/1998
• Issued: 06/26/2001
• Est. Priority Date: 07/10/1997
• Status: Expired due to Fees

• Current Assignee: Universite Laval
• Original Assignee: Universite Laval
• Inventors: Arias-Estrada, Miguel
• Primary Examiner(s): SHAH, KAMINI S
• Application Number:
  US09/112,101
• Time in Patent Office: 1,083 Days
• Field of Search: 348/158, 348/165, 348/144, 358/213.24, 702/150, 702/151, 702/152, 702/153, 382/209, 707/100
• US Class Current: 702/150
• CPC Class Codes: G01S 11/12 using electromagnetic waves other than radio waves
• CPC Class Codes: H04N 25/47 Image sensors with pixel address output; Event-driven image sensors; Selection of pixels to be read out based on image data
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: H04N 3/155 Control of the image-sensor operation, e.g. image processing within the image-sensor

Abstract

A custom CMOS imager with integrated motion computation is described. The architecture is centered around a compact mixed-mode pixel with digital asynchronous self-signaling capabilities. An address-event communication channel with an external time-stamp protocol is used to compute image features velocities. The motion sensor could be used in applications such as self-guided vehicles, mobile robotics and smart surveillance systems.

Claims

1. An system for detecting and determining the direction of motion of an object, an image of which appears as an image formed by an array of pixels, said system comprising:

a motion sensor with self-signaling pixels for signaling detection of motion and transmitting information regarding that motion;

a digital module which receives the information regarding the detected motion, which module stores said information and after a fixed measurement time period computes velocity vectors from said information received from a set of at least two pixels and then transmits said velocity vectors to a host computer for further use; and

wherein said motion sensor and digital module combination allows for real time continuous operation of the system.

2. The system of claim 1 wherein the motion sensor has an array with a plurality of self-signaling pixels.

3. The system of claim 2 wherein the set of pixels comprises four pixels so that the digital module can compute a bidimensional velocity vector.

4. The system of claim 3 wherein a plurality of velocity vectors are sent as a vector map to the host computer.

5. The system of claim 1 wherein the motion sensor further comprises at least one arbiter for request sequentiation of signals from the pixels to avoid collisions during multiple motion based signalization by said pixels.

6. The system of claim 1 wherein the fixed measurement time period can be changed to allow for a range of resolution of velocity computation.

7. The system of claim 1 wherein the pixel circuitry is designed for slow adaptation to gradual changes in illumination and to quick response to sharp changes in illumination so that the pixels detect moving edges.

8. A method for detecting motion of an object and determining the direction and speed of that motion, said method comprising the steps of:

sensing motion with a plurality of self-signaling pixels, which pixels make up an array of a motion sensor;

signaling by each of the pixels as they detect motion that they have detected motion;

sequencing for attention during a time measurement period information being provided by each of the pixels which are sensing motion;

time stamping the information received from each of the pixels;

saving the information from each pixel which has been time stamped to a specific memory address;

retrieving from memory at the end of each time measurement period the information from each pixel which has been time stamped during that measurement period;

computing velocity vectors from the time stamped information;

creating with the computed velocity vectors a velocity vector map; and

using the velocity vector map to determine direction of motion and speed of an object.

9. The method of claim 8 wherein the step of computing the velocity vector further comprises the steps of:

reading from specific memory addresses time stamped information of four adjacent pixels;

computing a direction of a velocity vector with the time stamped information from the four pixels;

computing a speed of the velocity vector with the time stamped information from the four pixels; and

saving the velocity vector to a velocity vector map.

10. A self-signaling pixel for use in a motion sensing array for detecting motion comprising:

a photoreceptor for detecting motion;

analog conditioning circuitry to convert a photoreceptor signal from an analog to a digital signal;

a digital memory cell to store signals generated by the photoreceptor; and

wherein the pixel is operatively connected to the motion sensing array such that when the photodetector detects motion the photodetector generates an analog signal with information concerning the motion, which signal is in turn converted to a digital signal which is saved to the memory cell which cell retains the information until a signal sent by the pixel to the motion sensing array is acknowledged whereupon the information in the cell is transferred from the memory cell to the sensing array for further processing and the memory cell is reset to receive and save the next signal generated by the photodetector.