Time-of-flight based distance measuring method and distance measuring system

Abstract

A time-of-flight based distance measuring method and system are provided. The distance measuring method includes: sending a pulse from a transmitter side intermittently, the pulse being reflected by a target object, a reflected signal being reflected from the target object accordingly; utilizing a receiver side to perform a signal sampling operation multiple times according to a sampling period for a predetermined period of time and accordingly generate a sampling result of the reflected signal, the predetermined period of time being longer than or equal to two times a pulse period of the pulse; detecting time of flight of the pulse traveling from the transmitter side to the receiver side according to the sampling results and measuring distance between the target object and a reference position according to the time of flight. The distance measuring method achieves low power consumption, measures the distance rapidly and maintains good measurement quality.

What is claimed is: 
     
         1 . A time-of-flight based distance measuring method, comprising:
 sending a pulse from a transmitter side intermittently, wherein the pulse is reflected by a target object, and a reflected signal is reflected from the target object accordingly;   utilizing a receiver side to perform a signal sampling operation multiple times according to a sampling period for a predetermined period of time, and accordingly generate a sampling result of the reflected signal, wherein the predetermined period of time is longer than or equal to two times a pulse period of the pulse;   detecting time of flight of the pulse traveling from the transmitter side to the receiver side according to the sampling result; and   measuring a distance between the target object and a reference position according to the time of flight.   
     
     
         2 . The distance measuring method of  claim 1 , wherein the step of utilizing the receiver side to perform the signal sampling operation multiple times according to the sampling period for the predetermined period of time comprises:
 before arrival of the reflected signal at the receiver side, starting performing the signal sampling operation according to the sampling period.   
     
     
         3 . The distance measuring method of  claim 1 , wherein the step of the step of utilizing the receiver side to perform the signal sampling operation multiple times according to the sampling period for the predetermined period of time comprises:
 after a period of time has elapsed since sending the pulse from the transmitter side, starting performing the signal sampling operation according to the sampling period, wherein the period of time is shorter than or equal to half the pulse period.   
     
     
         4 . The distance measuring method of  claim 1 , wherein a time difference between a time when the transmitter side starts sending the pulse and a time when the receiver side starts performing the signal sampling operation is shorter than the pulse period. 
     
     
         5 . The distance measuring method of  claim 1 , wherein the step of utilizing the receiver side to perform the signal sampling operation multiple times according to the sampling period for the predetermined period of time comprises:
 while the transmitter is starting sending the pulse, utilizing the receiver side to start performing the signal sampling operation according to the sampling period.   
     
     
         6 . The distance measuring method of  claim 1 , wherein the step of utilizing the receiver side to perform the signal sampling operation multiple times according to the sampling period for the predetermined period of time comprises:
 while the pulse sent from the transmitter is falling, utilizing the receiver side to start performing the signal sampling operation according to the sampling period.   
     
     
         7 . The distance measuring method of  claim 1 , wherein the predetermined period of time comprises a first sampling interval and a second sampling interval, and each of a duration of the first sampling interval and a duration of the second sampling interval is equal to the pulse period; the step of utilizing the receiver side to perform the signal sampling operation multiple times according to the sampling period for the predetermined period of time and accordingly generate the sampling result of the reflected signal comprises:
 sensing the reflected signal to generate a response signal;   during each of the first sampling interval and the second sampling interval, generating a first pixel output by selectively utilizing a first transmission path to receive the response signal according to a first control signal, and generating a second pixel output by selectively utilizing a second transmission path to receive the response signal according to a second control signal, wherein the second control signal and the first control signal have different phases, and at least one of the first transmission path and the second transmission path is utilized to receive the response signal; and   sampling the first pixel output and the second pixel output each time the sampling period has elapsed, and accordingly generating the sampling result according to the first pixel output and the second pixel output.   
     
     
         8 . The distance measuring method of  claim 7 , wherein the step of generating the first pixel output comprises:
 when the response signal is received through the first transmission path, sampling the response signal to generate the first pixel output; and   the step of generating the second pixel output comprises:   when the response signal is received through the second transmission path, sampling the response signal to generate the second pixel output.   
     
     
         9 . The distance measuring method of  claim 8 , wherein the step of generating the first pixel output further comprises:
 when the first transmission path is not utilized for receiving the response signal, generating a first reference signal serving as the first pixel output;   the step of generating the second pixel output further comprises:   when the second transmission path is not utilized for receiving the response signal, generating a second reference signal serving as the second pixel output; and   the step of generating the sampling result according to the first pixel output and the second pixel output comprises:   each time the first pixel output and the second pixel output are sampled, generating the sampling result by subtracting one of the first pixel output and the second pixel output from the other of the first pixel output and the second pixel output.   
     
     
         10 . The distance measuring method of  claim 7 , wherein the first control signal and the second control signal have a phase difference of 180 degrees. 
     
     
         11 . The distance measuring method of  claim 7 , wherein a waveform of the first control signal occurring during the first sampling interval is identical to a waveform of the first control signal occurring during the second sampling interval, and a waveform of the second control signal occurring during the first sampling interval is identical to a waveform of the second control signal occurring during the second sampling interval 
     
     
         12 . The distance measuring method of  claim 1 , wherein the sampling period is equal to a quarter of the pulse period. 
     
     
         13 . A time-of-flight based distance measuring system, comprising:
 a pulse generator unit;   a control circuit, coupled to the pulse generator unit, the control circuit being configured to control the pulse generator unit to send a pulse intermittently, wherein the pulse is reflected by a target object and a reflected signal is reflected from the target object accordingly;   a time-of-flight sensor, controlled by the control circuit, the time-of-flight sensor being configured to perform a signal sampling operation multiple times according to a sampling period for a predetermined period of time, and accordingly generate a sampling result of the reflected signal, wherein the predetermined period of time is longer than or equal to two times a pulse period of the pulse; the time-of-flight sensor is further configured to detect time of flight of the pulse traveling from the pulse generator unit to the time-of-flight sensor according to the sampling result, and measure a distance between the target object and the distance measuring system according to the time of flight.   
     
     
         14 . The distance measuring system of  claim 13 , wherein before arrival of the reflected signal at the time-of-flight sensor, the control circuit is configured to control the time-of-flight sensor to start performing the signal sampling operation according to the sampling period. 
     
     
         15 . The distance measuring system of  claim 13 , wherein after a period of time has elapsed since the pulse generator unit sent the pulse, the control circuit is configured to control the time-of-flight sensor to start performing the signal sampling operation according to the sampling period; the period of time is shorter than or equal to half the pulse period. 
     
     
         16 . The distance measuring system of  claim 13 , wherein a time difference between a time when the pulse generator unit starts sending the pulse and a time when the time-of-flight sensor starts performing the signal sampling operation is shorter than the pulse period. 
     
     
         17 . The distance measuring system of  claim 13 , wherein the control circuit is configured to, while the pulse generator unit is starting sending the pulse, control the time-of-flight sensor to start performing the signal sampling operation according to the sampling period. 
     
     
         18 . The distance measuring system of  claim 13 , wherein the control circuit is configured to, while the pulse is falling, control the time-of-flight sensor to start performing the signal sampling operation according to the sampling period. 
     
     
         19 . The distance measuring system of  claim 18 , wherein the time-of-flight sensor comprises:
 a pixel array, comprising a plurality of pixels, wherein each of the pixels comprises:
 a sensor, configured to sense the reflected signal to generate a response signal; 
 a first readout circuit configured to, during each sampling interval of the first sampling interval and the second sampling interval included in the predetermined period of time, selectively transmit the response signal according to a first control signal generated from the control circuit and accordingly generate a first pixel output, wherein a duration of the sampling interval is equal to the pulse period; and 
 a second readout circuit configured to, during the sampling interval, selectively transmit the response signal according to a second control signal generated from the control circuit and accordingly generate a second pixel output, wherein the second control signal and the first control signal have different phases, and at least one of the first readout circuit and the second readout circuit is utilized to transmit the response signal during the sampling interval; and 
   a processing circuit, coupled to the pixel array and the control circuit, the processing circuit being configured to refer to a sample control signal generated from the control circuit to sample the first pixel output and the second pixel output each time the sampling period has elapsed, and accordingly generate the sampling result according to the first pixel output and the second pixel.   
     
     
         20 . The distance measuring system of  claim 19 , wherein when the first readout circuit is utilized to transmit the response signal during the sampling interval, the first readout circuit is configured to sample the response signal to generate the first pixel output; when the second readout circuit is utilized to transmit the response signal during the sampling interval, the second readout circuit is configured to sample the response signal to generate the second pixel output.