# US 2021/0333404 A1 · Imaging system with time-of-flight sensing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0333404 A1 - Document ID: US20210333404A1 - Status: Published application - Kind: A1 - Application number: 17/134,726 - Filed: 2020-12-28 - Published: 2021-10-28 - Earliest claimed: 2020-04-27 - Assignees: Semiconductor Components Industries, LLC - Applicants: Semiconductor Components Industries, LLC - Inventors: Erez TADMOR - Web page: https://patentgrep.com/patent/US20210333404A1 ## CPC - G01S 17/894: Three-dimensional [3D] imaging with simultaneous measurement of time-of-flight at a two-dimensional [2D] array of receiver pixels, e.g. time-of-flight cameras or flash lidar - G01S 7/484: Transmitters - G01S 7/4863: Detector arrays, e.g. charge-transfer gates - G01S 7/4865: Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487) - H04N 23/73: by influencing the exposure time - H04N 25/77: Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract A time-of-flight (TOF) sensing system may include an illumination module and a sensor module. The illumination module may emit light having a reduced illumination duty cycle such as a high peak power and low width illumination pulse. The emitted light may reflect off of one or more objects as reflected light. The sensor module may include pixels operable based on a sensor modulation signal to generated image charge portions in response to the reflected light. The sensor modulation signal may be selectively suppressed after a period of time corresponding to a distance of interest. Processing circuitry in the TOF sensing system may obtain TOF information based on a phase difference between the emitted light and the image charge portions determined by cross-correlation data. By using the illumination pulse and the selective sensor modulation suppression, TOF sensing may exhibit reduced aliasing issues and improved ambient light rejection. ## Claims ### Claim 1 A time-of-flight sensing system comprising: an illumination source configured to emit a light pulse for a time-of-flight sensing operation; pixels configured to receive reflected light resulting from the emitted light pulse and to generate charge in response to the received light during the time-of-flight sensing operation; driver circuitry configured to control the pixels based on a sensor modulation signal having a modulation frequency during the time-of-flight sensing operation; and processing circuitry configured to generate cross-correlation data based on the generated charge to identify time-of-flight information. ### Claim 2 (depends on 1) The time-of-flight sensing system defined in claim 1, wherein each of the pixels includes a photosensitive element coupled to first and second charge storage region via first and second transistors, respectively. ### Claim 3 (depends on 2) The time-of-flight sensing system defined in claim 2, wherein the driver circuitry provides first and second corresponding control signals to the first and second transistors for at least a given pixel based on the sensor modulation signal. ### Claim 4 (depends on 3) The time-of-flight sensing system defined in claim 3, wherein the first and second transistors for the given pixel are alternatively activated by the first and second corresponding control signals to store the generated charge in first and second portions at the first and second charge storage regions, respectively, during the time-of-flight sensing operation. ### Claim 5 (depends on 4) The time-of-flight sensing system defined in claim 4, wherein the first and second transistors for the given pixel are coupled to a floating diffusion region and pixel readout circuitry, and wherein the given pixel is configured to perform separate readout operations for each of the first and second portions of the generated charge. ### Claim 6 (depends on 1) The time-of-flight sensing system defined in claim 1, wherein the illumination source is configured to emit additional light pulses, and the light pulse and the additional pulses occur at a frequency less than the modulation frequency. ### Claim 7 (depends on 6) The time-of-flight sensing system defined in claim 6, wherein the light pulse and the additional light pulses for an illumination signal having a duty cycle of less than 20 percent. ### Claim 8 (depends on 6) The time-of-flight sensing system defined in claim 6, wherein each of the additional light pulses is associated with a corresponding additional time-of-flight sensing operation. ### Claim 9 (depends on 1) The time-of-flight sensing system defined in claim 1, wherein the sensor modulation signal is used to control the pixels during a first time period in the time-of-flight operation and pixel modulation is suppressed during a second time period in the time-of-flight sensing operation. ### Claim 10 (depends on 9) The time-of-flight sensing system defined in claim 9, wherein the pixels are modulated to store different portions of the generated charge at corresponding charge storage regions in each pixel during the first time period, and wherein pixel modulation is suppressed by stopping an integration of additional charge at the corresponding charge storage regions in each pixel during the second time period. ### Claim 11 (depends on 9) The time-of-flight sensing system defined in claim 9, wherein the first time period is associated with distances within a target distance of interest, and the second time period is associated with distances outside of the target distance of interest. ### Claim 12 A method for indirect time-of-flight sensing operations comprising: emitting a light signal exhibiting light pulses at a pulse frequency; receiving a reflected light signal resulting from the emitted light signal at sensor module; performing sensor modulation for the sensor module using a modulation frequency to generate sensor data based on the reflected light signal, wherein the pulse frequency is less than the modulation frequency; and determining time-of-flight information based on cross-correlation data obtained from the sensor data. ### Claim 13 (depends on 12) The method defined in claim 12, wherein performing the sensor modulation comprises, for each active pixel in the sensor module, storing different portions of charge at corresponding charge storage regions in each active pixel and separately reading out each of the different portions of charge from each active pixel. ### Claim 14 (depends on 13) The method defined in claim 13 further comprising: after performing the sensor modulation for a time period associated with a distance of interest, stopping the sensor modulation. ### Claim 15 (depends on 14) The method defined in claim 14, wherein stopping the sensor modulation comprises, for each active pixel in the sensor module, stopping the integration of additional charge at the corresponding charge regions in each active pixel. ### Claim 16 (depends on 12) The method defined in claim 12, wherein each light pulse in the light signal is associated with a corresponding time-of-flight sensing operation based on which corresponding time-of-flight information is determined. ### Claim 17 (depends on 12) The method defined in claim 12, wherein the light signal has a duty cycle of less than 20 percent. ### Claim 18 An indirect time-of-flight sensor comprising: an illumination module configured to emit a light signal having one illumination pulse for each time-of-flight sensing operation; and a sensor module configured to receive a reflected light signal based on a reflected version of the emitted light signal, to perform signal modulation based on a modulation frequency to generate charge in response to the received light signal for a given time-of-flight sensing operation, and to suppress sensor modulation for the given time-of flight sensing operation based on a distance of interest within which time-of-flight information is determined. ### Claim 19 (depends on 18) The indirect time-of-flight sensor defined in claim 18, wherein the light signal has a pulse frequency that is less than the modulation frequency. ### Claim 20 (depends on 18) The indirect time-of-flight sensor defined in claim 18, wherein the sensor module is configured to perform ambient light rejection and aliasing rejection when suppressing the sensor modulation.