# US 11,445,123 B2 · System and method for PWM control of a video display screen > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,445,123 B2 - Document ID: US11445123B2 - Status: Granted - Kind: B2 - Application number: 17/486,412 - Filed: 2021-09-27 - Published: 2022-03-31 - Granted: 2022-09-13 - Earliest claimed: 2020-09-28 - Assignees: Brompton Technology Ltd. - Applicants: Brompton Technology Ltd. - Inventors: Christopher Deighton - Web page: https://patentgrep.com/patent/US11445123B2 ## CPC - H04N 23/73: by influencing the exposure time - G09G 3/2014: {by modulation of the duration of a single pulse during which the logic level remains constant} - G09G 3/32: semiconductive, e.g. using light-emitting diodes [LED] - G09G 5/10: Intensity circuits - G09G 5/12: Synchronisation between the display unit and other units, e.g. other display units, video-disc players - H04N 23/74: by influencing the scene brightness using illuminating means - G09G 5/006: {Details of the interface to the display terminal (specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04)} - G09G 2320/0247: Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes - G09G 2320/0626: for control of overall brightness - G09G 2320/064: by time modulation of the brightness of the illumination source - G09G 2340/0435: Change or adaptation of the frame rate of the video stream - G09G 2360/145: the light originating from the display screen - H04N 23/745: Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) ## Abstract A PWM control system includes a memory and a processor. The processor obtains camera characteristics relating to a camera that is configured to capture an image displayed by a video display. The camera characteristics include a duration of a period when a shutter of the camera is open. The processor also calculates a PWM timing control for the video display. The PWM timing control specifies a PWM cycle duration that is based on the period when the shutter of the camera is open. The processor further sends a signal to the video display. The signal includes the PWM timing control and is configured to cause the video display to control a brightness of the video display according to the PWM timing control during the period when the shutter of the camera is open. ## Claims ### Claim 1 A pulse width modulation (PWM) control system comprising: a memory configured to store instructions; and a processor coupled to the memory and configured to execute instructions stored in the memory to: obtain camera characteristics relating to a camera that is configured to capture an image displayed by a video display, the camera characteristics comprising a duration of a period when a shutter of the camera is open; calculate a PWM timing control for the video display, the PWM timing control specifying a PWM cycle duration based on the period when the shutter of the camera is open; and send a signal to the video display, the signal including the PWM timing control and configured to cause the video display to control a brightness of the video display according to the PWM timing control during the period when the shutter of the camera is open. ### Claim 2 (depends on 1) The PWM control system of claim 1, wherein the PWM timing control is a first PWM timing control and the PWM cycle duration is a first PWM cycle duration, the processor is configured to execute the instructions stored in the memory to calculate a second PWM timing control specifying a second PWM cycle duration based on the period when the shutter of the camera is closed, and the signal further includes the second PWM timing control and is further configured to cause the video display to control the brightness of the video display according to the second PWM timing control during the period when the shutter of the camera is closed. ### Claim 3 (depends on 1) The PWM control system of claim 1, wherein the signal includes an indication of a time of initiation of the PWM cycle. ### Claim 4 (depends on 1) The PWM control system of claim 1, wherein the PWM cycle duration specified by the PWM timing control is less than the duration of the period when the shutter of the camera is open. ### Claim 5 (depends on 1) The PWM control system of claim 1, wherein the signal further includes a PWM adjustment. ### Claim 6 (depends on 5) The PWM control system of claim 5, wherein the PWM adjustment is configured to cause the video display to lengthen or shorten the PWM cycle duration by one of adjusting a PWM clock rate, adjusting a PWM bit depth, extending or shortening one or more periods where the video display is off in the PWM cycle, and truncating the PWM cycle before it has completed. ### Claim 7 (depends on 1) The PWM control system of claim 1, wherein the PWM timing control is a first PWM timing control, the PWM cycle duration is a first PWM cycle duration, the signal is a first signal, the period when the shutter of the camera is open is a first period, and the processor is configured to execute the instructions stored in the memory to: calculate a second PWM timing control for the video display, the second PWM timing control specifying a second PWM cycle duration, where an average value of the first PWM cycle duration and the second PWM cycle duration more closely matches the duration of the first period when the shutter of the camera is open than does the first PWM cycle duration; and send a second signal to the video display, the second signal including the second PWM timing control and configured to cause the video display to control the brightness of the video display according to the second PWM timing control during a second period when the shutter of the camera is open. ### Claim 8 (depends on 1) The PWM control system of claim 1, wherein the camera characteristics further comprise a camera shutter type, and the processor is configured to execute the instructions stored in the memory to calculate the PWM timing control further based on the camera shutter type. ### Claim 9 (depends on 1) The PWM control system of claim 1, wherein the processor is configured to execute the instructions stored in the memory to send to a user of the PWM control system a PWM matching signal configured to indicate how closely the PWM cycle duration matches the period when the shutter of the camera is open. ### Claim 10 (depends on 1) The PWM control system of claim 1, wherein the camera characteristics is a first camera characteristics relating to a first camera, comprising a first duration of a first period when the shutter of the first camera is open, and the processor is configured to execute the instructions stored in the memory to: obtain a second camera characteristics relating to a second camera configured to capture the image displayed by the video display, the second camera characteristics comprising a second duration of a second period when a shutter of the second camera is open; and calculate the PWM timing control based on both the first camera characteristics and the second camera characteristics. ### Claim 11 A method of controlling pulse width modulation (PWM) in a video display, the method comprising: obtaining, by a control system, camera characteristics relating to a camera that is configured to capture an image displayed by the video display, the camera characteristics comprising a duration of a period when a shutter of the camera is open; calculating, by the control system, a PWM timing control for the video display, the PWM timing control specifying a PWM cycle duration based on the period when the shutter of the camera is open; and sending, by the control system, a signal to the video display, the signal configured to cause the video display to control a brightness of the video display according to the PWM timing control during the period when the shutter of the camera is open. ### Claim 12 (depends on 11) The method of claim 11, wherein the PWM timing control is a first PWM timing control and the PWM cycle duration is a first PWM cycle duration, the method further comprising: calculating by the control system a second PWM timing control specifying a second PWM cycle duration based on the period when the shutter of the camera is closed, wherein the signal further includes the second PWM timing control and is further configured to cause the video display to control the brightness of the video display according to the second PWM timing control during the period when the shutter of the camera is closed. ### Claim 13 (depends on 11) The method of claim 11, wherein the signal includes an indication of a time of initiation of the PWM cycle. ### Claim 14 (depends on 11) The method of claim 11, wherein the PWM cycle duration specified by the PWM timing control is less than the duration of the period when the shutter of the camera is open. ### Claim 15 (depends on 11) The method of claim 11, wherein the signal further includes a PWM adjustment. ### Claim 16 (depends on 15) The method of claim 15, wherein the PWM adjustment is configured to cause the video display to lengthen or shorten the PWM cycle duration by one of adjusting a PWM clock rate, adjusting a PWM bit depth, extending or shortening one or more periods where the video display is off in the PWM cycle, and truncating the PWM cycle before it has completed. ### Claim 17 (depends on 11) The method of claim 11, wherein the PWM timing control is a first PWM timing control, the PWM cycle duration is a first PWM cycle duration, the signal is a first signal, the period when the shutter of the camera is open is a first period, the method further comprising: calculating by the control system a second PWM timing control for the video display, the second PWM timing control specifying a second PWM cycle duration, where an average value of the first PWM cycle duration and the second PWM cycle duration more closely matches the duration of the first period when the shutter of the camera is open than does the first PWM cycle duration; and sending by the control system a second signal to the video display, the second signal including the second PWM timing control and configured to cause the video display to control the brightness of the video display according to the second PWM timing control during a second period when the shutter of the camera is open. ### Claim 18 (depends on 11) The method of claim 11, wherein the camera characteristics further comprise a camera shutter type, the method further comprising calculating the PWM timing control further based on the camera shutter type. ### Claim 19 (depends on 11) The method of claim 11, the method further comprising sending by the control system to a user of the control system a PWM matching signal configured to indicate how closely the PWM cycle duration matches the period when the shutter of the camera is open. ### Claim 20 (depends on 11) The method of claim 11, wherein the camera characteristics is a first camera characteristics relating to a first camera, comprising a first duration of a first period when the shutter of the first camera is open, the method further comprising: obtaining by the control system a second camera characteristics relating to a second camera configured to capture the image displayed by the video display, the second camera characteristics comprising a second duration of a second period when a shutter of the second camera is open; and calculating by the control system the PWM timing control based on both the first camera characteristics and the second camera characteristics.