GB2507416A - LED display luminance control - Google Patents

LED display luminance control Download PDF

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Publication number
GB2507416A
GB2507416A GB201317971A GB201317971A GB2507416A GB 2507416 A GB2507416 A GB 2507416A GB 201317971 A GB201317971 A GB 201317971A GB 201317971 A GB201317971 A GB 201317971A GB 2507416 A GB2507416 A GB 2507416A
Authority
GB
United Kingdom
Prior art keywords
luminance
pixels
illuminated
pixel
control system
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB201317971A
Other versions
GB201317971D0 (en
GB2507416B (en
Inventor
Jon Robert Wood
Paul Frederick Hackney
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hanover Displays Ltd
Original Assignee
Hanover Displays Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hanover Displays Ltd filed Critical Hanover Displays Ltd
Priority to GB201317971A priority Critical patent/GB2507416B/en
Publication of GB201317971D0 publication Critical patent/GB201317971D0/en
Publication of GB2507416A publication Critical patent/GB2507416A/en
Application granted granted Critical
Publication of GB2507416B publication Critical patent/GB2507416B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/0646—Modulation of illumination source brightness and image signal correlated to each other
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2360/00—Aspects of the architecture of display systems
    • G09G2360/14—Detecting light within display terminals, e.g. using a single or a plurality of photosensors
    • G09G2360/144—Detecting light within display terminals, e.g. using a single or a plurality of photosensors the light being ambient light

Abstract

A dot matrix LED display has an array of LED pixels and a control system configured to set the luminance of each pixel that is illuminated at a first luminance, L, if the percentage x of illuminated pixels is less than or equal to a threshold percentage n. L is set inversely with an ambient light level. The control system is configured to illuminate each pixel at a reduced luminance L, where L = (n/x)L, if n > x. A software low-pass filter is used to smooth the value of L.

Description

I
LED DISPLAYS
Background to the Invention
[0001] This invention relates to a dot matrix LED display.
[0002] The display could, for example, be used on the exterior of interior of a vehicle such as a bus, for displaying variable information such as destination information. Other uses include video walls, light curtains, static displays, for example in shop windows, and vehicle dashboard displays.
[0003] Known displays include brightness controls. Thus under bright sunlight conditions the luminance of the dispTay can be set to a maximum and, at night, with no external lighting, the luminance can be set to a minimum. However, when a high proportion of the pixels are illuminated, power consumption is correspondingly high. Also, the display can be dazzling for viewers.
Summary of the Invention
[0004] The present invention provides a dot matrix LED display having an array of LED pixeTs and a controT system configured to set the luminance of each pixel that is illuminated at a first luminance, L, if the percentage x of ilTuminated pixels is less than or equaT to a threshold percentage n, L being set inversely with an ambient light level, and the control system being configured to illuminate each pixel at a reduced luminance U, where L' = (n/x)L, if 11 > x, a software low-pass filter being used to smooth the value of U. [0005] The control system can control the luminance by pulse width modulation and/or current register adjustment.
Detailed Description of Particular Embodiments
[0006] A particular embodiment of the invention wiTl now be described by way of
example only.
[0007] The LED dispTay of the invention comprises a microcontrolTer having a soTid state memoly that stores the current state of the pixels of the display. At regular time intervals, the microcontroller calculates the percentage, x, of pixels that are on. Thus if all pixels are illuminated, x = 100.
[0008] Without using the present invention, the level of Tuminarice is set by the light falling on an ambient light sensor. For example, under bright sunlight conditions the luminance would be set to the maximum and in the night with rio external lighting present, the luminance would be set to minimum. Call the value set by the sensor L. Then we denote U for the value of brightness with the invention applied. The percentage of illuminated pixels at which we want to begin normalisation is denoted n. In a particular example n is 50%. Most text messages only use between 30%-40% of pixels at maximum. If 50% or more pixels are lit, it is usually a graphic image or a reverse video' effect text where the wording is shown by the pixels that are off, not the ones that are on.
[0009] For conditions where: x <= ii, the luminance will remain set at 1.
[0010] For conditions where: x> n, the luminance will be set to U, where U = (n/x) L OO11J A software low pass filter wiTi be applied to the output to avoid U being overly affected by transient changes in x.
[0012] Actual luminance adjustment is made using one or both of the existing techniques of PWM (pulse width modulation) and current register adjustment.
The relationship between the luminance and the current adjustment made to the LEDs via one of both of these exishng techniques is approximately Tinear and can be assumed to be linear for the purposes of this invention.
[0013] The invention thus provides a more easily readable display at high illuminated pixel percentages, whilst saving power.

Claims (3)

  1. CLAIMS1. A dot matrix LED display having an array of LED pixels and a control system configured to set the Turninance of each pixel that is illuminated at a first luminance, L, if the percentage x of illuminated pixels is less than or equal to a threshold percentage n, L being set inversely with an ambient light level, and the control system being configured to illuminate each pixel at a reduced luminance U, where It' = (n/x)L, if n > x, a software low-pass filter being used to smooth the value of It'.
  2. 2. A display according to claim 1, wherein luminance is controlled by pulse width modulation.
  3. 3. A display according to claim 1 or 2, wherein luminance is controlled by current register adjustment.
GB201317971A 2013-10-10 2013-10-10 LED displays Active GB2507416B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB201317971A GB2507416B (en) 2013-10-10 2013-10-10 LED displays

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB201317971A GB2507416B (en) 2013-10-10 2013-10-10 LED displays

Publications (3)

Publication Number Publication Date
GB201317971D0 GB201317971D0 (en) 2013-11-27
GB2507416A true GB2507416A (en) 2014-04-30
GB2507416B GB2507416B (en) 2015-02-25

Family

ID=49679884

Family Applications (1)

Application Number Title Priority Date Filing Date
GB201317971A Active GB2507416B (en) 2013-10-10 2013-10-10 LED displays

Country Status (1)

Country Link
GB (1) GB2507416B (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110254344A (en) * 2019-06-17 2019-09-20 广州小鹏汽车科技有限公司 A kind of management method and device of atmosphere lamp effect

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060220578A1 (en) * 2005-03-31 2006-10-05 Samsung Sdi Co., Ltd. Organic light emitting display and method of driving the same
US20080036872A1 (en) * 2006-07-06 2008-02-14 Seiko Epson Corporation Image processing system, display device, program, and information recording medium

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060220578A1 (en) * 2005-03-31 2006-10-05 Samsung Sdi Co., Ltd. Organic light emitting display and method of driving the same
US20080036872A1 (en) * 2006-07-06 2008-02-14 Seiko Epson Corporation Image processing system, display device, program, and information recording medium

Also Published As

Publication number Publication date
GB201317971D0 (en) 2013-11-27
GB2507416B (en) 2015-02-25

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