U.S. patent application number 15/811337 was filed with the patent office on 2018-05-17 for method and device for current compensation for an electroluminescent display.
The applicant listed for this patent is INT TECH CO., LTD.. Invention is credited to YEN-JEN LAI, CHIN-RUNG YAN, YI WEI YAN.
Application Number | 20180137812 15/811337 |
Document ID | / |
Family ID | 62108012 |
Filed Date | 2018-05-17 |
United States Patent
Application |
20180137812 |
Kind Code |
A1 |
YAN; YI WEI ; et
al. |
May 17, 2018 |
METHOD AND DEVICE FOR CURRENT COMPENSATION FOR AN
ELECTROLUMINESCENT DISPLAY
Abstract
A method for current compensation in an electroluminescent (EL)
display is provided. The method includes measuring an intensity of
light of a pixel unit, identifying a pixel unit to be one that
needs compensation if the measured intensity exceeds a
predetermined threshold, determining the magnitude of a
compensation current, and providing an image data corresponding to
the magnitude of the compensation current to the identified pixel
unit.
Inventors: |
YAN; YI WEI; (TAICHUNG CITY,
TW) ; YAN; CHIN-RUNG; (HSINCHU CITY, TW) ;
LAI; YEN-JEN; (HSINCHU COUNTY, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INT TECH CO., LTD. |
HSINCHU COUNTY |
|
TW |
|
|
Family ID: |
62108012 |
Appl. No.: |
15/811337 |
Filed: |
November 13, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62421435 |
Nov 14, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/3248 20130101;
G09G 3/3208 20130101; G09G 2300/0819 20130101; G09G 3/3611
20130101; G09G 2330/02 20130101; H01L 51/5036 20130101; G09G
2320/0233 20130101; G09G 2320/029 20130101; H01L 29/78 20130101;
G09G 3/2092 20130101; G09G 2300/0439 20130101; H01L 23/528
20130101; G09G 2320/045 20130101; H01L 27/3211 20130101; G09G
2300/026 20130101; G06F 3/1446 20130101; G09G 2310/0278 20130101;
G09G 2320/0204 20130101; H01L 29/41733 20130101; H01L 27/3244
20130101; G09G 3/30 20130101 |
International
Class: |
G09G 3/3208 20060101
G09G003/3208 |
Claims
1. A method for current compensation in an electroluminescent (EL)
display, the method comprising: measuring an intensity of light of
a pixel unit; identifying a pixel unit to be one that needs
compensation if the measured intensity exceeds a predetermined
threshold; determining the magnitude of a compensation current; and
providing an image data corresponding to the magnitude of the
compensation current to the identified pixel unit.
2. The method according to claim 1 further comprising: providing an
image data of a predetermined grayscale to a pixel unit under
measurement before measuring an intensity of light of the pixel
unit.
3. The method according to claim 2, wherein identifying a pixel
unit further comprises: comparing the measured intensity with the
predetermined grayscale.
4. The method according to claim 2, wherein determining the
magnitude of a compensation current further comprises: calculating
a difference between the measured intensity and the predetermined
grayscale; and converting the difference into the magnitude of a
compensation current.
5. The method according to claim 1 further comprising: determining
the location of the identified pixel unit.
6. The method according to claim 5, wherein the pixel unit is
driven by a gate driver integrated circuit (IC) and a source driver
IC, further comprising: providing information on the location of
the identified pixel unit to the gate driver IC; and providing
information on the magnitude of a compensation current to the
source driver IC.
7. A method for current compensation, the method comprising:
obtaining real-time image data on mura of a display of a mobile
device; storing the real-time image data on mura in a memory of the
mobile device; and determining pixels that need compensation based
on the real-time image data on mura.
8. The method according to claim 7, wherein obtaining real-time
image data on mura of a display of a mobile device comprises:
taking a picture of an image displayed by the display of the mobile
device.
9. The method according to claim 7 further comprising: updating in
the memory an original image data on mura with the real-time image
data on mura.
10. The method according to claim 9, wherein the original image
data on mura is stored in the memory when the mobile device is
manufactured.
11. The method according to claim 9, wherein the original image
data on mura includes a previously stored image data on mura.
12. The method according to claim 7, wherein the memory includes a
flash IC.
13. An electroluminescent (EL) display, comprising: a substrate; an
EL device layer over the substrate, the EL device layer including a
number of EL devices; and an optical sensor layer over the
substrate, the optical sensor layer including first sensors
arranged in a first direction and second sensors arranged in a
second direction, the first sensors and the second sensors
intersecting one another at intersection points, wherein the
optical sensor layer is configured to identify a region of the EL
device layer for compensation by detecting impedance at each
intersection point from a reference point.
14. The EL display according to claim 13, wherein the substrate
includes one of a low temperature polysilicon (LTPS) substrate and
an indium gallium zinc oxide (IGZO) substrate.
15. The EL display according to claim 13, wherein the EL device
includes one of an organic light emitting diode (OLED), a micro LED
and a quantum dot LED (QLED).
16. The EL display according to claim 13, wherein the optical
sensor layer has a same size as the substrate.
17. The EL display according to claim 13, wherein the optical
sensor layer 33 is made of a relatively high transparent
material.
18. The EL display according to claim 13 further comprising a
measuring module configured to measure an intensity of light of an
EL device.
18. EL display according to claim 18 further comprising an
analyzing module configured to identify an EL device to be one that
needs compensation if the measured intensity exceeds a
predetermined threshold.
20. The EL display according to claim 19 further comprising a
calculating module configured to determine the magnitude of a
compensation current for the identified EL device.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. provisional
application Ser. No. 62/421,435, filed Nov. 14, 2016, the
disclosure of which is hereby incorporated herein by reference.
BACKGROUND
[0002] In an active matrix organic light emitting diode (AMOLED)
display, each pixel unit includes a capacitor for storing data so
that the pixel unit can be maintained at an illumination state.
Such driving mechanism is suitable for the development of
large-size, high-resolution displays. As a result, AMOLED has
become increasingly important in the research and development of
advanced displays such as flexible displays. For an OLED device,
its luminescence is determined by the magnitude of current flowing
through the OLED device, which in turn is determined by the thresh
old voltage Vth of the OLED device. For a display that comprises a
plurality of the OLED devices, the magnitude of current may be
different from one OLED device to another due to variation in Vth,
resulting in a non-uniform luminescence across the pixel units. The
threshold variation may result from manufacturing factors or device
aging.
SUMMARY
[0003] Embodiments of the present invention provide a method for
current compensation in an electroluminescent (EL) display. The
method includes measuring an intensity of light of a pixel unit,
identifying a pixel unit to be one that needs compensation if the
measured intensity exceeds a predetermined threshold, determining
the magnitude of a compensation current, and providing an image
data corresponding to the magnitude of the compensation current to
the identified pixel unit.
[0004] In an embodiment, the method further includes providing an
image data of a predetermined grayscale to a pixel unit under
measurement before measuring an intensity of light of the pixel
unit.
[0005] In another embodiment, the operation of identifying a pixel
unit further includes comparing the measured intensity with the
predetermined grayscale.
[0006] In yet another embodiment, the operation of determining the
magnitude of a compensation current further includes calculating a
difference between the measured intensity and the predetermined
grayscale, and converting the difference into the magnitude of a
compensation current.
[0007] In still another embodiment, the method further includes
determining the location of the identified pixel unit.
[0008] In yet still another embodiment, wherein the pixel unit is
driven by a gate driver integrated circuit (IC) and a source driver
IC, the method further includes providing information on the
location of the identified pixel unit to the gate driver IC, and
providing information on the magnitude of a compensation current to
the source driver IC.
[0009] Some embodiments of the present invention provide a method
for current compensation. The method includes obtaining real-time
image data on mura of a display of a mobile device, storing the
real-time image data on mura in a memory of the mobile device, and
determining pixels that need compensation based on the real-time
image data on mura.
[0010] In an embodiment, the operation of obtaining real-time image
data on mura of a display of a mobile device includes taking a
picture of an image displayed by the display of the mobile
device.
[0011] In another embodiment, the method further includes updating
in the memory an original image data on mura with the real-time
image data on mura.
[0012] In yet another embodiment, the original image data on mura
is stored in the memory when the mobile device is manufactured.
[0013] In still another embodiment, the original image data on mora
includes a previously stored image data on mura.
[0014] In yet still another embodiment, the memory includes a flash
IC.
[0015] Embodiments of the present invention also provide an
electroluminescent (EL) display. The EL display includes a
substrate, an EL device layer over the substrate, and an optical
sensor layer over the substrate. The EL device layer includes a
number of EL devices. The optical sensor layer includes first
sensors arranged in a first direction and second sensors arranged
in a second direction. The first sensors and the second sensors
intersect one another at intersection points. The optical sensor
layer is configured to identify a region of the EL device layer for
compensation by detecting impedance at each intersection point from
a reference point.
[0016] In an embodiment, the substrate includes one of a low
temperature polysilicon (LTPS) substrate and an indium gallium zinc
oxide (IGZO) substrate.
[0017] In another embodiment, the EL device includes one of an
organic light emitting diode (OLED), a micro LED and a quantum dot
LED (QLED).
[0018] In yet another embodiment, the optical sensor layer has a
same size as the substrate.
[0019] In still another embodiment, The EL display according to
claim 13, wherein the optical sensor layer 33 is made of a
relatively high transparent material.
[0020] In yet still another embodiment, the EL display further
includes a measuring module configured to measure an intensity of
light of an EL device. In addition, the EL display includes an
analyzing module configured to identify an EL device to be one that
needs compensation if the measured intensity exceeds a
predetermined threshold. Moreover, the EL display includes a
calculating module configured to determine the magnitude of a
compensation current for the identified EL device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Aspects of the present disclosure are best understood from
the following detailed description when read with the accompanying
figures. It is noted that, in accordance with the standard practice
in the industry, various features are not drawn to scale. In fact,
the dimensions of the various features may be arbitrarily increased
or reduced for clarity of discussion.
[0022] FIG. 1 is a flow diagram of a method for current
compensation in an electroluminescent (EL) display, in accordance
with some embodiments.
[0023] FIG. 2 is a block diagram of a system comprising a device
for current compensation, in accordance with some embodiments.
[0024] FIG. 3 is a cross-sectional diagram of an EL display, in
accordance with some embodiments.
[0025] FIG. 4 is a schematic diagram showing function of an optical
sensor layer in the EL display illustrated in FIG. 3, in accordance
with some embodiments.
[0026] FIGS. 5A and 5B are diagrams showing an optical sensor layer
in the EL display illustrated in FIG. 3, in accordance with some
embodiments.
[0027] FIG. 6A is a schematic diagram of a system for obtaining
real-time image data on mura, in accordance with some
embodiments.
[0028] FIG. 6B is a schematic block diagram showing a method of
updating image data on mura, in accordance with some
embodiments.
[0029] FIG. 7 is a flow diagram of a method for current
compensation in an electroluminescent (EL) display, in accordance
with some embodiments.
DETAILED DESCRIPTION
[0030] The following disclosure provides many different
embodiments, or examples, for implementing different features of
the provided subject matter. Specific examples of components and
arrangements are described below to simplify the present
disclosure. These are, of course, merely examples and are not
intended to be limiting. For example, the formation of a first
feature over or on a second feature in the description that follows
may include embodiments in which the first and second features are
formed in direct contact, and may also include embodiments in which
additional features may be formed between the first and second
features, such that the first and second features may not be in
direct contact. In addition, the present disclosure may repeat
reference numerals and/or letters in the various examples. This
repetition is for the purpose of simplicity and clarity and does
not in itself dictate a relationship between the various
embodiments and/or configurations discussed.
[0031] Further, it will be understood that when an element is
referred to as being "connected to" or "coupled to" another
element, it may be directly connected to or coupled to the other
element, or intervening elements may be present.
[0032] FIG. 1 is a flow diagram of a method for current
compensation in an electroluminescent (EL) display, in accordance
with some embodiments.
[0033] Referring to FIG. 1, in operation 11, intensity of light of
each pixel unit in a display is measured. The display may include
an electroluminescent (EL) display, for example, an active matrix
organic light emitting diode (AMOLED) display. Moreover, the
display may include pixel units, a gate driver integrated circuit
(IC) and a source driver IC. The pixel units are arranged in, for
example, an N.times.M matrix. The gate driver IC selects one or
more rows of pixel units in the N rows of pixel units, while the
source driver provides image data to selected pixel units in the M
columns of pixel units. Each of the pixel units includes an EL
device. The EL device may include, for example, a current-driven
element that may further include an organic light emitting diode
(OLED), a micro LED or a quantum dot LED (QLED).
[0034] The intensity of light of a pixel unit is a function of
current that flows through the EL device of the pixel unit.
Moreover, the intensity may be different from one pixel unit to
another due to variation in the Vth of the EL device. In an
embodiment, to measure the intensity, an image data of a
predetermined grayscale is provided from the source driver IC to
the pixel units.
[0035] Next, in operation 12, it is determined, based on the
measured intensity of light in each pixel unit, whether current
distribution across the array of pixel units is uniform. In an
embodiment, if the measured intensity of a pixel unit, when
compared with the predetermined grayscale, exceeds a predetermined
threshold, the pixel unit is identified as one that needs current
compensation.
[0036] If in operation 12 it is determined that the current
distribution is uniform, then in operation 13, a state of Mura is
updated.
[0037] In general, a Mura effect means a non-uniform or uneven
display surface caused by an imperfect illumination of pixel units.
The Mura effect may appear to be brighter or darker, less
saturated, poor in contrast or from the general display
presentation deviating areas, spots or pixels.
[0038] Therefore, if in operation 12 the current distribution is
not uniform, then in operation 14, the location of a pixel unit
that is identified in operation 12 is determined.
[0039] In operation 15, the magnitude of a compensation current for
the pixel unit of interest, i.e., the pixel unit identified in
operation 12, is determined. In an embodiment, an offset between
the measured intensity and the predetermined grayscale is
calculated to determine an amount of compensation. The amount of
compensation is then converted into an image data corresponding to
the magnitude of the compensation current.
[0040] In operation 16, information on the magnitude of a
compensation current for the pixel unit of interest is provided to
a source driver IC. In addition, in operation 17, information on
the location of the pixel unit of interest is provided to a gate
driver IC.
[0041] Subsequently, in operation 18, the pixel unit of interest is
compensated based on the image data.
[0042] FIG. 2 is a block diagram of a system 20 comprising a device
21 for current compensation, in accordance with some
embodiments.
[0043] Referring to FIG. 2, the system 20 includes a display 26 as
well as the device 21. The display 26, which may be an EL display,
includes an array of pixel units 260 and driver ICs 264. The device
21, configured to compensate the display 26 for non-uniform current
distribution, includes a controller 210, a measuring module 212, an
analyzing module 215, a calculating module 218 and a memory
217.
[0044] The measuring module 212, under the control of the
controller 210, measures intensity of light of the array of pixel
units 260. In operation, the controller 210 commands the driver ICs
264 to provide an image data of a predetermined grayscale to the
array of pixel units 260 to facilitate measurement by the measuring
module 212. A value of the predetermined grayscale may be stored in
the memory 217.
[0045] In response to a measuring result, the analyzing module 215
determines whether a pixel unit needs to be compensated by, for
example, comparing a measured intensity with the predetermined
grayscale. If such a pixel unit is identified, the location of the
identified pixel unit is stored in the memory 217.
[0046] The calculating module 218, based on a difference between
the measured intensity and the predetermined grayscale, determines
the amount of compensation and then converts the amount of
compensation into an image data corresponding to the magnitude of a
compensation current.
[0047] The controller 210, based on information on the location of
the identified pixel unit and the magnitude of compensation current
for the identified pixel unit, commands the driver ICs to provide
the image data to the pixel units at the location.
[0048] The device 21 in some embodiment may be merged into the
display 26, as will be discussed with reference to FIGS. 3 to 5
below.
[0049] FIG. 3 is a cross-sectional diagram of an EL display 30, in
accordance with some embodiments.
[0050] Referring to FIG. 3, the EL display 30 includes a substrate
31, an EL device layer 32 and an optical sensor layer 33. The
substrate 31 may include a low temperature polysilicon (LTPS)
substrate or an indium gallium zinc oxide (IGZO) substrate. The EL
device layer 32, disposed between the substrate 31 and the optical
sensor layer 33, includes EL devices that may include OLEDs micro
LEDs or quantum dot LEDs (QLEDs). The optical sensor layer 33 is
configured to detect if non-uniform illumination such as Mura
effect occurs in the EL device layer 32 and, if any, determines a
region of interest in the EL device layer 32. In an embodiment, the
optical sensor 33 is integrated into a touch panel (not shown) of
the EL display 30.
[0051] FIG. 4 is a schematic diagram showing function of the
optical sensor layer 33 in the EL display 30 illustrated in FIG. 3,
in accordance with some embodiments.
[0052] Referring to FIG. 4, a region 320 in the EL device layer 32
is detected as a region of non-uniform illumination region (shown
in a dashed arrow). To detect a non-uniform illumination region,
pixel units in the EL display 30 are provided with a predetermined
grayscale value. Sensors in the optical sensor layer 33 detect if
there is a region of interest and, if any, report the location of
the region of interest and an optical difference in intensity of
light to a controller. The region may be as small as a single pixel
unit, or as large as the entire array of pixel units. Subsequently,
a converter converts the optical difference into an image data. The
controller commands driver ICs to adjust the region of interest
based on the image data. The method and device for compensation are
similar to or same as those described and illustrated with FIGS. 1
and 2, and therefore are not further discussed.
[0053] FIGS. 5A and 5B are diagrams showing the optical sensor
layer 33 in the EL display 30 illustrated in FIG. 3, in accordance
with some embodiments.
[0054] Referring to FIG. 5A, the optical sensor layer 33 includes
first sensors 51 and second sensors 52. The first sensors 51 extend
in a first direction, while the second sensors 52 extend in a
second direction substantially orthogonal to the first direction.
As a result, the first sensors 51 and the second sensors 52
intersect one another at intersection points. In an embodiment, the
optical sensor layer 33 has substantially the same size as a touch
panel of the EL display 30. Moreover, the optical sensor layer 33
is made of a relatively high transparent material to prevent the
touch panel from optical loss. The first sensors 51 and the second
sensors 52 in the optical sensor layer 33 detect the resistance at
each intersection point from a reference point. The reference point
may be predetermined by a user of the EL display 30. A linear
relationship exists between the resistance of an intersection point
and a distance between the intersection point and the reference
point. However, for a non-uniform illumination region, such as the
region 320 shown in FIG. 5B, no such linear relationship may exist.
Accordingly, when the EL device layer 32 emits light, a non-uniform
illumination region is detected. The location of the region of
interest and an image data corresponding to the amount of optical
difference are sent to driver ICs for compensating the region of
interest.
[0055] FIG. 5B thus illustrates a method for obtaining image data
on mura by detecting non-uniform illumination regions. In other
embodiments, as will be discussed with reference to FIGS. 6A and
6B, image data on mura may be obtained in real time by taking an
image displayed by a display device.
[0056] FIG. 6A is a schematic diagram of a system 60 for obtaining
real-time image data on mura, in accordance with some
embodiments.
[0057] Referring to FIG. 6A, the system 60 includes a camera 61 and
a mobile device 67. The camera 61, which may include a monocular
camera, a digital camera, or a cellphone camera, is configured to
obtain image data on mura of the mobile device 67. A commercially
available camera may have a resolution of approximately 1.2 mega
pixels or higher, which is sufficient to support the system 60. In
operation, the mobile device 67 is powered on for the camera 61 to
take a picture of an image displayed by the mobile device 67. The
system 60 alleviates optical interference from ambient light, and
facilitates adjustments in the x, y and z coordinates to ensure the
quality of image data on mura.
[0058] FIG. 6B is a schematic block diagram showing a method of
updating image data on mura, in accordance with some
embodiments.
[0059] Referring to FIG. 6B, real-time image data on mura 62
obtained by the camera 61 is sent to the mobile device 67. In the
present embodiment, a processor 64 on a main board of the mobile
device 67 receives the real-time image on mura 62 and determines
non-uniform illumination regions, if any, in the display of the
mobile device 67. The real-time image on mura 62 is then stored via
a driver IC 66 into a memory 68 such as a flash IC, and may update
an original image data on mura 680 in the memory 68. In an
embodiment, the original image data on mura 680 refers to one that
has been stored in the memory 68 by a manufacturer when the mobile
device 67 was made. In another embodiment, the original image data
on mum 680 refers to a previously stored real-time image data on
mura. The original image data on mura 680, in particular those
stored by the manufacturer, may not reflect the current state of
mura when the mobile device 67 has been used for a while. As a
result, the current state of mura may be significantly different
from the state originally stored. With the updated image data on
mura, a more precise compensation can be made for pixels in a
non-uniform illumination region.
[0060] FIG. 7 is a flow diagram of a method for current
compensation in an electroluminescent (EL) display, in accordance
with some embodiments.
[0061] Referring to FIG. 7, the method is similar to that
illustrated in FIG. 1 except, for example, operations 71, 72 and
73. In operation 71, real-time image data on mura of a mobile
device is obtained. Next, in operation 72, the real-time image data
on mura is stored in a memory of the mobile device and updates an
original image data on mura. Subsequently, in operation 73, it is
determined if current distribution is uniform. In an embodiment, to
determine if current distribution is uniform, the real-time image
data on mura is compared against the original image data on mura.
Based on a comparison result, it can be determined whether the
intensity of light of a pixel unit in an illumination region
relative to the real-time image data on mura is changed.
Accordingly, the intensity of light of the pixel unit is measured
by reference to the comparison result in order to determine if
current distribution is uniform.
[0062] In operation 73, if the current distribution is determined
to be uniform, then the operations 71 and 72, when necessary, are
repeated. If not uniform, a compensation process based on the
operations 14 to 18 previously discussed with reference to FIG. 1
may be performed.
[0063] The foregoing outlines features of several embodiments so
that those skilled in the art may better understand the aspects of
the present disclosure. Those skilled in the art should appreciate
that they may readily use the present disclosure as a basis for
designing or modifying other processes and structures for carrying
out the same purposes and/or achieving the same advantages of the
embodiments introduced herein. Those skilled in the art should also
realize that such equivalent constructions do not depart from the
spirit and scope of the present disclosure, and that they may make
various changes, substitutions, and alterations herein without
departing from the spirit and scope of the present disclosure.
* * * * *