Ambient Light Measurement in Semiconductor Display Devices
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Solution Overview
Problem
Conventional semiconductor devices and electronic apparatuses struggle to accurately calculate ambient-light illuminance when the illuminance sensor is placed on the backside of a display panel, as it is irradiated with both ambient light and display light, making it difficult to subtract display light emissions effectively.
Innovation Solution
A semiconductor device with a light measuring instrument opposite the display surface, a storage device for synchronized measurements during shorter and longer measurement periods, and a calculation unit to determine light emission illuminance and subtract it from ambient light measurements, ensuring accurate ambient-light illuminance calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the illuminance sensor is disposed on the backside of the display panel, then the display area can be increased and entire-surface display is enabled, but the sensor is irradiated with both ambient light and display light, making it difficult to accurately measure ambient-light illuminance
Solution Approach 1:
The measurement period is segmented into multiple sub-frames, with each sub-frame corresponding to a specific pixel row's display period. The illuminance sensor performs measurements at different timing for different sub-frames, allowing separation of ambient light and display light components through temporal segmentation of the measurement process
Solution Approach 2:
The control unit stores in advance the correspondence between sub-frames and pixel rows, and pre-determines the measurement timing for each sub-frame based on the display period of corresponding pixel rows. This preliminary setup enables accurate synchronization between display output and sensor measurement, facilitating precise subtraction of display light from total light
2Quantity of substance
If the illuminance sensor measures light during the display's ON/OFF periods, then the measurement can capture both ambient and display light, but it becomes difficult to accurately subtract display light to obtain ambient-light illuminance
Solution Approach 1:
The display panel operates with periodic ON/OFF cycles for different pixel rows, and the illuminance sensor performs measurements at specific periods corresponding to these cycles. By synchronizing measurements with the periodic display refresh cycles and using the stored sub-frame to pixel row correspondence, the system can identify and subtract display light contributions at each period, accurately isolating ambient light
Solution Approach 2:
The control unit uses feedback from the display control signals to determine when each pixel row is being displayed, and adjusts the measurement timing accordingly. The stored correspondence between sub-frames and pixel rows provides feedback information that enables the sensor to measure at optimal moments, allowing accurate separation of ambient and display light components
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for more accurate calculation of ambient-light illuminance by distinguishing between ambient and display light emissions, enhancing the precision of illuminance measurement.
Implementation Method 1
a light measuring instrument disposed opposite the display surface of a display panel provided with a self-emission element, and disposed for measuring the ambient-light illuminance of the display panel
Data Source
AI summary
A semiconductor device includes the following: a light measuring instrument disposed opposite the display surface of a display panel provided with a self-emission element, and disposed for measuring the ambient-light illuminance of the display panel; a storage device configured to store a plurality of first measurements measured by the light measuring instrument in synchronization with a synchronizing signal of the display panel during a plurality of first measurement periods that are shorter than an ON/OFF period of the self-emission element; and a calculation unit configured to calculate the light emission illuminance of the self-emission element in accordance with the plurality of first measurements stored in the storage device, and configured to calculate the ambient-light illuminance by subtracting a value based on the light emission illuminance from a second measurement measured by the light measuring instrument during a second measurement period that is longer than the plurality of first measurement periods.