Dual-Display Multiplexing to Improve XR Bonding Yield
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Solution Overview
Problem
Conventional head-mounted extended reality devices face challenges in adjusting interpupillary distance (IPD) due to the need for separate display screens for the left and right eyes, leading to increased power consumption, size, and cost, as well as difficulties in connecting high-resolution displays with a large number of small connection pins, which can reduce bonding yield and increase manufacturing costs.
Innovation Solution
The display apparatus employs a multiplexer and demultiplexer on each substrate to reduce the number of connection pins, allowing for larger pin sizes and improved bonding yield, while eliminating the need for multiple layers of flexible circuit boards, thereby reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate display screens are provided for left and right eyes with high resolution, then display quality is improved, but the number of connection pins increases leading to reduced bonding yield
Solution Approach 1:
The patent combines the connection interfaces of two separate display screens into a single flexible circuit board. The multiplexer on the first substrate and demultiplexer on the second substrate enable multiple signal lines to be transmitted through a reduced number of connection pins, merging what would traditionally require separate connection interfaces into one unified connection structure.
Solution Approach 2:
The patent changes the parameter of connection pin quantity from N pins per screen to M pins total for both screens, where M < N. This parameter change is achieved through the multiplexer/demultiplexer configuration that allows multiple signal lines to share fewer physical connection pins, directly addressing the bonding yield issue while maintaining high-resolution display capabilities.
2Reliability
If the number of connection pins is reduced, then bonding yield is improved, but the number of signal lines that can be transmitted is limited
Solution Approach 1:
The multiplexer on the first substrate performs periodic switching to route different signal lines through the same M connection pins at different time intervals. This time-division multiplexing allows N signal lines to be transmitted sequentially through M pins, achieving both reduced pin count for improved bonding yield and full signal line capacity for high-resolution displays.
Solution Approach 2:
The flexible circuit board with M connection pins serves as an intermediary between the two substrates. The multiplexer and demultiplexer act as signal routing intermediaries that enable N signal lines to be transmitted through the M-pin connection interface, resolving the contradiction between pin count reduction and signal line capacity.
3Adaptability or versatility
If multiple layers of flexible circuit boards are used to connect display modules, then connection flexibility is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges multiple flexible circuit board layers into a single flexible circuit board structure. By implementing the multiplexer/demultiplexer configuration on this single board, the patent eliminates the need for multiple stacked flexible circuit boards, thereby reducing manufacturing complexity and cost while preserving the flexibility needed for head-mounted display configurations.
Solution Approach 2:
The single flexible circuit board is designed with multi-functionality, serving both as the mechanical connector and as the signal routing platform. The multiplexer/demultiplexer integration allows this single board to perform the functions that would traditionally require multiple separate layers, achieving universality that reduces both manufacturing complexity and maintains adaptability.
Data Source
AI summary
The present disclosure relates to a display apparatus and an extended reality device. The display apparatus comprises: a first display module, a second display module and a first flexible circuit board. The first display module comprises a first substrate, N first signal lines and a multiplexer being arranged on the first substrate, a first connection end of the first flexible circuit board being fixed on the first substrate, and the multiplexer being electrically connected between the first connection end of the first flexible circuit board and the first signal lines. The second display module comprises a second substrate, N second signal lines and a first demultiplexer being arranged on the second substrate, a second connection end of the first flexible circuit board being fixed to the second substrate, and the first demultiplexer being electrically connected between the second connection end of the first flexible circuit board and the second signal lines. The number of electrical connection lines in the first flexible circuit board is M, M being less than N, and M and N being both positive integers.