Appliance Keypad Light Guide With Selective Key Illumination
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Solution Overview
Problem
Conventional keypad designs for appliances require a large power supply and are not compact due to the need for a light source behind each key, which increases size and complexity.
Innovation Solution
A control unit with a keypad that uses a light guide to illuminate keys and a liquid crystal display grid to selectively restrict or transmit light, allowing for compact and energy-efficient backlighting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light source is placed behind each individual key in the keypad, then each key can be adequately illuminated, but the device size increases and power consumption increases
Solution Approach 1:
Multiple individual light sources are merged into a single light guide that serves all keys. The light guide distributes light from one source to multiple keys through optical coupling, eliminating the need for separate light sources behind each key while maintaining illumination quality.
Solution Approach 2:
A light guide acts as an intermediary between the single light source and the multiple keys. The light guide receives light from the source and distributes it to various keys through optical coupling, enabling indirect illumination without requiring direct light sources at each key location.
2Illumination intensity
If light sources are spaced apart from keys by a diffusion distance, then even illumination is achieved, but the device becomes less compact
Solution Approach 1:
The light guide serves as an intermediary that eliminates the need for diffusion distance. By optically coupling the light guide directly to the keys, uniform illumination is achieved through the light guide's optical properties rather than through spatial separation and diffusion.
Solution Approach 2:
The mechanical approach of spacing light sources from keys with diffusion is replaced by an optical approach using a light guide. The light guide uses optical coupling to achieve uniform illumination without requiring physical separation, thereby reducing device thickness.
3Illumination intensity
If multiple light sources are used for keypad illumination, then each key is well-lit, but power consumption increases
Solution Approach 1:
Multiple light sources are combined into a single light source that illuminates all keys through the light guide. This consolidation reduces the total power consumption while maintaining adequate illumination of all keys through efficient optical distribution.
Solution Approach 2:
A single light guide performs the function of multiple individual light sources by distributing light to multiple keys simultaneously. This multi-functional approach allows one light source to serve multiple purposes (illuminate multiple keys), reducing overall power consumption.
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
The solution enables a compact, energy-efficient, and simplified keypad design that effectively illuminates only necessary keys based on user selections, reducing power consumption and enhancing user guidance.
Implementation Method 1
a light guide disposed adjacent the keys and being configured to direct light from a light source to the keys for illuminating the keys
Implementation Method 2
a liquid crystal display grid disposed between the keypad and light guide, the liquid crystal display grid being configured to selectively restrict light from being transmitted from the light guide to one or more keys
Data Source
AI summary
A control unit including a keypad having a plurality control indicators, a light producing device configured to illuminate the control indicators, and a light blocking device disposed between the control indicators and the light producing device and configured to selectively restrict or transmit light from the light producing device to the control indicators.