Using Different Light Colors to Detect Touches on Screens

This 2011 patent describes a system that uses two different colors of light to accurately detect where an object, like a finger, touches a screen or surface.

What it covers

This patent details a system for detecting the position of objects within a specific area, like a display screen. It works by using an optical detector to capture images. The system shines light of a first wavelength (color) into the area, capturing a first image. Then, it shines light of a second wavelength (another color) into the same area and captures a second image. The core idea is to process these two images, specifically by subtracting the second image's signal from the first. This subtraction helps to eliminate false signals, such as light that reflects directly back from the surface itself, and can also help identify the object based on how it interacts with the different light colors. For example, if you touch a screen, the system can figure out exactly where your finger is by analyzing the differences in the light patterns.

What it doesn't cover

• —Systems that only use a single wavelength or color of light for detection.
• —Detection systems that do not involve subtracting image signals to isolate object interaction.
• —Methods that rely on sound waves or electrical capacitance for touch detection.
• —Systems that cannot differentiate between direct reflections and reflections from a specific edge member.
• —Position detection that does not involve generating an image from an optical detector.

The clever bit

The clever part is using two different colors of light and subtracting the resulting images. This subtraction technique helps to filter out unwanted light signals, like those bouncing directly off the screen surface, making it easier to pinpoint the actual touch object. It also allows for object identification based on unique optical properties when interacting with different light colors.

Why it matters

This patent explores a method for improving the accuracy of touch detection systems, particularly for displays and interactive whiteboards. By using multiple wavelengths of light, it aims to reduce errors caused by ambient light or direct reflections, leading to more reliable touch input. This was important as touch technology was becoming more prevalent in consumer electronics and interactive displays.

Real-world examples

• 1.Interactive digital whiteboards
• 2.Touchscreen displays for computers
• 3.Some early optical touch detection systems