Objective: Explore different aspects of perception and their implications on display technologies
Perception is most commonly defined as the process of recognizing, organizing, and interpreting sensory information. It deals with the human senses that generate signals from the environment through sight, hearing, touch, smell and taste. Simply put, perception is the process by which we interpret the world around us, forming a mental representation of the environment. This representation is not isomorphic to the world, but is subject to many correspondence differences and errors.
In this lab, you will be using an microcontroller platform to explore different aspects of visual perception. Through both lab sections, you will gain a better understanding of flicker fusion, color mixing standard, and light detection principles.
In this lab, you will be using an microcontroller platform to explore different aspects of visual perception. Through both lab sections, you will gain a better understanding of flicker fusion, color mixing standard, and light detection principles.
Lab Components
- One common cathode RGB LED (http://cdn.sparkfun.com/datasheets/Components/General/YSL-R1047CR4G3BW-F8.pdf)
- Resistors (3*150 Ω, 3*220 Ω)
- Solder-less Protoboard
- Jumper Wires
- Arduino Leonardo
Part 1: Flicker Fusion and the Persistence of Vision
The refresh rate of a display is a commonly talked about metric of display performance. From 60Hz on a common LCD television to the 240Hz refresh rates on high-end gaming monitors, what is the difference? and does it matter? In this part of the lab we will be studying refresh rates and why they are important.
Procedure:
- Write a simple program in Arduino IDE that blinks an LED at 1Hz. You can use any color of the RGB LED. (Please use the 220 Ω resistors between your chosen LED color's anode and the arduino's digital pins).
- Increase the frequency until you can no longer perceive the flickering.
- Confirm the LED is still flashing by waving your hand in front of the LED.
- Now, repeat the experiment using your peripheral vision. Repeat the same experiment for each color of the LED. Does your perception change?
Questions:
- What is the threshold frequency for visibility of flickering that you found (roughly)?
- Is there any noticeable difference in the frequency using your peripheral vision?
- What is the application of flicker fusion in displays?
Part 2: Color Mixing
Displays are comprised of thousands of pixels! Each pixel contains a set of red, green, and blue color elements. Through addressing techniques, precise intensities of all three colors combine in such a way that humans perceive a certain color. In this part of the lab we will be creating a one pixel display using an RGB LED.
Procedure:
- Write a simple program that can mix the RGB LED into whatever color you want given the RGB parameter of that color. ( Use the 150 Ω resistors between each of the colored LED anode and the arduino's digital pins)
- Using your program, display Columbia Blue (155, 221, 255) with your LEDs.
- To simulate how an RGB pixel on a display would change color, set your LED's to white (255, 255, 255) and transition through 5 different colors. At what frequency should you set the pixel's refresh rate?
- Repeat steps (2-3) with the 220 Ω resistors. What do you notice? and what uses would this have in an actual large-area display?
Questions:
- Why is it difficult to find the RGB coordinates that will match exactly with the colors?
- Does the viewing environment (inside vs outside, night vs day, viewing angle, etc) affect your perception of the displayed color? Should it?
- Modern displays have resolutions in the thousands! What are some issues in scaling up your one RGB pixel into an array of thousands?