We’ve preached ad nauseum here on QuickLogic HotSpot about VEE and its ability to increase viewability on displays. We’ve showed pictures and videos, and many of our faithful readers have been able to experience VEE in person on various production smartphones/tablets/pico projectors or on our demo systems. Viewing is easy to prove…but how about quantifying the improvement?
For the scientific-minded amongst you, lets try this:
- I = IM + refl (with reflections on the display [i.e., you are outside, or in bright lighting indoors], this is “viewed brightness”)
- Contrast = im_dark/refl (the contrast of the darkest details, assuming the reflections are overwhelming the darkest details)
- Contrast = im_dark*Gain_VEE/refl (if you improve the dark details with VEE, this is the actual viewing contrast)
- Gain_VEE =(I_VEE_maxstrength/ I_VEE_off)2.2
(2.2 stands for the gamma of sRGB display)
- I_VEE_maxstrength, I_VEE_off are to be measured in spatially large (like half of the screen) darkest area (e.g. I_dark =10 (VEEoff)) of some test image.
Head hurt? Mine does.
Let me put this into real life terms.
Smartphone display OEMs like to say their displays have a contrast ratio of 1500:1, or some figure close to that. However, that specification is under ideal viewing conditions. Once ambient lighting and display reflection are factored, your actual contrast ratio can be closer to 10:1. Don’t believe me? Display a contrast ratio chart to your phone (for instance, from Imatest). During the day, go inside into a dark room, draw the shades, adjust brightness on the phone to about 30% (DON’T use auto brightness), and look. Then, go outside into direct sunlight, adjust brightness to 100%, and then look. Tell me your viewing experience isn’t significantly compromised.
Now, using a combination the formulas above and actual measured data, we are able to calculate that when VEE is used at maximum, it can improve contrast ratio by up to 128X. This means that we can use VEE to improve the actual contrast ratio from 10:1 to 1280:1, making the viewing experience very close to the original ideal spec. Those who have seen it work can attest to this.