Eyeglass Free Display

Vision Correcting Displays

Goodbye to corrective lenses…..

A new computational display technology has been developed by the researchers at MIT and Microsoft through which one can adjust any image onto a display and can see clearly without the use of any eyewear.  Combining optics and prefiltering algorithms the display technology comes up with features like high resolution, higher contrast and better efficiency. The advantage of this technology is that it can be used to correct higher order aberrations.

Human Eye and its Test Procedures

Human eye is a simple organ which reacts to light. Being a sense organ it helps in the purpose of vision. The presence of human eye helps in distinguishing different colors. The human eye consists of photosensitive ganglion cells in the retina which helps in receiving light signals that affect the pupil size adjustment, regulation and suppression of the hormones.

Common Test Procedures

1. Eye Chart
2. Color Blind Test
3. Solutions for Eye Correction

Eye Chart:  is one of the method or a simple chart which helps in the measurement of visual acuity. These charts are used by the physicians as an eye test procedure.

Color Blind Test: This test is done to check the color blindness of the human. This test is done to know whether a person can distinguish between the colors.

Eye correction Solutions: To get rid of the eye problems different solutions are available. Some of them are listed below.

• Glasses
• Contacts
• Lasik Treatment

Apart from these corrective methods, researchers of MIT and the University of Berkeley have developed a display known as Eyeglass free display/ Vision Correcting Displays for vision correction avoiding the use of above correction methods.

Vision Correcting Displays

A vision defect is defined as any mismatch that occurs between the focal distance of the eyes. The vision correcting display helps in the simulation of the image at the correct focal distance which will be between the viewer’s eye and the display.

The vision correcting display makes use of algorithms inorder to change any image based on the prescription of the users glass with a light filter placed at the front of the display. The algorithm helps in altering any light from the individual pixels. Due to this, when light passes through the hole of the plastic filter, light rays will reach the retina and will create a sharp image.

The disadvantage of the approach is that simulation of single pixels in the virtual image needs the requirement of multiple pixels. The major condition of the eyeglass free display is that the angle at which light arrives at the simulated image is sharper than the angle at which the light will arrive from the image being displayed on to the screen. So, the pixels which will project the light to the right side of the pupil have to be offset to the left and those pixels that project the light to the left side of the pupil will be having the offset to the right.

Prototype

The prototype developed by the researchers consists of a matrix of pinholes which measures 75 microns in diameter with gaps of 390 microns in width.  This pinhole printed screen is then placed or inserted in between the two layers of the clear acrylic which is then attached to the iPod display. Based on the algorithm and the glass prescription, screen compensates the visual impairment of the person by controlling the intensity and the light direction from the screen pixel.  The technique of deconvolution helps in reversing the optical distortion so that the light passing through the matrix pinhole will be perceived by the user as an image.

Visual correcting display is different from the 3D technology. This eyeglass free display will help in the projection of different images to different other parts of the viewer’s pupil allowing to adjust the screen brightness, resolution of each pixel. Due, to this the image is made clear within the eyes of the user without any corrective lenses.

Illustration of Vision Correcting Displays

Figure 1 shows a conventional 2D display with the focal range of the eye resulting in a blurred image. While the figure 2 shows the multilayered display with prefiltered generation of image allowing better image sharpness and contrast. Figure 3 shows the image contrast being preserved using a light filed approach with the help of lenslet arrays on the screen. 

Advantages

• Higher resolution and contrast than prior approaches
• Leverages off-the-shelf and low-cost parts
• Accounts for range of viewing distances
• Implementations with parallax barriers are brighter
• Implementations with lenslet-based devices have thinner form factors.

Comparison with other displays

Applications

• Can be used in vehicles as display for visual correction.
• Useful in watches, PCs, mobiles as display for visual correction.

References

http://web.media.mit.edu/~gordonw/VisionCorrectingDisplay/SIG2014-VisionCorrectingDisplay.pdf