30-05-2012, 04:46 PM
The Virtual Retinal Display
[attachment=23597]
Introduction
The Virtual Retinal Display (VRD) is a new technology for creating visual images. It was
developed at the Human Interface Technology Laboratory (HIT Lab) by Dr. Thomas A. Furness
III. The VRD creates images by scanning low power laser light directly onto the retina. This
special method results in images that are bright, high contrast and high resolution. Current
prototypes of the system produce full color images at a true 640 by 480 resolution.
The technologies of virtual reality (VR) and augmented reality (AR) are the new paradigm
for visual interaction with graphical environments. The features of VR are interactivity and
immersion. To achieve these features, a visual display that is high resolution and wide field of
view is necessary. For AR a visual display that allows ready viewing of the real world, with
superimposition of the computer graphics is necessary. Current display technologies require
compromises that prevent full implementation of VR and AR. A new display technology called the
Virtual Retinal Display (VRD) has been created. The VRD has features that can be optimized for
the human computer interfaces.
VRD versus Pixel Based Displays
The mode of illumination of the retina by the VRD is quite different from conventional
screens. The scanning mechanism rapidly sweeps a spot of light over the retina. The spot passes
over the retinel (an area analogous to the retinal area where a pixel is focused ). Thus the retinel is
not illuminated uniformly in time. Further, the actual time of illumination is extremely brief (40
nanoseconds). There is only a brief spike of illumination of a portion of the retina for each refresh
cycle of the display. The light from the VRD is coherent and very narrow band in wavelength. The
VRD can be configured such that the spot actually overlaps retinels or is smaller than a retinal area.
Table 1 summarizes the differences between the pixel based display and the VRD.
Methods
For our safety analysis, we measured the light power output of the VRD when it was
creating images. We had subjects adjust the brightness of the VRD images in a see through
configuration that allowed them to see an image on a conventional CRT screen. The VRD image
brightness was adjusted so that it appeared equal to the brightness of the CRT images.
Results
In our safety analysis, all subjects were readily able to match the VRD brightness to the
bightness of the control images. Power output values of the VRD varied from 50 to 1200
nanowatts. Typical VRD images are on the order of 300 nanowatts. Typical VRD images are also
readily viewed superimposed on ambient room light. Normal subjects are all able to see VRD
images clearly. All 8 formally tested subjects were able to resolve VRD targets within one line of
CRT or paper targets. 4 were able to resolve targets at the same resolution. 5 of 8 normal subjects
reported VRD images to be “as sharp” or “sharper” than CRT or paper targets. There was no
distortion detected with astigmatism stars or Amsler grids.
Conclusions
The VRD is a safe new display technology. The power levels recorded from the system are several
orders below the power levels prescribed by the American National Standard. The VRD readily
creates images that can be easily seen in ambient roomlight and it can create images that can be seen
in ambient daylight. The combination of high brightness and contrast and high resolution make the
VRD an ideal candidate for use in a surgical display. Further, tests show strong potential for the
VRD to be a display technology for patients with low vision.
[attachment=23597]
Introduction
The Virtual Retinal Display (VRD) is a new technology for creating visual images. It was
developed at the Human Interface Technology Laboratory (HIT Lab) by Dr. Thomas A. Furness
III. The VRD creates images by scanning low power laser light directly onto the retina. This
special method results in images that are bright, high contrast and high resolution. Current
prototypes of the system produce full color images at a true 640 by 480 resolution.
The technologies of virtual reality (VR) and augmented reality (AR) are the new paradigm
for visual interaction with graphical environments. The features of VR are interactivity and
immersion. To achieve these features, a visual display that is high resolution and wide field of
view is necessary. For AR a visual display that allows ready viewing of the real world, with
superimposition of the computer graphics is necessary. Current display technologies require
compromises that prevent full implementation of VR and AR. A new display technology called the
Virtual Retinal Display (VRD) has been created. The VRD has features that can be optimized for
the human computer interfaces.
VRD versus Pixel Based Displays
The mode of illumination of the retina by the VRD is quite different from conventional
screens. The scanning mechanism rapidly sweeps a spot of light over the retina. The spot passes
over the retinel (an area analogous to the retinal area where a pixel is focused ). Thus the retinel is
not illuminated uniformly in time. Further, the actual time of illumination is extremely brief (40
nanoseconds). There is only a brief spike of illumination of a portion of the retina for each refresh
cycle of the display. The light from the VRD is coherent and very narrow band in wavelength. The
VRD can be configured such that the spot actually overlaps retinels or is smaller than a retinal area.
Table 1 summarizes the differences between the pixel based display and the VRD.
Methods
For our safety analysis, we measured the light power output of the VRD when it was
creating images. We had subjects adjust the brightness of the VRD images in a see through
configuration that allowed them to see an image on a conventional CRT screen. The VRD image
brightness was adjusted so that it appeared equal to the brightness of the CRT images.
Results
In our safety analysis, all subjects were readily able to match the VRD brightness to the
bightness of the control images. Power output values of the VRD varied from 50 to 1200
nanowatts. Typical VRD images are on the order of 300 nanowatts. Typical VRD images are also
readily viewed superimposed on ambient room light. Normal subjects are all able to see VRD
images clearly. All 8 formally tested subjects were able to resolve VRD targets within one line of
CRT or paper targets. 4 were able to resolve targets at the same resolution. 5 of 8 normal subjects
reported VRD images to be “as sharp” or “sharper” than CRT or paper targets. There was no
distortion detected with astigmatism stars or Amsler grids.
Conclusions
The VRD is a safe new display technology. The power levels recorded from the system are several
orders below the power levels prescribed by the American National Standard. The VRD readily
creates images that can be easily seen in ambient roomlight and it can create images that can be seen
in ambient daylight. The combination of high brightness and contrast and high resolution make the
VRD an ideal candidate for use in a surgical display. Further, tests show strong potential for the
VRD to be a display technology for patients with low vision.