InViso eye tracker system
Inviso is latin for “Look
into”
In viso means “In a perceived object”
InViso eye tracker specification
Content
· The eyeglasses are used as an interface between the user and a Android or iPhone application. The app connects through Bluetooth to the eyeglasses.
· 2 LCD displays on the glasses, one for each eye, is used to project a 3D image on a suitable distance in front of the eyes. The glasses in the front are used as mirror lenses to make this possible.
· 2 cameras, one for each eye, are used to measure viewing angle and calculate focus distance.
· The menu system is an application running on an Android or IOS phone that calculates the focus distance and viewing angle. The eyes are used as a “mouse” to navigate in the menus of the application.
· Some of the unique ideas in this design are:
o Eye sight is used as an input to the GUI
o Eye focal length is used as an input to the GUI
o Eyeglasses is a part of the lens-system (mirror lens)
o New type of Fresnel mirror, possible patent opportunity
o New eye scanning technique
1 |
Eye camera chip: OMV7690, 640x480. Size: 2.5 x 2.5 x 3 mm |
|
2 |
Display: KCD-KDCF-AA, 800 x 600. Size: 12 x 9 mm |
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3 |
PCB: With Bluetooth transceiver and micro controller |
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4 |
Battery:, Lithium Ion, 3.7V, 800 mAh. Size:65 x 22 x 6 mm |
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5 |
Lens: Cemented Doublet from Qioptiq. Part.no:322223000 |
|
6 |
Mirror: custom Polycarbonate or Trivex mirror, 50% transparency. Radius = 50 mm |
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7 |
LED for Background light: VLMW322BACA5K8L |
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8 |
Flex Circuit board: 4 layers |
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9 |
Eyeglass frame: half rim Carbon fiber graphite (CFG) with fixed temples |
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Below is a picture from the camera view
of the right eye.
The red field represents the iris moving area and is used to track the iris
leftmost position.
Cubic spline data interpolation can be used to speed up the readings and
increase the precision of the measurement.
Calculate the eye distance
Simplified example how to calculate the viewing x-angle
Calculating Focus distance
Calculating Focus distance error
The graphics for the menu system is transferred to the eyeglasses using Bluetooth from an Android or IOS phone.
Bluetooth requirement
· Bluetooth v3.0 + EDR (Enhanced Data Rate) Class 3 (5m)
· Max transfer rate = 24Mbit/s thru 802.11 link
· Profile: Basic Imaging Profile (BIP) “Image Push” or “Remote Display”, if possible
Bluetooth Bandwidth Requirement
· Image resolution: 800 x 600 pix.
· Update frequency/speed: 5FPS (Frames Per Second) or 0.2s delay
·
Image size 800 x 600 x 3(24bit) x 5FPS =
72Mbit/s! (uncompressed)
Maximum throughput with bluetooth is 24Mbit. (same data is transferred to both
display, image + distance). This requires a compression of more than 2:1. In the
table below there are three different standards to compress images.
Decompression needs a lot of processing and the microprocessor in the glasses
needs to run slow with leaves PNG and JPG as an less attractive option.
Type |
Pros. |
Cons. |
GIF |
· Image is lossless (8-bit) · small amount of serial data flash space · decompr. fast so image displayed quickly · supports binary transparency · good for drawings |
· not for full color photos · 256 different colors per image |
JPG |
· uses much less serial data flash space · full 24-bit color · good for photos |
· decompression time is long · no transparency · compression can be lossy |
PNG |
· full 8-bit transparency · full 24-bit color · good for photos |
· large serial data flash space · decompression takes time |
Example Image 800 x 600 |
Format |
Compressed |
Ratio |
|
BMP |
1.83MB (Uncompressed) |
1:1 |
GIF |
75kB |
1:24 |
|
JPG |
15kB |
1:120 |
|
PNG |
170kB |
1:10 |
GIF will reduce the colors to 1 byte 256 (colors) and compress the image up to 24 times
24Mbit/75kB = 32 FPS (worse case with all bits drawn)
Backlight requirement
Location |
lumen |
lux (lumen/m²) |
100 watt bulb |
1200 |
120 (10m²) |
Living room |
|
100 |
Bright Room |
|
400 |
Daylight cloudy sky |
|
5,000 |
Daylight clear sky |
|
10,000 |
Daylight bright sunlight |
|
20,000 |
Direct Sunlight |
|
110,000 |
Full moon |
|
0.01 |
· lumen = 1-cos α x 2 x π x candela (α = half light angle)
· lux = candela/distance²
LED |
Intensity |
Lumen |
Lux @ 1cm² (LCD chip) |
VLMW322ABBB5K8L |
2850 mcd 120° |
9 |
83 000 |
VLMW322BACA5K8L |
3550 mcd 120° |
11 |
100 000 |
BL-1210SMD-W120 |
7000 mcd 120° |
22 |
220 000 |
· The above calculation doesn’t take into account the light attenuation when reflected through the mirror and the LCD backlight diffusion layer
The mirror solution has a big
disadvantage due to its unattractive appearance and bulky size.
A fresnel lens can be used to reduce the size and make the glasses more
flexible.
The interlaced edges in the fresnel mirror has just a small impact of the
visibility because the
edges are located out of focus and therefore becomes blurred and invisible.
The Fresnel lens consists of two parts, one with a reflective coating surface
and the
other with an inverted shape with same refraction index. This design will
provide a perfect
“see thru” combined with the reflective mirror lens from the unique fresnel
design.
The reflective light from the opposite side comes from an IR light source used
to
light up the iris for the eye camera.
Types of activation
Both eyes blink activation
Both eyes blink for
“press down” same for release.
One eye blink activation
One eye for “press down” the other
for release.
One eye for “press down” same for release.
·
Eye focus-delay
activation
Stare at the same
location for short time activates “press down”.
Stare at the same location for longer time activates “release”.
·
Head nod
activation (g-sensor requirement)
Head nod activates
“press down”.
Head nod the second time activates “release”.
·
Head nod direction
sensitive activation (g-sensor requirement)
Head nod forward
activates “press down”.
Head nod backwards activates “release”.
· Chew activation (g-sensor requirement)
Chew/bite activates “press down”.
Chew/bite the second time activates “release”.
·
Head Switch
activation
Pressed switch activate
“press down” release for “release”.
· Eye gesture activation
Drawing symbols activates different functions/programs.
· Nose poke activation (g-sensor and gyro)
A virtual stylus is moved with the
head and used to activate menus.
(actually only the menu is moved for this illusion)