Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Reexamination Certificate
1999-10-12
2001-05-08
Manuel, George (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
Reexamination Certificate
active
06227667
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an apparatus which makes it possible to record the back scatter of the exterior image projected onto the retina of the human eye. The backscatter or retina reflex image is modified or enhanced by additional information by an electronic image processing to form an enhanced image which is projected back into the eye with the aid of a laser beam modulation and deflection for superimposing on the original exterior image.
BACKGROUND INFORMATION
The technical requirements that must be met by the recording, processing and reproduction of images keep growing with an increasing demand for information and their clear graphic visualization. The rapid advance in these fields goes hand-in-hand with the ever accelerating image processing by computers.
Today, the main field where electronic image processing is applied, involves the further processing of images that are taken by cameras, scanning systems and sensors in the visible light spectrum as well as in other sections of the electromagnetic spectrum such as the infrared, the radio frequency and the X-ray frequency range. After electronic processing, the images are reproduced either as individual images or as moving images on an image reproduction screen such as a display for presenting the information to the eye.
On the one hand it is possible to make special image contents easier recognizable by electronic image processing. Known techniques for this purpose include, for example local frequency filtering, margin sharpness increasing, image data compression, image correlation, dynamic reductions and false color coding. On the other hand, other techniques are concerned with the superposition or subtraction of auxiliary images taken from different spectral ranges or with the superimposing of stored plans, maps, and drawings onto the original image.
For many applications an image presentation practically free of time lag is of great advantage to the eye, for example when operating an aircraft, ship, vehicle, or in an open loop control and monitoring of processes and assembly lines. By applying image processing the information content of the actual, direct image can be intentionally increased or reduced. Image processing is used in a wide range from increasing the image contrast to blending-in of additional information, marking of details, and highlighting dangers.
In many of these applications, it is disadvantageous that the electronic camera is a “second eye system” separate from the human eye. This disadvantage is due to the fact that the images are seen from another recording location and that additionally, the pictures on the image screen are presented at another observation location than the eye. Thus, the human eye must constantly change between the direct observation and the indirect observation while taking into account different observation angles, different image details, and different size ratios which leads to physical impairments and delays when decisions must be made.
The above problems have in part been solved by the “head-up-display (HUD)” technique used in the piloting of combat aircraft, in that important informations such as instrument displays and target data are inserted or fade-in into the open spectacles of the pilot's helmet and thus into the visual field of the pilot. This technique is also used experimentally in the automobile industry for displaying of instrument readings on the windshield so that the driver is not distracted from viewing the road by viewing the instrument panel.
The HUD technique has been further developed in the so-called “virtual reality” or “cyber space” technique, wherein closed spectacles are used, i.e. glasses in which the outside view is blocked, and three-dimensional full images moved by the HUD, are projected into the eye with virtual reality. These virtual reality images are then modified in response to body motions such as locomotion, movement of an arm, a finger, or head and eye movements.
The HUD technique generates an image on an image screen and projects the image into the eye after reflection on the surface of the spectacle glasses. The eye sees, so to speak, through the glasses as full mirrors onto the display “around the corner”. Where open spectacles are used, a partially transmitting mirror permits the simultaneous viewing of the outside environment. Since the display is connected to the head, the image follows the head movements.
Certain HUD devices are equipped with an “eye tracker” which follows the eye movements with the help of a motion sensor applied to the eyeball or with a camera which observes the movements of the eye pupils or of the vascular structure of the retina. It is thus possible to electronically shift the image projected in the HUD device, corresponding to the these movements within the visual field.
It is possible in a HUD device to project the image through the projection optic into “infinity” in order to relax the eye free of accommodation. By adjusting different view angles for both eyes toward the same object, a stereoscopic, i.e. three-dimensional vision, is possible.
On the one hand these applications and techniques illustrate the high level of the electronic image processing which is capable to process moving images with an acceptable quality almost without time lag and with a reasonable technical effort and expense. On the other hand, these techniques also illustrate the increasing demand for a direct image transmission into the eye.
However, there are limits to current HUD techniques. The accuracy or precision of the automatic tracking of the eye movements with the eye tracker is substantially worse than the alignment precision and image resolution of the eye. As a result, the fade-in image floats or dances in the visual field which leads to an unprecise target acquisition and is tiring to the eyes.
For the above reasons, conventional applications of the full image reproduction are limited to the use of closed spectacles, i.e. to the exclusive fade-in of external images. Contrary thereto, when open spectacles are used, permitting an additional external view, the fade-in is still limited to simple additional information in the form of text, symbols, or image contours.
A complete three-dimensional and timely overlap between fade-in images and the real image seen by the eye requires an exact three-dimensional and timely coincidence of the two images on the retina. It is the aim of the invention to achieve this coincidence by a direct recording or photographing of the retina image and then projecting the new image back onto the real image substantially without any time lag and with congruence.
First, the prior art will be discussed as far as it relates to the recording of retina reflex images, to image scanning in the internal eye and the projection of laser images directly into the eye. The invention starts from this prior art.
The technical realization of a continuous imaging of the retina reflex of the environment or exterior requires that the optical reflex of the retina is actually usable. The reflection capability of the retina has been measured in detail, for example by F. C. Delori and K. P. Pflibsen in an article entitled “Spectral Reflectance of the Human Ocular Fundus” which appeared in “Applied Optics”, Vol. 28, No. 6, 1989. The reflection capability of the fovea centralis of the retina has a low value of 0.2% at the blue visual spectral range (450 nm) and increases monotonously to a value of 10% at the long wave red range (750 nm). In the range of the largest eye sensitivity and the most acute vision, namely in the green/yellow range between 500 nm and 600 nm the reflection capability is within 1 and 2%.
Thus, a recording system for this reflection capability must be constructed for an illumination density of the retina that is smaller by a factor of 50 to 100 compared to the illumination density of the objects seen by the eye. A further impairment of the available light quantity is due to the size of the eye pupil of 1 to 7 mm, which is, compared to conventional technical recording sys
Eberl Heinrich
Halldorsson Thorsteinn
Schmidt-Bischoffshausen Horst
Daimler-Chrysler AG
Fasse W. F.
Fasse W. G.
Manuel George
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