CA2689701A1

CA2689701A1 - Viewing device for welding helmets, sun visors and the like

Info

Publication number: CA2689701A1
Application number: CA 2689701
Authority: CA
Inventors: Shangqing Liu; Changsong Liu
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-07-10
Filing date: 2009-07-10
Publication date: 2011-01-10

Abstract

The invention provides a viewing device for eye or vision protection when viewing object with harmful optical radiation such as welding arc or in glare background such as driving towards oncoming vehicle at night. The device is mounted in a head worn or attached to a before eye equipment, such as welding helmets or sun visors. The viewing device contains video camera to get wide visual angle, signal remodelling module to darken/brighten too bright/dim pixels on flat display. By seeing clear image of viewing filed on the display to replace seeing harmful or glare object, viewer eyes or vision are protected. Furthermore, using two cameras and two displays to achieve stereoscopic view, using miniaturized displays and magnifying lenses to rationalize the device size. Nowadays the video camera and flat display including miniaturized flat display are popular and not expensive which can make the device have reasonable cost.

Description

Viewing Device for Welding Helmets, Sun Visors and the Like This invention relates to a viewing device for eye or vision protection. More particularly, this invention relates to an optical electronic device containing one or two video camera(s), one or two video signal remodelling module(s), one or two flat panel display(s) or and a pair of magnifying lenses mounted in a head-worn or attached to a before eye equipment, such as welding helmets, sun visors and the like, for eye or vision protection when viewing the object with harmful optical radiation or in glare background.

Background of The Invention It is dangerous or difficult to view the object with harmful optical radiation or in glare background, such as the welding arc for welder or the road ahead for driver facing oncoming car light at night.

A popular device for viewing the object with harmful optical radiation is an auto darkening window assembly mounted in a welding helmet. The window assembly is an electronic optical shutter system containing static infrared and ultraviolet filters that always block the infrared and ultraviolet radiations, an electronic control module and an electrically operated liquid crystal light shutter that changes transmittance for visible light. The liquid crystal shutter darkens/lightens when a voltage is applied.
The voltage is come from the electronic control module that contains photocell(s) or other photo-sensor(s). The control module darkens the liquid crystal shutter when it detects the bright arc light, and lightens the liquid crystal shutter after the arc goes out. Such window assembly needs sensitivity adjustment for darkening/lightening degree.
If the sensitivity adjustment is set too low, the window may not darken when exposed to the arc, especially to the small arc. If the sensitivity is set too high, the window may stay darkened when exposed to bright room lights, sunlight, arc flashes from other welders, etc.

One early design of such device is disclosed in U.S. Pat. No. 4,039,254. After then many improvements have been adopted. For example, the scheme for blocking radiations in infrared and ultraviolet ranges is disclosed in U.S. Pat. No.
5,519,512, the scheme for improving visual angle and response time of the light shutter is disclosed in U.S. Pat. No. 4385806.
Although this kind of device is a progress, it still needs overcoming some shortages.
First, the whole liquid crystal shutter has a same transmittance (shade) value in any moment, that is, the transmittance does not vary at different places on the shutter corresponding with the luminance distribution of the viewing scene. Therefore, when shutter shade is at good dark state, that is, when the arc and a small area around it can be seen safely and clearly, the other sites, including those not far away from the arc, cannot be seen. It is because the luminance of the sites away from the arc is much lower than that of the arc and that of the small area around it. Thus, the viewing field is limited. For a typical auto darkening welding helmet on market, such as Miller Digital Elite Series Helmet (see web site http:"w ANi-,.miller,.velds.com), the viewing field is 6 cm by 9.7 cm.
Considering the normal distance from the welding arc to the welder eye is more than 450 cm, the visual angle corresponding to this viewing field is less than 7.6 by 12.3 . It makes user inconvenient when working.

Second, the liquid crystal shutter and the infrared and ultraviolet filters are made of glass sheets. They are brittle. Since the arc light is incident into the viewer eyes directly through them, there is a dangerous possibility to viewer eyes if one (or more) of these glass sheets cracks.
Third, the arc light intensity is very strong, long time irradiation of strong light will degrade the organic crystal molecules in the liquid crystal shutter and shorten the shutter lifetime.

There is no commercial device for viewing the object in glare background to my knowledge now, such as for automobile driver who faces glare light from oncoming vehicle at night. When the road is not wide like most local roads in the countryside, the vehicle light is such glare that the driver cannot see the road ahead clearly.
Many device designs have been proposed for this purpose. One is disclosed in U.S. Pat. No. 5,305,012. The device mainly comprises a transparent liquid crystal modulator consisting of a plurality of pixels. Each pixel has a controllable light transmittance for selectively reducing the intensity of light propagating from a point in a spatial scene, through the pixel, then towards the driver eye. An attached image detecting and processing module determines which pixels the light transmittance is to be actively controlled in order to reduce the intensity of incident light by a selective amount before they reach the driver eye.
Because the spatial scene including the strong light sources is always moving, and the positions of the driver eyes are not fixed too, to correctly determine the pixels needing to reduce light transmittance by a desired amount in real time is not easy. It becomes more difficult to make such device have compact size, light weight and acceptable cost.

Summary of The Invention An aim of the invention is to provide a viewing device for protecting viewer eyes when he or she views the object with harmful optical radiation, such as the welder, metal grinder, and etc. The device of the invention can overcome the disadvantages of the previous devices, such as the auto darkening welding helmet. By using video camera with mid- or wide-angle lens to increase the device visual angle. By using video signal multiple amplifying and adjusting circuit to remodel video signal from the camera to brighten too dim and darken too bright pixels on the display and produce a clear image of the whole viewing scene. By using magnifying lenses to see miniaturized and near eye display to reduce the device size. By viewing safe image on the display to instead of directly viewing harmful object like the arc, to protect viewer eye.
Furthermore, by using two video cameras and two displays to achieve stereoscopic view to get more space perceptions like object distance. A binocular head-worn device has the potential to achieve stereoscopic view easily.

Another aim of the invention is to provide a viewing device for protecting viewer vision when he or she views the object in glare background, such as for driver towards oncoming vehicle light at night or rising/falling sun at morning or afternoon, and etc.
The device of the invention can overcome the disadvantages of the previous proposals, such as the one disclosed in U.S. Pat. No. 5,305,012. By using video camera with wide-angle lens to increase the device visual angle. By using video signal multiple amplifying and adjusting circuit to remodel video signal from the camera to brighten too dim and darken too bright pixels on the display and produce a clear image of the whole viewing scene. By viewing clear image on the display to instead of directly viewing object in glare background to protect viewer vision. Furthermore, by using magnifying lenses to see miniaturized and near eye display to make the device be mounted on a head-worn equipment. And by using two video cameras and two displays to achieve stereoscopic view to get space perceptions like object distance.

The aforementioned objects and advantages of the invention will be appreciated from the following description and accompanying drawings wherein:

FIG. 1 is a front schematic view of a device mounted in a welding helmet as an embodiment of the viewing device for eye protection according to the invention.
FIG. 2 is a side sectional schematic view, taken generally on the dash line 11-in FIG. 1, of the embodiment shown in FIG. 1. A video camera on top acquires the image. The video signal is remodelled by an electronic module and transmitted to a flat panel display. Then the viewer sees the image through a pair of magnifying lenses.
FIG. 3 is a schematic diagram illustrating the change of an analog video signal of a scanning line after the remodelling by a video voltage signal multiple amplifying and adjusting circuit shown in FIG. 4.
FIG. 4 is a schematic diagram illustrating a video voltage signal multiple amplifying and adjusting circuit as an embodiment of the video signal multiple amplifying and adjusting circuit of the viewing device according to the invention.
FIG. 5 is a schematic diagram illustrating the optical geometry of the magnifying lens as an embodiment of the near eye viewing assembly of the viewing device according to the invention.
FIG. 6 is a front schematic view of a device with stereoscopic view mounted in a welding helmet as another embodiment of the viewing device for eye protection according to the invention.

FIG. 7 is a side sectional schematic view, taken generally on the dash line 181 in FIG. 6, of the embodiment shown in FIG. 6.
FIG. 8 is a rear sectional schematic view, taken generally on the dash line 201 in FIG. 7, of the embodiment of FIG. 6. Two video cameras on top acquire two individual images. The video signals of two images are remodelled by two electronic modules respectively and transmitted to two flat panel displays. Then each of the viewer eyes views a different image through a magnifying lens to achieve stereoscopic view.
FIG. 9 is a front schematic view of a binocular device with stereoscopic view mounted on a headband assemble as an embodiment of the viewing device for vision protection according to the invention.
FIG. 10 is a rear sectional schematic view of the embodiment shown in FIG. 9.
Two video cameras on top acquire two individual images. The video signals of two images are remodelled by two electronic modules respectively and transmitted to two flat panel displays. Then each of the viewer eyes views a different image through a magnifying lens to achieve stereoscopic view.

FIG. 1 I is a side sectional schematic view, taken generally on dash line 221-in FIG. 9, of the embodiment shown in FIG. 9.

FIG. 12 is a front schematic view of a device attachable to sun visor as another embodiment of the viewing device for vision protection according to the invention. A
video camera on left side acquires the image of the road ahead.
FIG. 13 is a rear schematic view of the embodiment shown in FIG. 12. The video signal from the camera is remodelled by video signal remodelling module and transmitted to the flat panel display.

Detailed Description of The Invention FIG. 1 illustrates the front view of a device mounted on a welding helmet. It is used as an embodiment of the viewing device for eye protection according to the invention. The helmet 10 is made of any known helmet materials having suitable durability, strength, lightweight and cost, such as plastic, fibreglass, thermoplastic poly-alloy and etc. A video camera 12 is mounted on the central top of the helmet 10. The location of the video camera may be changed in different designs. The visual axis of the camera is fixed, or changeable manually or electronically. Here the camera visual axis is fixed and parallel with the visual axis of the viewer when he or she comfortably wears the helmet and looks at the front. The knob 13 is for manually adjusting a device function, such as power on and off, the camera visual axis direction, display brightness, image contrast and etc. When more than one functions are manually adjusted, the other adjusting knobs may be mounted behind the knob 13. The descriptions about the adjusting knobs are given in the following with individual embodiments.

The video camera having mid- (> 30 ) or wide- (> 60 ) angle lens and auto-focus function is used to get large visual angle and visual distance range.
Furthermore, the camera lens may have optical or digital zoom function to vary the visual angle. If the zoom lens is used, the zoom ratio is adjusted manually or automatically. There are several choices for the locations of the zoom ratio and other adjusting knobs, which depend on the concrete requirements. It may be on the left outside surface of the helmet as shown in FIG. 1 for convenient use, or on the top area inside the helmet and in front of the head for better reliability (avoiding possible collisions). In order to protect the camera lens from dirtiness and damaging during operations like the arc sparks, a changeable transparent sheet is used to cover the camera lens. Nowadays the video camera with auto-focus function and zoom lens (especially the digital zoom) is very common, such as the popular level snapshot video camera and the simpler ones like webcam. For example, the Microsoft lifeCam NX-6000 webcam can capture high definition video with 1280 x 1024 resolution. It has a visual angle of 71 , 3X digital zoom, and auto-focus function with visual distance range from several centimetres to infinity. Most of the webcams have compact size, light weight and low cost.
FIG. 2 is a schematic side sectional view, taken generally on the dash line 11-in FIG. 1, of the embodiment shown in FIG. 1. The video camera 12 on top acquires the image of the viewing field. The video signal of the image is sent to the electronic remodelling module 14 by wiring 16, and then transmitted to a flat panel display 18 by wiring 20. The viewer views the image through a magnifying lens 22 and another magnifying lens that is behind the lens 22. The camera, remodelling module and the display are powered by battery 25. The headband assembly 24 helps the viewer to wear the helmet comfortably and keep his/her eyes at the right viewing positions.
The welding arcs have very strong optical radiations. For example, the luminance of direct current carbon arcs is 15000 to 90000 stilbs (such as see "Handbook of Optics, vol. I, 2d ed., edited by M. Bass. E. Van Stryland, D. Williams, and W. Wolfe (eds.), McGraw-Hill, New York, 1995, p. 10.23). As comparison, the luminance of a white object in a normal room is just around 0.05 stibs. It means that the maximum difference of the light intensities from a welding scene into the camera is over 6 orders of magnitude. It is over human visual sensation scope. It is lucky that the modern photo-detectors have large dynamic range for detecting such large luminance difference. For example, the silicon pn junction photodiode, which is often used to form CCD
(the image detecting array) of the cameras, can detect light flux over a scope from W/cm2 to 10-3 W/cm2, that is, its dynamic detecting range is over 10 orders of magnitude (such as see "Handbook of Optics, vol. I, 2d ed., edited by M. Bass.
E. Van Stryland, D. Williams, and W. Wolfe (eds.), McGraw-Hill, New York, 1995, p.
15.55).
Therefore the camera having such sensing elements can capture the whole scene including the extremely bright arc and much dimmer objects if adjusting the camera exposure to make the light intensities incident on the sensing array within its dynamic detecting range.
A video camera outputs a one-dimensional stream of analog or digital signal. A
schematic analog video signal for a single horizontal scanning line of a simulate image is shown in FIG. 3. It consists of a voltage signal containing the light intensity information. The voltage peak 26 represents the light intensity of the arc.
The voltage peaks 27, 28 and 29 represent the light intensities of the objects near the arc, and the peaks 30, 31, 32, 33, and 34 represent those of the objects away from the arc, and 35 and 36 represent those of the objects far away from the arc. The highness of the voltage waveform is shown in logarithm scale, and is not drawn in exact real ratio.
The popular displays cannot show such video signal because they don't have so large brightness change ability, especially for the flat panel displays consisting of a plurality of tiny pixels. Of course, the human eyes cannot see such large brightness change too. In order to solve this problem, a video signal remodelling method is introduced here. It is by amplifying weak video signal and depressing strong video signal to shrink the signal change range within the display brightness change scope. To conduct this method, a video signal multiple amplifying and adjusting circuit is designed.
FIG. 4 is a schematic diagram of a video voltage signal multiple amplifying and adjusting circuit as an embodiment of the video signal multiple amplifying and adjusting circuit of the viewing device according to the invention.
In FIG. 4, a transistor 70, the resistors 71, 72, 73, 74, and 75, a capacitor 76, two thyristors 77 and 78, and a diode 79 compose the first video voltage signal amplifier.
With the same structure, the second and the third video voltage signal amplifiers are composed by the transistors 80 and 90, the resistors 81, 82, 83, 84, 85, and 91, 92, 93, 94, 95, the capacitors 86 and 96, the thyristors 87, 88, and 97, 98, and the diodes 89 and 99 respectively.

For a given transistor, by selecting the values of the resistors 71, 72, 73, 74 and 75, the input voltage signal may be amplified linearly by the first amplifier, and then goes into the second amplifier through the diode 79. Afterwards, in the similar way, the voltage signal may be linearly amplified by the second and the third amplifiers, and finally goes to the output terminal 105.
Defining F,, F2 and F3 as the amplifying ratios of the first, second and third amplifier respectively, then if making F, = F2 = F3 = 100, the above voltage multiple amplifying circuit has a total amplifying ratio of 106.
Along with the voltage increase of the signal input the first amplifier, the voltage at the point between the resistors 93 and 94 goes up. By selecting the values of the resistors 93 and 94, the thyristors 97 and 98 may be turned on when the signal voltage at the point between the resistors 91 and 92 is over the F,F2Vi, where the voltage V, is indicated on FIG. 3. Then the voltage at the point between the thyristor 97 and the capacitor 96 falls to almost zero, resulting in no signal output to the terminal 105 from the diode 99. Meanwhile as the thyristor 98 is on, the voltage signal from the diode 89, which voltage is higher than F,F2V,, goes to output terminal 105 directly.

In the same way, along with the further voltage increase of the signal into the first amplifier, the voltage at the point between the resistors 83 and 84 goes up. By selecting the values of the resistors 83 and 84, one may make the thyristors 87 and 88 be turned on when the signal voltage at the point between the resistors 81 and 82 is over the FIV2, the voltage V2 is indicated on FIG. 3. Then the voltage at the point between the thyristor 87 and the capacitor 86 falls to almost zero, resulting in no signal into the third amplifier from the diode 89. Thus, the voltage signal with the voltage higher than FIV2 goes to the output terminal 105 through the thyristor 88. Meanwhile, no signal output from the thyristor 98 any longer.
At last, when the voltage at the point between the resistors 71 and 72 goes up to V3, the thyristors 77 and 78 are turned on (the voltage V3 is indicated on FIG. 3). No signal goes into the second amplifier from the diode 79. Thus, the voltage signal with the voltage higher than V3 goes through the thyristor 78 without any amplifying to the output terminal 105 directly. Meanwhile, no signal output from the thyristor 88 any longer.
The diodes 99, 100, 101 and 102 are used to avoid unwanted influences among three amplifiers. The resistors 103 and 104 form the adjusting circuit, which reduces the voltage of the output signal to match the requirement of the display. The output terminal after voltage adjusting is 106.

The output voltage ranges from diodes 99, 100, 101 and 102 are F1F2F30 -FIF2F3V1, FIF2VI - FIF2V2, FIV2 - FIV3 and V3 - V4 respectively. It means that the signal with voltage between 0 - VI is amplified FIF2F3 times, the signal with voltage between VI - V2 is amplified F1F2 times, the signal with voltage between V2- V3 is amplified FI
times, and the signal with voltage between V3 - V4 is not amplified. Thus, the voltage multiple amplifying circuit selectively amplifies the video signal in different voltage regions with different ratios, that is, the video signal is remodelled.
Choosing V4 = FIV3 = FIF2V2 = FIF2F3V1, where V4 is the maximum voltage of the input signal (also see FIG. 3), thus the range of the input signal voltage (0 - V4) is shrunk to the range of V3 - V4, that is, the change range of the input voltage is shrunk to one millionth at output terminal 105 as F I = F2 = F3 = 100.
Thus at the terminal 105, The peaks 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 and of the input signal waveform become the peaks 46, 47, 48, 49, 50, 51, 52, 53, 54, 55 and 56 of an output signal waveform respectively (see FIG. 3). After such signal remodelling, several peaks of the output signal waveform are distorted, such as the peaks 49, 53, and several new peaks emerge, such as 57, 58 and 59. They may be improved by some measures. For example, making the thyristors 78, 88 and 98 be turned on a little earlier than the thyristors 77, 87 and 97, the distorted peaks may be smoothed somewhat, such as becoming the peaks 60, 61, 62, 63 and 64 respectively. In fact, the distortion of the real output signal will not be as obvious as seen in FIG. 3. The reason is that the widths of the most real signal peaks are much narrower than those shown in FIG. 3. Thus a few distorted peaks, they are just a very small part of the total peaks, cannot cause obvious distortion feeling for a whole image. Another reason is that very few peaks have extremely deep slopes like the peaks 29, 30, 33 and 34, which inducing large distortions.

There are different video signal formats. In almost all of them the video signal is produced, processed, transmitted and displayed on a base of one-dimensional stream of the signal. So the method of using the video signal multiple amplifying and adjusting circuit to remodel the signal intensity can be used for different video formats. For different flat panel displays, the video signals forming the images are either the electric voltage signal or the electric current intensity signal. For the later, the video signal multiple amplifying and adjusting circuit is the video electric current intensity multiple amplifying and adjusting circuit. By using current intensity amplifying or controlling element known at present, and basing the similar remodelling principle disclosed for the embodiment illustrated in FIG. 4, the video electric current intensity multiple amplifying and adjusting circuit can be built.

The above video signal remodelling circuits may be improved further. For example, the fourth, fifth or even more amplifier may be added to the circuit to increase the total amplifying ratio, such as to F1F2F3F4 = 1010, to F1F2F3F4F5 = 1012, or even more, where F4 and F5 are the amplifying ratios of the fourth and fifth amplifiers respectively.
In the another way, the fourth, fifth or even more amplifier may be added to the circuit to reduce the amplifying ratio of each amplifier when keeping the total amplifying ratio same, such as to make F1F2F3F4 = 108 and F1 = F2 = F3 = F4 = 1016, to make = 108 and F 1 = F2 = F3 = F4 = F5 = l 01.33, or even more, resulting in a smaller change range of the output voltage or current intensity to match the brightness change range of the display better. In addition, the operational amplifiers and the like may replace the transistors to get better amplifying performance. The fast transistors may replace the thyristors to get shorter switching time and etc. There are also other measures to improve or construct the remodelling circuit based on the known knowledge.
After video signal remodelling, in order to get better image quality, the image contrast and brightness may be adjusted manually or automatically further. The related contrast and brightness adjusting circuits may be put into the remodelling module, in which the signal remodelling circuit is placed. The knobs for contrast and brightness adjusting are best located near the above said adjusting knob 13. The designs of the contrast and brightness adjusting circuits are well-known knowledge. They are not described in detail here. Then the video signal is transmitted to the flat panel display from the remodelling module.
For a head-worn equipment with a display mounted in it, a problem is that the viewer cannot see the image clearly if the display nears the viewer eyes. The minimum acceptable distance between the display and the eye is 25 cm. Another problem is that if the display is located at an acceptable distance like 25 cm, its size needs to be large to obtain a reasonable visual angle. Both of them create difficulty of making the equipment with a suitable size.
In FIG. 2 a near eye viewing assembly with simple structure is illustrated.
Here only a pair of magnifying lens 22 (another lens is behind the lens 22) is placed in front of the display 18. The distance between two lens centres is from 6.3 cm to 7.7 cm, which corresponds with the normal distance between two eyes of adult (the inter-pupillary distance). The distance between two lenses may be fixed or changeable to fit individual eyes better. In this embodiment it is fixed at 7 cm.
FIG. 5 is a schematic diagram illustrating the optical geometry of the magnifying lens as an embodiment of the near eye viewing assembly of the viewing device according to the invention. A magnifying lens 22 with diameter of 6 cm is used here as an example. Considering a moderate eye clearance, the lens is placed at the position that is 3 cm from the eye 110. The distance from the display 18 to the lens is chosen to be 7 cm, which is acceptable for the helmet size.
According to the thin lens imaging formula 1/S' + 1/S = 1/F, where S' and S
are the distances from the display to the lens and from the lens to the eye respectively, and F

is the lens focal length, then since S' = 7 cm and S = 3 cm, the required focal length of the lens is 2.1 cm. The visual angle of this viewing assembly is 90 .
The resolution of the display may be the existing ones, including 480 X 320, X 480, 720 X 480, 1024 X 768, 1280 x 720, 1280 X 1024 and 1920 X 1080, but not limited to them. The resolution of the display needs matching with the camera.
Considering general requirement for most welding and grinding operations and reducing the device cost, the popular resolutions of 720 X 480 or 1024 X 768 is preferred here.
In order to get better viewing quality and operating performance, the near eye viewing assembly may be improved. Such as using high refractive index materials and/or the diffraction and/or binary optical technologies to reduce the lens thickness, using multi-component type of lens to eliminate lens optical distortion, chromatic dispersion and etc. The lens diameter, the distance from the lens to the eye, and the distance from the display to the lens may be changed, such as from 1 cm to 8 cm, 2 cm to 10 cm and 2 cm to 16 cm respectively. The other kind of optical elements, such as optical prisms, reflective mirrors, diffractive and holographic elements and etc. may also be used to construct different kinds of optical viewing assemblies. The improvements of the near eye viewing assembly may further consult the designs of the head-worn displays, reference is made to the following publications: "Head-worn Displays: The Future Through New Eyes" by J. Rolland and O. Cakmakci, in Optics & Photonics News, published by The Optical Society of America, vol. 20, no. 4, 2009, pp.
21-27, and the Chapter 1, 8, 15 and 16 in "Handbook of Optics, vol. II, 2d ed., edited by M. Bass. E.
Van Stryland, D. Williams, and W. Wolfe (eds.), McGraw-Hill, New York, 1995.
The flat panel display is miniaturized one with diagonal size from 0.5 inch to inches. They may be is liquid crystal display, liquid crystal on silicon display, light-emitting diode display, organic light emitting diode display, electro luminescent display, surface-conduction electron-emitter display, field emission display and etc.
Nowadays, the miniaturized displays are used popular and are not expensive. For example, most snapshot cameras have miniaturized display mounted on the rear back.
FIG. 6 illustrates the front view of a device having stereoscopic view mounted in a welding helmet. It is used as another embodiment of the viewing device for eye protection according to the invention. The helmet 180 is made of the materials same as those described for the embodiment shown in FIG. 1. Two video cameras 182 and are mounted on the top of the helmet. The locations of two video cameras may also be changed in different designs.

The distance between two cameras (lens centre to lens centre) is from 6.3 cm to 7.7 cm. This distance may be fixed or changeable manually. In this embodiment it is fixed and is 7 cm.

The visual axes of two cameras are fixed, or adjustable manually or electronically to get better perspective for stereoscopic imagery. Here the visual axes of two cameras are adjustable. In vertical direction the visual axes of two cameras are parallel with the visual axes of the viewer eyes when he or she comfortably wears the helmet and looks at the front. In horizontal direction the visual axes of two cameras are synchronously adjusted and always meet at a point. The distance from that point to the centre of so-called `Baseline' of the two cameras (a line connecting two camera lens centres) is changeable from 0.35 in to 9 in. Since over 9 in the angle of an object becomes essentially the same from each eye of the viewer (see M. Bass. J. M. Enoch, E.
W. Van Stryland, and W. L. Wolfe (eds.), Handbook of Optics, vol. III, 2d ed., McGraw-Hill, New York, 2001, pp. 12.3 -12.13). The knob 185 for adjusting the visual axes of the cameras is located between two cameras.

Another way to adjust the horizontal directions of the visual axes of two cameras is to horizontally cut each image captured by two cameras to change the percentage of their common area to form a changing binocular overlap. Its advantage is no camera mechanical movements. The description about it will be given in the following.
The knob 186 is for manually adjusting one of the device functions, such as power on and off, the display brightness, the image contrast and etc. When more than one functions are manually adjusted, the other adjusting knobs may be mounted behind the knob 186. The adjusting knobs may also be mounted on other suitable places, such as on the top area inside the helmet and in front of the head.

The video camera having angle lens larger than 40 and auto-focus function is used. The camera lenses may also have zoom function that is adjusted automatically or manually. The knob for zoom ratio adjusting may be located near the above said power, brightness and contrast adjusting knobs.

FIG. 7 is a side sectional schematic view, taken generally on the dash line 181 in FIG. 6, of the embodiment shown in FIG. 6. The video camera 184, electronic remodelling module 188, display 190 and magnifying lens 194 form the imaging and viewing system for viewer left eye, which is powered by the battery 198. Wires 206, 200 and 108 connect the elements of this system. The part 204 is the headband assembly.
The imaging and viewing system for viewer right eye is behind the elements for left eye and cannot be seen.
FIG. 8 is a rear sectional schematic view, taken generally on the dash line 201 in FIG. 7, of the embodiment of FIG. 6. Two video cameras 182 and 184 on top acquire two individual images. The video signals are remodelled by two electronic modules 188 and 189 respectively and transmitted to two flat panel displays 190 and 192, which are illustrated by dash lines as they are sheltered by covering plate and magnifying lenses 194 and 196. Then each of the viewer eyes views a different image through two magnifying lenses respectively to obtain a stereoscopic view. The cameras, electronic modules and displays are powered by the battery that cannot be seen in Fig. 8.
Two modules are connected to two displays by wires 200 and 202 respectively.
The headband assembly 204 helps the viewer to wear the helmet comfortably and keep his/her eyes at the right viewing positions.
In order to get clear view for whole viewing field containing extremely bright spots like the arc, each of two video signals output from the two cameras need to be remodelled respectively by two video signal multiple amplifying and adjusting circuits, which are the same as that described for the embodiment shown in FIG. 1.
Furthermore, in order to get better image quality, the contrast and brightness of the two images need to be adjusted manually or automatically as the same as those described for the embodiment shown in FIG. 1. Then the video signals of two images are transmitted to two flat panel displays by two remodelling modules respectively. The adjusting degree for signal remodelling, lens zoom ratio, image contrast and image brightness must be the same for two individual imaging systems, that is, two cameras, two remodelling modules and two displays must be adjusted synchronously to make the common areas in two images be same.

In order to get stereoscopic imagery, each eye of the viewer needs to see a different image with a common area for both of the eyes. The binocular overlap, how much of the visual field of each eye is common to the other eye, is the basis for the sense of depth and stereo, which allows human to sense which objects are near and which objects are far. Humans have a binocular overlap of about 100 (50 to the left of the nose and 50 to the right). The larger the binocular overlap, the greater the sense of stereo (see M. Bass. J. M. Enoch, E. W. Van Stryland, and W. L. Wolfe (eds.), Handbook of Optics, vol. III, 2d ed., McGraw-Hill, New York, 2001, pp. 12.1 -12.17).
One way to change the binocular overlap is to adjust the horizontal directions of the visual axes of the two cameras. It has been described above for FIG. 6.
Another way is to horizontally cut the area of each image captured by two cameras to change common area percentage in each image electronically. For example, when 80% of the image captured by one camera is common to the image captured by another camera, the viewer stereoscopic sense will be greater than that when only 60% of each image is common to the another. Since the image area cutting can be conducted electronically, it has an advantage of no camera mechanical movements. In order to provide the image with enough large viewing field for cutting, the camera visual angle needs to be sufficient large such as larger than 45 . How to cut the image in horizontal direction electronically is relatively simple. For example, to cut the length of each single horizontal scanning line of output video signals from the remodelling modules.
There are various mature measures for video editing. For example, see "Handbook of Image and Video Processing" by Alan C. Bovik, published by Elsevier Academic Press, 2ed., London, 2005. Considering that the editing requirement for the above cutting is relatively simple (without changes of sharpness, color, saturation and etc.), it will not complicate device and increase cost much.
The structure and design of the near eye viewing assembly of this embodiment are the same as that described for the embodiment shown in FIG. 5. One different is that there are two separated displays located in front of two magnifying lenses.
The distance between two lens centres is from 6.3 cm to 7.7 cm. In this embodiment it is 7 cm.

In order to get better viewing quality and operating performance, the near eye viewing assembly of this embodiment may also be improved by the measures such as those described for the embodiment shown in FIG. 5.
The flat panel displays are miniaturized ones with diagonal size from 0.5 inch to inches. They may be is liquid crystal display, liquid crystal on silicon display, light-emitting diode display, organic light emitting diode display, electro luminescent display, surface-conduction electron-emitter display, field emission display and etc.
FIG. 9 is a front schematic view of a binocular device with stereoscopic view mounted on a headband assembly as an embodiment of the viewing device for vision protection according to the invention.
Two video cameras 220 and 222 on top acquire two individual images of the viewing scene having objects whose luminance difference is over human eye clarifying ability. The video signals of two images are remodelled by two electronic modules 224 and 226 respectively and then transmitted to two flat panel displays located in the holding frame 228. The frame is mounted on the headband assembly 230. The knobs 232, 234, 236 and 238 are located on the front outside surface of the frame 228 for adjusting device functions, such as power on and off, camera lens zoom ratio, image contrast, image brightness and etc. The battery is stored in the Box 239. The knob 241 is for adjusting the visual axes of the cameras.
FIG. 10 is a rear schematic view of the embodiment shown in FIG. 9. Two magnifying lenses 240 and 242 are mounted on the frame rear edge. Two flat panel displays 244 and 246 are illustrated by dash lines as they are sheltered by covering plate and magnifying lenses.
FIG. 11 is a side sectional schematic view, taken generally on the dash line 221 in FIG. 9, of the embodiment shown in FIG. 9. The flat panel display 244 is mounted on the inside surface of the frame 228. The magnifying lens 240 is mounted on the frame rear edge and has a distance 7 cm from the display 244. The display and magnifying lens for viewer right eye are behind the display 244 and the lens 240 and cannot be seen.
Since each eye of the viewer sees a different image, the stereoscopic view can be achieved.

In the electronic and optic aspects, the designs for this embodiment are the same as those for the embodiment shown in FIG. 6. Therefore the detailed descriptions are not repeated here.
This viewing device is for viewing the object in the glare background. There are no harmful infrared, ultraviolet and extremely strong visible radiations, which can hurt viewer skin. Therefore, the viewing device is mounted directly on the headband assembly to reduce device weight and facilitate the use. In order to ensure the security for viewer such as for the driver during driving, some safety functions must be added.
One of them is the warning light to indicate insufficient charge in the battery. In this embodiment, the battery warning light 248 is located beside the display for reliable notice.
FIG. 12 is a front schematic view of a device that is attachable to sun visor as another embodiment of the viewing device for vision protection according to the invention.

On the left side of the frame 260, a video camera 262 is mounted, which captures the image of the viewing scene having objects whose luminance difference is over human eye clarifying ability. The straps 264, 266, 268 and 270 are used to attach the device to the sun visor of the vehicle. The buckles 272 and 274 are used to tighten the straps. The visual axis of the camera is fixed or changeable manually or electronically.
In this embodiment, the visual axis is changeable and is adjusted towards the road ahead when the sun visor is turned down completely. The video camera having angle lens lager than 45 and auto-focus function is used. The camera lens may also have zoom function that is adjusted automatically or manually.
FIG. 13 is a rear schematic view of the embodiment shown in FIG. 12. The video signal from the camera is remodelled by an electronic module, which is located in the frame and cannot be seen, and then is transmitted to the flat panel display 276. The device is powered by a battery that is also located in the frame 260. The device has an external power cable used for battery charging or powering the device directly to save the battery. This cable may be connected to the cigarette lighter hole. The knobs 280, 282, 284, 286 and 290 are for adjusting visual axis of the camera, the lens zoom ratio, the power on and off, display brightness, image contrast and etc. they are located on the right side of the frame 260.
In the electronic and optic aspects, that is, the capturing of the viewing scene, video signal remodelling, image transmitting and displaying are the same as those described for the embodiment shown in Fig. 1, excepting that the display used in this embodiment is not a miniaturized one, and the magnifying lenses are not needed.
The display used here have the same resolutions described for the embodiment shown in Fig. 1. Its diagonal size is from 5 inches to 22 inches. The display may be liquid crystal display, liquid crystal on silicon display, light-emitting diode display, organic light emitting diode display, electro luminescent display, surface-conduction electron-emitter display, field emission display and etc. In addition, the device may be mounted on the sun visor directly, that is, to manufacture a new kind of sun visor, which has the video camera, remodelling module, flat display and related attachments.
At ordinary times, the sun visor with the device attached to it is turned up.
The driver sees the road ahead through the windshield directly. At night when a vehicle is coming, the sun visor with the device is turned down. The video camera captures the viewing scene of the road ahead including glare light from oncoming vehicle.
After the video signal is remodelling and adjusting, the driver may see the clear image of the road ahead on the display for safe driving.
It will be apparent that various changes and modifications can be made without departing from the scope of the invention as defined in the claims. For example, the locations of the cameras, the remodelling modules, the battery and the adjusting knobs may be changed. Some attachments may be added to help tightening the headband assembly to different viewers and etc.

Claims

1. A viewing device mounted in a head-worn equipment for eye protection when viewing object with harmful optical radiation, said viewing device consists essentially of:
video camera, video signal remodelling module, flat panel display, a pair of magnifying lenses and power source;

the video camera captures the viewing scene having objects whose luminance difference is over human visual sensation scope, the video signal remodelling module selectively amplifies the video signal output from the camera in different intensity regions with different ratios and adjusts it to shrink the signal intensity difference to a displayable range for forming clear image of the viewing scene on the flat panel display;

the flat panel display is watched through a pair of magnifying lenses.

2. The viewing device of claim 1, wherein said head-worn equipment is welding helmet and the like.

3. The viewing device of claim 1, wherein said video camera has mid- (>
30°) or wide-(> 60°) angle lens.

4. The viewing device of claim 1, wherein said video camera has optical or digital zoom lens.

5. The viewing device of claim 3 or claim 4, wherein said lens has a changeable transparent covering sheet.

6. The viewing device of claim 1, wherein said video camera has auto-focus function.

7. The viewing device of claim 1, wherein the visual axis of said video camera is fixed or changeable manually or electronically.

8. The viewing device of claim 1, wherein the dynamic range of said video camera for detecting luminance is up to 10 orders of magnitudes.

9. The viewing device of claim 1, wherein said video signal remodelling module contains multiple video signal amplifiers and adjusting circuit, each amplifier amplifies the video signal in a desired intensity region with a desired ratio, to shrink the signal intensity difference to a displayable range to form clear image of the viewing scene on the flat panel display.

10. The viewing device of claim 1, wherein said flat panel display is miniaturized display with diagonal size from 0.5 inches to 5 inches.

11. The viewing device of claim 1, wherein said flat panel display is liquid crystal display, or liquid crystal on silicon display, or light-emitting diode display, or organic light emitting diode display, or electro luminescent display, or surface-conduction electron-emitter display, or field emission display.

12. The viewing device of claim 1, wherein said magnifying lens is placed in front of said flat panel display, the distance between them is from 2 cm to 16 cm.

13. The viewing device of claim 1, wherein the diameter of said magnifying lens is from 1 cm to 8 cm.

14. The viewing device of claim 1, wherein said magnifying lens is a multi-component type of lens.

15. The viewing device of claim 1, wherein said magnifying lens is a diffractive optical type of lens.

16. The viewing device of claim 1, wherein said magnifying lens is a binary optical type of lens.

17. The viewing device of claim 1, wherein said power source is disposable or rechargeable battery.

18. The viewing device of claim 1, wherein said power source is power cable connected to external electrical source.

19. The viewing device of claim 1, wherein two said video cameras, two said video signal remodelling modules and two said flat panel displays compose two separated imaging systems for different eyes of viewer to achieve the stereoscopic view.

20. The viewing device of claim 19, the visual axes of two said cameras are fixed or adjusted manually or electronically.

21. The viewing device of claim 19, the visual axes of two said cameras are adjusted by horizontally cutting the partial area of each image captured by the cameras to form a changing binocular overlap.

22. A viewing device mounted on a head-worn equipment for vision protection when viewing object in glare background, said viewing device consists essentially of:

video camera, video signal remodelling module, flat panel display, a pair of magnifying lenses and power source;

the video camera captures the viewing scene having objects whose luminance difference is over human eye clarifying ability, the video signal remodelling module selectively amplifies the video signal output from the camera in different intensity regions with different ratios and adjusts it to shrink the signal intensity difference to a displayable range for forming clear image of the viewing scene on the flat panel display;

the flat panel display is watched through a pair of magnifying lenses.

23. The viewing device of claim 22, wherein said head-worn equipment is headband assembly and the like.

24. The viewing device of claim 22, wherein said video camera has mid- (>
30°) or wide- (> 60°) angle lens.

25. The viewing device of claim 22, wherein said video camera has optical or digital zoom lens.

26. The viewing device of claim 22, wherein said video camera has auto-focus function.

27. The viewing device of claim 22, wherein the dynamic range of said video camera for detecting luminance is up to 10 orders of magnitudes.

28. The viewing device of claim 22, wherein said video signal remodelling module contains multiple video signal amplifiers and adjusting circuit, each amplifier amplifies the video signal in a desired intensity region with a desired ratio, to shrink the signal intensity difference to a displayable range to form clear image of the viewing scene on the flat panel display.

29. The viewing device of claim 22, wherein said flat panel display is miniaturized display with diagonal size from 0.5 inches to 5 inches.

30. The viewing device of claim 22, wherein said flat panel display is liquid crystal display, or liquid crystal on silicon display, or light-emitting diode display, or organic light emitting diode display, or electro luminescent display, or surface-conduction electron-emitter display, or field emission display.

31. The viewing device of claim 22, wherein said magnifying lens is placed in front of said flat panel display, the distance between them is from 2 cm to 16 cm.

32. The viewing device of claim 22, wherein the diameter of said magnifying lens is from 1 cm to 8 cm.

33. The viewing device of claim 22, wherein said magnifying lens is a multi-component type of lens.

34. The viewing device of claim 22, wherein said magnifying lens is a diffractive optical type of lens.

35. The viewing device of claim 22, wherein said magnifying lens is a binary optical type of lens.

36. The viewing device of claim 22, wherein said power source is disposable or rechargeable battery.

37. The viewing device of claim 22, wherein said power source is power cable connected to external electrical source.

38. The viewing device of claim 22, wherein two said video cameras, two said video signal remodelling modules and two said flat panel displays compose two separated imaging systems for different eyes of viewer to achieve the stereoscopic view.

39. The viewing device of claim 38, the visual axes of two said cameras are fixed or adjusted manually or electronically.

40. The viewing device of claim 38, the visual axes of two said cameras are adjusted by horizontally cutting the partial area of each image captured by the cameras to form a changing binocular overlap.

41. A viewing device mounted on or attached to a before eye equipment for vision protection when viewing object in glare background, said viewing device consists essentially of:

video camera, video signal remodelling module, flat panel display and power source;

the video camera captures the viewing scene having objects whose luminance difference is over human eye clarifying ability, the video signal remodelling module selectively amplifies the video signal output from the camera in different intensity regions with different ratios and adjusts it to shrink the signal intensity difference to a displayable range for forming clear image of the viewing scene on the flat panel display;

42. The viewing device of claim 41, wherein said before eye equipment is sun visor and the like.

43. The viewing device of claim 41, wherein said video camera has mid- (>
30°) or wide- (> 60°) angle lens.

44. The viewing device of claim 41, wherein said video camera has optical or digital zoom lens.

45. The viewing device of claim 41, wherein said video camera has auto-focus function.

46. The viewing device of claim 41, wherein said the dynamic range of said video camera for detecting luminance is up to 10 orders of magnitudes.

47. The viewing device of claim 41, wherein said video signal remodelling module contains multiple video signal amplifiers and adjusting circuit, each amplifier amplifies the video signal in a desired intensity region with a desired ratio, to shrink the signal intensity difference to a displayable range to form clear image of the viewing scene on the flat panel display.

48. The viewing device of claim 41, wherein the diagonal size of said flat panel display is from 5 inches to 22 inches.

49. The viewing device of claim 41, wherein said flat panel display is liquid crystal display, or liquid crystal on silicon display, or light-emitting diode display, or organic light emitting diode display, or electro luminescent display, or surface-conduction electron-emitter display, or field emission display.

50. The viewing device of claim 41, wherein said power source is disposable or rechargeable battery.

51. The viewing device of claim 41, wherein said power source is power cable connected to external electrical source.

52. The viewing device of claim 41, the visual axis of said camera is fixed or adjusted manually or electronically.