GB2445365A

GB2445365A - Anti-dazzle apparatus

Info

Publication number: GB2445365A
Application number: GB0700170A
Authority: GB
Inventors: Michael Robert Garrard
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-01-05
Filing date: 2007-01-05
Publication date: 2008-07-09
Also published as: GB0700170D0

Abstract

An optical device including a transmission medium 101 which has the ability to adjust selectively and dynamically the light attenuation (for example to reduce dazzle or glare). This may be achieved by means of a light detector 200 and a controller 201: High intensity light 102 from a bright object 104 (within the filed of view 105) may be directed to both the observer 100 and the light detector 200; the controller 201 may calculate that area 202 requires maximum attenuation. The invention may be applied to front screens for vehicles, rear view mirrors, sunglasses, welding masks, security and monitoring cameras or other visual systems.

Description

2445365

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AM OPTICAL TRANSMISSION SYSTEM

The present invention relates to an optical system with dynamic and selectively variable light transmission for visual systems.

Background general problem

Sometimes visibility of an observing system is reduced due to a bright source of light directed toward the observing system. This can occur when the source of light is sufficiently bright compared to other items in the field of view that the observing system cannot accommodate the range of brightness. The effect is that the observing system is less able to correctly see the field of view - detail and contrast of the view are reduced.

Background examples

An example might be when driving, visibility can be reduced due to the glare of the sun. Since the problem is caused by the position of the sun relative to the observer and his/her movement, it will be appreciated that this problem is common to any mode of transport, including walking, automobiles such as cars and motorbikes, aircraft and boats.

Background other light sources

Furthermore, it will be appreciated that any source of bright light might serve to cause dazzle, such as a motion triggered security lamp. That dazzle might be caused by more than one light source simultaneously, such as oncoming car headlights at night, or multiple reflections of the sun.

Background non-human observers

In addition, similar problems are encountered by non-human visual systems such as security cameras. For example, a camera sensitive to low levels of luminosity can be unable to read the registration plate of a car due to *dazzle' from the car headlights.

Thus the term ^observer' herein applies not only to human observers but to any observation system to which the invention might be applied.

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General problem

In general, the problem can be stated as one of reduced visibility due to variation in brightness in the field of view greater than can be accommodated by the visual system regarding the view.

Prior art sunglasses

To reduce the glare, people sometimes wear sunglasses. This is effective in reducing the brightness, but reduces the contrast evenly, so visibility is often still poor particularly if the sun is within the field of view. In addition the reduction in brightness is usually fixed for a particular pair of sunglasses so the reduction of light intensity is predetermined and may be too great or too little. This still true of sunglasses that use a fixed but graduated attenuation that is typically darker at the top, because the sun may be low in the sky and still bright.

Prior art photochromatic sunglasses

Some sunglasses use a chemical 'photochromatic' means to self adjust the level of attenuation. This is effective in adjusting to the average level of luminosity but is of no advantage for increasing contrast. In addition such sunglasses are usually slow to react, taking 10's of seconds to darken, which can lead to dazzle if the sun is encountered suddenly, for example turning to face the setting sun; and also taking 10's of seconds to lighten, which can lead to poor visibility when moving from a light to a dark environment, for example driving into a tunnel.

Prior art welding helmets

Electronic welding helmets use an LCD window that darkens when a high intensity of light is detected. This protects the user from the ultraviolet light produced by the welding arc and from reflections. However the window is darkened uniformly to a high extent that reduces visibility greatly on areas not illuminated by the arc.

Prior art electrochrome mirror

Some rear view mirrors in cars use an electronic dimming means called 'electrochrome'. This reduces the intensity uniformly, and so can reduce dazzle but does not increase contrast.

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Accordingly, it is desirable to improve this situation by providing a means to reduce dazzle and improve visibility.

Statement of Invention

An optical system wherein a light transmission medium is varied dynamically versus time and selectively versus direction of observation, in order to attenuate light from the field of view in a way that improves the ability of the observer to observe said field of view.

The Benefits

The outline operation and benefits of the invention will now be described, by way of example, with reference Figure 1.

FIGURE. 1, selectivity and dynamic definition.

FIGURE. 1 illustrates an observer with a field of view including the sun, in which 100 represents the eye of the observer, 101 represents the invention, 102 represent light with a high intensity, 103 represent light with a lower intensity, 104 represents the sun and 105 represents the field of view.

In the invention, the transmission medium 101 is darkened selectively to attenuate significantly the visual path between the observer 100 and the source or sources of bright light 104. Selectively in this context means that attenuation of light through some parts of the medium is greater than light through other parts of the medium. The high intensity light 102 is attenuated by the transmission medium 101 to a lower intensity 103. However, the remainder of the visual field is already at a lower intensity 103. In this area, the transmission medium applies less attenuation, and maybe none at all. This allows the observer 100 to observe the field of view 105, including a source of bright light directed towards the observer, whilst achieving much improved visibility of the remainder of the field of view 105 particularly in close proximity to the bright light. The detail of attenuation pattern required determines the selectivity required of the transmission medium.

Various changes in the system affect the required pattern of attenuation. These include changes in the incident light intensity or pattern, movement of the observer, movement of the transmission medium and/or movement of the bright object. The improved visibility of the observer is maintained during changes by dynamic (sufficiently rapid)

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updates of the attenuation pattern of the transmission medium.

Embodiments

Example embodiments of the invention will now be described, with reference to the drawings, of which:

FIGURE. 2 illustrates a first embodiment of the invention using as an example the windscreen of an automobile;

FIGURE. 3 illustrates a second embodiment of the invention using as an example sunglasses;

FIGURE. 4 shows a flowchart describing one option for a process to operate the machine shown in Figure 3;

FIGURE. 5 illustrates a third embodiment of the invention also using as an example sunglasses;

FIGURE. 6 illustrates a forth embodiment of the invention using as an example the rear view mirror of an automobile.

A first embodiment of the present invention is now described in detail with reference to FIGURE.2.

In Figure 2., an observer 100 has a field of view 105 including a bright object 104. A light detector 200 is connected to a controller 201, and the controller 201 is connected to a transmission medium 101, that medium being capable of dynamically and selectively attenuating light at the command of control signals from controller 201.

In the invention, the light detector 200 is arranged to have approximately the same field of view 105 as the observer 100. From the bright object 104 high intensity light 102 is directed toward the observer 100. High intensity in this context refers to any light intensity that causes reduction in visibility for the observer 100. The high intensity light 102 also reaches the light detector 200. The light detector 200 sends information on the light from the field of view 105 to the controller 201. This information would typically be a digital representation of the light from the field of view, that is, this information would typically be a digital image.

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The controller 201 processes this digital image to determine the parameters of light over the field of view, such as the average brightness, the brightness mapped over the field of view, the hue mapped over the field of view, and the position in the field of view of the source or sources of high intensity light.

The controller 201 then calculates the optimum attenuation to be applied to the transmission medium 101. The optimum attenuation would be one that reduces the intensity of light in the desired wavelengths, such that the observer has improved vision of the field of view.

For example, the controller might calculate the position 202 on the transmission medium 101 that is intersected by a theoretical line between the observer and each source of bright light. This calculation would typically involve correction of the field of view as presented by the camera, to estimate the field of view as observed by the observer; such action being required if the physical location of the light detector 200 differs significantly from the observer 100. Having identified the areas requiring maximum attenuation, the controller might then apply a gradually reducing attenuation as a function of distance away from the points of highest attenuation. The minimum, maximum,

average attenuation and attenuation rate could also be functions of the observed field of view.

The controller 201 then commands the transmission medium 101 to adjust its attenuation selectively over its area.

This process of measurement, analysis and setting of the transmission medium 101 is updated dynamically, such that the attenuation pattern matches and tracks the field of view as observed by the observer.

Construction of the invention uses techniques known to those skilled in the art. The light detector 200 must have selective sensitivity to brightness over the field of view. This would commonly be a digital camera. The controller 201 must be able to translate the information representing the light pattern in the field of view into a control signal for the transmission medium 101. This would commonly be a microcontroller and supporting electronics. The optical transmission medium 101 would commonly be a liquid crystal display.

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A second embodiment of the present invention is now described with reference to FIGURE.3.

This example is a pair of sunglasses. Each lens 101 is a selective and dynamically variable transmission medium, and digital camera or cameras 200 observe the field of view 105. A second digital camera or cameras 300 track the eyes of the observer, in order to determine how best to deploy the light attenuation.

Techniques for tracking eye movement and estimating the view of the observer are well known. In the case of the present invention, the requirement to track eye position is less critical because the aim is not to estimate where the subject is focussing, simply to determine the position of the pupils.

FIGURE. 4 shows a flowchart describing one option for a process to operate the machine shown in Figure 3.

A third embodiment of the present invention is now described with reference to FIGURE.5.

This embodiment is similar to FIGURE. 3, except that the light detector 200 is closely coupled to the transmission medium 101 in order to eliminate the need to track the eyes of the observer. The light detector need only identify sufficient detail of the field of view 105 to enable setting of the transmission medium 101: for example relatively coarse resolution infra-red detection may be sufficient for a pair of sunglasses. The use of a curved detector might be employed to create variation in intensity and thus estimate the relative location of the sun to the observer.

A forth embodiment of the present invention is now described with reference to FIGURE.6.

This example is an automobile rear view mirror. The transmission medium 101 is placed infront of a mirror 500. The diagram shows the reflection of a vehicle 501, at night, whose headlamps are shining, and would be causing dazzle were it not for the selective darkening of the transmission medium 101. The pattern shown is one option of many that would be effective.

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In this example the light detector 200 is shown beneath the mirror, but it might alternatively be positioned elsewhere around the mirror, or even elsewhere on the vehicle. It might also be shared, for example a camera also used for parking assistance. One camera might be used to control the transmission medium of both centre and side mirrors.

Variations in construction

As would be appreciated by a person skilled in the art,

there are significant variations that might be applied to the construction of the invention, whilst adhering to the principles herein.

The light detector 200 might be, for example, simple light detectors and a lensing arrangement as found in passive infra-red detectors. The light detector 200 might be a film sensor that can detect light over a surface. The light detector 200 might be sensitive to brightness only (monochrome) or to chrominance, hue, saturation or other measure of light or combination thereof, or indeed to wavelengths that are not visible to human observers such as infra red or ultra violet. This might be a property of the detector, or achieved by the use of optical filters. There might be only one detector, or a plurality in order to discriminate different wavelengths of light, or a plurality of detectors in order to provide to the controller different perspectives on the field of view. The light detector 200 might be located after the transmission medium 101 or before it relative to the field of view 105, or to the side.

The controller 109 could be any suitable form of processing device. It might be analogue electronics but would most likely be a digital integrated circuit such as a microcontroller, a programmable gate array, a digital signal processor or application specific integrated circuit.

The algorithm used to calculate the appropriate level of attenuation might be a simple linear dependency,

exponential, a polynomial equation of any order, and/or include a time based function. There may be limits on the minimum or maximum attenuation for visibility or safety reasons. Since the controller is preferably programmable, there is little limitation on the mathematical relationship between the light detected and the attenuation applied.

The image might be processed at the resolution of the light detector or using relationships of multiple pixels in the information reported by the detector. The image might be

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processed serially or stored in memory and processed in bulk.

The optical transmission medium 101 could be any electronically controllable selective display technology, including monochrome liquid crystal, colour liquid crystal, polymer, organic polymer or other electrostatic display. Displays as used in Head Up Display units or digital projectors might be used. Electroluminescent or light emitting diode technology might also be used. The display might be transparent by default or might have some degree of natural attenuation, or reflectivity of incident light. The desired qualities might be produced by a plurality of layers with different functions, a plurality of layers with interactive functions or from a single layer with the desired function.

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Claims

1. An optical transmission system, whereby one or more light transmission media are located between an observer and a field of view, at least one of those media being capable of dynamic and selective variation of light transmission which is carried out in response to one or more properties of the light from the field of view.

2. An optical transmission system according to claim 1, further comprising a semi-reflective or reflective surface incorporated into the light path from the field of view to the observer.

3. An optical transmission system according to claim 1 or 2 whereby the adjustment to light transmission is undertaken as a mathematical function, such as a polynomial or logarithmic or mapped, of some measure of the light in the field of view.

4. An optical transmission system according to claim 3 whereby the mathematical function is an inverse relationship whereby the areas of the greatest light intensity in the field of view are most attenuated, with areas of lesser intensity in the field of view receiving less or no attenuation

5. An optical transmission system according to claim 3 whereby the minimum and or maximum degree of attenuation is limited.

6. An optical transmission system according to claim 3 whereby the mathematical function includes compensation for the brightness as perceived by the observer.

7. An optical transmission system according to claim 3 whereby the average attenuation is a function of the brightness of ambient light.

8. An optical transmission system according to claim 1 or 2 whereby the dynamic update rate of the pattern of selective transmission is sufficient to track the relative positions of the observer, and/or the direction of view, and/or the movement of objects within the field of view.

9. An optical transmission system according to claim 1 or 2 whereby one of the properties of light used in the determination of transmission is brightness or intensity.

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10. An optical transmission system according to claim 1 or 2 whereby the property of light that varies when the light passes through the transmission occurs is brightness or intensity.

11. An optical transmission system according to claim 1 or 2 whereby the property of light detected is a band or bands of frequencies, those bands optionally including particular colours and/or infra-red and/or ultraviolet.

12. An optical transmission system according to claim 1 or 2 whereby the variation of light transmission occurs for a band or bands of frequencies, optionally including particular colours and/or infra-red and/or ultraviolet.

13. An optical transmission system according to claim 1 or 2 designed to assist a human observer who is using one or both eyes.

14. An optical transmission system according to claim 1 or 2 designed to assist machine systems, with single or multiple points of observation, including both autonomous systems and those used for remote observation by humans.

15. An optical transmission system according to claim 1 or 2 further comprising an electronic means for selective and dynamic control of the light transmission medium.

16. An optical transmission system according to claim 15 wherein the means of electronic control is a microcontroller, digital signal processor or other large scale integrated silicon device.

17. An optical transmission system according to claim 15 wherein the means of electronic control uses memory to store information for processing from the light detectors.

18. An optical transmission system according to claim 1 or 2 further comprising one or more electronic light detectors each capable of resolving a property of light, such as intensity for a particular set of frequencies, for a plurality of areas within the field of view.

19. An optical transmission system according to claim 18 whereby the light detector or detectors are the same side of the light transmission medium as the observer.

20. An optical transmission system according to claim 18 whereby the light detector or detectors are the opposite side of the light transmission medium as the observer.

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21. An optical transmission system according to claim 18 whereby there are light detectors on both sides of the light transmission medium.

22. An optical transmission system according to claim 18 whereby one or more light detectors face the observer for the purpose of tracking the position of the observer, and/or for the purpose of tracking the pupils or other eye features of the observer.

23. An optical transmission system according to claim 22 whereby the position of the observer and/or the perceived direction of observation of the observer is used as a variable in the determination of the attenuation pattern of the light transmission medium.

24. An optical transmission system according to claim 18 whereby the position of observation of the light detector or detectors is offset from the position of the observer or observers, and this information is used as a variable in the determination of the attenuation pattern of the light transmission medium.

25. An optical transmission system according to claim 18 whereby one or more light detectors supplies information used to control one or more light transmission media.

26. An optical transmission system according to claim 18 whereby the electronic light detector is a digital camera including CMOS and CCD types of camera.

27. An optical transmission system according to claim 18 whereby the light detector is not opaque and is located in the light path between the observer and the field of view, including a detector that is a layer or film within the light transmission media composite.

28. An optical transmission system wherein a microcontroller processes data from a digital camera in order to adjust the pattern of light transmission on a liquid crystal screen situated between an observer and a field of view, for the purpose of improving the ability of the observer to observe said field of view.

29. A method of improving the ability of an observer to observe a field of view by attenuating light from the field of view dynamically versus time and selectively versus direction of observation.

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30. An optical transmission system according to any preceding claim, where the invention is applied to sunglasses, front screens for automobiles such as trucks and cars, motorcycle visors, airplane windows, airplane helmet visors, welding masks, rear vision mirrors, rear vision systems employing cameras, security and monitoring cameras, cameras, video cameras, or other visual systems.