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CONTROL OF LIGHT LEVEL OF VACUUM
This application is a continuation-in-part of U.S. Ser. No. 5 08/442,475, filed May 16,1995, now abandoned, which is a continuation of U.S. Ser. No. 08/250,092, filed May 26, 1994, now abandoned, which is a continuation of U.S. Ser. No. 08/057,439, filed May 4, 1993, now abandoned, which is a continuation of U.S. Ser. No. 07/840,852, filed Feb. 25, 10 1992, now abandoned.
FIELD OF THE INVENTION
This invention relates to a variable intensity light emitting instrumentation system on a vehicle and, more particularly, to an electronic control system for adjusting the intensity of light emitting instrumentation to compensate for electrochromic control features through which the light emitting instrumentation is visible, and to light sensing means
adapted to control and vary the intensity of the light emitting elements of the aforesaid instrumentation system over a range as a function of light levels so that as the light levels vary, the intensity of the light emitting elements will also vary whereby the instrumentation system will remain visible to the vehicle operator but not distracting to the vehicle operator during changing light level conditions.
BACKGROUND OF THE INVENTION
The invention disclosed herein is related to the technology 30 disclosed in U.S. Pat. No. 4,917,477, which is owned by the assignee of the present invention, and the aforesaid U.S. patent is to be considered incorporated herein by reference.
Recent advances in electronic technology, particularly the packaging of modules into smaller spaces, has the automo- 35 bile manufacturers requesting more information type modules to be oriented at various and convenient locations inside the vehicle. It is oftentimes desirable by the automobile manufacturer to have the aforesaid information modules, such as an automatic calibrating compass, clock, tempera- 40 ture and other type modules oriented in locations other than the instrument panel on the dashboard, such as in overhead consoles and the like. Such locations of the information type modules will then provide more space for other modules in either the instrument panel on the dashboard or even in the 45 overhead console. One such location for information type modules is the rearview mirror because it allows for easier viewing of the display without the driver removing his/her eyes from the road. One known unlighted display on an externally mounted rearview mirror is disclosed in U.S. Pat. 50 No. 1,528,082. There, nevertheless, exists problems associated with locating lighted information type modules in a rearview mirror environment. Primarily there would be substantial additional cost to the automobile manufacturer because they would have to run additional wires from the 55 instrument panel on the dashboard to enable the light intensity of the light emitting elements of lighted type information type modules to be controlled so as to render the intensity thereof reduced during nighttime driving, for example, and render them non-distractive to the vehicle 60 driver. Further, if such lighted information type modules are embodied in the rearview mirror environment, the provision of electrochromic layer transmissive attenuation, as described in the aforementioned U.S. Pat. No. 4,917,477, will diminish the light intensity of the light emitting ele- 65 ments during glare conditions. Thus, heretofore, the rearview mirror environment was not deemed to be an appro
priate environment for lighted information type modules, especially in mirror constructions embodying electrochromic layer transmissive attenuation capabilities.
Another factor to be considered in orienting a lighted information type display in a rearview mirror environment is that a vacuum fluorescent lighting element would create a problem in safety, namely, the intensity of the vacuum fluorescent display would be distracting to the driver. That is, the readout value of the lighted information type display must be visible through the electrochromic layer as well as be comprehended by the driver. Yet, the display should not be too bright in order to distract the driver's attention from viewing the road forward and rearward. The amount of distraction will increase during nighttime driving because the ratio of light changing from day to night light condition is approximately one million to one, and the display intensity will be immensely brighter to the driver's eyes during the night condition, especially if there is no compensation for the intensity of the information displayed in the rearview mirror setting.
Accordingly, it is an object of this invention to provide a light sensing control system for controlling the intensity of the light emitting elements of the vehicle instrumentation visible to the vehicle operator over a range as a function of light levels so that as the light levels vary, the intensity of the light emitting elements will also vary whereby the instrumentation will remain visible at all times to the vehicle operator, but not at an intensity that would be considered distracting to the vehicle operator during variable light conditions.
Another object of the invention is to provide an improved electro-optic rearview mirror incorporating improved control circuitry whereby the luminance of a light emitting display embodied in the mirror varies with respect to the light transmittance of the electro-optics.
Another object of the invention is to provide an improved electro-optic rearview mirror incorporating improved control circuitry whereby the luminance of a vacuum fluorescent display embodied in the mirror varies inversely with respect to glare light levels impinging on the mirror.
Another object of the invention is to provide an improved electro-optic rearview mirror incorporating improved control circuitry whereby the luminance of a light emitting display embodied in the mirror varies directly with respect to ambient light levels.
Another object of the invention is to provide an improved electro-optic rearview mirror incorporating improved control circuitry whereby the luminance of a light emitting display embodied in the mirror varies inversely with respect to the levels of glare light impinging on the mirror and whereby the luminance of the display may be modified independently of the glare light levels impinging on the mirror.
It is a further object of this invention to provide an ambient light sensing control for varying the intensity of light emitting elements on instrumentation mounted on a rearview mirror assembly of a vehicle.
It is a further object of this invention to provide a light sensing control, as aforesaid, wherein electrochromic means is mounted in front of the light emitting elements of the vehicle instrumentation system so that the light absorption characteristic of the electrochromic means can effect a varying of the intensity of the light emitting elements visible therethrough to the vehicle operator.
SUMMARY OF THE INVENTION
The objects and purposes of the invention are met by providing, in a vehicle having instrumentation indicative of
the parameters associated with the operation of the vehicle, which instrumentation includes variable intensity light emitting elements so that the instrumentation will be appropriately displayed to the vehicle operator, a light sensing control system for sensing varying light conditions and 5 generating corresponding electrical signals indicative of varying light levels, means for controlling the light intensity of the light emitting elements and responsive to the electrical signals for varying the intensity of the light emitting elements visible to the vehicle operator over a range as a 10 function of the varying light levels so that as the light levels change, the intensity of the light emitting elements will also change whereby the instrumentation will remain visible to the vehicle operator but not at a distracting brightness to the vehicle operator during variable light conditions. Another 15 feature of the invention is the provision of a control for adjusting the intensity of the light emitting elements to compensate for the electrochromic control layer through which the light is visible.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and purposes of the invention will become apparent to persons skilled in this art upon reading the following specification with reference to the accompanying drawings, in which:
FIG. 1 is a highly schematic view of the interior of an automotive vehicle;
FIG. 2 is an enlarged front view of the interior rearview mirror assembly within the automobile; 30
FIG. 3 is a highly schematic sectional view taken generally along the line 3—3 of FIG. 2;
FIG. 4 is a schematic block diagram of an operative system for controlling the intensity of the light emitting elements on a vehicle instrumentation system in response to 35 varying light conditions;
FIG. 5 is a graph depicting the level of light intensity absorption by an electrochromic layer as compared to the wave length of the light signal being absorbed; ^
FIG. 6 is a graph illustrating the relationship of the voltage applied to the electrochromic layer of the mirror construction as glare conditions, viewed by the vehicle driver, increase;
FIG. 7 is a graph depicting the voltage level produced by 45 an ambient light level sensing device;
FIG. 8 is a schematic block diagram of an auxiliary system for controlling the intensity of the light emitting elements of a vehicle instrumentation system;
FIG. 9 is a schematic sectional view of another embodi- 50 ment of the invention; and
FIG. 10 is a schematic block diagram illustration of an alternative design for a mirror transmissivity and display intensity control system of this invention. 55
The automatic electrochromic mirror 10 herein disclosed is of the type disclosed in the aforementioned U.S. Pat. No. 4,917,477, which, as stated above, is to be considered 60 incorporated herein by reference. The mirror 10 includes circuitry generally depicted in FIG. 4 for automatically controlling the reflectance of the mirror to provide maximum rear vision while giving relief to the driver from glare which is caused by headlights from the next following 65 vehicle during night driving. The ambient and glare-causing light levels observed by the driver of the vehicle are moni
tored by a pair of photosensors 11 and 12 (FIG. 4) located in the mirror assembly. The electronic circuit shown in FIG. 4 is provided within the mirror assembly and processes the light level information and serves to properly energize the electrochromic layer when glare relief is required.
Referring to FIG. 3, the mirror 10 includes a reflective layer 14 provided on a rear surface of a mirror glass layer 16. A front cover glass 17 is provided in front of the mirror glass layer 16 and oriented therebetween is an electrochromic layer 18. Reflective glass layer 16 has a trapezoidal prismatic profile as described hereinafter in greater detail. As is explained in detail in the aforementioned U.S. Pat. No. 4,917,477, the electrochromic layer 18 includes a substance 19 having the desired electrochromic properties. Transparent conductive layers 21 and 22 are connected to an electrical circuit at terminal points 23 and 24, respectively.
In the operation of the mirror 10, the light ray 1 enters through the front cover glass 17, the transparent conductive layer 21, the electrochromic layer 18, the transparent conductive layer 22, and the mirror glass layer 16 before being reflected from the reflective layer 14 provided on the mirror glass layer 16. Light in the reflected ray 2 exits by the same general path traversed in the reverse direction. Both the ray 1 and the reflective ray 2 are attenuated in proportion to the degree to which the electrochromic layer 18 is light absorbing. The angle of the prism is preferably great enough to allow the rays 3, 4 and 5, which are reflected from different surfaces of the mirror structure other than the reflective layer 14, to be reflected up toward the roof of the automobile instead of toward the eyes of the driver. Only the ray 2 reaches the driver's eyes. The light ray 1 makes one pass through the attenuating layer 18 before being reflected by the reflective layer 14 as the ray 2. The ray 2 then makes a pass through the attenuating layer 18 before being viewed by the driver. Since the rays 3, 4 and 5 are directed away from the driver, the ray 2 is the only light viewed by the driver. It should be noted that the light in the ray 2 has made two passes through the attenuating electrochromic layer 18.
In this particular embodiment, a surface area 26 of the reflective layer 14 of the mirror 10 is removed so that no reflective capability exists in the aforementioned surface area. Alight-emitting information display module 13 having information displayed on its front face 27 is oriented so that the front face 27 abuts against the surface area 26 whereby the information 28 is visible to the vehicle operator through the glass layer 16, the electrochromic layer 18 and the front cover glass 17. Such an information display module 13 can be an electronic compass of the type referred to in U.S. Pat. No. 4,425,717, where the flux gate sensor is mounted in the mounting system 25 (FIG. 1) for the rearview mirror 10 mounted to the vehicle windshield. The controlling electronics 34 (FIG. 4) for the compass can be any of those disclosed in U.S. Pat. Nos. 4,505,054; 4,546,551; 4,677,381 and 4,953,305. The previously mentioned five patents, all owned by Prince Corporation of Holland, Mich., are to be considered incorporated herein by reference.
Referring to the circuit block diagram of FIG. 4, one or more electrochromic mirrors 10,101 and 102 are used as the inside rearview mirror and the left outside and the right outside mirrors, respectively, of a vehicle. These mirrors are supplied with approximately 1.2 volts to darken them and are short circuited to clear them rapidly. It has been found that the mirrors 10, 101 and 102 clear within about 20 seconds when open circuited. The electrical supply 119 for the mirrors 10,101 and 102 is connected to the conventional 12.8 volt automotive supply which is turned on by the vehicle ignition switch. The supply circuit 119 limits supply
voltage transients and regulates the supply voltage to a portion of the system.
The backward facing sensor circuit 12 senses light rays 107 from the headlamps of the vehicle 106 generating an electrical signal indicative of the glare producing light from 5 the rear.
The forward facing sensor circuit 11 senses the ambient light rays 105 to the front of the vehicle, while the visor 112 shields the sensor from the rays 104 of street lamp 103 which is nearly overhead. The purpose of the forward 10 sensing circuit 11 is to respond to ambient light in much the same way as the driver's eyes respond and to establish the operating threshold of the mirror accordingly.
For ambient light level less than 0.02 foot candles, the actual ambient light level has very little effect on the driver's perception of glare. The minimum light threshold circuit 113 causes the output of the forward facing circuit 11 to approach a constant value for light levels which are less than 0.02 foot candles. A time average of about 25 seconds is
applied to the forward light signal by a long time average circuit 114 to produce a time averaged ambient light reference signal against which the signal from the backward facing sensor circuit 12 is compared. This time average
stabilizes the reference signal and causes it to track the slow „
response of the human eye to changing light levels. A comparator circuit 118 is provided which signals a glare condition when the signal from the backward facing sensor circuit 12 indicates a glare light level which exceeds the reference level established by the time averaged forward 3Q signal.
Several other signals combine to override the glare determination and to hold the mirrors 10, 101 and 102 in the bright condition. First, a day detector circuit 115 compares the forward signal against a fixed threshold equivalent to 35 approximately two foot candles and holds the mirrors in the bright condition when the forward light level exceeds this threshold. Second, a vehicle backup detect circuit 116 monitors the backup light signal, which indicates that the vehicle is in reverse gear, and hold the mirrors in the bright 40 condition to improve visibility when the vehicle is in reverse gear. Third, a power supply over voltage detection circuit 117 is provided which holds the mirrors in the bright condition when the automotive supply voltage exceeds a safe operating range for circuit components. 45
Signals are added together at 121 to command the dim state whenever the glare condition is detected and none of the three inhibiting conditions is present. The mirror supply circuit 124 operates in conjunction with the current limit circuit 122 and voltage limit circuit 125 to supply approxi- 50 mately 1.2 volts to the mirrors 10,101 and 102 to cause them to assume the dim state. The mirrors return spontaneously to their bright states within approximately 20 seconds of the time that the 1.2 volt supply is removed. The mirror shorting circuit 123 short circuits the inputs to the mirrors to speed 55 their return to the bright state.
In operation, it is normal for the command signal from 121 to change frequently between commanding the bright and the dim mirror states. The mirrors respond rapidly enough to the dim command that the driver is normally not 60 bothered by excessive glare. The natural delay of the mirrors in returning to their bright states prevents the annoying and disorienting changes in mirror brightness which is associated with other fast responding mirrors when driven by the simplified control circuit. Furthermore, most other mirrors 65 have short periods of unusability or of high distortion during their transition. For example, most liquid crystal display
mirrors scatter light for about one half second following a transition, while a two position prism mirror is misnamed while traveling from one position to another. In contrast, the electrochromic mirror assumes intermediate reflectance and remains useable during all stages of the transition.
A switch 31 (FIG. 2) is located along the bottom edge of the mirror assembly 10 to allow the operator to choose between an "OFF" position which deactivates the automatic glare control feature of the electrochromic mirror and a mirror position M with automatic glare control. If, in this particular embodiment, the lighted information display module 13 is a compass of the type mentioned above, the compass or other electronic module can be activated via the same switch to the "C/M" position as shown in FIG. 2 while retaining the automatic glare control feature. The information 28 is in the form of plural green light emitting members 29, namely, variable intensity vacuum fluorescent elements which are separately controlled and are organized into a pattern so that when they are appropriately lighted, they display a letter or letters or degrees on a compass indicative of the direction of travel of the vehicle. During night mode, these light emitting elements can have their intensity adjusted over a range to a minimal intensity of, for example, 20% of full brightness to allow the driver's non-distraction of the readout. This, however, creates difficult viewing of the display during glare conditions since the electrochromic layer will be appropriately controlled to absorb light both coming from the headlights of the next following vehicle, but also from the light being emitted by the light emitting elements 29 of the information display 28. This particular problem was overcome by the following design improvements.
Vacuum fluorescent light is transmitted normally through the electrochromic layer and during a maximum glare condition, the electrochromic layer 18 attenuates the light emitted from the vacuum fluorescent display about 7 to 1. This attenuation is minimized because both the vacuum fluorescent display emitted light passes through the absorbing electrochromic layer only one time versus two times for reflected light and the green spectral emission curve for the vacuum fluorescent display peaks at a wave length near the minimum in the visual spectral absorption curve for the electrochromic layer. Even with the reduced attenuation through the electrochromic layer, a problem still exists in that the readability of the display during night glare situations is problematic at best. The combination of the 7 to 1 attenuation and the front cover glass 17 reflection of that light will wash out the readout viewing to the operator. This circumstance makes even the green vacuum fluorescent display difficult to read and, as a result, the adjustable display intensity must compensate for the electrochromic layer attenuation by an amount of the increasing glare caused by the headlights of the next following vehicle. This compensation is in the form of a level intensity control circuit 32 in FIG. 4 which monitors the electrochromic layer voltage and sends a monitored electrochromic layer voltage signal to a display driver 33 to increase the display intensity according to the amount of glare relief that is present. As shown in FIG. 6, the amount that the vacuum fluorescent display intensity increases, from a minimum of 20%, is not to a full 100% brightness level during glare conditions, because that particular level of brightness becomes distracting to the operator. Thus, for example, a 50% level of full brightness was arbitrarily selected as the maximum brightness level for the display intensity.
As shown in FIG. 7, the amplified photocell voltage versus ambient light is displayed, the steps for the vacuum