Low profile optical lighting assembly for use in outside vehicle mirror and method of forming same

An optical lighting assembly for use with a vehicular outside rearview mirror includes a printed circuit board (PCB) having a light source such as a light emitting diode (LED) mounted thereon. An optical device such as a light pipe is positioned adjacent to the LED for propagating light away from the LED. A mirror element includes at least one indicia where light escaping from the light pipe is used to illuminate the indicia.

FIELD OF THE INVENTION

The present invention relates generally to optical displays and more specifically a low profile optical assembly for use in lighting indicia used with an outside vehicle mirror.

BACKGROUND OF THE INVENTION

Outside mirrors having indicia for signaling turns or alerting a driver to vehicles in the driver's blind spot are well known in the art. Side blind zone alert (SBZA) systems often use an icon that appears in the vehicle's side mirror when the system detects a vehicle or other objects in the driver's blind spot. In use, the SBZA enables the vehicle to detect other vehicles located where they may be difficult for the driver to directly see using the outside mirrors.

When the SBZA system detects a vehicle in the adjacent lane, the system will illuminate a symbol or other indicia on the driver's outside rearview mirror. This alerts the driver to a potential collision. Often, when the driver activates the turn signal in the direction of the detected vehicle, the blind spot alert symbol will flash to better draw the attention of the driver. Otherwise, the symbol remains illuminated until the other vehicle has left the blind zone. Prior artFIG. 1A,FIG. 1BandFIG. 1Cillustrate various types of indicia that are often used with the outside rearview mirror.FIG. 1Aillustrates a mirror assembly100A that uses a triangular symbol103A positioned at a side edge of mirror101A. The triangular indicia103A is commonly used with the SBZA for indicating a detected vehicle in the vehicle's blind spot zone.

Similarly,FIG. 1Billustrates a mirror assembly100B that shows vehicle indicia103B that depicts two offset vehicles such that one vehicle is to the left and behind the driver's vehicle in the blind spot zone. The vehicle indicia103B is also positioned on a side of the mirror101B and is also used in connection with an SBZA. Finally,FIG. 1Cis another mirror assembly100C that is used as a turn signal indicator such as the chevron103C that is positioned at an edge of the mirror101C. When used in this type of application, the chevron103C would be used with the driver's outside mirror showing the indicia depicting a turn to the left while blinking or illuminated. These indicia or other symbols are most often cut or etched into the mirror glass however indicia formed using microdots and associated applica are also possible. When activated, light projected behind the mirror element will illuminate the symbol or indicia such that it is visible for altering the driver.

Various lighting packages have been developed in order to provide illumination to the indicia behind the mirror glass. The illumination allows the indicia to be easily detected by the driver in both daylight and darkness. Since the outside mirror housing must be limited to a certain size, the optics for lighting the symbols and other indicia become very important since they must radiate a bright light while still remaining a relatively small size in order to fit within a predefined space.

FIG. 2is a prior art cross-sectional diagram showing a lighting technique as used in the prior art. The optical module200includes a printed circuit board (PCB)201having a light emitting diode203mounted on one side of the PCB. An optical device205is positioned in front of the LED203and is used for gathering and directing light rays at a specific angle towards the indicia. This allows the indicia to be visible to the user. In order to protect the optics within the optical module, a cover209is used to surround the back portion of the module.

The optic device205comprises a first lens surface having a total internal reflector (TIR) portion surrounding a refractive portion and a macro beam shaping device. Rather than incorporating lenses into the design, TIR optical materials are used for obtaining a desired illumination pattern from the LEDs or other illumination devices. TIR optical material is advantageous since it can be manufactured of plastic of a reduced size and weight. Moreover, the TIR material can encompass an entire light source for reducing and/or eliminating optical loss that would occur with an optical lens. As seen inFIG. 2, the TIR optic205uses surfaces of revolution based on free-form curves such as a light collection cup207. The TIR optic205also uses other optical principles such cubic splines or Bézier curves that operate to steer and/or direct light in a desired direction.

Those skilled in the art will recognize that other embodiments may use an eccentric reflector to reflect the maximum amount of light from the light source toward the indicia. An eccentric reflector is a reflector that reflects light at a point which is not at a focal point of the reflector optic. However, a disadvantage of these types of lighting assemblies is that the use of eccentric reflectors and other optical devices increase the overall thickness of the lighting module. Although thin profile designs can be achieved using both LED backlighting techniques and eccentric reflectors, current design parameters often require a depth or thickness less than 9 mm. Accordingly, designs using an eccentric reflector can be limited to applications where these types of design constraints are not an issue and the mirror can accommodate the large size of this type of lighting assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 3is an exploded view of an outside vehicular mirror assembly showing the various elements that are positioned within a mirror housing. The mirror assembly300includes a reflective mirror element301that may be manufactured of mirrored glass having a fixed reflectance or alternatively an electrochromic (EC) element for varying the reflectance of the mirror. Positioned behind the mirror element301is a heating element303used for melting ice and/or evaporating condensation or other fluids from the front surface of the mirror element301. A carrier plate305is positioned behind the heating element303and is used for holding the mirror301and heater303into a rigid and fixed position within a mirror housing. As will be described in further detail herein, a lighting module307is used for providing the lighting for illuminating various indicia302cut and/or etched into a surface of the mirror element301. The indicia are used typically for driver assist functions of the vehicle including but not limited to turn signals, blind spot detection, obstacle detection, lane departure warning (LDW) or the like.

The lighting module307fits within a walled holder309that is formed within the carrier assembly305. The holder309is used for holding the lighting module307into a fixed position. In use, the light module307is oriented so as to allow light rays to propagate in forward direction through an aperture311in the heating element303. The light is then projected through the indicia302allowing the etched glass to have a brightly illuminated glow for viewing by the driver. The illumination is of the nature to draw the driver's attention to the indicia when a fully lit of blinking state. The lighting module307is powered using a wiring harness313and electrical connector315at vehicle voltages of 12 VDC or less. The electrical connecter315can be used with carrier recess317for holding the electrical connector315into a fixed position.

FIG. 4is an exploded view of an embodiment of the lighting module shown inFIG. 3. The light module400includes an optical device401such as lens optic. As described herein, the lens optic contains a first lens surface having a total internal reflector (TIR) portion surrounding a refractive portion. The lens optic also includes a macro beam shaping device configured to obtain both a desired illumination pattern and indicia luminance from the illumination devices positioned behind the optic. The lens optic401has one or more surfaces of revolution403for directing the light in a predetermined pattern and/or direction. A printed circuit (PC) board405is positioned behind the optical device and includes one or more illumination devices407such as LEDs or the like. The LEDs may be clear, colored, multi-colored and/or mixed in various combinations of color to illuminate the indicia to a published standard or achieve some desired illumination effect.

The illumination devices such as LEDs407are mounted on the surface of the PC board opposite that which projects toward the optical device401. By having the LEDs backmouted on the PC board405, the LEDS are inset in the PC board405in order to save overall space. This configuration reduces the overall thickness of the PCB assembly, i.e., the thickness of the PCB and the components mounted thereto rather than the LED mounted on one side of the PCB with no through hole. Thus, the overall width or profile of the PC board405and the illumination device407is thinner than if the illumination device407were mounted on the front surface of the PC board405(e.g. the surface facing the optical device401). The LEDs may be mounted in a predetermined shape or pattern on the PC board405in order to align one or more of the LEDs with an optical device401for providing the maximum amount of light at specific locations to the optical device401. In order to achieve the desired illumination of the indicia, an LED may be axially aligned with the optical device401or offset in a manner so as only the desired amount of light is propagated to the optical device. Although illustrated as one type of optical device401, it will be evident to those skilled in the art, various types of optics can be used in order to achieve a desired effect. The light module400further includes a cover409for preventing dirt or other debris from contacting the illumination devices407or the optical device401. The cover409has a predetermined shape and attachment mechanism so as to fit within the walled holder or other predetermined area of the carrier plate as seen inFIG. 5.

FIG. 5illustrates a front view of the carrier assembly as seen inFIG. 3. The carrier assembly500includes the lighting module501shown mounted in the holder503. The wiring harness505is shown extending along the lower edge of the carrier plate507. The electrical connector509may mate to a corresponding receptacle in the carrier assembly500for providing power to the lighting module501. The carrier assembly as described herein can be used for various types of light modules such as the thru-board and edge lighting embodiments as described herein.

FIG. 6is a side cross-sectional view of the thru-board lighting module shown through section lines VI-VI ofFIG. 5according to an embodiment of the invention. The light module600is arranged to include one or more illumination devices601mounted (e.g. LEDs) to the rear side of the PCB603. Although a design incorporating five (5) LEDs is illustrated inFIG. 4, it will be evident to those skilled in the art that other designs greater than or less than five LEDs are also possible for providing desired amounts of light unique to a specific application. Alternatively, other styles of LEDs that are smaller can also be used to provide a desired amount of light needed for this lighting application.

The PCB603defines a gap, aperture or hole allowing light from the LED to project in a forward direction into and through the hole. As described herein, the light from the LED601is collected by an optical device605such as a TIR optic or the like for obtaining a desired illumination pattern from the LED601. The optical device605is positioned such that it touches or abuts a portion of a rear surface of the heating element607. The mirror glass609is then positioned upon a front surface of the heating element607. This allows light from the optical device605to propagate through an aperture610of the heater607toward the mirror glass609. This light is then used to illuminate indicia providing driver assist functionality which are cut or etched into the mirror glass609. An edge of the carrier substrate611can frictionally engage an adhesive with both the heater607and the mirror glass609for holding the assembly into a fixed position within the housing.

As described herein, a cover613is used to prevent dust and other debris from entering the light module that might taint the color of light or lessen the light intensity that would be available to illuminate the indicia at the mirror glass609. As can be seen by comparingFIG. 2andFIG. 6, the PCB603and components connected thereto (e.g. illumination device601) ofFIG. 6can be thinner having a lesser profile then the PCB201and the LED203of prior artFIG. 2. This is based up on the illumination device601being inset to the PCB603and electrically connected to the backside of the PCB603rather than a front side of the PCB. A projection614or spacer is shown inFIG. 6extending from the cover portion613to the PCB603.

FIG. 7illustrates an exploded view of an edge-lit light module assembly in accordance with an alternative embodiment of the invention. The light module assembly700includes a printed circuit board701having one or more illumination devices703(e.g. LEDs) mounted thereon for providing a light source. An optical enhanced specular reflector (ESR) film705is positioned adjacent to the LEDs703for guiding light from the LEDs703into an optical device707. As described herein, optical device707is a light guide, light pipe or the like and is used for propagating light to various locations from the illumination devices703. An optical diffuser709is positioned adjacent to and in front of the optical device707. The optical diffuser709works to spread or scatter the light in a forward direction toward the mirror glass. It should be evident to those skilled in the art that many different varieties of diffusers might be used for this application including but not limited to ground glass diffusers, Teflon diffusers, holographic diffusers, polymer diffusers opal glass diffusers and greyed glass diffusers. Finally, an optical brightness enhancement film (BEF) is used in front of the diffuser707. The BEF operates to direct all of the light rays in a single forward direction for effectively increasing the brightness of the light module assembly700as light is projected toward the indicia. An additional BEF film orientated 90 degrees to the first film can optionally be used to further enhance the intensity. Finally as noted herein, a cover713is used at the rear of the edge-lit light module700for preventing dust and other debris from entering the assembly and affecting operation of the optics.

FIG. 8is a cross-sectional view of the edge lighting module assembly taken through lines VIII-VIII ofFIG. 5. The edge lit light module800includes an illumination device801such as one or more LEDs used to form a light source. The light illumination device801is mounted to a PCB803such that the LED801extends outwardly to abut one side edge of an optical device805. The optical device805may be a light tube, light pipe, light guide, fiber optic or the like that includes a textured surface for allowing light from the LED801to propagate over some predetermined distance using only a single light source. For this edge-lit application, the optical device805is a light pipe having a textured surface for diffusing light where the light pipe is formed using a planar element such as transparent plate for distributing light over its entire length. In this lighting application, it is desirous to select a light pipe for the controlled leakage of light allowing the light to propagate in the optical device. The illumination device801as used in combination with the light pipe805provides a substantially low profile since the light source generally is positioned adjacent the optical device805such that the overall depth of both of these elements can be kept to less than 9 mm. According to one embodiment, the overall depth can be in a range between approximately 4 mm and 8 mm. This offers a distinct advantage over prior art designs since the edge light module assembly can be used in situations where limited space is available for the lighting source.

In use, the light escaping optical device805will be reflected by reflective surface806which could be but is not limited to a white reflective plastic, a metalized plastic or an optical ESR film. The reflective surface806allows an optimal amount of light to be reflected in a forward direction so as it passes through an optical diffuser807. As described herein, the diffuser spreads the light rays so as they are directed through an optional BEF film in one direction for enhancing the overall brightness of the edge lit module800. Those skilled in the art will also recognize that a second BFF film may also be used for directing light in a different plane. The light then passes through an aperture811formed within the heater element812. The light escaping through the aperture811can then be used for illuminating one or more indicia that is etched into the mirror glass813. As described herein, the carrier plate815is used for holding the heater812and mirror glass element813into a fixed positioned while mounted in the mirror housing. A cover817works to cover the back of the light module800for preventing dust or other debris from entering the assembly that might adversely affect optical performance.

FIG. 9A,FIG. 9BandFIG. 9Care diagrams showing illuminated indicia and/or icons used in connection with the mirror glass that can indicate various vehicle functions and driver assist options according to various embodiments of the present invention.FIG. 9Aillustrates an outside mirror900ahaving a mirrored element901ashowing an icon that is used for indicating activation and/or annunciation of various driver assist features. A single icon or indicia may be shaped as a triangle903A, star905B or both may be used. Similarly,FIG. 9Billustrates an outside mirror900B having a mirror901B where a blind spot detector903B, in the form of an automotive icon, is used for notifying the driver of activation of a blind spot detector for indicating e.g. the presence of a vehicle of other object in the driver's blind spot. A secondary enunciator905B is used for indicating to the driver that some predetermined driver assist function may have failed a self-test mode or is having some other type of functional difficulty to alert the driver the device should not be relied upon due to malfunction.FIG. 9Cis an outside mirror900C having a mirrored element901C showing both a turn signal903C along with an annunciation bar905C at the top portion of the mirror element901C for indicating activation of a driver assist function.

Hence, one or more embodiments of the present invention are directed to an optical light module for illuminating symbols or other indicia etched into the reflective glass in an outside vehicular mirror. In one embodiment a thru-board light module is described where one or more light illumination devices such as LEDs are mounted on a rear surface of a PCB. The LEDs propagate light through an aperture located in the PCB where the light is directed to at least one TIR optic. This light is directed through an aperture in the heating element where it is then used to illuminate symbols, letters, numbers and/or other indicia etched into the mirror glass. Similarly, another embodiment of the invention uses an edge lit light technique where one or more illumination devices such as LEDs are positioned adjacent to an edge of an optical light pipe or the like. Light then propagates through the light pipe where it is reflected or refracted in a forward direction. The light then passes through an optical diffuser and an optical BEF. Once the light passes though an aperture in the heating element, it can be used to illuminate symbols or other indicia etched into the mirror glass. The invention is advantageous in that it can be manufactured at low cost and with a profile of less than 10 mm for mounting into small cavities inside an outside mirror housing.