The present invention is directed generally to lighting systems. More particularly, the present invention is directed to light transforming devices that provide a precisely determined light distribution pattern, such as those used for navigation, obstructions and other signal lights.
Presently, lighting systems are used to mark obstructions and curves on roadways and paths on airport taxiways and runways. For example, airports incorporate a system of lighting to provide guidance to approaching and taxiing aircraft. Thousands of halogen lamps can be used in airports. Unfortunately, these lamps require excessive amounts of power.
In roadway lighting systems, lamps are placed around the obstructions and along roadway curves to signal the presence of the obstructions and curves to drivers. These lighting systems do not sufficiently redirect light in an optimal pattern for drivers. For example, the lamps do not provide adequate light to drivers located far away from the lamps. Accordingly, the lamps also do not compensate for an inverse square relationship of illuminance to distance as a driver approaches the lamp. In particular, the lamps do not adjust for the fact that a driver can see the lamp better when the driver is closer to the lamp. Additionally, most of such signal devices direct only a portion of light emitted by a light source in a useful pattern. Accordingly, they have low efficiency. Some in the prior art have sought to allow “hands-free” access to a user's voice mail messaging system. By way of example, without intending to limit the present invention, U.S. Pat. No. 6,868,142, issued on Mar. 15, 2005 to Gupta et al., discloses a voice-operated interface for communicating with a voice mail messaging system. A speech recognition unit is utilized to retrieve certain voice commands (e.g., “next”, “skip”, “repeat”) and then translate the commands into a proper tone sequence which is transmitted to the voice mail messaging system. The voice mail messaging system then retrieves and transmits the voice mail to the user.
The present invention provides a method and apparatus for a high efficiency redirected light emitted by a light source in a predetermined pattern by using an optical transformer with a precisely calculated reflective surface. In one embodiment, the present invention provides emitted light redirected by a light transformer having a curved circular reflective interior surface, the reflective interior surface reflecting the light in a predetermined pattern. For example, the reflective interior surface reflects the light with a substantial amount of light being reflected close to an axis coincident with a radial line defining a radius of the circular reflective interior surface. The light is transmitted to the exterior of the light transformer by an optical window.
In another embodiment, the present invention provides a light redirecting device for transmitting light with low divergence or substantially parallel with an axis of light direction. The device can include a first total internal reflection surface, a first member including a portion of the first total internal reflection surface, a first planar optical window located at an end of the first member, the first planar optical window being substantially perpendicular to the axis of light direction, and an aspheric lens adjacent to the first member. The device can further include a second total internal reflection surface symmetrical across the axis of light direction with the first total internal reflection surface, and a second member including a portion of the second total internal reflection surface, the second member symmetrical across the axis of light direction with the first member. The device can additionally include a second planar optical window located at an end of the second member, the second planar optical window being substantially perpendicular to the axis of light direction, the second planar optical window further being symmetrical across the axis of light direction with the first planar optical window.
In another embodiment, the present invention provides a light redirecting device that can include a first end that receives light from a light source, a second end that outputs the received light, the second end located on an opposite end of the device from the first end, a first member located on a third end of the light redirecting device the first member having an outer wall comprising a total internal reflection surface, a second member located on a fourth end of the light redirecting device, the fourth end located on an opposite end of the redirecting device from the third end, the second member having an outer wall comprising a total internal reflection surface, and an axis located between the third end and the fourth end, the axis being perpendicular to the first end. The first face and the second face can redirect the received light in a direction of the second end.
In another embodiment, the present invention provides a method for designing a reflective surface for a light transformer that can include the steps of receiving maximum and minimum output angles, receiving a location of a portion of the light transformer with respect to a light source that provides light, and iteratively, point-by-point, calculating an optical transformer reflective surface by providing for each increment of an input angle, an associated increment of the output angle which is consistent with predetermined output intensity distribution to reflect light provided by the light source according to the received maximum and minimum output angles based on the received location of a portion of the light transformer.
In another embodiment, the present invention provides an apparatus for transforming and emitting light that can include a light source that emits light, a light transformer having a curved circular reflective interior surface, the reflective interior surface reflecting the light emitted by the light source in a predetermined pattern with a substantial amount of light being reflected close to an axis coincident with a radial line defining a radius of the circular reflective interior surface and an optical window the transmits the light to the exterior of the light transformer. The reflective interior surface can reflect the light at an angle α to achieve an intensity proportional to 1/(tan2α). The reflective interior surface can further reflects light rays of the light at different angles to compensate for an inverse proportional relationship between perceived intensity and distance from a light source.
The preferred embodiments of the present invention will be described with reference to the following figures, wherein like numerals designate like elements, and wherein:
a)-11(c) are exemplary illustrations of inverse square law compensation using source luminous intensity;
a)-14(c) are exemplary illustrations of a system that provides an omnidirectional light pattern in a horizontal plane with precision predetermined luminous intensity distribution in a vertical plane;
a) and 15(b) are exemplary illustrations of a resulting envelope and a overlapping intensity distribution pattern of a lighting system;
In operation, the light source 310 emits light rays 350-352 towards the reflective surface 130. The light rays 350-352 are reflected in accordance with the curvature of the reflective surface 130. A ray with a minimal angle with respect to the vertical axis is reflected in a direction of the maximum elevation (ray 352), and a ray with a maximum angle is reflected in a direction of minimum elevation (ray 350). Therefore, the waist of the outgoing beam will be formed in order to minimize the vertical size of the transmissive wall. Preferably, a higher percentage of the light rays 350-352 are reflected along the path of ray 350.
For example, 70% of the light emitted from the light source 310 can be reflected substantially along the path of light ray 350, 10% substantially along the path of light ray 352 and the remaining 20% substantially between paths 350 and 352. Therefore, the luminaire 300 will have a luminous intensity higher at lower angles, and about all light emitted by the light source will be directed in a predetermined pattern. In particular, the luminaire 300 can redirect the light so that illuminance at a long range distance (i.e. at the lower observation angles) will be equal to illuminance at a short range distance (i.e. at the higher observation angles). Therefore, as a driver in a car approaches the luminaire 300, the driver can perceive light of equal intensity at long distances and at short distances from the luminaire 300.
In operation, the input device 920 is used to input data to the design processing unit 910. The data may be input by a user of the system 900. The design processing unit 910 can process the data and store the data on the database 940. The design processing unit 910 can also retrieve data from the database 940 for processing. The design processing unit 910 can further send data to the output device 930. The output device 930 may print out or display the data to a user. The output device 930 may additionally machine a light transformer based on the data.
In an exemplary embodiment, the controller 1050 operates in accordance with the invention by receiving maximum and minimum output angles and receiving a location of a portion of the light transformer with respect to a light source. The controller 1050 can iteratively calculate points on the light transformer to reflect light provided by the light source according to the received maximum and minimum output angles based on the received location of a portion of the light transformer.
The design module 1000 can be used to create an arbitrary aspherical reflective surface, for example, reflective surfaces 130, 630 or 635 that will provide equal omnidirectional patterns in a horizontal space with precisely predetermined luminous intensity distribution in the vertical plane utilizing a single light source or multiple light sources with given photometric characteristics.
The aspherical reflective surface 1130 can be designed so that all light rays emitted from the light source 1140 are reflected through the omnidirectional window 1120 at an angular domain between a α′min and a α′max. A ray with a minimal angle, with respect to the vertical axis (α′min) should be reflected in the direction of the maximum elevation (α′max) and a ray with a maximum angle (α′max) should be reflected in the direction of the minimum elevation (α′min). Therefore, the waist of the outgoing beam will be formed in order to minimize the vertical size of the omnidirectional window.
a)-11(c) are exemplary illustrations of inverse square law compensation using source luminous intensity with angle distribution ƒ(α′)=1/tan2 (α1).
where E is illuminance, I is the source luminous intensity and D is the distance. Because,
where c is constant.
The design of the reflective surface 1130 is an iterative process.
α·ƒ(α)·α=ƒ′(α′)·Δα′ (1)
where a is the constant for the full cycle of the design. The condition in Equation (1) means that output energy in sector Δα′ is equal to emitted energy in the sector Δα with the factor a. Factor a is shown in Equation (2):
With the output power function ƒ′(α′) the boundary conditions αmin and αmax will determine factor a unambiguously. So as illustrated in
α′F=α′L+Δα′ (3)
is the local angle of the reflection cone, β can be found from the reflection's law as:
The coordinate of point C, which is next to the known point B can be found as the point of intersection of ray AC with the local conical surface from the system of linear equations:
Y−YB=tan β·(ZC−ZB)
Y=Z·tan α (5)
where the second equation is the equation of ray from point A with angle α with respect to the z-axis. So,
This can be repeated from point C to the new point of the reflective surface 1320 until the outgoing angle α′ will not reach α′max.
This method illustrates how the controller 1050 can design a light transformer to have a predetermined light distribution pattern. Accordingly, the controller 1050 iteratively calculates points on a light transformer to reflect light provided by a light source according to received maximum and minimum output angles based on a received location of a portion of the light transformer.
In some cases, when a single-source luminous intensity distribution does not provide adequate illumination to match desired specifications, an alternative design with multiple light sources, such as depicted in
c) illustrates how a horizontal pattern is created by way of overlapping individual outgoing patterns α′1, α′2, α′3, etc. When given a desired angular intensity distribution for a particular light source 1510, it is possible to choose the number of light sources 1510 and their relative location to provide a horizontal envelope with predetermined non-uniformity.
In operation, the light source 1810 can transmit light through the input surface 1820. The input surface 1820 can direct the light through the light channel 1840 by way of total internal reflection to the reflective surface 1830. The reflective surface 1830 can reflect the light according to a specified distribution pattern. For example, the reflective surface 1830 can reflect the light at an angle α′ where α′ falls between α′min and α′max. Additionally, the reflective surface can reflect the light in a manner similar to the semi-flush omnidirectional luminaire 300 of
The method of this invention is preferably implemented on a programmed processor. However, the method may also be implemented on a general purpose or special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an ASIC or other integrated circuit, a hardware electronic or logic circuit such as a discrete element circuit, a programmable logic device such as a PLD, PLA, FPGA or PAL, or the like. In general, any device on which resides a finite state machine capable of implementing the flowcharts shown in the Figures may be used to implement the processor functions of this invention.
While this invention has been described with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.
This application is a continuation of and claims priority to U.S. application Ser. No. 11/930,423, filed Oct. 31, 2007, which is a continuation of U.S. application Ser. No. 10/277,230, filed Oct. 21, 2002, now U.S. Pat. No. 7,503,669, which is a continuation-in-part of U.S. application Ser. No. 09/566,521, filed May 8, 2000, now U.S. Pat. No. 6,543,911, and all of which are herein incorporated by reference.
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