|Publication number||USRE41240 E1|
|Application number||US 10/424,334|
|Publication date||Apr 20, 2010|
|Filing date||Apr 25, 2003|
|Priority date||Mar 26, 1999|
|Also published as||DE69903360D1, DE69903360T2, EP1166164A1, EP1166164B1, US6282027, WO2000058771A1|
|Publication number||10424334, 424334, US RE41240 E1, US RE41240E1, US-E1-RE41240, USRE41240 E1, USRE41240E1|
|Inventors||Thomas A. Hough|
|Original Assignee||Genlyte Thomas Group Llc|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (35), Classifications (23), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to lighting instruments, and especially to devices and apparatus for controlling the distribution of light energy in non-imaging illumination applications.
Four qualities of lighting as described by Stanley McCandless in his book “A Method of Lighting the Stage” are intensity, color, distribution, and movement. Whereas intensity and color may be said to refer to attributes of particular light beams, distribution refers to the arrangement of light sources about the stage and the directions in which they are aimed. Intensity, color, and distribution are primary qualities, whereas movement is emergent from changes in the primary qualities. Movement in this sense occurs as the condition of the other three qualities changes over time. A simple adjustment of intensity results in movement. No change in any of the other three qualities can occur without resulting in movement, and movement cannot occur without the passage of time from moment to moment.
The passage of time, over the years, has seen all three of the primary qualities of lighting become subject to motorized mechanization and computerized remote control so that in the case of distribution, movement (in a conventional sense) has become overtly mechanized. Moving lights, virtually unheard of twenty years ago, have revolutionized the art of lighting the stage, enabling dynamic lighting effects not possible before the advent of computer-controlled lighting systems having automatically variable qualities. After the novelty of overtly dynamic movement subsides, an appreciation of subtlety once again becomes possible so that we might consider the quality of distribution from the aspect of variable beam divergence or beam spread.
In stage lighting, it is often desirable to expand the light beam from a so-called wash luminaire to illuminate a broader area. A wash luminaire can produce such an effect using a light source and a concave reflector which are moveable with respect to a lens, such as disclosed in U.S. Pat. No. 3,428,800 or in U.S. Pat. No. 3,665,179. The divergence angle of the light beam varies depending upon the position of the source and reflector with respect to the lens. Popular variable-divergence luminaires, such as the Cadenza PC manufactured by Rank Strand of the United Kingdom and the 2KW Fresnel manufactured by Mole-Richardson of California and others, use such an optical system to control the divergence angle of the light beam projected by the luminaire. A positive, or convex, front lens illuminated by a lamp and retroreflector combination produces a substantially columnar light beam and projects a relatively small pool of light when the lamp is placed at the focus of the lens. As the lamp and reflector combination is moved in either direction away from the focus of the lens, the beam diverges from columnar to project a larger pool of light. Such a system is quite large and requires many inches of travel for the lamp and reflector combination along the optical axis of the lens. The carrier mechanism of these luminaires is typically manually adjustable and the large glass front lens, typically eight to ten inches in diameter, is thick and heavy even with the significant weight reduction gained by the Fresnel design used by Mole-Richardson.
Another common system for controlling the divergence angle of a light beam is disclosed in U.S. Pat. No. 4,602,321 and uses a lamp which is movable with respect to a parabolic reflector. When the lamp is placed at the focus of the reflector, a substantially columnar light beam emerges and projects a small pool of light. As the lamp is moved rearwardly along the optical axis of the reflector and away from the focus of the reflector, the beam diverges from columnar to form a larger pool of light. This system requires an adjustable carriage for the lamp socket and frequently requires provisions for minor (manual) adjustments along two additional axes orthogonal to the optical axis, so as to maintain proper alignment of the lamp on the optical axis, in addition to motorized adjustment along the optical axis for controlling beam divergence.
Many commonly used systems for controlling the divergence angle of a light beam use two or more lens elements is series and in combination with a fixedly mounted lamp and a fixedly mounted reflector. In these systems, one or more of the lens elements are movable with respect to the lamp and reflector to vary the divergence angle of a light beam formed thereby. Some common examples are disclosed in U.S. Pat. Nos. 2,076,240; 2,650,292; 2,950,382; 3,302,016; 3,594,556; 4,462,067; 4,519,020; 4,709,311; 4,739,456; 5,029,992; 5,404,283; among others. Some of these systems are used in image-projecting applications in which a hard-edged spot of light is projected onto a distant surface such as a stage floor or backdrop, and may also be used to project complex images formed by objects placed in a focal plane of the projection lens system, such as described, for example, in U.S. Pat. No. 4,779,176.
Another, unique system for controlling the energy distribution of a light beam in a non-imaging application is disclosed in U.S. Pat. No. 5,774,273 and uses a variable-geometry liquid-filled lens having a deformable, transparent membrane supported by a transparent, multi-cellular structure forming an array of variable-power lenslets. An optically clear liquid is pumped into or out of the structure to deform the membrane into an array of convex or concave lenslets having adjustable optical power to control energy distribution. A motorized pump is used as the actuator, and the system may be operated by remote control.
It is nevertheless desirable to have a solid-state apparatus, not relying upon liquid components, for controlling the energy distribution of a light beam in non-imaging applications, which apparatus can economically be made large in diameter and yet be light-weight and operable over a short distance along the optical axis of a luminaire.
The present invention provides a solid-state apparatus which is economically made, is scalable to large diameters yet operates over a short distance along the optical axis of a luminaire to control the distribution of light energy in non-imaging illumination applications.
In accordance with the present invention, an apparatus for controlling divergence of a beam of light comprises a first multiple-lens array including a plurality of plano-convex lenses arranged in a pattern and supported on a transparent substrate: a second multiple-lens array including a plurality of plano-concave lenses arranged in a pattern and supported on a transparent substrate; the first and second multiple-lens arrays being formed so that a curvature of convex lens surfaces of the first array matches a curvature of concave surfaces of the second array, and each convex lens surface of the first array corresponds to and is aligned with a matching concave lens surface of the second array; the first and second multiple-lens arrays being disposed serially and coaxially in a light beam path such that convex-lens surfaces of the first array are generally adjacent and coaxially aligned with concave surfaces of the second array; and one of the multiple-lens arrays being movable coaxially with respect to the other multiple-lens array.
The operative concepts of an illumination optical system according to the present invention are described with reference to
In a “zero-power” state, as shown in
The first lens 1, having a positive optical power, tends to converge the light beam upon a focus point FP2, after which point the light beam will diverge. The second lens 2, having a negative optical power, tends to diverge a collimated light beam. When the apex 15 of the concave surface 13 of the second lens is positioned at the focus point FP2 of the first lens, as shown in
The behavior of the light beam passing through the lens system comprising the first, plano-convex, lens 1 and the second, plano-concave, lens 2, is governed by Snell's Law, in accordance with which a light ray passing from air to glass (from a less dense optical medium into a more dense optical medium) is refracted towards the surface normal while a light ray passing from glass to air (from a more dense medium to a less dense medium) is refracted away from the surface normal. The angle of divergence of the light beam is practically zero (assuming a collimated beam emerging from the reflector 4) when the first and second lenses are positioned as closely together as possible, and the angle of divergence increases as the separation between the lenses increases.
The results of computer simulation modelling the lens system according to the present invention are illustrated in
A preferred embodiment of the present invention, as shown in
A practical system may be constructed such that each multiple-lens array comprises a plurality of perimetrically circular lenslets 22 (convex) or 33 (concave) in an hexagonal arrangement as shown in FIG. 12. The perimeters of the individual lenslets have circular shapes and the spaces between the lenslets in this arrangement comprise approximately 10 per cent of the area of the array, through which no significant refraction takes place. Consequently, the area between the perimetrically circular lenslets is preferably masked to avoid a “hot-spot” concentration of un-diverted light rays in the center of a light beam that is subject to a significant angle of beam divergence through the system. Alternatively, an hexagonal array of hexagonally-trimmed lenslets, or perimetrically hexagonal lenslets, avoids a 10 per cent loss of light intensity through the system by avoiding the use of a mask, but the resulting beam through such a system has an hexagonal profile and projects an hexagonal spot of light. As another alternative, the spaces between perimetrically circular lenslets could be covered with additional, secondary, curved optical surfaces with corresponding pairs of matching secondary curved optical surfaces on the two multiple-lens arrays.
The preferred embodiment is economically constructed as a first and second array of perimetrically circular lenslets that are molded, in an hexagonal arrangement, on surfaces of transparent plates and mounted in suitable carriers. An opaque mask is provided for one or both arrays to fill in the spaces between the circular lenslets. As shown in
As shown in
The linear actuators are preferably stepper motors such as the Z20841 series motors made by Haydon Switch and Instrument, Inc. of Waterbury, Conn., which are arranged to drive a threaded drive shaft 55 through the body of the motor in response to electrical drive signals. The apparatus may be assembled with the two mounting rings in contact with each other such that the two multiple-lens arrays are properly aligned and at minimal separation for the zero-power state, and the drive shafts can then be secured to the flanges of the first mounting ring. Thereafter, the motors may be wired in series and operated by a suitable controller so that the extension of the various drive shafts remains identical through the range of operation and the multiple-lens arrays are maintained parallel to each other. Limit switches or physical stops may be employed to constrain the operation of the apparatus to within a usable range such as hereinbefore described. The apparatus is preferably remotely controlled via an electronic control system in communication with a supervisory control console such as described in U.S. Pat. No. 4,980,806.
Other types of actuators can also be used, such as electric servo motors, pneumatic or hydraulic actuators, or even manually-operated actuators so long as the separation between the two multiple-lens arrays is controlled within a usable range and the multiple-lens arrays are maintained parallel to each other. The control system might also be capable of operation independently of a supervisory control console or even be free-running, if so desired, to oscillate between two extents of travel. Ideally, however, the apparatus forms part of an automated, multiple-parameter lighting instrument providing remotely-controlled azimuth and elevation adjustment and/or remotely-controlled adjustment of light beam color such as shown, for example, in U.S. Pat. No. 5,367,444.
Experimental results obtained from a prototype lens system according to the preferred embodiment are shown in FIG. 11. Four curves superimposed over each other onto a graph relating light intensity in foot-candles (on a logarithmic scale) to beam radius in inches illustrate the distribution of light energy (irradiance) 20 feet (six meters) from the light source. A first curve represents irradiance with the two lens arrays at zero separation, and shows peak light intensity of over 1000 foot-candles in the center of the beam and intensity of about 20 foot-candles at about 25 inches (635 mm) from the center. A second curve represents irradiance with the two lens arrays separated by 0.3 inches (7.6 mm), and shows peak intensity of about 300 foot-candles in the center of the beam and intensity of 20 foot-candles at about 38 inches (965 mm) from the center. A third curve represents irradiance with the two lens arrays separated by 0.6 inches (15 mm), and shows peak intensity of about 150 foot-candles in the center of the beam and intensity of 20 foot-candles at about 60 inches (1524 mm) from the center. A fourth curve represents irradiance with the two lens arrays separated by 0.9 inches (23 mm), and shows peak intensity of about 50 foot-candles in the center of the beam and intensity of 20 foot-candles at about 50 inches (1270 mm) from the center, with slightly more energy content in the fringes of the beam between 75 and 100 inches (762 to 1016 mm) from the center than does the third curve.
The curves of
An optical system for a wash luminaire, used in non-imaging illumination applications, as shown in FIG. 15 and
The system as shown in
The output lens 67 as shown is a well-known type of lenticular lens which shapes the beam to project a non-circular pool of light, but could just as easily be a water-clear lens imparting no appreciable beam divergence or a lightly-stippled lens imparting a small amount of diffusion to the exiting light beam 68. Interchangeable lenses of these types are widely used in the VL5™ luminaire made by Vari-Lite, Inc. of Dallas, Tex. Several different types of lenticular lens are used individually with the VL5 luminaire depending upon the desired beam shape, and the zoomable beam-spreader of the present invention can be used in combination with such a lens to spread the beam in whatever shape is imparted by the lenticular exit lens.
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|U.S. Classification||359/618, 359/623, 359/621|
|International Classification||F21W131/406, F21V14/00, G02B17/08, F21V5/00, F21V13/00, G02B3/00, G02B15/14, F21S10/00, F21S2/00, F21Y101/00, G02B27/00, G02B27/10|
|Cooperative Classification||G02B15/14, G02B3/0062, G02B26/0875, G02B3/0075, G02B27/0961, G02B3/0056|
|European Classification||G02B26/08R, G02B27/09S2L1|