This invention generally relates to apparatus for cooling electro-optical components and more particularly relates to an apparatus for cooling a spatial light modulator.
Projectors and other large-scale electronic imaging systems use lasers and other high-intensity light sources for forming images. Light from these sources is directed to spatial light modulators (SLMs) such as digital micromirror devices (DMDs) including the Digital Light Processor (DLP) from Texas Instruments, Dallas, Tex., or Liquid Crystal Devices (LCDs). A considerable amount of heat can result when the intense light from laser or other sources is concentrated onto the SLM. Unless it is removed, this heat can quickly degrade component performance and image quality and, if allowed to rise to high levels, can destroy the SLM. Thus, solutions are needed for quickly and efficiently removing excess heat from the SLM device during operation.
Conventional solutions for cooling the SLM include passive devices, such as heat sinks, used with numerous types of solid-state electronic components. Convection cooling from the heat sink can be supplemented by fans or other devices to promote air circulation in order to draw heat away from the heat sink. As SLMs are reduced in size and light sources increase in intensity, however, a more aggressive cooling solution is typically required.
In response to this need, solutions using liquid coolant have also been proposed for providing heat management within laser projection apparatus. Using this type of solution, water or other liquid coolant is pumped along and around heat-generating and heat-sensitive components through a series of conduits, typically also leading to a radiator or other device for lowering the coolant temperature. Solutions for cooling electronic components that combine fin structures familiar to heat sink designs with liquid coolant flow include that shown in U.S. Pat. No. 7,331,380 entitled “Radial Flow Microchannel Heat Sink with Impingement Cooling” to Ghosh et al. Coolant devices and systems directed more particularly to the requirements of projection apparatus are disclosed, for example, in U.S. Patent Publication No. 2007/0165190 entitled “Heat Exchanger, Light Source Device, Projector and Electronic Apparatus” by Takagi, and U.S. Pat. No. 7,226,171 entitled “Optical Device and Projector” to Fujimori et al.
Although the use of liquid coolant is a step forward over heat-sink and forced-air cooling solutions, however, there is still a need for improvement. Unlike the heat problems presented with electronic components and packaging, the heat generation that is encountered by the SLM is concentrated within a much smaller area. Thus, conventional approaches that are designed to cool electronic circuitry by spreading out the heat more evenly prove to be poorly suited to the more localized cooling requirements for DMDs and other types of SLMs.
Thus, there is a need for a component cooling solution that compensates for the intense, localized heat that is typical of the SLM environment, particularly where laser light and other high-energy light source is concentrated over a small area.
The present invention addresses the need for localized cooling of a spatial light modulator (SLM) in an electronic projector or other imaging apparatus. This need is met by providing a cooling cell for drawing heat from a light modulator comprising an enclosure for conducting a fluid coolant, the enclosure comprising:
It is a feature of the present invention that it directs liquid coolant against the back side of a surface that is used to mount an SLM that receives intense light energy.
It is an advantage of the present invention that it draws heat outward and away from the rear surface of the SLM, thereby removing heat that is incident over a small area.
It is a further advantage of the present invention that it provides a compact cooling cell that is adaptable for the dense packing requirements of an electro-optical light modulator.
These and other features, and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention.
Figures shown and described herein are provided to illustrate principles of operation and structure according to embodiments of the present invention and may not be drawn with intent to show actual size or scale. Because of the relative dimensions and compactness of the component parts for the cooling cell of the present invention, a number of different views of the cooling cell are shown, including exploded views of the overall assembly and sectional views of the assembly and of major components in an embodiment of the present invention.
The terms “bottom” or “underside”, “top”, “behind”, and similar terms are used to indicate opposite surfaces or other features of components as described and illustrated herein, but are not intended to limit a component to a vertical or horizontal or facing orientation. Similarly “downward” and “upward” are used to describe directions for fluid flow relative to the shape of directing structures and do not define directions relative to the mounting orientation of the cooling device. It can be noted that one advantage of the cooling cell of the present invention relates to its adaptability for orientation in any direction, unlike a heat sink, in which, to take advantage of convection effects, cooling fins must normally be disposed in a vertical orientation and must be above the component being cooled.
Referring to
As is shown in the view from the underside of cooling cell 10 in
The exploded view of
The plan view of
The arrangement of cooling cell 10 components allows this device to be used in any orientation, so that modulator component 30 can be mounted in an appropriate orientation for the optical path inside the projector or other imaging system. By directing fluid coolant directly against the back side of component mounting surface 26, cooling cell 10 draws heat that is concentrated on modulator component 30 and directs this heat upward from well cavity 34 and outward so that it can exit cooling cell 10 and be cooled elsewhere in the cooling system.
Embodiments of the present invention thus address the need for cooling over the small area of the DMD or other SLM, providing a cooling solution that is suited to the stringent cooling requirements of a laser projector or similar apparatus. Advantageously, cooling cell 10 is compact, allowing dense packaging of the SLM and its supporting optics. Cooling cell 10 provides a cooling enclosure that has a relatively small parts count, and can be scaled to accommodate the dimensions and geometry of a reflective SLM, as well as the requirements of refractive modulator devices, such as the grating light valve (GLV) or grating electromechanical systems (GEMS) modulator.
Base 20 can be formed from any of a number of types of metal, using conventional molding techniques or using machining techniques made possible by Computerized Numerical Control (CNC) for single-part construction. EDM machining (Electrical Discharge Machining) is one specialized form of CNC machining that can be used for precision fabrication of complex parts from metal and other hard, conductive materials. Briefly, EDM selectively erodes material from a workpiece of a conductive substance by providing an electrical discharge across the gap between an electrode and the material to be removed. A dielectric fluid continually flows in the gap area around the electrode and flushes out the removed material. Wire EDM is one form of EDM, using a continuously moving wire as its electrode. Other techniques that may be suitable for fabricating base 20 can include conventional machining, laser machining, various etching techniques, water jets, and machining technologies in general that remove material from a solid block, forming and shaping cavities and structures of defined dimensions, controlling their overall contour and depth. Optionally, a suitable ceramic or other non-metallic heat-conductive material can be used.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. For example, cover 12 can be plastic, metal, ceramic, or other suitable material. Nozzle 32 can be formed as part of cover 12, or can be a separate component or can be formed as part of base 20. Cooling cell 10 can also be configured to support other types of electronic or electro-optical components in addition to SLMs, such as gratings or other diffractive devices, reflectors, dichroic surfaces, or beam splitters, for example. Thus, what is provided is an apparatus and method for cooling any type of component, particularly one for which intense heat is generated over a relatively small area.