Abstract:
An optical assembly for use with a spectrophotometer. The optical assembly may comprise an illumination source, a detection sensor, a monitor sensor, and an optical piece having a first side adapted to face a sample. The optical piece may define an illumination channel extending from the illumination source toward the first side. The optical piece may also define a detection channel extending from the first side toward the detection sensor. In addition, the optical piece may define a monitor channel extending from the illumination channel toward the monitor sensor. Also, a light emitting diode (LED) assembly for use with an optical measurement device. The LED assembly may comprise a substrate having a top surface and a bottom surface and a plurality of LED dies positioned on the substrate to emit light in a first direction normal to the bottom surface of the substrate. The LED assembly may also comprise a plurality of leads in electrical contact with the plurality of LED dies. The plurality of leads may be positioned on the bottom surface of the substrate, and may be configured to surface-mount to a board.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/710,920 filed on Aug. 24, 2005, and U.S. Provisional Application No. 60/708,222, filed on Aug. 15, 2005, which are incorporated herein by reference. This application is also related to a concurrently filed United States Patent Application entitled, “IMPROVED OPTICAL INSTRUMENT,” by Jon Nisper and Mike Mater, which is herein incorporated by reference. 
     
    
     BACKGROUND  
       [0002]     Spectrophotometers and other similar optical instruments have been used in industry for many years to measure optical properties of various objects. A spectrophotometer operates by illuminating a sample surface or other object and then sensing the light that is either reflected by or transmitted through the sample. The reflected or transmitted light may then be characterized by wavelength and intensity. Traditional spectrophotometers are large bench top instruments suitable for use in a lab or similar environment. As advances have been made in microelectronics, smaller, more portable spectrophotometers have been developed.  
         [0003]     These smaller devices, however, suffer from several significant disadvantages. For example, it is difficult to find suitable illumination sources for smaller spectrophotometers. Traditional incandescent bulbs of sufficient brightness are often too big and use too much energy to be practical in smaller applications. Many portable spectrophotometers use light emitting diodes (LED&#39;s) as an illumination source, however, these devices create their own problems. First, even LED&#39;s manufactured to the highest tolerances often show an unacceptable variation in spectral output from unit to unit. Also, the spectral output of an LED tends to change with temperature, causing spectrophotometers to be temperature dependent. Additional problems arise as individual spectrophotometer components are placed in close proximity with one another. For example, when the illumination source and detection sensors are placed in close proximity, light leakage from the source is often picked up by the sensors, skewing their readings.  
       SUMMARY  
       [0004]     In one general aspect, the invention is directed to an optical assembly for use with an optical instrument. The optical assembly may comprise an illumination source, a detection sensor, a monitor sensor, and an optical piece having a first side adapted to face a sample. The optical piece may define an illumination channel extending from the illumination source toward the first side. The optical piece may also define a detection channel extending from the first side toward the detection sensor. In addition, the optical piece may define a monitor channel extending from the illumination channel toward the monitor sensor. In various embodiments, the monitor sensor may be a dual beam reference sensor capable of discerning color.  
         [0005]     In another general aspect, the invention is directed to a light emitting diode (LED) assembly for use with an optical measurement device. The LED assembly may comprise a substrate having a top surface and a bottom surface and a plurality of LED dies positioned on the substrate to emit light in a first direction normal to the bottom surface of the substrate. The LED assembly may also comprise a plurality of leads in electrical contact with the plurality of LED dies. The plurality of leads may be positioned on the bottom surface of the substrate, and may be configured to surface-mount to a board.  
         [0006]     In yet another general aspect, the invention is directed to a spectrophotometer. The spectrophotometer may comprise a circuit board, an illumination source, and a sensor. The circuit board may comprise a first surface and a second surface opposite the first surface, and may have a first optically transparent opening between the first surface and the second surface. The illumination source may be mounted on the first surface of the circuit board, and may be mounted to direct light through the first optically transparent opening. The sensor may be mounted on the second surface of the circuit board. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0007]     Embodiments of the present invention are described herein, by way of example, in conjunction with the following figures, wherein:  
         [0008]      FIG. 1  shows an exploded view of a spectrophotometer according to various embodiments;  
         [0009]      FIG. 2-3  show views of a spectrophotometer circuit board according to various embodiments;  
         [0010]      FIGS. 4-6  show views of a light emitting diode (LED) chip according to various embodiments; and  
         [0011]      FIGS. 7-10  show views of an optical piece according to various embodiments.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]     Embodiments of the present invention are directed to portable optical instruments including, for example, spectrophotometers, densitometers, sensitomers, photometers, etc., and various components thereof.  FIG. 1  shows an exploded view of an exemplary instrument  100  according to various embodiments. The instrument  100  comprises a circuit board  102  and an enclosure for the circuit board that includes enclosure bottom  104 , enclosure top  106  and covers  108  and  116 .  
         [0013]     The circuit board  102 , also pictured in  FIGS. 2 and 3 , includes various optical and electronic components necessary to implement the instrument  100 . For example, the circuit board  102  may include optical components such as, for example, illumination source  114  and sensors  118 ,  120 , as shown in  FIG. 2 . The illumination source  114  may be any kind of suitable illumination source and may include, for example, one or more incandescent sources, one or more fluorescent sources, one or more light emitting diodes (LED&#39;s), etc. In various embodiments, all or a portion of the optical components  114 ,  118 ,  120  may be enclosed by an optical piece  110 . The optical piece may direct light emitted from or received by the various optical components, for example, as described in more detail below.  
         [0014]     The sensors  120 ,  118  may be any sort of sensor or photo-sensitive device. Detection sensor(s)  120  may be directed to receive light reflected by or transmitted through a sample surface (e.g., by optical piece  110 ). Monitor sensor(s)  118  may be directed to receive and monitor light emitted by the illumination source  114  (e.g., by optical piece  110 ). In various embodiments, the sensors  120  and/or monitor sensors  118  may have the capability to discern color. The sensors  118 ,  120  may be constructed according to any suitable technology, though, in various embodiments, the sensors  118  and/or  120  may be constructed using low cost CMOS technologies. Also, in various embodiments, each individual sensor  120 ,  118  may be comprised of many individual sensors, for example a 16×16 array of 64 individual sensors or a 640×480 array of 307,200 sensors (e.g., such as an RGB CMOS chip similar to those used by cameras). Further, such individual sensors may have individual spectral filters located on top of them. In this way, the individual sensors sample only a portion of the spectrum reflected from an object for each LED. In various embodiments the individual sensors may be addressed individually, or sensors with similar color filters may be addressed together.  
         [0015]     The circuit board  102  may also include other components for implementing non-optics portions of the instrument  100 . For example, the circuit board  102  may include a processor  124  for configuring the optics and interpreting signals from the sensors  118 ,  120 . A memory  123  in communication with the processor  124  may store instructions for the processor  124 , results of spectrophotometer measurements, etc. The memory  123  may include any suitable kind of volatile and/or non-volatile memory device. A display  112  in communication with the processor  124  may be used to provide a user interface to a user of the instrument  100 , for example, to display results of measurements, receive input parameters and other instructions for the instrument  100 , etc. The user may provide input to the instrument  100  via input buttons  128 . An actuation button  116 , may allow a user to cause the instrument  100  to take a reading. It will be appreciated that, in various embodiments, any suitable computer or computer devices may be included on the circuit board  102  instead of, or in addition to, processor  124 , memory  123 , etc.  
         [0016]      FIGS. 4-6  show detailed views, according to various embodiments, of an LED chip illumination source  400 . The LED chip  400  may provide light of various different wavelengths or colors. In various embodiments, the LED chip  400  may comprise a substrate  402 . The substrate  402  may be made of a ceramic or other high thermal conductivity material, and have a base portion  404  and raised portion  406 . The raised portion  406  may define a cavity  412 . LED dies  410  may be mounted on a surface of the substrate  402  within the cavity  412  as shown. The LED dies  410  may be electrically connected to leads  408 , which may be used to provide current and voltage to the LED dies  410 , causing them to emit light. In various embodiments, at least a portion of the inside edges of the cavity  412  may be constructed of a reflective material, such as, for example SPECTRALON or a suitable ceramic material. In this way, light from the LED dies  410  that is incident on the edges of the cavity  412  may be reflected away from the edges, reducing light leakage. Also, in other various embodiments, at least a portion of the inside edges of the cavity  412  may include a reflective coating, such as aluminum, gold, SPECTRAFLEC coating, etc. In various embodiments, all or a portion of the leads  408  may also serve as a reflective material.  
         [0017]     It will be appreciated that each of the LED dies  410  may have a specific peak wavelength. The LED dies  410  may all have different peak wavelengths, or may include dies  410  with approximately the same peak wavelengths. For example, multiple dies  410  with the same or similar peak wavelengths may be used to boost the output power at a desired wavelength. The number of LED dies  410  and the number of peak wavelengths may be selected based on the specific requirements of the instrument  100 . For example, in various embodiments there may be between six and sixteen dies  410  having between six and sixteen different spectral outputs. Also, it will be appreciated that various other LED components may accompany dies  410 . For example, in various embodiments, LED dies  410  may be accompanied by various reflectors, lenses, covers, etc.  
         [0018]     In various embodiments, a filter  414  may be positioned over the LED dies  410 , as shown. The filter  414  may attenuate unwanted wavelengths from the output of LED dies  410 . For example, some LED&#39;s have emission bands other than their advertised peak wavelength. These extra emission bands are often in the infrared portion of the spectrum, but can be in the visible or ultraviolet portions as well. Sensors  118 ,  120  may be sensitive to the additional emission bands, causing their readings to be skewed. Accordingly, the filter  414  may be selected to attenuate any additional output bands that may be present. For example, if additional infrared output bands are a concern, the filter  414  may be chosen to attenuate radiation in the infrared portion of the spectrum. Also, in various embodiments, the filter  414  may be used to at least partially compensate for output variations between LED dies  410  due to production, temperature, etc. For example, the filter  414  may be a comb filter that attenuates light at multiple wavelengths and passes the advertised peak wavelengths of the LED dies  410 . The comb filter may be manufactured according to any suitable method including, for example, a Fabry-Perot method.  
         [0019]     In use, the LED chip  400  may be mounted over a hole, or other transparent area of the circuit board  102  allowing the LED chip  400  to direct illumination through the circuit board  102 . For example, the raised portion  406  of the substrate  402  may fit through a hole in the circuit board  102 . In various embodiments, the LED chip  400  may be mounted on a first side of the circuit board  102 , and sensors  118 ,  120  may be mounted on a second side of the circuit board, opposite the first side. It will be appreciated that mounting the LED chip  400  and sensors  118 ,  120  on opposite sides of the circuit board  102  may reduce unwanted noise due to light leakage. The LED chip  400  may be secured and electrically connected to the circuit board  102  via leads  408 , which may be surface mounted to corresponding pads (not shown) on circuit board  102 .  
         [0020]     The LED chip  400  may also include various other features to ease production. For example, in various embodiments, the substrate  402  and filter  412  may be made of heat resistant material (e.g., the substrate  402  may be made of ceramic and the filter  412  may be made of glass). Accordingly, the LED chip  400  may be mounted to the circuit board  102  according to known infrared (IR) solder reflow processes without damage to the chip  400 . Also, in various embodiments, the LED chip  400  may include one or more orientation-specific features, such as feature  416 . These orientation-specific features may mesh with corresponding features (not shown) on circuit board  102  only when the LED chip  400  is in a correct orientation relative to the circuit board  102 . In this way, the correct orientation of the LED chip  400  may be verified during production.  
         [0021]      FIGS. 7-10  show views, according to various embodiments, of the optical piece  110 . The optical piece  110  may define a series of channels for directing light to and from the illumination source  114  (e.g., LED chip  400 ) and the respective sensors  118 ,  120 . For example, an illumination channel  702  may direct light from the illumination source  114  to a sample (not shown). Detection channels  704  may direct reflected light from the sample to detection sensors  120 . A monitor channel  706  may direct light from the illumination channel  702  to one or more monitor sensors  118 . The optical piece  110  may have a first surface  701  configured to be brought into optical contact with a sample, and a second surface  703  configured to be optically coupled to the illumination source  114  and respective sensors  118 ,  120 .  
         [0022]      FIG. 9  shows a view of the surface  703  of the optical piece  110 , according to various embodiments. The surface  703  may define various features  714 ,  716 ,  718  that facilitate coupling of the various channels  702 ,  704 ,  706  to the various optical components  114 ,  118 ,  120 . In various embodiments, as shown by  FIG. 10 , the features  714 ,  716  and  718  may be indentations extending from the surface  703  to the respective channels  702 ,  704 ,  706 . For example, indentations  714  are shown extending from the surface  703  to detection channels  704 . In use, the detection sensors  120  may fit within indentations  714 . In this way, noise due to light leakage may be further minimized. Likewise, indentation  716  may extend from the surface  703  to the monitor channel  706 , allowing monitor sensor  118  to be received within the indentation  716  and thereby coupled to the monitor channel  706 . Feature  718  may also be configured to receive illumination source  714  and couple it to the illumination channel  702 .  
         [0023]     In various embodiments, the channels  702 ,  704 ,  706  may be configured to enhance the optical properties of the instrument  100 . For example, inside surfaces of the channels  702 ,  704 ,  706  may be polished or may include a reflective coating to enhance their reflectivity. Also, the shapes of the channels  702 ,  704 ,  706  may be selected based on the channels&#39; purpose. For example, illumination channel  702  may be elliptical or hyperbolic. In this way light from the illumination source  114  may be efficiently collected and provided to the sample at surface  701  with improved spatial uniformity across wavelengths and LED outputs. The illumination channel  702  may also be formed into other shapes (e.g., more complex shapes) to facilitate even illumination. For example, in various embodiments, the illumination channel  702  may be fashioned in a shape that is not a surface of revolution. Also, in various embodiments, the illumination channel may be formed with ribs or facets running longitudinally from the illumination source  114 .  
         [0024]     Also, for example, the detection channels  704  may be shaped as a partial cone or cylinder. Accordingly, light received by the detection channels  704  from surface  702  of the piece  110  may be focused toward the detection sensors  120  received within features  714 . Monitor channel  706  may be shaped so as to sample light emitted from the illumination source  114  and deliver it to the monitor sensor  118  such that the signal is proportional to the detector channel signals. This may be accomplished through optical design which balances the amount of light received by the monitor sensor  118  from each individual LED and ensures that it changes over temperature in a fashion similar to the detector channels. The monitor channel  706  may also be shaped to ensure that LED&#39;s included in the illumination source are sampled proportionally, regardless of their distance from the monitor sensor  118 . In various embodiments, the monitor channel  706  may also be configured such that its response either does not change with temperature, or does change with temperature, but in a predictable way.  
         [0025]     The optical piece  110  may also have various other features that facilitate easy manufacturing. For example, in various embodiments, the optical piece  110  may be constructed of one contiguous piece. In various other embodiments, the optical piece  110  may be constructed of three or fewer pieces. The pieces may be fit together according to any suitable method, for example, the pieces may snap together without the use of separate fasteners. In various embodiments, the number of pieces of the optical piece  110  may be less than the total number of channels included therein. The piece or pieces of the optical piece  110  may be constructed according to any suitable manufacturing method including, for example, injection molding.  
         [0026]     In various embodiments, the monitor sensor  118  may be able to discern colors. Accordingly, the sensor  118  and channel  706  may be referred to as dual beam reference sensor  118  and channel  706  respectively. A dual beam reference sensor  118  may allow the spectral output of the illumination source  114  to be monitored. In various embodiments, readings of the instrument  100  may be corrected for variations in the spectral output of the illumination source. Also, it will be appreciated that when a dual beam reference sensor  118  is used, the dual beam reference channel  706  may be configured considering additional considerations. For example, the channel  706  may be achromatic, meaning that its response should not change with wavelength. In this way, light of different colors emitted by the illumination source  114  may be directed to the sensor  118  at an intensity proportional to the emission intensity. Also, in various embodiments the response of the channel  706  may change with wavelength, but in a predictable way.  
         [0027]     It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for purposes of clarity, other elements, such as, for example, some specific tasks of the non-execution service provider units described above, etc. Those of ordinary skill in the art will recognize that these and other elements may be desirable. However, because such elements are well known in the art and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein.  
         [0028]     As used herein, a “computer” or “computer system” may be, for example and without limitation, either alone or in combination, a personal computer (PC), server-based computer, main frame, server, microcomputer, minicomputer, laptop, personal data assistant (PDA), cellular phone, pager, processor, including wireless and/or wireline varieties thereof, and/or any other computerized device capable of configuration for processing data for standalone application and/or over a networked medium or media. Computers and computer systems disclosed herein may include operatively associated memory for storing certain software applications used in obtaining, processing, storing and/or communicating data. It can be appreciated that such memory can be internal, external, remote or local with respect to its operatively associated computer or computer system. Memory may also include any means for storing software or other instructions including, for example and without limitation, a hard disk, an optical disk, floppy disk, ROM (read only memory), RAM (random access memory), PROM (programmable ROM), EEPROM (extended erasable PROM), and/or other like computer-readable media.  
         [0029]     While several embodiments of the invention have been described, it should be apparent that various modifications, alterations and adaptations to those embodiments may occur to persons skilled in the art with the attainment of some or all of the advantages of the present invention. It is therefore intended to cover all such modifications, alterations and adaptations without departing from the scope and spirit of the present invention as defined by the appended claims. We claim: