Abstract:
A light source. The light source may comprise a substrate comprising at least one flexible portion; an illumination source mounted on the flexible portion; and a structural unit positioned relative to the flexible portion to determine a deflection angle of the flexible portion. An illumination angle of the light source may be dependent on the deflection angle of the flexible portion. Instruments including the light source are also disclosed, along with a method of changing the illumination angle of the light source. The method may comprise the steps of removing the structural unit and replacing the structural unit with a second structural unit positioned relative to the flexible portion to deflect the flexible portion by a second deflection angle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application Ser. No. 60/788,900 filed on Apr. 3, 2006. 
     
    
     BACKGROUND  
       [0002]     Optical instruments such as calorimeters, densitometers, dot meters, gloss meters, and the like typically include an integral light source for illuminating a specimen and one or more sensors for receiving light reflected from or transmitted through the specimen. Characteristics of the specimen (e.g., color, transmittance, reflectance, etc.) may then be determined by measuring and analyzing properties of the received light. An accurate determination of such characteristics generally requires that light emitted from the light source strike the specimen at a pre-determined illumination angle(s). Colorimeters and densitometers, for example, may require a 45°/0° illuminator/sensor geometry, whereas gloss meters may require a number of different illuminator/sensor geometries depending upon surface characteristics of the particular specimen.  
         [0003]     During instrument development and testing, it is frequently necessary to alter the illumination angle(s) of the emitted light for, among other things, determining the operating charactertics and optimal configuration of the instrument. Performing such adjustments using conventional light source designs may be inconvenient and require expensive and/or time-consuming modifications of the light source. Furthermore, conventional light sources are typically customized to their respective instruments and are not easily adapted for use in other instruments having different illumination angle requirements. Therefore, for manufacturers having different lines of instruments, the inability to easily adapt a light source for use in different instruments may result in relatively high design and manufacturing costs.  
         [0004]     Accordingly, there exists a need for a light source for use in the above-identified instruments, as well for use in other instruments and illumination applications, that enables the illumination angle(s) of emitted light to be quickly and easily adjusted.  
       SUMMARY  
       [0005]     In one aspect, the present invention is directed to a light source. The light source may comprise a substrate comprising at least one flexible portion; an illumination source mounted on the flexible portion; and a structural unit positioned relative to the flexible portion to determine a deflection angle of the flexible portion. An illumination angle of the light source may be dependent on the deflection angle of the flexible portion. Instruments including the light source are also disclosed, along with a method of changing the illumination angle of the light source. The method may comprise the steps of removing the structural unit and replacing the structural unit with a second structural unit positioned relative to the flexible portion to deflect the flexible portion by a second deflection angle.  
         [0006]     In another aspect, the present invention is directed to another light source. This light source may comprise a substrate comprising at least one flexible portion; an illumination source mounted to the flexible portion; a holder positioned in an illumination path of the illumination source; and a backer. The at least one flexible portion may be positioned between the backer and the holder. Also, a deflection angle of the flexible portion may be determined by a taper angle of at least one of the backer and the holder. 
     
    
     DESCRIPTION OF THE FIGURES  
       [0007]      FIG. 1  illustrates an exploded view of an instrument according to various embodiments;  
         [0008]     FIGS.  2  illustrates a top view of various embodiments of the holder of the instrument of  FIG. 1 ;  
         [0009]      FIG. 3  illustrates various embodiments of the backer of the instrument of  FIG. 1 ;  
         [0010]      FIG. 4  illustrates various embodiments of the flexible substrate of the instrument of  FIG. 1 ;  
         [0011]      FIG. 5  illustrates various embodiments of the chassis of the instrument of  FIG. 1 ;  
         [0012]      FIG. 6  illustrates the backer of  FIG. 3  attached to the chassis of  FIG. 5 ;  
         [0013]      FIG. 7  illustrates a bottom view of the chassis having the backer, the flexible substrate, and the holder installed thereon according to various embodiments; and  
         [0014]      FIG. 8  illustrates the dependence of the illumination angle upon the deflection of the flexible portions of the flexible substrate according to various embodiments. 
     
    
     DESCRIPTION  
       [0015]      FIG. 1  illustrates an exploded view of an instrument  10  according to various embodiments of the present invention. The instrument  10  may generally be any instrument configured for illuminating a specimen  30  and may also analyze the reflected light (or light transmitted through the specimen  30 ) to determine one or more of optical characteristics of the specimen  30 . Such instruments may include, for example, spectrophotometers, calorimeters, densitometers, gloss meters, dot meters, etc. In the illustrated embodiments, the instrument  10  is configured for analyzing reflected light. According to various embodiments, the instrument  10  comprises a light source  15  and a light sensor assembly  20  mounted to a chassis  25 . In use, light generated by the light source  15  is emitted from the instrument  10  and illuminates the specimen  30 . A portion of the emitted light that is reflected from the specimen  30  may be received through apertures of the light source  15  and chassis  25  and directed to the light sensor assembly  20 . Signals generated by the light sensor assembly  20  responsive to the reflected light may be processed to determine characteristics of the specimen  30 . Signal processing may be conducted using processing means internal or external to the instrument  10 .  
         [0016]     According to various embodiments, the light source  15  may be configured to assume various illumination angles. For example, the light source  15  may generally comprise a substrate  45  having at least one flexible portion (e.g., such as flexible portions  80  shown in  FIG. 4 ). Each flexible portion may have one or more illumination sources, such as light emitting diodes  85  (LED&#39;s), mounted thereto. The flexible portion or portions of the substrate  45  may be capable of pivoting to provide different illumination angles and may be secured at a given illumination angle by one or more structural units, such as a holder  35  and a backer  40 . According to various embodiments, the light source  15  may further comprise a nose portion  47  and any suitable fastening means (not shown) for retaining the light source  15  in the mounted position upon the chassis  25 .  
         [0017]     The holder  35  may be positioned between the illumination source and the specimen  30  (e.g., in an illumination path of the illumination source or sources). Also, the holder  35  may be made from any sort of light-transmitting material.  FIG. 2  illustrates a top view and cross-sectional views, according to various embodiments, of the holder  35 . The holder  35  may track the shape of the flexible portions. For example, in embodiments where the light source  15  is generally ring-shaped, the holder  35  may also be ring-shaped and may exhibit an upwardly-tapered frusto-conical geometry.  
         [0018]     According to various embodiments, the holder  35  may comprise one or more shoulder portions  50 , with each shoulder portion  50  exhibiting a taper angle θ T . In embodiments comprising more than one shoulder portion  50 , the shoulder portions  50  may be arranged in an off-set configuration wherein one or more shoulder portions  50  are shifted inward by a distance d toward a center axis of the holder  35  relative to the other shoulder portions  50 . For example, as shown in the embodiments of  FIG. 2 , the holder  35  may comprise eight shoulder portions  50 , with four of the shoulder portions  50  shifted inward toward the center axis by a distance d in an alternating fashion relative to the other four shoulder portions  50 . This may be, for example, to accommodate LED&#39;s  85  or other illumination sources of differing sizes, for example, as discussed in more detail below.  
         [0019]     It will be appreciated that the configuration of  FIG. 2  is provided by way of example only, and that other configurations may be employed. In other embodiments, for example, the shoulder portions  50  may not be off-set from one another. In this way, the holder  35  may have a continuous inner surface. In still other embodiments, one or more of the shoulder portions  50  may be shifted inward by a distance different than that of other shifted shoulder portions  50 . Additionally, although the taper angles θ T  of the shoulder portions  50  in the illustrated embodiments may generally be equal, one or more of the shoulder portions  50  may have a taper angle θ T  different from that of other shoulder portions  50 .  
         [0020]     In addition to securing or contributing to securing the flexible portion or portions of the substrate  45 , the holder  35  may perform various other functions in accordance with requirements of the particular application in which the instrument  10  is used. For example, the holder  35  may be fabricated from a diffuse or translucent material, such as an acrylic plastic material. In this way, the holder  35  may serve as a diffuser to the light source  15 , controlling its spatial distribution. In addition, the holder  35  may serve as all or a part of a lensing assembly for broadening or narrowing the illumination range of the light source  15 . For example, the holder  35  may itself form all or a portion of one or more lenses, or may have one or more lenses embedded therein. In addition, according to various embodiments, the holder  35  may be substantially transparent.  
         [0021]     As shown in  FIG. 3 , the backer  40  may exhibit a planar geometry and define an aperture  60  having an inwardly-tapered seating portion  65  disposed about the periphery thereof. According to various embodiments, the taper angle of the seating portion  65  is equal to, or substantially equal to, the taper angle θ T  of the shoulder portions  50 . The taper angle θ T  may also represent the illumination angle of the light source  15 . When the instrument  10  is assembled, the each shoulder portion  50  may be received onto the seating portion  65  such that a gap  67  is defined therebetween. For an inwardly-shifted shoulder portion  50  (see  FIG. 2 ), the corresponding gap  67  exhibits a greater width w than the of non-shifted shoulder portions  50 . As discussed below in connection with  FIG. 7 , the amount d by which a particular shoulder portion  50  is shifted (and thus the width w of the corresponding gap) may be determined based upon the dimensions of components (e.g., LEDs) disposed between holder  35  and the backer  40  when the instrument  10  is assembled.  
         [0022]     The backer  40  may generally be fabricated using any suitable plastic or metal material (e.g., Delrin, aluminum). Although the backer  40  is shown as a separate component in the illustrated embodiments, it will be appreciated that in other embodiments the backer  40  may instead be integrally formed as a feature of the chassis  25  ( FIG. 5 ). According to various embodiments, the backer  40  may be formed from a material having good heat-dissipating properties. In this way, the backer  40  may serve as a heat sink for the substrate  45 .  
         [0023]     The substrate  45  may be fabricated from any material suitable for use in flexible circuit applications, such as, for example, Kapton® Polyimide film available from DuPont, and comprise a circuit pattern  70  formed thereon using conventional circuit printing techniques. Such flexible substrates are commercially available from a number of manufacturers, such as, for example, GC Aero of Torrance, CA. As shown in  FIG. 4 , the substrate  45  may define an aperture  75  and comprise a plurality of flexible portions  80  extending inwardly toward the center of the aperture  75 . One or more of the flexible portions  80  may comprise at least one light-emitting diode  85  (LED) attached thereto via corresponding electrical mounting pads  90 . The mounting pads  90  may be integrally formed as a part of the circuit pattern  70 . For purposes of clarity, the LEDs  85  are not shown in  FIG. 4 .  
         [0024]     Although the substrate  45  is depicted as comprising sixteen (16) flexible portions  80  arranged in alternating pairs, it will be appreciated by one skilled in the art that the substrate  45  may comprise any number and arrangement of the flexible portions  80 . According to various embodiments, the LEDs  85  may be of a surface-mount (SMT) design and configured for attachment using, for example, an IR reflow process. It will be appreciated that the LEDs  85  may emit identical or different frequencies of light (visible and/or non-visible) depending upon factors such as, for example, the particular type of instrument  10  and the application in which it is used. Such factors may also determine the number of LEDs  85  attached to each finger portion  80 .  
         [0025]     The chassis  25 , according to various embodiments, may be fabricated from aluminum or other suitable material and comprise mounting surfaces  95 ,  100  to which the light source  15  and the sensor assembly  20  are respectively attached. As shown in  FIG. 5 , the mounting surface  95  may be recessed and suitably contoured such that the backer  40  may be received thereon. Receipt of the backer  40  onto the mounting surface  95  is shown in  FIG. 6 . The mounting surface  95  may define an aperture  100  through which light reflected from the specimen  30  may be passed to the light sensor assembly  20 . It will be appreciated that the chassis  25  may be configured for use with a hand-held instrument  10  or with a machine-operated instrument  10 .  
         [0026]      FIG. 7  illustrates a bottom view of the chassis  25  having the backer  40 , the flexible substrate  45 , and the holder  35  installed thereon according to various embodiments. For purposes of clarity, the LEDs  85  and the nose portion  47  are omitted. The flexible substrate  45  is disposed between the holder  35  and the backer  40  such that receipt of the holder  35  onto the backer  40  causes the deflection of the flexible portions  80  relative to a plane (A-A) of the flexible substrate  45 . In particular, each finger portion  80  and the LEDs  85  mounted thereon are deflected at an angle determined by the taper angle θ T  of the shoulder portions  50  and the backer  40 . As shown, the configuration of the substrate  45  and the holder  35  is such that two adjacent flexible portions  80  are deflected by each shoulder portion  80 . It will be appreciated, however, that the substrate  45  and the holder  35  may be configured such that more or fewer flexible portions  80  are deflected by each shoulder portion  50 . As noted above in connection with FIG.  2 , the taper angle θ T  of one or more of the shoulder portions  50  may be different from that of other shoulder portions  50 . Accordingly, the flexible portions  80  and their corresponding LEDs  85  may be deflected at different angles relative to other flexible portions  80  and their corresponding LEDs  85 . Furthermore, because the gap between each shoulder portion  50  and the backer  40  may be varied by shifting the shoulder portion  50  as described above, each flexible portion  80  may accommodate LEDs  85  having dimensions (e.g., height) different from those of other flexible portions  80 . Advantageously, the small profile of the light source  15  enables it to be positioned closer to the specimen  30 , thus allowing the size of the instrument  10  to be condensed.  
         [0027]      FIG. 8  illustrates the dependence of illumination angle upon the deflection of the flexible portions  80  and their corresponding LEDs  85  according to various embodiments. For a taper angle θ T  of the shoulder portions  50  and the seating portion  65 , the flexible portions  80  (and thus the optical axis of their corresponding LED  85 ) are rotated inward by an angle θ T  relative to the plane A-A of the flexible substrate  45 . Accordingly, where the orientation of the optical instrument  10  is such that the plane A-A of the flexible substrate  45  is generally parallel with the surface of the specimen  30 , the emitted light will illuminate the specimen  30  at an angle θ T.  Accordingly, the angle by which emitted light illuminates the specimen  30  is determined by the deflection angle of the substrate  45  relative to the specimen  30 , which is, as shown, determined by the taper angle θ T  of the holder  35  and the backer  40 .  
         [0028]     According to various embodiments, the deflection of the flexible portions  80  may be determined in various other ways. For example, the holder  35  may be omitted. In this case, the flexible portions  80  may be secured to the backer  40 , or the seating portion  65  by any suitable method including, for example, glue, adhesive, etc. According to various embodiments, the flexible portions  80  may be secured to the backer  40  by mechanical means. For example, a frame may extend from the backer  40  to secure the flexible portions  80 . Alternatively, other mechanical devices may be used including, for example, clips, hooks, slots in the backer  40 , etc. Also, according to various embodiments, the backer  40  may be omitted and the flexible portions  80  of the substrate  45  may be secured to the holder  35 , for example, using any of the means described above.  
         [0029]     It will be appreciated that the illumination angle of light emitted from the light source  15  is easily varied by suitably modifying the taper angle θ T  of the shoulder portions  50  and the seating portion  65 . The ability to vary the illumination angle in this fashion is particularly advantageous during design and development phases of the instrument  10 . In particular, because the holder  35  and the backer  40  may be quickly interchanged or modified to provide the desired taper angle θ T,  the time and expense required for development iterations (e.g., prototyping and testing) is substantially reduced. Additionally, because only minimal component modifications are necessary for adapting the light source  15  for use in a variety of instruments  10  having different illumination angle requirements, design and manufacturing costs are significantly reduced. Design and manufacturing costs are further reduced by the use of conventional components (e.g., flex circuit material, SMT LEDs) and conventional circuit population techniques for light source  15  fabrication.  
         [0030]     Although the embodiments shown illustrate the light source  15  as ring-shaped, it will be appreciated that the general principles disclosed herein may be applicable to non-ring-shaped light sources also. For example, one or more flexible portions may be arranged linearly, forming a line-shaped light source  15 . The lineary flexible portion or portions may be deflected, for example, as described above.  
         [0031]     It will be appreciated by one skilled in the art that uses of the light source  15  are not limited to the above-described instrumentation. In particular, it will be appreciated that the light source  15  may be suitably adapted for use in any lighting application in which it is desirable to adjust the illumination angle quickly and with minimal expense. Such applications may include not only instrumentation-related lighting applications, but also general lighting applications (e.g., residential, commercial, or industrial lighting applications).  
         [0032]     Whereas particular embodiments of the invention have been described herein for the purpose of illustrating the invention and not for the purpose of limiting the same, it will be appreciated by those of ordinary skill in the art that numerous variations of the details, materials, configurations and arrangement of components may be made within the principle and scope of the invention without departing from the spirit of the invention. The preceding description, therefore, is not meant to limit the scope of the invention.