Abstract:
A microscope ( 10 ) having an improved light source assembly ( 40 ) that provides sufficient illumination for sophisticated microscopic applications while requiring so little power that it may be operated with a small, rechargeable battery pack ( 46 ) that provides over 40 hours of continuous operation from a single charge. The light source assembly ( 40 ) has a bulb life of approximately 100,000 hours and operates at temperatures significantly below the operating temperatures of conventional microscope bulbs.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to microscopes and related instruments. More particularly, the invention relates to a cordless microscope with an improved light source assembly.  
           [0003]    2. Description of the Prior Art  
           [0004]    Microscopes are commonly used in laboratories, classrooms, and other applications and are considered to be among the most valuable scientific instruments ever invented. To permit magnified viewing of a specimen, a typical microscope requires that the specimen be illuminated. Microscopes are arranged either for transmitted illumination, where light is passed through the specimen, or for reflected illumination, where light bounces back from the specimen. Transmitted lighting is more usual today.  
           [0005]    Ambient or general purpose room lighting is typically not intense enough to provide the desired amount of specimen illumination; therefore, most microscopes include an electric lamp or other means of artificial illumination. Typically, the lamp is built into the base or stand of the microscope and is plugged into a conventional 120 volt AC outlet with an electrical cord. Unfortunately, such electrical cords cause several problems. For example, many laboratories and classrooms do not have an adequate number of available AC outlets in which to plug the cords. This necessitates the use of unsightly and bulky extension cords and multiple-outlet plug-in strips. Another problem is that researchers, students, and teachers often wish to move their microscopes from location to location, requiring the cords to be frequently unplugged and then replugged into new outlets. Microscopes with electrical cords also cannot be used outdoors and other locations where no AC electrical outlets are available.  
           [0006]    Cordless microscopes have been developed to address some of the above-identified concerns. Unfortunately, however, currently-available cordless microscopes suffer from several distinct disadvantages. For example, because sophisticated microscopes use relatively high-wattage bulbs to provide adequate specimen illumination, a quality cordless microscope either requires a large battery to power the bulb or has a very short operating life between battery charges. Some cordless microscopes solve this problem by using lower wattage bulbs. While these types of microscopes are adequate for use as toys, they do not provide adequate illumination for most scientific and educational applications.  
           [0007]    Another limitation of existing cordless microscopes, and all microscopes in general, is that they typically use tungsten, halogen, or fluorescent bulbs that generate a great deal of excess heat. Such heat may cause burns and may undesirably raise the temperature of any specimens placed in the vicinity thereof. The excess heat may be dissipated by fans, but this further increases the power requirements, cost, and complexity of the microscopes.  
           [0008]    Another limitation of existing cordless microscopes, and all microscopes in general, is that their bulbs frequently burn out and/or break and therefore must be replaced. This necessitates a partial dismantling of a microscope&#39;s base or stand to access, remove, and replace its bulb.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention solves the above-described problems and provides a distinct advance in the art of cordless microscopes and microscopes in general. More particularly, the present invention provides a microscope having an improved light source assembly that provides sufficient illumination for sophisticated microscopic applications while requiring so little power that it may be operated with a small, rechargeable battery pack that provides over 40 hours of continuous operation from a single charge. The light source assembly has a bulb life of approximately 100,000 hours and operates at temperatures significantly below the operating temperatures of conventional microscope bulbs.  
           [0010]    One embodiment of the light source assembly of the present invention broadly includes a circuit board, a plurality of Light Emitting Diodes (LEDs) mounted on the circuit board, and a connector configured for coupling with a rechargeable battery. The circuit board is preferably circular in shape and is coated with a reflective material to reflect light emitted from the LEDs. The circuit board fits within a circular opening in the base of a microscope and replaces a conventional microscope lamp.  
           [0011]    The LEDs have a highly-focused angle of illumination, operate at a high candle power, and generate optimum true white light to provide an illumination approximately equal to that of a conventional 20-watt bulb. Advantageously, the LEDs require much less power than conventional microscope bulbs and operate at a much lower temperature. The light source assembly of the present invention therefore needs no cooling fan and can be powered by a small battery pack that provides for approximately 40 hours of continuous operation from a single charge. The LEDs have a bulb life of approximately 100,000 hours and therefore may never need to be replaced. In the event that the LEDs require replacement, the entire light source assembly can be easily removed from the microscope and replaced with another similar or identical light source assembly.  
           [0012]    These and other important aspects of the present invention are described more fully in the detailed description below. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0013]    A preferred embodiment of the present invention is described in detail below with reference to the attached drawing figures, wherein:  
         [0014]    [0014]FIG. 1 is an isometric view broadly depicting a cordless microscope in which the principles of the present invention may be implemented.  
         [0015]    [0015]FIG. 2 is an exploded isometric view of the base of the microscope of FIG. 1.  
         [0016]    [0016]FIG. 3 is an electrical circuit diagram depicting certain components of the light source assembly of the cordless microscope.  
         [0017]    [0017]FIG. 4 is a top plan view of the light source assembly.  
         [0018]    [0018]FIG. 5 is an isometric view of reflective tube that may be used in certain embodiments of the cordless microscope. 
     
    
       [0019]    The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    Turning now to the drawing figures, and particularly FIG. 1, a cordless microscope  10  constructed in accordance with a preferred embodiment of the invention is illustrated. The cordless microscope  10  has many of the same components as conventional plug-in microscopes such as the T-1201 and T-1901 model microscopes manufactured and sold by Ken-A-Vision Manufacturing Co., Inc., of Kansas City, Mo. For example, the cordless microscope  10  preferably includes a conventional stand  12  having a base  14  which may be placed on a counter top or other level surface and an upstanding arm  16  supported on the base  14 . As illustrated in FIG. 2, the base  14  includes an upper section  18  and a lower section  20  that can be removably connected with screws or other conventional fasteners. The upper section  18  has a raised circular lamp holder  21  for receiving a light source as described below. The top of the lamp holder  21  defines a circular opening  22  for directing light out of the base  14  as described in more detail below.  
         [0021]    Returning to FIG. 1, the microscope  10  also includes a stage  24  supported by the arm  16  for holding specimens to be viewed. The stage  24  includes an opening  26  in approximate axial alignment with the circular opening  22  in the base  14 . As is conventional, specimens are placed on the stage  24  over the opening  26  so that light may pass through the specimens. The microscope  10  also includes one or more objective lenses  28  supported by the arm  16  above the stage  24  for magnifying images of specimens placed on the stage  24 . The objective lenses  28  may be mounted on a rotatable head  30  or carousel that allows certain ones of the lenses  28  to be selected for use.  
         [0022]    The microscope  10  also includes one or more eyepiece lenses  32  mounted on the arm  16  above the objective lenses  28  for providing further magnification of specimen images and for permitting a user to view the images. The eyepiece lenses  32  may also be mounted to a rotating head or carousel. The cordless microscope  10  also includes conventional controls mounted to the stand  12  such as course and fine coaxial focusing knobs  34 ,  36 .  
         [0023]    In accordance with one important aspect of the present invention, the microscope  10  also includes an improved light source assembly  40  illustrated in FIGS. 3 and 4 that replaces or is used instead of a conventional fluorescent, halogen, or tungsten light bulb. The preferred light source assembly  40  broadly includes a circuit board  42 , a plurality of LEDs D1, D2, D3, and D4 mounted on the circuit board  42 , a first connector  44  configured for connecting to a battery or battery pack  46 , a second connector  48  configured for connecting to an on/off switch  50 , and a third connector  52  configured for connecting to a battery recharger.  
         [0024]    The circuit board  42  is preferably a conventional printed circuit board that is cut or formed so that it fits snugly within the lamp holder  21  formed in the microscope base  14 . The top surface of the circuit board  42  is preferably coated with a highly reflective material such as tin to reflect light emitted from the LEDs upwardly toward a sample placed over the opening  26  in the stage  24 . For microscopes having a raised or elongated lamp holder, the circuit board  42  may be placed in an internally-reflective tube  56  illustrated in FIG. 5 which is then in turn placed in the raised lamp holder. Light emitted from the circuit board  42  is then reflected upwardly and off of the interior walls of the tube  56  and out through the opening of the lamp holder. A 28 mm white frosted filter is preferably positioned in the top of the lamp holder  21  to filter the light emitted from the LEDs toward the stage  24 .  
         [0025]    As best illustrated in FIG. 4, the LEDs D1, D2, D3, and D4 are arranged on the top surface of the circuit board  42  so as to project light upwardly toward a sample placed on the stage  24 . In preferred forms, the light source assembly  40  includes four LEDs positioned in the approximate center of the circuit board  42  and arranged in a substantially Y-shaped configuration.  
         [0026]    The LEDs have special operating characteristics that enhance and optimize the light output of the light source assembly  40 . For example, the LEDs have a highly-focused angle of illumination so that most of their generated light is projected upwardly toward the stage  24 , rather than sideways or down toward the circuit board  42 . It has been determined that the optimum angle of illumination is approximately 20 degrees. In contrast, conventional LEDs have a much less focused angle of illumination in the range of 80-180 degrees. Moreover, the LEDs emit a true white light, rather than a blue light as is conventional with LEDs, that provides superior sample illumination for microscopic applications. Further, each LED provides over 5,000 millicandellas (MCD) of illumination, but operates at a temperature less than 25 degrees C. Finally, each LED has a bulb life of approximately 100,000 hours. The preferred LEDs are supercool-white InGaN discrete model number L200CWGKB-22D LEDs manufactured by Ledtronics.  
         [0027]    Because the LEDs are arranged on a reflective coated circuit board  42 , have a highly-focused angle of illumination, operate at a high candle power, and generate optimum true white light, the light source assembly  40  provides illumination equivalent to a 20-watt bulb. Advantageously, however, the light source assembly  40  requires much less power than a conventional 20-watt bulb and operates at a much lower temperature. The light source assembly  40  therefore needs no cooling fan and can be powered by a small battery pack  46  as described below.  
         [0028]    The first connector  44  is preferably mounted on the circuit board  42  and is electrically connected with the LEDs so that it may be connected with the battery pack  46  for powering the LEDs. The connector  44  is preferably a three-pin, female-type jack terminal configured for coupling with a corresponding male-type pin connector  45  wired to the battery pack  46 . The preferred battery pack  46  is a four-battery Nickel Metal Hydride (NiMH) 4.8 volt 1500 mAH battery pack. Such a battery pack  46  is small enough to fit within the upper  18  and lower  20  sections of the microscope base  14 , yet is powerful enough to power the LEDs for forty hours of continuous illumination on a single charge. The battery pack  46  may be recharged with a conventional charger in approximately eight hours and has a life of approximately 500 recharging cycles.  
         [0029]    The second connector  48  is also preferably mounted on the circuit board  42  and is configured for connecting to the on/off switch  50  to switch the LEDs on and off. The on/off switch  50  is preferably mounted on the outside of the microscope stand  12  but may be mounted elsewhere as a matter of design choice. The second connector  48  is preferably a female-type, three-pin jack terminal configured for coupling with a corresponding male-type pin connector  49  wired to the on/off switch  50 .  
         [0030]    The third connector  52  is preferably mounted flush with the outside of the microscope stand  12  and is configured for coupling with a battery charger. The third connector  52  is preferably a two-pin, female-type jack terminal wired to the pin connector  49 . The preferred charger is a 9-volt DC, 300 mA charger such as the Calrad Model No. VFBT-757 charger.  
         [0031]    As illustrated in FIGS. 3 and 4, the LEDs are wired in parallel between the first pin of the second connector  48  and the second pin of the first connector  44 . Each LED is also preferably connected in series with a 68 ohm, 5 watt resistor R2, R3, R4, R5 for limiting the current flow therethrough. A 60 volt, 0.5 amp fuse is preferably wired between the first pin of the first connector  44  and the third pin of the second connector  48 . A 68 ohm, 5 watt resistor R1 is connected between the second pin of the first connector  44  and the second pin of the second connector  48  to regulate current delivery from the battery charger to the battery pack  46 . The connections between the various components on the circuit board are preferably printed directly on the circuit board with conductive foil material.  
         [0032]    To operate the light source assembly  40  and thus the microscope  10 , the first connector  44  is coupled with the pin connector  45  connected to the battery pack  46  and the second connector  58  is connected to the pin connector  49  connected to the on/off switch  50 . The on/off switch  50  may then be closed to switch power from the battery pack  46  to the LEDS so as to illuminate the LEDs. Light emitted from the LEDs is then directed upwardly through the circular opening  22  in the upper section  18  of the base  14  toward the stage  24  so as to illuminate any samples placed thereon. As discussed above, any light that is not initially directed upwardly from the LEDs reflects off of the reflective circuit board  42 , and in some embodiments the internally-reflective tube  56 , toward the stage  24 . The on/off switch  50  may be opened at any time to disconnect the battery pack  46  from the LEDs.  
         [0033]    When the battery pack  46  becomes discharged, a battery charger may be plugged into the third connector  52 . This automatically disconnects the LEDs from the battery pack  46  and begins charging the battery pack  46 .  
         [0034]    If any of the LEDs burn out, the entire light source assembly  40  can be easily removed and replaced with a new light source assembly by dismantling the microscope base  14  and disconnecting the first connector  44  from the pin connector  45  and the second connector  48  from the pin connector  49 . Because the LEDs and all other circuitry are mounted to the circuit board  42 , no further modifications are required to replace the light source assembly  40 .  
         [0035]    Although the invention has been described with reference to the preferred embodiment illustrated in the attached drawing figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims. For example, although the light source assembly of the present invention is especially suited for use with a cordless microscope, it may also be used with conventional microscopes that plug into a 120-volt AC power source. An analog to digital converter and other circuitry would be required for such an application.  
         [0036]    Having thus described the preferred embodiment of the invention, what is claimed as new and desired to be protected by Letters Patent includes the following: