Title of Invention

"A REFLECTOMETER"

Abstract

A pulsating light source emits light to illuminate a target surface which possesses a certain color and shade of color. Light that is reflected from the target surface is detected by an optical detector. An output from the optical detector is differentially amplified to compensate for any shift caused by ambient light, temperature or other external factors, and generate an output signal indicative of the color and shade of the target surface. The output signal from the differential amplifier is then rectified by a synchronous detector to produce a substantially steady DC voltage that is indicative of the color or shade of color at the target surface. Where the target surface color shade is indicative of a certain measurable quantity or quality (such as an analyte concentration) , the steady DC voltage is converted using a look-up table into a corresponding quantity or quality measurement. In performing this conversion/ compensation is made for any variations in pulsating light source intensity due to temperature change.

Full Text

The present invention relates to a reflectometer. BACKGROUND OF THE INVENTION This application for patent claims priority from U.S. Provisional Application for Patent Serial No. 60/063,935, filed October 31, 1998, and entitled "Reflectance-Type Glucose Meter." Technical Field of the Invention The present invention relates to reflectometer technology and, in particular, to a method and apparatus for detecting and measuring color shades with a relatively high degree of accuracy. Where the color shades are indicative of a certain measurable quantity or quality, the present invention further relates to method and apparatus for converting the detected color shade into a corresponding quantity or quality measurement. Description of Related Art presently, the only approved method for home monitoring of blood chemistry requires drawing blood by using a lance, usually sticking a finger and placing a drop of blood on a chemical strip that is read by a desk- top reflectance meter. Diabetics who need to control their insulin level via diet or insulin injection may test themselves five or six times per day, the frequency recommended by the American Diabetes Association. Some may choose to test less often than recommended to avoid the unpleasantness associated with drawing blood. Another method that also requires drawing blood utilizes the electrical response of the blood on a disposable PC Board. Some attempts to use infrared techniques to look through the skin have proven to be leas reliable and too expensive for commercial application. One technology which has demonstrated accurate and repeatable results employs a transdermal patch and a delivery medium to transport chemistry relative to blood glucose levels found in interstitial fluid to a sensitive membrane that contains a chemical or biological reaction that results in slight color changes in the patch which can be related to glucose levels. One such patch apparatus is disclosed by Peck (Patent # 4,821,733), which patent disclosure is incorporated herein by reference. Another patch that provides a color change within a short time period has been developed by Technical Chemicals & Products, Inc. (TCPI) as disclosed in U.S. Application for Patent Serial No. OS/ , filed September 11, 1997. An ultra-sensitive meter that can resolve the full range from the subtle color changes in a transdermal patch is the subject of the present invention. Beyond the obvious requirements for improved sensitivity, the meter is affected by the factors that are related to the portability of a hand-held device. These factors include background light changes, temperature changes, and unsteady hand-held operation not normally associated with the desk-top meters that are widely employed for measuring blood. The transdermal patch is applied to the skin, and after an incubation period of about 5 minutes, a protective cover is removed and the outside of the patch1a color-sensitive membrane is exposed. The meter ia then held against the patch at a controlled distance from the membrane. After a few seconds, the meter of the present invention displays the glucose level on an LCD display. Effects of pressure variation, rotation, and movement are minimized by the device's detection algorithm. SUMMARY OF THE INVENTION The present invention comprises reflectometer for detecting and measuring subtle changes in color and shade of color. In general, a pulsating light source illuminates a target surface which possesses a. certain color and shade of color. An optical detection circuit synchronously detects light that is reflected from the target surface and generates an output signal whose voltage is indicative of the color and shade of the target surface. This voltage is then processed to make an evaluation and identification of any measurable quantity or quality that ie represented by the detected color or shade of color. More specifically, a pulsating light source emits light to illuminate the colored target surface, where the specific color or shade of color ie indicative of a certain measurable quantity or quality (such as an analyte concentration). Light that is reflected from the target surface ie detected by an optical detector. An output signal from the optical detector is then processed and fed back to the optical detector to compensate for any shift cauaed by ambient light. The output signal from the optical detector is further differentially amplified to produce an AC output signal indicative of the color and shade of the target surface. The output signal from the differential amplifier is then rectified by a synchronous detector to produce a substantially steady DC voltage that is indicative of the color or shade of color at the target surface. This DC voltage is converted to a corresponding digital value, and that digital value is converted using a look-up table into a corresponding quantity or quality measurement. It is an object of the invention to have a highly sensitive reflectance meter capable of resolving aubtlc color differences for monitoring body chemistry. It is another object of this invention to eliminate the effects of ambient light on the reflectance measurement. It is a further object to incorporate the features of this invention into a hand-held device that is substantially unaffected by movement, rotation, or differences in contact pressure. It is another object of this invention to compensate the reading for temperature changes imposed by both ambient conditions and by induced temperature effects of the light source. It is yet another object of this invention to make practical a completely non-invasive glucose-measurement system for home and personal use. Accordingly, the present invention relates to a reflectometer, comprising: a pulsating light source for emitting light to illuminate a target surface which possesses a certain color and shade of color; an optical detector for detecting light that is reflected from the target surface and generating a first output, signal indicative of detected light; means for processing the first output signal to generate a feedback signal for application to the optical detector to compensate for any shift in the first output signal resulting from the detection of ambient light by the optical detector; and a detector for synchronously rectifying the second output signal to generate a steady DC output voltage that is indicative of the color or shade of color at the target surface. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS A more complete understanding of the method and apparatus of the present invention may be acquired by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein: FIG 1 is a cross-section of the sensor portion of the meter; FIG 2 is a drawing of a hand held meter of the present invention; FIG 3 is the detection circuit diagram ,- PIG 4 is a flow diagram of the entire meter circuit; FIG 5 is the meter control and display circuit diagram; FIG 6 is an LED temperature compensation circuit schematic; FIG 7 is a graphic diagram describing the detection algorithm of the present invention; and FIO 8 is a cross-sectional view of the detection window section. DETAILED DESCRIPTION OF THE DRAWINGS The sensor (Figure 1) contains a dual light source to increase the reflective signal strength and to uniformly illuminate the target surface. Two LED's 1 and 2 are mounted in a housing 3 at an angle to the normal. The LED's have a narrow fifteen degree projection angle. A photo transistor 4 is mounted to the housing normal to the target surface 5 of a transdermal patch 6, and has a narrow view angle. This symmetrical arrangement minimizes specular reflection and reduces the effect o£ rotational error that can occur from a slightly uneven color. The LED's are preferably attached to the printed circuit board 9 so that they can be adjuated wichin the LED cavity 10 within the housing 3. A pre-calibration is made when the LED'a are adjusted, the LED current is set, and the meter is calibrated to a color standard. The outer housing 11 ia constructed to have a thin cylindrical section 12 that can be docked with the patch to ensure alignment to the colored membrane surface 5. The housing is constructed with a low-expansion plastic such as Ryton, preferably with a non-reflective surface, and should be of a dark color {brown or black) to substantially eliminate any background signal from the housing's reflection. The meter (Figure 2} includes a sensor section 12 on one end of a semi-cylindrical case 13 that can be comfortably held in one hand. A "READ" button 14 activates the detection circuit, described below. Two key switches, a "SCROLL" button 15 and the "SELECT" button 16, are located on the face of the meter. An LCD display 17 provides a digital reading of the level. The display also has a real-time clock function that can be programmed by using the SCROLL and SELECT buttons to set the time-of-day and to set alarms to alert the user to take a reading , and to allow the user to select a manufacturing batch code of the tranadermal patch. A battery compartment 18 is located in the top end of the meter. Within the battery compartment is a data-port so that the user can connect to a computer or a telephone line to relay readings to a doctor or a clinic. The present invention will be better understood by presentation of the following example of its use with a transdermal patch, such as that manufactured by TCPI (see, U.S. Application Serial No. 08 ), in particular but not restricted to the detection of glucose in interstitial fluid related to blood levels. The patch requires, for example, a five-minute incubation period once in contact with the skin. Once the patch is attached to the skin, for example, on the inside of the forearm, the SELECT button is is pressed, starting a count-down. After five minutes, an audible alarm 19 alerts the user to connect the docking portion of the sensor section 12 to the patch 6 and take a reading by pressing the "READ" button 14. The READ button activates the detection circuit, and a detection routine measures the peak hold output signal in three to four seconds. The signal is converted to a level and displayed on the LCD 17. The glucose concentration is determined by measuring the reflectivity of the transdermal patch when exposed to light emitted by the high intenaity red LBDs l and 2. Light obtained from a pair of light emitting diodes 1 and 2 is generated with, for example, a 37 Hertz square wave of controlled current. The exact frequency is not critical, except that it should not be harmonically related to the main power line frequency, 60 Hertz in the United States or 50 Hertz in countries which use 50 Hertz. Referring to Figure 3, the pulsating light is detected by the photo transistor Q4 connected to a second transistor Q3 (not a photo transistor) with similar characteristics in a differential configuration. The output from one of the transistors is buffered and compared to a B.C. reference level and filtered by an integrator to provide a D.C. voltage. This voltage is proportional to the error between the desired quiescent operating point and the shift caused by ambient light, temperature, and other outside factors that would shift the operating point and otherwise result in measurement errors. This "feedback" voltage is applied to the base of the photo transistor Q4 to bias it back to the desired operating point. The output from the second transistor 03 of the differential amplifier, and the buffered output from the first transistor Q4, are fed to an operational amplifier U2D where they are differentially amplified and then full-wave-detected by a synchronous detector U2C, U3A, U3C. The synchronous detector which is phase-locked to the drive frequency of the LED's 1 and 1 via a phase inverter U3B ensures that the measured signal is accurately proportional to the reflected light from the target surface. The output from the synchronous detector is then filtered by a first order low pass filter R15 and C6, which smooths it before it is passed to an Analog-to-Digital converter and finally to a microprocessor. Diode D4 is important to establish a separate D.C. reference for the synchronous detector and also a reference for the analog output. The detection circuit output D.C. voltage of Figure 3 is input to the meter control circuit illustrated by Figure 5. The microprocessor 21, shown in its relationship to the circuit function in Figure 4, is programmed to process the detection circuit output D.C. voltage together with the measured ambient temperature signal to calculate a compensated voltage that directly relates to the reflectance off the target membrane surface at standard conditions. The microprocessor, by use of a lookup table related to the process batch characteristics, then calculates the glucose concentrations and then drives the display to present the reading for viewing by the user. The microprocessor aleo stores the reading date and time for future reference. In addition to the above functions, the microproceeaor is programmed to alert the user via alarm signals when the test should be made and provides other time functions that obviate the need for the user to have a separate clock. Control of the device is accomplished by providing switches and buttons with the following functions: READ, 14, SCROLL, 15, and SELECT (parameter entry), 16. A detailed understanding of the circuit is presented by reference to Figures 3 and 4. U4 is an astable square wave oscillator with sufficient power to drive two LED'a Dl and D2 connected in series. R17 and R18 are used to control the LEDs1 current and hence the light output. Q3 and photo transistor Q4 are connected in a differential configuration. Transistor pair Ql is a current mirror configuration to assure a stable and appropriate quiescent operating point for the differential pair Q3-Q4. Operational amplifier U2A ia configured as a unity gain, non-inverting buffer for the voltage output from Q3. U2B is an operational amplifier configured as an integrator. The buffered output of U2A ie compared to the D.C. voltage derived from the divider R8 and R9. The D.C. output voltage from U2B is converted to a current: by R6 which is then used to adjust the base current of Q4 to restore the desired operating point of the differential pair detector Q3-Q4. U2D is an operational amplifier that is connected in a differential configuration to amplify the output signals from Q3-Q4. The output of U2D is A.C. coupled via C4 to the synchronous detector 19 comprised of U2C, U3A and U3C. The full-wave-rectified output of U2C is fed to a low-pass filter RIB, C6. The smoothed signal is then directed to the A/D converter, which may be incorporated into the microprocessor or may be a separate device followed by a microprocessor. Figure 5 depicts the display circuit of the Mater. 175 is the display driver that can be integrated with a microprocessor/ Figure 4, or communicate with a computer as shown in Figure 5. SI is an on/off switch which powers the circuits of Figure 3 is previously deecribed as the READ button. Power is always available to the microprocessor which incorporates the clock and timing circuit. Switches S2 and S3 provide the logic levels to the microprocessor 21 or computer. Ui is a three-terminal Voltage Regulator that ensures a stable operating voltage to the meter. The output of the LED's is affected by ambient temperature - as temperature increases, the light output decreases - and the meter compensates for that effect. Referring again to Figure 1 and circuit diagram Figure 3, diode 7 or D3 is embedded in the housing adjacent to one of the LED's, and is used as a temperature sensor to compensate for the LED light output changing with temperature. A diode used as a temperature sensor can translate into a voltage that can be defined by temperature. For example, the voltage drop of a small signal diode 1N4148 is measured to be 0.0021 volts/degrees, C, a forward voltage drop is set by adjusting the series potentiometer R19, to .609 volts at twenty-five degrees C. The temperature effect of the light intensity varies with the detection signal nearly linearly. For example, at zero reflectance, there is no effect on the reflectivity. The reflectance temperature effect is thus expressed as a factor of the signal. A plot of the temperature error in volts versus the reflectance revealo a straight line that intersects the origin and has a slope of .0035 volts/degrees C. The compensation voltage is .0035 X Signal Voltage X Temperature change from twenty-five degrees C. Using the signal diode 7 described above, the compensated voltage becomes Signal -.00375 X Signal (diode voltage -.609)/.0021 or S{1-1.66( V -.609)) Alternately, direct compensation for the diminished light output can be accomplished with one or two diodes 8 adjacent to an LED and electronically in series with the LED's. Referring to Figure 6, this method can be used to directly compensate for temperature. The voltage drop of the series diodes with increasing temperature increases the current to the LED's, compensating for diminished light output with increasing temperature. For this series diode compensation it is preferable to use a germanium or Schottky diode since the low forward voltage drop of these types is an advantage in controlling the sensitivity of the light-adjusting potentiometer R18. In the manner already described, the detector circuit is substantially immune to the external influence of light, induced noise, and temperature. The aforementioned docking portion 12 of the meter need not necessarily provide a tight fit with the patch because leakage of ambient light, just like skin color, is compensated for by the synchronous detection feature of the circuit. Internally, the alternating nature of the light source and detector circuit avoids polarization and is not subject to D.C. drift. The high brightneae LED light source does have a Temperature Coefficient that is relative to the current. Two methods for correcting and compensating for the LED's have been described in detail. There are other factors that can affect accuracy: the technique of taking a reading, in particular, unsteady operation; motion while taking a reading; and varying contact pressure as the meter interfaces with the patch. In a hand-held meter, the routine to measure a repeatable peak hold must be tolerant of vibrations and unsteady operation. Data is sampled at a high enough rate to use many data points as input to an averaging routine. The sample rate is preferably not coincident with 50 Hz or 60 Hz or any harmonic thereof to minimize conducted or emitted line noise effects. The averaging technique should be able to determine the correct reading within a few seconds and not be affected however by the time to take a reading. The peak detection voltage stability is considered in order to arrive at a repeatable result. If, for example, the detection voltage range is between .5 and .8 volts, then a peak detection voltage stability of .002 volts would provide for better than 1% resolution. A signal gain of 5 would result in a range of 2.5 to 4 volts, a range that is more compatible with a microprocessor having an analog to digital converter with 5 volt supply. In this case, a stability of .01 volts is sufficient for 1% resolution. Figure 7 illustrate the peak hold detection algorithm used in the present example. In this example, the Sampling Rate (number) samples raw data per second is 200.0, the Average Sample Rate (number) averages per second is 20.0, the Moving Average Window Size (seconds) is 1.0; the Peak Detection Window Size (seconds) is 0.5; and the Peak Hold Deviation (volts) is 0.002. Raw data is collected at [200] samples per second. A Moving Average is calculated for the last [one second] or last 200 data points. The Moving average is tabulated every [l/20th] of a second and compared to the last 10 tabulated Moving averages (.5 seconds). If the deviation is less than [.002] volts during the peak window period, then a steady state condition has been satisfied, and the laet moving average becomes the Peak value. This Peak value is not actually the highest recording, it is the eteady state value after a minimum 1 second data collection period. According to the data collection example of Figure 7, if all of the Average data blocks between Vav23 and Vav32 are within .002 volts than the steady state value is equal to V32. A low limit voltage of .200 volts is chosen as a trigger value to begin collecting data, the first raw data value above the low limit is VI. Errors are defined if the final peak hold steady state value is below or above the expected range, or if a value is not obtained after a pre-determined time, for example, 6 seconds. With this routine, the normal detection time is 3 seconds even when an unsteady or imperfect technique is employed. The last peak value is corrected for temperature and the resolved value is compared to a lookup table that correlates a voltage to a mg/dL equivalent. If the value is between two lookup rows, the final reading is interpolated. This, method will accurately convert a nonlinear relationship between reflectance and mg/dL glucose. The lookup table is selected according to the batch code of the patch. Other factors that may affect the calibration to an individual can also be effected by the choice of the lookup table. An example lookup table is illustrated in Table 1. TABLE 2 mV (Table Removed) The invention is presented for full understanding by the following example: At 10:00 AM, a pre-set audible alarm alerts the diabetic user to take a glucose reading. A transdermal patch is attached to the inside of the user's forearm and the SELECT button is pressed, signaling the beginning of a five minute countdown. After five minutes another audible alarm having a distinct tone sequence alerts the user that it is time to read the patch. The sensor section is coupled to the patch in the manner already described and the READ button is pushed, activating the light source and the detection circuit. After one second the detector circuit output voltage is hovering around .660 volts and after 2 seconds the peak-hold stable voltage is obtained and a value of .664 volts is presented to the microprocessor for analysis. In addition, the temperature seneor diode inputs a value of .611 volta. According to the correction algorithm [R= S (1-1.66(.611-.609) ] the corrected reading is .662 volts. According to the lookup table the glucose level is between 140 and 180 mg/dL. The interpolated result is 170.4 mg/dL. When rounded to a 1 mg/dL resolution, the final result is 170 mg/dL and is displayed on the LCD. The result is also stored in memory along with the date and time for future reference or to be downloaded to a computer as patient history. After one minute, the display reverts back to the time of day and the program anticipates the next pre-set alarm. Between alarms other measurements can be initiated by pressing the SELECT button to go into countdown mode. During the five-minute countdown mode, the display will show the time with the colon symbol on continuously in lieu of its normal once-per-second blinking. ALTERNATE EMBODIMENT With the meter docked to the transdermal patch the window portion of the sensor section ia open to both the light source and the photo detector. Accurate measurement is dependent upon the target surface being in position. Figure 8b shows the deflection of the target surface with varying levels of applied force: light, medium, and very hard. It hag been observed that the result of increasing presaure applied to the patch by the meter causes an increased reflectance signal due to the target surface deflecting toward the photo detector. In addition/ the target surface may not be completely flat. This also can cause an error unrelated to the chemical reaction color change. Figure 8a shows the mechanical effect with increasing pressure when a transparent window is used. The window 22 constrains the flexible membrane 5 and fixes the position of the target. The transparent window is preferably made of a plastic that exhibits a high transmissivity at the wavelength of the source light used, in this case, that wavelength emitted by the red LEDs. Additional requirements include durability and resistance to cleaning solutions. The clear window should prevent dirt and dust from accumulating within the sensor cavities which could reduce the sensitivity and might also effect the calibration. This invention is presented as a hand-held non-invasive glucose measuring device although the scope is noc limited to this embodiment. The advantages can be applied to regular strip-meters to improve their accuracy and sensitivity, or to any reflectance device that requires the high degree of resolution, repeatability, and accuracy demonstrated by this invention. Although preferred embodiments of the method and apparatus of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims. WE CLAIM: 1. A reflectometer, comprising: a pulsating light source for emitting light to illuminate a target surface which possesses a certain color and shade of color; an optical detector for detecting light that is reflected from the target surface and generating a first output, signal indicative of detected light; means for processing the first output signal to generate a feedback signal for application to the optical detector to compensate for any shift in the first output signal resulting from the detection of ambient light by the optical detector; and a detector for synchronously rectifying the second output signal to generate a steady DC output voltage that is indicative of the color or shade of color at the target surface. 2. The reflectometer as claimed in claim 1, wherein the pulsating light source emits light having an intensity that varies with changes in temperature, the reflectometer comprising: a temperature sensor thermo-mechanically coupled to the pulsating light source, the sensor generating a third output signal indicative of temperature near the pulsating light source; and means for correcting the steady output voltage in accordance with the third output signal to account for detected changes in pulsating light source temperature. 3. The reflectometer as claimed in claim 2, wherein the pulsating light source comprises at least one light emitting diode, and wherein the temperature sensor comprises a diode. 4. The reflectometer as claimed in claim 1, wherein the pulsating light source emits light having an intensity that varies with changes in ambient temperature, the reflectometer comprising: a temperature sensor thermo-mechanically coupled to the pulsating light source; and means for having the temperature sensor control operation of the pulsating light source to counteract for any variations in light intensity due to changes in ambient temperature. 5. The reflectometer as claimed in claim 4, wherein the pulsating light source comprises one light emitting diode, wherein the temperature sensor comprises a diode, and wherein the means for having comprises a series electrical connection of the diode with the light emitting diode. 6. The reflectometer as claimed in claim 1 wherein the optical detector comprises: a photo transistor for receiving and detecting light that is reflected from the target surface and generating a first differential signal; a transistor for setting the quiescent operating point and generating a second differential signal; and means for differentially connecting the photo transistor and transistor at a common emitter connection. 7. The reflectometer as claimed in claim 6, comprising a current mirror for supplying fixed constant current into the common emitter connection between the photo transistor and transistor. 8. The reflectometer as claimed in claim 6, wherein the means for processing operates to process the second differential signal to generate the feedback signal for application to the photo transistor to bias the photo transistor to the quiescent operating point. 9. The reflectometer as claimed in claim 8, wherein the means for processing comprises an integrator for comparing the second differential signal to a reference voltage and integrating a result of the comparison to generate the feedback signal, wherein the feedback signal is indicative of an error between the quiescent operating point and a shift caused by ambient light detected at the photo transistor. 10. The reflectometer as claimed in claim 1, wherein the pulsating light source comprises: two light emitting diodes; and means for mounting the light emitting diodes each at an orientation angle away from an orientation angle of the optical detector so as to provide for uniform illumination of the target surface with minimal specular reflection to the optical detector. 11. The reflectometer as claimed in claim 1 wherein the target surface comprises a color developing membrane of a transdermal patch, and the reflectometer has a reader head adapted for mating with the color developing membrane of the transdermal patch. 12. The reflectometer as claimed in claim 11, wherein the reader head has a transparent window for flattening the color developing membrane when the reader head mates with the color developing membrane. 13. The reflectometer as claimed in claim 1 wherein the target surface color shade is indicative of a certain measurable quantity or quality, the reflectometer comprising a processor for converting the steady DC voltage indicative of the color or shade of color at the target surface into a corresponding quantity or quality measurement. 14. The reflectometer as claimed in claim 13, comprising a look-up table correlating steady DC voltage value to corresponding quantity or quality measurements, the processor consulting the look-up table in making its conversion. 15. The reflectometer as claimed in claim 14, wherein the measurable quantity or quality comprises an analyte concentration. 16. The reflectometer as claimed in claim 15, wherein the analyte concentration comprises either glucose level or cholesterol level. 17. The reflectometer as claimed in claim 1, wherein the pulsating light source emits light having an intensity that varies with changes in temperature, and wherein the target surface color shade is indicative of a certain measurable quantity or quality, the reflectometer comprising: a temperature sensor thermo-mechanically coupled to the pulsating light source, the sensor generating a temperature indicative signal; and a processor for adjusting the steady DC voltage indicative of the color or shade of color at the target surface in accordance with the temperature indicative signal to generate a compensated DC voltage, and for converting the compensated DC voltage into a corresponding quantity or quality measurement. 18. A reflectometer as claimed in claim 11, wherein the reader head comprises: two light emitting diodes; an optical detector; and means for mounting the light emitting diodes each at 5 an orientation offset angled away from an orientation of the optical detector so as to provide for substantially uniform illumination of a target surface with minimal specular reflection to the optical detector. 19. A reflectometer as claimed in claim 18, wherein said optical detector is oriented normal to the target surface. 20. A reflectometer as claimed in claim 18, wherein offset angle is between forty and forty-five degrees. 21. A reflectometer as claimed in claim 18, wherein the target surf ace comprises a color developing membrane of a transdermal patch, and the reader head is adapted for mating with the color developing membrane of the transdermal patch. 22. A reflectometer as claimed in claim 18, wherein the said reader head has a transparent window for flattening the color developing membrane when the reader head mates with the color developing membrane. 23. A reflectometer, substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

3205-del-1998-abstract.pdf

3205-del-1998-claims.pdf

3205-del-1998-correspondence-others.pdf

3205-del-1998-correspondence-po.pdf

3205-del-1998-description (complete).pdf

3205-del-1998-drawings.pdf

3205-del-1998-form-1.pdf

3205-del-1998-form-13.pdf

3205-del-1998-form-19.pdf

3205-del-1998-form-2.pdf

3205-del-1998-form-4.pdf

3205-del-1998-form-6.pdf

3205-del-1998-gpa.pdf