Abstract:
A method of measuring a characteristic of a skin, including varying an air pressure in a chamber positioned adjacent to a skin, in which the chamber has an opening that exposes the skin to changes in the air pressure in the chamber. A plurality of measurements of surface profiles of the skin are made over a period of time as the surface profile of the skin varies in response to changes in the air pressure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional and claims the benefit of U.S. patent application Ser. No. 11/736,954, filed on Apr. 18, 2007, which claims the benefit of U.S. Provisional Patent Application 60/895,588, filed on Mar. 19, 2007. The above applications are incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    This invention relates to skin elasticity measurement. 
         [0003]    Mechanical properties of skin (e.g., elasticity of skin) may change due to, e.g., disease, stress, or dehydration. When the body becomes dehydrated as a result of diseases (e.g., ones that cause diarrhea) or reduced liquid intake (e.g., famine or marathon running), the skin becomes “doughy” and does not snap back when pinched. A fluid loss of 5% of the body weight is considered mild dehydration. A 10% loss is regarded as moderate dehydration, and 15% or more fluid loss is severe dehydration. For example, in a test for dehydration called the “pinch test” or “turgor test,” the skin is grasped and pulled up in a pinch-like manner and then release. Healthy skin will quickly snap back to its undeformed state, whereas dehydrated skin slowly returns to its undeformed state. 
       SUMMARY 
       [0004]    In one aspect, in general, a method of measuring a characteristic of a skin, the method including varying an air pressure in a chamber positioned adjacent to a skin, the chamber having an opening that exposes the skin to changes in the air pressure in the chamber, making a plurality of measurements of surface profiles of the skin over a period of time as the surface profile of the skin varies in response to changes in the air pressure, and outputting the measurements or a value derived from the measurements. 
         [0005]    Implementations of the method may include one or more of the following features. Measuring the surface profiles of the skin includes using a video camera to capture images of the surface profiles of the skin as the skin rises or falls in response to changes in the air pressure. The method includes providing an indication of a likelihood of dehydration of a person or an animal based on measurements of the surface profile of the skin. The method includes forming an air-tight coupling between the skin and a rim surrounding the opening. 
         [0006]    In another aspect, in general, a method includes varying an air pressure in a chamber positioned adjacent to a skin, the chamber having an opening that exposes the skin to changes in the air pressure in the chamber; making a plurality of measurements of a level of a surface of the skin over a period of time as the surface of the skin rises or falls in response to changes in the air pressure in the chamber; and using the plurality of measurements to determine an elasticity of the skin. 
         [0007]    Implementations of the method may include one or more of the following features. Measuring the level of the surface of the skin includes using a linear potential meter to measure the level of the surface of the skin. Measuring the level of the surface of the skin includes using a Hall sensor to measure a magnetic field generated by a magnet attached to the surface of the skin. 
         [0008]    In another aspect, in general, a method includes varying an air pressure in a first chamber positioned adjacent to a skin, the first chamber defining an opening that exposes the skin to changes in the air pressure in the chamber, making a plurality of measurements of a volume of the skin in the first chamber over a period of time as the volume of the skin in the first chamber changes in response to changes in the air pressure in the first chamber, and outputting the measurements or a value derived from the measurements. 
         [0009]    Implementations of the method may include one or more of the following features. The method includes varying a volume of a second chamber that is coupled to the first chamber to cause the air pressure in both the first and second chambers to vary over the period of time. Making a plurality of measurements of a volume of the skin in the first chamber includes making a plurality of measurements of the air pressure in the first and second chambers over the period of time as the air pressure changes in response to the variations in the volume of the second chamber, and determining the volume of the skin in the first chamber based on the measurements of the air pressure. 
         [0010]    An apparatus for measuring a characteristic of a skin, the apparatus includes a chamber to be positioned adjacent to a skin, the chamber having an opening that exposes the skin to changes in an air pressure in the chamber; a pump to vary the air pressure in the chamber; and a video camera to capture images of surface profiles of the skin in the chamber over a period of time as the surface profile of the skin changes in response to changes in the air pressure in the chamber. 
         [0011]    Implementations of the apparatus may include one or more of the following features. The apparatus includes a controller to control the pump and the video camera to capture images of surface profiles of the skin over a period of time. The apparatus includes a data processor to process captured image data and provide an indication of a likelihood of dehydration of a body based on a result of the processing of the image data. The chamber has an inner surface having a dark color to enhance a contrast between the skin and the inner surface of the chamber. The apparatus includes a vent valve to provide a passage between the chamber at the atmosphere. The chamber includes a cuvette. 
         [0012]    An apparatus for measuring a characteristic of a skin, the apparatus includes a chamber to be positioned adjacent to a skin, the chamber defining an opening that exposes the skin to changes in an air pressure in the chamber; a pump to vary the air pressure in the chamber; and a sensor to measure a level of a surface of the skin in the chamber over a period of time as the surface of the skin in the chamber rises or falls in response to changes in the air pressure in the chamber. 
         [0013]    Implementations of the apparatus may include one or more of the following features. The sensor includes a linear potential meter to measure the level of the surface of the skin. The sensor includes a Hall sensor to measure a magnetic field generated by a magnet attached to the surface of the skin. 
         [0014]    An apparatus for measuring a characteristic of a skin, the apparatus includes a first chamber to be positioned adjacent to a skin, the first chamber defining an opening that exposes the skin to changes in an air pressure in the first chamber; a second chamber having an adjustable volume and being coupled to the first chamber, the first and second chambers having a common air pressure; a pump to reduce an air pressure in the first and second chambers; a pressure sensor to sense the air pressure; and a data processor to determine a change in a volume of the skin in the first chamber based on measurements of the air pressure by the pressure sensor. 
         [0015]    Implementations of the apparatus may include one or more of the following features. The second chamber includes a motor and a syringe, the motor to drive a plunger of the syringe to change the volume in the second chamber. 
         [0016]    The apparatuses and methods can have one or more of the following advantages. The elasticity of a skin can be quickly measured, and information about skin elasticity can be used as a factor in evaluating whether a person or animal is dehydrated. The device for measuring skin elasticity is low cost, small, and convenient to carry. 
         [0017]    Other features and advantages of the invention are apparent from the following description, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0018]      FIG. 1  is a schematic diagram of a skin measurement system. 
           [0019]      FIG. 2  is a schematic diagram of a skin measuring system. 
           [0020]      FIG. 3  show images of skin surface profiles. 
           [0021]      FIG. 4  is a schematic diagram of a skin displacement measuring device. 
           [0022]      FIG. 5  is a schematic diagram of a skin displacement measuring device. 
           [0023]      FIG. 6  is a schematic diagram of a skin measuring system. 
       
    
    
     DESCRIPTION 
       [0024]    Mechanical properties of skin, such as elasticity of the skin, can be measured by applying a force to the skin and measuring how the skin responds to the force. For example, a suction force can be applied to pull the skin, and sensors can be used to measure the skin while the suction force is applied and/or after the suction force is removed. In some examples, a sensor may be used to determine the amount of time it takes for the skin to deform a certain amount when a given suction force is applied. In some examples, a sensor may be used to measure the profile of the skin over time as the skin returns its original state after the suction force is removed. 
         [0025]      FIG. 1  is a schematic diagram of a skin measuring system  100  for measuring mechanical properties of a skin  102 . the mechanical properties may include, e.g., an elasticity of the skin  102 . The system  100  includes skin displacement measuring device  104  that measures positions of the skin  102  as a suction force pulls on the skin  102  over a period of time. The device  104  includes a chamber  106 , which may be a cuvette, that is placed over the skin  102 . The device  104  is pressed against the skin  102  so that the skin  102  completely covers an opening  110  of the chamber  106 , preventing air from entering or leaving the chamber  106  through the opening  110 . The chamber  106  is coupled to a vacuum pump  112  through a tube  194 . As the vacuum pump  112  operates to reduce the air pressure in the chamber  106 , a suction force is generated on the skin  102 , pulling the skin  102  upwards into the chamber  106 . 
         [0026]    The system  100  includes a pressure sensor  114 , a vent solenoid  116 , and an adjustable vacuum relief valve  118  that are coupled to the tube  194 . The level of vacuum in the chamber  106  can be adjusted by adjusting vacuum relief valve  118  to control the amount of air entering the tube  194  through the valve  118 . The vent solenoid  116  when activated provides a passage between the tube  194  and the outside environment so that the pressure in the chamber  106  can quickly return to atmospheric pressure. 
         [0027]    The description below includes examples of skin elasticity measurement systems that use different methods for measuring the displacement of the skin  102 . 
       Example 1 
       [0028]      FIG. 2  is a schematic diagram of an example of a skin measuring system  120  for measuring mechanical properties of a skin  102 . The system  120  has a skin displacement measuring device  150  that includes a digital video camera  122  for capturing images of the skin surface profile  124  over a period of time. The system  120  includes a cuvette  126  that is pressed against the skin  102  during measurement. The cuvette  126  can have, e.g., a 10 mm×10 mm square cross section. The cuvette  126  has an opening  128  through which the skin  102  is partially pulled into the cuvette  126  in response to a reduction in the air pressure in the cuvette  126 . The system  120  includes a vacuum pump  112 , a pressure sensor  114 , a vent solenoid  116 , and an adjustable vacuum relief valve  118 , similar to those shown in  FIG. 1 . 
         [0029]    A light source, e.g., a red light emitting diode (LED)  130 , illuminates the skin  102  in the cuvette  126 . To provide a constant illumination, the LED  130  can be driven by, e.g., a 5 V voltage regulator connected to a 9 V battery. A resistor (not shown) in series with the LED  130  can be used to limit the current flowing through the LED  130  to, e.g., about 10 mA to allow the LED  130  to provide adequate illumination. 
         [0030]    The cuvette  126  can be made of, e.g., clear plastic. Both the inside and outside of the cuvette  126  are painted, e.g., matte black, except for a window  132  on a sidewall of the cuvette  126  near the opening  128 . Painting the inside and outside of the cuvette  126  matte black prevents reflections on the interior and exterior surfaces of the cuvette  126  so that clear images of the skin can be captured by the digital video camera  122 . The matte black wall of the cuvette  126  provides a dark background in contrast to the skin  102  illuminated by the red LED  130 . 
         [0031]    The digital video camera  122  includes a lens  134  and an image sensor  136 , e.g., a CMOS sensor. The lens  134  is placed adjacent to the window  132  and focuses light reflected from the skin  102  in the cuvette  126  onto the image sensor  136 . This allows the digital video camera  122  to capture images of the surface profile of the skin  102  as the skin  102  rises or falls in the cuvette  126  in response to changes in the air pressure in the cuvette  126 . 
         [0032]    The system  120  can be used to make at least two types of measurements. In a first type of measurement, the profile of the skin  102  is measured without correlating the profile to the air pressure in the cuvette  126 . The measurement can be performed when the air pressure in the cuvette  126  is decreasing or increasing. 
         [0033]    For example, the vacuum pump  112  can be activated to start pumping air out of the cuvette  126 , and images from the digital video camera  122  can be used to determine changes in the skin profile over a period of time. The suction force generated by the vacuum pump  112  is substantially constant. The amount of pressure change (from the preset pressure to the atmospheric pressure) is substantially constant, assuming that the atmospheric pressure is substantially constant. The amount of time for the skin  102  to reach a certain height, the height reached by the skin  102  after a certain amount of time, or the profile of the skin  102  after a certain amount of time, provides information about the elasticity of the skin  102 . This information may be useful in determining general conditions or healthiness of the skin  102 . 
         [0034]    The system  120  can measure how the skin profile changes over time as the air pressure in the cuvette  126  abruptly increases from a preset low-pressure level to the atmospheric pressure. When the vacuum pump  112  pumps air out of the cuvette  126  and the air pressure reduces to the preset low-pressure level, the vent solenoid  116  can be activated to allow air to enter the tube  194 , causing the air pressure in the cuvette  126  to abruptly increase to the atmospheric pressure. Changes of the skin profile after the vent solenoid  116  is activated can be measured using images captured by the digital video camera  122 . 
         [0035]    The amount of pressure change (from the preset pressure to the atmospheric pressure) is substantially constant, assuming that the atmospheric pressure is substantially constant. The amount of time for the skin  102  to return to its original state, the amount of change in the height of the skin surface after a certain amount of time, or the amount of change in the profile of the skin  102  after a certain amount of time, provides information about the elasticity of the skin  102 . This information may be useful in determining general conditions or healthiness of the skin  102 . The original state of the skin refers to the state of the skin  102  under normal atmospheric pressure. 
         [0036]    The skins of a healthy person and a dehydrated person may show different skin profile versus time characteristics. For example, when the vent solenoid  116  is activated to cause the air pressure in the cuvette  126  to abruptly increase from a preset low-pressure level to the atmospheric pressure, the skin of a healthy person may quickly return to its original state, whereas the skin of a dehydrated person may take a longer amount of time to return to its original state. 
         [0037]    A database can be established to indicate, for example, for a certain age and gender, when the amount of time required for the skin to return to its original state is beyond a certain threshold level, there is a higher likelihood that the person is dehydrated. 
         [0038]    In a second type of measurement, the profile of the skin  102  is measured and correlated with the air pressure in the cuvette  126 . For example, the vacuum pump  112  can be activated to gradually reduce the air pressure in the cuvette  126 . At the same time, the pressure sensor  114  senses the air pressure, and the digital video camera  122  captures images of the skin profile over a period of time. The images from the camera  122  can be processed to determine how the skin profile changes in response to changes in the air pressure in the cuvette  126 . The change in the skin profile in response to changes in the air pressure in the cuvette  126  can provide information about the elasticity of the skin  102 . This information may be useful in determining the general conditions or healthiness of the skin  102 . 
         [0039]    In one version of the system  120 , the output of the pressure sensor  114  is sent to an analog-to-digital converter (ADC)  138 . The outputs of the ADC  138  and the digital video camera  122  are sent to a notebook computer (not shown) (or a personal digital assistant, PDA) wirelessly or through, e.g., a Universal Serial Bus (USB) cable. The computer (or PDA) executes an application program that processes the measurement data from the pressure sensor  114  and the images from the digital video camera  122 . 
         [0040]    The application program may generate a number of characteristics that can be used as one of the factors in evaluating the healthiness or conditions of the skin  102 . The images captured by the digital video camera  122  include red portions with black backgrounds. The red portions represent the skin  102  inside the cuvette  126  illuminated by the red LED  130 . The application program may identify the highest point of the red portion in each image to determine how high the skin  102  rises in the cuvette  126  over time in response to a change in the air pressure. 
         [0041]    The application program may count the number of pixels in the red region to determine the area of the red region, which provides an indication of the volume of the skin in the cuvette  126 . The application program may perform integration to estimate the volume of the skin  102  in the cuvette  126 . The application program may correlate the changes in the skin profile to changes in the air pressure in the cuvette  126 . 
         [0042]    The system  120  may include a controller (not shown) to control some of the processes described above. For example, the user may press the cuvette  126  against a person&#39;s skin and press a button (not shown) of the system  120  to start a measurement sequence. Pressing the button generates a control signal that triggers the controller to activate the pump  112  to start pumping. The pressure sensor  114  senses the air pressure in the cuvette  126 . The output from the pressure sensor  114  is monitored by the application program. When the air pressure reaches a preset low-pressure level, the controller activates the vent solenoid  116  to cause the air pressure to return to atmospheric pressure, and deactivates the pressure pump  112 . The application program processes the measurement data from the pressure sensor  114  and the digital video camera  122 , and compares the measured data with pre-established data in a database. Base on the comparison, the application program outputs information on a display (not shown), in which the information can be used as one of the factors in evaluating the general conditions or healthiness of the skin  102 . 
         [0043]    The system  120  can be built using off-the-shelf components. For example, the digital video camera  122  can be, e.g., a WebCam !Live Ultra video camera, available from Creative Labs, Inc., Milpitas, Calif. The vacuum pump  112  can be a model 8018Gt 24 V diaphragm vacuum pump, available from Namiki Precision of California Inc., Belmont, Calif. The pressure sensor  114  can be, e.g., a gas pressure sensor model GPS-BTA, available from Vernier Software and Technology, Beaverton, Oreg. The computer software for processing the data from the pressure sensor  114  can be, e.g., LoggerPro, also available from Vernier Software and Technology. The LoggerPro software automatically detects the gas pressure sensor characteristics and records the output from the pressure sensor  114  directly in metric pressure units (i.e., Pa). The LoggerPro software can be set to record the pressure at, e.g., 200 samples per second while the vacuum pump  112  lowers the air pressure in the cuvette  126 . 
         [0044]    In another version of the system  120 , a built-in data processor processes the data from the pressure sensor  114  and the images from the digital video camera  122 . The system  120  may include a small liquid crystal display to show the measurement results. For example, the system  120  may show the number of seconds that it takes from the skin  102  to return to its original state when the air pressure changes abruptly from a preset low-pressure level to the atmospheric pressure. The user may consult a handbook that include tables of statistical information on skin measurements for people of different ages and gender to determine whether there is a likelihood that the person being measured is dehydrated. In some examples, the system  120  may have a flash memory that stores a database that includes statistical information on skin measurements for people of different ages and gender. Based on a comparison of the measurements and the statistical values in the database, the system  120  may provide an output on the display showing whether there is a likelihood that the person being measured is dehydrated. 
         [0045]    The data processor, the microcontroller, the skin displacement measuring device  150 , the vent solenoid  116 , the adjustable vacuum relief valve  118 , the vacuum pump  112 , and pressure sensor  114 , and the A/D converter  138 , can all be mounted in a battery-operated portable device. 
         [0046]      FIG. 3  show examples of images  140  of the surface profile of the skin  102  captured by the digital video camera  122 . The images  140  were obtained using simulation. The darker region  142  represents the matt black surface of the cuvette  122 , and the lighter region  144  represents the skin  102  inside the cuvette  122  illuminated by the red LED  130 . As the air pressure in the cuvette  122  decreases, the suction force on the skin  102  increases and a larger portion of the skin  102  is pulled into the cuvette  122 . 
       Example 2 
       [0047]      FIG. 4  is a schematic diagram of an example of a skin displacement measuring device  160  that includes a linear potentiometer  162  placed inside a cuvette  126 . The device  160  can be used in the system  120  of  FIG. 2  to replace to device  150 . A ferromagnetic metal foil disk  164  is attached to a region of the skin  102  being measured for displacement. The disk  164  can be attached to the skin  102  in numerous ways, such as using a two sided sticky tape  174 . As the skin  102  rises or falls in the cuvette  126 , the disk  164  rises or falls correspondingly. The linear potentiometer  162  measures the displacement of the disk  164 , indirectly measuring the displacement of the skin  102 . 
         [0048]    The linear potentiometer  162  uses an operating voltage that is provided by a 5V voltage regulator chip (not shown) connected to a 9 V battery (not shown). The linear potentiometer  162  has a slider  168 , in which different positions of the slider  168  correspond to different voltage outputs of the potentiometer  162 . A permanent magnet  166  is coupled to a connecting shaft  170 , which is coupled to the slider  168 . The magnet  166  is magnetically coupled to the foil disk  164 . As the disk  164  rises or falls, the slider  168  moves in response, changing the voltage output of the potentiometer  162 . 
         [0049]    When the vacuum pump  112  pumps air out of the cuvette  126 , the skin  102  rises or falls depending on the pressure inside the cuvette  126 . The displacement of the skin is measured by the linear potentiometer  106 . For example, when the skin  102  rises, the slider  168  is pushed upwards so that the potentiometer  162  outputs a higher voltage signal. Conversely, when the skin  102  falls, the slider  168  is pulled downwards so that the potentiometer  162  outputs a lower voltage signal. The output voltage can be recorded as a function of time, allowing the skin displacement to be measured as a function of time. 
         [0050]    Instead of using the output voltage of the potentiometer  162  as an indication of the position of the slider  168 , a ruler (not shown) may be placed behind the slider  168 , so that the position of the slider  168  can be determined based on the ruler. 
         [0051]    Using the potentiometer  162 , it is possible to determine the amount of time for the skin  102  to reach a certain height, or the height reached by the skin  102  after a certain amount of time. This information can be used to determine the elasticity of the skin  102 , which may be used as a factor in determining general conditions or healthiness of the skin  102 . 
         [0052]    The linear potentiometer  162  can be, e.g., an Alps model RDC1014A09, with a travel distance of 14 mm, an operating force of 250 mN, and a total resistance of 10 kΩ. The magnet  166  can be, e.g., a cylindrical, miniature, high energy density NdFeB permanent magnet. The foil disc  164  can be, e.g., cut from feeler-gage stock. The 5V voltage regulator chip can be, e.g., from ST Microelectronics. 
       Example 3 
       [0053]      FIG. 5  is a schematic diagram of an example of a skin displacement measuring device  200  that includes a cuvette  126  for forming a chamber over a portion of a skin  102  to be measured, and two Hall effect magnetic field sensors  202  (referred to as Hall-effect sensors  202 ) for measuring displacement of a permanent magnetic disk  204  attached to the skin  102 . The Hall-effect sensors  202  can be placed inside or outside of the cuvette  126 . When the magnetic disk  204  rises or falls in response to changes in the air pressure in the cuvette  126 , the magnetic field generated by the magnetic disk  204  changes. This change in the magnetic field is measured by the Hall-effect sensors  202 . In some examples, in order to reduce the effect of tilting of the magnetic disk  204  as the disk  204  moves with the skin  102 , the two Hall-effect sensors  202  can be mounted orthogonal to each other in the cuvette  126 . 
         [0054]    The Hall-effect sensors  202  can be, e.g., model 1321 from Allegro Microsystems. The precision digital micrometer can be, e.g., a micrometer available from Mitutoyo America Corporation, Aurora, Ill. The magnetic disk  204  can be, e.g., made of NdFeB and have a diameter of 3 mm and a thickness of 1 mm. 
         [0055]    The output of the Hall sensors  202  can be calibrated using a precision digital micrometer. For example, during a calibration process, the micrometer measures the displacement of the skin  102  at the same time that the Hall sensors  202  measure the changes in the magnetic field due to changes in the positions of the magnetic disk  204 . A calibration table can be established to correlate the output of the Hall sensor  202  to a corresponding skin displacement. Later, the micrometer can be removed, and displacement of the skin  102  can be measured using the Hall sensors  202  and the calibration table. 
         [0056]    In order to reduce the effect of the magnet  106  tilting as it moves with the skin, the two Hall sensors may be mounted orthogonal to each other on the chamber  104  or cuvette. A chamber  104  with sloping sides may assist in the placement of the sensors. 
       Example 4 
       [0057]      FIG. 6  is a schematic diagram of an example of a skin measuring system  180  for measuring mechanical properties of a skin  102 . The system  180  includes a first chamber  196  (e.g., a cuvette) that covers a portion of the skin  102  to be measured. The system  108  also includes a motorized syringe unit  184  that includes a second chamber  182 , e.g., formed by a low friction syringe  186 , that is coupled to the first chamber  196  through a tube  194 . The syringe  186  has a plunger (piston)  188  that is driven by a small geared motor  190 , which provides sufficient torque to drive the syringe plunger  188  in the presence of a substantial vacuum in the second chamber  182 . The syringe piston  188  is driven in and out of the second chamber  182  in an oscillating, sinusoidal fashion using an off-axis connection  192  to the motor  190 . 
         [0058]    The system  180  includes a vacuum pump  112 , a pressure sensor  114 , a vent solenoid  116 , and an adjustable vacuum relief valve  118 , similar to those shown in  FIG. 1 . When the vacuum pump  112  pumps air out of the first chamber  126  and the second chamber  182 , the air pressure in the first chamber  126  is reduced and the skin  102  is stretched upwards. This stretching of the skin  102  causes the volume within the first chamber  1126  to decrease. In addition, the syringe  186  can generate, e.g., a 0.25 mL volume change in the second chamber  182  by changing the position of the plunger  188 . For example, when the plunger  188  is at its highest position, the volume of the second chamber  182  is 0.25 ml greater than when the plunger  182  is at its lowest point. 
         [0059]    The small geared motor  190  can be, e.g., a motor available from FischerTechnik, Germany. The syringe  186  can be, e.g., a precision graduated, glass syringe, having a total volume of 2.0 ml. 
         [0060]    The system  180  measures skin displacement by measuring changes in the volume of the skin  102  inside the first chamber  196  by measuring changes in the air volume in the first chamber  126 . The changes of the air volume in the first chamber  126  are determined by changing the air volume of the second chamber  182  and measuring the changes in air pressure. The motor  190  operates to drive the plunger  188  up and down periodically for a period of time, causing the volume of the second chamber  182  to oscillate with a 0.25 mL volume change. The change in air pressure and the volume occupied by the skin in its stretched state is determined. The system  180  is calibrated such that at different pressures the volume of the skin  102  is measured, resulting in a mapping or relationship between the air pressure and the volume of skin in the first chamber  196 . This relationship allows a prediction of the volume of a deformed skin based on the measured pressure in the chamber  196 . The change in volume of the skin  102  over time provides information about the elasticity of the skin  102 , which can be used as one of the factors in determining general conditions or healthiness of the skin  102 , as described above. 
         [0061]    Other implementations and applications are also within the scope of the following claims. For example, the model numbers, dimensions, shapes, and parameters of the components in the skin measurement systems can be different from those described above. The video camera  122  can include, e.g., a charge-coupled device (CCD) image sensor instead of a CMOS image sensor. The data about skin elasticity can be further processed to produce additional useful information. For example, the skin elasticity data of a person can be compared with historical data to provide information about changes in the person&#39;s skin characteristics.