Patent Abstract:
The devices, systems and methods may continuously detect surface characteristics of a sample surface at a tilt. The exemplary system may have a conveying device for moving a sample surface, a light source for reflecting a beam of light off the sample surface, and a light detector with a light detection surface for continuous light detection. A lens may be used to reflect the beam of light from the sample surface and focus the beam of light on the light detection surface of the light detector. The area of the beam of light at the point of focus on the light detection surface may be unequal to the light detection surface. A reference analyzer may be used to determine the optical surface based on a comparison of the reflected light received with known reflected light values for known sample surfaces.

Full Description:
FIELD OF THE INVENTION 
   The present invention relates generally to detecting surface characteristics of a sample surface, and more particularly to continuous detecting of surface characteristics of a moving sample surface. 
   BACKGROUND OF THE INVENTION 
   During the paper making process water, refined pulp and other additives are combined to give the finished paper the desired properties. The mix is spread over a mesh screen which forms the paper and lets the water be extracted. The paper then travels through different processes and machines designed to remove the water from the paper. After the paper is dry, the paper is run between drums to give the desired smoothness. This process may be referred to as calendering the paper. The more times paper is calendered the less bulk it has but the smoother the finish of the paper. To create glossy paper, uncoated paper may be coated with a paint-like product and buffed by rollers under very high pressure, to create a shiny appearance. This process may be referred to as supercalendering. Additional varnish layers may be applied to paper during the printing process to provide a gloss surface on the paper. The gloss surface may also protect the paper from the surrounding environment. During the various manufacturing process a continuous roll of paper weaves throughout the machinery of the press. Rolls and presses are used to move the paper between the various manufacturing processes. 
   To ensure that the paper surface has received the correct amount of gloss, sensors are used to measure the gloss of sample surfaces. Referring to  FIG. 1A , sensor  100 A may have a light source  102 A for providing a light beam  104 A to illuminate sample surface  106 A at a pass-line. Light beam  104 A is reflected off sample surface  106 A. The intensity of the reflected light is measured with light detector  108 A. The reflected light is measured by light detecting surface  110 A of light detector  108 A to determine the light intensity of the reflected light. The gloss level is calculated by determining the ratio of the reflecting light beam intensity to the intensity of the illuminating light beam. The intensities of the reflected light are compared with known values of intensity for various gloss sample surfaces. 
   Referring to  FIG. 1B , as the paper moves along the manufacturing process, sample surface  106 B of a web of paper may flutter or wave due to vibrations imparted by the devices, applicators, and other machinery used in the manufacturing process. The flutter or wave may cause the sample surface  106 B to move to a new sample surface location  112 B. The movement of the sample surface  106 B may cause errors to the measured gloss values because the optical arrangement of the gloss sensor system may require a very precise geometry in order to operate in a correct manner. 
   Referring to  FIG. 1C , as the paper moves along the manufacturing process, the sample surface  106 C of the web of paper may tilt and/or cup due to shifts in the web of paper in both lateral and longitudinal directions. The tilt may cause the sample surface  106 C to shift to a new sample surface angle  112 C. This may be problematic with on-line measurement applications. The tilt of the sample surface  106 C may cause errors to the measured gloss values. The erratic sensor response is caused by the optical arrangement of the gloss measurement. The optics may require a very precise geometry. The light source  102 C may reflect the light beam  104 C off the sample surface  106 C exactly onto the light detecting surface  108 C of the light detector  110 C. 
   If sample surface  106 B,  106 C moves or tilts, some part of the reflected light rays may be lost and the measured signal will be erratic. The current state of the art may provide for precise measurements in a laboratory setting when the sample position can be easily controlled but, as explained above, such control is not easily obtained in a manufacturing environment. 
   In paper and board manufacturing, non-touching measurement principles may be preferred over sensor techniques that make contact with the paper web. In addition, paper web stabilization techniques such as mechanical sheet stabilizers are also not preferred. For example, the use of mechanical sheet stabilizers can cause scoring on the product surface. Due to such markings, it may be impossible to use sheet stabilizers in certain applications. Also, sheet stabilizers may tend to increase dust and dirt problems by rubbing the moving web. The cross-direction profiles of paper and board webs can have many types of deviations from a straight line. For example, the base cross profile can be warped in many different directions. Because warping or scoring of paper the optimal position of the paper web for on-line gloss measurement is very difficult and sometimes impossible to guarantee. 
   Accordingly, an efficient and effective device, method, and system is needed for detecting surface characteristics of a sample surface. In addition, the system and method may provide for detecting surface characteristics of a moving sample surface. 
   SUMMARY OF THE INVENTION 
   It is, therefore, an object of the present invention to provide devices, systems, and methods for detecting surface characteristics of a sample surface at a tilt where the surface is stable or moving. According to an exemplary embodiment of the present invention, the device may have a conveying device for moving a sample surface. The device may also have a light source for reflecting a beam of light off the sample surface and a light detector with a light detection surface for continuous light detection. A lens may be used for receiving the beam of light reflected from the sample surface and focusing the beam of light on the light detection surface of the light detector. The area of the beam of light prior to the lens may be unequal to an area of a lens receiving surface. A reference analyzer may determine the optical properties of the analyzed surface based on a comparison of the reflected light received with known reflected light values for known sample surfaces. 
   In an alternate embodiment, the area of the focused beam of light may be larger than the area of the light detection surface and the reference analyzer comparison may be based on the area of the detection surface. In another embodiment, the area of the focused beam of light may be smaller than the area of the light detection surface and the reference analyzer comparison may be based on the area of the focused beam of light prior to the lens. In another embodiment, the reference analyzer may determine the gloss, the deviation of gloss, the sparkle spot size, or the number of spot sizes. In another embodiment, the light detector may be a Charge Coupled Device (CCD) camera., Charge Coupled Device (CCD) array, Complementary Metal Oxide Semiconductor (CMOS) camera, Complementary Metal Oxide Semiconductor (CMOS) array, photodiode array or photodiode. In yet another embodiment, the sample surface may be the surface of a moving web of paper. In yet another embodiment, the reference analyzer may compare the intensity of reflected light received with known intensity reflected light values of known sample surfaces. 
   According to an exemplary embodiment of the present invention, the method may involve the following steps. The sample surface may be conveyed along a mechanized process at a tilt. A beam of light is emitted onto the sample surface and reflected off the sample surface. The beam of light reflected from the sample surface is focused onto a light detection surface of a light detector. The area of the beam of light prior to the lens is unequal to an area of a lens receiving surface. The beam of light is focused by the lens onto the light detection surface of the light detector continuously. The optical surface is determined based on a comparison of the reflected beam of light received with known reflected light values for known sample surfaces. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objectives and advantages of the present invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference numbers refer to like parts throughout, and in which: 
       FIG. 1A  is a generalized schematic of a prior art gloss sensor. 
       FIG. 1B  is a generalized schematic of a prior art gloss sensor with flutters and waves of the sample surface at the pass-line. 
       FIG. 1C  is a generalized schematic of a prior art gloss sensor with tilt of the sample surface at the pass-line. 
       FIG. 2A  is a generalized schematic of a sensor used to implement the exemplary light source embodiment of the present invention. 
       FIG. 2B  is a generalized schematic of a sensor used to implement the exemplary light source embodiment of the present invention with flutters and waves of the sample surface at the pass-line. 
       FIG. 2C  is a generalized schematic of a sensor used to implement the exemplary light source embodiment of the present invention with a tilted sample surface at the pass-line. 
       FIG. 3  is a flow chart illustrating an exemplary method for the sensor used to implement the light source embodiment of the present invention. 
       FIG. 4A  is a generalized schematic of a sensor used to implement the exemplary light detector embodiment of the present invention. 
       FIG. 4B  is a generalized schematic of a sensor used to implement the exemplary light source embodiment of the present invention with flutters and waves of the sample surface at the pass-line. 
       FIG. 4C  is a generalized schematic of a sensor used to implement the exemplary light detector embodiment of the present invention with a tilted sample surface at the pass-line. 
       FIG. 5  is a flow chart illustrating an exemplary method for the sensor used to implement the light detector embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A sensor is used to measure the gloss of a sample surface by directing a beam of light at the sample surface and electronically comparing the reflectance of the sample surface to that of a standardization surface having a known gloss. According to an exemplary light source embodiment of the present invention, the light beam illuminating the sample surface may have a larger area than the light beam accepted and detected by the light detector. The illuminated area of the sample surface is larger than the area, which is seen by the light detector. The illuminated area of the sample surface is larger than the measurement area, which is seen by the light detector. This arrangement allows the sample surface to change its position within predefined geometrical limits. The measurement area of the light detector remains in the illuminated area as the sample surface moves. The intensity of reflected light received by the light detector is compared with known values of intensity for various gloss sample surfaces based on the area of the light detector. 
   According to an exemplary light detector embodiment, a narrow light beam is used to illuminate the sample surface and is reflected onto a light detector. The illuminated area of the sample surface is smaller than the area which is seen by the light detector. The illuminated area of the sample surface is smaller than the measurement area, which is seen by the light detector. This arrangement allows the sample surface to change its position within the geometrical limits. The measurement area of the beam remains within the detection area of the light detector as the sample surface moves. The intensity of reflected light received by the light detector is compared with known values of intensity for various gloss sample surfaces based on the area of the beam of light. The various embodiments described herein may comply with various known standards, for example, the Technical Association of the Pulp and Paper Industry (TAPPI) standards as well as other known industry and government standards. 
   According to an exemplary lens embodiment, a light beam may illuminate the sample surface and is reflected onto a light detector. The illuminated area of the sample surface may be collimated to a beam smaller than the area which is seen by the light detector. The illuminated area of the sample surface may be collimated to a beam larger than the area which is seen by the light detector. This arrangement allows the sample surface to change its position within the geometrical limits in a similar fashion as previously described in the light detector and light source embodiment. The measurement area of the beam remains within the detection area of the light detector as the sample surface moves. The intensity of reflected light received by the light detector is compared with known values of intensity for various gloss sample surfaces based on the area of the beam of light or the area of the light detector, respectively. 
   Referring to  FIG. 2 , sensor  200 A may include light source  202 A with lens  203 A for providing light beam  204 A to illuminate sample surface  206 A at a pass-line. Light source  202 A and lens  203 A provide light beam  204 A with an area larger than light detection surface  210 A of the light detector  208 A. Light source  202 A provides a focused beam of light or collimated light beam for example a laser or other method of providing a focused beam of light. Light source  202 A may be a variety of electromagnetic energy sources. For example, the light source may emit a non-visible wavelength of light energy to prevent interference by overhead lighting or other sources of light within the manufacturing process. 
   Sample surface  206 A may be a variety of materials handled in a manufacturing process or mechanized process. For example, sample surface  206 A may be a web of paper or board. The web is continuously moved throughout the manufacturing process using various rollers, presses, and other machinery. Sample surface  206 A is not limited to a web of paper. Sample surface  206 A may be individual sheets of material that are advanced on a conveyor belt or devices for transporting sheets of material. 
   Sensor  200 A provides accurate measurements of the sample surface without or with a reduced need for stabilization. Light beam  204 A is reflected off the sample surface  206 A. The intensity of the reflected light is measured with a light detector  208 A. The reflected light is measured by light detecting surface  210 A of light detector  208 A to determine the light intensity of the reflected beam of light  204 A. The light detecting surface  210 A may define the area seen by the light detector  208 A. The measurement geometry and optics may be regulated by industry standards, for example, Technical Association of the Pulp and Paper Industry (TAPPI) T480. 
   The light detecting surface  210 A converts the beam of light  204 A into electrical current. The light detecting surface  210 A may be composed of a variety of devices, for example, Charge Coupled Device (CCD) camera, Charge Coupled Device (CCD) array, Complementary Metal Oxide Semiconductor (CMOS) camera, digital Complementary Metal Oxide Semiconductor (CMOS) imaging, or photodiodes. The light detector  208 A may be a continuous detecting device, for example, a video camera. The signal generated by light detector  208 A may be analog or converted to a digital signal for processing. The signal of light detector  208 A is fed into a reference analyzer (not shown). 
   Referring to  FIG. 2B , as the paper moves along the manufacturing process, sample surface  206 B of the web of paper may dip, flutter, and wave due to shifts in the web of paper in both lateral and longitudinal directions. The sensor  200 B has the light source  202 B for providing the light beam  204 B to illuminate the sample surface  206 B at the pass-line. The light source  202 B provides the light beam  204 B with an area larger than a light detection surface  210 B of the light detector  208 B. The sensor  200 B provides accurate measurements of the sample surface without or with a reduced need for stabilization. The light beam  204 B is reflected off the sample surface  206 B. The intensity of the reflected light is measured with the light detector  208 B. The reflected light is measured by the light detecting surface  210 B of the light detector  208 B to determine the light intensity of the reflected beam of light  204 B. The shift of the sample surface  206 B to a new sample surface angle  212 B does not affect the gloss measurement. As long as the light detecting surface  210 B remains in the area of the light beam, the intensity detected will remain consistent based on the area of the light detection surface  210 B. 
   Referring to  FIG. 2C , as the paper moves along the manufacturing process, sample surface  206 C of the web of paper may tilt and/or cup due to shifts in the web of paper in both lateral and longitudinal directions. The sensor  200 C has the light source  202 C for providing the light beam  204 C to illuminate the sample surface  206 C at the pass-line. The light source  202 B provides the light beam  204 C with an area larger than a light detection surface  210 C of the light detector  208 C. The sensor  200 C provides accurate measurements of the sample surface without or with a reduced need for stabilization. The light beam  204 C is reflected off the sample surface  206 C. The intensity of the reflected light is measured with the light detector  208 C. The reflected light is measured by the light detecting surface  210 C of the light detector  208 C to determine the light intensity of the reflected beam of light  204 C. The tilt of the sample surface  206 C to a new sample surface angle  212 C does not affect the gloss measurement. As long as the light detecting surface  210 C remains in the area of the light beam, the intensity detected will remain consistent based on the area of the light detection surface  210 C. 
   The reference analyzer compares the intensity of the signal received from light detector  210  with known values of intensity for various gloss sample surfaces. Architecturally in terms of hardware, the reference analyzer may include a processor, memory, and one or more input and output interface devices. The local interface may have additional elements, which are omitted for simplicity, such as controllers, buffers (caches), drivers, repeaters, and receivers, to enable communications. Further, the local interface may include address, control, and/or data connections to enable appropriate communications among the components of a network. 
   The reference analyzer may determine the gloss level of sample surface  206  by determining the ratio of the reflecting light beam intensity to the intensity of the illuminating light beam from the light source  202 . The amount of light dispersed by sample surface  206  is used to determine the gloss level of sample surface  206 . The reference analyzer may use a stored table or equations to compute the gloss level of the sample surface  206 . The gloss level is determined by comparing the ratio of intensity with the intensity of the gloss level for known sample tables of the gloss level. 
   The systems and methods may also be incorporated in software used with a computer or other suitable operating device of the reference analyzer. The reference analyzer may also include a Graphic User Interface (GUI) to allow the administrator or user to enter, view and store the gloss level or enter constraints associated with the desired gloss level to control other devices of the manufacturing process. 
   Referring to  FIG. 3 , a flow chart illustrates an exemplary method for the sensor used to implement the light source embodiment  300  of the present invention. The manufacturing process advances sample surface  206  to the pass-line of sensor  200  (block  302 ). The light source  202  directs beam of light  204  onto sample surface  206  (block  304 ). The beam of light  204  is reflected by sample surface  206  (block  306 ). 
   The beam of light reflected by the sample surface is detected on a light detection surface  210  of the light detector  208  (block  308 ). The light detection surface  210  has an area smaller than the area of the beam of light  204 . This allows the sample surface  206  to flutter or tilt within a designated geometry. The designated geometry is controlled by the area of the beam of light  204  relative to the area of detection on the light detecting surface  210 . Increasing the area of the light beam  204  may increase the amount of movement allowed by the sample surface  206  to a new location of the sample surface  212 . Generally, the area of the beam of light  204  is circular; however, the invention may utilize a variety of shapes with either the beam of light  204  or the area of the light detection surface  210 . For example, the beam of light  204  may be a circle and the light detection surface  208  may be a square with a width larger than the diameter of the beam of light  204 . The reference analyzer determines the gloss level of the sample surface  206  by comparing the reflected light received from the area of the light detection surface  210  with known reflected light values for known sample surfaces based on the area of the light detection surface  210  (block  310 ). 
   Referring to  FIG. 4A , the sensor  400 A may have a light source  402 A with lens  403 A for providing a light beam  404 A to illuminate the sample surface  406 A at a pass-line. The light source  402 A and lens  403 A provide a light beam  404 A with an area smaller than a light detection surface  410 A of the light detector  408 A. The light source  402 A provides a focused beam of light  404 A as previously described with regard to the exemplary light detector embodiment. The sample surface  406 A may also be a variety of materials as previously described with regard to the exemplary light source embodiment. 
   Sensor  400 A provides accurate measurements of sample surface  406 A without or with a reduced need for stabilization. Light beam  404 A is reflected off sample surface  406 A. The intensity of the reflected light is measured with light detector  408 A. The reflected light is measured by light detecting surface  410  of light detector  408 A to determine the light intensity of the reflected beam of light  404 A. The light detecting surface  410 A may define the area seen by light detector  408 . 
   Light detecting surface  410 A converts the beam of light  404 A into electrical current using a variety of light detecting elements as previously described with regard to the exemplary light source embodiment. The signal of light detector  408 A is fed into a reference analyzer (not shown). The reference analyzer compares the intensity of the signal received from light detector  410 A with known values of intensity for various gloss sample surfaces. Architecturally in terms of hardware, the reference analyzer is similar to the reference analyzer of the exemplary light source embodiment as previously described. 
   Referring to  FIG. 4B , as the paper moves along the manufacturing process, sample surface  406 B of the web of paper may shift, flutter, and wave due to shifts in the web of paper in both lateral and longitudinal directions. Sensor  400 B has light source  402 B for providing light beam  404 B to illuminate sample surface  406 B at the pass-line. Light source  402 B provides light beam  404 B with an area smaller than a light detection surface  410 B of light detector  408 B. Sensor  400 B provides accurate measurements of the sample surface without or with a reduced need for stabilization. Light beam  404 B is reflected off sample surface  406 B. The intensity of the reflected light is measured with light detector  408 B. The reflected light is measured by light detecting surface  410 B of light detector  408 B to determine the light intensity of the reflected beam of light  404 B. The shift of sample surface  406 B to a new sample surface angle  412 B does not affect the gloss measurement. As long as the beam of light  404 B remains in the area of light detecting surface  410 B, the intensity detected will remain consistent based on the area of the beam of light  404 B. 
   Referring to  FIG. 4C , as the paper moves along the manufacturing process, sample surface  406 C of the web of paper may tilt and/or cup due to shifts in the web of paper in both lateral and longitudinal directions. Sensor  400 C has light source  402 C for providing light beam  404 C to illuminate sample surface  406 C at the pass-line. Light source  402 C provides light beam  404 C with an area smaller than a light detection surface  410 C of light detector  408 C. Sensor  400 C provides accurate measurements of the sample surface without or with a reduced need for stabilization. Light beam  404 C is reflected off sample surface  406 C. The intensity of the reflected light is measured with light detector  408 C. The reflected light is measured by light detecting surface  410 C of light detector  408 C to determine the light intensity of the reflected beam of light  404 C. The tilt of sample surface  406 C to a new sample surface angle  412 C does not affect the gloss measurement. As long as the beam of light  404 C remains in the area of light detecting surface  410 C, the intensity detected will remain consistent based on the area of the beam of light  404 C. 
   The reference analyzer may determine the gloss level of the sample surface  406  by determining the ratio of the reflecting light beam intensity to the intensity of the illuminating light beam from light source  408 . The amount of light dispersed by sample surface  406  is used to determine the gloss level of sample surface  406 . The reference analyzer may use a stored table or equations to compute the gloss level of sample surface  406 . The gloss level is determined by comparing the ratio of intensity with the intensity of gloss levels for known sample tables of the gloss level. 
   Referring to  FIG. 5 , a flow chart illustrates an exemplary method for the sensor used to implement the light detector embodiment  400  of the present invention. The manufacturing process advances sample surface  406  to the pass-line of sensor  400  (block  502 ). Light source  402  directs beam of light  404  onto sample surface  406  (block  504 ). Beam of light  404  is reflected by sample surface  406  (block  506 ). 
   Beam of light  404  reflected by the sample surface  406  is detected on light detection surface  410  of light detector  408  (block  508 ). Light detection surface  410  has an area larger than the area of the beam of light  404 . This allows sample surface  406  to flutter or tilt within a designated geometry. The designated geometry is controlled by the area of the beam of light  404  relative to the area of detection on light detecting surface  410 . Increasing the area of light beam  404  may increase the amount of movement allowed by sample surface  406  to a new location of sample surface  412 . The reference analyzer determines the gloss level of sample surface  406  by comparing the reflected light received from light detection surface  410  with known reflected light values for known sample surfaces based on the area of the beam of light  404  (block  510 ). 
   It will be understood that the foregoing is only illustrative of the principles of the invention and that various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. Accordingly, such embodiments will be recognized as within the scope of the present invention. For example, the exemplary embodiments are illustrated as being implemented to determine the gloss level of the sample surface, however, one skilled in the art will appreciate that embodiments of the invention may be implemented with a variety of other surface characteristics. 
   Persons skilled in the art will also appreciate that the present invention can be practiced by other than the described embodiments, which are presented for purposes of illustration rather than of limitation and that the present invention is limited only by the claims that follow.

Technology Classification (CPC): 6