Method and device for achieving high contrast surface illumination
DCFirst Claim
1. A method of imaging topography of a surface of a medium comprising the steps of:
- providing illumination of said surface such that light strikes said surface at angles within sixteen degrees of said surface, including simultaneously directing said light from multiple planes of incidence, each being perpendicular to said surface, thereby forming an illumination pattern on at least a portion of said surface such that said illumination pattern has first areas of high brightness that correspond to raised surface features of said medium and has second areas of relatively low brightness; and
forming data responsive to said first and second areas.
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Abstract
A method and device for acquiring data related to topography of a medium includes projecting light, allowably from more than one direction, onto the surface of the medium at an angle of less than sixteen degrees relative to the surface and imaging the surface. For example, the imaging sensor may be an array of sensor elements that is used to determine navigation of a hand-held scanner along an original. By introducing light at an angle of less than sixteen degrees, surface irregularities cast shadows that form a high contrast illumination pattern along the surface of the medium. The navigation sensor detects multi-element variations of intensity of scattered light from the surface with respect to positions along the surface, so that the Nyquist criteria are adequately satisfied. Typically, the light is collimated incoherent light, but this is not critical. The illumination angle can be established by using a prism. The prism may have an antireflective thin film coating on one or more prism faces. The employment of a prism provides a number of advantages, such as use of a transparent surface in contact with the media and raising the illumination source(s) away from the media.
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Citations
23 Claims
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1. A method of imaging topography of a surface of a medium comprising the steps of:
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providing illumination of said surface such that light strikes said surface at angles within sixteen degrees of said surface, including simultaneously directing said light from multiple planes of incidence, each being perpendicular to said surface, thereby forming an illumination pattern on at least a portion of said surface such that said illumination pattern has first areas of high brightness that correspond to raised surface features of said medium and has second areas of relatively low brightness; and forming data responsive to said first and second areas. - View Dependent Claims (2, 3)
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4. A method of acquiring data related to topography of a medium comprising the steps of:
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providing a structure having an illumination source and an array of sensor elements in which each sensor element has a field of view; directing radiation from said illumination source at a surface of said medium such that said radiation defines a path that is fixed relative to said sensor elements, including establishing said path to be at an angle of less than sixteen degrees relative to said surface, thereby forming an illumination pattern on at least a portion of said surface such that said illumination pattern has first areas of relatively high brightness that correspond to raised surface features of said medium and has second areas of relatively low brightness; providing relative movement between said structure and said medium; during said step of providing relative movement and by means of said sensor elements, detecting said first areas of relatively high brightness and said second areas of relatively low brightness; and forming an image of said surface of said medium, including tracking positions of said first and second areas during said step of providing relative movement in order to determine at least one of position encoding information and image information. - View Dependent Claims (5, 6, 7, 8, 9, 10)
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11. A method of acquiring data related to topography of a surface comprising the steps of:
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providing a first illumination source and an array of sensor elements, each sensor element having a field of view; projecting radiation from said first illumination source onto a region of said surface having surface irregularities such that raised locations of said surface cast shadows among adjacent raised locations, thereby providing an illumination pattern having detectable contrast between high brightness pattern features corresponding to said raised locations and low brightness pattern features corresponding to locations adjacent to said raised locations, said step of projecting radiation including defining an angle of incidence of at least 74 degrees to the normal of said region of said surface; positioning said array of sensor elements to detect radiation intensity along said region of said surface; providing relative movement between said region and said first illumination source and said array, said relative movement being in a direction generally parallel to said surface; and using said array, imaging high and low intensity features having a cross sectional dimension at least twice as great as a cross sectional dimension of said field of view. - View Dependent Claims (12, 13, 14, 15)
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16. A device for acquiring data related to topography of a medium comprising:
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a hand-manipulatable housing having a generally planar face for positioning in substantially parallel relationship with a surface of said medium; an illumination source connected to said housing at said planar face; an array of sensing elements positioned along said planar face; and optical means connected to said housing for directing light from said illumination source to reach said surface at an angle of less than sixteen degrees relative to said surface and for redirecting scattered light from said surface to impinge said sensing elements. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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Specification