Optical imaging system
First Claim
1. Optical imaging system for imaging an object, mainly for a fingerprint reading apparatus, comprising:
- a total reflection prism (2) with a total reflection surface having a center (2.2.2) and constituting an object plane (2.2) for receiving the object, the total reflection prism (2) having a first transmitting surface (2.1) for receiving light to illuminate the object when placed on said object plane (2.2) through the interior of the prism (2), and a second transmitting surface (2.3) for transmitting the light reflected from said total reflection surface;
optical means (3) having an optical axis and an input and output pupil, said input pupil receiving the reflected light transmitted through the second transmitting surface (2.3) and said optical means (3) forming the image of the object plane (2.2) in an image plane which is perpendicular to the optical axis; and
electronic image detector means (4) located in the image plane, characterized in that said center (2.2.2) of the object plane (2.2) is offset from the optical axis (3.0) in a direction perpendicular to and relative to the optical axis (3.0) and said image detector means (4) is also offset from the optical axis (3.0) in accordance with said image formation by said optical means (3).
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Accused Products
Abstract
Optical imaging system between an object plane (2.2) of a total reflexion prism (2) and an image plane, mainly for a fingerprint reading apparatus, that comprises an optics (3) for imaging the object plane to the image plane, and an electronic image detector (4) in the image plane. The optics defines an optical axis (3.0) and input and output pupils, respectively. The total reflexion prism (2) is arranged in front of the input pupil of the optics (3). The prism has a first surface receiving light for illuminating the object plane through the interior of the prism and a further surface through which light reflected from the object plane passes towards the optics. The object plane closes an angle with the optical axis, which is preferably between 45° and 65° if the refraction index of the prism is between 1.5 and 1.85. The object plane (2.2) of the total reflexion prism (2) is offset relative to the optical axis (3.0) in normal direction and the image detector (4) is also offset in normal direction relative to the optical axis (3.0) to an extent which corresponds to the location of the image of said object plane.
17 Citations
11 Claims
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1. Optical imaging system for imaging an object, mainly for a fingerprint reading apparatus, comprising:
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a total reflection prism (2) with a total reflection surface having a center (2.2.2) and constituting an object plane (2.2) for receiving the object, the total reflection prism (2) having a first transmitting surface (2.1) for receiving light to illuminate the object when placed on said object plane (2.2) through the interior of the prism (2), and a second transmitting surface (2.3) for transmitting the light reflected from said total reflection surface; optical means (3) having an optical axis and an input and output pupil, said input pupil receiving the reflected light transmitted through the second transmitting surface (2.3) and said optical means (3) forming the image of the object plane (2.2) in an image plane which is perpendicular to the optical axis; and electronic image detector means (4) located in the image plane, characterized in that said center (2.2.2) of the object plane (2.2) is offset from the optical axis (3.0) in a direction perpendicular to and relative to the optical axis (3.0) and said image detector means (4) is also offset from the optical axis (3.0) in accordance with said image formation by said optical means (3). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification