Optical: systems and elements – Prism
Patent
1997-02-28
2000-11-07
Shafer, Ricky D.
Optical: systems and elements
Prism
359833, 359834, 356 71, G02B 504, G03B 2772
Patent
active
061445118
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical device fixing device, and particularly to a prism mounting device for an optical device using light beam which passes through a prism or lens, a lens fixing device for aligning and fixing the center of a lens with a prescribed optical axis, and a reflecting mirror fixing device for fixing a reflecting mirror of an optical device.
2. Description of the Related Art
To open a locked door or to allow only registered persons to access to valuable data, a judging device according to fingerprint checking has been developed.
A conventionally known developed individual fingerprint checking device comprises a prism, a lens, and an image processing circuit. FIG. 12 shows such a device as a schematic vertical sectional view.
The device shown in FIG. 12 has a fingerprint checking device housed into a case 1 and a top lid 2 mounted at the top. Within the case 1, a prism 4 and a lens 5 are disposed substantially in a horizontal direction, and an emission unit 3 is positioned below the prism 4. The upper part of the prism 4 is in contact with the top lid 2. The prism 4 is positioned with its center axis aligned with the optical axis of the lens 5. A mirror 7 is positioned to reflect the light coming out of the lens 5, and the light reflected on the mirror 7 enters an image pickup device 8. The prism 4 is fully covered with a light impermeable material excluding a surface opposed to the emission unit 3, a surface on which a finger 9 is positioned, and a surface from which light is entered into the lens 5.
In the device shown in FIG. 12, when light is emitted from the emission unit 3 to the prism 4, the emitted light passes through the prism 4 and also the top lid 2. When the finger 9 is positioned on a lighted area to check a fingerprint, the light from below is substantially absorbed at valley portions of the fingerprint, and the light is mostly reflected on ridge portions of the fingerprint to enter the prism 4.
As indicated by the arrows, the light goes downward within the prism 4, and reflects again on the prisms's surface opposed to the emission unit 3 (a bottom face 4a of the prism 4). In view of the shape of the prism 4, the surface of the prism 4 opposite from the lens 5 forms a reflection surface 10 for the light, so that the light reflected on the bottom face 4a of the prism 4 is reflected on the reflection surface 10, and goes straight through the prism 4 to the lens 5.
The lens 5 is covered by a lens holder 6 and held within the case 1. Accordingly, the position of the lens 5 can be adjusted to focus the light, which has advanced through the prism 4 toward the lens 5, beyond the lens 5 by the lens 5. By adjusting to focus on the mirror 7, the fingerprint image is enlarged by the lens 5, and the light reflected on the mirror 7 reaches the image pickup device 8 to process the fingerprint as a digital image, for example.
To process a small line pattern like a fingerprint as a digital image, the dimensions of the prism 4 and the lens 5 are prescribed, and the dimension of the case 1 for accommodating them is roughly determined accordingly. But, as to the light beam for fingerprint checking, in order to accurately form a fingerprint image on the image pickup device, it is necessary to accurately set the positions of the prism 4 and the lens 5 within the case 1.
Therefore, a position adjusting means has been used as shown as schematic views in FIG. 13 and FIG. 14.
FIG. 13 is a diagrammatic sectional view showing a position adjusting means. In FIG. 13, the prism 4 is in contact with the case 1 by being pushed slightly by springs 11, 12 from two sides toward the end on the lens side in the case 1. Strength and direction of the springs 11, 12 are adjusted so that the optical axis of the prism 4 agrees with the optical axis of the lens 5 at the position where the prism 4 is pushed within the case 1 by the springs 11, 12.
FIG. 14 is similar to FIG. 13 except that screws 13, 14 are used instead of the springs 11, 12 used in F
REFERENCES:
patent: 904066 (1908-11-01), Jacob
patent: 2400401 (1946-05-01), Eckerman et al.
patent: 3039405 (1962-06-01), Barr
patent: 4470664 (1984-09-01), Shirasawa
patent: 4727859 (1988-03-01), Lia
Imaki Takeyoshi
Umetsu Hitoshi
Fujitsu Denso Ltd.
Shafer Ricky D.
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