Pressure activated fingerprint input apparatus
An image input apparatus includes an image reading assembly positioned below a placement surface on which an object to be examined is placed, and a sensing circuit for sensing that the object is placed on the placement surface, in accordance with a pressure applied to the placement surface.
1. An image input apparatus comprising:
an image reading assembly including an optical sensor arranged under a placement surface on which an object to be examined is placeable;
sensing means, arranged under the image reading assembly, for sensing whether the object is placed on the placement surface based on a pressure applied to the placement surface by the object; a light source which emits light and illuminates the object with the light, and which is arranged between the image reading assembly and the sensing means; and
a diffusion light-guiding plate which is arranged between the image reading assembly and the sensing means, and which guides the light emitted by the light source from the light source to the object, when the sensing means senses that the object is placed on the placement surface;
wherein the sensing means senses the pressure through the diffusion light-guiding plate.
2. The image input apparatus according to claim 1 , further comprising driving means for causing the image reading assembly to perform an image reading operation, when the sensing means senses that the object is placed on the placement surface.
3. The image input apparatus according to claim 1 , wherein the sensing means comprises:
a pressure sensor which senses the pressure applied to the placement surface; and
comparing means for comparing a pressure level sensed by the pressure sensor with a threshold value for discriminating between a placed state and an unplaced state and, if the threshold value is exceeded, outputting a trigger signal for causing the image reading assembly to perform an image reading operation.
4. The image input apparatus according to claim 1 , further comprising adjusting means for controlling the light source so that the brightness of the light from the light source is adjusted in accordance with the pressure applied to the placement surface by the object.
5. The image input apparatus according to claim 1 , wherein the optical sensor comprises a plurality of double-gate transistors arranged in a matrix manner.
6. The image input apparatus according to claim 1 , further comprising a holder for holding the object such that the object is properly placed in positions of the image reading assembly and the sensing means.