IMAGE CAPTURING APPARATUS AND FOCUSING METHOD THEREOF

Abstract

An image capturing apparatus and a focusing method thereof are provided. The image capturing apparatus includes a flatbed, a light source, an optical sensing unit, a focusing unit and an adjuster medium. The flatbed is used for carrying an object. The light source is used for illuminating the object to output an optical signal. The optical sensing unit is used for sensing the optical signal to output an electrical image signal. The focusing unit is disposed between the flatbed and the optical sensing unit. The adjuster medium is configured between the object and the optical sensing unit for adjusting the object distance or the image distance, such that the focusing unit focuses the optical signal on the optical sensing unit to generate an electrical image signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (prior art) illustrates the imaging of a conventional contact image sensor (CIS);

FIG. 2A illustrates an image capturing apparatus according to an embodiment of the invention in a first state;

FIG. 2B illustrates an image capturing apparatus in a second state according to a first embodiment of the invention;

FIG. 2C illustrates an image capturing apparatus in a second state according to a second embodiment of the invention;

FIG. 3 illustrates a flowchart of a focusing method of image capturing apparatus according to an embodiment of the invention;

FIG. 4 illustrates an optical path of an image capturing apparatus according to an embodiment of the invention;

FIG. 5A illustrates an adjuster medium with multiple sheets in an image capturing apparatus according to an embodiment of the invention; and

FIG. 5B illustrates an adjuster medium with ladder structure in an image capturing apparatus according to an embodiment of the invention.

Claims

1. An image capturing apparatus, comprising: a flatbed for carrying an object;an optical sensing unit;a focusing unit;a light source for illuminating the object to generate an optical signal, wherein the optical signal forms an optical path from the object to the focusing unit first and then to the optical sensing unit next; andan adjuster medium, wherein when the object and the optical sensing unit are spaced by a first distance L1, the adjuster medium is disposed outside the optical path, and the object and the focusing unit are spaced by a second distance L2, when the object and the optical sensing unit are spaced by a third distance L3, the adjuster medium is disposed in the optical path, and the object and the focusing unit are spaced by a fourth distance L4, such that the focusing unit focuses the optical signal on the optical sensing unit to generate an image signal.

2. The image capturing apparatus according to claim 1, wherein the light source comprises a light guiding element for guiding a point light source to be a uniformed line light source.

3. The image capturing apparatus according to claim 1, wherein the focusing unit is a self-focus lens array.

4. The image capturing apparatus according to claim 1, wherein the optical sensing unit is a contact image sensor (CIS).

5. The image capturing apparatus according to claim 1, wherein the third distance L3 and the first distance L1 are differed by a height d, the adjuster medium has a thickness H and a refractive index n, and the thickness H, the refractive index n and the height d satisfy: H*(1−1/n)=d.

6. The image capturing apparatus according to claim 5, wherein when the adjuster medium is disposed in the optical path, the adjuster medium is configured between the object and the focusing unit.

7. The image capturing apparatus according to claim 6, wherein the thickness H of the adjuster medium and the fourth distance L4 satisfy: H≦L4.

8. The image capturing apparatus according to claim 5, wherein the focusing unit is movably disposed in the optical path.

9. The image capturing apparatus according to claim 8, wherein the position of the focusing unit in the optical path is adjusted such that the fourth distance L4 is equal to the second distance L2, and the adjuster medium is configured between the focusing unit and the optical sensing unit in the optical path.

10. The image capturing apparatus according to claim 1, wherein the adjuster medium is made of glass or acryl.

11. The image capturing apparatus according to claim 1, wherein the adjuster medium includes multiple sheets having the same or different adjusting values.

12. The image capturing apparatus according to claim 1, wherein the adjuster medium has different adjusting values at different portions.

13. The image capturing apparatus according to claim 12, wherein the adjuster medium is a ladder structure made of the same material.

14. A focusing method of image capturing apparatus, wherein the image capturing apparatus at least comprises a flatbed, a light source, an optical sensing unit, and a focusing unit, the method comprising: placing an object above the flatbed, wherein the object and the flatbed are spaced by a height d;loading an adjuster medium to an optical path between the object and the optical sensing unit to adjust an object distance or an image distance of the object;illuminating the object to output an optical signal by the light source; andthe optical signal passing through the focusing unit and the adjuster medium for being focused on the optical sensing unit.

15. The focus adjusting method according to claim 14, wherein when the adjuster medium adjusts the object distance of the object, the step of loading the adjuster medium comprises: positioning the adjuster medium in the optical path between the object and the focusing unit.

16. The focus adjusting method according to claim 14, further comprising: moving the focusing unit towards the object to adjust the object distance.

17. The focus adjusting method according to claim 16, wherein when the adjuster medium adjust the image distance of the object, the step of loading the adjuster medium comprises: positioning the adjuster medium in the optical path between the focusing unit and the sensing unit.

18. The focus adjusting method according to claim 16, wherein the focusing unit is moved towards the object by a distance d.