Image capturing apparatus
The present invention provides a digital camera which has a plurality of image capturing optical systems and quickly performs automatic focusing. A digital camera includes a first image capturing optical system formed from a lens 2 and a first image sensor, and a second image capturing optical system formed from a lens 3 and a second image sensor. An image processor detects a phase difference between an image of a single subject formed on the first image sensor and an image of the same formed on the second image sensor, in order to perform phase-difference AF. Since the lenses 2, 3 have different focal lengths, the image processor executes correlation operation after having performed conversion processing for causing a scaling factor of the image formed by the first image sensor to coincide with that of the image formed by the second image sensor, to thus detect a phase difference.
1. An image capturing apparatus comprising:
a first image capturing optical system which generates a first image output signal;
a second image capturing optical system which is spaced apart from the first image capturing optical system by a predetermined distance and differs from the first image capturing optical system in terms of an angle of field which generates a second image object signal;
conversion mechanism which performs conversion operation for causing a scaling factor of the first image to coincide with a scaling factor of the second image; and
distance computing mechanism which computes a distance to a subject by means of performing correlation operation of a first image and the second image after the conversion mechanism performs the conversion operation.
2. The image capturing apparatus according to claim 1 , wherein the conversion mechanism causes a scaling factor of the first image to coincide with a scaling factor of the second image by means of converting the resolution of at least one of the first and second images.
3. The image capturing apparatus according to claim 1 , wherein the first image capturing optical system and the second image capturing optical system have substantially the same aspect ratio and pixel size.
4. The image capturing apparatus according to claim 1 , wherein the first image capturing optical system includes a fixed focus lens, and the second image capturing optical system includes a zoom lens.
5. The image capturing apparatus according to claim 1 , wherein each of the first image capturing optical system and the second image capturing optical system includes a zoom lens.
6. The image capturing apparatus according to claim 1 , wherein the computing mechanism includes
contrast detection means for detecting contrast of at least one of the first image and the second image; and
comparison means for comparing the detected contrast with a reference value; and
the image capturing apparatus further comprises
focus adjustment means for adjusting focus until the contrast reaches the reference value when the contrast is less than the reference value, wherein
the distance computing mechanism executes correlation operation after contrast has reached the reference value.
7. The image capturing apparatus according to claim 1 , wherein the distance computing mechanism executes two-dimensional correlation operation as correlation operation.
8. The image capturing apparatus according to claim 1 , wherein the distance computing mechanism comprises
contrast detection means which divides at least one of the first and second images into a plurality of areas, to thus detect contrast of the respective areas;
comparison means for comparing the detected contrast with a reference value; and
selection means for selecting an area where the detected contrast becomes equal to or greater than the reference value, wherein correlation operation of the area selected by the selection means is executed.
9. The image capturing apparatus according to claim 1 , wherein the distance computing mechanism has
detection means for detecting a characteristic area of a subject from at least one of the first and second images, wherein
conversion operation for causing the scaling factor of the first image to coincide with the scaling factor of the second image is performed such that a scaling factor optimal for a scaling factor of the characteristic area of the subject is achieved.
10. The image capturing apparatus according to claim 8 , wherein the characteristic area is a person.