The present invention relates to a distance measuring apparatus including an imaging device and a calculation unit calculating a distance to a subject on the basis of an electrical signal. The imaging device includes a signal acquisition unit that acquires a first electrical signal based on a beam t
The present invention relates to a distance measuring apparatus including an imaging device and a calculation unit calculating a distance to a subject on the basis of an electrical signal. The imaging device includes a signal acquisition unit that acquires a first electrical signal based on a beam that has passed through a first region off the center of the exit pupil in a predetermined direction; a second electrical signal based on a beam that has passed through a second region off the center of the exit pupil in a direction opposite to the predetermined direction; and a third electrical signal based on a beam that has passed through a region eccentric from the first region in the direction opposite to the predetermined direction. The calculation unit performs a signal correction process for generating a first corrected signal and a distance calculation process for calculating the distance.
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1. A distance measuring apparatus comprising: an optical system forming an image of a subject;an imaging device acquiring an electrical signal from a beam that has passed through an exit pupil of the optical system; anda calculation unit calculating a distance to the subject on the basis of the elec
1. A distance measuring apparatus comprising: an optical system forming an image of a subject;an imaging device acquiring an electrical signal from a beam that has passed through an exit pupil of the optical system; anda calculation unit calculating a distance to the subject on the basis of the electrical signal,wherein the imaging device includes a signal acquisition unit acquiring a first electrical signal mainly based on a beam that has passed through a first region off the center of the exit pupil in a predetermined direction;a second electrical signal mainly based on a beam that has passed through a second region off the center of the exit pupil in a direction opposite to the predetermined direction; anda third electrical signal different from the second electrical signal on the basis of a beam that has passed through a third region off the first region in the direction opposite to the predetermined direction, andwherein the calculation unit performs a signal correction process for generating a first corrected signal by subtracting the third electrical signal from the first electrical signal in a predetermined proportion and a distance calculation process for calculating the distance by using the first corrected signal in a phase-difference detection method. 2. The distance measuring apparatus according to claim 1, wherein, in the signal correction process, the first corrected signal is generated on the basis of Exp. 3, S1′=S1−αS3 (Exp. 3) where S1′ is the first corrected signal, S1 is the first electrical signal, S3 is the third electrical signal, and α is a positive value that causes S1′ to have no negative value. 3. The distance measuring apparatus according to claim 1, wherein the signal acquisition unit further acquires a fourth electrical signal different from the first electrical signal mainly on the basis of a beam that has passed through a forth region off the second region to the predetermined direction;in the signal correction process, a second corrected signal is further generated by subtracting the fourth electrical signal from the second electrical signal in a predetermined proportion; andin the distance calculation process, the distance is calculated using the first corrected signal and the second corrected signal. 4. The distance measuring apparatus according to claim 3, wherein, in the signal correction process, the second corrected signal is generated on the basis of Exp. 5, S2′=S2−βS4 (Exp. 5)where S2′ is the second corrected signal, S2 is the second electrical signal, S4 is the fourth electrical signal, and β is a positive value that causes S2′ to have no negative value. 5. The distance measuring apparatus according to claim 3, wherein the signal acquisition unit generates electric signals in accordance with a quantity of a beam;the third electrical signal is a signal having a higher S/N ratio than the S/N ratio of the second electrical signal; andthe fourth electrical signal is a signal having a higher S/N ratio than the S/N ratio of the first electrical signal. 6. The distance measuring apparatus according to claim 3, wherein the signal acquisition unit includes first, second, third, and fourth light receiving portions that acquires the first, second, third, and fourth electrical signals, respectively. 7. The distance measuring apparatus according to claim 1, wherein the third electrical signal is an electrical signal different from the second electrical signal, the third electrical signal being acquired mainly on the basis of, among beams that have passed through a pupil region through which a beam corresponding to the first electrical signal passes, a beam that has passed through the third region off the first region in the direction opposite to the predetermined direction. 8. The distance measuring apparatus according to claim 3, wherein the fourth electrical signal is an electrical signal different from the first electrical signal, the fourth electrical signal being acquired mainly on the basis of, among beams that have passed through a pupil region through which a beam corresponding to the second electrical signal passes, a beam that has passed through the forth region off the second region to the predetermined direction. 9. The distance measuring apparatus according to claim 3, wherein the signal acquisition unit includes first and second light receiving portions acquiring the first and second electrical signals, respectively; andthe third and fourth electrical signals are generated by the first and second light receiving portions mainly on the basis of beams that have passed through the first region and the second region, respectively. 10. The distance measuring apparatus according to claim 3, wherein the signal acquisition unit includes a first light receiving portion and a fifth light receiving portion;the third and fourth electrical signals are acquired by the fifth light receiving portion;the first electrical signal is acquired by the first light receiving portion; andthe second electrical signal is a signal generated by subtracting the first electrical signal from the electrical signal acquired by the fifth light receiving portion. 11. The distance measuring apparatus according to claim 6, wherein the imaging device includes a plurality of pixels having the light receiving portions; andthe light receiving portions are disposed in three adjacent pixels. 12. The distance measuring apparatus according to claim 3, wherein the calculation unit further performs a corrected-base-length calculation process for calculating a corrected base length on the basis of regions on the exit pupil through which beams corresponding to the first and second corrected signals pass; andin the distance calculation process, the distance is calculated using the correct base length and the corrected signal. 13. The distance measuring apparatus according to claim 4, wherein the signal correction process includes a correction-factor adjusting process for adjusting the correction factors depending on the shape of the exit pupil, the distance between the exit pupil and the imaging device, or positions on the imaging device. 14. The distance measuring apparatus according to claim 4, wherein the calculation unit further performs a signal modification process for generating first and second modification filters expressed by Exp. 15 and Exp. 17 and performing convolution integral of the first corrected signal and the second modification filter and convolution integral of the second corrected signal and the first modification filter to generate a first modified signal and a second modified signal, respectively; andthe distance calculation process is a process for calculating the distance by using the first modified signal and the second modified signal instead of the first corrected signal and the second corrected signal, L1′=L1−αL3 (Exp. 15)L2′=L2−βL4 (Exp. 17)where L1′ and L2′ are the first and second modification filters, L1, L2, L3, and L4 are line spread functions determined depending on the signal acquisition units for the first, second, third, and fourth signals and the optical system, and α and β are the correction factors. 15. An image acquisition unit comprising the distance measuring apparatus according to claim 1. 16. The image acquisition unit according to claim 15, wherein the distance measuring apparatus detects the focus of the optical system on the basis of the result of distance measurement of the distance measuring apparatus. 17. The image acquisition unit according to claim 15, wherein the image acquisition unit acquires a distance image by using the distance measuring apparatus. 18. A method for measuring a distance, comprising the steps of: acquiring a first electrical signal mainly based on a beam that has passed through a first region off the center of an exit pupil of an optical system in a predetermined direction;acquiring a second electrical signal mainly based on a beam that has passed through a second region off the center of the exit pupil in a direction opposite to the predetermined direction;acquiring a third electrical signal different from the second electrical signal on the basis of a beam that has passed through a third region off the first region in the direction opposite to the predetermined direction;generating a first corrected signal by subtracting the third electrical signal from the first electrical signal in a predetermined proportion; andcalculating the distance by using the first corrected signal in a phase-difference detection method. 19. A non-transitory storage medium recording a program for causing a computer for calculating, in a distance measuring apparatus including an optical system forming an image of a subject and an imaging device acquiring an electrical signal from a beam that has passed through an exit pupil of the optical system, a distance to a subject by using a first electrical signal mainly based on a beam that has passed through a first region off the center of the exit pupil in a predetermined direction, a second electrical signal mainly based on a beam that has passed through a second region off the center of the exit pupil in a direction opposite to the predetermined direction, and a third electrical signal different from the second electrical signal, the third electrical signal being based on a beam that has passed through a third region off the first region in the direction opposite to the predetermined direction, to execute a signal correction process for generating a first corrected signal by subtracting the third electrical signal from the first electrical signal in a predetermined proportion and a distance calculation process for calculating the distance by using the first corrected signal in a phase-difference detection method.
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