Patent ID: 7856126

Claim:
A lens apparatus comprising: a lens movable in a direction of an optical axis; a lens driving unit configured to move the lens in the direction of the optical axis; a first position sensing unit configured to output a plurality of detection signals that periodically change in accordance with movement of the lens; a second position sensing unit configured to detect a reference position of the lens; and an arithmetic unit configured to compute a relative position of the lens in relation to the reference position, wherein the arithmetic unit is configured to compute first position data indicating the reference position based on the plurality of detection signals, to compute a difference included in the first position data based on a phase of the plurality of detection signals, and to compute corrected first position data, in which the difference is corrected, based on the first position data and the difference, when the lens is at the reference position, wherein the arithmetic unit is configured to compute second position data indicating an arbitrary position based on the plurality of detection signals, to compute a difference included in the second position data based on a phase of the plurality of detection signals, and to compute corrected second position data, in which the difference is corrected, based on the second position data and the difference, when the lens is at the arbitrary position, wherein the arithmetic unit is configured to compute the relative position of the lens in relation to the reference position based on the corrected first and second position data, and wherein the difference included in the first position data and the difference included in the second position data are obtained from the following equation: E = A ⁢ ⁢ sin ⁢ ⁢ θ - 2 ⁢ 2 ⁢ A λ ⁢ θ ⁢ ⁢ where ⁢ ⁢ ( - λ 4 ≤ θ ≤ λ 4 ) ( 1 ) where, E is the difference of a reference position, A is the amplitude of the plurality of detection signals, θ is the phase, and λ is the wavelength of the plurality of detection signals.