Patent ID: 7593113

Claim:
An undistorted imaging apparatus for light speckles, comprising: a light-emitting device, emitting light to an object surface, and producing one or more rays of scattered light; a light-limiting module, comprising a plurality of light-limiting members for limiting said one or more rays of scattered light and producing a plurality of rays of diffraction light, which interferes with each other and produces a plurality of light speckles, said plurality of light-limiting members for limiting the incident angle field of view at which said one or more rays of scattered light enter a sensor, each having a linear dimension of the field of view for an undistorted image being less than d max ≈ λ 5 · γ 4 ⁢ ⁢ δ ⁢ ⁢ cos 3 ⁢ ⁢ θ , where: λ=is the wavelength of the highly coherent light, 2δ=is the average diameter of the light speckles, 2γ=is the distance between the sensor and the object surface, θ=is the angle between the optical axis of the imaging apparatus and the normal of the object surface; and said sensor, adapted behind the light-limiting module, receiving the plurality of light speckles, and producing a light-speckle pattern according to the plurality of light speckles.