| 摘要 |
PROBLEM TO BE SOLVED: To provide a laser expand optical system capable of removing speckle, and simultaneously illuminating a wide area evenly without lowering a luminous intensity.SOLUTION: A laser expand optical system 1 includes: an input lens 2 for condensing injected laser beam L; and a pin-hole plate 4 having a pinhole 4a disposed in the vicinity of a focal position of the input lens 2. The laser expand optical system 1 has an output lens 6 which causes zero-order diffraction light Lto be parallel light out of diffraction lights diffracted by the pin hole 4a. A focal distance of the input lens 2 is f, a diameter of the laser beam L is Φ, a wavelength of the laser beam L is λ, and a diameter of the pin hole 4a is Φ. A diameter of the pin hole 4a is set to satisfy 2λf/Φ≤Φ≤10[μm] under a condition of 0.067f/(f/Φ)<2.44λf/Φ. |
