A liquid pressure varifocus lens has been developed that employs a fibrous actuator which contracts on application of a
current or on heating. The focal length of the convex lens can be varied continuously between 90 mm to 300 mm. The
shape of the lens changes smoothly and the construction of the lens is extremely simply. It requires a low electric power
to drive it. In this study, the optical characteristics and the response time of the liquid pressure varifocus lens were
measured. The time constant of the fibrous actuator was 1.0 s for the rise time when electric power was initially supplied.
A fibrous actuator having a length of 370 mm was used, and a voltage of 9.5 V was applied.
A varifocus lens by liquid pressure has been developed to change the focal length from a concave to a convex shape by adjusting the liquid pressure. It consists of a polymer film, an acrylic plate, and liquid and it is filled up with the liquid in its cavity. The deformation of the refraction surface of the lens is analyzed theoretically. An experiment by He-Ne laser is performed with a plano-convex type lens. The dynamic range of the focal length of the convex lens is from 50 mm to 250mm. The application for a YAG laser with 1.06μm of wavelength is demonstrated experimentally. The focus was adjusted along the material surface without moving the optical element. As a result, the control of the beam spot diameter is succeeded. Finally, the laser processing is demonstrated to manufacture Fe compressed powder sheets. Its melting marks along a focus change are formed with a minimum width of 100μm.
This paper describes a surface profile measurement using a varifocus lens by an optical sectioning. The focus method is utilized for a uni-axis optical system of projection and observation. The varifocus lens is mounted on between a liquid crystal grating and a projection lens. A focus length can be continuously varied from a concave to a convex shape by changing the liquid pressure. The contrast of projected pattern onto the sample is approximated the Gauss distribution along the distance and indicates sharpest at the focused plane. It is possible to analyze the contrast distribution by a grating projected method using a liquid crystal grating with 4 steps phase-shifting method. The liquid crystal grating is powerful tool to make arbitrary intensity and frequency distribution. Surface profiles of mechanical parts have been measured to demonstrate for this method.
A method for a beam shaping optics is proposed to convert a laser beam profile into required intensity distribution. A beam shaper with aspherical surface is calculated by Snell's law converted from measured irradiate beam profile to required profile. An acrylic resin is cut by a ball type grinding wheel consisted on diamond powder and polished by a cone type felt buff with alumina ceramics powder. A CNC lathe is used to control these tools position. A shaper with 4mm of thickness works to convert multi-mode beam profile with 13mm of diameter into a flat top cylinder with 1mm of diameter. Its working distance is 60mm. Its transmittance is over 98%.It suceed to generate uniform melting mark of 0.6mm diameter on the steel target by YAG laser process.