Abstract: A laser pick-up device for an optical disk receives three laser beams to irradiate the optical disk and uses a six-division optical detector to detect the laser beams reflected from the optical disk and to track exactly the optical disk. A reflection type diffraction grating is positioned at a front position in order to divide and reflect the laser beam generated by a laser diode. A holographic element having the function of a toric lens is used as a diffracting device for the reflected beams. The six-division optical detector is positioned to one side and/or behind the diffraction grating. The grid gaps of the holographic element can be larger using the present invention which simplifies the manufacturing the holographic element and thereby provides a laser pick-up device that is suitable for mass production.

Abstract: A float operated valve is provided with the rise of a float being temporarily prevented by the elastic force of a spring mounted on the valve body. When the buoyant force of the float reaches a predetermined maximum buoyant force as a result of the water level rising and the float becoming increasingly submerged, the buoyant force of the float moves the spring and closes the valve. The valve is also shown with a twin float construction for on/off operation at low and high water levels.