Abstract: There is provided an optical low pass filter passing only a lower spatial frequency using a phase grating and the structure of the grating. The optical low pass filter utilizes the two-dimensionally arranged phase grating for the purpose of removing an image with a higher spatial frequency in an imaging system employing a semiconductor solid-state imaging device such as CCD image sensor or CMOS image sensor, The optical low pass filter which suppresses a spatial frequency component higher than a specific frequency and passes a component lower than the specific frequency in an imaging system sensing input images includes a grating generating the phase shift of 0, a grating generating the phase shift of &phgr;, arranged at the right and bottom of the 0-phase shift grating, and a grating generating the phase shift of 2&phgr;, arranged at the diagonal side of the 0-phase shift grating.

Abstract: There is a provided a method for fabricating a grating pattern, including the steps of: coating an SOG solution on a glass substrate by spin coating method; heat-treating the SOG thin film coated on the glass substrate, to form a silicon oxide layer; coating a photoresist on the silicon oxide layer and exposing the photoresist layer by masking process; developing the exposed photoresist layer and wet-etching the silicon oxide layer; and developing the photoresist layer used as a mask. According to the present invention, the grating pattern can be fabricated without etching the glass substrate, and high-quality products at a low cost is accomplished since the present invention does not require the expensive sputtering apparatus. Furthermore, the step-shape oxide layer pattern can be obtained through one-time wet etching since the multilevel oxide layer is easily formed.