An X-ray phase grating used for X-ray phase-contrast imaging based on Talbot interference includes a first substrate and a second substrate. The oil strainer assembly includes a strainer element and a housing. When the character determining part determines the character, the display part displays the determined character. Alternative calibration procedures are provided if the battery is not completely discharged before charging or if the battery is not fully charged by the charging process. A gap-filling material is refilled into the trench and over the semiconductor substrate.