Patent ID: 7619787

Claim:
A document illuminating unit comprising: at least one light source configured to emit light, the at least one light source including a fluorescent lamp and having an opening arranged at an obliquely downward portion of the at least one light source; and at least one reflector configured to reflect the light emitted from the at least one light source, and the at least one reflector is disposed at a position obliquely downward of the at least one light source, the light emitted from the opening of the at least one light source travels via the at least one reflector to illuminate a reading area of a document, and the at least one reflector has a shape of an ellipse to collect the light emitted from the at least one light source, wherein: the reflector is expressed by following formulas; ( X 2 /A 2 )+( Y 2 /B 2 )=1, and ( A>B> 0), and is also expressed by the following formulas; α>sin −1 ( R/D ), and θ=α+β+γ, where “X” represents a major axis of the ellipse, “Y” represents a minor axis of the ellipse, “θ” represents a lean angle of the ellipse with respect to an optical axis in a direction of a plumb line to an document, “α” represents an angle between the major axis of the ellipse and a nearest light ray to the document, “β” represents a light convergent angle, “γ” represents an angle between a farthest light ray from the document and the optical axis in the direction of the plumb line to the document, “R” represents a radius of the fluorescent lamp, and “D” represents a distance between two focal points, and one focal point of the reflector is arranged in a straight line of a center of the fluorescent lamp and a center of the opening and another focal point is arranged in a vicinity of a reading position of the document.