Back to results
US 6,687,060 B2Granted
Reading optical system
AssigneeMinolta Co., Ltd.
InventorsKazuharu Kagoshima, Makoto Ooki
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeMinolta Co., Ltd.
InventorsKazuharu Kagoshima, Makoto Ooki
Estimating the term…
A reading optical system for projecting a document image on a CCD in an image reading device, providing, sequentially from the document side, a symmetrical lens group rotatable about the optical axis, and a free curved mirror. Reflective surface shape of the free curved mirror is symmetrical in a plane perpendicular to the linear layout direction of the line CCD and includes the intersection of the optical axis of the lens group and the reflective surface of the free curved mirror. The reflective surface shape of the free curved mirror is asymmetrical in a plane parallel to the linear layout direction of the line CCD and includes the normal line (NL) at the intersection. The number of lenses of the lens group structure can be reduced to three lenses while maintaining a high optical performance by using such a free curved mirror.
A reading optical system for projecting a document image on a linear image sensing device, said reading optical system comprising:
An optical system for projecting an image on a linear image sensing device, said optical system comprising:
An optical system according to 3, wherein said mirror is arranged outside of said lens group.
A reading optical system for projecting a document image on a linear image sensing device, said reading optical system comprising:
Dependencies are inferred from the claim text.
Drawings are temporarily unavailable. Open the PDF at USPTO
From the US filing history. Foreign family members aren’t listed.
Catadioptric systems: having a field corrector only
Systems with reflecting surfaces, with or without refracting elements: catadioptric systems
Optical elements, systems or apparatus
Term ended 12 Jan 2022 (estimated)
1. Field of the Invention
The present invention relates to a reading optical system. For example, the present invention relates to a reading optical system suitable for an image reading device (particularly facsimile and digital copier) provided with a linear image sensing device such as a line CCD (charge-coupled device).
2. Description of the Related Art
FIG. 1 shows the YZ cross section of an embodiment of the reading optical system.
FIG. 2 shows the XZ cross section of an embodiment of the reading optical system.
FIG. 3 shows the distortion in the embodiment.
In the following description, like parts are designated by like reference numbers throughout the several drawings.
The embodiments of the reading optical system of the present invention are described hereinafter with reference to the drawings. FIGS. 1 and 2 show the optical structure of an embodiment of the reading optical system; FIG. 1 shows the optical structure in the YZ cross section in mutually intersecting X, Y, and Z directions, and FIG. 2 shows the optical structure in the XZ cross section. In FIGS. 1 and 2, surfaces with the Si (i=1, 2, 3, . . . ) appended are the No. i surface counting from the object side (i.e., document side), and surface (S8) with the star symbol appended is a reflective mirror surface having a free curve.
This embodiment is a reading optical system used in an image reading device (facsimile, digital copier or the like) provided with a line CCD (SR) as a linear image sensing device, and has arranged, sequentially from the object side, a symmetrical lens group (GR) rotatable relative to the optical axis (AX), and a free curved mirror (MR). The lens group (GR) has, sequentially from the object side, a first lens (G1) comprising a concave positive meniscus lens element on the object side, a second lens (G2) comprising a biconcave negative meniscus lens element, a stop (ST), and a third lens (G3) comprising a biconvex positive lens element. The reflective surface (S8) of the free curved mirror (MR) comprises a free curved surface having a concave shape on the object side. The plate (PL) disposed nearest the image plane (IM) side is a cover glass of the line CCD (SR). In this image reading device, a document image is reduced and projected for reading on the line CCD (SR). The optical axis (AX) of the lens group (GR) is parallel to the Z direction, and perpendicular to the XY plane. The linear layout direction (i.e., a direction in line with the photoreceptor element comprising each pixel) of the line CCD (SR) is parallel to the Y direction.