Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1998-08-14
2001-01-23
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C359S619000, C359S622000, C359S627000, C359S726000
Reexamination Certificate
active
06177667
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an imaging device, and more particularly to an imaging device which is applicable to reading optical systems of copy machines, facsimile machines and the like, an optical system of a reading scanner having a CCD sensor and a equimagnification sensor and optical systems of an optical printing head and a self-scanning type optical printing head.
2. Description of the related Art
In the recent years, it is required to miniaturize optical equipment, such as a copy machine and an optical printer head. To satisfy this requirement, a reading optical system and/or a writing optical system of the optical equipment have to be miniaturized. Thus, an equimagnification imaging optical system in which a distance between an object and an image can be strongly reduced is under investigation. The equimagnification imaging optical system is defined as an optical system which forms an image having the same size as an object.
A description will now be given of an example of the equimagnification imaging optical system having a conventional configuration.
FIG. 1
illustrates the equimagnification imaging optical system having a conventional configuration. Referring to
FIG. 1
, a roof mirror lens array
103
is formed as the equimagnification imaging optical system. The roof mirror lens array
103
has a lens array
101
and a roof mirror array
102
. The lens array
101
is formed of a plurality of lenses
104
which are arranged in line perpendicular to a a drawing plane of FIG.
1
. the lenses
104
are optically equivalent to each other. The roof mirror array
102
is formed of a plurality of roof mirrors
106
. The roof mirrors
106
are arranged in line so that each of the roof mirrors
106
faces one of the lenses
104
. Each of the roof mirrors
106
has a ridge line
105
. The ridge line
105
is perpendicular to a direction in which the roof mirrors
106
are arranged and an optical axis of each of the lenses
104
. A stop member (not shown) is provided between the lens array
101
and the roof mirror array
102
so that imaging systems, each of which is formed of one of the lenses
104
and a corresponding one of the roof mirrors
106
, are separated from each other.
A reading position P
1
of an original
107
is set at a position which is not on the optical axis of each of the lenses
104
and corresponds to a finite slit height position. Light reflected from the reading position P
1
of the original
107
passes through the each of the lenses
104
so that the light formed of parallel rays. The parallel rays travels to a corresponding one of the roof mirrors
106
and are reflected by the corresponding one of the roof mirrors
106
in the same direction. The light reflected by each of the roof mirrors
106
travels through a corresponding one of the lenses
104
again and is then focused on an imaging position P
2
which is optically conjugate to the reading position P
1
. The position P
2
is, for example, on a surface of a CCD sensor
108
.
An prism lens array is disclosed in Japanese Patent Publication No.61-2929. Into this inprism lens array, a lens array and a roof mirror lens array are integrated. In the same manner as the roof mirror lens described above, a reading position is set at a position corresponding to a finite slit height position. The light reflected at the reading position travels through each of lenses and is then reflected by each of roof prisms twice. The light reflected by the each of the roof prisms travels through a corresponding one of the lenses again and is focused on an imaging position which is optically conjugate to the reading position.
A roof mirror lens array which is the equimagnification imaging optical system is disclosed in Japanese Laid-Open Patent Application No.57-37326. Into this roof mirror lens array, a lens array, a roof mirror array and a stop member are integrated the lens array has lenses which are optically equivalent to each other. The lenses are arranged in line. The roof mirror array has roof mirrors. Each of the roof mirrors faces one of the lenses and has a ridge line. The ridge line is perpendicular to a direction in which the lenses are arranged and to an optical axis of each of the lenses. The stop member is provided between the lens array and the roof mirror array to separate imaging optical systems each of which is formed of a corresponding one of the lenses and a corresponding one of the roof mirrors. The roof mirror lens array may be used to read images and for exposure of a photosensitive member.
In each of the imaging devices as described above, a single imaging system is formed of a lens of the lens array and a roof mirror of the roof mirror array. An aperture of the stop member is provided between corresponding lens and roof mirror to optically separate the imaging system from adjacent imaging systems. In this type of the imaging device, the light travels and returns through the lens. Thus, it is not possible to locate the reading position and the imaging position at the same position. The light rays travels along the optical axis are separated to an object (the original) side rays and imaging point side rays. Thus, the reading position and the imaging position have to be set based on a finite slit height position. That is, the reading position P
1
is set at a finite height position in a direction parallel to the ridge line
105
of each of the roof mirrors
106
. The imaging position P
2
is set at the finite height position in the reverse direction.
Since the amount of separation of the light rays is limited, separation mirrors
109
(
1
) and
109
(
2
) are used to set the reading position P
1
and the imaging position P
2
as shown in FIG.
1
. The light traveling from the reading position P
1
is reflected by the separation mirror
109
(
1
) and travels to a corresponding one of the lenses
104
. The light passing through each of the lenses
104
is reflected by the separation mirror
109
(
2
) and focused on the imaging position. Each of the separation mirrors
109
(
1
) and
109
(
2
) is a rectangular plane mirror which expands in a direction perpendicular to the drawing plane of FIG.
1
. Each of the separation mirrors
109
(
1
) and
109
(
2
) are arranged so as to be inclined by 45° with respect to a plane including optical axes &phgr; of the lenses
104
of the lens array
101
.
In the conventional imaging device having a roof mirror lens or a roof mirror lens array, the light passes through the same lens
104
twice, and the reading position P
1
(a reading plane) and the imaging position P
2
(an imaging plane) are located in the opposite sides with respect to the optical axis &phgr; of the lens
104
. The separation mirrors
109
(
1
) and
109
(
2
) are provided in optical paths between the reading position P
1
and the lens
104
and between the lens
104
and the imaging position P
2
.
The surfaces of each roof mirror and the separation mirrors
109
(
1
) and
109
(
2
) are provided with reflecting films which are formed of high reflecting material, such as aluminum (Al), by a vacuum evaporation process. The reflectivity of each of the reflecting films is about 90%. In the imaging device having the above structure as shown in
FIG. 1
, there are two reflecting surfaces of each of the roof mirrors
106
and two reflecting surfaces of the respective separation mirrors
109
(
1
) and
109
(
2
). Thus, the total reflectivity of is about 66%. The loss of the amount of light in the imaging device is large. In addition, in the conventional case, the light pass through the same lens
104
twice, so that the reading position P
1
and the imaging position P
2
have to be adjacent and to be symmetrical to each other with respect to the optical axis &phgr;. Thus, stray light, such as reflected light from the surface of the lens
104
and from surfaces other than the reflecting surface of the roof mirror
106
, may be incident on the imaging position P
2
at a high possibility. Such stray light affects characteristics o
Akanuma Goichi
Fujita Kazuhiro
Inoue Hiroyuki
Maeda Ikuo
Lee John R.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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