Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
1999-10-07
2002-03-26
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S628000, C359S630000, C359S631000
Reexamination Certificate
active
06362921
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical element having an entrance refractive surface, an exit refractive surface and internal reflective surfaces, a holding structure for the optical element, and an image pickup apparatus.
2. Description of Related Art
Image pickup in electronic still cameras or video cameras is performed by converting an object image formed on an image pickup element (hereinafter represented as a CCD, by way of an example) by an optical system into electrical signals by means of the CCD.
A range within which a sufficiently sharp image for actual usage is available before and behind the best imaging point by the optical system is called the depth of focus. To perform image pickup without defocusing or partial-defocusing, it is necessary to position a plane of the CCD within the depth of focus. The optical system and image pickup system having the autofocus mechanism conduct adjustment of the position of a lens group by detecting the focus in order to position the CCD plane always within the depth of focus. On the other hand, the optical system and image pickup system having no autofocus mechanism require the back-focus adjustment for adjusting the distance of the CCD plane with respect to the optical system.
The back-focus adjustment is performed, for example, in the adjustment step during the assembly process by using jigs and tools, or after the assembly process by integrating an adjustment mechanism within the holding member for the CCD.
The former of the above-described back-focus adjustment has such disadvantages that replacement or recycling of the CCD is not possible because the CCD is completely fixed by adhesives after adjustment, and the adjustment step takes much time.
Now, an example of the latter of the above-described back-focus adjustment is shown in
FIGS. 9A and 9B
.
FIG. 9A
is a sectional view showing a cross-section of a typical single-focus lens unit and image pickup system along a plane including the optical axis. In
FIG. 9A
, the CCD is not represented by a cross-section.
FIG. 9B
is a plan view of the back-focus adjustment mechanism for the CCD, as viewed in the direction of arrows on a plane represented by the two-dotted chain line in FIG.
9
A. In
FIGS. 9A and 9B
, reference numeral
101
denotes a lens group composed of a plurality of lens elements, reference numeral
102
denotes a lens barrel for holding the lens group
101
and blocking light, reference numeral
103
denotes optical correction plates having a quartz low-pass filter and an infrared-cutting filter, reference numeral
104
denotes a CCD, reference numeral
104
a
denotes an image pickup plane of the CCD
104
, reference numeral
104
b
denotes a corner portion of the image pickup plane
104
a
, reference numeral
105
denotes a CCD holding plate made of metal for holding the CCD
104
, reference numeral
106
denotes a CCD circuit board for transmitting image signals to a flexible cable
108
, etc., by electrically connecting terminals of the CCD
104
with soldering, etc, reference numeral
107
denotes an insulating member for insulating the CCD holding plate
105
from the CCD circuit board
106
, reference numeral
109
denotes a base plate for holding the CCD holding plate
105
so as to allow adjustment of back-focus and tilt with respect to the lens barrel
102
, reference numeral
109
a
denotes positioning holes for regulating the position of the base plate
109
with respect to the lens barrel
102
, and reference numeral
109
b
denotes tapped holes for fastening the base plate
109
to the lens barrel
102
by screws. Reference numeral
110
denotes a back-focus feed screw for back-focus adjustment, reference numerals
111
and
112
denote a spring and an urging screw, respectively, for urging the CCD holding plate
105
toward the base plate
109
, and reference numeral
113
denotes tilt adjusting screws for adjusting tilts around the x axis and y axis of the CCD holding plate
105
.
The back-focus feed screw
110
engages with a tapped hole of the base plate
109
with the tip of the back-focus feed screw
110
in contact with the CCD holding plate
105
. In an example shown in
FIG. 9A
, the tip of the back-focus feed screw
110
is arranged so as to come into contact with the rear side of the CCD holding plate
105
at a point corresponding to the corner portion
104
b
of the image pickup plane
104
a
of the CCD
104
. The CCD
104
is fixed to the CCD holding plate
105
by bonding, etc., after positioning by a jig. The CCD holding plate
105
is moved by the back-focus feed screw
110
in directions for changing the distance from the optical system. More specifically, turning clockwise the back-focus feed screw
110
causes the CCD holding plate
105
to move toward the lens group
101
, thereby decreasing the back-focus. Conversely, turning counterclockwise the back-focus feed screw
110
causes the CCD holding plate
105
to move away from the lens group
101
, thereby increasing the back-focus.
Furthermore, the tilt of the CCD holding plate
105
is adjusted by the urging screw
112
and the two tilt adjusting screws
113
. The urging screw
112
engages with a tapped hole of the CCD holding plate
105
, and can freely move with respect to the base plate
109
along the axial direction thereof with positional restriction only in the direction of the plane of the base plate
109
. The spring
111
is held in a compressed state between the urging screw
112
and the base plate
109
with the head of the urging screw
112
utilized, so as to apply an urging force to move the urging screw
112
in the direction away from the lens group
101
by a force of repulsion of the spring
111
. This urging force causes a rotational moment working on the CCD holding plate
105
with the tip of the back-focus feed screw
110
acting as a fulcrum, but the tilt of the CCD holding plate
105
is restricted by two tilt adjusting screws
113
. More specifically, the tilt adjusting screws
113
engage with tapped holes of the CCD holding plate
105
but can freely move with respect to the base plate
109
, so that the tilt adjusting screws
113
are pulled in by the moment working on the CCD holding plate
105
to regulate the position of the CCD holding plate
105
at the location where the heads of the tilt adjusting screws
113
come into contact with the base plate
109
. At this time, if an axis parallel to the longer side of the CCD image pickup plane
104
a
is set as the x-axis and an axis parallel to the shorter side as the y-axis out of axes passing through the corner portion
104
b
of the CCD image pickup plene
104
a
, the tilt adjusting screws
113
are disposed on the x-axis and the y-axis, respectively, to rotate the CCD holding plate
105
around the x-axis or the y-axis by turning either one of the tilt adjusting screws
113
. Arranging the back-focus feed screw
110
and the tilt adjusting screws
113
in the above-described way allows performing adjustment readily in the directions around the x-axis or the y-axis independently.
Conducting the above operation while monitoring image signals from the CCD
104
generated by picking up an image of an evaluation chart allows performing adjustment of back-focus and tilt of the CCD
104
. However, in the above-described back-focus adjustment method, the fulcrum of the CCD holding plate
105
shifts its position when the back-focus adjustment is performed. Therefore, the tilt adjustment is required always after the back-focus adjustment, so that it is impossible to perform the back-focus adjustment independently of the tilt adjustment.
Also, as shown in
FIG. 9A
, the lens group
101
is positioned in the direction perpendicular to the optical axis by the inner periphery of the lens barrel using the outer peripheries of the lens group
101
and in the direction along the optical axis by bringing the refractive surfaces of the lens group
101
into contact with the steps formed inside the lens barrel, and is then fastened by bonding or by a
Iida Seiji
Kawano Kenji
Uehara Tsukasa
Canon Kabushiki Kaisha
Epps Georgia
Lucas Michael A.
Robin Blecker & Daley
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