Surgery – Endoscope – Having imaging and illumination means
Reexamination Certificate
2002-08-23
2004-07-06
Leubecker, John P. (Department: 3739)
Surgery
Endoscope
Having imaging and illumination means
C600S117000, C348S240100
Reexamination Certificate
active
06758807
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the priority of Japanese Patent Applications Nos. 2001-255846 filed on Aug. 27, 2001 and 2001-299228 filed on Sep. 28, 2001, which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an electronic endoscope with a power scaling function and, more particularly, to power scaling operation control of an electronic endoscope capable of observing an optically magnified image by a movable lens and forming an electronically magnified image through signal processing.
2. Description of the Related Art
An electronic endoscope, etc. in recent years has an objective lens system at the tip of its scope provided with a power scaling movable lens and drives this movable lens using an actuator, etc. to optically magnify an image of an object under observation. This optically enlarged image is picked up by an image pick-up element such as a CCD (Charge Coupled Device), and various types of image processing are performed by a processor based on the output signal from the CCD, by which an enlarged image of a subject to be observed is displayed on a monitor. In such an optical variable power mechanism, an observed image can be enlarged up to about 70 to 100 times.
On the other hand, conventionally, the image obtained by the CCD is enlarged electronically by picture element interpolation processing etc. of an electronic variable power circuit. According to this, the optically enlarged image can be further enlarged and displayed on the monitor for observation.
The power scaling function of such an electronic endoscope electronically magnifies an image which has been optically magnified under an arbitrary magnification using optical power scaling and electronic power scaling switches respectively or operates by associating optical power scaling with electronic power scaling using a common power scaling switch of an endoscope operation section. When this common power scaling switch is used, the movable lens is moved to the magnification end (near end) by optical power scaling, and then optical power scaling is automatically changed to electronic power scaling to form a further magnified image through signal processing, which makes it possible to observe specific areas such as affected areas speedily and under an optimal magnification.
SUMMARY OF THE INVENTION
However, the optical power scaling mechanism using a movable lens in the above-described conventional electronic endoscope has a smaller depth of field as the magnification increases and there are cases where the electronic endoscope cannot optimally display an overall image of an object under observation with an uneven surface in the depth direction. This phenomenon will be described now with reference to
FIGS. 12 and 13
.
In
FIG. 12
, the left-hand side view shows a state in which when a movable lens
1
lies at the Far end, the proximal end, a subject to be observed
2
forms an image on a CCD image pick-up surface
3
, and the right-hand side view shows an image formation state at the time when the moving lens
1
is moved to the Near side, the enlargement side. In
FIG. 12
, since the moving lens
1
is set at a position of distance
0
, at the time of enlargement, the image pick-up surface
3
is drawn so as to be shifted rearward. Actually, the moving lens
1
moves forward. When the optical enlargement is not made as shown in the left-hand side view of
FIG. 12
, the focus is sharpened, for example, at a distance of 8 to 100 mm, and the depth of field is 92 mm. Whereas, when the optical enlargement is made as shown in the right-hand side view in
FIG. 12
, the focus is sharpened at a distance of 4 to 20 mm, and the depth of field is 16 mm.
FIG. 13
is an explanatory view of the depth of field. Taking the focal length of a lens
4
as f, the F number as F
N
, the allowable blur circle as &dgr;, and the distance of subject to be observed as L, the rear depth of field L
r
and the front depth of field L
f
are expressed as follows:
L
r
=(&dgr;·
F
N
·L
2
)/(
f
2
−&dgr;·F
N
·L
) (1)
L
f
=(&dgr;·
F
N
·L
2
)/(
f
2
+&dgr;·F
N
·L
) (2)
The depth of field of this lens
4
is a value obtained by summing up the rear depth of field L
r
and the front depth of field L
f
, that is, L
r
+L
f
. The depth of focus is 2&dgr;·F
N
.
The aforementioned depth of field explained in
FIG. 12
is also the above-described value of L
r
+L
f
, and the range in which the focus is sharp is 92 mm at the Far end and 16 mm at the Near end. In the configuration of variable power objective optical system now used for an endoscope, the depth of field decreases as the image is enlarged. Therefore, in the case where a subject to be observed having irregularities is observed, the depth of field becomes shallow (short), so that a blur occurs somewhere in the depth direction. When the subject to be observed caught in a state of shallow depth of field is enlarged electronically, the blur in the depth direction is also enlarged, which presents a problem in that the whole of the subject to be observed cannot be displayed and observed with high picture quality.
The present invention has been implemented in view of the above-described problem and it is an object of the present invention to provide an electronic endoscope having a power scaling function capable of eliminating blurring in the depth direction by switching only the depth of field to an optimal value and smoothly observing an image.
To attain the above-described object, the present invention is characterized by including an objective optical system that optically scales power of an image under observation using a power scaling lens, an electronic power scaling circuit that electronically scales the image obtained through an image pickup element through signal processing, depth operating means that changes the depth of field at the optical power scaling to an arbitrary value and a control circuit that drives and controls the objective optical system so that the objective optical system is set to the depth of field selected by the operation of this depth operating means and controls the electronic power scaling operation of the electronic power scaling circuit so that it maintains the magnification of the image immediately before the depth operation.
Since the depth of field is specified by the position of the movable lens to magnify the image, the depth of field can also be recognized by the optical magnification. According to the above-described configuration, assuming that a predetermined depth of field (e.g., depth equivalent to ×60) is selected by the depth operating means when an image is magnified to ×72, for example, through optical power scaling, ×1.2 is set by electronic power scaling. This makes it possible to display a magnified image under the same magnification as that immediately before the depth operation. Furthermore, assuming that the depth of field value is 7 mm under ×72 and 12 mm under ×60 as described above, it is possible to widen the sharply focused range 5 mm in the depth direction and observe a magnified image focused within a desired range.
Furthermore, the control circuit can be controlled so that it does not electronically scale power beyond a preset allowable magnification range when the depth of field is changed to an arbitrary value.
The depth operating means can be constructed by including a selection switch that selects a plurality of preset depth of field values and a variable switch to change the depth of field values selectable by this switch. Furthermore, this depth operating means can also be made to increase the depth of field from the immediately preceding value by a predetermined amount when a depth of field change operation is performed.
Another embodiment of the present invention is characterized by including an objective optical system that optically scales an image under observation using a power scaling lens, an electronic power scaling circuit that electronically scales the image obtained th
Fuji Photo Optical Co., Ltd.
Leubecker John P.
Snider Ronald R.
Snider & Associates
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