Photocopying – Projection printing and copying cameras
Reexamination Certificate
1998-02-19
2001-06-26
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
C355S069000, C355S077000
Reexamination Certificate
active
06252645
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image reading apparatus for reading an image recorded on an original such as a film.
2. Description of the Related Art
In recent years, the following technique has developed. That is, an image obtained by reading a film image serving as an original by a film scanner or the like is displayed on a display, and a user edits and processes the image to obtain a preferable image. The frequency of transmission of image data of a film image to a communication destination by using a communication device rapidly increases. As a method of reading a film image, the following methods are generally used. That is, a film original is irradiated by an illumination light source from one side of the film original to directly read a transparent film image from an area sensor, or a film image is read by causing a high-density line sensor to mechanically scan the film image.
Here, as an example of a conventional image reading apparatus, a film scanner for reading the image of a transparent original (film) will be exemplified. A conventional film scanner which reads an image recorded on a film to input the image to a personal computer has been mainly developed for a 35 mm standard film. When an image is to be read by such a film scanner, scanning (pre-scanning) at a low resolution, and an image obtained by this scanning is displayed on a personal computer as a preview screen. Thereafter, the film scanner is instructed to main-scan a desired read range designated on the preview screen. The film scanner main-scans the desired range of the indicated image to transmit image data obtained by this scanning to the personal computer.
FIG. 30
is a schematic view showing the arrangement of a conventional film scanner. Referring to
FIG. 30
, reference numeral
1101
denotes an original table (film carriage), and reference numeral
1102
denotes a developed film which is fixed to the original table
1101
. Reference numeral
1103
denotes a lamp serving as a light source;
1104
, a mirror;
1105
and
1106
, lenses;
1107
, a line sensor constituted by a CCD (Charge Coupled Device); and
1108
, an aperture unit whose aperture can be mechanically adjusted.
Reference numeral
1109
denotes a motor for moving the original table
1101
in a scanning direction;
1110
, a motor for adjusting the aperture of the aperture unit
1108
;
1111
, a control circuit; and
1113
, a sensor for detecting the position of the original table
1101
.
The lamp
1103
, the line sensor
1107
, the motors
1109
and
1110
, and the sensor
1113
are electrically connected to the control circuit
1111
, and the control circuit
1111
controls determination and adjustment of an aperture, movement of the original table
1101
, ON/OFF of the lamp
1103
, and the like. Light irradiated from the lamp
1103
passes through the developed film
1102
along an optical axis
1112
, is reflected by the mirror
1104
, and then passes through the lenses
1105
and
1106
and the aperture unit
1108
to reach the line sensor
1107
.
A method of reading image information from the developed film
1102
by using the film scanner
30
will be described below.
The control circuit
1111
causes the motor
1110
to drive the aperture unit
1108
such that the aperture of the aperture unit
1108
is set in a predetermined standard state, and turns on the lamp
1103
. The control circuit
1111
causes the sensor
1113
to detect the position of the original table
1101
, rotates the motor
1109
to scan the image of the developed film
1102
, and then moves the original table
1101
toward the film surface. The control circuit
1111
causes the line sensor
1107
to read light transmitted through the developed film
1102
.
Here, the control circuit
1111
determines the aperture of the aperture unit
1108
not to saturate electric charges in the light-receiving element of the line sensor
1107
, and causes the motor
1110
to adjust the aperture of the aperture unit
1108
to the determined aperture. Upon completion of the adjustment, the original table
1101
is moved by the motor
1109
toward the film surface to scan the video image range of the film
1102
, and light emitted from the lamp
1103
and passing through the film
1102
is received by the line sensor
1107
. A video signal output from the line sensor
1107
in accordance with the received light is transmitted to the control circuit
1111
. Upon completion of the scanning for the video image range of the film
1102
, the control circuit
1111
turns off the lamp
1103
and drives the motor
1109
to return the original table
1101
to an initial position.
With the above procedure, the film scanner reads the image information of the film
1102
fixed to the original table
1101
. The read image information can be used in an external device such as a personal computer.
However, on the optical path used when the light emitted from the lamp
1103
reaches the line sensor
1107
, the aperture unit
1108
is arranged, and the aperture of the aperture unit
1108
is adjusted to adjust an amount of light being incident on the line sensor
1107
. For this reason, the following drawbacks are generated.
Since the aperture unit
1108
for adjusting an amount of light being incident on the line sensor
1107
must be arranged, the film scanner has a complex structure. In addition, since the film scanner must comprise the control circuit for controlling the operation of the motor
1110
, the film scanner cannot be easily reduced in size.
An image signal output from the CCD includes random noise and noise generated by a variation in dark current.
FIGS. 31A and 31B
show image signal outputs from the CCD in a state wherein incident light is interrupted.
FIG. 31A
shows a dark current output from the CCD at 25° C. for an accumulation time of 10 msec, and the variation in dark current is about 4 mV.
This dark current has a value changed depending on a temperature and an accumulation time. For example,
FIG. 31B
shows an image signal output from the CCD when the temperature and the accumulation time in the state in
FIG. 31A
increase by &agr;° C. and &bgr; msec, respectively. It is understood that the level of the dark current is high as a whole.
Due to such a dark current, the ratio of an image signal and noise of an image of a high-density portion of, especially, a negative film or the like has an equal level. For this reason, when the image is displayed, stripes may be formed in a sub-scanning direction. Therefore, in the prior art, an image process such as smoothing or averaging is performed to an image signal to make the stripes inconspicuous. However, since the sharpness of the image is degraded, image quality is degraded.
As an illumination light source of the film original reading apparatus, a halogen lamp, a fluorescent lamp, an LED, and the like are used. These lamps are selectively used depending on applications. For example, a high-speed reading operation is to be performed, a halogen lamp, a fluorescent lamp, or the like is used as a brighter light source to increase illuminance on a film surface. In addition, when the apparatus is desired to be reduced in size, an LED may be used as a light source which generate a small amount of heat.
However, when a halogen lamp or a fluorescent lamp is used as a light source, the light source generate a large amount of heat. For this reason, in-focus precision is degraded by waviness generated on a film surface by the heat, or the film itself may be damaged. In order to solve this problem, the interval between the light source and the film is increased such that the film is not adversely affected by heat from the light source, or a cooling fan is arranged. As a result, the apparatus cannot be easily reduced in size. In addition, since a time from the light source is turned on to when an amount of light is stable is long, the ON state of the light source must be kept before the film image is read regardless of a reading operation.
On the other hand, when an LED is used a
Nagano Masatoshi
Onda Yoshinari
Sato Hidekage
Adams Russell
Canon Kabushiki Kaisha
Kim Peter B.
Morgan & Finnegan , LLP
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