Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2001-08-27
2003-11-18
Le, Thien M. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462250
Reexamination Certificate
active
06648226
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image reading apparatus for reading a document image, a method of controlling the same, and a control program.
2. Description of the Related Art
FIG. 1
is a schematic block diagram of the configuration of an image reading apparatus
200
.
In
FIG. 1
, the image reading apparatus
200
is connected to a host computer
100
, and is controlled by the host computer
100
. Images from the image reading apparatus
200
are displayed by the host computer
100
, and are saved therein.
The host computer
100
includes a CPU (central processing unit)
101
for performing various operations, a RAM (random access memory)
102
which is used as a work area by an operating system or programs, a hard disk
103
for storing the operating system and the programs, a monitor
104
, an input device
105
including a mouse and a keyboard, and an interface unit
106
for connecting the host computer
100
to an external device of the image reading apparatus
200
.
The interface unit
106
comprises a serial interface, a parallel interface, a SCSI (small computer serial interface), a USB (universal serial bus) interface, and an IEEE 1394 interface.
The image reading apparatus
200
includes a contact image sensor (hereinafter referred to as “CIS”)
201
, LEDs (light emitting diodes)
202
used as light sources, an LED control circuit
203
, an amplifier
204
, an analog-to-digital (A/D) converter circuit
205
, a shading RAM
206
, a shading correction circuit
207
, a peak detecting circuit
208
, a gamma conversion circuit
209
, a buffer RAM
210
, a packing/buffer RAM control circuit
211
, an interface circuit
212
, a motor drive circuit
213
, and a motor
214
.
FIG. 2
illustrates the configuration of a program stored in the host computer
100
for controlling the image reading apparatus
200
. The program includes a TWAIN (Technology Without Any Interested Name) compatible application
301
, a TWAIN driver
302
, a device driver
303
, a port driver
304
, and an operating system (OS)
305
.
The packing/buffer RAM control circuit
211
controls the motor
214
and the buffer RAM
210
in the following way:
Image data output from the packing/buffer RAM control circuit
211
is written to the buffer RAM
210
, and the image data written is read from buffer RAM
210
to the host computer
100
via the interface circuit
212
. If a speed at which data is written from the packing/buffer RAM control circuit
211
to the buffer RAM
210
is higher than a speed at which the data is read by the host computer
100
from the RAM
210
, the buffer RAM
210
encounters an overflow. The packing/buffer RAM control circuit
211
checks an available space of the buffer RAM
210
, and instructs the motor drive circuit
213
to stop reading the image data when the available space equals the amount of one line of the image data. When the buffer RAM
210
becomes empty again, the packing/buffer RAM control circuit
211
instructs the motor drive circuit
213
to resume reading.
Such an operation to avoid an overflow of the buffer RAM
210
is called a start/stop operation (hereinafter referred to as “SS”). When SS is effected, the reading may be resumed either at the stop position of the CIS
210
or at a position back from the stop position. If the reading is resumed at the stop position, the image may discontinue at the stop position, thereby causing degradation of image quality. If the reading is resumed at a position back from the stop position, an extra time is required before the reading can be resumed, thereby making the overall scan time slower. Such inconveniences are inevitable if SS is caused, and it is therefore necessary to minimize SS as much as possible.
Since the driving speed of the motor
214
is proportional to a speed at which the data is written to the buffer RAM
210
, the device driver
303
conventionally controls the speed of the motor
214
so that a speed at which the data is written to the buffer RAM
210
from the packing/buffer RAM control circuit
211
is lower than a speed at which the data is read from the buffer RAM
210
by the host computer
100
, and so that the data is written to the buffer RAM
210
at the highest speed in the above condition.
The speed of the motor
214
is controlled, assuming that the host computer
100
reads image data from the buffer RAM
210
at a constant rate. If the reading of data by the host computer
100
is interrupted, the buffer RAM
210
becomes full, thereby causing SS.
One possible reason why the reading of data by the host computer
100
is interrupted is swapping of memories. When an image is being read, the TWAIN driver
302
reserves a work area having the same size as the size of the image. If an available space of the RAM
102
is greater than the image size, the RAM
102
is used for the work area. If an available space of the RAM
102
is smaller than the image size, the work area that cannot be stored in the available space of the RAM
102
becomes a virtual memory for which the memory of the hard disk
103
is used. If the work area allocated to the hard disk
103
is accessed, swapping of memories occurs. The swapping might cause data which is being read by the host computer
100
to be interrupted depending upon the performance of the hard disk
103
.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an image reading apparatus which prevents degradation of image quality and a delay in the image reading time which are caused by interruption of reading of image data, and to provide a method of controlling the image reading apparatus.
To achieve the above object, the method of and the apparatus for reading images according to the present invention is constituted as follows.
An image reading apparatus includes: an image reading unit having a photoelectric conversion component for reading light from an image and converting the read image to an image signal; a driving motor for moving the image reading unit and the image relative to each other; a motor control unit for controlling the driving motor; an interface connecting to an external information processing device; a conversion circuit for performing analog-to-digital conversion on the image signal into image data; a memory connected to the interface for storing the image data; and a control signal receiving unit for receiving a motor control signal via the interface. The control signal receiving unit receives the motor control signal which controls the driving motor so as to satisfy the relationship V1≦V2, where V1 represents a data speed at which the image is read to generate the image data, and V2 represents a data speed at which the image signal read out via the interface is stored in the information processing device as one piece of image data. The motor control unit controls the driving motor according to the received motor control signal.
An image reading system includes an image reading apparatus, and an information processing apparatus. The image reading apparatus includes: an image reading unit having an photoelectric conversion component for reading light from an image and converting the read image to an image signal; a driving motor for moving the image reading unit and the image relative to each other; a motor control unit for controlling the driving motor; a conversion circuit for performing analog-to-digital conversion on the image signal into image data; and an image memory for storing the image data. The information processing apparatus includes: a temporary storage memory for reading and temporarily storing the image data stored in the image memory; a first timer for measuring the speed of the data stored in the temporary storage memory; and a control signal generating unit for outputting a motor control signal to the motor control unit based on the measurement of the first timer. The motor control unit controls the driving motor according to the motor control signal output by the control signal generating unit.
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