JPH11308410A - Image reader and method for reading image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain reading of an image almost at the same time when a light source for original radiation is lighted by adjusting a gain of a signal processing means so that an output of the signal processing means reaches a prescribed value in response to an output of a luminous quantity monitor means. SOLUTION: A rising time of the reader extended over a long period is one of factors delaying a time to obtain a first copy from its standby state. Then a variable amplifier is controlled in terms of real time to apparently quicken the rising characteristic of a light source and to provide the quick stability as shown in figure (b), resulting in obtaining the first copy quickly. The control characteristic of the amplification factor in this case is illustrated in figure (c). That is, the circuit gain is set higher when the luminous quantity is insufficient to amplify the signal level thereby correcting the characteristic of an image reception level equally to the image processing OK level shown in figure (b). Thus, the gain of a signal processing means is adjusted till the luminous quantity of the original radiation light source is made stable after the lighting of the light source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus used in an image forming apparatus or the like, which starts an image reading operation under a predetermined light amount.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, at the time of a first copy, the start of an image forming operation has been waited for a time until the light amount of a document irradiation lamp reaches a predetermined level and stabilizes to a light amount necessary for image formation.

[0003]

As described above, it takes a long time to perform the first copy, which is one of the causes of a decrease in office efficiency.

The present invention has been made under such circumstances, and has as its object to provide an image reading apparatus and an image reading method capable of reading an image almost simultaneously with turning on a light source for illuminating a document. It is.

[0005]

According to the present invention, in order to achieve the above object, a light amount monitor is started from the start of lighting control of a light source of an image reading apparatus, and the image reading is performed in accordance with the rising characteristic of the light amount. In order to secure a predetermined image reading level, the gain is sequentially adjusted in the process of signal processing after the photoelectric conversion element to improve the apparent light amount rising time.

More specifically, the image reading apparatus is described in (1) below.
(5) and the image reading method is configured as (6) below.

(1) A document irradiating light source for irradiating a document for reading a document, photoelectric conversion means for generating an output signal corresponding to light from the document irradiated by the document irradiating light source,
Signal processing means for processing the output signal of the photoelectric conversion means, light quantity monitoring means for monitoring the light quantity of the document irradiation light source, and the light quantity from the lighting of the document irradiation light source being stable in accordance with the output of the light quantity monitoring means. An image reading apparatus comprising: a gain adjustment unit that adjusts a gain of the signal processing unit so that an output of the signal processing unit becomes a predetermined value until the output of the signal processing unit reaches a predetermined value.

(2) In the image reading device according to the above (1), the gain adjusting means is a variable amplifier.

(3) In the image reader according to the above (1), the gain adjusting means is an A / D converter.

(4) In the image reader according to (3), the reference voltage Vt of the A / D converter is used.
An image reading device that adjusts the gain by changing the op.

(5) The image reading apparatus according to (4), further comprising an automatic background cancel circuit,
An image reading apparatus using the automatic background cancel circuit for controlling the reference voltage Vtop.

(6) A document reading method in an image reading apparatus, wherein a first step of turning on a document irradiation light source for irradiating a document for reading a document, and a light amount of the document irradiation light source reaching a predetermined value A second step of judging whether or not the output of the signal processing system has reached a predetermined value when it is determined that the output has not reached the predetermined value in the second step. An image reading method, comprising:

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to examples of a copying machine.

Although the embodiment uses a reflective original, the present invention is not limited to this, and can be similarly implemented using a transparent original (also referred to as a transparent original). Further, in the embodiment, the original is scanned and read by the line sensor. However, the present invention is not limited to this, and the present invention can be similarly implemented by directly reading by the area sensor. Further, the present invention is not limited to the form of an apparatus such as a copying machine, but can be similarly implemented in the form of an image reading method.

[0015]

(Embodiment 1) FIG. 5 shows an embodiment "copier".
FIG. 2 is a cross-sectional view showing the overall configuration of the embodiment. In FIG. 1, a document feeder 101 of a reader unit 1 feeds a document (not shown) one by one in order from the last page onto a platen glass 102, and after the reading operation of the document is completed, the document on the platen glass 102. Is to be discharged. When the document is conveyed onto the platen glass 102, the lamp 103 is turned on, the movement of the scanner unit 104 is started, and the document is exposed and scanned. The light reflected from the original by the exposure scanning is guided to an image sensor (hereinafter, referred to as a CCD) 109 by mirrors 105, 106, 107 and a lens 108. Thus, the scanned image of the original is a CCD image.
Read by 109. The image data output from the CCD 109 is transferred to the printer unit 2 after a predetermined process. The laser driver 221 of the printer unit 2 drives the laser light emitting unit 201 and causes the laser light emitting unit 201 to emit laser light corresponding to the image data output from the reader unit 1. And this laser light is
The laser beam is applied to different positions on the photosensitive drum 202, and latent images corresponding to these laser beams are formed on the photosensitive drum 202. The latent image portion of the photosensitive drum 202 includes a developing device 2
03 causes the developer to adhere. Then, at a timing synchronized with the start of the laser beam irradiation, a recording sheet is fed from either the cassette 204 or the cassette 205, conveyed to the transfer section 206, and the developer adhered to the photosensitive drum 202 is removed. Transfer to recording paper. Then, the recording paper on which the developer is loaded is conveyed to the fixing unit 207 and the fixing unit 20.
By the heat and pressure at 7, the developer is fixed on the recording paper. The recording paper that has passed through the fixing unit 207 is
The sorter 220 sorts the recording paper by storing the discharged recording paper in each bin.
When double-sided printing is set, the recording sheet is conveyed to the discharge roller 208, the rotation direction of the discharge roller 208 is reversed, and the recording paper is guided to the re-feed conveyance path 210 by the flapper 209. When multiplex printing is set, the recording paper is guided to the re-feeding conveyance path 210 by the flapper 209 so that the recording paper is not conveyed to the discharge roller 208, and the recording paper guided to the re-feeding conveyance path 210 is the same as described above. Paper is fed to the transfer unit 206 at the same timing as the timing.

FIG. 1 is a block diagram showing the configuration of the reader unit 1. As shown in FIG. The image data output from the CCD 109 shown in FIG. 4 is obtained by sampling the output corresponding to the characteristics of the lamp 103 and the amount of reflected light according to the image original by the sample-and-hold unit 110, and sending it to the image processor 114 via the variable amplifier 111. Feed image formation is being performed. The image data that has passed through the image processor is sent to the printer unit (output device) 2 shown in FIG. 5, is output-controlled by an output device driver (not shown), and is output as an image output.

FIG. 2A is a diagram showing a rising characteristic of a power supply such as a fluorescent lamp. The horizontal axis indicates the time required for rising, and the vertical axis indicates the lamp light amount (light intensity). Conventionally, halogen lamps have been the mainstream in copiers, but are switching to light sources that consume less power and generate less heat. However, a discharge tube such as a fluorescent lamp tends to have a longer stabilization time of a discharge phenomenon than a halogen lamp, and thus requires a longer time until a stable light amount can be supplied. The rise time is extended from standby to 1
This is one of the factors that slows down the time required to obtain the first copy (first copy).

Therefore, in order to make the rising characteristics of the light source seem faster, to provide high-speed stability as shown in FIG.
11 real-time control is performed. The control characteristic of the amplification factor at this time is as shown in FIG. That is, when the amount of light is insufficient, the circuit gain is set high and the signal level is amplified, so that correction is performed so that the characteristics become equivalent to the image processing OK level shown in FIG.

FIG. 3 shows an operation flow at that time. When the operator presses the copy button of the operation unit (not shown) of the copying machine at 301 in the flowchart, the copying operation is started. When the light source lighting control of 302 is performed, the light source
The rising characteristic as shown in FIG. FIG.
The dotted line in (a) is the light level required for image formation,
The time required to stabilize at the dotted line level is the wait time. That is, in the state of the transition of the light amount, which is the wait time in the related art, NO is selected by the light amount determination flow of 303, and the amplification factor of 304 is calculated from the output of the light amount detecting means (not shown). The calculated amplification factor is set in the amplifier 111 by the 305. At this time, if the image forming operation has not been started, “NO” is selected in 306, and the start of image data acquisition in 307 is selected.
In conjunction with this, the document reading unit 309 starts operating. If NO is selected once in 306, the image forming operation is turned ON, so YES is selected in 306 after the second time, and the flow returns to the predetermined light amount reaching determination flow of 303. This flow is repeated until the detection signal of the light amount detection sensor is stabilized at a predetermined level for a certain period of time.

FIG. 4 shows the rising characteristics of the light source and the criteria of the flow for determining whether or not to reach a predetermined light quantity at 303. here,
T2 indicates a gain real-time adjustment range (time). Further, T1 is a time for determining the achievement of the light amount of 303. When the target light amount is reached and the level is maintained for a predetermined period of time T1, it is determined that the target light amount has been achieved. Switch to initial data. At this time, the set gain at the time of real-time gain adjustment and the gain value at the image processing OK level are almost the same level, and even if the gain is replaced with a fixed gain, the effect on the image is insignificant. When reading of the image data at 309 is started, video data read from an image reading unit 312 including a CCD, a light source, a condenser lens, a moving optical system, and the like (not shown) is taken. The read image data is subjected to image processing in the image forming unit 310, and is output as image output in 311.

As described above, by compensating the light amount rising characteristic, the wait time until the start of the image forming operation can be shortened, and the data can be taken in at almost the same timing as when the copy start button is turned on. A copying machine with reduced time can be realized.

(Embodiment 2) This embodiment is an example in which the reference voltage of the A / D converter is controlled in real time as means for apparently increasing the rising characteristics of the light source. FIG. 7 shows the control state of the reference voltage at this time. In the A / D converter, V
If there are top and Vbottom, the input signal level of the A / D converter is the same, and the state is smaller than Vtop, the lower Vtop indicates an operation in which the apparent signal amplification factor increases. FIG. 7 shows the control state of this Vtop. FIG. 8 shows an example of UP of the amplification factor by controlling the reference voltage. It is assumed that V1> V2 and the input signal is smaller than V2. But,
In a state where the input signal exceeds V1, the peak level of the output signal does not change since the reference range is exceeded, and only the section of FF (H) fluctuates. If the input signal is smaller than V1 and larger than V2, the reference voltage Vtop is controlled from V1 to V2 in a process of controlling the reference voltage Vtop, although there is an amplifying action. All become FF (H). As described above, if the input signal exceeds the level of Vtop, it is impossible to perform the original correction of the light amount adjustment.

Therefore, the Vtop is adjusted in real time by using a technique for canceling the background, which is conventionally performed in the case of reading a document in a flowing manner. Hereinafter, a method using an automatic background cancel circuit will be described.
FIG. 6 is a schematic diagram of the automatic background cancel circuit. C from the light from the light source 601 via the lens 602
Original reflected light is collected on the CD 603. The CCD output signal sampled by the sample hold unit 604 is multiplied by a predetermined gain by a variable amplifier 605, and then output as video data by an A / D converter 606.
At the same time, the A / D input signal is also branched to the comparator 607, which compares the A / D input signal with a target value (not shown). If the target value is equal to or greater than the target value, the charging circuit 610 Is selected, the capacitor 612 is charged with the reference potential via the resistor, and when the potential of the capacitor 612 is selected by the selector 608, the voltage of the A / D converter 606 is
The top increases. That is, an operation is performed in which the amplification factor of the circuit system is reduced. On the other hand, when the voltage is lower than the target value, the discharge circuit 61
1 is selected, the capacitor 612 is discharged through the resistor, and the potential drops. In the discharging state, when the capacitor 612 is selected by the selector 608, the reference voltage Vtop of the A / D converter 606 decreases, and the A / D
The output value of the converter 606 is controlled so as to approach the target value of the comparator 607. At this time, the operation of increasing the amplification factor of the circuit system is performed. An original width signal is input at the gate 609. If the signal of the entire CCD reading area is used for control when the background of the original is skipped, the signal of the area exceeding the width of the actual original is used. This is because there is a problem that data is handled and control is not correctly fed back. However, in the present embodiment, the purpose is to realize the rapid rise characteristics of the light source, and it is desirable to fully input all line data as a control signal. Therefore,
In the control when the light source rises, the document width signal is fixed at “H”. A resistance voltage divider 613 sets a limiter for the reference voltage of the circuit. Reference numeral 614 denotes a potential forcible extraction circuit for returning a reference potential different for each document to the default when the automatic background cancel function is used. Finally, when Vtop (fixed) of the selector 608 is selected, the selector 608 is switched when the light source is stabilized at the target light amount during a normal image forming operation.

With such a configuration, the wait time until the image forming operation is started can be reduced, the data can be taken in at substantially the same time as the start of the copy start button, and the first copy time can be reduced. Machine can be realized.

As described above, also in the present embodiment, a light quantity rising characteristic can be compensated, a wait time until image forming operation is started can be shortened, and a copier in which a first copy time is shortened can be realized.

[0026]

As described above, according to the present invention,
The problem of the stabilization time of the light source, which is one of the factors that delays the start of reading at the start of image reading, can be apparently improved, and the image reading operation can be started almost simultaneously with the lighting of the light source.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a reader unit.

FIG. 2 is an operation explanatory diagram

FIG. 3 is a flowchart illustrating the operation of the first embodiment;

FIG. 4 is a diagram showing the operation of the first embodiment.

FIG. 5 is a cross-sectional view illustrating the entire configuration of the first embodiment.

FIG. 6 is a diagram illustrating a configuration of a main part according to a second embodiment.

FIG. 7 is a diagram showing a change in reference voltage Vtop;

FIG. 8 is an explanatory diagram of gain adjustment using a reference voltage.

[Explanation of symbols]

 103 lamp 109 CCD 111 variable amplifier 114 image processor

Claims (6)

[Claims] An original irradiating light source for irradiating an original for reading an original, a photoelectric conversion unit for generating an output signal corresponding to light from the original irradiated by the original irradiating light source, and an output of the photoelectric conversion unit Signal processing means for processing a signal, light quantity monitoring means for monitoring the light quantity of the document irradiation light source,
Gain adjustment for adjusting the gain of the signal processing means in accordance with the output of the light quantity monitoring means so that the output of the signal processing means becomes a predetermined value from the time when the document irradiation light source is turned on until the light quantity is stabilized. And an image reading device. 2. An image reading apparatus according to claim 1, wherein said gain adjusting means is a variable amplifier. 3. The image reading apparatus according to claim 1, wherein said gain adjusting means is an A / D converter. 4. The image reading device according to claim 3, wherein a reference voltage Vtop of said A / D converter is set.
An image reading apparatus, wherein the gain is adjusted by changing the value of the image. 5. The image reading apparatus according to claim 4, further comprising an automatic background cancel circuit, wherein the automatic background cancel circuit is used for controlling the reference voltage Vtop. 6. A document reading method in an image reading apparatus, comprising: a first step of turning on a document irradiation light source for irradiating a document for reading a document; and a light amount of the document irradiation light source reaching a predetermined value. A second step of determining whether or not the output of the signal processing system has reached a predetermined value when it is determined that the output of the signal processing system has not reached the predetermined value in the second step. And an image reading method.