JP3779631B2 - Image reading device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus that reads a color original by alternately turning on light sources of a plurality of colors at a predetermined lighting duty ratio.
[0002]
[Prior art]
In image reading devices such as color facsimile machines, color image scanners, color copiers and their multifunction devices, red, green, and blue light sources are used as color light sources, and the light reflected from the original is photoelectrically converted by a light receiving element. Image data.
[0003]
At this time, the original is read in accordance with the line-sequential reading method by color-separating and reading the color original by alternately lighting three light sources of red (Red), green (Green), and blue (Blue) at intervals of one accumulation time. Has been done. Hereinafter, the three light sources of red, green, and blue are referred to as an R light source, a G light source, and a B light source.
[0004]
Thus, when performing color reading by the line-sequential reading method, the lighting duty ratio of each light source is 33% or less at the maximum, but when performing monochrome reading, only the G light source is turned on line by line. The lighting duty ratio of the light source may be up to 100%.
[0005]
Generally, as such a light source, a light emitting diode (LED) is used, and unless the drive current is used below the maximum forward current rating, life deterioration or damage occurs.
[0006]
[Problems to be solved by the invention]
However, since control of the drive current to such a light source is performed by software control, if a thermal runaway occurs and normal control cannot be performed, a drive current exceeding the maximum forward current rating is supplied to the light source. As a result, there has been a problem that the above-mentioned deterioration of life or breakage occurs.
[0007]
Therefore, an object of the present invention is to provide an image reading apparatus with improved reliability by preventing a drive current exceeding the maximum forward current rating from being supplied to a light source even if thermal runaway or the like occurs.
[0008]
[Means for Solving the Problems]
The invention according to claim 1 includes a light source including light emitting diodes of a plurality of colors, turns on the light source to irradiate the original, receives the reflected light, and outputs a video signal to read a color original. In the image reading apparatus, a light source test lighting unit is provided for causing the light source to be test-lit and determining the light source lighting control and the state of the light source based on the video signal at that time, and the lighting duty ratio of the light source is set by the test lighting. One of the test items is whether or not the video signal changes according to the change.
[0009]
The invention according to claim 2 includes a light source composed of light emitting diodes of a plurality of colors, turns on the light source to irradiate the original, receives the reflected light, and outputs a video signal to read a color original. In the image reading apparatus, a light source test lighting unit is provided for causing the light source to be test-lit and determining a light source lighting control and a light source state based on the video signal at that time. If an abnormality is detected in this state, the power supply to the light source is immediately stopped, while the lighting duty ratio of the light source is changed by the test lighting, and whether or not the video signal changes accordingly. Is one of the test items.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a color facsimile apparatus as an example of an image reading apparatus according to the present invention. FIG. 2 is a diagram showing a reading mechanism of the reading unit, and FIG. 3 is a diagram showing a reading circuit configuration.
[0012]
Such a color facsimile apparatus includes a system control unit 1 that controls the entire apparatus, a ROM that stores a control program for the system control unit 1 and a memory unit 2 that includes a RAM that stores various data relating to the operation of the apparatus. An operation display unit 3 for displaying information such as an operation state and various input operations by an operator, a reading unit 4 for optically reading a document, a recording unit 5 for forming an image on a recording paper, and a communication partner. A communication control unit 6 that exchanges facsimile control signals with a facsimile machine and executes communication, a compression / decompression unit 7 that encodes and decodes image data, and the like are connected via a bus. Yes.
[0013]
As shown in FIG. 2, the reading unit 4 sandwiches the documents set on the sheet feeding tray 11 one by one and conveys them to the document table 14, and the document conveyed by the sheet feeding roller 12. Document front / rear end detection sensor 13 for detecting the front end and the rear end and confirming the position of the document, the document placed on the document table 14 and pressing the document conveyed to the document table 14 and performing shading correction and the like. The main components are a white white pressure plate 15 used as a white reference plate when performing the operation, a paper discharge roller 16 that sandwiches and discharges a document that has been read from the document table 14 after image reading.
[0014]
A light source 20 and an image sensor 21 such as a contact image sensor are provided below the document table 14 so as to read the conveyed document.
[0015]
As shown in FIG. 3, the reading unit 4 outputs the light source 20 of the R light source 20a, the G light source 20b, and the B light source 20c, and the light source drive control signal, and also outputs a video signal from the image sensor 21 described later. A light source control circuit 23 to be captured, a light source drive circuit 24 that drives each light source 20 by supplying power based on the light source drive control signal, a power source 25 that supplies power to the light source, and a reflection from a document illuminated by the light of the light source 20 An image sensor 21 that receives light and converts it into an electrical signal, an optical unit 26 that condenses the reflected light from the original on the light receiving unit of the image sensor 21, and the like.
[0016]
With such a configuration, when reading a color original, as shown in FIG. 5, the three light sources 20 of the R light source 20a, the G light source 20b, and the B light source 20c are sequentially switched and turned on at intervals of one line. Therefore, even when all the light sources are turned on in one accumulation time, the lighting duty ratio of each light source 20 is a maximum of 33% or less.
[0017]
Thus, the video signal from the image sensor 21 is input to the light source control circuit 23 in the order of the R light source 20a, the G light source 20b, and the B light source 20c, and color image processing is performed based on the video signal to obtain a color image. It is done.
[0018]
However, as shown in FIG. 5, if the lighting duty ratio of each light source 20 is within 33% at the maximum, the light source control circuit 23 operates abnormally. If a light source 20 having a lighting duty ratio exceeding 33% is generated as shown in FIG. 6, a drive current exceeding the maximum forward current rating of the light source 20 flows as shown in FIG. In the worst case, it is damaged and cannot be read.
[0019]
Further, the abnormal operation of the light source control circuit 23 may cause two or more light sources 20 to be turned on at the same time, and color abnormality may occur in the read color image.
[0020]
FIG. 6 illustrates the case where the lighting duty ratio of the R light source 20a is 100% (always on).
[0021]
FIG. 4 is a diagram showing the maximum forward current ratings in the R light source 20a, the G light source 20b, and the B light source 20c in terms of the lighting duty ratio. In this case, the forward current maximum ratings are not always the same due to the difference in the characteristics of the light sources 20, and FIG. 4 illustrates the case where the R light source 20a has a smaller forward current maximum rating than the other G light sources 20b and B light sources 20c. Yes.
[0022]
Therefore, in the present invention, each light source 20 is turned on one by one by the light source test lighting shown in FIG. 9 to test the light source lighting control and the state of the light source 20 itself (whether it is damaged or the like). Such light source test lighting is preferably performed before reading a document.
[0023]
First, the light source control circuit 23 sets the lighting duty ratio of the test light source (step S1), and outputs a light source drive control signal to the light source drive circuit 24.
[0024]
The light source drive circuit 24 drives the test light source based on the light source drive control signal. In this case, the lighting duty ratio is set within a maximum of 33%.
[0025]
Next, lighting control of the test light source is started (step S2), and the video signal is monitored (step S3).
[0026]
FIG. 7 is a diagram showing a lighting state of each light source 20 and a video signal capturing state with respect to the test light source.
[0027]
The light source control circuit 23 can exemplify a method of monitoring the peak value of the video signal, for example, when monitoring the video signal.
[0028]
As described above, in the method of monitoring the peak value of the video signal, a value when the test light source is turned on as shown in FIG. 8A (hereinafter referred to as a bright output value) and a state shown in FIG. 8B. A value when the test light source is turned off (hereinafter referred to as a dark output value) is obtained.
[0029]
Therefore, it is determined whether or not the bright output value is larger than the dark output value (step S4). In this way, if the test light source performing lighting control fails and is not lit, the bright output value and the dark output value are the same level, so the test light source fails. Can be judged.
[0030]
If it is determined that the bright output value is larger than the dark output value (bright output value> dark output value), whether or not the dark output value is the same as the preset dark output reference value is determined. Judgment is made (step S5).
[0031]
If it is determined in step S5 that the dark output value and the dark output reference value are the same value (dark output value = dark output reference value), the test light source is normally turned off.
[0032]
However, if the dark output value and the dark output reference value are not the same value (dark output value ≠ dark output reference value), it is an abnormal state in which the test light source is not turned off even though the turn-off control is performed. .
[0033]
As such a state, for example, although the lighting duty ratio is set to 33% or less as control, the actual lighting duty ratio is over 33% or the lighting is always on. A case can be illustrated.
[0034]
Such a determination is made, and when the light output value> the dark output value and the dark output value = the dark output reference value, it can be determined that the test light source is operating normally (step S6).
[0035]
On the other hand, if the light output value is not greater than the dark output value or the dark output value is not equal to the dark output reference value, it is determined that some abnormality exists in the test light source or an abnormality exists in the control ( Step S7).
[0036]
When such an abnormality is detected, the reading process is not executed, and a message to that effect is displayed on the display unit or the like in the operation unit and a user response is awaited.
[0037]
In the case where the test light source is lit with a lighting duty ratio exceeding 33% due to a control abnormality, it is determined that (dark output value ≠ dark output reference value). If the operation is continued, a drive current exceeding the maximum forward current rating is supplied to the test light source for a long time, and the test light source may be damaged.
[0038]
Therefore, when such an abnormality is detected, the power supply 25 is forcibly turned off or the lighting control of each light source 20 is stopped so that physical damage to each light source 20 is minimized. It is preferable to do.
[0039]
The above processing is sequentially performed for each light source 20, and reading of image information is started when lighting monitoring is normally completed for all the light sources 20 (step S8).
[0040]
Since the state of the light source 20 and its control state can be confirmed in this way, even when a drive current exceeding the maximum forward current rating is supplied to the light source 20 due to a control abnormality or the like, this can be detected in advance. This makes it possible to prevent the occurrence of a serious situation such as breakage and improve the reliability.
[0041]
Next, a second embodiment of the present invention will be described with reference to the drawings. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate.
[0042]
The previous embodiment has been described on the assumption that the lighting duty ratio of each light source 20 within one accumulation time is constant.
[0043]
On the other hand, in the present embodiment, the light source test lighting can be performed even when the lighting duty ratio is changed.
[0044]
In such a case, the lighting duty ratio of each light source 20 is sequentially switched as shown in FIG.
[0045]
FIG. 13 is a flowchart showing the procedure of the light source test lighting. First, the light source control circuit sets the lighting duty ratio of the test light source (step S11), and outputs the control signal to the light source driving circuit 24. The lighting duty ratio to be set at this time is 30, 40, 50%, etc. Predetermined and set to one of them.
[0046]
Thereby, the light source drive circuit 24 drives the test light source based on the control signal.
[0047]
Next, the lighting monitoring control of the test light source is started (step S12), and the peak value monitoring of the video signal is performed (step S13).
[0048]
Then, the video signal is monitored by the light source control circuit 23, and it is determined whether or not the bright output value is larger than the dark output value (step S14).
[0049]
As a result, if the test light source that performs lighting monitoring control fails and does not light, the bright output value and dark output value will be the same level, so the test light source will fail. Can be judged.
[0050]
If it is determined that the bright output value is larger than the dark output value (bright output value> dark output value), whether or not the dark output value is the same as the preset dark output reference value is determined. Judgment is made (step S15).
[0051]
If it is determined in step S15 that the dark output value and the dark output reference value are the same value (dark output value = dark output reference value), the test light source is normally turned off.
[0052]
However, when the dark output value and the dark output reference value are not the same value (dark output value ≠ dark output reference value), the light source is turned off as a control, but the test light source is not turned off normally. is there.
[0053]
Such a determination is made for all the lighting duties (step S16), and when all the lighting duties are bright output value> dark output value and dark output value = dark output reference value, the lighting duty is set. It is determined whether a bright output proportional to the ratio has been detected (step S17).
[0054]
FIG. 11 shows the video signal waveform when the lighting duty ratio is changed, and FIG. 12 is a diagram showing the relationship between the lighting duty ratio and the bright output value when the test light source is normal.
[0055]
Thus, as shown in FIG. 12, when a proportional relationship is recognized between the lighting duty ratio and the bright output value, it can be determined that the test light source is operating normally (step S18).
[0056]
On the other hand, if the light output value> the dark output value, the dark output value = the dark output reference value, or if there is no proportional relationship between the lighting duty ratio and the bright output value, the test light source It is determined that an abnormality exists or an abnormality exists in the control (step S19).
[0057]
When such an abnormality is detected, the reading process is not executed, and a message to that effect is displayed on the display unit or the like in the operation unit and a user response is awaited.
[0058]
The above test is sequentially performed on each light source 20, and when lighting monitoring is normally completed for all the light sources 20, reading of image information is started (step S20).
[0059]
Since the state of the light source 20 and its control state can be confirmed in this way, even when a drive current exceeding the maximum forward current rating is supplied to the light source 20 due to a control abnormality or the like, this can be detected in advance. This makes it possible to prevent the occurrence of a serious situation such as breakage and improve the reliability.
[0060]
【The invention's effect】
As described above, according to the present invention, the lighting duty ratio of the light source is changed by the test lighting, and whether or not the video signal changes according to this is set as one of the test items. Therefore, it is possible to determine the light source lighting control and the light source state in all lighting states, thereby improving the reliability.
[Brief description of the drawings]
FIG. 1 is a block diagram of a facsimile apparatus applied to the description of an embodiment of the present invention.
FIG. 2 is a diagram illustrating a reading mechanism of a reading unit.
FIG. 3 is a diagram illustrating a reading circuit configuration.
FIG. 4 is a diagram showing a forward current maximum rating with respect to a lighting duty ratio of a light source.
FIG. 5 is a diagram when a light source drive control signal is normally output.
FIG. 6 is a diagram when an abnormality occurs in a light source drive control signal.
FIG. 7 is a diagram showing a light source drive control signal at the time of test lighting.
8A and 8B are diagrams showing the waveform of a video signal, where FIG. 8A shows a waveform during bright output, and FIG. 8B shows a waveform during dark output.
FIG. 9 is a flowchart showing a test lighting procedure;
FIG. 10 is a diagram showing a light source drive control signal at the time of test lighting applied to the description of the second embodiment.
FIG. 11 is a diagram illustrating a waveform of a video signal.
FIG. 12 is a diagram illustrating a relationship between a bright output value and a lighting duty person.
FIG. 13 is a flowchart showing a test lighting procedure;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 System control part 4 Reading part 20 Light source 20a R light source 20b G light source 20c B light source 21 Image sensor 23 Light source control circuit 24 Light source drive circuit 25 Power supply

Claims (2)

In an image reading apparatus comprising a light source composed of light emitting diodes of a plurality of colors, turning on the light source to irradiate the original, receiving the reflected light and outputting a video signal, the image reading apparatus reads the color original. Provided with a light source test lighting means for performing test lighting and determining the light source lighting control and the state of the light source based on the video signal at that time,
An image reading apparatus characterized in that the lighting duty ratio of the light source is changed by the test lighting, and whether or not the video signal changes according to the duty ratio is one of the test items. In an image reading apparatus comprising a light source composed of light emitting diodes of a plurality of colors, turning on the light source to irradiate the original, receiving the reflected light and outputting a video signal, the image reading apparatus reads the color original. Provided with a light source test lighting means for performing test lighting and determining the light source lighting control and the state of the light source based on the video signal at that time,
When an abnormality is detected in the light source lighting control or the state of the light source by the light source test lighting, the power supply to the light source is immediately stopped,
An image reading apparatus characterized in that the lighting duty ratio of the light source is changed by the test lighting, and whether or not the video signal changes according to the duty ratio is one of the test items.

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