JPH0678141A - Image reader - Google Patents

Abstract

PURPOSE:To obtain a desired picture output regardless of overflow of an image sensor. CONSTITUTION:This image reader is provided with a detecting part 110, a discriminating part 115, a selecting part 113, etc., which substitute the picture signal, which is obtained at the time when the overflow signal is in the high level, with prescribed set picture data or normal picture data adjacent to the overflow area to correct the picture signal synchronously with the overflow signal which is outputted from an image sensor 104 at the time of overflow of the image sensor.

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 having an image sensor for converting light energy into an electric signal.

The present invention also provides a copying machine, a facsimile machine,
Of course, it can be applied to an electronic camera or the like.

[0003]

2. Description of the Related Art Conventionally, an image reading apparatus using an image sensor is generally constructed as shown in FIG. An original placed on the original table glass 1 is illuminated by an illumination lamp 2 capable of controlling the light amount, and light reflected from the original is condensed by a lens 3 to form an image on an image sensor 4. An image output photoelectrically converted by the image sensor 4 is amplified to a predetermined level by an amplifier 5, and converted into a digital image signal by an A / D (analog / digital) converter 6. The shading correction unit 7 performs shading correction on the illumination lamp 2, the lens 3, and the image sensor 4 on the digital image signal. The shading-corrected image signal has the masking correction unit 8 correct the spectral characteristics of the illumination lamp 2 and the image sensor 4, the LOG (logarithm) conversion unit 9 performs LOG conversion, and transfers the image signal to a printer unit (not shown) as image data. To be done.

[0004]

However, in the conventional device as described above, the CCD is used as the image sensor.
In an image sensor using a solid-state image sensor such as a (charge coupled device), particularly a line sensor, when light having a saturation output voltage or more is incident, the light overflows and charges are applied to a portion where no light is incident. Cannot be read normally, as it will overflow. In the case of an area sensor, an overflow drain is often provided,
This prevents overflow.

That is, in the above-mentioned conventional example, the diffused light of the illumination lamp 2 is condensed, and the light amount of the illumination lamp 2 is controlled so as not to exceed the saturation voltage of the image sensor 4. Nevertheless, when a mirror or a reflector having a curvature is placed on the platen glass 1, specularly reflected light enters the image sensor 4 instead of diffused light, so that a light amount exceeding the saturation voltage of the image sensor 4 is incident. As a result, the image sensor 4 blooms. For this reason, the blooming portion became pure white and could not be accurately read.

Further, in the prior art, it was not possible to judge whether the line sensor overflowed, and it was not possible to judge whether the sensor output was normal.

In view of the above points, an object of the present invention is to provide an image reading apparatus capable of obtaining a desired image output even when the image sensor overflows.

A further object of the present invention is to provide an image reading apparatus capable of determining whether or not light that overflows the image sensor has entered, and which pixel of the image sensor has entered. Especially.

[0009]

In order to achieve the above object, a first embodiment of the present invention is directed to an image sensor that outputs an overflow detection signal in addition to an image signal, and an overflow detection signal based on the overflow detection signal. A correction means for correcting the image signal by replacing the image signal of a part with a predetermined correction signal is provided.

Further, according to the present invention, preferably, the predetermined correction signal may be image data inputted in advance from an external input means.

Further, according to the present invention, preferably, the predetermined correction signal is image data generated by primary or secondary complementation based on a value of an image signal of a portion adjacent to an overflow area. it can.

Further, according to the present invention, preferably, the image sensor can output the overflow detection signal indicating that the saturation voltage has been reached when a light amount exceeding the saturation voltage is incident.

Further, according to the present invention, preferably, the overflow detection signal may be a pulse signal which can be distinguished by a low level pulse and a high level pulse for each storage time.

In the present invention, preferably, the overflow detection signal can be output corresponding to each pixel of the photodiode of the image sensor.

Further, according to the present invention, preferably, the image sensor includes a photodiode portion, and when light having a saturation voltage or more is incident on the photodiode portion, an outflow charge to the photodiodes on both sides of the incident photodiode is discharged. It is possible to output the detection result of the detection means as the overflow detection signal.

[0016]

In the first embodiment of the present invention, the overflow signal output in addition to the image signal output from the image sensor is used to correct the image signal at the time of overflow. Also obtains the desired image.

Further, according to the second aspect of the present invention, in the image sensor, when light having a voltage equal to or higher than the saturation output voltage is incident, it is determined whether or not the light has a saturation output voltage or higher based on the quantity of the incident light. Therefore, it is possible to inform that the subsequent processing circuit has overflowed.

Furthermore, by detecting the bit that has affected the overflow, not only the bit that has overflowed due to strong light but also the part where the charge has flowed out are detected and this detection output is output from the image sensor. Thus, it is possible to inform that the subsequent processing circuit has overflowed.

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(First Embodiment) FIG. 2 shows the circuit arrangement of an image reading apparatus according to the first embodiment of the present invention. Where 101
Is a platen glass 10 on which an object to be read such as a document is placed
2 is a light source for illuminating an object to be read placed on the platen glass 102, 103 is a lens for condensing the original light, and 1
An image sensor 04 can output an image signal and an overflow signal. The image signal output from the image sensor 104 is output to the first amplifier 105, and the overflow signal output from the image sensor 104 is output to the second amplifier 105.
Input to the respective amplifiers 106 of. One amplifier 10
The output signal of No. 5 is the same as in the prior art.
7, A / D conversion is performed, and the shading correction unit 109 performs shading correction, and then the masking correction unit 111.
The masking is corrected with.

The output signal of the other amplifier 106 is converted into a digital signal by the A / D converter 108, converted by the detection unit 110 so that the overflowed portion can be determined, and transferred to the determination unit 115 as a determination signal. It Although the determination unit 115 will be described in detail later, the determination unit 115 sets a prescribed image signal at the time of overflow in the determination unit 115 from the operation unit 117 through the arithmetic control unit 116 according to an input signal from the detection unit 110. Then, the set image data is output to the selection unit 113. By switching the signal of the set image data and the read image data by the selection unit 113, the predetermined set image data is output without using the read image data only when the overflow occurs.

The delay circuit 112 is for matching the timing with the judgment unit 115, and the masking correction unit 1
11 and the selection unit 113. The output signal of the selection unit 113 is logarithmically converted by the LOG conversion unit 114 and transferred to a printer unit (not shown).

FIG. 3 shows the waveform and timing of the output signal of the circuit of FIG. The waveform in FIG. 3A is the image sensor 1
The shift pulse is 04, and the accumulation time is between the pulses. The waveform of FIG. 3B shows the image sensor 10
4 is an output image signal. The waveform in FIG. 3C is an overflow signal that is the output of the image sensor 104. This overflow signal is detected by the detection unit 110.
Thus, the multi-valued data is converted into a pulse signal having the waveform shown in FIG. The waveform in FIG. 3E is image data set in the determination unit 115 from the operation unit 117 via the calculation control unit 116, and the broken line portion represents the black level.

According to the control of the pulse signal shown in FIG. 3D, the selector 113 outputs the image data shown in FIG. 3B when the pulse signal is "L" (low level). When it is "H" (high level), the setting data is switched so as to output the setting data shown in FIG. 3E, and the corrected data having the waveform shown in FIG. 3F is obtained.

(Second Embodiment) FIGS. 4 and 5 show a second embodiment of the present invention. In this embodiment, the image data in the overflow area is interpolated using the normal output image data in the portion adjacent to the overflow area, and is output as the image data in the overflow area. Reference numeral 312 in FIG. 4 is a multi-line delay circuit that delays data of one or more lines to perform the interpolation.
Reference numeral 5 stores normal image data (for example, image data of portions indicated by A and B in FIG. 5) adjacent to the overflow area, and interpolation data D ₀ based on the following equation (1).
Is a determination unit and a memory for creating

[0026]

[Equation 1]

Here, A is the value of normal image data at point A in FIG. 5, B is the value of normal image data at point B in FIG. 5, N is the number of pixels between points A and B, and n is the correction. The number of pixels from point A to a point in the overflow area.

In this way, the determining unit 315 generates the image data (interpolation data) of the overflow portion, and the selecting unit 113 uses the interpolation data only when the overflow occurs to obtain the image data.

(Third Embodiment) In the second embodiment of the present invention described above, the interpolation of the image data at the time of overflow is the linear interpolation of the first order as shown in the above equation (1). As the third embodiment of the present invention, secondary interpolation may be performed based on all normal image data in the adjacent portion of the overflow area. It goes without saying that this makes it possible to obtain the same results as in the second embodiment.

(Fourth Embodiment) Next, the structure of the image sensor applicable to the above-described first to third embodiments of the present invention will be described.

FIGS. 6, 7, 8, 9, and 10 show a fourth embodiment of the present invention. FIG. 6 shows the array structure on the front surface of the image sensor of this embodiment, and FIG. 7 shows a potential cross section taken along the line AB of FIG. Here, 601 is a photodiode that generates an electric charge by the received light, and 602 is a CCD.
A shift gate (B) that gates the (charge coupled device) and the photodiode 601 portion, and 603 are CCDs (B) that transfer and output the photodiode signal. Further, reference numeral 604 is a shift gate (A) for transferring a charge equal to or higher than the saturated output to the CCD (A), and 605 is a CCD (A) for outputting an overflow signal.

FIG. 8 shows the timing of signals for driving the image sensor shown in FIG. At the “H (high level)” portion of the shift pulse A pulse, the photodiode 601
Shift charge from the overflow gate (A) 60
4 to the CCD (A) 605. The photodiode 601 is provided at the “H” portion of the shift gate B pulse.
Image signal of the CCD through the shift gate (B) 602
(B) Transfer to 103.

In the potential cross-sectional view of FIG. 7, the one-dot chain line of the photodiode 601 indicates the limit value of overflow, and if it exceeds this limit value, it means that overflow occurs. The broken line of the shift gate (A) 604 shows the change in the power supply of the shift gate when the pulse for the shift gate A becomes “H”. The broken line of the shift gate (B) 602 indicates that the shift gate B pulse is “H”.
Shows the change in the potential of the shift gate in the case of.
Transfer to D (B) 603.

FIG. 10 shows the output when a large amount of light exceeding the saturation voltage is applied to the shaded portion of the image sensor of FIG. As shown in FIG. 10, the overflow output from the image sensor is output only from the high-light-amount light receiving portion, and the image output is as shown in the lower waveform of FIG.

(Fifth Embodiment) FIGS. 11, 12 and 13 show a fifth embodiment of the present invention. The image sensor of this embodiment is different from the image sensor of the first embodiment shown in FIG. 6 in that the portions 604, 605 are replaced by 502, 501. Here, 502 is a gate (A) that holds the level of the overflow limit, and
Reference numeral 01 is a charge-voltage conversion unit that is a part that converts the charges overflowing from the gate (A) 502 into a voltage. Also, 5
Reference numeral 03 is a comparator that determines whether or not overflow charge has been injected into the charge-voltage converter 501.
Reference numeral 4 is a latch unit that holds the output of the comparator 503 only for 1H (1 storage time). The charge in the charge-voltage converter 501 is cleared at the “H” portion of the shift pulse A. The drive pulse is the same as in FIG. 8 of the above embodiment.

FIG. 13 shows the operation of the image sensor of FIG. Now, if a light input above saturation is applied to the image sensor of FIG. 11 for the accumulation time and the light input above saturation of the accumulation time or the part of the charge, the charge is converted via the gate (A) 502 into the charge-voltage converter 501. Flow out into the comparator 503 and the potential there rises
The threshold voltage Va is changed from “L” to “H”, and at the rising edge of the shift pulse A of the accumulation time, this value is latched by the latch unit 504 and the charge of the charge-voltage conversion unit 501 is cleared. In this way
The overflow output is obtained from the image sensor. The output of the image signal of the image sensor of this embodiment is the same as the operation of a normal CCD image sensor.

(Sixth Embodiment) FIG. 14 shows an array structure of an image sensor according to a third embodiment of the present invention. Where 8
Reference numeral 01 is a photodiode that generates electric charges by the received light, and 802 is a CCD that transfers pixels between the photodiodes 801 and overflow charges.

The light exceeding the saturation voltage is applied to the photodiode 8
When incident on the portion indicated by reference numeral 01 of No. 01, electric charges are leaked from 2 to 1 and 3 of the photodiode 801. This charge flows into CCD 802 1 and 2 and CCD 802 1
And output is obtained at 2. This results in overflow and avalanche signal outputs from this image sensor. The drive signal is the same as that obtained by removing the shift gate A from FIG.

Needless to say, in the fourth to sixth embodiments, the image sensor may be a 3-line color sensor.

[0040]

As described above, according to the present invention,
Since the overflow signal output in addition to the image signal output from the image sensor is used to correct the image signal at the time of overflow, desired image data can be obtained even at the time of overflow. effective.

Further, according to the present invention, the overflow detection unit is provided in the image sensor, and the detection result is output as an overflow signal separately from the image signal output. It is also possible to easily determine which pixel the light has entered.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration example of a conventional image reading apparatus.

FIG. 2 is a block diagram showing a circuit configuration of the image reading apparatus according to the first embodiment of the present invention.

FIG. 3 is a waveform diagram showing waveforms and timings of output signals of the circuit of FIG.

FIG. 4 is a block diagram showing a circuit configuration of an image reading apparatus according to a second embodiment of the present invention.

FIG. 5 is a plan view showing an example of the position of an overflow area in the second embodiment of the present invention.

FIG. 6 is a plan view showing an array structure of an image sensor according to a fourth embodiment of the present invention.

7 is a potential cross-sectional view showing a potential cross section along the line AB of the image sensor of FIG.

8 is a timing chart showing the timing of signals for driving the image sensor of FIG.

FIG. 9 is a schematic view schematically showing a case where a large amount of light is received on a part of the image sensor.

10 is a waveform chart showing the relationship between overflow output and image output in the state of FIG.

FIG. 11 is a plan view showing an array structure of an image sensor according to a fifth embodiment of the present invention.

12 is a potential cross-sectional view showing a potential cross section taken along line CD of the image sensor of FIG.

FIG. 13 is a timing chart showing timings and waveforms of output signals of drive signals of the image sensor of FIG.

FIG. 14 is a plan view showing an array structure of an image sensor according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference numeral 101 original platen glass 102 light source 103 lens 104 image sensor 105, 106 amplifier 107, 108 A / D converter 110 detection unit 111 masking correction unit 112 delay circuit 113 select unit 114 LOG conversion unit 115 judgment unit 116 arithmetic control unit 117 operation unit 312 Multi-line delay circuit 315 Judgment unit and memory 501 Charge-voltage conversion unit 502 Gate (A) 503 Comparator 504 Latch unit 601 Photodiode 602 Shift gate (B) 603 CCD (B) 604 Shift gate (A) 605 CCD (A) 801 Photodiode 802 CCD

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Yoshinori Ikeda Inventor Yoshinori Ikeda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yasuo Hasegawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Non Inc. (72) Inventor Katsuyoshi Maejima 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takashi Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akiko Hasegawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (7)

[Claims] 1. An image sensor that outputs an overflow detection signal in addition to the image signal, and corrects the image signal by replacing the image signal in the overflow detection portion with a predetermined correction signal based on the overflow detection signal. An image reading apparatus comprising: 2. The image reading apparatus according to claim 1, wherein the predetermined correction signal is image data input in advance from an external input means. 3. The predetermined correction signal is image data generated by primary or secondary complementation based on a value of an image signal of a portion adjacent to an overflow area. 1. The image reading device described in 1. 4. The image sensor outputs the overflow detection signal indicating that the saturation voltage has been reached when a light amount exceeding the saturation voltage is incident. The image reading device described. 5. The image reading apparatus according to claim 4, wherein the overflow detection signal is a pulse signal that can be distinguished by a low level pulse and a high level pulse for each storage time. 6. The image reading apparatus according to claim 4, wherein the overflow detection signal is output corresponding to each pixel of the photodiode of the image sensor. 7. The image sensor includes a photodiode section, and a detection unit that detects, when light having a saturation voltage or higher is incident on the photodiode section, an electric charge flowing to the photodiodes on both sides of the incident photodiode. The image reading apparatus according to claim 4, further comprising: a detection result output by the detection unit as the overflow detection signal.