JP3207544B2 - Image reading device - Google Patents

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.

Further, the present invention relates to a copying machine, a facsimile machine,
Of course, the present invention can be applied to an electronic camera and the like.

[0003]

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

[0004]

However, in the above-described conventional apparatus, a CCD is used as an image sensor.
In an image sensor using a solid-state imaging device 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 also applied to a portion where light is not incident. Overflows, so that normal reading cannot be performed. In the case of an area sensor, an overflow drain is often provided,
This prevents overflow.

That is, in the above-described conventional example, the configuration is such that the diffused light of the illumination lamp 2 is condensed, and the light quantity of the illumination lamp 2 is controlled so as not to exceed the saturation voltage of the image sensor 4. Nevertheless, if a mirror or a reflective object having a curvature is placed on the platen glass 1, specular reflection light enters the image sensor 4 instead of diffused light, so that an amount of light exceeding the saturation voltage of the image sensor 4 is incident. As a result, the image sensor 4 blooms. For this reason, the portion where blooming occurred became pure white, and accurate reading could not be performed.

In the prior art, it was not possible to determine whether or not the line sensor overflowed, and it was not possible to determine whether or not the output was normal.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide an image reading apparatus capable of obtaining a desired image output even when an image sensor overflows.

It is a further object of the present invention to provide an image reading apparatus capable of determining whether or not the image sensor has overflowed light and which pixel of the image sensor has been incident. It is in.

[0009]

According to a first aspect of the present invention, there is provided an image sensor for outputting an overflow detection signal in addition to an image signal, and an overflow sensor for detecting an overflow based on the overflow detection signal. Correction means for correcting the image signal by replacing a part of the image signal with a predetermined correction signal.

In the present invention, preferably, the predetermined correction signal may be image data previously input from external input means.

In the present invention, it is preferable that the predetermined correction signal is image data generated by primary or secondary complement based on a value of an image signal in a portion adjacent to an overflow area. it can.

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

In the present invention, it is preferable that the overflow detection signal is a pulse signal that can be distinguished by a low-level pulse and a high-level pulse for each accumulation time.

Preferably, in the present invention, the overflow detection signal is output corresponding to each pixel of the photodiode of the image sensor.

Preferably, in the image sensor according to the present invention, when the light having a voltage equal to or higher than the saturation voltage is incident on the photodiode, the image sensor detects the charge discharged to the photodiode on both sides of the incident photodiode. And a detection unit for detecting, and a detection result of the detection unit can be output as the overflow detection signal.

[0016]

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

According to the second embodiment of the present invention, when light having a voltage higher than the saturation output voltage is incident on the image sensor, whether or not the light has a voltage higher than the saturation output voltage is determined based on the amount of the incident light. Is determined, whereby it can be notified that an overflow has occurred in the subsequent processing circuit.

Further, by detecting the bit affected by the overflow, not only the bit in which the overflow has occurred due to the strong light, but also the portion from which the electric charge has flowed out, and this detection output is output from the image sensor. Thus, it is possible to inform the subsequent processing circuit that an overflow has occurred.

[0019]

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

FIG. 2 shows a circuit configuration of an image reading apparatus according to a first embodiment of the present invention. Here, 101
A platen glass on which an object to be read such as a manuscript is placed;
Reference numeral 2 denotes a light source for illuminating an object to be read placed on the platen glass 102; 103, a lens for condensing the original light;
An image sensor 04 can output an image signal and an overflow signal. The image signal output from the image sensor 104 is supplied to the first amplifier 105, and the overflow signal output from the image sensor 104 is supplied to the second amplifier 105.
, Respectively. One amplifier 10
The output signal of the A / D converter 10 is the same as that of the prior art.
7, the A / D conversion is performed, the shading correction is performed by the shading correction unit 109, and the masking correction unit 111
Is masked.

The output signal of the other amplifier 106 is converted to a digital signal by an A / D converter 108, converted so that an overflow portion can be determined by a detection unit 110, and transferred to a determination unit 115 as a determination signal. You. The determination unit 115 will be described later in detail, but 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 in accordance with an input signal from the detection unit 110. Then, the setting image data is output to the selection unit 113. By switching the signal of the setting image data and the read image data by the selection unit 113, predetermined setting image data is output without using the read image data only at the time of overflow.

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

FIG. 3 shows the waveform and timing of the output signal of the circuit of FIG. The waveform of FIG.
The shift pulse No. 04 is an accumulation time between pulses. The waveform shown in FIG.
4 is an image signal which is an output of the image forming apparatus. The waveform in FIG. 3C is an overflow signal that is an output of the image sensor 104. This overflow signal is sent to the detection unit 110
Thus, the multi-level data is converted into a pulse signal having the waveform shown in FIG. The waveform shown in FIG. 3E is image data set in the determination unit 115 from the operation unit 117 via the arithmetic control unit 116, and the broken line indicates the black level.

In accordance with the control of the pulse signal shown in FIG. 3D, the select section 113 outputs the image data shown in FIG. 3B when this pulse signal is at "L" (low level). At the time of “H” (high level), the setting data of FIG. 3E is switched to be output, thereby obtaining corrected data of the waveform shown in FIG. 3F.

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

[0026]

(Equation 1)

Here, A is the value of the normal image data at point A in FIG. 5, B is the value of the 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 value. This is the number of pixels from point A to a point in the overflow area.

As described above, the image data (interpolated data) of the overflow portion is generated by the judging section 315, and the image data is obtained by the selecting section 113 using the interpolated data only at the time of overflow.

(Third Embodiment) In the above-described second embodiment of the present invention, the interpolation of the image data at the time of overflow is a linear interpolation of the first order as shown in the above equation (1). As a third embodiment of the present invention, secondary interpolation may be performed based on all the normal image data in the adjacent portion of the overflow area. As a result, it is needless to say that the same result as in the second embodiment can be obtained.

(Fourth Embodiment) Next, the configuration of an 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 a front array structure of the image sensor of this embodiment, and FIG. 7 shows a potential cross section along the line AB in FIG. Here, reference numeral 601 denotes a photodiode that generates electric charges by the received light, and 602 denotes a CCD.
A shift gate (B) that gates the (charge-coupled device) and the photodiode 601 portion, and a CCD (B) 603 that transfers and outputs a photodiode signal. Reference numeral 604 denotes a shift gate (A) for transferring a charge higher than the saturation output to the CCD (A), and 605 denotes a CCD (A) for outputting an overflow signal.

FIG. 8 shows the timing of signals for driving the image sensor shown in FIG. In the "H (high level)" portion of the shift pulse A pulse, the photodiode 601
From the shift gate (A) 60
4 to the CCD (A) 605. In the "H" portion of the shift gate B pulse, the photodiode 601
Image signal through the shift gate (B) 602
(B) Transfer to 103.

In the electric potential cross-sectional view of FIG. 7, the one-dot chain line of the photodiode 601 indicates a limit value of overflow, and if it exceeds the limit value, it means that overflow occurs. A broken line of the shift gate (A) 604 indicates a 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 pulse for the shift gate B is “H”.
Shows the change in the potential of the shift gate in the case where the charge of the photodiode 601 is changed to CC.
D (B) 603.

FIG. 10 shows the output of the image sensor shown in FIG. 9 when a large amount of light exceeding the saturation voltage is applied to the hatched portion. As shown in FIG. 10, the overflow output from the image sensor is output only from the high-light-quantity 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 portions 604 and 605 are replaced with 502 and 501. Here, reference numeral 502 denotes a gate (A) holding the level of the overflow limit, and 5
Reference numeral 01 denotes a charge-to-voltage converter that converts charges overflowing from the gate (A) 502 into a voltage. Also, 5
Reference numeral 03 denotes a comparator which determines whether or not overflow charge has been injected into the charge-voltage converter 501;
Reference numeral 4 denotes a latch unit that holds the output of the comparator 503 only for 1H (one accumulation time). Note that the charge of the charge-voltage converter 501 is cleared at the “H” portion of the shift pulse A. The driving pulses are the same as those in the embodiment shown in FIG.

FIG. 13 shows the operation of the image sensor of FIG. Now, assuming that the light input that is longer than the saturation is given to the image sensor of FIG. 11 for the accumulation time, the charge is converted to the charge-voltage converter 501 via the gate (A) 502 by the light input that is longer than the saturation of the accumulation time or the portion. And the potential of the comparator 503 rises.
The threshold voltage Va exceeds the threshold voltage Va and changes from “L” to “H”. At the rise of the storage time shift pulse A, this value is latched by the latch unit 504 and the charge of the charge-voltage conversion unit 501 is cleared. In this way,
An overflow output is obtained from the image sensor. The output of the image signal of the image sensor of the present embodiment is the same as the operation of a normal CCD imager.

(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 denotes a photodiode that generates electric charges based on the received light, and reference numeral 802 denotes a CCD that transfers charges between pixels of the photodiode 801 and overflow.

Light exceeding the saturation voltage is applied to the photodiode 8
When the light is incident on the portion indicated by No. 2 of 01, electric charges leak from the photodiode 801 in the directions of 1 and 3. This charge flows into 1 and 2 of the CCD 802, and
And 2 provide the output. Thereby, overflow and avalanche signal outputs are obtained from this image sensor. The drive signal is the same as that in FIG.

In the fourth to sixth embodiments, it goes without saying that the image sensor may be a three-line color sensor.

[0040]

As described above, according to the present invention,
Since an overflow image signal output from the image sensor is used to correct an overflow image signal using an overflow signal output, desired image data can be obtained even when an overflow occurs. effective.

According to the present invention, the overflow sensor is provided in the image sensor, and the detection result is output as an overflow signal separately from the image signal output. It can be easily determined which pixel the light has entered.

[Brief description of the drawings]

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

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

FIG. 3 is a waveform chart showing waveforms and timings of output signals of the circuit of FIG. 2;

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

FIG. 5 is a plan view illustrating an example of a position of an overflow area according to a 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.

FIG. 7 is a potential cross-sectional view showing a potential cross-section taken along line AB of the image sensor of FIG. 6;

FIG. 8 is a timing chart showing timings of signals for driving the image sensor of FIG. 6;

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

FIG. 10 is a waveform chart showing a relationship between an overflow output and an image output in the state of FIG. 9;

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 of the image sensor of FIG. 11 along line CD.

13 is a timing chart showing the timing and waveform of an output signal of a drive signal 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 Signs List 101 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 selection unit 114 LOG conversion unit 115 determination unit 116 operation control unit 117 operation unit 312 Multi-line delay circuit 315 Judgment unit and memory 501 Charge-voltage converter 502 Gate (A) 503 Comparator 504 Latch 601 Photodiode 602 Shift gate (B) 603 CCD (B) 604 Shift gate (A) 605 CCD (A) 801 Photodiode 802 CCD

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshinori Ikeda 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Shizuo Hasegawa 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon 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. (56) References JP-A-61-158279 (JP, A) JP-A-61-141273 (JP, A) JP-A-1-170167 (JP, A) JP-A-55-10283 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1/40-1/409 H04N 1 / 46 H04N 1/60 H04N 5/330-5/335

Claims (7)

(57) [Claims] An image sensor that outputs an overflow detection signal in addition to an image signal; and correcting the image signal by replacing the image signal in an 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 previously input from external input means. 3. The image processing apparatus according to claim 2, wherein the predetermined correction signal is image data generated by primary or secondary complement based on a value of an image signal in a portion adjacent to an overflow area. 2. The image reading device according to 1. 4. The image sensor according to claim 1, wherein the image sensor outputs the overflow detection signal indicating that the saturation voltage has been reached when the amount of light that exceeds the saturation voltage is incident. The image reading device according to claim 1. 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 accumulation time. 6. The image reading apparatus according to claim 4, wherein the overflow detection signal is output for each pixel of the photodiode of the image sensor. 7. The image sensor, comprising: a photodiode unit; and detection means for detecting, when light having a voltage equal to or higher than a saturation voltage is incident on the photodiode unit, charges discharged to the photodiodes on both sides of the incident photodiode. The image reading apparatus according to claim 4, further comprising: outputting a detection result of the detection unit as the overflow detection signal.