JP3227249B2 - Image sensor - 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 sensor used in an image information processing apparatus such as a facsimile, an image scanner, and a copying machine, and in particular, converts not only visible light but also an optical signal in an invisible light range into an electric signal. Related to the image sensor.

[0002]

2. Description of the Related Art A conventional solid-state image sensor which is an image sensor is a charge-coupled device (CCD) type, a MOS type, or described in US Pat. No. 4,791,469 issued to Tadahiro Omi and Nobuyoshi Tanaka. 2. Description of the Related Art There is known an amplification type device in which a capacitive load is connected to an emitter of an optical transistor.

[0003] In recent years, their applications have been diversified, and a solid-state imaging device having a new function has been demanded.

[0004] For example, in addition to high image quality and colorization of copying machines, there is a demand for recognizing invisible images and reproducing and recording them. Examples of such an image, that is, an invisible light image, include an image formed with an ink having a characteristic of absorbing infrared rays.

[0005]

In general, a sensor for detecting invisible light is an individual device and detects an image or the like.
Some new design philosophy is needed to use it together with the sensor for visible light detection.

As a basic design concept, the present inventors have first found a technique in which a sensor for detecting visible light and a sensor for detecting invisible light are monolithically housed in one semiconductor chip.

[0007] However, there is room for further improvement in the above technology.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a small-sized image sensor capable of detecting an optical signal in a wide wavelength range from a visible light region to an invisible light region and performing signal processing relatively easily. .

An object of the present invention is to provide a plurality of photoelectric conversion elements for converting a light signal in a visible light region into an electric signal and a plurality of photoelectric conversion elements for converting a light signal in a non-visible light region into an electric signal. An image sensor arranged in an array, wherein the plurality of photoelectric conversion elements that convert the optical signal in the visible light region into an electric signal, an infrared cut filter and a color filter are stacked on the light receiving portion. Is formed,
A plurality of photoelectric conversion elements for converting an optical signal in the invisible light region into an electric signal include a polycrystalline silicon layer and a blue
Layered structure with color filter, or red filter and blue
This is achieved by an image sensor in which a visible light cut filter having a laminated structure with a color filter is formed. Further, the above object is to provide an illuminating means for illuminating an original with light in a wavelength region necessary for obtaining an optical signal in a visible light region and an invisible light region, A plurality of photoelectric conversion elements for converting a signal, and a plurality of photoelectric conversion elements for converting an optical signal in an invisible light region obtained from the document into an electric signal, are arranged in an array, and The plurality of photoelectric conversion elements for converting an optical signal into an electric signal are formed by laminating an infrared cut filter and a color filter on a light receiving portion thereof, and convert the optical signal in the invisible light region into an electric signal. a plurality of photoelectric conversion elements is provided at its light receiving portion, Tayui
Laminated structure of crystalline silicon layer and blue filter, or red
This is achieved by an image information processing apparatus comprising: an image pickup unit provided with a visible light cut filter having a laminated structure of a color filter and a blue filter . Further, the object is to illuminate an original with light in a wavelength region necessary for obtaining an optical signal in a visible light region and an invisible light region, and an optical signal in a visible light region obtained from the original. A plurality of photoelectric conversion elements for converting an electric signal into one electric signal and a plurality of photoelectric conversion elements for converting an optical signal in an invisible light region obtained from the document into a second electric signal are arranged in an array; The plurality of photoelectric conversion elements for converting an optical signal in the visible light region into an electric signal are formed by stacking an infrared cut filter and a color filter on a light receiving portion thereof, and the light in the non-visible light region is formed. A plurality of photoelectric conversion elements for converting a signal into an electric signal, an imaging unit having a visible light cut filter formed on a light receiving unit thereof, an image forming unit for forming an image based on the first electric signal, From the electric signal of 2 Determining means for determining whether or not the document has a specific pattern of invisible light; and control means for controlling an operation of the image forming means based on an output of the determining means. This is achieved by an image information processing device.

[0010]

According to the present invention, since the photoelectric conversion element for visible light and the photoelectric conversion element for non-visible light are arranged in-line, both light signals can be easily detected by a small-sized device.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic top view for explaining one embodiment of the present invention. On the main surface side of the image sensor 1, a photoelectric conversion element (R, G, B) for converting a light signal in the visible light region into an electric signal and a photoelectric conversion element (R) for converting a light signal in the invisible light region into an electric signal ( IR) are substantially linearly arranged. Therefore, optical signals can be detected in a wide range between the invisible light region and the visible light region, and a high-performance image sensor can be obtained.

As the photoelectric conversion element of the present invention, a photovoltaic element or a photoconductive element such as a photodiode or a phototransistor is preferably used.

As a photoelectric conversion element for converting an optical signal in the visible light region into an electric signal, an element made of a material capable of selectively absorbing only the optical signal in the visible light region, or transmitting an optical signal in the visible light region. An element having a filter that blocks light in a wavelength region used for photoelectric conversion by another photoelectric conversion element in the invisible light region is used.

Specifically, in order to obtain a black-and-white signal, the constituent materials of the elements are selected so as to have a selective sensitivity in a wavelength region from 400 nm to 700 nm as a visible light region, or the above-mentioned wavelength region is selected. The element is provided with a filter that selectively transmits light.

In order to obtain an optical signal in a specific region in the visible light region, an element may be made of a material having a sensitivity selectively in the specific region, or the light in the specific region may be selectively used. The element is provided with a filter that transmits light through the element.

Then, for example, red (R), green (G),
In order to obtain a color signal such as blue (B), an element (R element) having selective sensitivity in an R region (for example, a wavelength region from 580 nm to 700 nm) and a G region (for example, 480)
An element (G element) having a selective sensitivity in a wavelength region from nm to 580 nm and a B region (for example, from 400 nm to 48 nm).
A plurality of types of elements (elements B) having selective sensitivity in a wavelength region of 0 nm are used.

Of course, also in this case, the material itself has the R, G,
Each element may be composed of a material that selectively absorbs light in each of the B regions, that is, a material having selective sensitivity, or each of R, G, and B that has sensitivity in all regions of R, G, and B. Each element is configured by including a filter that selectively transmits light in the B region.

FIG. 2 is a graph showing typical spectral characteristics of transmitted light of the filter. The relative sensitivity on the vertical axis corresponds to the transmittance of visible light. When each element is provided with selective sensitivity by selecting a material, for example, each element is formed using a material having a light absorption characteristic corresponding to a relative sensitivity as shown in FIG.

In the present invention, the visible light region, the invisible light region, and the R, G, and B wavelength regions are not clearly distinguished by the value of the wavelength. The elements are UV, blue,
It suffices if the configuration is such that green, red, and infrared light are photoelectrically converted by a required amount, and unnecessary light is not substantially photoelectrically converted.

On the other hand, as a photoelectric conversion element for converting an optical signal in an invisible light region into an electric signal, for example, an element having selective sensitivity to ultraviolet light or infrared light is used. In this case as well, the material itself has a selective sensitivity to light in the invisible light region to constitute an element, or a material having sensitivity to a wide wavelength region including the invisible light region has an invisible light region. It is desirable to combine filters having a selective transmittance to light.

For example, FIG. 3 is a graph showing typical spectral characteristics of transmitted light of the above-mentioned filter. The relative sensitivity on the vertical axis corresponds to the transmittance of invisible light. Here, an example of a filter having a selective sensitivity in an infrared region (for example, a wavelength region of 750 nm or more) is described, but the filter is not limited thereto.

In the solid-state imaging device according to the present invention, as shown in FIG. 1, the R, G, B, and IR elements can be periodically arranged in a line to form a color line sensor. Preferably, one image at a resolution as a color signal has an element having selective sensitivity to an R region (R element), an element having selective sensitivity to a G region (G element),
An element having a selective sensitivity in the B region (B element) and an element having a selective sensitivity in the invisible light region (IR element) are included.

The three-dimensional image or the two-dimensional image is used to generate an optical signal to be detected. A typical example of the two-dimensional image is a planar image of a document or the like. Therefore, when used in a system that reads an image of an original, it is desirable to provide an illuminating unit for illuminating the original surface. Such lighting means include light emitting diodes, xenon lamps,
There are light sources such as halogen lamps. FIG. 4 shows typical light emission distribution characteristics of the light source. The light source only needs to generate light in a necessary wavelength range in accordance with the optical signal to be detected, and is not limited to the light source having the characteristics shown in FIG. By using a light source that generates light having at least the characteristics shown in FIG. 4, infrared light as R, G, B, and invisible light regions can be obtained.

In the following, a laminated structure of filters shown in FIGS. 5, 7, 10 and 11 is preferably used. In this case, the photoelectric conversion elements are monolithic with four independent lines each having R, G, B and IR parallel to each other. May be configured.

[0025]

EXAMPLES Hereinafter, each example of the present invention will be described in detail. However, the present invention is not limited to each example, and the scope of the present invention is not limited as long as the object of the present invention is achieved. It is possible to change the replacement of each constituent element and the selection of the material.

Embodiment 1 FIG. 5 is a cross-sectional view schematically showing a solid-state imaging device as an image sensor according to Embodiment 1.

On the photodiodes 101 to 104 as photoelectric conversion elements formed on one Si substrate 100, a filter for realizing the function according to the present invention is formed.

The photodiodes 101 to 103 absorb a light signal in the visible light region, and the photodiode 104 absorbs a light signal in the infrared region as a non-visible light region to generate light carriers. For this purpose, an infrared cut filter 105 is formed on the photodiodes 101 to 103.
The infrared cut filter 105 can be manufactured, for example, by a method using light interference. That is, a low-refractive-index material such as SiO ₂ and a high-refractive-index material such as TiO ₂ are alternately laminated in a thin film shape, thereby realizing the characteristics as shown in FIG. Such a filter 105 is processed into a desired pattern so as to be formed only on a desired area. On the infrared cut filter 105, R, G, and B filters 106 through which light in the R region, the G region, and the B region in the visible light region are transmitted so as to correspond to each of the photodiodes 101 to 103.
108 are formed respectively. R, G, B filters 10
Nos. 6 to 108 can be manufactured by, for example, a method utilizing selective absorption of light. That is, using a dyeable resin having photosensitivity, after forming a pattern in advance,
Examples include a “staining filter” for dyeing with a dye, and a “colored resist filter” for mixing a dye in a photosensitive resin and forming a colored resin pattern only by photolithography using the dye. For example, as shown in FIG. The spectral characteristics of each visible region can be obtained.

On the other hand, a visible light cut filter 109 is formed on the photodiode 104 for reading information in the infrared region. The visible light cut filter 109 can be similarly realized by a method using the above-described light interference or a method using the selective absorption of light.
In this embodiment, for example, the spectral characteristics as shown in FIG. 3 are realized by forming the R filter 110 and the B filter 111 so as to overlap each other.

FIG. 5 shows an R element, a G element, a B element and an IR element.
A solid-state imaging device having one element at a time is described as an example, but the solid-state imaging device as shown in FIG. 1 is configured by arranging a plurality of pixels as one pixel in an array.

(Embodiment 2) FIG. 7 is a schematic sectional view showing a solid-state imaging device as an image sensor according to Embodiment 2.

The difference from the first embodiment lies in the structure of the photoelectric conversion element for converting an optical signal in the infrared region into an electric signal. The other structure is the same as that of the first embodiment.

On the photodiode 104, a polycrystalline silicon layer (p-Si layer) 113 and a B filter 112 are stacked. This B filter is the same as the B filter 108 in FIG. 5, and exhibits spectral characteristics as shown in FIG.

On the other hand, by changing the thickness of the p-Si layer 113, the characteristics (absorption characteristics) in the wavelength region of 500 nm or less can be made the desired characteristics. The characteristics can be given to the filter 109.

(Embodiment 3) FIG. 10 is a schematic sectional view showing a solid-state imaging device as an image sensor according to Embodiment 3.

The difference from the first embodiment is that the structure of the photoelectric conversion element for converting an optical signal in the infrared region into an electric signal and the filter 1
The arrangement is the same as that of the first embodiment except for the arrangement of the filter 05 and the filter 107.

An R filter 114 and a B filter 115 are stacked on the photodiode 104. The R filter 114 and the B filter 115 correspond to the R filter in FIG.
The filter is the same as the filter 106 and the B filter 108, respectively, and exhibits almost the same spectral characteristics as those shown in FIG.

Fourth Embodiment FIG. 11 is a schematic sectional view showing a solid-state imaging device as an image sensor according to a fourth embodiment.

The difference from the first embodiment is that the filters 106, 1
The arrangement positions of 07, 108, 110, and 111 are the same as those of the first embodiment.

Here, the IR filter 105, the G filter 107, the B filter 108, and the B filter 108 are formed so that each filter can be formed on the photodiode as accurately as possible.
11 and a flattened layer 116 is provided.
On the flat surface of the layer 116, the filters 107, 108,
111 are formed adjacently, on which another planarized layer 117 is provided. On the flat surface of the layer 117, the R filters 106 and 110 are provided separately from each other. A similar flattened layer 118 is formed on the R filters 106 and 110 to form a flat light incident surface.

As these layers 116, 117 and 118, for example, transparent films having a refractive index of about 1.49 are used.

(Scanning Circuit) The above-described solid-state imaging device as an image sensor is configured as an integrated circuit in which a scanning circuit as a readout circuit is integrated integrally with a pixel array including a photoelectric conversion element on the same substrate. Is desirable. As such a scanning circuit, a CCD shift register, a CCD transfer gate, a shift register using a transistor, and a transfer gate using a transistor are used alone or in appropriate combination. Also, a storage capacitor for storing the photoelectrically converted electric signal may be provided as necessary.

In the configuration shown in FIG. 12, after the signals of the respective photodiodes shown in FIG. 1 are transferred to the CCD register, the signals are sequentially read out in a serial format, for example, in the order of R, G, B, and IR.

FIG. 13 shows another structure in which the R, G, and B signals of the photodiode signals are transferred to a visible CCD register for the visible CCD register, and the R, G, and B signals are transferred to the infrared CCD register on the opposite side. , B and the serial output are separately read out in parallel.

FIG. 14 shows still another configuration. The signals of the respective photodiode arrays are simultaneously transferred to the respective storage capacitors corresponding to the respective photodiodes, temporarily stored, and then sequentially read out by the selective scanning circuit. At this time, since the output from the storage capacitor can be performed independently for each photodiode, the R, G, B, and IR signals can be read in a parallel format.

FIG. 15 shows still another configuration, in which R, G, B signals for visible light and IR signals for infrared light are read out separately in upper and lower parts.

An image information processing apparatus having the image sensor of each embodiment described above will be described.

The sensor 1 detects substantially the same point on the document as R
(Red), G (Green), B (Blue), and an infrared component having a sensitivity of about 1000 nm, and read at a pixel density of 400 dpi.

The output of the sensor is subjected to so-called shading correction using a white plate and an infrared light reference plate.
It is input to the identification unit 1001 and the image processing unit 1003 as a bit image signal. An image processing unit 1003 performs processes such as scaling, masking, and OCR performed in a general color copying machine, and generates four color signals of C, M, Y, and K as recording signals.

On the other hand, the discriminating unit 1001 as a discriminating means detects a specific pattern in the document, which is a feature of the present invention, and outputs the result to the recording control unit 1004, and if necessary, paints the image with a specific color. For example, faithful image reproduction is prohibited by processing the recording signal and recording it on recording paper by the recording unit 1005, or stopping the recording operation.

Next, an image pattern to be detected in the present invention will be outlined with reference to FIGS.

FIG. 17 shows that the light is almost transparent in the visible region and 800
It shows the spectral characteristics of a transparent dye that absorbs infrared light in the vicinity of nm, for example, SIR-159 of Mitsui Toatsu Chemicals, Inc. is typical.

FIG. 18 shows an example of a pattern formed by using a transparent ink composed of the transparent infrared absorbing dye. That is, one side is about 120 μm on a triangular pattern recorded with a specific, that is, ink a that reflects infrared light.
Is printed using the above transparent ink. Since the pattern is almost the same color in the visible region as shown in the figure, the pattern b is indistinguishable to human eyes, but can be detected in the infrared region. For the following description, a pattern of about 120 μm is shown as one row, but if this b area is read at 400 dpi, the size becomes about 4 pixels as shown. The method of forming the pattern is not limited to this example.

Referring to FIG. 19, the identification unit 10 shown in FIG.
01 will be described in detail. 10-1 to 10 in FIG.
-4 is an image data delay unit composed of FIFO,
The image data of 32 bits (8 bits × 4 components) is delayed by one line.

The input image signal is first supplied to the flip-flop 1
1-1 and 11-2 hold the pixel data of A by delaying by two pixels, the memories 10-1 and 10-2 further delay the pixel data of C by two lines, and FF11-3 and 11-4.
The target pixel data X delayed by two pixels in step
Similarly, the pixel data of D are simultaneously input to the determination unit 12 in the same manner as the pixel data of B delayed by two pixels in 5 and 11-6. Here, the vicinity A of the target pixel position X,
The positional relationship between the four pixels B, C, and D is as shown in FIG.

That is, if the pixel X of interest has read ink in the portion b in FIG.
Both C and D are reading the image of the pattern a located around them.

[0057] (determination algorithm) Now the R component constituting the pixel signal A A _R, a G component A _G, B component of the A _B infrared component in the same manner as A _IR B, C, each pixel signal of the D Are defined as R, G, B, and IR components. Then, the average values Y _R , Y _G , Y _B , and Y _IR of the same color component are obtained by the following equation. _{Y R = 1/4 (A} R + B R + C R + D R) Y G = 1/4 (A G + B G + C G + D G) Y B = 1/4 (A B + B B + C B + D B) Y IR = 1/4 ( _AIR + _BIR + _CIR + _DIR )

The target pattern is determined according to the difference between the average value Y and the target pixel X obtained by the above equations. _{That, ΔR = | Y R -X R} |, ΔG = | Y G -X G |, ΔB = | Y B -X B |, when the _{ΔI R = Y IR -X IR ΔR} <K ΔG <K ( If K and L are constants, it is determined that a pattern exists if ΔB <K ΔIR> L is satisfied.

That is, it can be determined that the target pixel has a small difference in tint in the visible region as compared with the surrounding pixels, and has a difference of a constant L or more in infrared characteristics.

FIG. 21 is an example of hardware that implements the above determination algorithm. The adder 121 simply adds each of the color components for each of the four pixels, outputs the upper 8 bits, and obtains Y _R , Y _G , Y _B , and Y _IR , respectively. Subtractor 1
22 finds the difference from each component of the pixel signal of interest,
The three components R, G, and B are compared in absolute value with a constant K as a reference signal by comparators 123, 124, and 125. On the other hand, the infrared component is compared with a constant L as a reference signal by a comparator 126. The output of each comparator is AND gate 12
7, when the output terminal is "1", the pattern is determined.

[Brief description of the drawings]

FIG. 1 is a schematic top view of a solid-state imaging device according to an embodiment of the present invention.

FIG. 2 is a diagram showing spectral characteristics of a color filter used in the present invention.

FIG. 3 is a diagram showing spectral characteristics of a visible light cut filter used in the present invention.

FIG. 4 is a diagram showing light emission characteristics of a light source used in the present invention.

FIG. 5 is a schematic sectional view of the solid-state imaging device according to the first embodiment of the present invention.

FIG. 6 is a diagram showing spectral characteristics of an infrared cut filter used in the present invention.

FIG. 7 is a schematic sectional view of a solid-state imaging device according to a second embodiment of the present invention.

FIG. 8 is a diagram showing spectral characteristics of a blue filter used in the present invention.

FIG. 9 is a diagram showing spectral characteristics of another visible light cut filter used in the present invention.

FIG. 10 is a schematic sectional view of a solid-state imaging device according to a third embodiment of the present invention.

FIG. 11 is a schematic sectional view of a solid-state imaging device according to a fourth embodiment of the present invention.

FIG. 12 is a block diagram illustrating an example of a scanning circuit of a solid-state imaging device used in the present invention.

FIG. 13 is a block diagram showing another example of the scanning circuit of the solid-state imaging device used in the present invention.

FIG. 14 is a block diagram showing still another example of the scanning circuit of the solid-state imaging device used in the present invention.

FIG. 15 is a block diagram showing another example of the scanning circuit of the solid-state imaging device used in the present invention.

FIG. 16 is a block diagram of a control system of the image information processing apparatus of the present invention.

FIG. 17 is a diagram showing a spectral characteristic of an infrared light absorbing dye used for a document which can be read by the image information processing apparatus of the present invention.

FIG. 18 is a schematic diagram showing a document that can be read by the image information processing apparatus of the present invention.

FIG. 19 is a block diagram illustrating a configuration of a determination unit in the image information processing apparatus of the present invention.

FIG. 20 is a schematic diagram for explaining a determination operation in the image information processing apparatus of the present invention.

FIG. 21 is a block diagram illustrating a detailed configuration of a determination unit illustrated in FIG. 19;

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Mamoru Miyawaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-63-82325 (JP, A) JP-A-4 -87453 (JP, A) JP-A-3-191302 (JP, A) Japanese Utility Model Application Sho 60-177571 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 27/14 H04N 1/028 H04N 5/33 H04N 5/335 H04N 9/07

Claims (6)

(57) [Claims] 1. A plurality of photoelectric conversion elements for converting a light signal in a visible light region into an electric signal and a plurality of photoelectric conversion elements for converting a light signal in a non-visible light region into an electric signal are arranged in an array. An image sensor, wherein a plurality of photoelectric conversion elements for converting the optical signal in the visible light region into an electrical signal, an infrared cut filter in its light receiving portion,
A plurality of photoelectric conversion elements for converting an optical signal in the non-visible light region into an electric signal, a polycrystalline silicon layer and a blue
Layered structure with color filter, or red filter and blue
An image sensor comprising a visible light cut filter having a laminated structure with a color filter . 2. The image sensor according to claim 1, wherein a flattening layer is interposed between the infrared cut filter and the color filter. 3. The image according to claim 1, wherein the plurality of photoelectric conversion elements for converting the optical signal in the visible light region into an electric signal generate three color separation signals of red, blue and green. Sensor. 4. The image sensor according to claim 1, wherein the light receiving unit includes a photo diode or a photo transistor. 5. An illuminating means for illuminating an original with light in a wavelength region necessary for obtaining optical signals in a visible light region and an invisible light region, and an electric signal in a visible light region obtained from the original. A plurality of photoelectric conversion elements for converting light signals in an invisible light region obtained from the document into electric signals are arranged in an array, and the light in the visible light region The plurality of photoelectric conversion elements for converting a signal into an electric signal are formed by stacking an infrared cut filter and a color filter on a light receiving portion thereof, and convert the light signal in the invisible light region into an electric signal. A plurality of photoelectric conversion elements have a polycrystalline silicon layer and a blue filter
Or red filter and blue filter
An image information processing apparatus, comprising: an image pickup unit on which a visible light cut filter having a laminated structure is formed. 6. An illuminating means for illuminating an original with light in a wavelength region necessary for obtaining optical signals in a visible light region and an invisible light region, and a first optical signal in a visible light region obtained from the original. A plurality of photoelectric conversion elements for converting into an electric signal, and a plurality of photoelectric conversion elements for converting an optical signal in an invisible light region obtained from the document into a second electric signal, are arranged in an array, The plurality of photoelectric conversion elements that convert the optical signal in the visible light region into an electric signal are formed by stacking an infrared cut filter and a color filter on a light receiving portion thereof,
A plurality of photoelectric conversion elements for converting the optical signal in the invisible light region into an electric signal, an imaging unit having a visible light cut filter formed in a light receiving unit thereof, and forming an image based on the first electric signal Image forming means; determining means for determining whether or not the document has a specific pattern of invisible light from the second electric signal; and controlling the operation of the image forming means based on an output of the determining means. An image information processing apparatus comprising: a control unit.