JPH06204444A - Image sensor - Google Patents

Abstract

PURPOSE:To obtain a small-sized image sensor which enables good signal detection in a wide wavelength region from the visible region to the invisible region and enables the signal processing to be performed in a relatively easy manner, by arranging photoelectric transducers for visible rays and photoelectric transducers for invisible rays in an array. CONSTITUTION:In an image sensor 1 for photoelectric conversion of optical signals to electric signals, a plurality of photoelectric photoelectric B for converting optical signals in the visible region to electric signals and a plurality of photoelectric transducers IR for converting optical signals in the invisible region to electric signals are arranged in an array. For instance, the respective elements of R, G, B and IR are periodically arranged in a line to form a color line sensor 1. Further, preferably, an image in resolution as a color signal includes an element having selective sensitivity to the R-region, an element having selective sensitivity to the G-region, an element having selective sensitivity to the B-region, and an element having selective sensitivity to the invisible region, respectively.

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 more particularly to converting an optical signal not only in visible light but also in invisible light into an electric signal. Related to the image sensor.

[0002]

2. Description of the Related Art As a solid-state image pickup device which is a conventional image sensor, a charge-coupled device (CCD) type, a MOS type, or the inventor Tadahiro Omi and Nobunyoshi Tanaka are described in U.S. Pat. No. 4,791,469. There is known an amplification type device in which a capacitive load is connected to the emitter of an existing phototransistor.

Recently, its applications have been diversified, and solid-state image pickup devices having new functions are required.

For example, in addition to high image quality and colorization of a copying machine, it has been required to recognize an invisible image and reproduce and record it. Examples of such an image, that is, an invisible light image include an image formed of ink having a characteristic of absorbing infrared rays.

[0005]

In general, a sensor for detecting invisible light is an individual device, which detects an image or the like.
Some new design concept is required for use with a sensor for visible light detection.

As a basic design concept, the present inventors first found out a technique of monolithically incorporating a sensor for detecting visible light and a sensor for detecting invisible light in one semiconductor chip.

However, there is room for further improvement in the above technique.

[0008]

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

The object of the present invention is to provide an image sensor for photoelectrically converting an optical signal into an electric signal. In the image sensor, a plurality of photoelectric conversion elements for converting an optical signal in the visible light region into an electric signal and an optical signal in the invisible light region are electrically converted. This is achieved by an image sensor characterized in that a plurality of photoelectric conversion elements for converting into signals are arranged in an array.

[0010]

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

[0011]

DESCRIPTION OF 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 an optical signal in the visible light region into an electric signal and a photoelectric conversion element (R, G, B) for converting an optical signal in the invisible light region into an electric signal ( (IR) are arranged almost in a straight line. Therefore, the optical signal can be detected in a wide range of 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 such as a photodiode or a phototransistor or a photoconductive element 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 the visible light region. However, an element having a filter that blocks light in a wavelength region used for photoelectric conversion in another photoelectric conversion element in the invisible light region is used.

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

Further, in order to obtain an optical signal in a specific region in the visible light region, an element is made of a material having a selective sensitivity in the specific region, or the light in the specific region is selectively selected. The element is equipped with a filter that passes through.

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

Of course, also in this case, the material itself is R, G,
Each element may be configured by one that selectively absorbs light in each region of B, that is, one that has selective sensitivity, or each element having sensitivity in all regions of R, G, and B may have R, G, 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 a filter, and the relative sensitivity on the vertical axis corresponds to the transmittance of visible light. When each element is given a selective sensitivity by selecting the material, for example, each element is formed by using a material having a light absorption characteristic corresponding to the 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, and the photoelectric conversion used in the present invention. The elements are UV, blue, to get each required signal
It suffices that the green light, the red light, and the infrared light are photoelectrically converted by a necessary amount, and unnecessary light is not substantially photoelectrically converted.

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

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

The solid-state image pickup device of the present invention can construct a color line sensor by periodically arranging each element of R, G, B, and IR in a line shape as shown in FIG. Preferably, one image in the resolution as a color signal has an element having a selective sensitivity in the R region (R element), an element having a selective sensitivity in the G region (G element),
It is configured to include an element (B element) having a selective sensitivity in the B region and an element (IR element) having a selective sensitivity in the non-visible light region.

A three-dimensional image or a two-dimensional image is generated as the optical signal to be detected, and a typical example of the two-dimensional image is a plane image of a document or the like. Therefore, when used in a system for reading an image of a document, it is desirable to provide an illumination means for illuminating the document surface. As such an illumination means, a light emitting diode or a xenon lamp,
There are light sources such as halogen lamps. FIG. 4 shows typical light emission distribution characteristics of the light source. The light source is not limited to the one having the characteristics shown in FIG. 4 as long as it can generate the light in the required wavelength region according to the optical signal to be detected. If at least a light source that emits light having the characteristics shown in FIG. 4 is used, it is possible to obtain infrared light in the R, G, B and invisible light regions.

The laminated structure of the filters shown in FIGS. 5, 7, 10 and 11 is preferably used below, and the photoelectric conversion elements in that case are monolithic with four independent lines in which R, G, B and IR are parallel to each other. It may be configured to.

[0025]

EXAMPLES Hereinafter, each example of the present invention will be described in detail, but the present invention is not limited to these examples, and is within the scope of the present invention as long as the object of the present invention can be achieved. It is possible to replace each constituent element in step 1 and change the material selection.

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

A filter for realizing the function of the present invention is formed on the photodiodes 101 to 104 as photoelectric conversion elements formed on one Si substrate 100.

The photodiodes 101 to 103 absorb the optical signal in the visible light region and the photodiode 104 absorbs the optical signal in the infrared region as the non-visible light region, respectively, to generate optical carriers. Therefore, an infrared cut filter 105 is formed on the photodiodes 101 to 103.
The infrared cut filter 105 can be manufactured by, for example, a method using light interference. That is, a low refractive index substance such as SiO ₂ and a high refractive index substance such as TiO ₂ are alternately laminated in a thin film form to realize the characteristics as shown in FIG. 6, for example. 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 to 106 that transmit light in the R region, G region, and B region of the visible light region so as to correspond to the photodiodes 101 to 103, respectively.
108 are formed respectively. R, G, B filter 10
6 to 108 can be manufactured by, for example, a method utilizing selective absorption of light. That is, after using a dyeing resin having photosensitivity and forming a pattern in advance,
Examples include a "dyeing filter" for dyeing with a dye and a "coloring resist filter" for mixing a dye into a photosensitive resin and forming a colored resin pattern only by photolithography using the same, such 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 in order to read information in the infrared region. The visible light cut filter 109 can be similarly realized by a method using the above-mentioned light interference or a method using the selective absorption of light.
In the present embodiment, the R filter 110 and the B filter 111 are formed so as to overlap with each other, thereby realizing the spectral characteristics as shown in FIG. 3, for example.

In FIG. 5, R element, G element, B element and IR
Although a solid-state image sensor having one element each is given as an example, the solid-state image sensor as shown in FIG. 1 is configured by arranging the elements as one pixel in a plurality of arrays.

(Second Embodiment) FIG. 7 is a schematic sectional view showing a solid-state image pickup device as an image sensor according to a second embodiment.

The difference from the first embodiment is the configuration of the photoelectric conversion element for converting an optical signal in the infrared region into an electric signal, and the other configurations are the same as those of the first embodiment.

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

On the other hand, since the p-Si layer 113 can have desired characteristics (absorption characteristics) in the wavelength region of 500 nm or less by changing its thickness, it is possible to cut visible light as shown in FIG. The characteristics can be given to the filter 109.

(Third Embodiment) FIG. 10 is a schematic sectional view showing a solid-state image pickup device as an image sensor according to the third embodiment.

The difference from the first embodiment is the configuration of the photoelectric conversion element for converting the optical signal in the infrared region into an electric signal and the filter 1.
No. 05 and the filter 107 are arranged, and other configurations are similar to those of the first embodiment.

An R filter 114 and a B filter 115 are laminated on the photodiode 104. The R filter 114 and the B filter 115 are the R in FIG.
They are the same as the filters 106 and B filters 108, respectively, and show almost the same spectral characteristics as those shown in FIG.

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

The points different from the first embodiment are the filters 106 and 1
07, 108, 110, and 111 are arranged, and other configurations are the same as those in the first embodiment.

Here, the IR filter 105, the G filter 107, the B filter 108, and 1 are arranged so that each filter can be formed on the photodiode as accurately as possible.
A planarized layer 116 is provided between the two.
On the flat surface of the layer 116, the filters 107, 108,
111 are formed adjacent to each other, on which another planarized layer 117 is provided. The R filters 106 and 110 are provided separately on the flat surface of the layer 117. A similar flattened layer 118 is formed on the R filters 106 and 110 to form a flat light incident surface.

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

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

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

FIG. 13 shows another configuration. Among the signals of the respective photodiodes, the R, G and B signals are transferred to the visible CCD register IR signal respectively to the infrared CCD register on the opposite side, and then the R and G signals are transferred. , B serial format output and IR output are individually read 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 therein, and then sequentially read by the selective scanning circuit. At this time, since the output from the storage capacitor can be independently performed for each photodiode, each signal of R, G, B, and IR can be read in a parallel format.

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

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

The sensor 1 uses the R
(Red), G (green), B (blue), and in addition, it is decomposed into an infrared component having a sensitivity of about 1000 nm and read at a pixel density of 400 dpi.

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

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

Next, an image pattern to be detected in the present invention will be outlined with reference to FIGS. 17 and 18.

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

FIG. 18 shows an example of a pattern made by using the transparent ink composed of the transparent infrared absorbing dye. That is, one side is approximately 120 μm on a triangular pattern recorded with a specific, ie, infrared-reflecting ink a.
The square minute pattern b is printed with the transparent ink. Since the pattern has almost the same color in the visible range as shown in the figure, the pattern of b cannot be recognized by human eyes, but can be detected in the infrared range. For the following description, a pattern of about 120 μm is shown as one column, but if the area of b is read at 400 dpi, the size is about 4 pixels as shown. The method of forming the pattern is not limited to this example.

The identifying section 10 shown in FIG.
The details of 01 will be described. 19-1-10-1
-4 is an image data delay unit composed of a FIFO,
Image data of 32 bits (8 bits × 4 components) is delayed by one line.

The input image signal is first flip-flop 1.
1-1 and 11-2 delay and hold two pixels for pixel A data, and memories 10-1 and 10-2 further delay two lines for C pixel data, and FFs 11-3 and 11-4.
The target pixel data X delayed by 2 pixels by
Similarly, the B pixel data delayed by two pixels in 5 and 11-6 are similarly input to the determination unit 12 as the D pixel data. Here, the neighborhood A of the pixel position of interest X,
The positional relationship among the B, C, and D4 pixels is as shown in FIG.

That is, if the pixel X of interest is reading the ink in the portion b of FIG. 18, then the above A, B,
Both C and D are reading the image of the a pattern located around it.

[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 Each of the R, G, B, and IR components that compose is defined. Then, the average values Y _R , Y _G , Y _B , and Y _IR of the same color components are calculated 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 (A _IR + B _IR + C _IR + D _IR )

The determination of the target pattern follows 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) ΔB <K ΔIR> L, it is determined that there is a pattern.

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

FIG. 21 shows an example of hardware that implements the above determination algorithm. The adder 121 simply adds the respective color components of 4 pixels and outputs the upper 8 bits thereof to obtain Y _R , Y _G , Y _B and Y _IR , respectively. Subtractor 1
22 obtains the difference from each component of the pixel signal of interest,
The absolute values of the three components of R, G and B are compared 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 is input to the output terminal, and if the output terminal is "1", the pattern is determined.

[Brief description of 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 a spectral characteristic of a color filter used in the present invention.

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

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

FIG. 5 is a schematic cross-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 the 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 cross-sectional view of a solid-state imaging device according to Example 4 of the present invention.

FIG. 12 is a block diagram showing an example of a scanning circuit of the 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 invention.

FIG. 17 is a diagram showing a spectral characteristic of an infrared light absorbing dye used for a document that 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 showing the configuration of a discriminating means in the image information processing apparatus according to the present invention.

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

FIG. 21 is a block diagram showing a detailed configuration of a discriminating means shown in FIG.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H04N 9/07 A 9187-5C (72) Inventor Mamoru Miyawaki 3-30-2 Shimomaruko, Ota-ku, Tokyo No. Canon Inc.

Claims (8)

[Claims] 1. An image sensor for photoelectrically converting an optical signal into an electric signal, wherein a plurality of photoelectric conversion elements for converting an optical signal in a visible light region into an electric signal and an optical signal in an invisible light region are converted into an electric signal. An image sensor having a plurality of photoelectric conversion elements arranged in an array. 2. The image sensor according to claim 1, wherein a plurality of photoelectric conversion elements for converting an optical signal in the visible light region into an electric signal generate a plurality of color separation signals. 3. The image according to claim 1, wherein a 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 photoelectric conversion element for converting an optical signal in the non-visible light region into an electric signal absorbs infrared rays to generate an infrared signal. 5. A plurality of photoelectric conversion elements for converting an optical signal in the visible light region into an electrical signal generate three color separation signals of red, blue and green, and electrically convert the optical signal in the invisible light region. The image sensor according to claim 1, wherein the photoelectric conversion element for converting into a signal absorbs infrared rays and generates an infrared signal. 6. The image sensor according to claim 1, wherein the photoelectric conversion element includes a photodiode or a phototransistor. 7. Illuminating means for illuminating an original to obtain an optical signal, a plurality of photoelectric conversion elements for converting an optical signal in the visible light region obtained from the original into an electric signal, and an optical signal in the invisible light region. An image information processing apparatus, comprising: a plurality of photoelectric conversion elements for converting an electric signal into an electric signal; and an imaging unit in which the photoelectric conversion elements are arranged in an array. 8. An illumination unit for illuminating an original to obtain an optical signal, a plurality of photoelectric conversion elements for converting an optical signal in the visible light region obtained from the original into a first electric signal, and a non-visible light region. A plurality of photoelectric conversion elements for converting the optical signal of the second electric signal into a second electric signal, and an image forming unit that forms an image based on the first electric signal; 2. An image information processing apparatus, comprising: a discriminating unit that discriminates the electrical signal 2 based on a reference signal; and a control unit that controls the operation of the image forming unit based on the output of the discriminating unit.