JPH0810161B2 - Color sensor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a color sensor for discriminating the color of incident light.

(Prior Art) Various color sensors have been developed.

In the color sensor shown in FIG. 9A, p layer 1, n layer 2 and p layer 3 are sequentially formed on a single crystal silicon base material. As shown in the equivalent circuit of FIG. 9B, two pn junctions are connected in opposite directions. Assuming that the photodiode with the shallower pn junction is PD1 and the photodiode with the deeper pn junction is PD2, the front side PD1 has high blue sensitivity, while the PD2 has the infrared side, as shown in Figure 10. Has a peak sensitivity. The color can be identified from the ratio of the sensitivities of the two photodiodes PD1 and PD2.

However, in order to handle visible light, it is necessary to add an infrared cut filter, which complicates the structure. FIG. 11 shows the spectral sensitivity characteristics when an infrared cut filter is added.

FIG. 12 shows a color sensor in which amorphous silicon (hereinafter abbreviated as a-Si) and a three-color separation filter are combined (Nakano et al., Proc. Of the 43rd Japan Society of Applied Physics. P318).
On the glass substrate 11, the transparent electrode layer 12 and the a-Si layer (p-i-
n) 13 are sequentially laminated, and back electrodes 14, 15, 16 corresponding to three colors (R, G, B) are further formed. On the other hand, on the lower side (incident light side) of the glass substrate 11, filters 17, 18 and 19 of three colors are provided on the electrode 1
Adhere facing 4,15,16. After the incident light is separated into three colors by the three-color separation filters 17 to 19, photoelectric conversion is performed in the a-Si layer 13, and the color of the light is discriminated from the electric signal. This color sensor has the drawbacks of complicated structure and high cost.

The a-Si contact image sensor shown in FIG. 13 can discriminate the color of light without using a color filter. This sensor (refer to Japanese Patent Laid-Open No. 59-99863) is
Metallic electrodes 22, 22, ..., Non-doped a-Si layer 23, transparent electrode layer 24
Are sequentially formed.

By changing the voltage applied to the a-Si light receiving surface, color discrimination is performed by applying the phenomenon of different spectral sensitivity characteristics. Any two bias voltages with different values (for example,
The ratio of the two photocurrents when 0 V and a predetermined bias value are added is calculated. The relationship between the photocurrent ratio and the wavelength of light is obtained in advance. Therefore, the color of the emitted light can be discriminated from the calculation result.

In this sensor, since the photoelectric section is composed of a non-doped a-Si film, the rate of change of photocurrent due to bias voltage is small, and it is difficult to identify color information. In addition, since the transparent electrode 24 is not separated in each pixel, different voltages cannot be applied at the same time, so that the color information cannot be read in real time.

(Problems to be Solved by the Invention) As described above, the conventional color sensor requires a complicated structure such as addition of a color filter or an infrared cut filter on the light incident side, and also, in real time. There was a problem that it was not possible to distinguish the colors.

An object of the present invention is to provide a color sensor having a simple structure and capable of performing color discrimination in real time.

(Means for Solving the Problems) A color sensor according to the present invention is a color sensor that absorbs light and determines a color. In the color sensor, two first electrically isolated elements are formed on an insulator. An electrode, a single layer of an impurity-implanted amorphous silicon layer laminated on the first electrode and the insulator, and two transparent electrodes provided on the amorphous silicon layer so as to face the first electrode. Consists of
The first electrode, the amorphous silicon layer, and the transparent electrode constitute two photoelectric conversion elements composed of an electrode pair composed of a first electrode and a transparent electrode facing each other, and an amorphous silicon layer, and further two electrode pairs. And a voltage applying means for simultaneously applying voltages having different polarities to each other, and an arithmetic means for determining a color from the ratio of the photocurrents of the two photoelectric conversion elements.

(Operation) The color sensor according to the present invention has an electrode pair including at least two electrodes that are substantially electrically separated and at least two transparent electrodes that face the electrodes. Therefore, different voltages can be applied to the photoconductor layer at the same time, and the color of incident light can be discriminated in real time.

(Examples) Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic plan view showing the structure of a color sensor 30 according to an embodiment of the present invention, and FIG. 2 is an A in FIG.
It is a sectional view taken along the line -A '. Two lower electrodes 32a and 32b are formed on the insulating substrate 31 by patterning, and a photoconductor layer 33 is further formed thereon. On top of that, the lower electrode 32
The transparent electrodes 34a, 34 are deposited so as to face the a, 32b. In this embodiment, the insulating substrate 31 is made of glass and the lower electrodes 32a and 32b are provided.
Chromium, amorphous silicon hydride for the photoconductor 33, and indium tin oxide for the transparent electrodes 34a and 34b.

 Hereinafter, a method for manufacturing the color sensor 30 will be described.

First, the lower electrodes 32a and 32b are formed by depositing chromium on a glass substrate to a thickness of about 2000Å by a DC sputtering method and patterning it into the shape shown in FIG. 1 by a photolithography method. Next, amorphous hydrogenated silicon is deposited to a thickness of about 5000Å by the glow discharge method to form the photoconductor 33. The conditions for forming the film at this time were that the concentration of B ₂ H ₆ with respect to SiH ₄ was 5 ppm, the gas flow rate was 300 SCCM, and the pressure was 1
Torr, RF power 10W, substrate temperature 250 ° C, film deposition time approx.
40 minutes. On top of this, a transparent conductive film of indium tin oxide is deposited by the RF sputtering method. 95mol% In ₂ O ₃ + 5mol
% SnO ₂ is used as the target. The film forming conditions at this time are as follows: Ar pressure during sputtering is 3 to 5 × 10 ⁻³ Torr and RF power is
It is 300W. Further, this transparent conductive film is patterned into the shape shown in FIG. 1 by photolithography to form upper transparent electrodes 34a and 34b.

Since the photoconductor 33 is doped with boron as an impurity, it exhibits the characteristics of a p-type semiconductor. Therefore, when the transparent electrode side is negatively biased, the holes, which are majority carriers generated near the surface by the light on the short wavelength side, are biased in the opposite direction to the lower electrode, which is difficult to contribute as a photocurrent. .

The data of the wavelength dependence of the photocurrent shown in FIG. 3 shows that the current value remarkably changes when the negative bias voltage is changed. On the contrary, when the transparent electrode is positively biased, the holes near the surface easily flow to the counter electrode, so that the sensitivity on the short wavelength side becomes high.

The data of an example of the wavelength dependence of the current shown in FIG.
When the positive bias voltage is changed, the change in current value is relatively small.

FIG. 5 shows the spectral sensitivity characteristics when the bias is reversed. I _P1 is the photocurrent when the transparent electrode is biased at −1 V and I _P2 is biased at +1 V, and the peak sensitivity wavelength is relatively shifted by reversing the bias voltage.

FIG. 6 is a graph showing the relationship of I _P2 / I _P1 corresponding to each wavelength. I _P2 / I _P1 decreases monotonically with increasing wavelength. Therefore, the color of the incident light can be determined by reading the output of the photocurrent ratio I _P2 / I _P1 from each pixel corresponding to each wavelength in the state where the bias is reversed in real time. In the present invention, since the photoelectric conversion part is made to be a p-type by injecting impurities such as boron, by reversing the bias voltage applied to the transparent electrode side,
The photocurrent ratio on the short wavelength side is increased to facilitate color discrimination.

FIG. 7 shows a schematic block diagram for driving the color sensor 30. In this embodiment, since the transparent electrode is separated for each pixel, different voltages can be applied at the same time. A variable resistor 42 for voltage division is connected in parallel to a power supply 41 for applying positive and negative voltages to the transparent electrodes 34a, 34b, and a sliding point is grounded. Amplifiers 43a and 43b for current amplification are connected to the two lower chrome electrodes 32a and 32b, and after the minute current is amplified, the divider 44
The ratio of _P1 and I _P2 is taken, and the result of I _P2 / I _P1 is output to the output Vout.

By determining the wavelength corresponding to the output Vout in the graph of the wavelength dependence of I _P2 / I _P1 shown in FIG. 6, the wavelength of the light incident on the color sensor 30 can be determined and the color discrimination can be performed.

Even when the photoconductor 17 is of the n-type, similar results can be obtained by only changing the majority carriers to electrons.

Also, as shown in FIG. 8, a large number of metal electrodes 32 ', 3
By providing 2 ', ... And the transparent electrodes 34', 34 ', .., which are opposed to this, a line color sensor in which a large number of two color sensors are arranged can be constructed.

In the present invention, since the photosensor portion is made of an amorphous silicon thin film, the conductive conversion portion is made of glass,
It is characterized in that it can be formed on various ceramic insulators. In the embodiment shown in FIG. 2, the glass substrate 31
Although the color sensor is formed on the upper side, for example, when a photoconductive material is deposited on the lens of a video camera or the like, it can be used as a color sensor for color correction. As a result, since the film can be directly deposited on the lens, the number of parts can be reduced.

(Effect of the invention) Since the color of light can be discriminated without using a color filter, the structure of the color sensor is simple, the manufacturing process of the sensor is simplified, and the cost can be reduced.

Since different voltages can be applied simultaneously, color discrimination can be performed in real time.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a color sensor according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line AA ′ of FIG. 3 to 5 are graphs of wavelength dependence of photocurrent. FIG. 6 is a graph showing the wavelength dependence of I _P2 / I _P1 . FIG. 7 is a circuit diagram for detecting I _P2 / I _P1 from the color sensor. FIG. 8 is a sectional view of the line color sensor. 9A and 9B are a sectional view and an equivalent circuit diagram of a color sensor including two pn junctions, respectively. FIG. 10 and FIG. 11 are graphs of the spectral sensitivity characteristics of the color sensor of FIG. 9 (a), respectively. FIG. 12 is a cross-sectional view of a color sensor using a color filter. FIG. 13 is a sectional view of the contact image sensor. 31 ... Insulator, 32a, 32b ... Electrode, 33 ... Photoconductor layer, 34a, 34b ... Transparent electrode.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-59-99863 (JP, A) JP-A-58-125869 (JP, A) JP-A-59-4184 (JP, A) JP-A-61- 283837 (JP, A)

Claims (1)

[Claims] 1. A color sensor that absorbs light and determines a color, wherein two first electrodes that are electrically separated from each other are formed on an insulator, and are laminated on the first electrode and the insulator. The single-layer amorphous silicon layer into which impurities are injected, and the two transparent electrodes provided on the amorphous silicon layer so as to face the above-mentioned first electrode. These first electrode, amorphous silicon layer, and The transparent electrode comprises two photoelectric conversion elements composed of an electrode pair consisting of a first electrode and a transparent electrode facing each other and an amorphous silicon layer, and further, voltages of different polarities are simultaneously applied to the two electrode pairs. A color sensor comprising: a voltage applying unit; and an arithmetic unit that discriminates a color from a ratio of photocurrents of two photoelectric conversion elements.