JPH11150628A - Optical waveguide type image sensor and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide (OWG) type image sensor capable of executing effective image reading and a control method for the sensor by preventing the generation of a deviation between the OWG pitch of an OWG array and the pixel pitch of a photoelectric conversion element array due to a change in temperature and adopting constitution of applying no stress to the OWG array. SOLUTION: An OWG type image sensor is composed of the OWG array 4 arraying plural OWGSs in its inside liken an array and the photoelectric conversion element array 6 optically combined with the array 4 and capable of receiving exit light from the array 4 and converting the received light into an electric signal. The sensor is constituted of arranging a Peltier element 6 in the vicinity of the connection part of the array 4 with the array 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical waveguide type image sensor used for a one-dimensional readout reduction optical system of a hard copy image and a control method thereof.

[0002]

2. Description of the Related Art In recent years, as the demand for reading images from facsimile machines, image scanners, digital copiers and the like has increased, there has been a demand for higher performance and smaller size of one-dimensional image sensors for converting image information into electric signals.

Conventionally, as a one-dimensional image sensor, a sensor type having a sensor length shorter than the width of a document and reading an image formed by a reduction optical system using a lens and a one-to-one optical system are used. There is a contact type image sensor that reads an image formed at the same magnification.

A reduced image sensor has a large depth of focus and is capable of high-speed reading. On the other hand, a long optical distance is required because light is condensed by a lens and reflected by a mirror, and as a result, the size of the device is reduced. It becomes large and it is difficult to reduce the size. Further, there is a disadvantage that the adjustment of the optical system is complicated, and adjustment is required for each unit.

On the other hand, a contact type image sensor has a short distance from a document to a photoelectric conversion element and does not require adjustment of an optical system, but has a small depth of focus and a low document reading speed.
Since the size of the photoelectric conversion element needs to be the same as the width of the document, there is a disadvantage that it is difficult to reduce the size of the apparatus.

Therefore, a reduction optical image sensor including a reduction optical system using an optical waveguide has been proposed. This is an optical waveguide type reduction image sensor that reduces the size of the original using the reflected light from the original surface, and includes a lens array formed over the original surface width and a plurality of optical waveguides for guiding the light collected by the lens array. An optical waveguide array is formed, and a photoelectric conversion element array that converts light guided by the plurality of optical waveguides into an electric signal. According to such an optical waveguide type reduced image sensor, the size and thickness of the device can be further reduced as compared with the above-described contact type image sensor and lens reduced optical image sensor, and complicated adjustment of the optical system can be performed. Becomes unnecessary.

As such an optical waveguide type image sensor, there is one in which a polymer material is used for an optical waveguide array, as described in JP-A-7-301730.
However, in this case, since the polymer material is used, when the linear expansion coefficient of the polymer material is different from the linear expansion coefficient of the photoelectric conversion element array material, the pitch of the core of the optical waveguide array and the photoelectric conversion element array A deviation occurs from the pixel pitch, making it difficult to perform accurate reading.

In order to solve such a problem, there has been proposed one as described in Japanese Patent Application Laid-Open No. 4-45654. In this technique, two holding plates are provided on the cladding layer surface of the polymer waveguide array, and the linear expansion coefficient of at least one of the holding plates is made equal to that of the photoelectric conversion element array. According to this, even when the ambient temperature changes, the polymer waveguide array is held by the side plate having the same linear expansion coefficient as the photoelectric conversion element array, so that the pixel pitch of the photoelectric conversion element array and the polymer waveguide The deviation from the core pitch of the waveguides in the array can be suppressed.

[0009]

However, according to the prior art described in Japanese Patent Application Laid-Open No. 4-45654, a large linear expansion coefficient is suppressed by a small linear expansion coefficient. If it changes, stress acts on the inside of the optical waveguide array, and peeling occurs particularly at the interface between the core and the clad of the waveguide, which adversely affects the waveguide loss.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and prevents a deviation between an optical waveguide pitch (core pitch) of an optical waveguide array and a pixel pitch of a photoelectric conversion element array due to a temperature change. In addition, by adopting a configuration in which the stress in the optical waveguide array does not act,
It is an object of the present invention to provide an optical waveguide type image sensor capable of performing good reading and a control method thereof.

[0011]

According to the first aspect of the present invention, there is provided an optical waveguide array in which a plurality of optical waveguides are arranged in an array, and the optical waveguide array includes: An optical waveguide type image sensor comprising: a photoelectric conversion element array which optically combines the light emitted from the optical waveguide array and converts the light into an electric signal, in the vicinity of a coupling portion of the optical waveguide array with the photoelectric conversion element array. And a Peltier element.

According to the first aspect of the present invention, since the Peltier element is arranged near the joint of the optical waveguide array and the photoelectric conversion element array, the linear expansion between the optical waveguide array and the photoelectric conversion element array is achieved. Even if the coefficient is different and the optical waveguide pitch (core pitch) of the optical waveguide array is shifted from the pixel pitch of the photoelectric conversion element array due to a temperature change,
The Peltier element can eliminate these misalignments. At this time, since an excessive stress does not act on the optical waveguide array, an optical waveguide defect does not occur, and a good reading can be realized without adversely affecting the waveguide loss.

Further, according to the second aspect of the present invention, an optical waveguide array in which a plurality of optical waveguides are arranged in an array, and light emitted from the optical waveguide array optically combined with the optical waveguide array. And a photoelectric conversion element array that receives light and converts it into an electric signal. The method for controlling an optical waveguide image sensor in which a Peltier element is disposed near a coupling portion of the optical waveguide array with the photoelectric conversion element array, The current flowing through the Peltier element is controlled according to the frequency component of the output signal from the conversion element array that is lower than the clock frequency.

According to the invention described in claim 2, according to claim 1,
Peltier element of the optical waveguide type image sensor described in
Since control is performed in accordance with a frequency component lower than the clock frequency in the output signal from the photoelectric conversion element array, the optical waveguide pitch (core pitch) of the optical waveguide array and the pixel pitch of the photoelectric conversion element array due to a temperature change can be easily determined. Deviation can be prevented.

According to a third aspect of the present invention, in the control method of the optical waveguide type image sensor according to the second aspect, the output signal from the photoelectric conversion element array in the plain original reading state of the optical waveguide type image sensor. Among them, the current flowing through the Peltier element is controlled so that the frequency component lower than the clock frequency becomes zero.

In the optical waveguide type image sensor according to the first aspect, when the optical waveguide pitch (core pitch) of the optical waveguide array and the pixel pitch of the photoelectric conversion element array are shifted in a plain original reading state, the photoelectric conversion element array is deactivated. Affects the output signal. Therefore, in the invention of claim 3, the current flowing through the Peltier element is feedback-controlled so that the frequency component of the output signal lower than the clock frequency of the photoelectric conversion element becomes zero, and the optical waveguide array is controlled by the Peltier element. Is to control the temperature of the coupling portion with the photoelectric conversion element array.

Therefore, according to the third aspect of the present invention, the output signal from the photoelectric conversion element array due to a shift in the mutual position between the optical waveguide pitch (core pitch) of the optical waveguide array and the pixel pitch of the photoelectric conversion element array. By directly controlling the current flowing through the Peltier element so that the low-frequency component is reduced to zero, the mutual position between the optical waveguide pitch (core pitch) of the optical waveguide array and the pixel pitch of the photoelectric conversion element array can always be maintained. Reading can be performed.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. Here, the reading width B
An embodiment applied to four sizes and a resolution of 200 dpi,
Although described as an example, the present invention is not limited to this.

FIG. 1 is a schematic perspective view showing the structure of an image sensor according to an embodiment of the present invention. As shown in FIG. 1, an optical waveguide type image sensor according to the present embodiment includes a document 1
Light emitting diode array 2 for irradiating the original surface of
Micro-lens array 3 for condensing the reflected light from the light source, an optical waveguide array 4 for guiding the light condensed by the micro-lens array 3 as optical information, and reducing the optical information from the optical waveguide array 4 It comprises a CCD (Charge Coupled Device) 5 which is a photoelectric conversion element array for converting into a signal. Further, in the optical waveguide type image sensor according to the present embodiment, the Peltier element 6 includes a Peltier element 6 in order to correct the mutual positional deviation between the optical waveguide pitch (core pitch) of the optical waveguide array 4 and the pixel pitch of the CCD 5 due to a temperature change. The optical waveguide array 4 is arranged near a portion where the optical waveguide array 4 is coupled to the CCD 5.

The size of the optical waveguide array 4 of the present embodiment is 260 mm (width) × 25 mm (height) × 1.5.
mm (thickness). In the optical waveguide array 4, the number of optical waveguides was 2048, the depth of the optical waveguide groove was 8 μm, the width of the optical waveguide groove was 8 μm, and the optical waveguide pitch was 125 μm at the light input end and 14 μm at the light output end. .

The CCD 5 used in this embodiment is
2048 pixels, pixel size 14μm × 12μ
m, pixel pitch is 14 μm, clock frequency is 3 MHz
belongs to.

Here, a method of manufacturing the optical waveguide array 4 of the present embodiment made of a polymer material will be described with reference to FIG. Various methods can be applied to the method of manufacturing the optical waveguide array used in the present invention. In this embodiment, the squeegee method is used.

First, a clad substrate 8 on which an optical waveguide groove 7 is formed is prepared (FIG. 2A). The material of the clad substrate 8 may be a transparent material having a lower refractive index than the material of the core portion forming the optical waveguide. In this embodiment, polymethyl methacrylate (PMMA, refractive index: 1.49) is used. Using this, a clad substrate 8 was produced by an injection molding method.

Next, a core material 9 having a higher refractive index than the clad material is applied onto the clad substrate 8 (FIG. 2).
(B)). Thereafter, the core material 9 other than the optical waveguide groove 7 is swept by the squeegee 10 and only the optical waveguide groove 7 is filled with the core material 9 (FIG. 2C). Then, UV 11
Is irradiated to cure the core material 9 (FIG. 2D). Then, a clad material 12 is applied to the upper part (FIG. 2E), and the clad material 12 is cured by irradiating ultraviolet rays 11 (FIG. 2F). In this embodiment, an ultraviolet curable resin having a refractive index of 1.52 is used as the core material 9.

Next, a CCD 5 as a photoelectric conversion element array is optically coupled to the optical waveguide array 4 manufactured as described above. In the present embodiment, the pitch of the optical waveguides of the optical waveguide array 4 is designed to match the pixel pitch of the CCD 5 when the room temperature is 20 ° C. Therefore,
In an environment at a room temperature of 20 ° C., the optical waveguide (core) of the optical waveguide array 4 and the pixels of the CCD 5 were aligned with each other so that they were aligned with each other by an optical adhesive.

Next, the Peltier element 6 is arranged on the substrate surface near the CCD 5 coupling portion of the optical waveguide array 4, and the fabrication of the optical waveguide image sensor is completed. In the present embodiment, the size and the position of the Peltier element 6 are set so as to cover all the 2048 optical waveguides at the output end of the optical waveguide array 4.

Next, the output from the CCD in the optical waveguide type image sensor according to the present embodiment will be described with reference to FIG.
3, the vertical axis indicates the output voltage (V) of the CCD 5, the horizontal axis indicates the element length of the CCD 5, and the horizontal axis 0 indicates the CC.
At the position of the center pixel along D5, it is assumed that there are the same number of left and right CCD pixels around the horizontal axis 0.

The linear expansion coefficient of PMMA, which is the cladding substrate material of the optical waveguide array 4 of the present embodiment, is 6.9 × 10 ^-5 / ° C., and the linear expansion coefficient of silicon of the pixels of the CCD 5 is 2 0.6 × 10 ⁻⁶ / ° C.

When the optical waveguide type image sensor of the present embodiment manufactured as described above is in a reading state of a white plain original as shown in FIG. 1, the optical waveguide pitch of the optical waveguide array 4 and the pixel of the CCD 5 are set. When the pitch matches, the output V ₁ of the 3MHz constant value of the CCD clock frequency is also obtained from the position of the throat CCD 5 (Fig. 3
(A)). However, if the temperature changes from this state, the difference in linear expansion coefficient between the optical waveguide array 4 and the CCD 5 causes
A shift occurs between the optical waveguide pitch of the optical waveguide array 4 and the pixel pitch of the CCD 5. Then, the output at the end pixel of the CCD 5 finally reaches the minimum value V ₀ (FIG. 3B). Actually, such a minimum value V ₀ was obtained when the ambient temperature was 27.4 ° C., and CC at that time was obtained.
The low frequency component of the output signal from D was f = 1.46 kHz.

If the mutual position between the extreme end of the optical waveguide of the optical waveguide array 4 and the extreme end of the pixel of the CCD 5 is shifted by one pixel, the output from the extreme end of the CCD 5 becomes the output V ₁ from the central pixel. Will be the same as However, the pixel output of an intermediate portion between the central portion and the outermost end of CCD5 becomes a minimum value V ₀ is lower than the pixel output of the others (Figure 3 (c)). Actually, such a minimum value V ₀ was obtained when the ambient temperature was 3
At 4.7 ° C., the low frequency component of the output signal from the CCD at that time was f ′ = 2f = 2.9 kHz.

Further, when the ambient temperature reaches 49.4 ° C.,
The mutual position between the extreme end of the optical waveguide of the optical waveguide array 4 and the extreme end of the pixel of the CCD 5 is shifted by two pixels, and the output from the CCD 5 is as shown in FIG. The component was f ″ = 4f = 5.8 kHz.

Here, the operating temperature of the CCD (−25 ° C. to 6
0 ° C.) and the glass transition temperature (80 ° C.) of PMMA of the cladding material of the optical waveguide array, the operating temperature of the optical waveguide image sensor of the present embodiment is −25 ° C.
It is in the range of 60 ° C. From this, the low frequency appearing on the CCD output is practically about 1 to 10 kHz.

From these, the control circuit system of the Peltier device of the optical waveguide type image sensor of the present embodiment was designed. The block diagram is shown in FIG.

As described above, if the mutual position between the optical waveguide pitch of the optical waveguide array 4 and the pixel pitch of the CCD 5 is shifted, a low frequency of about 1 to 10 kHz is generated in the output signal from the CCD 5. Therefore, in the present embodiment, as shown in FIG. 4, only low-frequency components are extracted from the output signal from the CCD 5 through a band-pass filter (1 to 10 kHz), and then sequentially passed through a rectifier circuit, a smoothing circuit, and a temperature switch.
A desired direct current is applied to the Peltier device 6. Then, the Peltier element 6 controls the temperature in the vicinity of the portion where the optical waveguide array 4 is coupled to the CCD 5.

The temperature switch used in this embodiment is:
At the standard temperature t = 20 ° C., the direction of the current flowing through the Peltier element 6 is switched. That is, when t = 20 ° C. or more, a current is supplied so as to cool the contact surface between the optical waveguide array 4 and the Peltier element 6, and when t = 20 ° C. or less, the contact surface between the optical waveguide array 4 and the Peltier element 6 is heated. The current is made to flow as described above.

In the optical waveguide type image sensor according to the present embodiment having the above-described configuration, the output signal of each pixel of the CCD 5 is constant in the white plain original reading state despite the change of the ambient temperature, and the pixel shift is caused. No error signal appeared. Then, when the document was actually read, good reading without noise could be performed.

In the above embodiment, the Peltier element 6 is
Although it is arranged individually, another one may be arranged on the back surface of the optical waveguide array 4. Further, a heat conductive film made of a metal film or the like having excellent heat conductivity may be provided in the vicinity of a portion of the optical waveguide array 4 where the optical waveguide array 4 is connected to the CCD 5.

FIG. 5 shows another embodiment of the optical waveguide type image sensor shown in FIG.
In the figure, a heat conductive film 14 formed by coating a metal film is provided in the vicinity of a portion connected to the CD 5, and a Peltier element 6 is disposed thereon. According to the heat conduction film 14, the heat conduction from the Peltier element 6 to the optical waveguide array 4 can be further improved.

[0039]

As described above, according to the first aspect of the present invention, since the Peltier element is arranged near the coupling portion of the optical waveguide array with the photoelectric conversion element array, the optical waveguide array and Even if the linear expansion coefficient of the photoelectric conversion element array differs from that of the photoelectric conversion element array, and the optical waveguide pitch (core pitch) of the optical waveguide array and the pixel pitch of the photoelectric conversion element array deviate due to a change in temperature, the Peltier element shifts these mutual positions. The displacement can be eliminated. At this time, since an excessive stress does not act on the optical waveguide array, an optical waveguide defect does not occur, and a good reading can be realized without adversely affecting the waveguide loss.

According to the second aspect of the present invention, the Peltier element of the optical waveguide type image sensor according to the first aspect is configured such that the Peltier element of the output signal from the photoelectric conversion element array has a frequency component lower than the clock frequency in the output signal. , It is possible to easily prevent the deviation between the optical waveguide pitch (core pitch) of the optical waveguide array and the pixel pitch of the photoelectric conversion element array due to a temperature change.

Further, according to the third aspect of the present invention, the low frequency component of the output signal from the photoelectric conversion element array due to a shift between the optical waveguide pitch of the optical waveguide array and the pixel pitch of the photoelectric conversion element array is reduced to zero. As described above, by directly controlling the current flowing through the Peltier element, the mutual position between the optical waveguide pitch of the optical waveguide array and the pixel pitch of the photoelectric conversion element array can always be maintained, and good reading can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a configuration of an optical waveguide type image sensor according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a manufacturing process of the optical waveguide type image sensor of the embodiment.

FIG. 3 is a diagram for describing pixel output depending on the position of a CCD in the optical waveguide type image sensor of the embodiment.

FIG. 4 is a block diagram illustrating a control circuit system of the Peltier device according to the embodiment.

FIG. 5 is a schematic perspective view illustrating a configuration of an optical waveguide type image sensor according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original 2 Light emitting diode array 3 Micro lens array 4 Optical waveguide array 5 CCD 6 Peltier element 14 Thermal conductive film

Claims (3)

[Claims] An optical waveguide array in which a plurality of optical waveguides are arranged in an array, and light emitted from the optical waveguide array is optically combined with the optical waveguide array and converted into an electric signal. An optical waveguide type image sensor comprising a photoelectric conversion element array, wherein a Peltier element is arranged near a coupling portion of the optical waveguide array with the photoelectric conversion element array. 2. An optical waveguide array in which a plurality of optical waveguides are arranged in an array, and optically combined with the optical waveguide array to receive light emitted from the optical waveguide array and convert the light into an electric signal. A photoelectric conversion element array, wherein a Peltier element is disposed in the vicinity of a coupling portion of the optical waveguide array with the photoelectric conversion element array, wherein an output signal from the photoelectric conversion element array is provided. Controlling the current flowing through the Peltier element according to a frequency component lower than the clock frequency. 3. The method for controlling an optical waveguide type image sensor according to claim 2, wherein:
A method for controlling an optical waveguide image sensor, comprising controlling a current flowing through the Peltier element so that a frequency component of a frequency lower than a clock frequency among output signals from a photoelectric conversion element array becomes zero.