JPH02220557A - image reading device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of an optical system in a part of a facsimile machine, digital copying machine, image scanner, etc. that performs image reading.

[Prior Art] A method of reading an image using a so-called contact type image sensor having a pixel row length that is the same as that of a document involves reading a same-magnification image formed using a self-focusing rod lens array. In this method, a photoelectric conversion element is brought close to the document surface and the reflected light from the document surface is directly read without forming an image. Both have extremely short optical path lengths compared to those that use a reduction type optical system, and the utilization of reflected light from the document surface is high, so it is possible to construct a compact and bright optical system, making it ideal for facsimiles and various image inputs. It is expected to be applied to devices. In particular, the latter does not require an optical element for image formation, making it possible to lower costs compared to the former, and expanding the range of applications of image reading devices in that it is possible to configure the layer device compactly. It is expected as such.

FIG. 2 shows an example of an optical system that directly reads the reflected light from the surface of the document. In the figure, a photoelectric conversion element 211 includes a lower electrode 202, a photoconductive layer 203, and a transparent upper electrode 204.
, and a large number of them are arranged in the direction perpendicular to the plane of the paper. An illumination window 231 is provided in the charging conversion element, and the illumination light 223 from the light source 221 is transmitted through the! 1
! ! The document surface 241 is exposed through the border transparent substrate and this illumination window.
reach. In this case, the lower electrode of the photoelectric conversion element also serves as a light shielding layer, and prevents light from the light source from directly entering the photoconductive layer. By scanning such an optical system in the direction of the paper surface, an image on the document surface can be read.

There are two types of reflected light from the document surface: one is caused by specular reflection on the document surface, and the other is light that is emitted after once entering the document surface. The former is emitted according to the angle at which the illumination light is incident, and contains almost no information about the density of the document surface. The latter is almost independent of the incident angle of the illumination light, is emitted from the document surface in a form that is nearly completely scattered, and contains information on the shading of the document surface. Hereinafter, the former will be referred to as surface reflected light and the latter as original light. In order to read the image on the surface of the document, it is necessary to allow only the light from the document to enter the photoelectric conversion element.

In the example shown here, since the illumination light is incident approximately perpendicularly to the document surface, the surface reflected light is emitted approximately perpendicularly to the document surface and returns toward the light source through the illumination window. Therefore, surface reflected light does not enter the photoelectric conversion element. Although the original light is most intensely emitted in the direction perpendicular to the original surface, it also contains many angular components, so a portion of it is incident on the photoelectric conversion element.

In this manner, the image on the document surface can be read.

[Problem M to be Solved by the Invention] As a light source for such an image reading system, a fluorescent tube or an LED array in which a large number of LEDs are arranged in one dimension can be used.

In the LED array, each LED is almost a point light source, and it is easy to control the angle at which the illumination light enters the illumination window, so the surface reflected light effectively enters the charging conversion element in the manner shown above. can be prevented.

Therefore, it is possible to perform reading with a higher S/N than the former. Furthermore, since LED is a solid-state light source, it has a long lifespan and is advantageous in that it requires no maintenance. For this reason, LEDs are generally used as light sources.

However, since the light from the LED has small directivity and it is difficult to concentrate the light only on the illumination window, the efficiency of light utilization becomes extremely low. Therefore, in order to obtain sufficient brightness for image reading, it is necessary to make the illumination window of the photoelectric conversion element considerably large. Although it is possible to use an optical system to collect light to compensate for this, the original advantages of low cost and compactness are lost.

Furthermore, since the illumination window cannot be made smaller, it is difficult to reduce the size of the photoelectric conversion element, which is a major obstacle in increasing the resolution of an imaging device.

Furthermore, since the LED array itself is a collection of point light sources and provides illumination without using any optical elements, variations in brightness in the longitudinal direction tend to become large. For this reason, significant sensitivity correction is required after reading, and there is a problem in that the S/N ratio of the image reading device decreases.

Therefore, the present invention is intended to solve such problems.
By using a light source with high directivity and high uniformity in the length direction, the aim is to increase resolution and improve S/N without sacrificing the low cost and compactness of this type of image reading device. .

[Means for Solving the Problems] In order to solve the above-mentioned problems, the image reading device of the present invention has an edge-emitting type N-film electroluminescent element that connects the end face of a substrate on which a photoelectric conversion element is formed. It is characterized by having a structure in which the end faces of the formed substrate are fixed so that the element surfaces are substantially parallel to each other or have an angle of 45 degrees or less.

Further, the device surface of the substrate on which the edge-emitting type thin film electroluminescent device is formed and the device surface of the substrate on which the charge conversion device is formed are fixed so as to have a step difference. Example] First, let's look at the edge-emitting type 11! which is an important component of the present invention! Electroluminescent element (hereinafter referred to as f & E T
I'll call it FEL. ) will be explained. ETFEL is proceeding of the
As seen in SID, Vol. 28.81 (1987), etc., the active layer of a thin film electroluminescent device is prepared under conditions such that it becomes a waveguide on the device surface. As shown in the figure.

In the figure, 301 is an insulating substrate, 302 is a lower electrode layer, 303 and 305 are dielectric layers, and 304 is an electroluminescent active layer. The lower electrode layer is a palladium film formed by sputtering and has a thickness of 100 OA. The dielectric layer is made of yttrium oxide (Y20311!) formed by electron beam evaporation and has a thickness of 2,500 OA. The active layer is formed by sputtering. The upper electrode layer is a zinc sulfide film (ZnS: Mn) added with manganese and has a thickness of 1.3μ.The upper electrode layer is an aluminum film formed by sputtering.
The film thickness is 4000 people.

The basic structure is the same as a normal WI membrane electroluminescent element used for display and illumination, and light emission occurs within the active layer by applying an alternating current voltage of several hundred Hz to several hundred kHz between the upper and lower electrodes. Since the structure is simple, it is relatively easy to form an element over a large area, and it is possible to manufacture an element with a long light emitting surface.

In a typical thin-film electroluminescent device, one of the electrodes is a transparent electrode, and light is extracted in a direction perpendicular to the device surface and used for display or backlighting. In such applications, since it is desired to reduce the driving voltage, the active layer is also made as thin as possible, and a value of about 5,000 to 8,000 is usually used.

On the other hand, if the device is to be used as an ETFEL, light must propagate within the active layer in a direction parallel to the device surface as shown at 310. Generally, the active layer has a higher refractive index than the dielectric layer, so a step-index waveguide can be constructed by utilizing this difference in refractive index.

In the case of devices used for normal displays and backlights, the active layer is thin, so sufficient propagation characteristics cannot be obtained as a waveguide. By increasing the thickness of this active layer, the propagation characteristics of this waveguide can be improved and it can be used as an ETFEL. The thicker the active layer, the more modes propagate within the waveguide and the better the propagation characteristics, but this increases the driving voltage and reduces the directivity of light emitted from the end facets, making it difficult to use for such purposes. becomes inconvenient. Therefore, although it depends on the color of the emitted light, the thickness of the active layer is 8,000 to 2μ.
It is better to take a value of about m.

Further, a transparent coating layer 307 made of glass or the like is provided on the ETFEL. This is to protect the element and increase the output efficiency by reducing the difference in refractive index at the emission end face of the ETFEL.It is made of transparent material such as phosphor glass or silicon oxide, and is used as a material between the active layer of the ETFEL and the air. A material with a refractive index is used.

Although specific materials are described here as the materials constituting the ETFEL, most of the materials constituting ordinary thin film electroluminescent elements can be used as long as they can constitute a waveguide. For example, materials for the dielectric layer include tantalum oxide (Ta203), alumina (A1203), silicon oxide, silicon nitride, barium titanate (BaT i 03), silicon oxynitride (810X).
In addition to zinc sulfide, cadmium sulfide (CdS) can be used as the material for the active layer.
), strontium sulfide (SrS), and materials in which these materials are dispersed in organic materials can also be used. In addition, the activators added to the active layer include copper, lead,
Terbinium, chlorine, fluorine, etc. can be used.

The present invention will be explained below with reference to Examples, and the ETFEL used as a light source here was manufactured by the method described above.

FIG. 1 is a sectional view showing an example of an image reading device according to an embodiment of the present invention. In the figure, it is assumed that the photoelectric conversion elements 111 are composed of a lower electrode 102, a photoconductive layer 103, and a transparent upper electrode 104, and are arranged in large numbers in a direction perpendicular to the plane of the paper. The lower electrode is a chromium film formed by sputtering and has a thickness of 2000 mm, and the photoconductive layer is an amorphous silicon film formed by plasma CVD and has a thickness of 8 mm.
The transparent upper electrode layer is an ITO film formed by sputtering and has a thickness of 2000.

Three passivation layers are provided on the photoelectric conversion element in order to improve reliability and protect the element from the surface of the original. Reference numerals 107 and 109 are passivation layers made of inorganic materials such as silicon oxide, which serve to improve moisture resistance and wear resistance. Reference numeral 108 is a passivation layer made of an organic material such as polyimide, which serves to flatten the surface of the element. Further, a conductive layer for shielding may be provided between the passivation layers in order to prevent the influence of static electricity due to friction with the surface of the document.

A substrate 122 on which a light source E T F E L 121 is formed has an element surface that is similar to the substrate 1 on which a photoelectric conversion element is formed.
The end face of the photoelectric conversion element was bonded to the end face of the substrate on which the photoelectric conversion element was formed so that it was substantially parallel to the element surface of 01. ETF
There is a stepped portion 15 of approximately 100 μm between the element surface of the substrate on which the EL is formed and the element surface of the substrate on which the photoelectric conversion element is formed.
1 is provided. This stepped portion can be created by changing the alignment reference when bonding the substrate on which the photoelectric conversion element is formed and the substrate on which the ETFEL is formed.

In addition, a spacer is placed on the surface of the photoelectric conversion element, and E
It can also be manufactured by fixing it at the same position as the end face of the substrate on which the TFEL is formed. In either method, alignment can be performed using only the element surfaces of each substrate as a reference, so assembly is easier than in the past.

Here, the ETFE appears on the ETFE from contact with the document surface.
A glass coating layer is provided to protect L. This layer also serves to increase the efficiency with which light is emitted from the end face of the ETFEL.

Further, the ETFEL must be activated at a frequency such that fluctuations in the amount of light do not affect the reading and scanning of the photoelectric conversion device. In the case of reading in the accumulation mode, which is normally used for such purposes, the scanning time is several ms, and in this case, a range of several kHz to several tens of kHz is appropriate in terms of efficiency and the like. When reading in current mode, a higher frequency is required, although it depends on the method.

The image on the document surface can be read by moving such an optical system horizontally over the document surface in the figure.

The stepped portion 151 prevents contact between the device surface and the document surface at this portion, and a space is formed over several hundred μI so that the document surface 141 is oblique to the device surface above the photoelectric conversion device. The light emitted from the ETFEL enters the document surface through this space. Since the light from the ETFEL is highly directional and spreads only about 100 μm even over a distance of several hundred μm, this light almost never directly enters the photoelectric conversion element. On the other hand, since the light from the document surface containing image information is emitted from the document surface in a direction almost perpendicular to the document surface, most of the light enters the photoelectric conversion element and is transmitted onto the document surface with high sensitivity and good S/N. It is possible to read images of

Image reading using such a method can be performed when the size of the stepped portion is in the range of about 30 μI11 to 500 μ−. However, if the size of the stepped portion is small, it is difficult to make the illumination light incident on the document surface, resulting in a decrease in sensitivity, and it becomes more susceptible to the influence of the state of contact with the document surface. If it is large, the distance between the document surface and the charge conversion element becomes large, and the MTF for image reading decreases. Therefore, in order to perform good reading, it is necessary to
It is desirable to set the value to about m.

Although it is desirable that the distance between the emission end face of the ETFEL and the substrate end face be as small as possible, it is possible to read the distance up to about 100 μm. However, if this distance is long, the emission end surface of the ETFEL may be blocked by the document surface depending on the state of contact with the document surface.
It is desirable that the thickness be 30 μm or less. If it is desired to increase the length of this part due to problems such as machining accuracy, it is possible to maintain the space at the emission end face of the ETFEL by fixing a spacer with a thickness of about 50 μm to 200 μm on the ETFEL.

Furthermore, depending on the thickness of this spacer, it is possible to adjust the position where the light from the ETFEL enters the document surface, and it can also be used as an adjustment part for optimizing reading performance.

The distance between the photoelectric conversion element and the edge of the substrate is
It is possible to make it considerably larger by adjusting the position of L and other parts such as spacers. However, in terms of stability of contact with the document surface, reading performance, etc., it is preferable that the thickness be as small as possible, and preferably 100 μm or less. Even with the current dicing accuracy, it is sufficient for mass production up to about 30 μm. The size of the charge conversion element in the sub-scanning direction can be determined relatively freely within a range where surface reflected light is not incident, but it goes without saying that it is desirable to set the size to less than the required resolution in the sub-scanning direction.

As described above, since this image reading device has a simple structure, it is easy to miniaturize the elements and achieve high resolution. Furthermore, since the illumination efficiency is high and reading can be performed with high sensitivity and good S/N, sufficient sensitivity and S/N can be ensured even when the resolution is increased. Additionally, there are no parts that are difficult to adjust or position, and mass production is high, making it possible to reduce costs compared to conventional methods.

Furthermore, because ETFEL is a linear light source, its brightness is highly uniform in the longitudinal direction (the direction in which photoelectric conversion elements are arranged), and there is no need to compensate for variations in the light source, which also reduces costs. It is possible to achieve this goal.

Furthermore, if a scanning circuit or the like is formed using a thin film, a transistor, etc. on the same substrate as the photoelectric conversion element, higher resolution of reading, lower cost, and smaller size of the device can be achieved.

In this way, when the illumination light is emitted in a direction parallel to the element surface, the angle at which the illumination light enters the document surface tends to become large. If the incident angle is large, a large proportion of the light reflected from the document surface becomes surface reflection. In order to increase the sensitivity of the image reading device, it is desirable to increase the angle of incidence of the illumination light onto the document surface.

FIG. 4(a) shows an example in which a thin film optical element is provided on the emission end surface side of the ETFEL in order to reduce the angle at which the light emitted from the ETFEL enters the document surface.

442 is made of a material with a lower refractive index than the glass coating layer on the ETFEL, such as silicon oxide, and
It is a thin film optical element with a large taper on the side surface on the TFEL side. When the glass coating layer is thickened, the ETF
Light emitted from the EL will travel through this coating layer. The light that has traveled through the coating layer is totally reflected at the boundary with this thin-film optical element, and the direction of the light beam is directed toward the surface of the document. Therefore, the angle at which the illumination light enters the document can be reduced. In addition to such elements, it is also possible to use a hologram lens or an element that causes reflection or scattering, as long as it has a similar function.

The embodiment shown in FIG. 4(b) has a similar purpose, and when bonding a substrate on which a charging conversion element is formed and a substrate on which an ETFEL is formed, the element surfaces of each substrate are at a certain angle. It is designed to have .

This type of shape can also be formed by fixing the substrates on which each element is formed with a jig etc. when bonding them, but it is possible to form them by fixing them with a jig etc. when bonding the substrates on which each element is formed. This can be achieved relatively easily by providing a slight taper angle.

The larger the angle between the element surfaces, the more the surface reflection on the document surface can be reduced and the amount of document light can be increased. However, the emission angle of the surface-reflected light also approaches perpendicular, making it difficult to separate it from the original light, and even if the angle is greater than 45 degrees, the S/N ratio will decrease. Furthermore, in order to increase this angle, it is necessary to perform taper dicing at a large angle, which also makes manufacturing difficult. For this reason, although it depends on the positional relationship between the photoelectric conversion element, the ETFEL, and the stepped portion, it is appropriate to set the angle to about 10 degrees to 30 degrees from the viewpoint of performance and ease of manufacture.

In actual manufacturing, the angle of the end face of the substrate varies due to problems with dicing accuracy, so a margin for this is taken.

However, the taper angle should be adjusted in the direction to obtain this condition.
FIG. 3 shows a die equipped with a light source of the image reading device of the present invention. is desirable. There is a cross-sectional view showing an ELFEL used in this invention.

[Effects of the Invention] As described above, by using the present invention, it is possible to perform reading without sacrificing low cost or compactness in an image reading device that performs reading by placing a photoelectric conversion element close to the document surface. We were able to achieve higher resolution, higher sensitivity, and improved S/N.

This makes it possible to support applications requiring high speed and high resolution, such as GIV facsimile and image filing systems, without increasing costs.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of an image reading device of the present invention. FIG. 2 is a diagram showing an example of a conventional image reading device.
FIGS. 3A and 3B are cross-sectional views showing other embodiments of the image reading device of the present invention. 101.201.401・Old・・・Insulating transparent substrate 102.202.402・・Old・Lower electrode layer 10
3.203.403.1 old...photoconductive layer 104.204
．． 404...Old...Transparent upper electrode layer 105.10B
, 107.206.406.407.408...
...passivation layer 111.211.411.
......Photoelectric conversion element 121.141...
...Edge-emitting type 811 electroluminescent element 122.422 ......Substrate 123.223
．． 423・Old・・・・Illumination light 231・・・・・・・
・Lighting window 141.241.441 ・Old・Dan・Manuscript surface 151.45
1...Step part 221...
Light source 452... Thin film optical element and above Applicant Seiko Epson Corporation Representative Patent Attorney Kizobe Suzuki (1 other person)

Claims (2)

[Claims] (1) The end face of the substrate on which the photoelectric conversion element was formed and the end face of the substrate on which the edge-emitting thin film electroluminescent element was formed were fixed so that the element surfaces were substantially parallel to each other or had an angle of 45 degrees or less. An image reading device characterized by having a structure. (2) A claim characterized in that the element surface of the substrate on which the edge-emitting thin film electroluminescent element is formed and the element surface of the substrate on which the photoelectric conversion element is formed are fixed so as to have a step difference. 1. The image reading device according to 1.