JPH06151799A - One-dimensional photosensor - Google Patents

Abstract

PURPOSE:To correct the quantity-of-light distribution of the illumination of a completely contact one-dimensional image sensor and to obtain the uniform photoelectric conversion output characteristics of the sensor. CONSTITUTION:An inclination is given to the aperture ratio of lighting windows 12, which are formed on a transparent glass substrate 11 and are used for taking-in light from an illumination, in the row direction of photoelectric conversion elements 3. In order to make an irregularity in the quantity of light of the illumination allow, the aperture area of the windows 12 is made small at a region having a large quantity of light and the aperture area is inversely made large at a region having a small quantity of light. When the quantity of light of the illumination and the aperture ratio of the windows 12 are assumed V and S, a one-dimensional photosensor is designed so as to hold the relation of VXS=K (a constant), whereby the quantity of light to reach a manuscript surface is held constant. Thereby, the output characteristic of the elements 3 can be made uniform and even though these is some irregularity in the quantity of light of the illumination, this irregularity can be corrected.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a one-dimensional optical sensor,
In particular, the present invention relates to a one-dimensional optical sensor suitable for a perfect contact image sensor that illuminates from the back surface of a transparent substrate.

[0002]

2. Description of the Related Art Recently, as a reading device such as a facsimile or an image scanner, a contact image sensor has been put into practical use in which the document width and the element array width of the optical sensor have a one-to-one correspondence. The contact image sensor does not require an optical path of a reduction imaging system and its fine adjustment, is advantageous in downsizing of the apparatus, and has an advantage of being economical.

FIGS. 3A and 3B show the basic structure of the contact image sensor. In the figure, it is a perfect contact type image sensor in which at least a daylighting window 2 having an opening portion and a photoelectric conversion element 3 are installed on a transparent glass substrate 1, and a thin protective glass plate 4 is adhered on this. The original 5 is brought into direct contact with and slides on the protective glass plate 4. Transparent glass substrate 1
The illumination light 6 of the LED 7 installed at the lower part of the light strikes the document 5 through the lighting window 2, and the reflected light reaches the photoelectric conversion element 3 to convert the image signal of the document 5 into an electric signal and read it. Since the original 5 is completely in close contact with the image sensor, the optical path length is short and the original 5 can be made compact. For example, if the photoelectric conversion elements 3 are arranged at a density of, for example, 8 / mm, the lighting windows 2 have a size of about 100 μm × 50 μm, and one or two photoelectric conversion elements 3 are formed adjacent to the photoelectric conversion elements 3. . In the case of an image sensor of A4 size, 1728 or 3456 lighting windows 2 are formed.

[0004]

In such a conventional one-dimensional photosensor, the light amount distribution of the light source of the illumination becomes the light amount distribution of the document surface as it is, and the uniformity of the light amount of the illumination becomes the sensitivity variation of the optical sensor. Is output. It is necessary to finally make the output variations uniform by applying electrical correction, and the correction range is also limited.

[0005] Normally, in order to reduce noise and size of lighting,
Although LED illumination is used, since the LED is basically mounted on a chip, the variation thereof is a large periodic value of ± 25% or more over the entire length. Further, if the pitch for arranging the LED chips is reduced to reduce this variation, the amount of heat generated increases, which affects the photoelectric conversion characteristics and reduces the S / N ratio, making it difficult to read a clear image. However, there is a big problem that the cost is increased because many LED chips are used.

[0006]

SUMMARY OF THE INVENTION A one-dimensional photosensor according to the present invention includes a transparent substrate which receives illumination light from one surface, and photoelectric conversions which are formed on multiple surfaces of the transparent substrate and are separately and independently installed on a straight line. In the one-dimensional photosensor, which comprises at least an element array and an opaque thin film layer which is arranged close to the photoelectric conversion element array and has a lighting window opened corresponding to each photoelectric conversion element, According to the light quantity (V) of the light, the aperture ratio (S) of the daylighting window corresponding to each of the photoelectric conversion elements is selected to satisfy the relationship of V × S = K (constant). I am trying.

[0007]

The present invention will be described below with reference to the drawings. 1A and 1B are a schematic plan view showing a basic structure of a one-dimensional photosensor according to the present invention and a light quantity distribution of LED illumination.

In the figure, the photoelectric conversion element 3 and the lighting window 12 are shown as an example on the upper surface of a transparent substrate 11 made of a transparent glass plate.
For example, in the case of an A4 size photosensor, 1728 pieces of each are arranged side by side. On the back surface of the transparent substrate, an LED array in which LED 7 chips are arranged in one row is installed, and the original surface on the upper surface of the transparent substrate 11 is illuminated through the lighting window 12. Since the same number of the lighting windows 12 are installed side by side with the photoelectric conversion elements 3, if the pitch is, for example, 8 lines / mm, they are installed at a pitch of 0.125 mm. In the LED7 array, the LED chips are usually arranged in a line and scattered, so that a periodic light amount unevenness occurs as shown in FIG. Although the variation varies depending on the pitch arranged for one LED7 array, a large light amount unevenness of ± 25% or more, for example, is inevitable. For this purpose, the lighting window 1
The size of 2 is set to be as large as possible in a place where the amount of light is small, and the opening of the lighting window 12 is made small in a place where the amount of light is large. That is, the aperture size of the daylighting window in the sub-scanning direction is planarly arranged with an inclination with respect to the axial direction to form an array, and variations in the light amount of the LED array are corrected. For example, the place with the smallest light intensity is 0.125 mm
If the size is × 0.1 mm, the area with the largest light amount has an opening size of 0.125 mm × 0.05 mm. LE
If the light quantity of the D array is V and the area of the lighting window is S,
The area of the lighting window may be determined so as to satisfy the relationship of V × S = K (constant). Since LED chips are mounted on the LED array in a scattered manner, light and dark are repeated periodically. If the size of the lighting window is determined according to the light-dark pattern, the light amount on the document surface will in principle have a constant value. A uniform image light output can be obtained without the need to electrically correct the output of the photoelectric conversion element 3. On the contrary, the number of LED chips can be reduced as much as possible if the above conditions are satisfied even if the LED array varies in light amount to some extent. Therefore, a configuration with a small number of LED chips is possible, and an inexpensive L
An ED array can be constructed. Further, the amount of heat generation is reduced, the temperature is increased, and the S / N is not deteriorated.

FIG. 2 is an out-of-plane schematic view showing a second embodiment of the present invention. In the figure, the outer diameters of the lighting windows 22 are all the same, and the grating 23 is installed inside the lighting windows. Gradually changing the density of the lattice 23 in the axial direction, L
It corresponds to the amount of ED illumination light. That is, when the amount of light of the LED array is large, the number of gratings in the lighting window is increased to increase the amount of light, and conversely, when the amount of light is small, the number of gratings is decreased or reduced to zero.

The one-dimensional photosensor having such a structure is
In addition to the same effects as those of the embodiment, since the light-dense dimension in the sub-scanning direction is the same for all the elements, the deterioration of the resolution in the sub-scanning direction does not occur. For example, in the case of A4 size over the entire length, the uniformity of sensitivity is ensured in all 1728 elements. In the above embodiment, the opening diameter of the daylighting window is variable, or the opening size is the same, and the density of the lattice pattern is variable, and the opening area is L.
It is changed according to the light amount of the ED array. But,
The present invention is not limited to this, and it is effective, for example, when the inside of the lighting window is on a mesh, or when two lighting window rows are combined, and each of them is combined, and if the variation of the LED light amount is corrected by the opening area of the lighting window, it is uniform. Thus, the illuminance on the original surface with a large amount of LED light can be obtained. Further, the present invention can be applied not only to LED lighting, but also to the case of correcting light at an end portion such as a cold cathode fluorescent tube.

[0011]

As described above, according to the present invention, since the unevenness of illumination is corrected and uniformed by changing the opening area of the lighting window installed on the transparent substrate, the S / N ratio is high. There is an effect that a low-priced one-dimensional optical sensor in which the correction circuit can be simplified can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing an embodiment of the present invention and a light quantity distribution of LED lighting.

FIG. 2 is a schematic plan view showing another embodiment of the present invention.

FIG. 3 is a schematic sectional view and a schematic plan view showing the basic structure of a conventional contact image sensor.

[Explanation of symbols]

 1 Transparent Glass Substrate 2, 12, 22 Daylighting Window 3 Photoelectric Conversion Element 4 Protective Glass Substrate 5 Original 6 Illumination Light 7 LED 11 Transparent Substrate 23 Lattice

Claims (1)

[Claims] 1. A transparent substrate that receives illumination light from one surface, a photoelectric conversion element array that is formed on the other surface of the transparent substrate and is linearly installed independently of each other, and is adjacent to the photoelectric conversion element array. In the one-dimensional photosensor at least composed of an opaque thin film layer having a lighting window opened corresponding to each photoelectric conversion element, corresponding to the light quantity (V) of the illumination light, A one-dimensional photosensor comprising the daylighting window in which the aperture ratio (S) of the daylighting window corresponding to each photoelectric conversion element is selected to satisfy the relationship of V × S = (constant).