JP2584773B2 - Image reading device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image reading apparatus that optically reads an image on a document used in a facsimile or the like.

(Prior art) The basic configuration of this type of device is to illuminate the original with a light source for illuminating the original, and then to reflect and diffuse the reflected and scattered light flux by an imaging system.
The image is read by forming an image on a long sensor array or the like formed of D or α-Si: H or the like. In recent years, there has been an attempt to read a sensor array by closely approaching the original surface without using an imaging system.

In order to read a document faithfully, the surface of the document is uniformly illuminated, an image is formed by an imaging system with no unevenness in the light amount, and there is no characteristic unevenness.
It is desirable to read by CCD or sensor array. If any of these has significant unevenness, a reading error occurs, for example, when a gray document is read uniformly over the entire surface, such a black streak or white streak appears remarkably.

Heretofore, attempts have been made to improve illumination unevenness and light amount unevenness of the image forming system by providing a slit having an appropriate opening shape in the optical path or shielding a part of the image forming system.

However, the non-uniformity of the characteristics of the sensor array has been solved by eliminating the non-uniformity itself, or by using only a sensor array having a small non-uniformity of the characteristics by sorting, by devising a sensor manufacturing process.

This has led to a prolonged development period of the device and an increase in cost.

(Problems to be solved by the invention) The present invention has been made to solve such problems.

(Means for Solving the Problems) The present invention relates to an image reading apparatus having a light source and a reading sensor array that receives light transmitted from the light source through a surface of a document to be read in close proximity to the surface of the document and receives the light. An optical member having a transmittance or aperture ratio distribution asymmetrically in the array direction corresponding to unevenness in the characteristics of the sensor array in an optical path from the light source to the reading sensor; The problem can be solved.

That is, the present invention aims to obtain an image reading apparatus which corrects the characteristic unevenness of the sensor by employing the above-described configuration and in which a reading error hardly occurs even when a sensor having a characteristic unevenness is remarkable.

The sensor may be a sensor array formed in an array, a sensor matrix formed in a matrix, or a single sensor area formed in a large area.

(Example) Next, the present invention will be described with reference to examples. FIG. 1 is a sectional view of an image reading apparatus according to an embodiment of the present invention.
In the figure, 1 is a light source, 2 is a filter, 3 is a structural member for supporting 5, 4 is a slit, 5 is a transparent substrate, 6 is a light shielding layer, 7 is a protective layer, 8 is an original, and 9 is a sensor light receiving portion. , 10 is 1
9 shows a luminous flux that exits from and reaches 9. The whole extends in the x-axis direction in the figure, and 9 is distributed in an array in the x-axis direction.

FIG. 2 is a plan view of the filter indicated by reference numeral 2 in FIG. In the figure, reference numeral 11 denotes a transparent substrate, and reference numeral 12 denotes an opaque (or low transmittance) portion formed of a metal film, a dye layer, or the like formed on the 11 by vapor deposition, patterning, printing, or the like.

The light beam 10 emitted from the light source 1 passes through the filter 2, the slit 4, the transparent substrate 5, and the protective layer 7, is reflected and diffused on the surface of the original 8, and reaches the sensor light receiving unit 9.

The filter 2 is formed by distributing the opaque portions 12 on the transparent substrate 11, and the density of the distribution of the 12 varies depending on the position in the x-axis direction. Since the size of each of the 12 dots is sufficiently small, unevenness corresponding to the size of the dots does not appear in the illuminance distribution of the exit surface (the surface in contact with the transparent substrate 5) of the slit 4 which is separated from 2 to some extent. However, an illuminance distribution in the x-axis direction corresponding to this change in density appears. The ratio of the illuminance on the exit surface of the slit 4 between the case where the filter 2 is not provided and the case where the filter 2 is provided is defined as the transmittance of the filter 2 at that position.

FIG. 3 shows a filter 2 according to the first embodiment of the present invention.
FIG. 6 is a diagram showing a transmittance distribution of the present invention. FIG. 4 is a diagram showing the sensitivity distribution of the sensor light receiving sections 9 arranged in an array in the x-axis direction in the embodiment of FIG. This distribution is for indoor conditions. As shown in FIG.
Is asymmetric with respect to the array direction,
Correspondingly, as shown in FIG. 3, the transmittance of the filter 2 is made asymmetric with respect to the array direction. FIG. 9 is a diagram showing a sensor output distribution when a gray document is read uniformly over the entire surface in a state where the filter according to the first embodiment is incorporated.

As described above, the dot density distribution of the filter 2 is designed so that the sensitivity distribution of the sensor is supplemented and the transmittance is high in a place where the sensitivity is low and the transmittance is low in a place where the sensitivity is high. When one image reading device is used, a uniform output can be obtained.

(Other Embodiment) FIG. 5 shows a filter 2 according to a second embodiment of the present invention.
FIG. 6 is a diagram showing a transmittance distribution of the present invention. Fig. 6 shows that the ambient temperature is Ta =
Sensor light receiving section 9 in Embodiment 2 when the temperature rises to 60 ° C.
FIG. 6 is a diagram showing a sensitivity distribution of the present invention. Example 2 at room temperature
Is shown in FIG. 4 as in the first embodiment. FIG. 10 is a diagram showing a sensor output distribution when an original is read uniformly over the entire surface with the filter incorporated in the second embodiment. In the figure, the solid line indicates a room temperature state, and the dotted line indicates a high temperature state.

In this embodiment, the dot density distribution of the filter 2 is designed so that a nearly uniform output can be obtained in any state, taking into account not only the room temperature state but also the sensitivity distribution in a high temperature state.

FIG. 7 shows a filter 2 according to a third embodiment of the present invention.
FIG. 6 is a diagram showing a transmittance distribution of the present invention. In this example,
To reduce the size of the device, the length of the light source is made as short as possible. If the length of the light source is not sufficiently long compared to the effective length of the device, a phenomenon in which the amount of light is insufficient at both ends of the effective length appears. 8th
The figure shows the illuminance distribution on the exit surface of the slit 4 when the filter 2 is not provided.

FIG. 11 is a diagram showing a sensor output distribution when an original is read uniformly over the entire surface with the filter incorporated in the third embodiment. In the figure, the solid line is at room temperature and the dotted line is at high temperature.

In the third embodiment, the distribution of the dot density of the filter 2 is designed so as to compensate for the decrease in the illuminance at both ends.

(Effects of the Invention) As described above, the use of the present invention makes it possible to obtain an image reading apparatus with few reading errors even if a reading sensor having large characteristic unevenness is used. Can do it.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of an image reading apparatus according to an embodiment of the present invention. FIG. 2 is a view showing a filter shown by 2 in FIG. FIG. 3 is a view showing a transmittance distribution of the filter in the first embodiment of the present invention. FIG. 4 is a diagram showing a sensitivity distribution at room temperature of the sensor array in the first and second embodiments of the present invention. FIG. 5 is a view showing a transmittance distribution of a filter according to a second embodiment of the present invention. FIG. 6 is a diagram showing a sensitivity distribution in a high temperature state of a sensor array according to the second embodiment of the present invention. FIG. 7 is a view showing a transmittance distribution of a filter according to a third embodiment of the present invention. FIG. 8 is a view showing an illuminance distribution on a slit exit surface when a filter is not provided in a third embodiment of the present invention. FIG. 9 is a diagram showing a sensor output distribution in the first embodiment of the present invention. FIG. 10 is a diagram showing a sensor output distribution in a second embodiment of the present invention. FIG. 11 is a diagram showing a sensor output distribution in a third embodiment of the present invention. 1 is a light source, 2 is a filter, 3 is a structural member for supporting 5, 4 is a slit, 5 is a transparent substrate, 6 is a light shielding layer, 7 is a protective layer, 8 is a document, 9 is a sensor light receiving section, and 10 is a sensor light receiving section. The luminous flux emitted from 1 to 9; 11 is a transparent substrate of 2; 12 is deposited on 11;
An opaque (or low-transmittance) portion made of a metal film, dye layer, or the like formed by patterning, printing, or the like.

Claims (1)

(57) [Claims] 1. An image reading apparatus comprising a light source and a reading sensor array for receiving light passing through the surface of a document to be read from the light source at a close distance to the surface of the document and receiving the light from the light source. And an optical member having an asymmetric distribution of transmittance or aperture ratio in the array direction corresponding to the unevenness of the characteristics of the sensor array.