JPH0258961A - Color reader - Google Patents

Abstract

PURPOSE:To read a picture with high accuracy by providing a slit to pass light for a luminous flux width at least either between a lens and a filter or between the filter and a line image sensor. CONSTITUTION:The slit to pass light for the luminous flux width is provided at least either between a lens 2 and filters 4a-4c or between the filters 4a-4c and a line image sensor 3. For example, a slit plate 23 equipped with a slit 21 is provided between the lens 2 and the filters 4a-4c, a slit plate 24 equipped with a slit 22 is provided between the filters 4a-4c and the line image sensor 3, and while the slit 22 has a linear shape, the slit 21 is made into a shape which can make passing light quantity at the edge part of a reading line larger than that at the center part of the reading line. Consequently, the multiple reflection of light, the scattering of light at a filter edge, etc., can be decreased, and the deterioration of a reading picture can be prevented. Thus, high-accurate reading can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color reading device that reads color images in a time-division manner by switching filters.

Color reading devices are used as image input devices for facsimiles and computers. Among these color reading devices, devices that read three colors, R (red), G (green), and B (blue) using a CCD image sensor or the like are known. This color reading device is desired to be further downsized, lowered in price, and improved in image quality.

[Conventional technology]

The basic parts of the conventional filter switching type color reading device to which the present invention is applied will be explained below using FIGS. 4 and 10.

FIG. 4 is a perspective view showing a conventional filter switching mechanism, and in the figure, reference numeral 1 indicates a reading line on the original 100. The reading line 1 is illuminated by illumination means (not shown), and an image on this line is read as follows.

Reflected light (reading light) from the reading line 1 is imaged by a lens 2 onto a line image sensor 3 such as a CCD line image sensor. In order to perform color reading, R2O and 83 filters 4a are installed between the lens 2 and the sensor 3.
, 4b and 4c are provided.

Filters 4a, 4b, 4c are linear motors 5a.

5b and 5c, respectively, and can be moved to a position that blocks the reading light from the reading line 1 to the sensor 3. When reading the R component of the color image on the reading line 1, as shown in FIG. 5(a), the R filter 4a of the three filters is placed in the optical path by driving the linear motor 5a. . Other two filters 4b
, 4c are held at retracted positions where they do not block the optical path. As a result, only the red light among the reflected light from the reading line 1 reaches the sensor 3, and the R component of the image is read. Image G
, B components are read by inserting filters 4b and 4c into the optical path, respectively, as shown in FIGS. The next line is read by feeding it a predetermined amount in the direction of the signal arrow (sub-scanning direction).

This color reading device combines a small, lightweight filter and a high-speed linear motor to achieve a single sensor.
High-speed color reading can be achieved by switching filters in approximately the same time as the line reading time (1 to 10 m5).

A conventional color reading device having such a configuration and operation has the following advantages.

(1) Compared to the conventional three-optical system system, there is only one optical system, and the device can be made smaller.

(2) By removing all three filters from the reading optical path, black and white reading is possible, and one device can be used as a color and black and white reading device. Furthermore, the filter switching mechanism can be made into a unit and incorporated into the optical system of a conventional black-and-white reader, so that color reading can be made an option for the black-and-white reader. That is, it has good compatibility with conventional black and white reading.

(3) Since there is only one optical system, there is no deviation in the reading position of each color of R, G, and B, and adjustment of the optical system becomes easy.

In this description, the filter is inserted between the lens 2 and the sensor 3, but the same effect can be obtained even if the filter is inserted between the document 100 and the lens 2.

Also, in the above explanation, each filter was made into a separate board, but
Each filter 4a as shown in FIG.

The same applies to the case where 4b and 4c are made into one plate and are made to reciprocate up and down on the optical path. FIG. 6 (al is a side view showing the filter in the optical path, FIG. 6(b) is a perspective view of the filter. FIG. 7 is a perspective view showing how to support the filter in FIG. 6, and the filter 4a, 4b and 4c are fixed to a common substrate 6 by adhesive or the like.The base vi6 is fixed to the tip end portion -7b of the leaf spring 7 with a screw 8.

FIG. 8 shows the switching mechanism of the filter shown in FIG. 6.

This filter switching mechanism has already been proposed by the applicant (Japanese Patent Application No. 136901/1983; filed on June 1, 1986).
2), the base 7a of the leaf spring 7 is attached to the lens 2.
It is fixed to a support member 9 that holds the.

The board 6 supported by the leaf spring 7 in this manner is a moving coil type linear motor 1 comprising a coil 10 fixed to the board 6 and a magnet 11 fixedly installed opposite to the coil 10.
The coil IO is reciprocated up and down by the coil IO, thereby switching the filter. During this drive, a sinusoidal current, for example, is supplied to the coil IO. Filters 4a, 4b, 4c
The material to be used is one with excellent heat resistance, moisture resistance, etc., such as colored glass. 13 is a reading light source (fluorescent lamp).

[Problem to be solved by the invention]

In the case of such a conventional structure, the lens 2 and the filter 4a,
4b, 4c, and filter 4a.

Scattering and multiple reflections of light occur between 4b, 4c and the line image sensor 3. Furthermore, by moving the filter, scattered light from the edges of the filter plate may enter the sensor. These lights eventually become a source of false signals, making it impossible to accurately read the document and deteriorating the read image.

Furthermore, in the conventional structure, a phenomenon called shading occurs for the following reasons.

(In a fluorescent lamp with 11 light sources, the brightness is lower at the ends than at the center in the tube length direction.

(2) The amount of light passing through a lens decreases at the periphery compared to the center of the lens according to the cosine fourth power law.

For the above reasons, for example, when reading a completely white document, the sensor output is lower at the edges along the reading line than at the center, as shown in FIG.

Normally, the output at the edges is 40 to 50% lower than that at the center, and if this continues, even if a document with the same density is read in the reading line direction, the output will change, making it impossible to read with high precision. Therefore, shading correction is performed for boat fishing.

This is done, for example, as follows. That is, the reference white is read and its output is stored. Then, the output when reading the original is corrected for each reading line position using the stored output as a reference.

However, this requires a correction circuit, which increases costs. Furthermore, if the difference in output between the center and the ends is large, there is a problem that the circuit scale becomes correspondingly large.

An object of the present invention is to provide a low-cost color reading device that can read images with high precision.

[Means to solve the problem]

In order to achieve the above object, the present invention guides the reflected light of the light that irradiates the color image on the document surface to the line image sensor through a lens and three color filters, and drives the line image sensor and controls the filter. In a filter switching type color reading device that reads color images in a time-division manner by synchronizing switching, a luminous flux width is provided between the lens and the filter, and between the filter and the line image sensor. The light passing width of one of the slits is set to be wider at the end than at the center, even if there is no compromise.

[Effect]

By inserting the filter as described above, light scattering and multiple reflections, which have been problems in the past, are reduced, so deterioration of the read image can be prevented and highly accurate reading can be achieved.

In addition, the shape of the slit is set so that the amount of light passing through the end of the reading line is greater than the center of the reading line, which eliminates the need for a circuit that performs shading correction, or reduces the burden on the circuit. It can be simplified and costs can be reduced.

〔Example〕

The present invention will now be described in detail with reference to FIGS. 1-3.

FIG. 1 is a perspective view showing the main structure of a color reading device according to the present invention, and in the figure, the same reference numerals are given to members having the same structure as those of the conventional one.

In the present invention, lens 2 and filter 4 a+ 4 b+
A slit is provided between the filters 40 and at least one of the filters 4a, 4b, 4c and the line image sensor 3 to allow light corresponding to the width of the luminous flux to pass through.
In this example, the slit plate 23 provided with the slits 21 serves as the lens 2 and the filter 4a.

4b and 4c, and a slit plate 24 having slits 22 is provided between the filters 4a, 4b, 4c and the line image sensor 3. The slit 22 is linear, but the slit 21 is
It has the shape shown in the figure, and the amount of light passing through the end portion of the reading line is greater than the central portion.

Providing such a slit reduces multiple reflections of light, scattering at filter edges, etc., thereby preventing deterioration of the read image and achieving highly accurate reading. Figure 3 is an explanatory diagram of the effect of the slit.
3(b) shows the state of multiple reflection, scattering, etc. of light in the case of the conventional structure (without slit), and FIG. 3(b) shows the state in the case of the present invention. 3a is a cover glass of the line image sensor 3. The above-mentioned effect is clear from this figure.

In this case, although a similar effect can be obtained by simply providing the slit 21, an even greater effect can be obtained by also providing the slit 22.

Further, since the slit 21 has the above-described shape, and the amount of light passing through the end portion of the reading line is greater than the central portion, shading can be prevented. In the case of a reading device that requires only a certain level of quality of read images at a low cost, this alone is sufficient for shading correction. Follower/
Therefore, a correction circuit is not necessary, and cost reduction can be realized. This is greater than the cost amplifier by adding a slit. In addition, in the case of a reading device aiming at high-precision reading, correction by a circuit is required in addition to the shading correction by the slit 21, but in that case as well, the amount of correction by the circuit is reduced by providing the slit 21. Reduce your burden. For example, the capacity of the memory that stores the read output of the reference white can be reduced if the fluctuation range of the reference signal is small. Therefore, cost reduction can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, the insertion of the filter reduces the scattering and multiple reflections of light between the lens and the filter or between the filter and the line image sensor, thereby preventing deterioration of the read image and increasing the Accurate reading is achieved. Furthermore, it is possible to simplify the circuit by omitting the circuit that performs shading correction or by reducing the load on the circuit, and it is possible to realize cost reduction.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the main structure of a color reading device according to an embodiment of the present invention, FIG. 2 is a perspective view showing the shape of a slit, and FIG.
Figure 4 is a perspective view showing the main parts of a conventional filter switching type color reading device, and Figures 5 (a), (b), and (C) are 4 is an explanatory diagram of the color reading operation of the device; FIGS. 6(a) and 6(b) are explanatory diagrams of the structure of other conventional filters; FIG. 7 is a perspective view showing how to support the filter of FIG. 6; The figure is a perspective view showing the filter switching mechanism of Fig. 6, and Fig. 9 is a graph showing the sensor output distribution in the case of the conventional structure. In the figure, 2 is a lens, 3 is a line image sensor, 4a, 4b, 4c is a filter, 21.22 is a slit, and 23.24 is a slit plate.

Claims (1)

[Claims] A lens (
2) and three color filters (4a, 4b, 4c) to the line image sensor (3), and drive the line image sensor (3) and the filters (4a, 4b, 4c).
) in a filter switching type color reading device that reads color images in a time-division manner by synchronizing the switching of the lens (2) and the filter (4a, 4b, 4c).
A slit (21) is provided between the filters (4a, 4b, 4c) and the line image sensor (3), and the slit (21) allows light of a width equal to the luminous flux to pass therethrough. A color reading device characterized in that the light passing width of one of the slits (21) is set to be wider at the ends than at the center.