JPH03183255A - Color reader - Google Patents

Abstract

PURPOSE:To prevent line spectrum components radiated from a fluorescent lamp light source from being made incident to a sensor by providing a filter, which has the incidence face arranged so as to cross the optical axis of an image forming optical system, and eliminates components having prescribed wavelength included to the incident light, between a fluorescent lamp light source and an original or between the original and a sensor. CONSTITUTION:An interference filter 220 consists of four reflection holograms 2211, 2212, 2213, and 2214, and respective reflection holograms 2211, 2212, 2213, and 2214 are diffraction gratings to selectively reflect components of narrow wavelength areas having prescribed wavelength lambda1, lambda2, lambda3, and lambda4 as centers. The interference filter 220 is arranged at 45 deg. to an optical axis 206, and the light reflected by the interference filter 220 is shielded by a blackboard 222 or the like to prevent this light from being made incident on a sensor 205. Thus, the measurement error of the intensity distribution due to the variance of the line spectrum is eliminated.

Description

[Detailed Description of the Invention] [Table of Contents] Overview Industrial Application Fields Conventional Technology Problems to be Solved by the Invention Means for Solving the Problems Action Examples ■, Correspondence between the Examples and FIG. 1 ■ , First Embodiment ■, Second Embodiment Effects of the invention [Summary] Regarding a color reading device that uses a fluorescent lamp as a light source, the bright line spectral components emitted from the fluorescent lamp light source are prevented from entering the sensor. With the aim of In a color reading device that reads color images by inserting a light source into the image sensor, a sensor is installed between the fluorescent lamp light source and the document, or between the document and the sensor so that the incident surface intersects the optical axis of the imaging optical system. is placed to remove components of a predetermined wavelength contained in the incident light,
comprising at least one filter that transmits other components;
The sensor is configured such that components passing through at least one filter reach the sensor.

[Industrial Field of Application] The present invention relates to a color reading device, and particularly to a color reading device using a fluorescent lamp as a light source.

Color reading devices are used as image input devices for facsimile machines and computers.

As a color reading device, for example, a charge coupled device (CCD) is used.
) and the like are known to measure and read a color image as the intensity distribution of each component of R (red), G (green), and B (blue).

Further, such color reading devices are required to read color images with high precision, and are also required to be smaller and lower in price.

[Conventional technology]

FIG. 7 shows the configuration of a conventional filter switching type color reading device. Further, FIG. 8 schematically shows the operation of a conventional filter switching type color reading device.

A document 611 is illuminated by an illumination device 612, and reflected light from a linear portion (hereinafter referred to as a reading line) 613 on the document 611 is transmitted to a sensor (for example, a CCD line image sensor) 61 by a lens 614.
It is imaged on 5.

This sensor 615 reads a color image at the reading line 613 by measuring the intensity distribution of incident light.

Here, in the color reading device shown in FIG.
filters 621r and 621g that transmit the green (G) component and the blue (B) component.

621b is selectively inserted.

These filters 621r, 621g, and 621b are linear motors 622r and 622g, respectively.

By driving these linear motors 622r, 622g, and 622b in the direction of arrow C perpendicular to the optical axis 616, the filter 621r
, 621g, and 621b are moved to positions where they block the optical path.

For example, the linear motor 62 corresponding to the filter 621r
When the filter 621r is inserted between the lens 614 and the sensor 615 as shown in FIG. 8(a), the sensor 615 receives only the R component of the reflected light from the reading line 613. is reached. This sensor 615
By measuring the intensity distribution of the R component of the reflected light, the R component of the image on the reading line 613 can be read.

Similarly, as shown in FIGS. 8(b) and (C), by driving the linear motors 622g and 622b, respectively, and inserting the filters 621g and 621b into the optical path, the image on the reading line 613 is A reading of 875 minutes is taken for the G component.

In this way, the color image of the linear portion of the document 611 corresponding to the reading line 613 is created by the filter 621r.
, 621g, and 621b, RGB
Each precept component is read in a time-divided manner.

Furthermore, by moving the original 611 by a predetermined length in the direction perpendicular to the reading line 613 (indicated by arrow A in FIG. 7) and repeating the above reading operation, the two-dimensional color image on the original 611 can be read. A read is made.

The three filters 621r and 621g described above.

621b, as shown in FIG. 9(b), filters 821r and 821b are placed on both sides with the filter 821b in the center.
One plate-shaped filter 820 formed with 21g adjacent to each other
A color reading device using
JP-A No. 62-210774 (disclosed in Color Reader J).

In the color reading device using the above-mentioned plate filter 820, as shown in FIG. By moving the filter 821r, 821g, or 821b in the vertical direction (indicated by arrow B in FIG. 9) within a plane, any one of the filters 821r, 821g, and 821b can be inserted into the optical path. In this way, by switching the filter inserted into the optical path, the sensor 81
5, the color image on the original document 811 is read by measuring the intensity distribution of each of the R, G, and B components.

FIG. 10 shows the configuration of a filter switching mechanism that moves the above-described plate filter 820.

The plate filter 820 is fixed to a substrate 823,
Further, one end of each of the four leaf springs 824 is fixed to the base plate 823, and the other end of each is fixed to the support base 831. By bending the four leaf springs 824, the base plate 823 is fixed to the support base 831. It is designed to swing using the fulcrum as a fulcrum. In addition, a pair of coils 8 are provided at both ends of the board 823.
26 is fixed.

A pair of magnets (not shown) are placed between each of the coils 826, and when a current is passed through the coils 826, the coils 826 use the force received from the magnetic field of the magnets to move the substrate 826 is moved in the vertical direction (indicated by arrows in FIG. 10).

In the above-mentioned filter switching type color reading device,
Since there is only one imaging optical system for reading images, RG
B: The size can be reduced compared to the case where a separate optical system is provided for each component, and the optical system can be easily adjusted because the reading position does not shift. Further, if the filter and the filter switching mechanism are made into a unit and made detachable, it can be added to a conventional black-and-white image reading device as an accessory, and it is also highly compatible with black-and-white image reading devices.

[Problem to be solved by the invention]

By the way, in the conventional method described above, as an illumination device for illuminating a linear part on a document, it is possible to uniformly illuminate such a linear area, and it is inexpensive and has a long life. Fluorescent lamps are widely used because they have the advantage of producing less heat and generating less heat.

Here, the light emitted by a fluorescent lamp includes not only a continuous component due to fluorescence, but also a bright line spectrum component unique to the element emitted when gas atoms sealed in the fluorescent lamp are excited by a discharge. is also included. For example, as shown in Figure 11, the spectral emission characteristics of a daylight fluorescent lamp include wavelengths of 405 nm (purple), 436 nm (blue-violet), and 54 nm (violet).
6nm (green).

The emission line spectrum of mercury such as 577-579rv (yellow) is seen.

The energy of such a bright line spectrum varies greatly depending on the ambient temperature and also varies depending on the lighting time of the fluorescent lamp. For this reason, the intensity of each RGB component of the reflected light from the document illuminated by the fluorescent lamp also fluctuates, resulting in the problem that color images cannot be read with high precision.

As a method for removing the influence of such emission line spectra and performing stable and highly accurate readings, a technique for performing measurements using the afterglow of a fluorescent light source (Japanese Patent Application Laid-Open No. 1983-1999) was proposed.
4270) has been proposed.

However, in this technique, it is necessary to repeat turning on and off the fluorescent light source at least once when reading an 1-line color image. For this reason, the time required for reading is longer, and the life of the fluorescent light source is shortened due to repeated blinking.Therefore, there is no method for reading color images with the fluorescent light source turned on. It is requested.

The present invention was created in view of these points, and it is an object of the present invention to provide a color reading device that prevents bright line spectral components emitted from a fluorescent lamp light source from entering a sensor.

[Means for Solving the Problems] FIG. 1 is a block diagram of the principle of a color reading device of the present invention.

In the figure, a document 101 is illuminated with a fluorescent light source 102,
The reflected light from the original 101 is imaged on a sensor 105 by an imaging optical system 104, and a plurality of color separation filters 106 each having a different color separation are selectively inserted into the optical path to read a color image. The color reading device is disposed either between the fluorescent lamp light source 102 and the original 101 or between the original and the sensor 105 so that the entrance plane intersects the optical axis of the imaging optical system 104, At least one filter 111 that removes a component of a predetermined wavelength contained in the incident light and transmits other components;
The configuration is such that the components that have passed through the two filters 111 reach the sensor 105.

[For production]

At least one filter 111 is connected to the fluorescent light source 102.
and the original 101 or between the original and the sensor 105 so that the incident surface intersects the optical axis of the imaging optical system 104.

For example, if these filters 111 are placed between the document 101 and the sensor 105, these filters 111
11, a component of a predetermined wavelength included in the reflected light from the original 101 is removed, other components are transmitted, and the sensor 1
Reach 05.

In addition, when these filters 111 are placed between the fluorescent lamp light source 102 and the document 101, these filters 111
The original 101 is illuminated by the component light transmitted through the original 11, and the light reflected by the original 101 is sent to the sensor 105.
reach.

For example, if the above-mentioned at least one filter 111 removes the bright line spectrum component contained in the light emitted from the fluorescent light source 102, it is possible to remove the bright line spectrum component contained in the light emitted from the fluorescent lamp light source 102. Color images can be read using the components.

Further, these filters 111 may be realized by a holographic diffraction grating formed by a reflection hologram.

In the present invention, since a predetermined wavelength component (e.g., a bright line spectrum component) is removed by the at least one filter txt described above, even when the fluorescent lamp light source 102 is continuously turned on, , the above-mentioned predetermined component never reaches the sensor 105.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 shows the configuration of a color reading device in one embodiment of the present invention.

1. Correspondence between the embodiment and FIG. 1 Here, the correspondence between the embodiment of the present invention and FIG. 1 will be shown.

The original 101 corresponds to the original 201.

The fluorescent lamp light source 102 corresponds to a fluorescent lamp used in the lighting device 202.

The imaging optical system 104 corresponds to the lens 204.

Sensor 105 corresponds to sensor 205.

The color separation filter 106 corresponds to the filters 211r, 211g, and 211b forming the plate-like filter 210.

Filter 111 corresponds to interference filter 220.

Examples of the present invention will be described below assuming that the correspondence relationship as described above exists.

In FIG. 2, a document 201 is illuminated by an illumination device N2O2 whose light source is a fluorescent lamp.
Reading reline corresponding to the linear area above (not shown)
A component of the reflected light that has passed through an interference filter 220 (described later) is imaged by a lens 204 onto a sensor (for example, a CCD line image sensor) 205.

Moreover, between the original 201 and the sensor 205 in FIG.
For example, a filter switching mechanism (not shown) whose detailed configuration is shown in FIG. 1O is arranged. This filter switching mechanism includes filters 211r and 211g that pass through RGB components, respectively.

A plate-shaped filter 210 consisting of 211b is fixed, and the plate-shaped filter 210 is rotated in a direction perpendicular to the optical axis 206 (
(indicated by arrow E in the figure). As a result, the filters 211r, 211g, 211
b is selectively inserted into the optical path.

For example, when the filter 211r is inserted into the optical path by the filter switching mechanism, only R of the reflected light from the reading line 203 reaches the sensor 205. Similarly, filter 211g.

211b, the G component and B component of the reflected light each reach the sensor 205.

In this way, the filters 211r, 211g, and 211b are sequentially switched so that the document 20 corresponding to the reading line is
The image of the linear area on 1 is time-divisionally measured as the intensity distribution of each RGB component.

Further, the above-mentioned plate-shaped filter 210 may be arranged between the lens 204 and the sensor 205, and the plate-shaped filter 210 and the filter switching mechanism are configured such that each of the three filters is driven by a linear motor. (See FIG. 7).

(ii) Structure of Interference Filter The interference filter 220 includes, for example, four reflective holograms 221. ．． 2212, 221. ．． 221°, and these reflection holograms 221, . 221□
, 221. ．． 221. each has a predetermined wavelength λ2 .
λ2. λ1. It is a diffraction grating that selectively reflects components in a narrow wavelength range centered on λ4.

Further, this interference filter 220 is arranged at an angle of, for example, 45 degrees with respect to the optical axis 206, and is blocked by a blackboard 222 or the like so that the light reflected by this interference filter 220 does not enter the sensor 205. There is.

FIG. 3 shows an explanatory diagram of a reflection hologram.

For example, when white light is incident on the reflection hologram 2211 at a predetermined angle, only components in a narrow band centered around the wavelength λ1 are reflected, as shown in FIG. 3 as the spectral characteristics of the reflected light. In this case, as shown in FIG. 3, the component obtained by removing the narrow band component centered on the wavelength λ1 mentioned above from the spectrum of the incident white light (see FIG. 3) is transmitted through the reflection hologram 2211. do.

Here, the center wavelength and bandwidth of the component reflected by the reflection hologram serving as the diffraction grating are determined by the diffraction grating pattern burned into the reflection hologram, but this diffraction grating pattern is Therefore, it is possible to design freely.

It is also possible to design the above-mentioned diffraction grating pattern so that the above-mentioned spectral characteristics of reflected light and transmitted light can be obtained for white light incident at different angles at each position of the reflection hologram. be.

Therefore, the wavelength λ1. λ2. λ5. λ4 is 405 each
nm, 436 nm, 546 nm, and 578 r+m, and design a diffraction grating pattern taking into consideration the inclination of the incident surface with respect to the optical axis (for example, 45 degrees) and the change in the incident angle depending on the position due to the incidence of convergent light (or diffused light). Bye.

The diffraction grating pattern created in this way is printed onto a glass substrate or the like, and the reflection holograms 221, . 22
1□, 2213, 221. The interference filter 220 may be formed by laminating them.

FIG. 4 shows the spectral characteristics of transmitted light and reflected light when light including components of the bright line spectrum is incident on this interference filter 220.

In this way, the four bright line spectrum components in the incident light are reflected in the reflection hologram 2 constituting the interference filter 220.
21. ．． 221□, 221. ．． 2214 and only the fluorescence component is transmitted through this interference filter 220.

Here, since the illumination device 202 uses a fluorescent lamp as a light source, the reflected light from the original 201 also contains a component corresponding to the bright line spectrum component shown in FIG. , changes depending on the energy of the components of the emission line spectrum, the ambient temperature, the lighting time of the fluorescent lamp, etc.

However, as described above, the reflection hologram 221 . ．． Since it is reflected by each of 22L, 2213° and 2214, it never reaches the sensor 205.

Therefore, only the light that has passed through the interference filter 220 (see FIG. 4) reaches the sensor 205, and the intensity distribution is measured as described above, eliminating measurement errors in the intensity distribution due to fluctuations in the bright line spectrum. can do.

The fluorescence component that passes through this interference filter 220 is
It is stable over time and has little temperature dependence. Therefore, by performing measurements using only such fluorescent components, errors in measurement results due to changes in the fluorescent lamp over time or changes due to ambient temperature can be reduced, and color images can be read with high precision.

Further, since the bright line spectrum is removed by the interference filter 220 inserted into the optical path, there is no need to blink the fluorescent lamp. Therefore, measurements can be made while the fluorescent lamp is continuously turned on, and the time required to read an image can be reduced compared to the case where the measurement is performed by repeatedly flashing the fluorescent lamp. Furthermore, the life of the fluorescent lamp will not be reduced.

Although FIG. 2 shows the case where the interference filter 220 is placed between the original 201 and the lens 204,
This interference filter 220 may be placed between the lens 204 and the sensor 205.

Normally, the lighting device 202 shown in Fig. 2 is a unit that integrates a power supply circuit for the fluorescent lamps, a heat insulating device that keeps the temperature of the fluorescent lamps constant, etc. light 4
01 is housed in a housing 410 as shown in FIG.

This housing 410 has a window 41 on the side facing the original 201.
1 is provided, and the emitted light from the fluorescent lamp 401 illuminates the document 201 through this window 411.

Therefore, the interference filter 220 shown in FIG.
1 and the sensor 205, instead of inserting it into the optical path between
When the interference filter 420 created as described above is attached to the window 411 described above, components of the light emitted from the fluorescent lamp 401 excluding the bright line spectrum (see FIG. 4) reach the original 201.

As a result, the original 201 is illuminated with light having a continuous spectrum as shown in FIG. This makes it possible to read color images with high precision.

Furthermore, since measurements can be made while the fluorescent lamp is continuously lit, the time required to read images can be shortened. Furthermore, the life of the fluorescent lamp will not be reduced.

Furthermore, the window 411 of the housing 410 that constitutes the lighting device 202
Since the interference filter 420 is attached to the color reading device, it is possible to meet the demand for downsizing the color reading device and making maintenance easier by unitizing each part.

Note that the position where this interference filter 420 is placed is not limited to the window 411 of the housing 410, but is also placed between the fluorescent lamp 401 and the document 2.
01, for example, Fig. 6(a),
As shown in (b), a coating technique may be applied to a part or all of the tube surface of a fluorescent lamp.

FIG. 6(a) shows a case where an interference filter is formed by coating on a portion of the tube surface of a fluorescent lamp that contributes to illumination of the document 201. In this case, the manuscript 201
The light that reaches , does not include the above-mentioned bright line spectrum.

Moreover, FIG. 6(b) shows a case where an interference filter is created all around the tube surface of a fluorescent lamp. In this case, all the light emitted from the fluorescent lamp is filtered by this interference filter, so that the spectral characteristics of the light emitted from the fluorescent lamp are as shown in FIG.

〔Effect of the invention〕

As described above, according to the present invention, components of a predetermined wavelength (for example, components of the IIm spectrum) are removed by at least one filter, so even when the fluorescent light source is continuously turned on, Since the above-mentioned predetermined components never reach the sensor, color images can be read at high speed and with high precision, which is extremely useful in practice.

[Brief explanation of drawings]

FIG. 1 is a principle block diagram of a color reading device according to the present invention, FIG. 2 is a configuration diagram of a color reading device according to a first embodiment of the present invention, FIG. 3 is an explanatory diagram of a reflection hologram according to the embodiment, and FIG.
The figure is an explanatory diagram of the interference filter according to the embodiment, and FIG.
FIG. 6 is a diagram showing a modification of the illumination device according to the second embodiment, FIG. 7 is a diagram showing the configuration of a conventional color reading device, and FIG. 8 is a diagram of a conventional color reading device. FIG. 9 is a block diagram of another conventional color reading device, FIG. 1O is a block diagram of a filter switching mechanism, and FIG. 11 is a diagram showing the spectral characteristics of a fluorescent lamp. In the figure, 101 is a document, 102 is a fluorescent light source, 104 is an imaging optical system, 105 is a sensor, 106 is a color separation filter, 111 is a filter, 201, 611, 811 is a document, 202, 612, 812 is an illumination device , 204.614,814 is a lens, 205.615,815 is a sensor, 206.616,816 is an optical axis, 210.820 is a plate filter, 211.621,821 is a filter, 220.420 is an interference filter, 221 401 is a reflection hologram, 401 is a fluorescent lamp, 410 is a housing, 411 is a window, 613 is a reading line, 622 is a linear motor, 823 is a substrate, 824 is a leaf spring, 826 is a coil, and 31 is a support stand. A block diagram of the principles of the present invention.FIG. 1. Structure of a color reading device according to an embodiment.FIG. Fig. 9 shows a modification of the conventional color reading device. Fig. 9 shows the operation of the conventional color reading device. Fig. 9 shows the structure of the filter switching mechanism.

Claims (1)

[Claims] (1) A document (101) is illuminated with a fluorescent light source (102), and the reflected light from the document (101) is reflected by the imaging optical system (102).
4) in a color reading device which reads a color image by forming an image on a sensor (105) and by selectively interposing a plurality of color separation filters (106) each having a different color separation in the optical path; Either between the lamp light source (102) and the original (101) or between the original and the sensor (105), such that the incident surface intersects the optical axis of the imaging optical system (104). At least one filter (111) is arranged and removes a component of a predetermined wavelength contained in the incident light and transmits other components, and the component transmitted through the at least one filter (111) is transmitted to the sensor (105). A color reading device characterized in that it is configured to reach.