JPS6243964A - Original reader - Google Patents

Abstract

PURPOSE:To obtain a stable color separation signal by providing an eliminating means for cutting nearly off infrared light of 690nm-1,100nm generated from a light source or light including the infrared ray. CONSTITUTION:When a fluorescent lamp 1 is lighted, the light is transmitted through a color filter 5 as an eliminating means cutting off near infrared-rays of long wave range from 690nm-1,100nm, the luminous quantity of the light 1 is detected by a detector 6, a signal is inputted to a lighting circuit 2 to stabilize the luminous quantity of the fluorescent lamp 1 at the visual region. The spectrum distribution transmitted through the color filter 7 of the stabilized fluorescent lamp 1 consists of the visual light range only, the light is irradiated on an original 9 and the reflected light is formed on a CCD line sensor 12 with the color separation filter 11 by a distribution refractive rod lens array 10. Thus, a stable color separation signal is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to (color) document reading and placement, and particularly to stabilization against fluctuations in the spectral distribution of a light source.

[Technical disadvantages of inventions and their problems]

In conventional (color) document reading devices, a light source with good color rendering properties, such as a halogen lamp, is used in order to obtain stable color separation characteristics.

In the case of such a light source, if the applied voltage is kept constant, the spectral distribution will be constant, and it is relatively easy to handle, but it is inefficient and generates a large amount of heat, so it cannot be used in small devices. Ta.

The amount of light can also be adjusted by changing the voltage applied to the light source.
]-, the spectral distribution also changes, and the light II
There was also a drawback that it was difficult to adjust. Therefore, fluorescent lamps are being considered in place of these light sources.

When using a fluorescent lamp as a light source, the luminous efficiency is also good;
Furthermore, by appropriately combining multiple types of phosphors, a fairly free spectral distribution can be obtained. Therefore, by using such a fluorescent lamp, it is relatively easy to improve color separation characteristics in combination with a reading sensor.

However, fluorescent lamps have the characteristic that when the tube is cold immediately after lighting, the amount of visible light emitted is lower than when the tube is rated (tube wall temperature around 45°C), and the amount of near-infrared light is increased. are doing.

In general, the transmittance of color separation filters and the reading sensor +
The sensitivity of the J- (for example, COD image sensor) extends to the near-infrared region, so if the spectral distribution fluctuates as described above, the color separation signal will be different from the color separation signal at the rated time. This has the disadvantage that stable color separation characteristics cannot be obtained.

Note that the above-mentioned problem is not only true when obtaining a color signal, but also applies when obtaining a monochrome binary signal.

For example, i! [! As mentioned above, when a document contains red information such as a seal, and a lot of near-infrared light is emitted, binarization at a certain level will correct the conversion to 2III. There was a drawback that it was not carried out. On the other hand, according to the above-mentioned patent publication, the above-mentioned drawback is solved by varying the binarization level according to the amount of near-infrared light. However, when obtaining a multi-valued color signal, it is impossible to eliminate the above-mentioned disadvantages using the method described in the above-mentioned patent publication.

Further, in the above-mentioned patent publication, a method of introducing an infrared cut filter is discussed in order to eliminate the above-mentioned disadvantages. According to this report, when an infrared cut filter is used, not only the infrared wavelength region but also part of the red wavelength region is often cut off, which not only makes it impossible to read red information correctly, but also reduces the amount of light. This resulted in a reduction in resolution and aggravated temporal fluctuations in the fluorescent lamp light distribution, making it unreasonable for practical use. As described above, if an appropriate infrared cut filter is not used and the light source is not stabilized properly, the disadvantages pointed out in the patent publication will occur. Especially color belief @
When reading, an extremely unnatural color output signal is produced in which only a specific color is emphasized.

In addition, in order to eliminate these drawbacks, we set the power source to 0NLk, turn on the light source for a certain period of time, place a heater around the fluorescent lamp, and set the tube W! Devices that control concentration are also being considered. However, when the light source is turned on for a certain period of time, the time for the light source to stabilize is not constant depending on the temperature of Iw, and there is a problem in achieving stabilization. Furthermore, when controlling the diaphragm, the concentration of the emitting part is not necessarily controlled, which has the disadvantage that the luminescence distribution is difficult to maintain constant. Note that a light source whose emission spectral distribution fluctuates is a phenomenon observed not only in fluorescent lamps but also in many light sources.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and eliminates the influence of infrared light output from a light source, and eliminates the possibility that the amount of light emitted by the light source fluctuates due to changes in environmental humidity, etc., or due to deterioration of the light source. It is an object of the present invention to provide a document reading device that can obtain stable color separation signals even if the amount of light varies.

(Invention 11) In order to achieve the above object, the present invention uses infrared light of approximately 6900 to 1100 ni generated from a light source, or
The reading sensor reads the light from which the infrared light has been removed by the removal means, and prioritizes the light source from which the infrared light has been removed. Light - - 〇 - Light detected by a detector or insensitive to infrared light -
A detector is used to detect the amount of light from the light source, and the amount of light emitted from the light source is controlled according to the detected amount of light.

(Embodiment of the Invention) The present invention will be described below with reference to an embodiment shown in FIGS. 1 to 10. In the figure, reference numeral 1 denotes a fluorescent lamp as a light source, and this fluorescent lamp I is lit by a lighting circuit 2 with a dimming function. The lighting starts using the operation button 4 connected to CP IJ 3.
A lighting start signal is generated, and the lighting circuit 2 is controlled by the CPU 3.

Although not shown, it is assumed that only the heater of the fluorescent lamp 1 is energized when the power of the document reading apparatus is turned on. Now, when the above fluorescent lamp 1 is turned on, 690
The light passes through a color filter 5, which serves as a removal means for cutting near-infrared light in the long wavelength range from nm to 110011 nm, and detects the amount of light from the fluorescent lamp 1 using a silicon photodiode as a detector, and adjusts this signal. It is input to the input terminal of the feedback loop of the lighting circuit 2 with optical function.

Figure 2a shows the spectral distribution immediately after the fluorescent lamp 10 is turned on without the feedback loop system, and b
This diagram shows the spectral distribution after lighting up until the end of the turn.

The light from the fluorescent lamp 1 is filtered through a color filter 5 (for example, made by C-SOO Hoya Glass) having the spectral transmittance shown in FIG. When detected with the exception of , the temporal change in the amount of light increases as shown in FIG. In other words, variations occur in the visible region. Therefore, as shown in FIG. 4, light from which infrared light has been cut is detected, and its signal is input to the lighting circuit 2 to stabilize the emitted light i of the fluorescent lamp 1 in the visible region.

That is, immediately after the fluorescent lamp 1 is turned on, much energy is spent emitting infrared light, as shown in FIG. 2a, and the visible light emitting layer is small. If this infrared light is detected using the light amount cut by the color filter 5, the amount will be smaller than when it is stable, as shown in FIG.

Therefore, in the lighting circuit 2, this silicon photodiode 6
A large amount of 1 energy is supplied from the lighting circuit 2 to the fluorescent lamp 1 so that the signal becomes constant. A large amount of energy is then supplied to the fluorescent lamp 1 until the amount of light becomes equal to the stable visible light amount. The emission spectrum of the fluorescent lamp 1 at this time is as shown in FIG. 5, and the emission spectrum in the visible light region is almost the same as the spectrum in a stable state, as shown in FIG. A filter 7 (as a removing means) having a transmittance shown in FIG.
It has the same characteristics as the color filter 5. ) There is no temporal variation in the amount of light transmitted through the filter, as shown in FIG.

At this time, the spectral distribution of the light transmitted through the color filter 7 is only in the visible light range, as shown in FIG. 7, and there is no variation in the spectral distribution. Next, this light is transmitted to the last 8
The reflected light is focused on a COD licensor 12 equipped with a color separation filter 11 by a distributed line bending rod lens array 10 . This imaged light is photoelectrically converted by the COD licensor 12, amplified by the amplifier 13, input to the A/D converter 14, and converted into a digital signal. In this way, the document is illuminated with stabilized light, so that stable color separation signals can be obtained.

As described above, the present invention is based on the fact that the fluctuation factor of the spectral distribution of a fluorescent lamp light source is caused by the emission spectrum of the rare gas sealed in the fluorescent lamp for starting discharge. That is, in a normal fluorescent lamp, argon gas is sealed in order to facilitate the start of discharge, and immediately after lighting, a large amount of the emission spectrum of argon gas (the wavelength from 690 ns to 950 ns is the most common) is emitted.

After lighting, the tube wall temperature rises due to discharge. As the mercury vapor pressure rises, the emission spectrum of mercury and the emission spectrum of the phosphor excited thereby increase, and after stabilization, the emission spectrum of argon almost disappears. In other words, the emission spectrum of a fluorescent lamp has a spectral distribution that shifts from the emission spectrum of a rare gas that emits light in the near infrared to the emission spectrum of mercury and phosphor that emits visible light.

On the other hand, many image sensors generally have almost no sensitivity in a long wavelength band of 1100 rv or more.

Therefore, in order to eliminate the influence of near-infrared light, which is the emission spectrum of rare gases, a filter is used on the illumination system side or the light receiving system side to cut off infrared light including light with wavelengths from 6900 to 1100 rv. Then, the light received by the image sensor is only the light of the spectrum of mercury and the spectrum of the phosphor excited by it, and the relative intensity of the spectral distribution fluctuates from just after turning on until it stabilizes. do not.

Next, when the discharge energy is constant, the discharge energy is used to emit light from the rare gas immediately after lighting, and the amount of visible light emitted is small. Therefore, the amount of light transmitted through the filter 5 that cuts the near-infrared light is detected, and information on this amount of light is fed back to the lighting circuit 2 of the fluorescent lamp 1, so that the amount of light emitted from the fluorescent lamp 1 is kept constant. For example, the spectral distribution in the visible light range, including the amount of light, can be made constant. By doing so, it becomes possible to read color information correctly, and there is no decrease in the amount of light, there is no temporal variation, and it is possible to obtain stable color separation characteristics.

In the above embodiment, an example was explained in which the infrared cut filter 7 was inserted on the illumination system side, but the same effect can be obtained even if a color filter 150 is inserted on the light receiving side as shown in FIG. Further, this color filter 150 may also be used as a cover glass of the package of the line sensor 12 equipped with the color separation filter 11.

Further, as shown in FIG. 12, an infrared cut filter 160 may be used on the glass surface of the fluorescent lamp 1. In this case, the color filter 5 placed in front of the silicon photodiode 6 that monitors the amount of light from the fluorescent lamp 1 becomes unnecessary.

Furthermore, as shown in FIG. 13, a heat-retaining heater 170 may be used around the fluorescent lamp 1 to improve the startup characteristics of the fluorescent lamp. Note that 171 is a controller for the heater 170, which detects the temperature of the heater 170 using a thermistor 172 and operates to keep the temperature of the heater 170 constant.

Also, as a CCO line sensor, 690rv to 1100
A similar effect can be obtained even if a material not sensitive to nm infrared light is used.

In addition, it goes without saying that the present invention can be modified in various ways within the scope of its gist.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to maintain an appropriate amount of light from the light source without being affected by the infrared light output from the light source, and it is possible to read image information correctly and to maintain stable color. This has the effect that decomposition characteristics can be obtained.

[Brief explanation of the drawing]

1 to 10 show an embodiment of the present invention,
Figure 1 is a schematic configuration diagram showing the document reading device, Figure 2 (a) is a graph showing the emission spectrum of a fluorescent lamp at low temperatures, and Figure 2+b> shows the emission spectrum of a fluorescent lamp at a stable temperature. Graphs, Figure 3 is a graph showing the spectral transmittance of an infrared cut filter, Figure 4 is a graph showing changes in the amount of visible light when no stabilization is applied, and Figure 5 is a graph showing the amount of visible light. A graph showing the emission spectrum of a fluorescent lamp in lighting II when stabilization is performed. Figure 6 is a graph showing temporal fluctuations in the amount of light when the amount of visible light is stabilized. A graph showing the spectral distribution of a fluorescent lamp transmitted through an infrared cut filter, Fig. 8 A graph showing the spectral sensitivity of a crawler sensor, and Figs. A graph showing the emission spectrum when sealed, FIG. 11 is the first other example, the first
FIG. 2 is a configuration diagram showing a second alternative embodiment, and FIG. 13 is a configuration diagram showing a third alternative embodiment. 1... Fluorescent lamp, 2... Light control device, 3... CPU. 4... Operation button, 5... Infrared cut filter (removal means), 6... Light amount detector, 7... Infrared cut filter (removal means), 8... Glass, 9...・Manuscript,
11... Color separation filter, 12... CCD line sensor. Applicant's agent Patent attorney Suzu II Takehiko Ibaraga (nm) (a) Figure 3 Wavelength (b) Figure 2 Figure 4 Growth (nm) Figure 5 Figure 7 Figure 6

Claims (5)

[Claims] (1) In a document reading device that irradiates a document with light from a light source and reads the reflected light with a reading sensor, the light emitted from the light source ranges from approximately 690 nm to 1100 nm.
nm infrared light or infrared light including this, the reading sensor reads the light from which the infrared light has been removed by the removing means, and the infrared light is removed by the reading sensor. The amount of light from the removed light source is detected by a light amount detector, or a light amount detector that is not sensitive to infrared light is used to detect the amount of light from the light source, and the amount of light emitted from the light source is controlled according to the detected amount of light. A document reading device characterized by having a configuration in which: (2) The document reading device according to claim 1, wherein the light source is a fluorescent lamp. (3) The removal means includes first and second infrared light cut filters, the first infrared light cut filter is provided in the illumination system of the light source, and the second infrared light cut filter is provided opposite to the light amount detector. A document reading device according to claim 1, characterized in that: (4) Claim 3, characterized in that the first infrared light cut filter is provided on the light receiving side of the reading sensor.
The document reading device described in Section 1. (5) The document reading device according to claim 1, wherein the removing means includes an infrared light cut filter surrounding the outer periphery of the light source.