JPH02155364A - Original reader - Google Patents

Abstract

PURPOSE:To reduce the deviation the coloring of a read original by turning an image forming optical means so as to vary an incident angle of a reflected light from the original against a change in a spectrum transmittivity of the image forming optical means due to a temperature change in the reader. CONSTITUTION:When a temperature in an optical system unit 5 rises, its temperature change is sensed and an infrared ray cut dichroic filter 3 is driven from a predetermined position by an angle corresponding to the temperature change. Thus, the wavelength of a light equivalent to 50% of the spectrum transmittivity is made unchanged from the read start position before temperature rise to keep the color balance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a reading device that reads a document by receiving reflected light from an illuminated color document on a color image sensor. The present invention relates to control for correcting changes in spectral transmittance due to temperature changes of an infrared cut dichroic filter provided to remove harmful infrared light.

(Prior Art) A conventional color document reading device is used as a document reading device of, for example, a full color copying machine. A schematic diagram of this conventional color document reading device is shown in FIG. 2. As shown in FIG. ), the image is formed on a color image sensor 4 (for example, a solid-state image sensor such as COD), and during that time, the color is separated into each component of B (blue), G (green), and R (red). I was reading the manuscript. At this time, in order to remove harmful infrared light contained in the reflected light from the original that enters the image sensor 4, an infrared cut dichroic filter 3 is installed in the reading optical system consisting of the SELFOC lens array, etc. It was fixed at right angles to the chief ray to read color originals. In order to show the function of this infrared cut dichroic filter, Figure 3 shows a graph of the spectral transmittance of the infrared cut dichroic filter. It can be seen that

(Problem to be Solved by the Invention) However, according to the fixed infrared cut dichroic filter in the prior art, the spectral transmittance changes depending on the temperature, as shown in FIG. 3, and some light is removed and some light is not. As a result, the spectral distribution and light amount of light having each wavelength on the color image sensor 4 would change. When such a change occurs, the light intensity balance of the B, G, and H components that make up the color of a color document is disrupted, causing a color shift between the actual color of the document and the color that is read. There was a problem.

This invention was made in view of the above problems, and an object of the present invention is to provide a document reading device that can correct deviations in the spectral transmittance of an infrared cut dichroic filter caused by changes in temperature. do.

(Means for Solving the Problems) The present invention provides a document reading device that receives reflected light from an illuminated document through an infrared cut dichroic filter to a photoelectric conversion element to read the document. and a control means for controlling the angle of incidence of light reflected from the document onto the infrared cut dichroic filter by rotating the infrared cut dichroic filter according to the detection signal. This document reading device is characterized by the following.

(Function) The angle of incidence of the light reflected from the original onto the infrared cut filter (
By performing control to change the spectral transmittance (see FIG. 4 (CB)) in response to temperature changes, the spectral transmittance of the filter can be changed in accordance with the incident angle, as shown in FIG. 4 (A). Therefore, as shown in FIG. 3, by changing the incident angle, it is possible to correct the wavelength shift caused by the temperature change of the imaging optical system by shifting it in the direction opposite to the wavelength shift.

(Embodiment) A first embodiment of the document reading device of the present invention will be described with reference to FIG. 1 and FIGS. 5 to 7. FIG. 1 is an overall schematic diagram of this embodiment, and corresponds to FIG. 2 of the prior art. A color document S placed on a transparent document platen glass is illuminated from below by a document illumination lamp, and the light reflected from the document is reflected by a SELFOC lens array 2 (hereinafter referred to as S).
The reflected light is collected by an infrared light filter (referred to as LA), and further passes through an infrared cut dichroic filter 3 to remove harmful infrared light contained in the reflected light. The reflected light received by the color image sensor (photoelectric conversion element) 4 is B, G, R8.
is decomposed into light with a wavelength of minutes and converted into an electrical signal. These 5LA2, infrared cut dichroic filter 3
, and the image sensor 4 are combined into one optical system unit 5, and temperature changes within this optical system unit 5 can be detected by a thermometer (not shown).

Next, the infrared cut dichroic filter 3 is rotated in accordance with the detected temperature change inside the optical system unit 5, and a mechanism for changing the incident angle of the reflected light incident on the infrared cut dichroic filter 3 is installed. This will be explained with reference to FIG. As shown in the figure, the infrared cut dichroic filter 3 inside the optical system unit 5 is supported by left and right filter supports 6. The fulcrum of this filter support 6 is freely rotatable, and the infrared cut dichroic filter 3 can be rotated by changing the relative vertical position of the left and right filter supports 6. The filter support 6 has a male thread cut on its surface, and is screwed into a female thread in a hole vertically provided in the case of the optical system unit 5.

The filter support 6 is rotated around an axis by a step motor (not shown) and moved vertically relative to the hole, thereby rotating the filter.

Next, the control for rotating this infrared cut dichroic filter will be explained with reference to the control block diagram in Fig. 7.6 The electrical signal representing the temperature inside the optical system unit 5 detected by a thermometer (not shown) is amplified by an amplifier. After that, A/
D conversion is performed, and an arithmetic circuit calculates the wavelength deviation Δin which corresponds to temperature change, and in order to adjust the deviation amount to an incident angle that cancels it, the filter support 6 is moved up and down by the step motor (not shown) and an infrared cut dichroic device is used. Rotate the filter 3 to a predetermined angle.

Now, the operation of the document reading apparatus having the configurations shown in FIGS. 1, 5, and 7 will be explained. In this embodiment, the document S in FIG. 1 is stationary, and the optical system unit 5 moves over the entire width of the document S. At this time, the document is illuminated by lighting the document illumination lamp l.
The reflected light passes through the 5LA 2 and the infrared cut dichroic filter 3 and forms an image on the color image sensor 4. However, for example, if a plurality of documents S are read in succession and the temperature inside the optical system unit 5 rises due to the lighting of the document illumination lamp 1 for a long period of time, the infrared cut dichroic filter 3 will cause the infrared cut dichroic filter 3 to emit light as shown in FIG. The transmittance shifts toward the short wavelength side (to the left in the figure). However, depending on the material of the infrared cut dichroic filter, there are some that shift to the long wavelength side (to the right in the figure). When the degree rises to 60 degrees, the wavelength of the light located at the position where the spectral transmittance is 50% shifts to the short wavelength side by Δ input = 8nrm.For this reason, the original is read without any correction. In contrast, in this embodiment, as described above, the infrared cut dichroic filter 3 is rotated to change the incident angle of the reflected light. This method utilizes this property that when the incident angle 0 (see FIG. 4 CB) of the reflected light of the dichroic filter 3 as shown in FIG. 4 (A) changes, the spectral transmittance graph shifts by several n1. When the temperature inside the optical system unit 5 rises, the temperature change is detected, and the infrared car and the Todaichro filter 3 are rotated from a predetermined position by an angle corresponding to the amount of temperature change. By doing so, the incident angle θ of the reflected light is changed, and the spectral transmittance graph is shifted to the longer wavelength side (right side) in FIG. 4(A), in order to correct the shift caused by the temperature rise.

In other words, if the temperature rises and the spectral transmittance graph shifts to the short wavelength side (to the left in the figure), a large amount of the R component of R, B, and G that corrects color will be cut, so The blue tint becomes stronger. Therefore, in order to prevent a strong blue tint, the infrared cartridge 2 is rotated to reduce the incident angle θ of the reflected light to the dichroic filter 3, and the spectral transmittance graph shown in Fig. 4 (A) is plotted. It is shifted in the direction of the cloth. This ensures that the wavelength of light with a spectral transmittance of 50% does not change from the reading start position before the temperature rises, and continues to maintain color balance. By directly detecting the temperature inside the optical system unit 5 in this way and making corrections according to the temperature, for example, as described above, the document illumination lamp 1 can be kept on for a long time, and the temperature inside the optical system unit can be reduced. Even when reading a plurality of documents in succession, where the color rises significantly, the color balance of the read document can be maintained.

(Other Embodiments) In the first embodiment described above, a thermometer that directly detects the temperature inside the device is provided as the temperature detection means, but in other embodiments, infrared Focusing on the fact that the spectral transmittance of the cut dichroic filter 3 changes and as a result the R component output signal output from the image sensor changes, the infrared cut dichroic filter is rotated according to this R component output signal. It is also possible to control

That is, as shown in FIG. 8, as the document reading time of the document reading device becomes longer, the output signal of the R component output from the image sensor 4 decreases.This is explained in detail in the first embodiment. As mentioned above, this is because the spectral transmittance of the infrared cut-dyegro filter shifts to the shorter wavelength side due to an increase in temperature, causing a large amount of the R component to be carted out.

Therefore, as shown in Figure 9, an image sensor (COD)
), the difference between the R component output signal and the R component output signal at the start of reading is calculated, and the angle of incidence of the reflected light from the document is controlled by this difference (see Figure 4 (B)). do. When the output signal of the R component decreases, the angle of incidence θ is decreased in accordance with the amount of decrease (see Fig. 4 (A).
)) and make corrections.As a result, even if the temperature inside the device is not directly detected, the temperature can be estimated and detected indirectly according to the R component output signal from the image sensor. The angle of incidence θ can be changed by rotating the infrared cut dichroic filter.

The third embodiment shown below does not directly detect temperature changes within the device, but controls by rotating an infrared cut dichroic filter according to the continuous reading time of the document reading device, that is, the number of sheets read. . That is, when a plurality of documents S are read continuously, there is a certain relationship between the continuous reading time and the temperature change inside the apparatus, that is, inside the optical system unit, as shown in FIG. The temperature rises rapidly at the start of reading, then gradually slows down, and once it rises to a certain temperature (A° C. in the figure), the temperature is maintained at approximately that temperature thereafter. Therefore, the time required for the temperature to reach a certain temperature A℃ from the start, that is, the number of sheets to be read, is known in advance, and these are divided into multiple stages, and when the number of sheets continuously read reaches, for example, n], the infrared light is applied. y) Move the incident angle θ of the dichroic filter 3 by 01 turns from the reference position. Similarly, at the time of n2, 02,・
... Rotate θn at the point of nn.

The first embodiment required a thermometer to directly detect the temperature, and the second embodiment required a monitoring device that read only the R component output signal from the image sensor. The third embodiment requires only a device that simply detects the number of consecutively read sheets during continuous reading, which simplifies the device. In this case, by detecting the number of continuously read sheets, the temperature inside the apparatus, that is, the temperature inside the optical system unit 5, can be indirectly estimated and detected.

However, for example, if continuous reading is performed immediately after 8 sheets have been read continuously, reading is stopped during that time, so the temperature will rise again before it has completely fallen, as shown in Figure 11. . Therefore, when continuous reading is restarted after a short interruption period, the interruption period should be measured and memorized, and if the reading is restarted before the temperature has completely fallen, the It is necessary to perform control that takes into account the temperature that has not been completely lowered.

In one or more embodiments, a structure in which the left and right filter supports 6 are moved in the vertical direction as shown in FIGS. 5 and 6 has been described as a structure for rotating the infrared cut dichroic filter, but other embodiments are also possible. In this example, as shown in FIG. 12, an infrared cut dichroic filter is fixed to one rotating shaft 7, and the direction of this rotating shaft 7 is not vertical. Along with the rotation, the infrared cut dichroic filter 3 can be rotated and the incident angle θ can be changed.

(Effects of the Invention) As explained above, the document reading device of the present invention rotates the imaging optical device to handle the change in the spectral transmittance of the imaging optical device due to temperature changes within the device. By changing the incident angle of the reflected light and correcting the spectral transmittance in the opposite direction, it is possible to reduce the color shift in the read document.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view of the entire device showing the first embodiment of the present invention, FIG. 2 is a schematic vertical cross-sectional view of the entire conventional device, and FIG. 3 is the spectrum of the infrared cut dichroic filter shown in FIG. A diagram showing changes in transmittance due to temperature changes, FIG. 4(A) is a diagram showing changes in spectral transmittance due to incident angle θ, and FIG. 4(B) is a diagram showing the incident angle of FIG. 4(A). , FIG. 5 is a sectional view showing a mechanism for rotating the filter in FIG. 1, FIG. 6 is an external perspective view of FIG. 5, and FIG. 7 is a control block diagram of the first embodiment.
FIG. 8 is a diagram showing the output signal level of the R component of color for a continuous reading device for explaining the second embodiment of the present invention, FIG. 9 is a control block diagram of the second embodiment, and FIG. FIG. 11 is a diagram showing the temperature change with respect to continuous reading time to explain the third embodiment. FIG. 11 is a diagram showing the temperature change when continuous reading is resumed after a short interruption period. FIG. 12 is another example. FIG. 3 is a schematic diagram showing a mechanism for rotating the imaging optical means in FIG. Explanation of symbols S...Document 1...Document illumination lamp 2.
...5LA (lens) 3...Infrared cut dichroic filter 4...Image sensor (photoelectric conversion element) 5...Optical system unit
6... Filter support 7... Rotation axis number 1 Constant wave + x) (nm" + 17 Figure 8 Figure 2 Figure 3 2÷ and 4

Claims (1)

[Scope of Claims] A document reading device that reads a document by receiving reflected light from an illuminated document by a photoelectric conversion element via an imaging optical device, comprising: a temperature detection device that detects a temperature change within the device; A document characterized in that a control means is provided for controlling the incident angle of reflected light to an infrared cut dichroic filter in an imaging optical system by rotating the infrared cut dichroic filter in accordance with the detection signal. reading device.