JPH0379156A - Image reader - Google Patents

Abstract

PURPOSE:To miniaturize a device and to improve operability by providing a fixing plate, a light source, and an optical system for a transmission original other than the fixing plate, the light source, and the optical system for a reflection original, and sharing a photoelectric conversion system consisting of a line sensor. CONSTITUTION:The reflection original is fixed at a reflection original platen 1, and is irradiated with a first optical system consisting of a filament light source 2 and a reflecting mirror 3, and a photoelectric sensor 4 by moving them with a driving means 5, and is photoelectrically converted 4, and output is A/D-converted 8. Meanwhile, a frame 11 on which the transmission original is placed is moved with a driving means 14 as irradiating with a filament light source 12 from a back plane. Transmission light is converged on a semi-cylindrical lens 17, and is image-formed on a white scattering plate 24 provided at the aperture part 22 of a reflection original reading means 20 via a reflecting mirror 18. At this time, the photoelectric sensor 4 is fixed by moving just underneath the aperture part 24, and the output is A/D-converted 8. Shading correction 9 is applied on the output A/Dconverted 8, and the fluctuation of a light quantity is corrected 10, and an image signal is outputted to a signal processing means not shown in figure.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable not only to originals having reflective spectral characteristics, but also to
The present invention relates to an image reading device capable of reading originals having transmission-type spectral characteristics, particularly small-sized transmission originals such as Sly 1 film.

[Summary of the invention]

The present invention separates the optical system for reflective originals and the light source, optical system, and drive means for transparent originals, and provides an optimal light source and optical system for each, thereby producing images with excellent image quality and operability. A reading device is provided.

[Conventional technology]

In a conventional image reading device, as shown in FIG. 3, a reflective document table 1 for fixing a reflective document, a linear first light source 2 for illuminating the reflective document fixed to the reflective document table, and a first linear light source 2 for illuminating the reflective document fixed to the reflective document table, a first optical system 3 that forms an image of a reflected original obtained by irradiation with a light source on a sensor surface; and a line that converts optical image information formed by the first optical system into an electrical signal. a first driving means 5 that slides and moves the sensor 4 and the first optical system or the sensor 3 integrated with the first optical system in the sub-scanning direction; and the reflective document table 1.
a sub-scanning reference plate 6 disposed parallel to the main scanning direction on the same plane as the sub-scanning reference plate 7 disposed parallel to the sub-scanning direction, and A for converting the output signal of the sensor 4 into a digital signal. /D conversion means 8, shading correction means 9 that performs shading correction according to the value of the signal read from the main scanning reference plate, and light amount fluctuation that corrects the light amount fluctuation of the light source according to the value of the signal read from the sub-scanning reference plate. Correction means 1
0, a mount 11 for fixing the transparent original, a point light source 23 for illuminating the transparent original fixed to the mount 11, and an image of the transparent original projected by the point light source 23. a second optical system 13 for forming an image on the reflective original table 1, and a passing original projecting means 21 which is separate from the reflective original reading means 2o.

The operation will be explained below with reference to the drawings.When reading a zero-reflection original, the transmission original projection means 21 is separated from the reflection original reading means 20, and only the reflection original reading means 20 operates. The original is fixed on a reflective original table l with the original surface facing the sensor 4. Here, in accordance with a reading start command from a control means (not shown), the first light source 2 is turned on and the original reading operation is started. First, the first driving means 5 drives the first light source 2. The grain sensor 4 integrated with the first optical system 3 is moved directly below the main scanning reference plate 6. At this position, the sensor 4 reads the main scanning reference plate 6 and generates an electrical signal. The A/D conversion means 8 converts this electrical signal into a digital signal and outputs it to the light amount fluctuation correction means 10 and the shading correction means 9. The light intensity variation correction means 10 outputs a signal defining the dynamic range of the A/D conversion means 8 to the A/D conversion means 8 in accordance with the above-mentioned signal. On the other hand, the synering correction means 9 stores information for correcting the spectral distribution of the first light source 2, the light transmission characteristics of the first optical system 3, and the sensitivity variations of the sensor 4 according to the above output. do. Next, in order to read the original, the first driving means 5 moves the first light source 2, first optical system 3, and sensor 4 in the sub-scanning direction at a constant speed from the starting position to the ending position of reading the original. move it to The sensor 4 sequentially converts image information of the document into electrical signals while moving directly under the document in the sub-scanning direction, and outputs the electric signals to the A/D conversion means 8 . At this time, the sensor 4 reads not only the image information of the document but also the information of the sub-scanning reference plate 7 arranged in the sub-scanning direction at the end of the reading range as shown in FIG. 2, and outputs it as an electrical signal. It is something. The A/D conversion means 8 converts the electric signal from the sensor 4 into a digital signal, and the signal based on the image information of the document is sent to the shading correction means 9.
A signal based on the sub-scanning reference plate 7 is output to the light amount fluctuation correcting means 10. The shading correction means 9 corrects the image signal based on the previously obtained shading correction information and outputs the image signal to a signal processing means (not shown). On the other hand, the light amount fluctuation correction means 10 adjusts the dynamic range of the A/D conversion means 8 to correct the fluctuation when there is a fluctuation in the first light source 2 based on the signal obtained by reading the sub-scanning reference plate 7. This enables stable reading of image information even if there are variations in the sensitivity of the light source, optical system, or sensor, or even if the output of the light source fluctuates during the image reading period. This is the result. When the reading of the original is completed in this way, the control means (not shown) turns off the first light source 2, returns the sensor 4 to a predetermined position via the first driving means 5, and starts the operation of reading the original. It ends.

Next, the case of reading an image on a transparent original will be described. In this case, the transparent original projection means 21 mentioned above is fixed on the reflective original table 1 of the reflective original reading means 20 to perform reading. The operation will be explained below. The i3 original is fixed on the stand 10.

The point light aI 23 projects the transparent original fixed on the stand 10 and forms an image on the original onto the reflective original table 1 via the second optical system 13. When reading a small transparent original, such as a slide film, it is common to project the image in an enlarged manner. At this time, a projection screen made of a transparent white scattering plate may be placed on the reflective document table l. Hereinafter, the image formed on the reflective document table 1 in this manner is read as if the reflective document were placed on the document table, using the same procedure as that for reading the reflective document described above. be. Note that at this time, it is also possible to perform shading correction and light amount fluctuation correction by arranging a transparent reference plate near the main scanning reference plate 6 and the sub-scanning reference plate 7 so as to be parallel to each reference plate. .

[Problem to be solved by the invention]

Conventional image reading apparatuses use a point light source when reading a transparent original to form an image of the original on the entire surface of a reflective original table, which causes the following problems.

That is, as shown in Fig. 4(b), the light intensity distribution due to the point light source falls concentrically around the optical axis, and furthermore, as shown in Fig. 4(e), in order to form an image on the entire surface of the document table. In the optical system used, the amount of peripheral light decreases according to the cosine fourth law, so that the overall light intensity distribution on the document table surface becomes as shown in the figure fdl. In this way, it is difficult to obtain a uniform light intensity distribution over the entire surface of the document table, and there is a problem in that if the document is read as is, the periphery of the document becomes dark. Also, for the same reason, A-a and B-b in Figure 4
As shown in , the shape of the light intensity distribution changes depending on the position on the document table, so even if information for shading correction is obtained in advance, such as when scanning a reflective original, it is necessary to perform appropriate correction. However, there was a problem in that unevenness in brightness occurred in the read image information. In addition, in order to solve this problem, the position of the point light source in Fig. 4(a) is changed to Z.
Moving the document farther away in the direction avoids the effects of a decrease in light intensity and allows the document to be read within a relatively stable light intensity distribution range, which is effective in stabilizing the quality of the output image. However, this creates new problems such as making the entire device large and significantly deteriorating the operability.Also, it is also effective to use a line light source similar to the first light source instead of a point light source. However, the newly installed line light source must be scanned in synchronization with the sensor, and a new driving means must be provided for this purpose, which increases the cost and increases the size of the entire device. In addition, the transparent original projection means, including the means for driving the line light source, must be attached and detached, which creates a new problem such as extremely poor operability as in the previous example. I end up.

Further, in the mechanism for projecting the image of a transparent original onto a reflective original platen, the transparent original projecting means must be attached and detached each time the type of original changes, resulting in poor operability.

[Means to solve the problem]

In order to solve the above problems, the present invention uses a line light source as a light source for reading a transparent original, and when reading a transparent original, the sensor is fixed and the pedestal on which the original is fixed is moved. The means and the transparent original projection means are optically connected through an opening provided at a position different from the reflective original table.

[Effect]

By using a line light source as a projection light source for a transparent original, it is possible to perform shading correction and light amount fluctuation correction similar to when reading a reflective original, and it is possible to obtain stable image output.

Furthermore, when reading a transparent original, we created a mechanism that moves and operates the transparent original while keeping the sensor fixed.
The moving distance of the document can be reduced in accordance with the magnification of the enlarged projection, and the entire apparatus can be made smaller. In addition, since the optical connection between the reflective original reading means and the transparent original projecting means is made through an opening provided at a location separate from the reflective original table, even if the type of original changes, the transparent original projecting means can be attached and removed. (Able to do reading work.)

〔Example〕

An embodiment of the present invention will be described below based on the drawings. 1st
The figure is a block diagram showing one embodiment of the present invention, and FIG. 2 is a diagram showing the main elements of the embodiment as viewed from the top of the device.

Reference numeral 1 denotes a reflective document table for fixing a reflective document, 2 a linear first light source that irradiates the reflective document fixed to the reflective document table, and 3, an image of the reflective document obtained by being irradiated by the first light source 2. 4 is a line type sensor that converts the optical image information imaged by the first optical system 3 into an electrical signal; 5 is the first optical system 3; 6 is a main scanning reference plate arranged parallel to the main scanning direction on the same plane as the reflective document table l; 8 is a sub-scanning reference plate arranged parallel to the sub-scanning direction, 8 is an A/D conversion means for converting the output signal of the sensor 4 into a digital signal, and 9 is a shading correction according to the value of the signal read from the main scanning reference plate 6. 10 is a light amount fluctuation correcting means for correcting the light amount fluctuation of the light source according to the value of the signal read from the sub-scanning reference plate 7; reflective original reading means composed of 20 or more elements; 11 is a transparent original 12 is a linear second light source that irradiates the transparent original fixed to the mount 11; 13 is a second light source that projects an image of the transparent original onto the reflective original table 1; A second optical system includes a lens 17 and a reflecting plate 18 that form an image on a transparent white scattering plate 24 provided in an opening 22 provided on the same plane; a second driving means for moving while sliding in the direction;
Reference numeral 15 denotes a transparent main-scanning reference plate arranged on the pedestal 11 in parallel to the main scanning direction, 16 refers to a transparent sub-scanning reference plate arranged parallel to the sub-scanning direction, and 21 refers to a transparent reference plate composed of the above elements. The transparent original projecting means 21, which is an original projecting means, is optically connected to the reflective original reading means 20 by a white scattering plate 24 located above an opening 22 provided in the reflective original reading means 20.

Further, reference numeral 19 denotes a light shielding plate installed to prevent direct light from the second light source 12 from entering the sensor 4, but in this embodiment, it is a light shielding plate that is separate from the reflective original reading means 20 and the transparent original projecting means 21. Therefore, the reflective original reading means 20
The external case also serves as a light shielding plate.

The operation will be described below with reference to the drawings.The operation when reading a zero-reflection type original is the same as that of the conventional example, so the explanation thereof will be omitted. When reading a transmissive type original, the original is fixed on a stand 11. In accordance with a reading start command from a control means (not shown), the first driving means 5 moves the first optical system 3 and the sensor 4 directly below the opening 22 and fixes them therein. Further, the second light source 12 is turned on and the original reading operation is started.

First, the second driving means 14 moves the pedestal 11 to position the transparent main scanning reference plate 15 on the optical axis indicated by the dashed line in FIG. At this position, the sensor 4 reads the light transmitted through the transparent main scanning reference plate 15 and generates an electrical signal.

The A/D conversion means 8 converts this electrical signal into a digital signal and outputs it to the light amount fluctuation correction means 10 and the shading correction means 9. The light intensity variation correction means 10 outputs a signal defining the dynamic range of the A/D conversion means 8 to the A/D conversion means 8 in accordance with the above-mentioned signal. On the other hand, the shading correction means 9 uses the second light source 12 according to the above output.
zero-order second driving means that stores information for correcting the spectral distribution of the optical system, correcting the light transmission characteristics of the first optical system 3 and the second optical system 17, and correcting sensitivity variations of the sensor 4; Reference numeral 14 moves the mount 11 in the sub-scanning direction at a constant speed from the original reading start position to the original reading end position in order to read the original.

The sensor 4 sequentially converts the image information of the transparent original into electrical signals and outputs them to the A/D conversion means 8. At this time, the sensor 4 not only captures the image information of the document, but also captures the light transmitted through the transparent sub-scanning reference plate 16, which is disposed in the sub-scanning direction at the end of the reading range, as shown in FIG. It is read and output as an electrical signal. The A/D conversion means 8 converts the electric signal from the sensor 4 into a digital signal, and the signal based on the image information of the transparent original is sent to the shading correction means 9.
Then, a signal based on the transparent sub-scanning reference plate 16 is outputted to the light amount fluctuation correction means 10. Shading correction means 9
Then, while correcting the image signal based on the shading correction information obtained previously, the image signal is output to a signal processing means (not shown). On the other hand, the light intensity variation correcting means 10 corrects the variation if there is a variation in the second light source 12 based on the signal obtained by reading the light transmitted through the transparent sub-scanning reference plate 16. The dynamic range of the /D conversion means 8 is readjusted as needed. In the present invention, since a line light source is used as the second light source 12,
Since the shape of the spectral distribution is almost constant no matter which sub-scanning position is taken, the above-mentioned correction means operates effectively.

This makes it possible to stably read image information even if there are variations in sensitivity of the light source, optical system, or sensor, or even if the output of the light source fluctuates during the image reading period. When the document reading is finished in this way, the control means (not shown) turns off the second light source 12, returns the sensor 4 to a predetermined position via the first drive means 5, and returns the sensor 4 to a predetermined position via the first drive means 5. The pedestal 11 is returned to a predetermined position via 14, and the original reading operation is completed.

FIG. 5 is a diagram showing another embodiment. The operation is the same as in the previously described embodiment, except that the pedestal 11, the second light source 12. A part of the second optical system 13 and the second driving means 1
4 is provided on the side surface of the reflective document reading means 20 on the opposite side to the opening 22. By adopting such a configuration, it is possible to make the entire apparatus compact and at the same time to increase the optical path length, so that the second optical system 13. Especially lens 1
There is no need to improve the characteristics of 7, and it becomes possible to construct the transparent original projection means 21 at low cost. Although not shown in the figure, the first driving means 5 and the second driving means 1
4 can also be used.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a stable image signal output for both small-sized reflective type originals and transmissive type originals, and it is possible to provide an image reading device with good operability.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an image reading device representing an embodiment of the present invention, FIG. 2 is a diagram showing the arrangement of main elements of the embodiment shown in FIG. A configuration diagram showing the image reading device, the fourth diagram (al is a diagram showing the coordinates on the document table, 4th edition) is a diagram showing the light intensity distribution on the document table obtained by the light source, FIG. is a diagram showing the light limit distribution on the document table obtained by the optical system, FIG. 4 is a diagram showing the overall light intensity distribution on the document table, and FIG. 5 is a diagram showing another embodiment of the present invention. 1 is a diagram showing the configuration of an example. 1... Reflective document table 2... First light source 3... First optical system 4... Sensor 5... First driving means 6...・Main scanning reference plate 7... Sub-scanning reference plate 8... A/D conversion means 9... Shading correction means 10... Light amount fluctuation correction means 11... Mount 12... Second light source 13...Second optical system 14...Second driving means 15...Transparent main scanning reference plate 16...Transparent sub-scanning reference plate 20...Reflective original reading means 21... Transparent original projection means 22...aperture or higher

Claims (1)

[Claims] A reflective document table that fixes a reflective document; a linear first light source that irradiates the reflective document fixed to the reflective document table; and an image of the reflective document that is obtained by being irradiated by the first light source on a sensor surface. a first optical system that forms an image; a line sensor that converts optical image information formed by the first optical system into an electrical signal; and the first optical system or the first optical system. a first driving means for sliding and moving the sensor in the sub-scanning direction; a main-scanning reference plate disposed on the same plane as the reflective document table and parallel to the main-scanning direction; a sub-scanning reference plate arranged in parallel; an A/D conversion means for converting the output signal of the sensor into a digital signal;
A reflection device comprising a shading correction means for performing shading correction according to the value of a signal read from the main scanning reference plate, and a light amount fluctuation correction means for correcting a variation in the light amount of the light source according to the value of a signal read from the sub-scanning reference plate. an original reading means, a mount for fixing the transparent original, a linear second light source that irradiates the transparent original fixed to the mount, and an image of the transparent original projected by the second light source on the reflective original table. a second optical system for forming an image on the same plane as the second optical system; a second driving means for moving the pedestal while sliding it in the sub-scanning direction; An image reading device comprising a transparent main-scanning reference plate and a transparent sub-scanning reference plate disposed parallel to the sub-scanning direction. An image reading device optically coupled to a reflective document reading device through an opening provided in the device.