JPH0418849A - Picture reader - Google Patents

Abstract

PURPOSE:To faithfuly read the reflection rate of an original by executing dummy lighting prior to the reading of a picture through the use of a light source for original illumination. CONSTITUTION:A blue light source 3a, a green light source 3b and a red light source 3c, all of which are the light sources for original illumination 3, a first reflecting mirror 4a, a second reflecting mirror 4b, an optical lens 5 and a CCD image sensor 6 are mounted on the frame of a read head. The picture on the original 1 is reflected on the first reflecting mirror 4a and the second reflecting mirror 4b, is image-formd on the light-receiving picture element of the image sensor 6 by the optical lens 5, is photoelectrically converted and electric information can be obtained. The color of the original 1 is resolved by sequentially switching the light sources 3. In such a case, the light sources 3 are dummy-illuminated prior to the reading of the picture and an output voltage more than prescribed quantity is generated from the image sensor 6, whereby the signal rise delay of the image sensor 6 is compensated. Thus, the reflection rate of the original is faithfuly read even if the reflection rate suddenly changes in intermittent reading.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the field of information processing and office equipment, and more particularly to an image reading device.

[Prior Art] As a means for inputting image information into information processing equipment,
An image reading device is used. This generally involves converting the optical information of the document from which image information is to be obtained into electrical information using a photoelectric conversion means, that is, an image sensor.
This enables processing of image information in information processing equipment.

In an image reading device, optical information of a document is generally imaged onto an image sensor using a light source such as a fluorescent tube, a halogen lamp, or an LED, and a lens. There are several types of image sensors depending on their method and form, but in practice, an image sensor called a CCD image sensor is widely used.

[Problems to be Solved by the Invention] A CCD image sensor generates an output voltage proportional to the amount of light incident on its light receiving pixel surface. However, if the amount of incident light is very low and a certain amount of time has passed, the generation of the output voltage will be delayed, and an output voltage proportional to the amount of incident light will not be obtained, resulting in an output voltage that is much lower than the value that should be generated. For example, when an image reading device is used in connection with a computer, if the signal transfer speed of the interface or the processing speed of the computer is slow, the image reading device may operate intermittently. In other words, out of the entire required reading range, only the range that can be processed by the interface or computer is read and then interrupted.
Read the next part after processing is completed. During the interruption, the document illumination light source is normally turned off, so almost no light is incident on the CCD image sensor, and when reading resumes, a voltage lower than the original output voltage is output. Therefore, boundaries occur in the read image output. FIG. 4(a) shows a --like gray original. FIG. 4(b) is a signal output diagram from the CCD image sensor when reading the gray original shown in FIG. 4cb>.

In this way, the output voltage drops several times after reading resumes. Therefore, boundaries appear in the read output image. Next, if there is a high-density part with very low reflectance in the document, the image signal of the document following that part with low reflectance, that is, the output voltage from the CCD image sensor, will have a low value, resulting in Areas of the document adjacent to low-reflection areas appear darker than they actually are. When reading a black and white striped pattern, the image signal level of the white line decreases, resulting in a decrease in contrast and, as a result, a deterioration in resolution. FIG. 5(a) shows a document whose reflectance changes rapidly and its reading direction. FIG. 5(b) is a signal output diagram from the CCD image sensor when reading as shown in FIG. 5(a).

In this case, however, the output voltage is low even though the white portion is actually being read because the reflectance document has been read for more than a certain period of time. Therefore, the black and white boundary line becomes blurred in the read output image.

The present invention solves the above-mentioned problems, and provides an image reading device that faithfully reads the reflectance of a document even when reading is performed intermittently or when the reflectance of the document changes rapidly. It is an object.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention uses a light source for document illumination to perform dummy lighting prior to image reading.

[Operation] Prior to image reading, the light source for document illumination of the image reading device is dummy lit to generate an output voltage of a certain amount or more from the CCD image sensor, thereby compensating for the signal rise delay of the CCD image sensor.

[Example code] A detailed description of the present invention will be given according to examples.

FIG. 1 is a sectional view of a reading head of an image reading device according to an embodiment of the present invention. This embodiment shows an example of a color image reading device that performs three-color separation by blinking a three-color light source. A document 1 is placed on a document table glass 2. A frame (not shown) of the reading head includes a blue light source 3a serving as document illumination light B3, a green light source 3b, a red light H3c, a first reflecting mirror 4a, a second reflecting mirror 4b, an optical lens 5, and a CC.
It is equipped with a D image sensor 6. The image on the original 1 is reflected by the first reflecting mirror 4a and the second reflecting mirror 4b, and then formed into a real image by the optical lens 5 on the light-receiving pixels of the CCD image sensor 6. Photoelectric conversion is performed in the CCD image sensor 6, and optical information of the document 1 is obtained as electrical information. Further, color separation of the original 1 is performed by sequentially switching and lighting the original illumination light source 3.

FIG. 2 is an operational diagram of the original illumination light source 3 and the CCD image sensor 6 in one embodiment of the present invention shown in FIG.

Here, a blue light source 3a is used as an image reading light source,
A case is shown in which a green light source 3b is used as a dummy lighting light source. Normal image reading is performed using the blue light source 3a, and the blue light source 3a is turned off when image reading is interrupted.

Then, before restarting image reading, the green light source 3
After the dummy lighting is performed for a necessary light accumulation period, the green light source 3b is turned off, and then the blue light source 3a is turned on to resume normal image reading.

In this manner, by performing dummy lighting prior to image reading, the output voltage of the CCD image sensor 6 rises sufficiently during the light accumulation period during which the dummy lighting is performed, and practically no delay in rising of the output voltage occurs.

FIG. 3 is an operational diagram showing another example of the operation of the document illumination light source 3 and the CCD image sensor 6 in the embodiment of the present invention shown in FIG. In this example, dummy lighting is performed during the entire standby period from the interruption of reading to the restart of reading, and moreover, the dummy lighting is turned on at a lower duty than normal lighting. According to experiments conducted by the inventor, it has been confirmed that the longer the dummy lighting is performed, the greater the compensation effect for the delay in rising the output voltage of the CCD image sensor. Also, by setting the dummy lighting to a low duty, the amount of light, that is, the output voltage, decreases, but if the dummy lighting is performed continuously like this, the required effect can be achieved even if the lighting duty is reduced to about 5% of the normal lighting. It has also been confirmed that this can be achieved. Therefore, by performing dummy lighting control as in this embodiment, heat generation and energy consumption due to dummy lighting can be minimized while ensuring a compensation effect for the delay in rising the output voltage of the CCD image sensor.

FIG. 4(C) is a signal output diagram from the CCD image sensor in one embodiment of the present invention when reading the gray original shown in FIG. 4(a). Here, when reading is resumed after reading is interrupted, dummy lighting is performed prior to reading, so the image signal does not change before and after reading is interrupted, and no boundaries occur in the read output image.

FIG. 5(b) is a signal output diagram from a CCD image sensor in another embodiment of the present invention when reading a document as shown in FIG. 5(a). In this embodiment, dummy lighting is performed for reading out all image signals. In a normal document, however, there is a small amount of output from the CCD image sensor even in the reflectance portion, so the dummy lighting produces a compensation effect for the delay in rising the output voltage of the CCD image sensor. Therefore, even when reading a document whose reflectance changes rapidly, the CC
The output voltage of the D image sensor sufficiently follows and accurate reading is possible. [Effects of the Invention] As described above, according to the present invention, appropriate software control can be added to a conventional image reading device. Accordingly, it is possible to provide an image reading device that can faithfully read the reflectance of a document even when reading is performed intermittently or when the reflectance of the document changes rapidly. The present invention does not require the addition of physical equipment, and only requires changing the software, so there is no cost increase.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a reading head of an image reading device using an embodiment of the present invention. FIG. 2 is an operational diagram of a light source and a CCD image sensor in one embodiment of the present invention. FIG. 3 is an operation diagram showing another example of the operation of the light source and CCD image sensor in one embodiment of the present invention. FIG. 4(a) is a diagram of a --like gray original. FIG. 4(b) is a signal output diagram from the CCD image sensor in the conventional example when reading the gray original shown in FIG. 4(b). FIG. 4(C) is a signal output diagram in the present invention. Fifth
Figure (a) is an explanatory diagram of reading a document whose reflectance changes rapidly. FIG. 5(b) is a signal output diagram from the CCD image sensor in the conventional example when reading as shown in FIG. 5(a). FIG. 5(C) is a signal output diagram in the present invention. 1...Original 2...Document table glass 3a...Blue light source 3b...Green light source 3c...Red light source 4a...First reflecting mirror 4b...First 2 Reflector 5...Optical lens 6...COD image sensor Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kisanbe Meiki 1 person Figure 3 Figure 1 Figure 2 (Q) Figure 4

Claims (5)

[Claims] (1) In an image reading device using a CCD image sensor and one or more light sources for document illumination, dummy lighting is performed to turn on the light source for document illumination during at least one light accumulation period prior to reading out an image signal. An image reading device characterized by: (2) The document illumination light source used for the dummy lighting is:
2. The image reading apparatus according to claim 1, wherein the image reading apparatus is different from a light source for illuminating a document that is turned on when reading the image signal. (3) The image reading device according to claim 1 or 2, wherein the dummy lighting is turned on only when reading is resumed after image reading is interrupted. (4) Claim 1 or Claim 2, wherein the dummy lighting is lit for reading out all image signals.
The image reading device described. (5) The dummy lighting can be selected between being turned on only when reading is restarted after image reading is interrupted, and being turned on when reading all image signals. The image reading device described.