JPH0425283A - Picture reader - Google Patents

Abstract

PURPOSE:To obtain the same picture read density data of other original carrier driver as the picture read density data of a read means in a main body by correcting a picture read density data so as to compensate a transmission loss through a paper guide plate when the original carrier driver is in use. CONSTITUTION:A data stored in a RAM 103 is converted into an analog voltage by a D/A converter 104 at original read, an element 201 is turned on by a switching signal Sl and an analog voltage from the D/A converter 104 is used for a reference voltage of an A/D converter 101 and a ratio of the reference voltage to an original reflection quantity is used as a multi-value data and outputted from the A/D converter 101. Then the transmission ratio of the paper guide plate is set by resistance voltage division of resistors R1, R2 and an element 202 is conductive by a switching signal Sl and a voltage divided by the resistors R1, R2 is inputted as a reference voltage of the A/D converter 101. Thus, the same multi-value data by the original carrier driver is obtained from the multi-value data by this reader.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image reading device that reads an image of a document.

[Prior Art] Conventionally, in image reading devices using a -dimensional image sensor (CCD, etc.), a flatbed type (a document is fixed on an image reading table and a reading system is moved in the sub-scanning direction) is used. , a type that performs line reading (hereinafter referred to as the flatbed type), and a sheet-through type (a type in which the image reading system is fixed and the original is not moved but is read; hereinafter referred to as the sheet-through type). ).

Therefore, there is an image reading device in which a sheet-through type document conveyance unit is provided as a separate document conveyance drive device, and the document conveyance drive device is combined with a flatbed type image reading device to perform reading.

The document conveyance drive device is an independent device, and uses a transparent plate called a paper guide plate at the document reading position on the optical system in order to move the document smoothly. However, since this paper guide plate does not have 100% transmittance, the amount of light reflected from the document due to the opaque amount is reduced compared to the amount of light from the main body image reading device. Therefore, the amount of light received by the image sensor is reduced,
The dynamic range of concentration becomes narrower. Therefore, when converting the image sensor output into analog-to-digital data and using N-bit multi-value data to produce halftone expression prints that are dithered, in order to obtain print density equivalent to that produced by the main unit, The slice level for dither processing was set to a different value from that of the main device.

[Problems to be Solved by the Invention] However, in the conventional example, when an image is read using a separate document transport device, which reduces the amount of light reflected from the document,
Even if the slice level pitch for dither processing is made finer, dark areas such as those in high-density photographs cannot be resolved, resulting in image quality deterioration such as blurring.

Furthermore, when transmitting an image signal as N-bit multi-value data obtained by analog-to-digital conversion, a difference occurs in the multi-value data between the main unit and the document transport device, even though the documents have the same density. Therefore, it is necessary to convert the data into the same multivalued data on the receiving side, and if the receiving side does not have a conversion processing means, there is a problem that a difference occurs in the received image density.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading device that solves the above problems.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an image reading device capable of reading an image by an image reading means inside the main body and reading an image using a document conveyance drive device. A switching means for selecting either image reading or image reading using the document transport drive device, and correcting only the image reading signal when the document transport drive device is used based on the selection result of the switching device. It is characterized by comprising a means to do so.

[For use] According to the present invention, when a separately provided document conveyance drive device is used with the above configuration, D, /M (however, D3 is the density data when the document conveyance drive device is used,
M is the transmittance of the paper guide plate), and the density data is corrected to obtain the same density data when using the image reading means inside the main body.

[Embodiment] Fig. 1 is a block diagram showing an embodiment of the present invention, and Fig. 2 is a block diagram showing an embodiment of the present invention.
A circuit for correction calculation is shown.

First of all, in FIG. 1, 101 is an analog/digital (A/
DJ converter 102 is switched by signal S2;
This is a switch for loading data output from the RAM 103 into the RAM 103. The RAM 103 is a shading correction data memory for correcting shading occurring in the optical system of the main body image reading device. 10
4 is a digital/analog (D/Al converter,
A correction circuit 105 corrects the analog signal (VIN) of the D/A converter 104 to VIN×M.

The output of the correction circuit 105 is used as a reference voltage for the A/D converter 101.

S2 is a switching signal for loading data for correcting shading generated in the optical system into the RAM 103, and Sl is a switching signal for switching between reading by the main body reading device and reading by a separate document conveyance drive device.

In FIG. 2, 201 and 202 are analog switch elements using the switching signal S1 as a control signal, 203 is an inverting element for switching the switch elements 201 and 202 using the signal S1, and R, , R, are resistors. .

Next, the operation of this embodiment will be explained.

The A/D converter 101 has a reference voltage (V, 1EF) and VI
The ratio with the DEO input is converted into an N-bit multi-value output. Normally, RAM 103 stores data when the amount of light received by the main body reading device is ioo%.
03 is converted into an analog voltage by the D/A converter 104, the element 201 is turned on by the switching signal S1, and the data stored in the A/D converter 101 is output from the D/A converter 104 as a reference voltage of the A/D converter 101. By using this analog voltage, the ratio between this reference voltage and the amount of light reflected from the original is outputted from the A/D converter 101 as multi-value data.

As described above, when a separate document conveyance drive device is used, a light amount loss occurs due to the paper storage board, so even if the document density is the same, there will be a difference in the ratio of the reflected light amount to the document. Therefore,
The transmittance of the paper storage board is set in advance by the resistor partial pressure of R3 and R2, the element 202 is made conductive by the switching signal S1, and the reference voltage of the A/D converter 101 is divided by the resistors R1 and R2. Input the applied voltage. In this way, by using a value that compensates for the amount of loss due to the paper storage board as the reference voltage of the reference voltage 101 of the A/D converter 101, the ratio of the amount of reflected light to the original is the same as that of the main device.
The same multi-value data as the multi-value data obtained by the main body reading device is obtained as multi-value data obtained by a separate document conveyance drive device.

Note that (1) the correction of the amount of light loss on the paper storage board can be equally performed even if the amount of light irradiated on the document is increased.

(2) Even if the A/D converter output is corrected based on the paper storage board transmittance, the same effect can be obtained.

[Effects of the Invention] As explained above, according to the present invention, density data is corrected to compensate for the amount of transmission loss of the paper storage board when a separately provided document transport drive device is used. The sameness can be obtained between the image reading density data and the image reading density data by the reading means in the main body, and uniform image quality can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a correction circuit diagram. 101...Analog-to-digital converter, 102...
Switch element, 103...Memory 104...Digital-to-analog converter, 105...
Correction circuit, 201.202... Analog switch, 203...
Inversion element. Diagram

Claims (1)

[Claims] In an image reading device capable of reading an image using an image reading means in the main body and reading an image using an original conveyance drive device, the image reading means in the main body can read the image, or the image reading means can read the image using the original conveyance drive device. The present invention is characterized by comprising a switching means for selecting either image reading using the switching means, and means for correcting only the image reading signal when the document conveyance drive device is used based on the selection result of the switching means. image reading device.