JPH04170851A - Picture reader - Google Patents

Abstract

PURPOSE:To finely adjust light quantity in a wide range by providing a light quantity coarse adjustment means which switches light quantity stepwise and a light quantity fine adjustment means which steplessly adjusts read scan speed and/or light quantity within a prescribed range. CONSTITUTION:A mechanism part controller 12 suitably adjusts a distance La between an original 3 and an image pickup lens 8 and a distance Lb between the image pickup lens 8 and a linear image sensor 9 in correspondence with a previously set projection scale factor. Light quantity received by the linear image sensor 9 changes and at the same time, an ND filter 7 adjusts and controls a transmission rate. Then, light quantity for the linear image sensor 9 is stepwise switched and controlled. Thus, light quantity can finely be adjusted within the wide range.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to an optical line sensor (for example, an image sensor) at a predetermined projection magnification after irradiating light from a light source onto a document.
The present invention relates to an image reading device that performs reading scanning by forming an image of the document on the optical line sensor.

[Prior art]

Conventionally, as this type of image reading device, 1, for example, Japanese Patent Application Laid-Open No.
-100564 (first conventional device) and JP-A-2-
A device disclosed in Japanese Patent No. 65367 (second conventional device) is known.

The first conventional device is equipped with a set of ND filters of a plurality of types in order to adjust the amount of light from the document to the optical line sensor. Above N
The D filters are configured so that their transmittances change, for example, in 10% increments, and a desired transmittance is obtained by combining ND filters with different transmittances, and the amount of light directed to the optical line sensor is adjusted as appropriate. It is configured as follows.

In the second conventional device, for example, in order to adjust the amount of light to the optical line sensor according to the projection magnification of the original, the reading scanning speed of the optical line sensor and the amount of illumination light to the original are controlled. It is configured as follows.

[R1 to be solved by the invention] However, in the first conventional device described above, the amount of adjustment of the light amount can only be set in a 10% pinch by switching the ND filter, and the amount of light can be adjusted at even finer pitches. If this were to be done, the number of filters would be enormous, making the optical system larger.

There is a problem in that it leads to an increase in costs.

Furthermore, in the second conventional device, the amount of light received by the optical line sensor changes by a factor of about 3 depending on the change in magnification. , it is not possible to respond to the above-mentioned changes in light intensity, and when controlling the reading scanning speed in an optical line sensor, the image processing time changes significantly depending on the change in magnification (in this case, it becomes up to 3 times slower), It cannot meet the needs for high-speed processing.

Therefore, the purpose of the present invention is to increase the size of the device,
An object of the present invention is to provide an image reading device having a function of finely adjusting light quantity within a wide range without increasing cost or significantly changing two-image processing time.

[Means to solve the problem]

In order to achieve the above object, the main means adopted by the present invention is to irradiate light from a light source onto an original and then make it incident on an optical line sensor at a predetermined projection magnification. An image reading device that performs reading scanning by forming an image of the original on the optical line sensor, comprising: a coarse light amount adjustment means that roughly adjusts the amount of light incident on the optical line sensor by switching in stages, and the optical line sensor. a light amount fine adjustment means for steplessly adjusting the reading scanning speed of the document and/or the light amount of the light source that irradiates light toward the document within a predetermined range, the light amount coarse adjustment means according to a predetermined projection magnification; and/or a light amount control means for controlling the amount of light incident on the optical line sensor to a predetermined value by appropriately operating the light amount fine adjustment means.

[Effect]

In the image reading device according to the present invention, first of all.

The amount of light incident on the optical line sensor is switched in stages by a light amount rough adjustment means (for example, an ND filter made by combining a plurality of filters with different transmittances).

Thereafter, the reading scanning speed of the optical line sensor and the light intensity of the light source are steplessly adjusted to appropriate values within a relatively narrow range.

As a result, the amount of light incident on the optical line sensor is set to a predetermined value according to the predetermined projection magnification.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.

The following examples are examples embodying the present invention, and are not intended to limit the technical scope of the present invention.

Here, FIG. 1 is a schematic configuration diagram of an image reading device according to an embodiment of the present invention.

In the image reading apparatus 1 according to this embodiment, a document 3 placed on a document table 2 is illuminated by light from a light source unit 4, as shown in FIG. When the document 3 is a transparent document, the light source 41 for transmission disposed below the document table 2 in the light source unit 4 is turned on, and the document 3 is a transparent document.
When X3 is a reflective original, a reflective light source 4. .

45 is lit.

The light source 4 in the light source unit 4. ．． 4. teeth.

Based on a control command signal from the host CPU 5, the illumination light source controller 6 adjusts the amount of light steplessly within a relatively narrow predetermined range.

On the side facing the surface of the original 3 on the original platen 2.

A variable magnification projection optical system 10 comprising an ND filter 7, an imaging lens 8, a linear image sensor 9, etc. is provided.

The light from the original 3 illuminated by the light source unit 4 passes through the ND filter 7 and the imaging lens 8, and is imaged on the linear image sensor 9, and the linear image sensor 9 scans and reads the light. It will be done. The reading scanning speed of the linear image sensor 9 is variably controlled by an image sensor controller 11 according to the amount of light incident on the linear image sensor 9, for example.

In this case, based on the command signal from the host CPU 5, the projection magnification is set to a predetermined projection magnification m.
Distance ji between the document surface of the document 3 and the imaging lens 8
lL, and a distance 11L between the imaging lens 8 and the linear image sensor 9, as appropriate.
The adjustment is controlled by 2. As the projection magnification changes in this way, the amount of light received by the linear image sensor 9 changes. However, in the device of this embodiment, for example, if the variable range of the projection magnification is set to m = 0.2 to 1, Original surface illuminance E0. The relationship between the image resolution E and the projection magnification m is expressed by the following equation.

Ep/Eooct/(1+m)” −・・■Here,
When the original surface illuminance E0 is constant, the projection magnification m is 0.2
When changing within the range of ~1, the image plane illuminance E changes by about 3 times (°, 'l/(1+0.2)'':
1/(1+1)”=0.770.25 =3:1
).

Therefore, in the apparatus of this embodiment, in order to vary the amount of light incident on the linear image sensor 9 within the variable range of the projection magnification, the ND filter 7 has a transmittance of, for example, 25% or 50%. .

It is constructed by combining filters of 75% and 100% (corresponding to no fill).

Then, by appropriately rearranging and controlling the ND filter 7, the amount of light incident on the linear image sensor 9 is switched stepwise and coarsely adjusted.

In the image reading device 1 configured as described above, the mechanical unit controller 12
Accordingly, the distance 11 [L between the original 3 and the imaging lens 8 and the distance between the imaging lens 8 and the linear image sensor 9 are adjusted as appropriate. At the same time, the linear image sensor 9
ND so that the amount of light incident on the
The filter 7 is adjusted and controlled, and the amount of light to the linear image sensor 9 is controlled to be switched in stages.

Here, the image plane illuminance E is 25~25 by the ND filter.
It changes stepwise (dimming) within the 100% range, but
In order to maximize the dynamic range of the output from the linear image sensor 9, it is necessary to finely adjust the amount of light to a value equal to the output voltage level of the linear image sensor 9 at saturation exposure. Therefore, in the device of this embodiment.

The illumination light source controller 6 adjusts the amount of light from the light source unit 4, and simultaneously or independently, the image sensor controller 11 adjusts the reading scanning speed of the linear image sensor 9. The amount of light emitted is controlled to a predetermined value.

Therefore, according to the device of this embodiment, the configuration of the ND filter is simpler than that of the conventional device, and it is possible to downsize and reduce the cost of the entire optical system. Further, the control range of the reading scanning speed in the linear image sensor 9 or the illumination light amount in the light source unit 7 4 is narrowed, and the light amount of the fluorescent lamp can be controlled by using an inverter or the like.

Since the control range of the reading scanning speed by the linear image sensor 9 is narrowed as described above, the range of change in the image processing time of the entire apparatus can be reduced.

〔Effect of the invention〕

As described above, in the present invention, after light from a light source is irradiated onto a document, it is made incident on an optical line scanner at a predetermined projection magnification, and an image of the document is formed on the optical line sensor to perform reading and scanning. The image reading apparatus includes: a light amount rough adjustment means for coarsely adjusting the amount of light incident on the optical line sensor by switching in stages; a light amount fine adjustment means for steplessly adjusting the light amount of the light source that irradiates the light within a predetermined range;
Since the image reading device is characterized by comprising a light amount control means for controlling the amount of light incident on the optical line sensor to a predetermined value, it may lead to an increase in the size and cost of the device, or Fine light intensity adjustments can be made within a wide range without significantly changing image processing time.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an erroneous image reading device according to an embodiment of the present invention. [Explanation of symbols] 1... Image reading device 3... Document 4... Light source unit 4, . 4. ...Light source 5...Host CPU 6...Illumination light source controller 7...ND filter 8...Imaging lens 9...Linear image sensor 10...Variable magnification projection optical system 11...・Image sensor controller 12... Mechanism controller

Claims (1)

[Claims] 1. After irradiating the original with light from a light source, it is incident on an optical line sensor at a predetermined projection magnification, and an image of the original is formed on the optical line sensor to perform reading scanning. In the image reading device, a light amount coarse adjustment means for coarsely adjusting the amount of light incident on the optical line sensor by switching in stages; and irradiating light toward the reading scanning speed of the optical line sensor and/or the document. a light amount fine adjustment means for steplessly adjusting the light amount of the light source within a predetermined range; and a light amount coarse adjustment means and/or the light amount fine adjustment means suitably operated according to a predetermined projection magnification, and the optical line sensor 1. An image reading device comprising: a light amount control means for controlling the amount of light incident on the image reading device to a predetermined value.