JPH02174362A - Scanner - Google Patents

Abstract

PURPOSE:To always read a sharp picture by switching the read mode into at least two kinds of the read mode with deep focus and low speed or the read mode with a shallow focus and high speed. CONSTITUTION:When a command selecting whether the read mode 1 with deep focus and low speed or the read mode 2 with shallow focus and high speed is received from an external device or a host device connecting to the scanner, the CPU of the scanner uses a solenoid 18 to drive an aperture blade 16 in a lens unit 15 via a lever 17 accordingly in a direction of stopping the blade in the case of the mode 1 and in the direction of opening the blade in the case of the mode 2 and switches the read timing accordingly. Thus, a picture with sharp focus is obtained even from a stereoscopic object and it is possible to read the picture not out of focus at a high speed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention sets a sheet original or a thick book original at a predetermined position on a target glass, and uses a one-dimensional line sensor for main scanning and a census sensor for sub-scanning. The present invention relates to a scanner device used in, for example, a copying machine, in which an optical system is moved mechanically.

(Conventional technology) An example of this type of scanner device is shown in FIG.

Reference numeral 1 denotes a target glass, 2 a thick book document set thereon to be read, and 3 a third device equipped with a lamp 4 that illuminates the document surface and a mirror 5 that receives reflected light from the document surface and changes the optical path. 1 a running body; 6 a second running body equipped with mirrors 7 and 8 that receive light from the first running body 3 and further change the optical path; 9 an imaging lens; 10 a CCD line sensor; 11 a control board. It is.

In such a configuration, the first traveling body 3 scans two sides of the document while moving from the position shown by the solid line to the position shown by the broken line, and at the same time, the second traveling body 6 also moves from the position shown by the solid line to the position shown by the broken line. Then, the reflected light from the original is incident on the imaging lens 9. Note that the moving distance (moving speed) of the second traveling body 6
is 1/2 of the moving distance fi (moving speed) of the first traveling body 3,
The optical path length of the reflected light is always constant. The lens 9 forms a light image on the CCD line sensor 10,
The CCD line sensor 10 performs photoelectric conversion and reads the image. The scanning of the document surface by the movement of the optical system is referred to as sub-scanning, and the CCD line sensor 10 performs main scanning in a direction perpendicular to the sub-scanning direction.

(Problems to be Solved by the Invention) By the way, when reading a thick book original as shown in FIG.

Therefore, as shown in FIG. 4, the portions (a, b) corresponding to the raised portions in the read image.

C) is likely to be blurred. This is particularly noticeable in sheet document feed type scanner devices used in facsimiles and the like.

Therefore, in order to prevent the document from becoming out of focus even if the document surface is a little far from the target glass, it is best to use a lens system with a deep depth of focus. This has the disadvantage that it requires a lot of time and therefore high-speed reading is not possible. Conversely, if the lens is made brighter, high-speed reading becomes possible for the opposite reason, but the depth of focus becomes shallower, making it difficult to clearly read the central part of a book document or the raised part of a three-dimensional object.

Deterioration of the scanned image due to the lifting of the original as described above (
In order to eliminate blur (blur), it is desirable to design a design with as deep a depth of focus as possible, and for that purpose, it is necessary to use a lens with a long focal length or a lens with a large F number, but the former In the latter case, the overall optical path length is increased, which increases the size of the device, and in the latter case, the illuminance of the light-receiving surface decreases, making it impossible to increase the reading speed. The reality is that the design involves finding a compromise between contradictory characteristics.

The present invention solves the above-mentioned problems, and provides a scanner device that changes the depth of focus as necessary to always read clear images.

(Means for Solving the Problems) The scanner device of the present invention is equipped with an aperture switching means for changing the F number of a lens in an optical system and a sub-scanning speed switching means, and the reading mode is set to ■ Deep depth of focus and low speed reading. It is possible to switch between at least two types: (1) shallow depth of focus and high speed reading mode;

(Function) When reading thick book manuscripts or three-dimensional objects, select depth of focus priority and set ■deep depth of focus and low speed reading mode. In addition, in the case of a sheet original, select the reading speed priority and switch to the shallow depth of focus and high speed reading mode.

Generally, the depth of focus Δ on the object side of a lens system is given by the following equation.

Δ=ρ・FNO(1+m)/m”-11) Also,
F=f/D (2). Here, ρ; Diameter of the circle of confusion FNO: Lens F number m: Magnification f: Focal length D: Effective aperture Therefore, if the effective pupil diameter is reduced by the lens aperture, the focal length f is constant, so the lens The number increases. On the other hand, according to equation (1), the number and the depth of focus Δ are proportional, so the effective pupil diameter and the depth of focus due to the diaphragm are inversely proportional.

Further, the illuminance E of the image is expressed as below.

Here, B: Brightness of the object: Transmittance of the lens (2) From equation (3), the brightness of the image is proportional to the square of the effective aperture of the lens aperture.

Therefore, EkaD2...(
4) Therefore, if the depth of focus is doubled, the field of view is reduced to 1/4, so if the same sensitivity is to be obtained, the reading speed must also be reduced to 1/4.

(Example) Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 1 shows an aperture switching mechanism of a lens according to an embodiment of the present invention. 15 is a lens unit 1-, which is provided with aperture blades 16 therein. This aperture blade 16
The aperture value can be changed by moving a lever 17 led out to the outside.

18 is a solenoid for switching the aperture.

Therefore, when reading a thick book original or a three-dimensional object, the aperture blades 16 are narrowed down to increase the F-number because the original tends to lift off the target glass. at the same time,
When the aperture blades 16 are narrowed down, the amount of light reaching the sensor surface decreases, so the sub-scanning speed is slowed down. On the other hand, when reading a sheet document, the aperture of the diaphragm is made large and the F number is made small because the document does not lift up. At the same time, since the amount of light reaching the sensor surface is large, the sub-scanning speed is increased.

FIG. 2 shows the control circuit configuration in one embodiment. When receiving a command to select either ■deep depth of focus and low speed reading mode or ■shallow depth of focus and high speed reading mode from an external device or host connected to the scanner device, the scanner side CPU: Accordingly, the aperture blades 16 in the lens unit 15 are driven by the solenoid 18 via the lever 17, and the mode is switched to the direction of closing the aperture if the mode is ■, and to the direction of opening the aperture if the mode is the mode ■. Along with this, the reading timing is also changed.

That is, in the case of mode (3), the motor control circuit is set so that the CCD integration time is long, and the sub-scanning feed speed is set to the low speed mode side. Since the mode setting is completed in the third mode, actual reading is performed next.If the mode is set to ■, the reading progresses slowly, but a sharply focused image can be obtained even for three-dimensional objects. In mode ■! Since this is selected when lifting of the J original, such as the original to Sheet 1 of 11--, does not occur, this also makes it possible to read an image without blurring at high speed.

The present invention can have several applications using the basic IJJ exchange configuration described above. Examples of its application will be shown below.

First, as shown in FIG.
A switch 22 that is linked to the opening and closing of the switch 1 is provided, and the opening and closing of the switch 22 is detected by a control CPU. That is, as shown in FIG. 5(a),
When a thick book original or three-dimensional object is set and the pressure plate cannot be closed, the switch 22 will not operate, causing
Deep depth of focus and slow scanning mode are automatically selected,
Further, as shown in FIG. 5(b), in the case of a sheet original, when the pressure plate 21 is closed, a switch is activated, whereby the shallow depth of focus and high speed reading mode (1) is automatically selected.

FIG. 6 shows a scanner device equipped with an automatic sheet document feeder (ADF) 25. When the ADF 25 is used, lifting does not occur because it is a sheet document, and high-speed reading is required. Therefore, ■Shallow depth of focus and high speed scanning mode will be automatically selected, and since the ADF will not be used for thick book manuscripts, ■Low depth of focus and low speed scanning mode will be automatically selected. Make it.

(Effects of the Invention) As explained above, according to the present invention, the reading mode can be set depending on whether the original to be read is thick like a book original or a sheet original. It is possible to switch between at least two modes: shallow depth of focus and high-speed reading mode, and it is possible to always read clear images, and high-speed reading is possible for sheet originals, making it highly cost-effective. It has the advantage that it can be used as a scanner device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a lens aperture switching mechanism according to an embodiment of the present invention, FIG. 2 is a block diagram of a control circuit in the same embodiment, and FIG. 3 is a diagram of a general reduction optical system scanner device. 4 is a diagram showing the occurrence of blurring when reading a thick book original; FIG. 5 is a diagram of the configuration of an applied example of the present invention;
FIG. 6 is a diagram showing another applied embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Target glass, 3... First traveling body, 6... Second traveling body, 9... Imaging lens,
10... CCD line sensor, 15... Lens unit, 16... Aperture blade, 17... Lever 1
8... Solenoid, 21... Pressure plate, 22... Switch, 25... ADF. Patent applicant Ricoh Co., Ltd.

Claims (3)

[Claims] (1) In a scanner device in which a sheet original or a book original is set in a predetermined position, main scanning is performed by a one-dimensional line sensor, and sub-scanning is performed by mechanically moving the sensor or optical system, in the optical system: It is equipped with an aperture switching means for changing the F-number of the lens and a sub-scanning speed switching means, and has at least two types of reading modes: [1] deep depth of focus and low speed reading mode, and [2] shallow depth of focus and high speed reading mode. A scanner device characterized by being able to switch to. (2) The scanner device according to claim (1), further comprising: means for detecting opening/closing of the document pressure plate; and a signal from the detection means, when reading is started with the document pressure plate open, a deep focal depth and a A scanner device comprising means for automatically setting a low-speed reading mode to a shallow depth of focus and a high-speed reading mode when reading is started with the document pressure plate closed. (3) The scanner device according to claim (1), comprising an automatic sheet document feeder, and starts reading by setting the document directly on the target glass without using the automatic sheet document feeder. A scanner device characterized in that it is provided with means for automatically setting a deep depth of focus and a low speed reading mode when reading is started using the sheet document automatic feeder, and a means for automatically setting a shallow depth of focus and a high speed reading mode when reading is started using the automatic sheet document feeder. .