JPH0456564A - Original reader - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is a flat-bed type document reading device, which includes a flat document table and a carrier that runs along the flat document table. The present invention relates to a document reading device that is read by a reading unit mounted on a device, and is characterized by a focus adjustment means of the reading unit.

(Prior Art) FIG. 9 is a side view schematically showing a reading unit of a conventional flatbed document reading device using a Rondo lens as an imaging lens.

In the figure, 1 is an original table made of a transparent glass plate, 3 is a lamp for illuminating the original, 4 is a first reflecting mirror, 5 is an imaging lens, 6 is a second reflecting mirror, and 7 is a contact type one-dimensional image sensor. , 2 is a carrier on which these devices are mounted, and the carrier 2 reads the document 8 on the document table 1 while moving in the left-right direction in the figure.

(Problem to be Solved by the Invention) In order to accurately read the document 8 with the above-mentioned device,
It is necessary that the information on the original document 8 be accurately imaged on the light receiving surface of the image sensor 7. However, in reality, defocusing tends to occur due to deflection of the document table 1, deflection of the guide member that guides the carrier 2, or lifting of the document 8 from the document table 1, and this is a factor that impedes the clarity of the read information. It becomes. Also, when assembling the device, carrier 2
Adjusting the focus so that a clear image is formed on the image sensor 7 over the entire travel range of the vehicle is a difficult and time-consuming task. For example, when the document table 1 is A3 size, the document table 1 is deflected by 0.6 degrees, and it is necessary to adjust the parallelism of the guide of the carrier 2 so that the defocus caused by this deflection is corrected. It's difficult in reality. Furthermore, when the manuscript is a book, the closing edges of the manuscript stand out from the manuscript metalwork, making it impossible to clearly read that part of the manuscript.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a document reading device having a function of automatically adjusting the focus by measuring the deflection of the document table 1 and the lifting amount of the document 8. That is.

(Means for Solving the Problems) In the apparatus of the present invention, the carrier 2 is provided with slide stands 12a, 12b, 12C (
In the specification, 12 is used as a general term for these. ), and a positionable electric motor 13 for moving this slide base is provided. The slide table 12 is equipped with an imaging lens 5 (FIG. 1), an image sensor 7 (FIG. 3), or both an imaging lens and an image sensor (FIG. 2). The positionable electric motor 13 is, for example, a servo motor or a pulse motor.

This electric motor 13 is connected to the slide base 12 via a rank pinion 14, 15, a ball screw 18, a belt drive device, etc.
drive back and forth.

Furthermore, the apparatus of the present invention includes a non-contact length measuring device 130 that detects the distance between the carrier 2 and the reading surface of the document 8. Various devices using a laser beam are known as the non-contact length measuring bag W30. The illustrated embodiment includes a two-segment photodiode 38, a condensing lens 36, and a knife 37, and when the distance to the document surface changes, the two-segment photodiode 38 is Although this structure utilizes the change in output difference, other structures, such as those equipped with an imaging lens and a position sensor, can also be used.

The measurement position B of the length measuring device 30 is placed in front of the reading position A of the reading unit (in front of the traveling direction of the carrier 2 when reading the document), and the measurement value is stored in the 1
One or more memories 41 are provided.

Further, detection means for detecting the rotation angle of the electric motor 13 from its original position or the amount of movement of the slide table 12 from its original position, such as an encoder 20 or a magnetic scale 16, is provided.

When reading a document, the length measuring device 30 measures the distance to the document surface every time the carrier 2 moves a predetermined distance i, and each time the reading position A of the reading unit reaches the measuring position B of the length measuring device, the memory 41 and the current position of the slide table 12, and if there is a deviation between the two, control is performed to rotate the electric machine 3 by an amount corresponding to the deviation. The electric motor 13 moves the imaging lens 5 and the slider 12a closer to the first reflecting mirror 4 by Δ/2 when the document surface moves away by a distance Δ. In the case where both image sensors 7 are mounted on the slide stand 12b, the slide stand 12b is the first
In the case where the image sensor 7 is mounted on the slide table 12C so that the image sensor 7 is moved closer to the reflecting mirror 4 by Δ, the slide table 12c is moved away from the first reflecting mirror 4 by Δ, and the document surface is moved away from the first reflecting mirror 4 by Δ.
When the rotation direction and amount of rotation become closer to each other, the direction and amount of rotation are controlled in the opposite direction to the above. The measurement position B of the length measuring device is set close to the side of the document 8 in the document width direction, and printing of information on that part of the document is prohibited, so that the length measuring device 30 always measures the ground color part of the document 8. be able to do so.

(Function) According to the above configuration, the electric motor 13 is driven based on the distance of the document surface measured by the length measuring device 30, and the distance from the document surface to the imaging lens 5 is determined at each point where the measurement is performed. Since the distance from the imaging lens to the image sensor 7 is always adjusted to be equal, the deflection of the document table 1 and the distance from the document 8
The focus shift caused by the lifting of the image is corrected, and a clear image can always be formed on the light receiving surface of the image sensor 7. In a document reading device, it is not possible to align measurement position B with the reading position because it would interfere with reading, but in the device of the present invention, measurement position B is placed in front of document reading position A and the measured value is is memorized once, and when the reading position A reaches the measurement position B, the position of the imaging lens 5 and image sensor 7 is adjusted based on the memorized value, so that accurate focus can be achieved without interfering with reading the document. Matching becomes possible. Also, according to the above configuration,
Even if the document table 1 is bent or there is a slight error in the parallelism between the guide member of the carrier 2 and the document table 1, these will be automatically corrected and read, making it easy to assemble the device. This also simplifies the adjustment work.

(Embodiment) FIGS. 1 to 3 show the first embodiment of the focus adjustment mechanism of the present invention.
These are diagrams showing embodiments to third embodiments, in which the first embodiment has a structure in which the imaging lens 5 is moved, and the second embodiment has a structure in which the imaging lens 5 is moved.
The third embodiment has a structure in which the image sensor 7 and the image sensor 7 are moved together.

In the figure, 1 is a document table, 2 is a carrier, 3 is a lamp for illuminating the document, 4 is a first reflecting mirror, and 5 is a rod lens (imaging lens)
, 6 is a second reflecting mirror, 7 is a one-dimensional image sensor,
These members themselves are no different from those of conventional devices.

11 is a rail provided on the carrier 2 in the direction of the optical axis of the reading light; 12 (12a, 12b, and 12C) is a slide base that is slidable on the rail 11; and 13 is an electric motor mounted on the carrier 2. 14 in Figure 1.2 is the electric motor 13
pinion fixed to the output shaft, 15 is the slide base 12
a, a rack fixed to 12b and meshed with the binion 14, 16 a magnetic scale attached to the carrier 2, 1
7 is a magnetic sensor fixed to the slider (F stands 12a, 12b), 18 in FIG. The ball nut 20 is an encoder (slit disc) that detects the rotation angle of the ball screw 18.

21 is a magnetic sensor 17 at the origin position of the slide table 12;
Alternatively, it is a counter that counts the output pulses of the encoder 2o, and in the ones shown in FIGS. 1 and 2, the direction in which the slide tables 12a and 12b are moved to the left in the figure is the forward rotation of the electric motor 13, and in the ones shown in FIGS. In this case, the direction in which the slide table 12c is moved to the right in the figure is the forward rotation of the electric motor 13.

FIG. 4 shows an embodiment of the length measuring device of the present invention. This length measuring device is attached to the side of the carrier 2 (the end in the direction perpendicular to the plane of the drawing).

In FIG. 4, 31 is a semiconductor laser oscillator, 32 is a reflecting mirror,
33 is a beam splitter (half mirror), 34 is 1/
4 wavelength plate, 35 is an objective lens, 36 is a condensing lens, 37
is a knife placed at the focal point of the condensing lens 36,
38 is a two-part photodiode.

A laser beam M emitted from a laser transmitter 31 is directed in a direction perpendicular to the original 8 by a reflecting mirror 32 and is irradiated onto the original 8 through a beam splitter 33 and a quarter-wave plate . The reflected light diffused on the surface of the original 8 is converted into parallel light by the objective lens 35, passes through the 1/4 wavelength plate 34, is reflected by the beam subrifter 33, is once converged by the condensing lens 36, and then is converted into parallel light by the objective lens 35. The light is incident on the split photodiode 38.

When the document 8 moves away from its normal position, the focal point P of the condenser lens 36 shifts to the left as shown in FIG.
The light incident on the diode 38b below the 8 is blocked, and the output that passes through the differential amplifier 39 is biased to the + side. On the other hand, manuscript 8
is closer than the normal position, the condenser lens 36
The focal point P of the differential amplifier 39 shifts to the right as shown in FIG. bias to the side.

The output of the differential amplifier 39 is converted into a digital signal by the AD converter 40 and stored in the first memory 41 .

Next, with reference to the flowcharts of FIGS. 7 and 8, the adjustment work at the time of shipment and the control operation at the time of document reading will be described.

In FIG. 7 showing a flowchart during adjustment work, the reference raster means a reading line for setting the output of the differential amplifier 39 and the reference value of the slide table 12, and is set at an arbitrary position close to the home position of the carrier 2. be done. Then, a document having a striped pattern in the reading direction of the image sensor 7 is prepared, and the document is brought into close contact with the position of the reference raster.

Next, the carrier is moved and stopped so that the measurement position B is aligned with the reference raster, and the output V of the differential amplifier 39 is measured. is stored in non-volatile memory as a reference value. Next, the carrier 2 is moved by a pulse to align the reading position A with the reference raster and read the document. And the output of the image sensor 7 is
Inter-nod amplitude m.

is detected and temporarily stored. Next, the electric motor 13 is driven to move the slide table 12 by one unit in either direction, and the document is read at that position, and the inter-bit amplitude m of the output of the image sensor 7 at this time is detected. If the value of the amplitude m at this time is larger than the stored amplitude m0, m is
o, the slide table 12 is moved one unit in the same direction as the previous time, and the detection of the amplitude m and the comparison and replacement with the stored value m0 are repeated (steps 51 to 53). Then, when the detected amplitude value m becomes smaller than the stored value m0, the slide table drive motor 3 is switched to reverse rotation. After repeating the loop from steps 51 to 53 described above, the determination of the step knob 56 in the next loop from step knobs 54 to 56 will be No, so from the origin position of the slide base 12 at this time The amount of movement h0 is stored in the nonvolatile memory as a reference value, and the adjustment work is completed.

FIG. 8 is a flowchart showing control when reading a document. In this flowchart, the carrier 2 has moved 10 pulses from the home position (the first measurement is taken at the i position, and thereafter a measurement is made every i pulse movement, and each time the reading position II person reaches the measurement position, the slide In the figure showing the position adjustment of the table 12, n is the number of the measurement position starting with 0, and k is a variable indicating the difference in number between the measurement position and the reading position.

During a read operation, first initialize n and k,
The amplifier output Vn (n=1) is detected at the first measurement position where the carrier 2 moves by i pulse, and the position Hh of the slide table 12 to be set is calculated.

In the formula of step 61, ho and ■. is a value stored in the nonvolatile memory during the setting work shown in FIG. 7, and α is a coefficient determined in advance by calculation or experiment. And the calculated location information. is stored in the memory area at address n.

Then, when the carrier 2 continues to move and the amount of movement reaches the number of pulses indicated by the formula in step 62, it is the time when the reading position A has reached the n-th measurement position.
At this time, the stored value h1-k is stored from address n- in the memory area.
The value of l is called in and the slide table 12 is moved to that position. Then, 1 is decremented from the value of k, that is, the address at which the position of the slide table 12 is to be adjusted next is incremented by one. Step 63 is a determination as to whether the carrier 12 has reached a certain measurement position.

If it has been reached, add 1 to each of the values of n and k, that is, advance the measurement position number by 1, increase the difference between the measurement position number and the correction position number by 1, and increase the amplifier output Vn. Detection and calculation and storage of the set position h7 of the slide table are performed. If the carrier has not moved to the position defined in step 61 or 62, the carrier continues to move until it reaches the position. The processing according to this flowchart ends when the reading end signal is received as an interrupt signal.

(Effects of the Invention) According to the apparatus of the present invention described above, the focus of the reading light on the image sensor is adjusted while measuring the distance between the carrier and the document surface one by one when reading the document. Focus shifts caused by errors during assembly or lifting of the document from the document table are corrected, allowing clear reading of the entire document, and making adjustments at the time of device shipment extremely easy. Then, when reading a document, the carrier is moved and the surface of the document is measured in front of the reading position, and the focus is adjusted when the reading position reaches the measurement position, so there is no interference with the optical path of the reading light. The length measuring device can be installed without any problems, the reading of one raster and the position measurement of the raster beyond it are done in parallel, and there is no need to stop the reading operation when adjusting the focus, which reduces the time required for focus adjustment. This has the effect of minimizing time.

[Brief explanation of drawings]

1 to 8 are diagrams showing embodiments of the present invention. FIG. 1 shows the first embodiment of the focus adjustment mechanism, FIG. 2 shows the second embodiment, and FIG. 3 shows the third embodiment of the focus adjustment mechanism. Figures illustrating each example, No. 4
5 and 6 are explanatory diagrams of the operation of the length measuring device shown in FIG. 4. FIG. 7 is a flowchart showing the adjustment work at the time of shipment of the device. The figure is a diagram showing a control flowchart during a reading operation. FIG. 9 is a simple side view showing a conventional image reading unit. In the figure, 1: Original table 2: Carrier 5: Rondo lens 7: Image sensor 8: Original
11: Rails 12a, 12b, 12c Nislide stand 13: Motivator 16: Magnetic scale 20: Encoder 30: Length measuring device 36: Condensing lens 38: 2-split type filter No. 39: Differential amplifier 31: Laser oscillator 37: Naifetsu diode 41: Memory Figure 8

Claims (1)

[Claims] A flat document table (1) and a carrier (2) running along the document table are provided, and an imaging lens (5) and an image sensor (7) are mounted on the carrier (2). In the document reading device, a carrier (2) is provided with a slide table (12) that is movable in the optical axis direction of the reading light (L), and an imaging lens (5) and/or an image sensor (7) is mounted on the slide table. is equipped with a positionable electric motor (13) for moving the slide table and a detection means (13) for detecting the amount of movement thereof.
16, 20), and the carrier (2) is equipped with a non-contact length measuring device (30) for measuring the distance to the original (8).
The measuring position (B) of the length measuring device is placed in front of the reading position (A) of the reading unit in the traveling direction of the carrier (2) when reading the document, and one piece is installed to store the measured value. Alternatively, a plurality of memories (41) are provided, and when the document is read, the length measuring device (30) measures the distance to the document surface and the measured value is stored in the memory (41).
), and when the reading position (A) of the reading unit reaches its measurement position (B), the slide table (12)
A document reading device characterized in that the position of the document is adjusted by referring to the contents of a memory (41).