JPH08237444A - Adjustment method for image reader - Google Patents

Abstract

PURPOSE: To adjust the position of a projection lens of the image reader quickly at a low cost. CONSTITUTION: An adjustment chart 36 provided with white stripes representing an edge of an image pickup area respectively is set above a slit 21 formed above a carriage 20 via an adjustment jig 37. A fluorescent light 23 is used to light the adjustment chart 36 and a reflected made incident onto the carriage 20 from the slit 21 is projected to a CCD line sensor 26 via a reflection mirror 24 by a projection lens 25 and a waveform of its output signal is displayed on a screen 40a of an oscilloscope 40. When the projection lens 25 is moved in the optical axis direction, an image size of the adjustment chart 36 projected on the CCD line sensor 26 is changed and a waveform pattern on the screen 40a is changed. When a waveform pattern representing projection of an image of each stripe in white color onto a light receiving element placed at both ends of the CCD line sensor 26 is displayed on the screen 40a, the movement of the projection lens 25 is stopped to make positioning of it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adjusting method for an image reading device, and more particularly to an adjusting method for adjusting a mounting position of a projection lens in the image reading device.

[0002]

2. Description of the Related Art An image reading apparatus such as a facsimile for reading and transmitting an image (original image) such as characters and pictures recorded on an original, and an image scanner for inputting image data to a personal computer (personal computer) are widely popular. are doing. In such an image reading apparatus, a document is illuminated in the main scanning direction by a light source such as a fluorescent lamp, and the reflected light is focused on an image sensor such as a CCD line sensor via a mirror and a projection lens. The image sensor decomposes one line of the formed original image into pixel units, thereby sequentially reading pixels for one column in the main scanning direction. In the image scanner, the light source, the mirror, the projection lens, and the image sensor are an integrated unit (called a carriage), and the entire document can be read by moving the unit in the sub-scanning direction. In the facsimile, the light source, mirror, projection lens and image sensor are fixed,
The original is conveyed in the sub-scanning direction.

When assembling the image reading apparatus, it is necessary to individually finely adjust the positional relationship between the image sensor and the projection lens in order to accurately form the original image on the image sensor. As an adjustment method, for example, the image sensor is fixed at a predetermined position and the projection lens is movable in the optical axis direction. Then, an adjustment chart is placed at the image pickup position of the document, and the image signal output from the image sensor is displayed on the oscilloscope as an output signal waveform.
When the image of the chart is accurately focused on the image sensor, the rising edge of the waveform becomes sharp, so while checking the waveform displayed on the oscilloscope, the operator finds the peak at which the rising edge of this waveform becomes the sharpest, The projection lens is positioned.

[0004]

By the way, in the image reading apparatus, as the projection lens, for example, a wide-angle lens having a focal length of 20 mm is adopted. However, since such a wide-angle lens has a deep focal depth, the change in the waveform of the output signal from the image sensor becomes extremely gentle compared to the amount of movement in the optical axis direction, and it is difficult to find the rising peak of the waveform. Therefore, the adjustment work for optimally positioning the projection lens requires skill and takes time. In addition, even if such a troublesome adjustment work is performed, the projection lens has a slight variation in the focal length due to an assembly error at the time of manufacturing, variations in the optical glass, etc., and the imaging range is not constant. There is. To solve this problem, after positioning the projection lens, it is necessary to correct the position of the image sensor or change the focal length of the projection lens. There is a problem that the cost increases and the cost of the projection lens increases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an adjusting method for an image reading device, which can adjust the position of a projection lens quickly and at low cost.

[0006]

In order to achieve the above object, an adjusting method for an image reading apparatus according to claim 1 sets an adjusting chart displaying at least the maximum reading width in the main scanning direction, and performs the adjustment. The waveform of the output signal from the image sensor obtained by imaging the application chart is displayed on the screen of the oscilloscope, and while observing this, move the projection lens in the optical axis direction so that both ends of the maximum reading width are at both ends of the image sensor. The projection lens is positioned so that a waveform pattern indicating that each of the light-receiving elements is read is displayed on the screen of the oscilloscope.

According to a second aspect of the present invention, there is provided an image reading apparatus adjustment method according to the first aspect of the present invention.
In the adjustment chart, high-reflectance narrow high-reflectance regions are provided at positions corresponding to both ends of the maximum reading width, and low-reflectance low-reflectance is provided at positions sandwiching each high-reflectance region in the main scanning direction. Regions are provided respectively, and the projection lens is positioned so that the imaging waveform of each high reflection region appears at both ends of the waveform pattern displayed on the oscilloscope.

[0008]

Function: The projection lens is movable in the optical axis direction.
Instead of the document at the reading position, an adjustment chart displaying at least the maximum reading width in the main scanning direction is set, and the output signal waveform from the image sensor is displayed on the screen of the oscilloscope. When the projection lens is moved in the optical axis direction, the size of the image of the adjustment chart projected on the image sensor changes, so that the shape of the waveform pattern displayed on the screen of the oscilloscope changes. The operator moves the projection lens while observing this waveform pattern, and the waveform pattern indicating that the images at both ends of the maximum reading width displayed on the adjustment chart are projected on the light receiving elements located at both ends of the image sensor. When is displayed on the oscilloscope screen, the operation of moving the projection lens is stopped, and the position of the projection lens is specified. With such a simple adjustment method,
Even if there is an error in the focal length of the projection lens, the position of the projection lens can be accurately positioned without causing a shift in the imaging range.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 2 showing the appearance of a monochrome type image scanner 10 embodying the present invention, a main body 11 of the image scanner 10 is a box type, and a transparent original on which an original 12 is placed is placed in the center of the upper part. A glass plate (stage) 13 is fitted. Further, the lid 15 covering the upper portion of the main body portion 11 at the time of reading the original is provided with the hinge 16 so that the main body portion 1
It is rotatably attached to one end. Body 11
A carriage 20 for reading an original 12 placed on a glass plate 13 is provided inside the container so as to be movable back and forth in the sub-scanning direction, and when the reading of the original is started, a main body is driven by a drive mechanism provided in the main body 11. The part 11 is moved from one end to the other end. As the original 12, a reflective original in which an image such as a picture or a character is recorded on an opaque support such as paper or a transparent original such as a positive film can be used.
The back surface of the lid 15 (the surface on the original side) has a white finish for reading a transparent original.

In FIG. 1, a slit 21 extending in the main scanning direction is formed on the upper portion of the carriage 20. A fluorescent lamp 23 is provided in parallel with the slit 21 inside the carriage 20, and the fluorescent lamp 23 illuminates an original placed on a glass plate through the slit 21 when reading an original. There is. An elongated reflection mirror 24 is provided right below the slit 21 in the main scanning direction at an inclination angle of, for example, 45 ° with respect to the document surface, and a projection lens 25 and a CCD line sensor 26 known as an image sensor are provided in the horizontal direction. They are arranged in order. As the projection lens 25, for example, a wide-angle type having a focal length of 20 mm is used.

The CCD line sensor 26 is, for example, 500
Zero light receiving elements are arranged in a straight line in the main scanning direction, and a signal current generated according to the amount of light incident on each light receiving element is read in time series and output to the amplifier 27. The amplifier 27 amplifies this analog electric signal and sends it to the image signal processing circuit 28. The image signal processing circuit 28 is an amplifier 27.
After converting the analog electric signal amplified by (1) into a digital image signal, after performing processing such as shading correction, it is output to a thermal printer, a personal computer or the like via an interface 29 such as SCSI.

In FIG. 3, the projection lens 25 is held by a lens holder 30, which is mounted on a rail 31 fixed to the bottom of the carriage 20 and has an optical axis α.
It is attached so as to be movable in the direction (sub-scanning direction).
A rack gear 32 having a fine pitch is fixed to the side surface of the lens holder 30, and a pinion gear 33 meshes with the rack gear 32. The tip of the shaft 34 fixed to the pinion gear 33 has a hole 20a formed in the upper wall of the carriage 20.
It is projected to the outside of the carriage 20 via the, and a knob 35 is fixed to the tip thereof. The knob 35 can be operated by removing a part of the main body cover. By rotating the knob 35, the projection lens 25 is moved to the lens holder 30 via the shaft 34, the pinion gear 33, and the rack gear 32.
Can be moved in the optical axis α direction. Note that hole 2
It is preferable that the carriage 20 near 0a be provided with a lock mechanism that can fix the knob 35 at an arbitrary position.

The image scanner 1 configured as described above
When assembling 0, the position of the projection lens 25 in the optical axis direction is finely adjusted. First, the adjustment chart 36 is set above the slit 21 via the adjustment jig 37. The adjusting jig 37 is composed of an elongated glass plate 38 made of the same material as the glass plate 13 of the main body 11 and a spacer 39, and the glass plate 13 of the main body 11 with the carriage 20 accommodated in the main body 11. The same state as when the adjustment chart 36 is placed on is reproduced. Then, the oscilloscope 40 is connected to the interface 29.

As shown in FIG. 4, the adjustment chart 36 has an elongated shape, and the glass plate 38 of the adjustment jig 37 is used.
The surface 36a facing the surface has a white finish with high reflectance. The black stripes 42a, 43a and the stripes 42b, which have a low reflectance, are formed on both ends of the surface 36a.
43b are printed with a slight gap therebetween.
The surface 36a is exposed in each of the gaps and forms white stripes 44a and 44b. These center lines P
The distance L1 between a and Pb corresponds to the maximum reading width (designed imaging range) of the original in the main scanning direction.

When the light receiving width of the CCD line sensor 26 is, for example, 20 mm and the projection magnification of the projection lens 25 is, for example, 1/4, the distance L1 of the adjustment chart 36 is, for example, 80 m.
m. The distance L2 between the center lines Qa and Qb of the stripes 42a and 42b is, for example, 76 mm, and the reference lines Ra and Rb indicating the distances between the stripes 43a and 43b.
The distance L3 between them is 84 mm. In addition, this reference line Ra
The position of is determined such that the distance from the center line Pa is equal to the distance between the center lines Pa and Qa. The same applies to the position of the reference line Rb.

The fluorescent lamp 23 is turned on and the CCD line sensor 26 is driven to project the image of the adjustment chart 36 on the CCD line sensor 26 via the reflection mirror 24 and the projection lens 25. The output signal from the CCD line sensor 26 is amplified by an amplifier 27, then digitized by an image signal processing circuit 28, subjected to processing such as shading correction, etc.
Input to 0. On the screen 40a of the oscilloscope 40, the waveform patterns shown in FIGS. 5A to 5C are displayed depending on the position of the projection lens 25.

On the screen 40a of the oscilloscope 40, (A)
When the waveform pattern of is displayed, the projection lens 25
Is closer to the reflection mirror 24 side, and the image of the adjustment chart 36 is larger than a predetermined size. That is, since the images of the stripes 44a and 44b are projected outward from the light receiving elements located at both ends of the CCD line sensor 26, the knob 35 is operated to move the projection lens 25 toward the CCD line sensor 26 side. To move.

When the waveform pattern (C) is displayed, the image of the adjustment chart 36 is smaller than a predetermined size because the projection lens 25 is located near the CCD line sensor 26. That is, since the images of the stripes 43a and 43b outside the maximum reading width are projected on the light receiving elements located at both ends of the CCD line sensor 26, the knob 35 is operated to operate the projection lens 2.
5 is moved toward the reflection mirror 24 side to increase the size of the image of the adjustment chart 36 projected on the CCD line sensor 26.

When the waveform pattern shown in (B) is displayed on the screen 40a of the oscilloscope 40, the image of the adjustment chart 36 has a predetermined size, and CC
The centers of the images of the stripes 44a and 44b are overlapped on the light receiving elements located at both ends of the D line sensor 26. That is, since all the images of the maximum reading width to be read in the readable range of the CCD line sensor 26 are projected without excess or deficiency, the operation of the knob 35 is stopped and the position of the projection lens 25 is specified. At this time, if the focal length of the projection lens 25 is as designed, the original image is accurately formed on the CCD line sensor 26.
The optical path length from the slit 21 to the CCD line sensor 26 is determined.

Generally, the focal length of the projection lens 25 is
Since the processing error of the lens itself and the assembly error at the time of manufacturing are included, (B) is displayed on the screen 40a of the oscilloscope 40.
With the waveform pattern shown in FIG.
Even if the position is set to "1", theoretically, a shift occurs in the focus position where the document image is formed on the CCD line sensor 26. However, since the depth of focus of the projection lens 25 is sufficiently deep, the amount of deviation of the focus position falls within the allowable range, and there is no risk of inconvenience such as deterioration of reading accuracy.

Although the CCD line sensor in which the light receiving elements are arranged in one line is used as the image sensor in the embodiment described above, a CCD area sensor in which the light receiving elements are two-dimensionally arranged may be used. In this case, for example, a signal output from the light receiving element for one line in the center of the light receiving area is used. Further, as the adjustment chart, the one in which only the maximum reading width in the main scanning direction is displayed is used. However, for example, the one in which the maximum reading width in the sub-scanning direction is also displayed, that is, the adjustment chart displaying the entire reading range is used. Good. In addition, the transparent glass plate 1 is used without using the adjusting jig 37.
Alternatively, the chart 36 may be set on the table 3. In this case, for example, the side surface of the main body is openable, and the projection lens can be moved and fixed from the side of the main body.

Although the above embodiment is a monochrome type image scanner, it goes without saying that the present invention can be applied to a color type image scanner. The color image scanner is provided with, for example, three light sources of R, G, and B, and these lights are sequentially switched, or the light source is a white light source, and R, G, and B are provided between the projection lens and the image sensor.
There are a B color three-color filter that can be inserted and removed freely, and these can be switched sequentially, and a color image sensor of three colors can be used. To adjust the position of the projection lens with these color image scanners, one color, eg G
The light source or the filter of No. 1 may be used, or the position of the projection lens may be adjusted for two colors or three colors, and the projection lens may be fixed at the average position thereof. Further, only the embodiment in which the present invention is applied to the flatbed type image scanner has been described, but it goes without saying that the present invention can be applied to other image reading apparatuses such as a handy scanner and a facsimile.

[0023]

As described above, according to the adjusting method of the present invention, the adjustment chart displaying at least the maximum reading width in the main scanning direction is used, and both ends of the maximum reading width are located at both ends of the image sensor. The position of the projection lens is specified when the waveform pattern indicating that each element has been read is displayed on the screen of the oscilloscope, so even if the focal length of the projection lens varies, it can be imaged with simple adjustment work. The range can be exactly matched to the predetermined range.

Further, since it is only necessary to use a predetermined adjustment chart and there is no need to use an expensive projection lens whose focal length can be changed, the position of the projection lens can be adjusted quickly at low cost. Further, the high-reflecting areas indicating both ends of the imaging range are provided at both ends of the adjustment chart, and each high-reflecting area is sandwiched by two low-reflecting areas, and each high-reflecting area of the adjustment chart is imaged. Since the position of the projection lens is specified when both ends of the waveform pattern indicating the above are displayed on the oscilloscope, the position of the projection lens can be easily adjusted.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of a structure of a carriage of an image scanner embodying the present invention and a signal processing circuit of a CCD line sensor.

FIG. 2 is a perspective view showing an appearance of an image scanner.

FIG. 3 is an explanatory diagram showing an outline of a moving mechanism of a projection lens.

FIG. 4 is a plan view of an adjustment chart.

FIG. 5 is an explanatory diagram showing a waveform pattern displayed on an oscilloscope.

[Explanation of symbols]

 10 Image Scanner 12 Original 13 Glass Plate 20 Carriage 23 Fluorescent Lamp 24 Reflecting Mirror 25 Projection Lens 26 CCD Line Sensor 36 Adjustment Chart 40 Oscilloscope 42a, 42b, 43a, 43b Black Stripes 44a, 44b White Stripes

Claims (2)

[Claims] 1. An image sensor in which a large number of light receiving elements are arranged in a line in at least a main scanning direction, an illuminating means for illuminating an image recording surface of a document placed at a reading position, and the illuminating means and the image sensor. An adjusting method of an image reading device for adjusting a mounting position of a projection lens in an image reading device including a projection lens for reducing and projecting an image recorded on an original onto an image sensor while moving relative to the original in a sub-scanning direction In, in the reading position, set the adjustment chart displaying at least the maximum reading width in the main scanning direction, project the waveform of the output signal from the image sensor obtained by imaging this adjustment chart on the screen of the oscilloscope, The projection lens is moved in the direction of the optical axis while observing, and both ends of the maximum reading width are located at both ends of the image sensor. As a waveform pattern indicating that the read respectively by the child is displayed on the oscilloscope screen, the adjustment method for an image reading apparatus, characterized by positioning the projection lens. 2. The adjustment chart is such that narrow high-reflectance regions having high reflectance are provided at positions corresponding to both ends of the maximum reading width, and reflectances are provided at positions sandwiching each high-reflection region in the main scanning direction. Low reflection regions are respectively provided, and the projection lens is positioned so that the imaging waveform of each high reflection region appears at both ends of the waveform pattern projected on the oscilloscope. 1. The method for adjusting the image reading apparatus described in 1.