JP2002312716A - Optical reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized optical reader capable of highly accurately reading fine images. SOLUTION: The optical reader is provided with a surface light emission laser array 2 emitting light, an optical system 4 converging emitted laser beams, a photodetector 8 detecting a reflected light quantity from a medium 12, a signal processing part 10 processing signals from the photodetector 8 and obtaining image information, a rotary mirror 5 changing the reflection angle of the laser beam in synchronism with the light emission timing of the laser array 2 so as to make the reflected laser beam scan the medium 12 in a scanning direction D crossing the array direction of laser elements by rotating about a rotary axis parallel to the array direction of the laser elements while reflecting the laser beam passed through the optical system 4, a motor 6 rotating the rotary mirror 5 in the direction of an arrow A, a motor driving circuit 7 driving the motor 6 and a controller 9 synchronizing the motor driving circuit 7 and a driver circuit 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical reader for optically reading an image formed on a medium.

[0002]

2. Description of the Related Art Conventionally, a laser scan type reader or a two-dimensional sensor has been used as a device for reading an image consisting of a fine optical pattern such as a bar code or a two-dimensional symbol printed on a medium by encoding digital information. A type reader is used.

A laser scanning type reader includes a laser light source, a lens for condensing laser light emitted from the laser light source, a folding mirror, a reciprocating vibration mirror or a polygon for scanning the laser light reflected by the folding mirror in a fixed direction. A mirror, a light receiving sensor, and the like are provided, and the laser light emitted from the laser light source is scanned over a bar code bar or a two-dimensional symbol cell by a reciprocating oscillating mirror or a polygon mirror, and the reflected light amount light receiving sensor is used. By detecting and processing a change in the amount of light with respect to the scanning position on the bar or the cell, information of one line scanned on the code is read. Further, it is also possible to read a two-dimensional symbol by moving the reading device body in a direction intersecting the scanning direction of the laser beam by the rotating mirror.

On the other hand, as a two-dimensional sensor type reader, for example, JP-A-6-139382 discloses a two-dimensional sensor in which photoelectric elements are arranged in a matrix to read a two-dimensional symbol such as a multi-stage code or a matrix code. Imaging means for imaging a two-dimensional symbol on the two-dimensional sensor; and two-dimensional imaging in the element array direction of the two-dimensional sensor based on the inclination of the two-dimensional symbol imaged with respect to the element array direction of the two-dimensional sensor. A two-dimensional sensor type reader having a direction correcting means for matching the directions of symbols is disclosed. In this two-dimensional sensor type reader, light is emitted from the light source to the entire two-dimensional symbol, and an image of the two-dimensional symbol is formed on the two-dimensional sensor through the imaging lens.
The two-dimensional symbol is read by processing the imaging pattern.

[0005]

In general, a laser scanning type reader uses a laser beam, so that the optical system has a large depth of focus and is advantageous in reading a fine code as compared with a two-dimensional sensor type reader. It is. However, in order to read a two-dimensional symbol with a laser scanning reader, the scanning direction or scanning range of the laser beam is moved so that the reading device main body coincides with the direction or range of the two-dimensional symbol, or a two-dimensional symbol is read. However, there is a problem that it is necessary to move the medium on which is printed, the mechanism tends to be complicated, and it is difficult to obtain high reading accuracy.

On the other hand, the two-dimensional sensor type reader has a large degree of freedom in the reading direction, but the depth of focus of the optical system is shallower than that of the laser scan type reader. There is a problem that it is easy to increase the size and increase the cost.

In view of the above circumstances, it is an object of the present invention to provide a small optical reader capable of reading a fine image with high accuracy.

[0008]

According to the present invention, there is provided an optical reading apparatus comprising: a light source for irradiating a predetermined medium with light; and an optical system for condensing light emitted from the light source on the medium. A light detector that receives reflected light from the medium irradiated with light and converts the amount of reflected light into an electric signal, and a signal processing unit that processes the electric signal from the light detector to obtain image information Wherein the light source is a light emitting element array composed of a plurality of light emitting elements arranged in a predetermined direction and sequentially emitting light in a predetermined order, and disposed between the optical system and the medium. By rotating around a rotation axis parallel to the arrangement direction of the light emitting elements while reflecting the light passing through the optical system, the reflected light crosses the medium on the medium in the direction intersecting with the arrangement direction of the light emitting elements. As you scan In synchronization with the emission timing of the light emitting element array is characterized in that a rotating mirror for changing the reflection angle.

[0009] Here, the optical reading device is configured to maintain the optical path length from the optical system to the medium constant irrespective of a change in the reflection angle due to the rotation of the rotating mirror. It is preferable to provide a rotating mirror reciprocating device that reciprocates the rotating shaft along the optical axis from the optical system to the rotating mirror.

When the light emitted from the light emitting element located at the center of the light emitting element array and reflected by the rotating mirror irradiates the medium vertically, the rotating mirror reciprocating device causes the optical system to rotate the light from the optical system. In a preferred embodiment, the rotating shaft is reciprocated so that the distance to the rotating shaft is maximized.

[0011]

Embodiments of the present invention will be described below.

FIG. 1 shows a first embodiment of the optical reader according to the present invention.
It is a schematic structure figure showing an embodiment.

As shown in FIG. 1, the optical reader 1 has a medium 12 on which a two-dimensional symbol 11 is printed.
, A driver circuit 3 for driving the light source 2, an optical system 4 for condensing light emitted from the light source 2 into a two-dimensional symbol 11, and a two-dimensional symbol irradiated with the light. The photodetector 8 includes a photodetector 8 that receives the reflected light from the photodetector 11 and converts the amount of the reflected light into an electric signal, and a signal processing unit 10 that processes the electric signal from the photodetector 8 to obtain image information.

As the light source 2 of the optical reader 1, a surface emitting laser array composed of a plurality of laser elements arranged in a predetermined direction and sequentially emitting light in a predetermined order is used, but the light source is limited to a laser. Is not something that is
D or the like may be used.

Further, the optical reader 1 is arranged between the optical system 4 and the medium 12, and reflects a laser beam passing through the optical system 4 while rotating the optical reader 1 in parallel with the arrangement direction of the laser elements. By rotating about the axis 5a, the reflection angle of the laser light is synchronized with the emission timing of the laser array 2 so that the reflected laser light scans the medium 12 in the scanning direction D intersecting the arrangement direction of the laser elements. And a rotating mirror 5 that changes the arrow A
, A motor drive circuit 7 for driving the motor 6, and a control device 9 for synchronizing the motor drive circuit 7 and the driver circuit 3.

FIG. 2 is a view showing a laser element array pattern of the surface emitting laser array used in the optical reader according to the first embodiment.

As the surface emitting laser array used here, a two-dimensional array in which laser elements are two-dimensionally arranged as shown in Japanese Patent Application Laid-Open No. 9-200431 can be used.

As shown in FIG. 2, the surface emitting laser array 2 includes a plurality of laser elements 2a in a direction inclined by an angle θ from an X direction parallel to the scanning direction by the rotating mirror 5.
A desired number of laser element groups, each having twelve laser elements per row, are arranged in the Y direction to form a two-dimensional array.

Here, the distance between the laser elements 2a in the X direction is dx, and the distance between the laser element groups in the Y direction is dx.
y. In addition, the inclination angle θ of each laser element group is defined by: the laser element at the right end in the drawing when the pattern of the laser array 2 is projected in the X direction; The distance g between the next laser element group located immediately below and the leftmost laser element is equal to the distance dp between adjacent laser elements in the laser element group when the laser element group is projected in the X direction. Is set to For example, if dx = dy = 0.042 mm, θ
= 4.76 degrees, and the distance dp = g = 0.0035 mm between the laser elements projected in the X direction. Therefore, when the magnification of the optical system 4 (see FIG. 1) is six times, the enlarged image of the pattern shown in FIG. 2 has a laser spot interval of 0.021 mm when projected in the X direction on the image forming plane. Dimensional symbol 11
(See FIG. 1).

Medium 12 on which two-dimensional symbol 11 is printed
Is placed at a predetermined position, and when the optical reader 1 is started, each laser element 2a of the laser array 2 (see FIG. 2) is sequentially turned on in response to the rotation of the rotating mirror 5, and the emitted laser light The light is emitted while scanning over the two-dimensional symbol 11, and the light detector 8 detects the amount of reflected light from each irradiation position on the two-dimensional symbol 11.

Here, assuming that the laser array 2 is composed of m rows × n columns (m, n) laser elements,
Each laser element is (1,1), (1,2), (1,3),
…, (1, n), (2,1), (2,2), (2,
3), ..., (2, n), (m, 1), (m, 2),
After lighting in the order of (m, 3), ..., (m, n),
Returning to (1, 1), the lights are turned on in the same order as above.

When the laser array 2 changes from (1, 1) to (m,
When the scanning speed of the laser light on the image forming surface due to the rotation of the rotating mirror is sufficiently slower than the time for lighting one cycle up to n), the laser array 2 irradiates a nearly stationary two-dimensional area. Is done.

Therefore, first, (1,1) to (1, n)
The rotating mirror is rotated by dθ on the line irradiated by the laser element group in the first row until the position is moved by [dx × 6], and then irradiated on the same line by the laser element group in the second row. When the laser beam is sequentially irradiated by the laser element groups on the third row, the fourth row,..., The twelfth row while rotating by the same interval, the signal of the reflected light emitted by the laser element group on the first row is obtained. On the other hand, when the signals from the second row to the twelfth row are overlapped while shifting the position by [dx × 6], the line having the width of [dx × 6 × m × n] is represented by [dx × 6]. A signal of the reflected light distribution when the light is irradiated at intervals can be obtained.

FIG. 3 is a view showing a laser element arrangement pattern (a) of a 4 × 4 surface emitting laser array and a two-dimensional symbol (b) read by the optical reader of this embodiment. 4 is a graph showing the amount of reflected light from a two-dimensional symbol read by the surface emitting laser array shown in FIG. 3 and a code signal obtained from the amount of reflected light.

The projection pattern 13 of the laser array arranged in a 4 × 4 matrix shown in FIG. 3A is mirrored on the symbol pattern 14 according to the rotation of the rotating mirror as shown in FIG. 3B. Scanning direction (Fig. 3
(See (a)).

As shown in FIG. 4A, a sub-scanning line 15 (see FIG. 3B) which is a lighting direction of a laser element group is
When four laser elements with m = 1 are located, the laser elements from n = 1 on m = 1 to the laser element with n = 4 are sequentially turned on at time intervals dt, and the reflected light thereof is detected by the photodetector 8. Is detected, the amount of reflected light that changes with time from one of a spot on the white pattern, a spot on the black pattern, and a spot that straddles the white pattern and the black pattern of the symbol pattern 14 changes with time according to the respective reflectance. can get.

Next, the laser beam is scanned in the scanning direction (see FIG. 3A) by the rotating mirror, and the sub-scanning line 15 (FIG.
(Refer to (b).) When the laser arrays m = 2, m = 3, and m = 4 are respectively positioned at the time period of tp, m = 1
As in the case of, a temporal change in the amount of light is detected.

Here, the signal delayed in time by dt is assumed to be at a position separated by a distance of [(dx) × (optical system magnification)], and is delayed in time by tp with respect to m = 1. It is assumed that the signal is located at a distance of [(dx) × (optical system magnification) ÷ (m = 4)]. Similarly, a signal of m = 3 delayed by [2 × tp] from m = 1, or m = 1
By performing the same processing on the signal of m = 4 delayed by [3 × tp], the reflected light amount distribution with respect to the position on the two-dimensional symbol is obtained as shown in FIG. The amount of reflected light obtained in this manner is processed by the threshold level S (see FIG. 4B), whereby 1
It can be converted to a dimensional code signal.

Further, the laser element group in the first row as a reference is irradiated at predetermined intervals in the rotation direction of the rotating mirror, and the laser element groups in the second to fourth rows are irradiated on each line. Then, when the signals of the first to fourth rows are superimposed in the same manner as described above, a code signal of a two-dimensional reflected light amount distribution is obtained as shown in FIG. By thresholding the code signal thus obtained, 2
An array of dimensional codes can be obtained.

Here, the resolution of the optical reader is determined by the spot diameter of the laser beam on the two-dimensional symbol and the interval between the spot diameters. The spot diameter of the laser beam depends on the angle of emission from the laser element and the magnification and brightness of the optical system. The interval between the laser beams in the Y direction (see FIG. 2) is a value obtained by multiplying the interval between the laser beams when projected in the X direction by the magnification of the optical system by the arrangement method on the laser array. The interval in the scanning direction (see FIG. 2)
It depends on how many two-dimensional symbols are divided in the scanning direction and how many.

Usually, one-dimensionally arranged laser arrays are used as the laser arrays. In this case, as described above, [(interval of laser arrays) × (magnification of optical system)] ] And the spot diameter of the laser beam on the two-dimensional symbol determine the actual reading resolution. The spacing between the one-dimensionally arranged laser arrays is 20μ from the point of fabrication.
m, it is difficult to reduce the resolution to 20 μm
In order to achieve this, an optical system of the same magnification must be used. However, when an equal-magnification optical system is employed, since the near-field image of a normal laser element is several μm, the spot diameter on the imaging surface also becomes several μm, and the focal depth becomes extremely shallow, In addition, since the irradiation range is narrower than the spot interval, reading becomes difficult and a reading error may occur.

There is also a method of increasing the spot diameter by darkening the brightness of the lens in an optical system of the same magnification, but in this case, the amount of light on the image forming surface is remarkably reduced, and a good S / N ratio is obtained.
No ratio can be obtained. Further, a 1 × optical system requires a light source and an optical system having the same width as the scanning width, so that there is a problem that the size of the exposure apparatus is increased.

On the other hand, in the method of the present embodiment, the spot diameter of the laser beam on the imaging plane can be changed in the range of 10 μm to 100 μm by using the magnifying optical system, and the two-dimensional array can be used. By doing so, the interval between spots on the imaging plane can also be set to a desired value. Further, by increasing the magnification, it is possible to scan a wide range with a small light source, and there is an advantage that the optical system can be downsized.

Next, a second embodiment of the optical reader according to the present invention will be described.

FIG. 5 is a side view of the optical reading apparatus according to the second embodiment of the present invention as viewed from a direction intersecting a scanning direction by a rotating mirror.

As shown in FIG. 5, in the optical reader 1 ′ of the present embodiment, when the laser light after passing through the optical system 4 from the light source 2 is scanned on the two-dimensional symbol 11 by the rotating mirror 5, Since the depth of focus becomes shallower as the spot diameter becomes smaller, the fluctuation of the spot diameter on the two-dimensional symbol 11 increases due to the rotation angle of the rotating mirror 5, and the reading accuracy deteriorates. Therefore, after exiting the optical system 4, it is desirable to keep the optical path length from the optical system 4 to the imaging plane 17 constant regardless of the rotation angle of the rotating mirror 5.

Now, if the position of the rotation axis 5a of the rotating mirror 5 is fixed and the distance from the optical system 4 to the reflecting surface of the rotating mirror 5 is fixed, the laser beam is scanned by the rotation of the rotating mirror 5. As shown by the broken line in FIG. 5, the beam waist of the laser beam draws an arc. Laser beam spot diameter is 1
In the case of 00 μm or more, a depth of focus of several tens of mm can be obtained, but when the spot diameter is about several tens of μm, the depth of focus becomes several mm or less. In that case, a deviation between the arc drawn by the beam waist of the laser light and the plane of the two-dimensional symbol causes defocus.

However, the scanning start position P1 and the scanning end position P2 of the laser beam are set symmetrically with respect to the position P0 at which the laser beam is perpendicularly incident on the two-dimensional symbol 11, so that this becomes the beam waist. When the light source 2, the optical system 4, and the rotation axis 5 a of the rotating mirror 5 are arranged at the position P <b> 0, the defocus becomes maximum at the position P <b> 0 where the laser light is perpendicularly incident on the two-dimensional symbol 11. Therefore, the rotating mirror 5
By moving the rotation axis 5a of the rotation mirror 5 along the optical axis 4a of the laser light from the optical system 4 to the rotation mirror 5 while rotating, the distance from the optical system 4 to the imaging plane 17 is made constant. be able to.

Therefore, in the optical reader 1 ′ of the second embodiment, regardless of the change in the scanning position of the laser beam caused by the rotation of the rotary mirror 5, the laser beam from the optical system 4 to the image forming plane 17 is changed. A configuration is provided with a rotating mirror reciprocating device 16 that reciprocates the rotating shaft 5a of the rotating mirror 5 along the optical axis 4a of the laser light from the optical system 4 to the rotating mirror 5 so that the optical path length is kept constant. I have.

When the laser beam emitted from the laser element located at the center of the laser array 2 and reflected by the rotating mirror 5 irradiates the medium 12 vertically, the rotating mirror reciprocating device 16 rotates the rotating shaft from the optical system 4. The rotating shaft 5a is reciprocated so that the distance to 5a is maximized.

FIG. 6 is a graph showing the relationship between the scanning position of the laser beam and the moving distance of the mirror rotation axis in the optical reader shown in FIG.

The scanning position P0, which is the center point of the horizontal axis of the graph of FIG. 6, is the position where the laser beam is perpendicularly incident on the two-dimensional symbol 11, as shown in FIG. The rotating shaft 5a at this time
Is assumed to be M0, as the laser beam is scanned from the scanning position P0 toward the laser beam scanning start position P1, the moving distance M of the rotating shaft 5a from the M0 position increases as shown in FIG. Similarly, when the laser beam is scanned from the scanning position P0 toward the scanning end position P2, the moving distance M of the rotating shaft 5a from the M0 position increases. That is, when the laser beam irradiates the scanning position P0, the distance from the optical system 4 to the rotation axis 5a is the maximum (moving distance M
= 0).

In this embodiment, the rotating mirror reciprocating device 1
6, the rotation axis 5a of the rotation mirror 5 is connected to the optical axis 4 as described above.
The laser beam is reciprocated along a, but the rotating mirror 5 is rotated in accordance with the reciprocating motion so that the angle of reflection of the laser beam by the rotating mirror 5 is adjusted. That is, as shown in FIG. 1, in the present embodiment, a rotating mirror 5 that changes the reflection angle of the laser light in synchronization with the light emission timing of the laser array 2, a motor 6 that rotates the rotating mirror 5, a motor 6 and a control device 9 for synchronizing the motor drive circuit 7 and the driver circuit 3 with each other.
(See FIG. 5), when scanning is started from the scanning position P0 toward the scanning position P0, the angle θ between the light incident on the rotating mirror 5 and the reflected light from the rotating mirror 5 becomes the minimum angle, and the scanning position P0
Gradually increases, the angle θ becomes 90 degrees when the laser beam irradiates the scanning position P0.

As the laser beam passes through the scanning position P0 and moves toward the scanning end position P2, the angle θ is further increased beyond 90 ° and is controlled so that the angle θ becomes maximum when the laser beam reaches the scanning start position P1. You.

As described above, in the second embodiment, the rotating shaft 5 of the rotating mirror 5 is
a is reciprocated along the optical axis 4a.
The optical path length of the laser light from the laser beam to the imaging plane 17 is always kept constant, so that the scanning can be performed with the beam waist of the laser light always positioned on the two-dimensional symbol. .

[0046]

As described above, according to the optical reader of the present invention, the optical reader is disposed between the optical system and the medium.
By rotating around a rotation axis parallel to the arrangement direction of the laser elements while reflecting the laser light passing through the optical system, the reflected laser light scans the medium in a direction crossing the arrangement direction of the laser elements. In addition, by providing a rotating mirror that changes the reflection angle of the laser light in synchronization with the light emission timing of the laser array, it is possible to take advantage of the long focal depth of the optical system while taking advantage of the laser light's long focal length. It is possible to realize a small optical reader capable of reading a complex image with high accuracy.

Further, regardless of the change in the reflection angle of the laser light due to the rotation of the rotating mirror, the rotation axis of the rotating mirror is moved from the optical system so that the optical path length of the laser light from the optical system to the medium is kept constant. When a rotating mirror reciprocating device for reciprocating along the optical axis of the laser light to the rotating mirror is provided,
High resolution reading is possible even if the laser beam is focused on a minute spot.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of an optical reader according to the present invention.

FIG. 2 is a diagram illustrating a laser element array pattern of a surface emitting laser array used in the optical reader according to the first embodiment.

FIG. 3 is a diagram illustrating a laser element arrangement pattern (a) of a 4 × 4 surface emitting laser array and a two-dimensional symbol (b) read by the optical reading device of the present embodiment.

4 is a graph showing a light amount of reflected light from a two-dimensional symbol read by the surface emitting laser array shown in FIG. 3 and a code signal obtained from the reflected light amount.

FIG. 5 is a side view of an optical reader according to a second embodiment of the present invention as viewed from a direction intersecting a scanning direction by a rotating mirror.

6 is a graph showing a relationship between a scanning position of a laser beam and a moving distance of a mirror rotation axis in the optical reader shown in FIG.

[Explanation of symbols]

 1, 1 'Optical reader 2 Light source (surface emitting laser array) 3 Driver circuit 4 Optical system 4a Optical axis 5 Rotating mirror 5a Rotating axis 6 Motor 7 Motor driving circuit 8 Photodetector 9 Control device 10 Signal processing unit 11 2 Dimensional symbol 12 Medium 13 Projection pattern 14 Symbol pattern 15 Sub-scanning line 16 Rotating mirror reciprocating device 17 Image plane

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideaki Ashikaga 430 Nakai-cho, Nakai-cho, Ashigara-gun, Kanagawa Prefecture Inside Fuji Xerox Fuji Xerox Co., Ltd. (72) Inventor Tetsuya Kimura 430 Sakai, Nakai-cho, Ashigara-gun, Kanagawa Prefecture Green Tech Nakai Fuji Xerox Co., Ltd. (72) Inventor Shoji Yamaguchi 430 Nakai-cho Sakai-Kamigami-gun, Kanagawa Prefecture Green Tech Nakai Inside Fuji Xerox Co., Ltd. (72) Inventor Hidehiko Yamaguchi 430 Nakai-machi Sakai, Ashigara-gun, Kanagawa Prefecture Green Tech Nakai Fuji Xerox Co., Ltd. F-term (reference) 5B072 AA02 AA03 CC21 DD02 LL04 LL11 LL18

Claims (3)

[Claims] A light source for irradiating a predetermined medium with light, an optical system for condensing light emitted from the light source on the medium,
A photodetector that receives reflected light from the medium irradiated with light and converts the amount of the reflected light into an electric signal, and a signal processing unit that processes the electric signal from the photodetector to obtain image information An optical reader having: a light-emitting element array comprising a plurality of light-emitting elements arranged in a predetermined direction and sequentially emitting light in a predetermined order, wherein the light source is disposed between the optical system and the medium. By rotating around a rotation axis parallel to the arrangement direction of the light emitting elements while reflecting the light passing through the optical system, the reflected light crosses the medium in the direction intersecting with the arrangement direction of the light emitting elements. An optical reader comprising: a rotating mirror that changes a reflection angle in synchronization with a light emission timing of the light emitting element array so as to scan. 2. A rotation axis of the rotating mirror from the optical system to maintain a constant optical path length from the optical system to the medium irrespective of a change in a reflection angle due to rotation of the rotating mirror. 2. The optical reader according to claim 1, further comprising a rotating mirror reciprocating device that reciprocates along the optical axis up to the rotating mirror. 3. The rotating mirror reciprocating device, when light emitted from a light emitting element positioned at the center of the light emitting element array and reflected by the rotating mirror irradiates the medium vertically, the rotating system reciprocates from the optical system. 3. The optical reader according to claim 2, wherein the rotating shaft is reciprocated so that the distance to the rotating shaft is maximized.