WO2010143662A1

WO2010143662A1 - Optical information reading device

Info

Publication number: WO2010143662A1
Application number: PCT/JP2010/059772
Authority: WO
Inventors: 久水文也; 川島安武
Original assignee: 株式会社オプトエレクトロニクス
Priority date: 2009-06-12
Filing date: 2010-06-09
Publication date: 2010-12-16
Also published as: JP2010286740A

Abstract

Disclosed is an optical information reading device, which is provided with a focus function and a zoom function using a liquid lens with a simple configuration. The optical information reading device (1) is provided with: a lens module (2) wherein liquid lenses (20A, 20B), which change the shapes of the boundary surfaces when a voltage is applied, are disposed at a predetermined interval with which the focal point distances can be changed by changing the shapes of the boundary surfaces, and at least one optical lens (27) is disposed; an image sensor (30) which photoelectrically converts optical signals which have passed through the lens module (2); thermistors (26A, 26B) which detect the temperatures of the liquid lenses (20A, 20B); a distance measuring unit (31) which measures the distance to a code mark (5); and an ASIC (40) which performs focus control and zoom control on the basis of the information of the distance measured by means of the distance measuring unit (31) and the information of the temperatures detected by means of the thermistors (26A, 26B).

Description

Optical information reader

The present invention relates to an optical information reader having a focus function and a zoom function using a liquid lens.

Bar codes that are one-dimensional code information are well known for the purpose of merchandise management and inventory management. A two-dimensional code is known as a code having a higher information density. As a device for reading a two-dimensional code, a method is known in which a two-dimensional code is photographed with a solid-state imaging device such as a CMOS image sensor or a CCD image sensor, and the image is subjected to various processing and then binarized and decoded. Yes.

Since the 2D code has a large amount of information that can be loaded, not only the price, product name, suppliers, etc., but also the information necessary for the management and sales side, as well as the production area, ingredients, simple precautions, usage, etc. It is also possible to provide information serving as a service when selling products to customers.

The CMOS image sensor used in such a device that reads code information is not functionally different from what is mounted on a digital camera or the like, so it functions as a photographer that normally shoots objects and landscapes. Is required. For example, in the case of inventory management or the like, it is used when an image of a position where the article is stored together with the target article is stored in a database together with code information.

The mobile phone is equipped with a small camera using the above-described CMOS image sensor. Most of the camera functions of mobile phones include a barcode / two-dimensional code scanner and an OCR (optical character reader), as well as images of landscapes and people, like ordinary digital cameras. is there.

An apparatus that performs imaging with a solid-state imaging device requires a configuration for focusing and a configuration for adjusting the size of an image, a configuration for automatically adjusting a focus position, a so-called autofocus function, and a configuration for changing a focal length, a so-called configuration. A zoom function is required. For the auto focus function and zoom function, a method of mechanically moving the lens position along the optical axis is known, but it is difficult to mount such a mechanism in a small device such as a mobile phone. is there. Therefore, there is a demand for a configuration in which the lens itself has an autofocus mechanism and a zoom. One of them is a liquid lens.

Conventionally, a technique for realizing a zoom function with a liquid lens has been disclosed (for example, see Patent Document 1). In addition, a technique in which a liquid lens is applied to a camera that captures a landscape or a person is disclosed (for example, see Patent Documents 2 and 3).

JP 2007-128084 A JP 2008-158247 A JP 2006-201639 A

For a general camera equipped with a solid-state imaging device, a technique has been proposed in which images are captured in a continuous manner and only the image in focus is decoded. However, the image is captured and decoded. Takes a long time to complete, and is not applicable to code scanners that manage merchandise and goods. Further, the code scanner needs to acquire a clear image having a predetermined size that can be decoded, and in a configuration using a liquid lens, compensation by temperature is required.

The present invention has been made to solve such a problem, and an object thereof is to provide an optical information reading apparatus having a focus function and a zoom function using a liquid lens with a simple configuration.

In order to solve the above-described problem, the present invention provides a first liquid and a second liquid, which have different optical refractive indexes and in which a boundary surface is formed without being mixed with each other, sealed in a container, Two or more liquid lenses to which a voltage for controlling the shape of the boundary surface between the liquid and the second liquid is applied are arranged with a predetermined interval at which the focal length can be changed by changing the shape of the boundary surface. In addition, a lens module in which at least one optical lens is disposed, an imaging unit having a solid-state imaging device that photoelectrically converts an optical signal transmitted through the lens module, and a temperature detection unit that detects the temperature of each liquid lens, Control for performing focus control and zoom control based on distance measurement means for measuring the distance to the reading object, distance information to the reading object measured by the distance measurement means, and temperature information detected by the temperature detection means. It is an optical information reading and means.

In the optical information reading device of the present invention, when the curvature of the boundary surface is changed in each liquid lens, the focal length can be continuously changed and the focal position can be adjusted to an arbitrary distance. Then, voltage information to be applied to the liquid lens is set based on the distance information to the reading object, and focus control for adjusting the focal position and zoom control for obtaining an image having a size suitable for decoding are performed. The voltage information to be applied to the liquid lens is compensated by the temperature information, and optimum focus control and zoom control are performed even if the temperature fluctuates.

According to the optical information reading apparatus of the present invention, focus control and zoom control can be performed without moving the lens, and the focus function and zoom function can be realized with a simple configuration. Thereby, it becomes possible to incorporate in a small apparatus. Further, since focus control and zoom control are performed based on the distance information and the temperature information, a clear image can be acquired in a short time, and a clear image can be acquired even if the temperature fluctuates.

It is a functional block diagram which shows an example of the optical information reader of this Embodiment. It is an internal block diagram which shows an example of the liquid lens which comprises the lens module of this Embodiment. It is a graph which shows the relationship between temperature and the response time of a liquid lens. It is a graph which shows the relationship between the temperature measured with the thermistor, and standby time. It is a graph which shows the relationship between the distance to a code symbol, and a field angle. It is a block diagram which shows arrangement | positioning of each lens in the lens module of this Embodiment. It is a graph which shows the change of the curvature of a liquid lens at the time of zoom. It is a graph which shows the relationship between the space | interval of a liquid lens, and a field angle. It is a block diagram which shows the specific example of a lens module. It is a block diagram which shows the specific example of a lens module. It is a block diagram which shows the specific example of a lens module. It is a flowchart which shows an example of a process of the optical information reader of this Embodiment. It is operation | movement explanatory drawing of a liquid lens. It is operation | movement explanatory drawing of a liquid lens. It is operation | movement explanatory drawing of a liquid lens.

Hereinafter, an embodiment of an optical information reading apparatus provided with a lens module of the present invention will be described with reference to the drawings.

<Example of Configuration of Optical Information Reading Device of the Present Embodiment>
FIG. 1 is a functional block diagram illustrating an example of an optical information reading apparatus according to the present embodiment, and FIG. 2 is an internal configuration diagram illustrating an example of a liquid lens constituting the lens module according to the present embodiment.

The optical information reading apparatus 1 according to the present embodiment includes a camera module 3 having a lens module 2 and a decoder 4. The lens module 2 includes a plurality of liquid lenses, in this example, two

liquid lenses

20A and 20B.

The liquid lens 20 A and the liquid lens 20 B are made of a conductive material that is an example of a first liquid in a cylindrical container 21 in which an incident surface 21 a and an output surface 21 b are formed of a transparent material that transmits light of a predetermined wavelength. High-water solution 22 and insulating oil 23, which is an example of the second liquid, are sealed.

The aqueous solution 22 and the oil 23 are separated in a direction along the optical axis O of the liquid lens 20A and the liquid lens 20B, and a boundary surface 24 through which light is transmitted without being mixed with each other is formed. The aqueous solution 22 and the oil 23 sealed by the liquid lens 20A and the liquid lens 20B have different light refractive indexes, and the light transmitted from the incident surface 21a to the output surface 21b is refracted at the boundary surface 24 between the aqueous solution 22 and the oil 23. Is done.

The liquid lens 20A and the liquid lens 20B include an electrode 25a in contact with the aqueous solution 22 and an electrode 25b in contact with both the aqueous solution 22 and the oil 23 through an insulating portion. When electricity is applied from the

electrodes

25a and 25b and a voltage is applied to the aqueous solution 22, the shape of the boundary surface 24 between the aqueous solution 22 and the oil 23 can be changed. Such a phenomenon is called an electrowetting phenomenon.

Two liquid lenses 20 A and 20 B are arranged in series along the optical axis O, and in the liquid lenses 20 A and 20 B, the curvatures R 1 and R 2 of the boundary surface 24 between the aqueous solution 22 and the oil 23 are changed. It is possible to realize a function of continuously changing a focal distance called “focus” and a function of adjusting a focus position called “focus”.

The lens module 2 includes a thermistor 26A that detects the temperature of the liquid lens 20A and a thermistor 26B that detects the temperature of the liquid lens 20B. The

thermistors

26A and 26B are an example of temperature detection means. The thermistor 26A is mounted on a flexible substrate (not shown) connected to the electrode of the liquid lens 20A, for example, so that the temperature around the liquid lens 20A can be accurately detected. Like that. The thermistor 26B is mounted on a flexible substrate (not shown) connected to the electrode of the liquid lens 20B, for example, so that the temperature around the liquid lens 20B can be accurately detected.

The lens module 2 includes at least one optical lens 27. The optical lens 27 is composed of, for example, a convex lens, and is disposed at the subsequent stage of the liquid lens 20B. The liquid lens 20A, the liquid lens 20B, and the optical lens 27 are attached to a lens housing (not shown) with the optical axes aligned. The optical lens 27 may be a single optical lens made of glass, plastic or the like that transmits light of a predetermined wavelength, or may be a combination of a plurality of optical lenses.

The camera module 3 includes the lens module 2 described above, an image sensor 30 that forms an imaging unit, and a distance measuring unit 31. The image sensor 30 is an example of a solid-state imaging device, and photoelectrically converts an input optical signal and outputs an electrical signal. As the image sensor 30, for example, a CMOS image sensor or a CCD image sensor is used. The image sensor 30 is disposed at a position where the light transmitted through the lens module 2 forms an image by the functions of the liquid lens 20 A, the liquid lens 20 B, and the optical lens 27.

The distance measuring unit 31 is an example of a distance measuring unit and includes, for example, a laser light receiving and emitting unit and the like, and measures the distance from the code symbol 5 that is a reading object. The camera module 3 may include an illumination LED 32 that emits guide light indicating the code symbol 5 of the reading object. The illumination LED 32 is provided as appropriate, and may not be mounted depending on the shape of the apparatus and the purpose of use.

The decoder 4 is an example of a signal processing unit, and performs control such as zoom and focus adjustment performed by the lens module 2, imaging performed by the image sensor 30, decoding of a signal output from the image sensor 30, and data transfer. An ASIC (Application Specific Specific Integrated Circuit) 40 is provided as a means. The decoder 4 includes a RAM 41 and a ROM 42 in which programs executed by the ASIC 40 and various tables are stored.

Further, the decoder 4 is connected to the lens module 2 and the camera module 3 as a signal input / output unit, and is connected to an information processing apparatus such as an external host computer (not shown). I / O 44 is provided.

The optical information reading apparatus 1 may include an operation unit 45 as a setting unit in order to acquire identification information for identifying the type of the code symbol 5 that is an imaging target. The operation unit 45 includes, for example, a display and a keyboard (not shown), and information is input or selected according to the display on the display. Further, without providing the operation unit 45, the identification information of the code symbol 5 may be acquired from an external information processing apparatus (not shown) and stored in the RAM 41.

The optical information reader 1 has a configuration in which the above-described components are mounted in a housing (not shown), for example, and a user can take an image with the hand. The optical information reader 1 is a scanner that can read a code symbol 5 such as a bar code and a two-dimensional code. However, if the OCR software is installed, the optical information reader 1 can also read characters. The ASIC 40 may be a combination of a CPU and an LSI such as an FPGA (Field Programmable Gate Array).

Next, a focus function for adjusting the focal position in the optical information reader 1 will be described. The optical information reading device 1 performs imaging when the reflected light from the code symbol 5 at an arbitrary distance forms an image on the image sensor 30, that is, when there is a so-called focus. This is because the content of the code symbol 5 cannot be decoded unless the image is clearly captured.

In the optical information reader 1, the distance from the code symbol 5 to be imaged is measured, and the

liquid lenses

20A and 20B of the lens module 2 are controlled so that the focal position matches the measured distance. For this reason, the camera module 3 includes a distance measuring unit 31 using a laser. There are two well-known laser distance measurement techniques. One is a pulsing technique, which measures the delay time between the start of the laser pulse and the return of the reflection to determine the distance. The other is a parallax (parallax) technique, in which a beam is irradiated to form a spot on the imaging object, and the detection spot position on the imaging object is measured. The distance of the imaging object is determined from the detected spot position. The distance measurement method is not limited to these examples, but the ASIC 40 is programmed to perform distance measurement by any one of these methods, for example.

In the liquid lens 20A and the liquid lens 20B, the curvatures R1 and R2 of the boundary surface 24 between the aqueous solution 22 and the oil 23 change according to the applied voltage. When the curvatures R1 and R2 of the

liquid lenses

20A and 20B change, the refractive power of the

liquid lenses

20A and 20B changes. Therefore, an applied voltage necessary for focusing on a reading object at an arbitrary distance is uniquely determined. It is done.

Therefore, in order to focus on the distance information Ld from the optical information reader 1 to the code symbol 5 that is the object to be read and the code symbol 5 at the position specified by the distance information Ld, the

liquid lenses

20A and 20B are focused on. The relationship between the voltage information V1 to be applied is measured to create a distance-voltage table TB1 and stored in the ASIC 40. Thereby, it is possible to acquire voltage information V1 corresponding to the distance to the code symbol 5 measured by the distance measuring unit 31.

On the other hand, the

liquid lenses

20A and 20B need a standby time after the voltage is applied until the curvatures R1 and R2 according to the applied voltage become possible and imaging becomes possible. This imaging standby time varies depending on the ambient temperature of the

liquid lenses

20A and 20B.

FIG. 3 is a graph showing the relationship between the temperature and the response time of the liquid lens. In FIG. 3, when a predetermined voltage capable of focusing on the imaging target is applied to the liquid lens, changes in the sharpness of the image obtained through the liquid lens are shown by graphs 301 to 303 for each predetermined temperature. . For example, when the sharpness of an image that can be decoded by the ASIC 40 is defined as a threshold Th, and the time until reaching the threshold Th is defined as an imaging standby time, the imaging standby time is generally smaller when the temperature is high, and the graph As shown in 301 and graph 302, the imaging standby time at 60 ° C. is much shorter than the imaging standby time at 25 ° C.

Therefore, the relationship between the temperature information Tp of the

liquid lenses

20A and 20B and the imaging standby time information Tm is measured, and a temperature-standby time table TB2 is created and stored in the ASIC 40. Since the

thermistors

26A and 26B are respectively provided in the

liquid lenses

20A and 20B, the ambient temperature and the imaging standby time of the respective

liquid lenses

20A and 20B are measured in advance.

FIG. 4 is a graph showing the relationship between the temperature measured by the thermistor and the standby time. FIG. 4 shows the minimum imaging standby time at which a sharpness image that can be decoded by the ASIC 40 can be captured with respect to the temperature measured by the

thermistors

26A and 26B. Thereby, it is possible to acquire imaging standby time information Tm according to the temperature of the liquid lens 20A measured by the thermistor 26A and the temperature of the liquid lens 20B measured by the thermistor 26B.

As described above, the distance-voltage table TB1 indicating the relationship between the distance information Ld up to the code symbol 5 and the voltage information V1 to be applied to the

liquid lenses

20A and 20B, the temperature information Tp of the

liquid lenses

20A and 20B, and the imaging. Optimal focus adjustment is made by the temperature-standby time table TB2 showing the relationship with the wait time information Tm, and a clear image of the code symbol 5 can be captured.

Next, the zoom function for continuously changing the focal length in the optical information reader 1 will be described. In the optical information reader 1, in order to decode the image of the code symbol 5 formed on the image sensor 30 by the ASIC 40, an image having a predetermined size is required according to the resolution of the image sensor 30.

The size of the image formed on the image sensor 30 is determined by the distance from the optical information reader 1 to the code symbol 5 that is the object to be read and the size of the code symbol 5. Therefore, the relationship between the angle of view ω estimated from the distance information Ld to the code symbol 5 and the size information W of the code symbol 5 to be imaged is measured to create the distance-view angle table TB3 and store it in the ASIC 40. Keep it.

FIG. 5 is a graph showing the relationship between the distance to the code symbol and the angle of view. FIG. 5 shows the angle of view with respect to the distance in Code 39 (pitch 0.254, width 70 mm), which is a general one-dimensional code. If the size of the code symbol 5 and the distance to the code symbol 5 are known, it is possible to predict the angle of view necessary for obtaining an image of a desired size. Thus, if a distance-view angle table TB3 such as a PDF417 code or a two-dimensional code that is frequently used as a reading object is created, the view angle can be acquired from the distance information.

The angle of view at which the image formed on the image sensor 30 has a predetermined size is determined by the focal length of the lens module 2, and the focal length of the lens module 2 is determined by the combination of the curvatures R1 and R2 of the

liquid lenses

20A and 20B. Therefore, the relationship between the focal length of the lens module 2 and the applied voltage is uniquely determined.

Therefore, the relationship between the focal length information fd for determining the angle of view ω of the lens module 2 and the voltage information V2 to be applied to the

liquid lenses

20A and 20B is measured, and the focal length-voltage table TB4 is created and stored in the ASIC 40. Keep it. Note that the temperature-standby time table TB2 described above is also necessary when performing zooming. As a result, it is possible to acquire voltage information V2 corresponding to the distance to the code symbol 5 measured by the distance measuring unit 31 and the size of the code symbol by using the distance-view angle table TB3 and the focal length-voltage table TB4. Become.

<Configuration Example of Lens Module of the Present Embodiment>
FIG. 6 is a configuration diagram showing the arrangement of each lens in the lens module of the present embodiment. In order to realize a zoom function using a liquid lens, the lens module 2 includes at least two

liquid lenses

20A and 20B and one optical lens 27 as described above.

In the liquid lens 20A and the liquid lens 20B, when the curvatures R1 and R2 of the boundary surface 24 between the aqueous solution 22 and the oil 23 are changed, the focal length f from the principal point determined by the curvature and arrangement of each lens changes. In FIG. 6, for convenience, the optical lens 27 is illustrated as having a main point. Further, the focal length f is also changed by changing the distance Le between the liquid lens 20A and the liquid lens 20B.

In the configuration shown in FIG. 6, the distance L between the image-side liquid lens 20A and the image FC to be read is 100 mm, and the distance Lg between the image lens 30-side liquid lens 20B and the optical lens 27 is 3 mm. Under such conditions, changes in the angle of view when the curvature R1 of the liquid lens 20A, the curvature R2 of the liquid lens 20B, and the distance Le between the liquid lens 20A and the liquid lens 20B are changed are measured. The angle of view (half value) of only the optical lens 27 is 16 °.

FIG. 7 is a graph showing the change in the curvature of the liquid lens during zooming, and FIG. 8 is a graph showing the relationship between the distance between the liquid lenses and the angle of view. From the result of FIG. 8, it can be seen that the zoom magnification of the lens module 2 can be increased as the distance between the liquid lens 20A and the liquid lens 20B is increased.

9 to 11 are configuration diagrams showing specific examples of lens modules. In the configuration including two

liquid lenses

20A and 20B and one optical lens 27 shown in FIG. 9, the zoom magnification increases as the distance Le between the liquid lens 20A and the liquid lens 20B increases. On the other hand, when the distance Le between the liquid lens 20 A and the liquid lens 20 B is increased, the ambient light does not reach the image sensor 30 by hitting the lens barrel between the liquid lenses, resulting in insufficient light quantity or so-called vignetting.

Therefore, in the configuration shown in FIG. 9, when the aperture is set at the center of the

liquid lenses

20A and 20B, the distance Le between the liquid lens 20A and the liquid lens 20B is about 9.6 mm at the maximum. At this time, the angle of view ω can be changed from 14.329 ° to 17.8443 °, and the zoom magnification is 1.26 times.

As a configuration in which the peripheral light amount does not decrease even if the distance Le between the liquid lens 20A and the liquid lens 20B is increased to 10 mm or more, for example, a configuration as shown in FIG. 10 is conceivable. In FIG. 10, the configuration includes two liquid lenses 20 A and 20 B and one optical lens 27, and a concave meniscus lens 28 is added to the top of the lens group to narrow the light.

Accordingly, the zoom magnification can be increased by separating the distance Le between the liquid lens 20A and the liquid lens 20B without reducing the peripheral light amount as compared with the configuration of FIG. 9 that does not include the concave meniscus lens. it can. In the configuration shown in FIG. 10, the distance Le between the liquid lens 20A and the liquid lens 20B is about 17 mm at the maximum. At this time, the angle of view ω can be changed from 13.003 ° to 17.924 °, and the zoom magnification is 1.4 times.

9 and 10, the configuration includes two

liquid lenses

20A and 20B. However, as a result of simulation, it has been found that the zoom magnification can be further increased by increasing the number of liquid lenses to two or more. Therefore, in FIG. 11, four

liquid lenses

20A, 20B, 20C, and 20D are provided, a concave meniscus lens 28 is provided in the front stage of the liquid lens group, and an optical lens 27 is provided in the rear stage. In the configuration of FIG. 11, the distance Le between the liquid lens 20A and the liquid lens 20D at both ends is about 30 mm at the maximum. At this time, the angle of view ω can be changed from 9.8 ° to 21.95 °, and the zoom magnification is 2.3 times.

<Example of Operation of Optical Information Reading Device of Present Embodiment>
FIG. 12 is a flowchart showing an example of processing of the optical information reading apparatus according to the present embodiment, and FIGS. 13 to 15 are explanatory diagrams of the operation of the liquid lens. Next, the optical information reading according to the present embodiment An operation of reading the code symbol 5 by the apparatus 1 will be described.

In the optical information reader 1, first, in step S1 of FIG. 12, the operation unit 45 is operated to set the type of the code symbol 5 to be read. For example, the ROM 42 stores in advance identification information for specifying the type of the code symbol 5 and the like, and the identification information of the code symbol 5 to be read is selected by the operation on the operation unit 45.

In the optical information reading device 1, the ASIC 40 measures the distance from the output of the distance measuring unit 31 to the code symbol 5 in step S2 to acquire the distance information Ld, and from the outputs of the

thermistors

26A and 26B, the liquid lens 20A. , 20B temperature information Tp is acquired.

In step S3, the ASIC 40 needs to zoom the distance to the code symbol 5 from the identification information of the code symbol 5 set by the operation unit 45 and the distance information Ld to the code symbol 5 detected by the distance measuring unit 31. It is determined whether or not the value is greater than a certain value.

When the ASIC 40 determines in step S3 that the distance to the code symbol 5 is equal to or greater than the integral value, the distance-view angle table TB3 corresponding to the identification information of the code symbol 5 set in the operation unit 45 is selected in step S4. To do. Then, referring to the distance-view angle table TB3, the focal length-voltage table TB4, and the temperature-standby time table TB2, the distance information Ld up to the code symbol 5 detected by the distance measuring unit 31 and the

thermistors

26A, 26B Voltage information V2 and imaging standby time information Tm corresponding to the detected temperature information Tp of the

liquid lenses

20A and 20B are acquired.

Here, the voltage information V2 is set for each of the

liquid lenses

20A and 20B, and when the distance to the code symbol 5 is far, a voltage that increases the size of the image formed on the image sensor 30 is applied. Is done. For example, as shown in FIG. 13, the curvatures R1 and R2 of the liquid lens 20A and the liquid lens 20B, that is, the curvatures R1 and R2 of the boundary surface 24 between the aqueous solution 22 and the oil 23 in the liquid lens 20A and the liquid lens 20B are concave. Such a voltage is applied.

In the above example, when the distance to the code symbol 5 is a certain value or more, the zoom is performed so that the size of the image formed on the image sensor 30 is increased. If the distance is equal to or smaller than another fixed value, zooming may be performed so that the size of the image formed on the image sensor 30 is reduced. When the distance to the code symbol 5 is short, for example, as shown in FIG. 14, a voltage is applied so that the curvatures R1 and R2 of the liquid lens 20A and the liquid lens 20B are convex.

When the ASIC 40 determines that the distance to the code symbol 5 is smaller than the integrated value in step S3 described above, the distance measuring unit 31 refers to the distance-voltage table TB1 and the temperature-standby time table TB2 in step S5. The voltage information V1 and the imaging standby time information Tm corresponding to the detected distance information Ld to the code symbol 5 and the temperature information Tp of the

liquid lenses

20A and 20B detected by the

thermistors

26A and 26B are acquired.

Here, the voltage information V1 is set for each of the

liquid lenses

20A and 20B, and a voltage is applied so that the image of the code symbol 5 at the position specified by the distance information Ld is formed on the image sensor 30. . For example, as shown in FIG. 14, a voltage corresponding to the distance information Ld is applied from a state in which the curvatures R1, R2 of the liquid lens 20A and the liquid lens 20B are flat.

In step S6, the ASIC 40 performs zoom control according to the identification information of the code symbol 5 and the distance information Ld to the code symbol 5, and focus control according to the distance information Ld to the code symbol 5, and the thermistors 26A, After the imaging standby time corresponding to the temperature information Tp of the

liquid lenses

20A and 20B detected at 26B has elapsed, the code symbol 5 is imaged by the image sensor 30.

In step S7, the ASIC 40 determines whether the size of the captured code symbol 5 is appropriate for decoding. In the processing of steps S3 and S4 described above, zoom control is performed with reference to the distance-view angle table TB3 and the focal length-voltage table TB4 based on the identification information of the code symbol 5 and the distance information Ld to the code symbol 5. Yes. The optical information reader 1 can recognize the assumed size of the code symbol 5 to be read by setting the identification information of the code symbol 5 to be read in advance. Therefore, normally, an image of a desired size can be acquired by performing zoom control with reference to the distance-view angle table TB3 and the focal length-voltage table TB4.

However, even if the type of code symbol 5 is the same, there may be a plurality of types, and there may be a case where an image of an appropriate size cannot be acquired with the distance-view angle table TB3 and the focal length-voltage table TB4. . Therefore, in step S7, it is determined whether or not the size of the captured code symbol 5 is appropriate for decoding.

If it is determined in step S7 that the size of the captured code symbol 5 is appropriate for decoding, in step S8, the captured image data is decoded and data indicating the content of the code symbol 5 is output. . On the other hand, if it is determined in step S7 that the size of the captured code symbol 5 is not an appropriate size for decoding, the process returns to step S4 to perform zoom control according to the size information W of the code symbol 5. The code symbol 5 is imaged and decoded again.

In the above operation example, the identification information of the code symbol 5 is acquired in advance. However, the code symbol 5 may be imaged by the image sensor 30 and the feature point is detected to identify the code symbol. Moreover, you may identify from the magnitude | size of a code symbol.

The present invention can be used for a barcode reader, a two-dimensional code reader, and the like, and can realize autofocus and zoom with a small device.

DESCRIPTION OF SYMBOLS 1 ... Optical information reader, 2 ... Lens module, 3 ... Camera module, 4 ... Decoder, 20A, 20B ... Liquid lens, 26A, 26B ... Thermistor, 27 ...・ Optical lens, 30 ... Image sensor, 31 ... Ranging unit, 40 ... ASIC

Claims

A first liquid and a second liquid having different optical refractive indexes and forming a boundary surface without being mixed with each other are sealed in a container, and the boundary surface between the first liquid and the second liquid is sealed. Two or more liquid lenses to which a voltage for controlling the shape is applied are arranged at a predetermined interval at which the focal length can be changed by changing the shape of the boundary surface, and at least one optical lens is provided. An arranged lens module;
An imaging unit having a solid-state imaging device that photoelectrically converts an optical signal transmitted through the lens module;
Temperature detecting means for detecting the temperature of each liquid lens;
Distance measuring means for measuring the distance to the reading object;
An optical device comprising: distance information to the reading object measured by the distance measuring means; and control means for performing focus control and zoom control based on the temperature information detected by the temperature detecting means. Information reader.
The control means determines whether the distance to the reading object is a distance that needs to be zoomed based on the distance information to the reading object measured by the distance measuring means, and the zoom is necessary. If the distance is determined to be a distance, focus control and zoom control are performed based on the distance information to the reading object measured by the distance measurement unit and the temperature information detected by the temperature detection unit, and zooming is unnecessary. The focus control is performed based on the distance information to the reading object measured by the distance measuring unit and the temperature information detected by the temperature detecting unit when it is determined that the distance is detected. Optical information reader.
Comprising setting means for setting identification information for identifying a reading object;
The control means performs zoom control based on an assumed size of the reading target specified based on the identification information set by the setting means and distance information to the reading target measured by the distance measuring means. The optical information reader according to claim 1, wherein the optical information reader is performed.
The control means determines whether or not the zoom is necessary based on the size information of the reading object imaged by the imaging unit, and determines that the zoom is necessary. The optical information reader according to claim 1, wherein zoom control is performed based on
5. The optical device according to claim 1, wherein the lens module includes a concave meniscus lens disposed in the front stage of each liquid lens and a convex lens disposed in the rear stage as the optical lens. Information reader.