JP2009033561A - Information code reader and method of reading the same code - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information code reader for raising a success rate of decoding of information code and moreover improving reliability of the decoding and also provide a method of reading the information code. <P>SOLUTION: The information code reader includes an optical system 210 having optical wave surface modulating element forming a primary image, an imaging element 220, an image processing unit 230 to form the high definition final image from the primary image, and a control unit 240 having a decoding function to allow determining whether to decode or not the filtered image data by receiving the signal having completed the filtering process in the image processing unit 230 and also having a determining function to determine the decoding data in accordance with the result of decoding by the decoding function by filtering the image data using a plurality of image recovery filters in the filtering process function of the image processing unit 230. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an information code reading apparatus using an image sensor and having an optical system, and a method thereof.

In response to the digitization of information, which has been rapidly developing in recent years, the response in the video field is also remarkable.
In particular, as symbolized by a digital camera, the imaging surface is changed to a film, and a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) sensor, which is a solid-state imaging device, is used in most cases.

  As described above, an imaging lens device using a CCD or CMOS sensor as an imaging element is for taking an image of a subject optically by an optical system and extracting it as an electrical signal by the imaging element. In addition to a digital still camera, It is used in information code reading devices (bar code readers), video cameras, digital video units, personal computers, mobile phones, personal digital assistants (PDAs), image inspection devices, automatic control industrial cameras, and the like.

FIG. 32 is a diagram schematically illustrating a configuration and a light flux state of a general imaging lens device.
The imaging lens device 1 includes an optical system 2 and an imaging element 3 such as a CCD or CMOS sensor.
In the optical system, the object side lenses 21 and 22, the diaphragm 23, and the imaging lens 24 are sequentially arranged from the object side (OBJS) toward the image sensor 3 side.

In the imaging lens device 1, as shown in FIG. 32, the best focus surface is matched with the imaging device surface.
33A to 33C show spot images on the light receiving surface of the imaging element 3 of the imaging lens device 1.

By the way, when a lens with a bright F value is defocused from the in-focus position, the modulation transfer function (MTF: Modulation Transfer Function) is suddenly lowered. As a result, the MTF falls to 0 and a so-called bounce having a value again at a high frequency occurs.
Since the phase is shifted beyond this bounce point, the resolution is lost.
If the F value is reduced, the change in MTF at the time of defocusing can be kept low, so that the defocus range that does not bounce can be widened. This is a method of increasing the depth of field by reducing the F value.

For example, as a depth extension technique for a barcode reader, the depth of field is expanded by narrowing the F value as described above to achieve a fixed focus.
Focusing increases the shooting distance but requires a complicated mechanism. Therefore, there is no problem that has an autofocus mechanism due to a problem of reliability of impact resistance, durability, or immediacy. That is, the barcode reader uses a fixed focus lens from the viewpoint of reliability.
However, if the F value is reduced, the light energy incident on the image sensor is reduced, so that there is a problem that the sensitivity is lowered, noise increases, and barcode decoding fails.
Therefore, in the barcode reader, the depth of field is determined by balancing the shooting distance of the product specification and the F value.

In addition, imaging devices have been proposed in which light beams are regularly dispersed by a phase plate and restored by digital processing to enable imaging with a deep depth of field (for example, Non-Patent Documents 1 and 2 and Patent Documents). 1-5).
If this method is used, the F-number remains bright and the depth of field can be extended.
“Wavefront Coding; jointly optimized optical and digital imaging systems”, Edward R. Dowski, Jr., Robert H. Cormack, Scott D. Sarama. “Wavefront Coding; A modern method of achieving high performance and / or low cost imaging systems”, Edward R. Dowski, Jr., Gregory E. Johnson. USP 6,021,005 USP 6,642,504 USP 6,525,302 USP 6,069,738 JP 2003-235794 A

  However, although the limit distance of the depth of field obtained by the aperture is limited so that the bounce of the MTF does not decrease to a low frequency due to the aperture effect, the MTF itself is low and the decoding accuracy is lowered. Therefore, the reliability of decoding is lowered at a position near the depth of field.

In addition, the system using the phase modulation element described in each of the above-described documents has an advantage that even if the F value is bright, bounce can be suppressed as much as possible and a wide depth can be obtained.
However, even if an attempt is made to suppress the change in the PSF as much as possible with respect to the in-focus position, it cannot be made exactly the same, and the shape of the PSF has changed compared to the in-focus position at the marginal depth, and the difference is the restored image. Deterioration. There is a disadvantage that the reliability of the decoding is lowered at the last minute depth.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an information code reading apparatus and method that can increase the success rate of decoding of an information code and can improve the decoding reliability.

  According to a first aspect of the present invention, an optical system, an image sensor that captures an image of an information code that is a subject that has passed through the optical system, and a plurality of point spread functions according to the distance between the optical system and the subject ( A plurality of image restoration filters prepared in advance for each PSF), filter means for filtering the image data output from the image sensor by the image restoration filter, and the image data on which the filtering has been performed Decoding means including determination of whether or not the information code can be decoded, and causing the filter means to filter the image data with the plurality of image restoration filters, and decoding data indicating a result of the decoding means that is permitted in the decoding possibility determination Output as.

  Preferably, a predetermined number of times of image acquisition are performed for the same information code, and the final decoding result is adopted when the predetermined number of times or more is obtained in the determination of whether or not decoding is possible.

  Preferably, the type of the restoration filter for which a result that is acceptable in the determination as to whether or not decoding is possible is stored, and the type that is stored when the determination as to whether or not decoding is possible in the next information code reading is performed. The restoration filter is preferentially used.

  Preferably, the optical system includes an optical wavefront modulation function for modulating an optical transfer function (OTF).

  Preferably, the optical system includes a light wavefront modulation element or a light wavefront modulation surface formed on the optical element forming the optical system.

  Preferably, the image processing apparatus includes storage means for storing the restoration filter, and the value of the restoration filter can be changed for each individual optical system or for each required distance between the optical system and the subject.

Preferably, the plurality of restoration filters are generated by changing the coefficient of the Wiener filter so that the following filter gain FG values are substantially equal.
FG = (1 / a * ΣΣfilt (u, v) ^ 2) ^ 0.5
a is the total number of elements in the filter

  Preferably, the plurality of restoration filters are set to have a higher filter gain as the distance between the plurality of restoration filters corresponds to the subject distance away from the focus center than to the distance corresponding to the subject distance as the focus center of the optical system. Has been.

  Preferably, the determination of whether or not decoding is possible is also linked in accordance with the level of the filter gain of the plurality of restoration filters.

  According to a second aspect of the present invention, there is provided an information code reading method in which an image of an information code, which is a subject that has passed through an optical system, is picked up by an image sensor and the information code is read, and the distance between the optical system and the subject is determined. The image data output from the image sensor is filtered by a plurality of image restoration filters prepared in advance for each of a plurality of corresponding point spread functions (PSFs), and the information is applied to the image data subjected to the filtering A determination is made as to whether or not the code can be decoded, and the result determined by the determination as to whether or not the code can be decoded is adopted as decoded data.

  According to the present invention, it is possible to increase the success rate of decoding information codes, and to improve the reliability of decoding.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is an external view showing an example of an information code reading apparatus according to an embodiment of the present invention.
2A to 2C are diagrams illustrating examples of information codes.
FIG. 3 is a block diagram illustrating a configuration example of an imaging apparatus applied to the information code reading apparatus of FIG.

As shown in FIG. 1, the information code reader 100 according to the present embodiment has a main body 110 connected to a processing device such as an electronic register (not shown) via a cable 111, for example, a reflectance printed on a reading object 120. It is a device that can read the information code 121 such as a different symbol or code.
When the reading start switch 112 formed on the main body 110 is operated, the information code reading device 100 uses the trigger as a trigger to read the information code, for example, 10 times, and if it can be determined by 7 decoding determinations, It has a function of decoding results.
The reason for having this function is that considering the ease of use of the user, it is assumed that the state where the information cannot be read with respect to disturbance or weak information will continue if the decoding determination is enabled once. It is. By the way, it is configured so that the setting of seven times of this retry can be changed.

  As an information code to be read, for example, a one-dimensional bar code 122 such as a JAN code as shown in FIG. 2A, a stack-type CODE 49 as shown in FIGS. 2B and 2C, Alternatively, a two-dimensional barcode 123 such as a matrix type QR code can be used.

  In the information code reading apparatus 100 according to the present embodiment, an illumination light source (not shown) and an imaging apparatus 200 as shown in FIG.

  As shown in FIG. 3, the imaging apparatus 200 of the information code reading apparatus 100 includes an optical system 210, an imaging element 220, an image processing apparatus 230 including a function as a filter unit, a control unit including functions as a decoding unit and a determination unit. 240, and an external interface unit (I / F) 250.

The optical system 210 supplies an image obtained by photographing the information code 121 that is the subject object OBJ to the image sensor 220.
As the optical system 210, for example, a fixed focus lens is used.

The image sensor 220 forms an image captured by the optical system 210, and forms an image primary image information as a primary image signal FIM of an electrical signal via an analog front end unit (AFE) (not shown). It consists of a CCD or CMOS sensor that outputs to.
In FIG. 3, the imaging element 220 is described as a CCD as an example.

The image processing device 230 receives a digital signal of a captured image coming from an AFE (not shown) at the previous stage, performs a two-dimensional convolution process, and outputs the convolution process to the control device 240 at the subsequent stage.
The image processing device 230 uses a plurality of image restoration filters prepared in advance for each of a plurality of point spread functions (PSFs) corresponding to the distance between the optical system 210 and the subject to perform image data output from the image sensor 220. And a function of performing filtering by the image restoration filter.
For example, a distance of 125 mm, 100 mm, 88 mm, or the like is selected as the distance between the optical system 210 and the subject, and an image restoration filter is prepared in advance for each of a plurality of point spread functions (PSFs) corresponding to these distances.

The image processing device 230 has a storage unit that is provided in or outside, for example, a non-volatile memory, and an image restoration filter is stored in the storage unit.
The image restoration filter stored in the storage unit is configured to be able to change the value of the image restoration filter for each individual optical system 210 or for each required subject distance.

  The plurality of image restoration filters are generated by changing the coefficient of the Wiener filter so that the filter gain FG values shown below are substantially equal.

[Equation 1]
FG = (1 / a * ΣΣfilt (u, v) ^ 2) ^ 0.5
a is the total number of elements in the filter

  Further, the plurality of image restoration filters are set so that the filter gain becomes higher as the number of the image restoration filters corresponds to the subject distance away from the focus center than the one corresponding to the subject distance at the focus center of the optical system 210. .

4A to 4C are diagrams showing the relationship between the filter gain FG and the RMS of the MTF.
As shown in FIG. 4A, before the filtering process, as shown in FIG. 4A, the top of the MTF is at the best focus position, and the MTF decreases as the defocus amount increases.
Therefore, after the filtering process, the filtering process is performed so that the MTF on the defocus side is increased and the difference from the best focus side is decreased to make the MTF uniform.
For this reason, as shown in FIG. 4C, the filter gain is higher as the distance to the subject is farther from the focus center than to the distance from the focus center of the optical system 210. Is set.
By applying a filter process having characteristics as shown in FIG. 4C, an RMS of the MTF as shown in FIG. 4B can be obtained.

As shown in FIGS. 5A and 5B, if the filter gain FG is increased, the MTF can be increased, but the noise amount is increased accordingly.
That is, when focusing only on the restoration filter, changing the restoration level is related to the resolution and noise of the restored image. That is, when a strong restoration filter is used, the resolution increases and the noise also increases. A certain amount of noise can be avoided by correction processing or the like when determining the information code, but there is a limit (this corresponding configuration and function will be described later). At the same time, it is possible to determine if the resolution has a certain resolution.

The control device 240 controls communication with the host device (for example, an electronic register) via the image processing device 230 and the interface unit 250, and controls arbitration control of the entire system.
The control device 240 receives a signal subjected to the filter processing in the image processing device 230, and performs a decoding function for determining whether or not the information code can be decoded with respect to the filtered image data, and a filter processing function of the image processing device 230 The image data is filtered by a plurality of image restoration filters, and a determination function for determining the result that is permitted in the decode function determination (hereinafter also referred to as “decode determination”) as the decode data is provided.
Note that the decoding capability determination of the decoding function refers to determining whether it can be determined as an information code from the filtered image data.

  Then, the control device 240 performs control such as transmitting image data (decoded information) whose decoding is permitted to the host device via the interface unit 250, for example.

FIG. 6 is a flowchart for explaining a basic process of the decoding determination process for the read information code in the control device according to the present embodiment.
In this example, three distances such as 125 mm, 100 mm, and 88 mm are selected as the distance between the optical system 210 and the subject, and prepared in advance for each of a plurality of point spread functions (PSFs) corresponding to these distances. Assume that three image restoration filters F1, F2, and F3 are used.

When the reading start switch 112 formed on the main body 110 is operated, reading of the information code is started by using the switch as a trigger, and the captured image data is input to the image processing device 230.
Here, a decoding determination process is performed in the control device 240.
First, in the control device 240, an instruction is issued to the image processing device 230 so as to perform filtering by the filter F1, and accordingly, an image restoration process is performed on the read data by the filter F1 (ST1). The restored image data is supplied to the control device 240.
The control device 240 determines whether or not it can be determined as an information code from the image data filtered by the filter F1 (ST2). If it is determined in step ST2 that determination is possible, it is determined that decoding is possible (decoding OK) (ST8).
If it is determined in step ST2 that decoding is not possible (decoding NG), an instruction is issued to the image processing device 230 to perform filtering with the filter F2, and an image restoration process is performed on the read data with the filter F2. (ST3). The restored image data is supplied to the control device 240.
The control device 240 determines whether or not it can be determined as an information code from the image data filtered by the filter F2 (ST4). If it is determined in step ST4 that determination is possible, it is assumed that decoding is OK (ST8).
If it is determined in step ST4 that decoding is impossible, an instruction is issued to the image processing device 230 to perform filtering by the filter F3, and an image restoration process is performed on the read data by the filter F3 (ST5). The restored image data is supplied to the control device 240.
In control device 240, it is determined whether or not it can be determined as an information code from the image data filtered by filter F3 (ST6). If it is determined in step ST4 that determination is possible, it is assumed that decoding is OK (ST8).
If it is determined in step ST6 that decoding is impossible, it is determined that decoding using three filters is impossible (ST7).

The basic process of the information code decoding determination process of the control device 240 has been described above. According to this basic processing, the success rate of decoding of the information code can be increased, and as a result, the reliability of decoding can be improved.
In this way, a plurality of image restoration filters corresponding to the shooting distance are prepared and tested in order, and whether the decoding result is OK is repeated. This result may be the final decoding result, or may be statistically determined to pass more than a predetermined pass determination from a plurality of combinations.

  In the determination function of the control device 240 according to the present embodiment, for example, when the image data is acquired a predetermined number of times for the same information code and the decoding function determines whether or not a certain number of times is possible in the decoding function, the final determination is performed. It can be configured to be adopted as a typical decoding result.

  FIG. 7 is a flowchart showing a process for obtaining a final decoding result when the determination of whether or not decoding is possible becomes possible for a certain number of times or more.

In the processing of FIG. 7, when the reading start switch 112 formed on the main body 110 is operated, reading of the information code is started using this as a trigger, and the captured image data is input to the image processing device 230.
Here, a decoding determination process is performed in the control device 240.
First, in the control device 240, an instruction is issued to the image processing device 230 so as to perform filtering by the filter F1, and accordingly, an image restoration process is performed on the read data by the filter F1 (ST11).
This information reading and image restoration processing using the filter F1 are performed a predetermined number of times, for example, 10 times. These restored image data are supplied to the control device 240.
In the control device 240, it is determined whether or not it can be determined as an information code from each image data filtered by the filter F1. Then, the number of times determined to be determinable in this decoding determination process is held as data N1 (ST12, ST13).

Next, the control device 240 instructs the image processing device 230 to perform filtering with the filter F2, and accordingly, the image restoration processing is performed on the read data with the filter F2 (ST14).
This information reading and image restoration processing using the filter F2 are performed a predetermined number of times, for example, 10 times. These restored image data are supplied to the control device 240.
In the control device 240, it is determined whether or not it can be determined as an information code from each image data filtered by the filter F2. The number of times determined to be determinable in this decoding determination process is held as data N2 (ST15, ST16).

Next, in the control device 240, an instruction is given to the image processing device 230 so as to perform filtering with the filter F3, and accordingly, image restoration processing is performed on the read data with the filter F3 (ST17).
This information reading and image restoration processing using the filter F3 are performed a predetermined number of times, for example, 10 times. These restored image data are supplied to the control device 240.
In the control device 240, it is determined whether or not it can be determined as an information code from each image data filtered by the filter F3. The number of times determined to be determinable by this decoding determination process is held as data N3 (ST18, ST19).

As described above, the largest one of the number of times N1, N2, and N3 determined to be determinable obtained by performing the image reading and image restoration processing using the three filters F1, F2, and F3 a plurality of times It is determined whether or not the set number of OK times (the number of times decoding can be determined, threshold), for example, 7 times or more is OK (ST20).
If the number of times is equal to or greater than the preset number of times, it is assumed that the decoding of the image data by the filter having the maximum number of times of OK is OK (ST21).
If it is determined in step ST20 that decoding is impossible, it is determined that decoding by all three filters is impossible (ST22).

As described above, in the determination function of the control device 240 according to the present embodiment, for example, when image data is acquired a predetermined number of times for the same information code and the decoding function determines whether or not a certain number of times is possible in the decoding function. The processing that is adopted as the final decoding result has been described.
According to this process, the reliability of decoding can be further improved as compared with the basic process of FIG.

  Further, in the determination function of the control device 240 according to the present embodiment, for example, the type of the image restoration filter that has obtained a result that can be determined by the determination of whether or not decoding is possible is stored, and the determination of whether or not decoding is possible is performed at the next information code reading. In this case, it is possible to preferentially use the stored type of restoration filter.

  FIG. 8 is a flowchart showing processing for preferentially using the stored type of restoration filter.

When the reading start switch 112 formed on the main body 110 is operated, reading of the information code is started by using the switch as a trigger, and the captured image data is input to the image processing device 230.
Here, a decoding determination process is performed in the control device 240.
First, the control device 240 instructs the image processing device 230 to perform filtering with a filter X (in this example, X can be 2 and 3 with an initial value of 1). An image restoration process is performed on the read data at ST31 (ST31). The restored image data is supplied to the control device 240.
In control device 240, whether or not it can be determined as an information code from the image data filtered by filter X (here X = 1, for example, corresponding to filter F1 in FIG. 6) is decoded (ST32). If it is determined in step ST32 that determination is possible, it is assumed that decoding is OK (ST41).

If it is determined in step ST32 that decoding is impossible, 1 is added to X (ST33), and X is set to 1 if X is larger than 3. The image processing device 230 is instructed to perform filtering with the filter X (for example, corresponding to the filter F2 in FIG. 6), and an image restoration process is performed on the read data with the filter X (ST34). The restored image data is supplied to the control device 240.
In control device 240, it is decoded and determined whether or not it can be determined as an information code from image data filtered by filter X (here X = 2, for example, corresponding to filter F2 in FIG. 6) (ST35). If it is determined in step ST35 that determination is possible, it is assumed that decoding is OK (ST41).

If it is determined in step ST35 that decoding is impossible, 1 is added to X (ST36), and X is set to 1 if X is larger than 3. The image processing device 230 is instructed to perform filtering with the filter X (for example, corresponding to the filter F3 in FIG. 6), and an image restoration process is performed on the read data with the filter X (ST37). The restored image data is supplied to the control device 240.
The control device 240 determines whether or not it can be determined as an information code from the image data filtered by the filter X (here X = 3, for example, corresponding to the filter F3 in FIG. 6) (ST38). If it is determined in step ST38 that determination is possible, it is assumed that decoding is OK (ST41).
If it is determined in step ST38 that decoding is impossible, 1 is added to X (ST39), and X is set to 1 if X is larger than 3. Then, it is determined that decoding by all three filters is impossible (ST40).

  In the above processing, the initial value of the filter X can be any one of 1 to 3, and when x + 1 is 4, processing for returning X to 1 is performed.

  As described above, when determining whether decoding is possible in the next reading of the information code, it is configured to use the stored type of restoration filter preferentially, so that information can be obtained more accurately and quickly with high quality. The code can be read.

  Further, for example, a method of adopting a method in which, for example, the filter that can be decoded last is given the first priority, and the filter corresponding to the subject distance at the center of the focus of the optical system is given the second priority. Therefore, versatility can be improved.

  Furthermore, in the determination function of the control device 240 according to the present embodiment, for example, in the determination of whether or not decoding is possible, it is possible to link the noise determination of the determination of whether or not decoding is possible according to the level of the filter gain FG of the plurality of restoration filters It is.

  9A to 9C are diagrams showing the relationship between the noise determination threshold value NVTH and the noise level NLVL before and after the filter processing according to the present embodiment.

  When the decoding noise determination threshold is constant, the noise is increased when the amount of focus is large by the restoration filter, and exceeds the noise determination threshold. Since we want to determine the noise increased by the restoration filter according to the difference in the filter, set the noise judgment threshold in proportion to the change of the filter gain so that the noise judgment will not be affected even if the filter is changed. Constitute.

When the defocus amount is large from the in-focus position, the blur amount increases and the contrast decreases. Therefore, a restoration filter with a large defocus increases the filter gain and increases the contrast as much as possible.
However, as shown in FIGS. 5A and 5B, noise also increases as the filter gain increases. Therefore, if the noise judgment at the time of decoding is the same, restoration with a filter having a high filter gain will cause noise level to be restored. Exceeds the determination threshold, and decoding becomes impossible.
Therefore, when a filter with a high filter gain is applied, as shown in FIG. 9C, defocusing is performed by increasing the noise determination threshold value NVTH in a direction in which decoding is possible (OK) even when the noise level NLVL is high. While it is possible to increase the contrast even at a large distance, it is possible to expand the decoding determination range regardless of noise determination.

10A to 10C show images before and after image restoration filter processing when the distance between the optical system and the information code as the subject is 125 mm, 100 mm, and 88 mm by the information code reader 100 according to the present embodiment. FIG.
In this example, the focus is on the 125 mm image, but this is only an example, and the present invention is not limited to this.
According to the information code reading apparatus 100 of the present embodiment, as shown in FIGS. 10A to 10C, even if blurred image data is captured, decoding is performed by using an image restoration filter corresponding to the distance. It is possible to perform a good restoration process so that decoding can be performed based on the availability determination.
As shown in FIG. 10C, the image after the image restoration filter processing in the case of the distance between the optical system that is the most blurred and the information code that is the subject is good so that it can be decoded by determining whether or not decoding is possible. Can be restored.

The case where a normal lens optical system is used has been described above.
Hereinafter, as a preferred embodiment, a configuration in which the optical system includes an optical wavefront modulation function for modulating an optical transfer function (OTF), and the depth of field can be extended by effectively using a determinable range; The function will be described.
The light wavefront modulation function can be provided by arranging a light wavefront modulation element in the optical system or including a light wavefront modulation surface formed in the optical element forming the optical system.
Hereinafter, a case where an optical wavefront modulation element is applied will be described as an example.

  In the imaging apparatus 200A shown in FIG. 11 according to this embodiment, a light wavefront modulation element is applied to the optical system 210A, the light flux is regularly dispersed by the light wavefront modulation element, restored by digital processing, and the depth of field is deep. A wavefront aberration control optical system system or a depth expansion optical system (DEOS) system that enables image capturing is adopted, and the information code is determined according to the distance between the optical system 210A and the subject (information code). Therefore, it can be read with high accuracy.

  The imaging apparatus 200A shown in FIG. 11 is different from the imaging apparatus 200 of FIG. 3 in the configuration of the optical system 210A and the function of the image processing apparatus 230A. The configuration and functions described in association with FIGS. In the same way, the following description will focus on the different DEOS portions.

  FIG. 12 is a diagram schematically illustrating a configuration example of an optical system 210A including the light wavefront modulation element according to the present embodiment.

  An optical system 210A in FIG. 12 is disposed between an object side lens 211 disposed on the object side OBJS, an image forming lens 212 for forming an image on the image sensor 220, and between the object side lens 211 and the image forming lens 212. A wavefront modulation element (wavefront forming optical element) group 213 made of, for example, a phase plate 213a having a three-dimensional curved surface, which deforms a wavefront of an image formed on the light receiving surface of the imaging element 220 by the imaging lens 212 is provided.

In the present embodiment, the case where the phase plate is used has been described. However, the optical wavefront modulation element of the present invention may be any element that deforms the wavefront, and an optical element whose thickness changes. (For example, the above-mentioned third-order phase plate), an optical element whose refractive index changes (for example, a gradient index wavefront modulation lens), an optical element whose thickness and refractive index change due to coding on the lens surface (for example, a wavefront) A light wavefront modulation element such as a modulation hybrid lens or a phase plane formed on the lens surface) or a liquid crystal element capable of modulating the phase distribution of light (for example, a liquid crystal spatial phase modulation element). .
Further, in the present embodiment, the case where a regularly dispersed image is formed using a phase plate that is a light wavefront modulation element has been described. However, the lens used as a normal optical system has the same rule as the light wavefront modulation element. When an image that can form a dispersed image is selected, it can be realized only by an optical system without using a light wavefront modulation element. In this case, it does not correspond to the dispersion caused by the phase plate described later, but corresponds to the dispersion caused by the optical system.

The optical system 210A in FIG. 12 is an example in which an optical phase plate 213a is inserted.
The phase plate 213a shown in the figure is an optical lens that regularly disperses the light beam converged by the optical system. By inserting this phase plate, an image that does not fit anywhere on the image sensor 220 is realized.
In other words, the phase plate 213a forms a deep luminous flux (which plays a central role in image formation) and a flare (blurred portion).
As described above, means for restoring the regularly dispersed image to a focused image without moving the optical system 210A by digital processing is a wavefront aberration control optical system system or a depth extension optical system system (DEOS). : Depth Expansion Optical system), and this processing is performed in the image processing apparatus 230A.

  Hereinafter, the principle of the DEOS of the present embodiment, the optical system, and the configuration and function of the image processing apparatus will be specifically described.

First, the basic principle of DEOS will be described.
As shown in FIG. 13, when the subject image f enters the DEOS optical system H, a g image is generated.
This is expressed by the following equation.

[Equation 2]
g = H * f
However, * represents convolution.

  In order to obtain the subject from the generated image, the following processing is required.

[Equation 3]
f = H ^-1 * g

Here, the kernel size and calculation coefficient regarding H will be described.
The optical switching information is KPn, KPn-1,. In addition, each H function is defined as Hn, Hn-1,.
Since each spot image is different, each H function is as follows.

The difference in the number of rows and / or the number of columns in this matrix is the kernel size, and each number is the operation coefficient.
Here, each H function may be stored in a memory, and the PSF is set as a function of the object distance, and is calculated based on the object distance. By calculating the H function, an optimum object distance is obtained. It may be possible to set so as to create a filter. Alternatively, the H function may be directly obtained from the object distance using the H function as a function of the object distance.

  In the present embodiment, as shown in FIG. 12, an image from the optical system 210A is received by the image sensor 220 and input to the image processing device 230A when the aperture is opened, and a conversion coefficient corresponding to the optical system is acquired. The image signal having no dispersion is generated from the dispersion image signal from the image sensor 220 with the acquired conversion coefficient.

  In the present embodiment, as described above, dispersion means that, by inserting the phase plate 213a, an image that does not fit anywhere on the image sensor 220 is formed, and the phase plate 213a has a deep light flux ( It plays a central role in image formation) and a phenomenon of forming flare (blurred portion), and includes the same meaning as aberration because of the behavior of the image being dispersed to form a blurred portion. Therefore, in this embodiment, it may be described as aberration.

In the present embodiment, DEOS can be employed to obtain high-definition image quality, and the optical system can be simplified and the cost can be reduced.
Hereinafter, this feature will be described.

14A to 14C show spot images on the light receiving surface of the image sensor 220. FIG.
14A shows a case where the focal point is shifted by 0.2 mm (Defocus = 0.2 mm), FIG. 14B shows a case where the focal point is a focal point (Best focus), and FIG. 14C shows a case where the focal point is shifted by −0.2 mm. In this case, each spot image is shown (Defocus = −0.2 mm).
As can be seen from FIGS. 14A to 14C, in the imaging apparatus 200A according to the present embodiment, a light beam having a deep depth (a central role of image formation) is generated by the wavefront forming optical element group 213 including the phase plate 213a. And flare (blurred part) are formed.

  Thus, the primary image FIM formed in the imaging apparatus 200A of the present embodiment has a light beam condition with a very deep depth.

FIGS. 15A and 15B are diagrams for explaining a modulation transfer function (MTF) of a primary image formed by the imaging lens device according to the present embodiment. FIG. 15A is a diagram showing a spot image on the light receiving surface of the imaging element of the imaging lens device, and FIG. 15B shows the MTF characteristics with respect to the spatial frequency.
In the present embodiment, the high-definition final image is left to the correction processing of the image processing device 230 including a digital signal processor (Digital Signal Processor), for example, as shown in FIGS. 15A and 15B. The MTF of the primary image is essentially a low value.

  As described above, the image processing apparatus 230A receives the primary image FIM from the image sensor 220, performs a so-called predetermined correction process for raising the MTF at the spatial frequency of the primary image, and forms a high-definition final image FNLIM. To do.

The MTF correction processing of the image processing device 230A is performed after edge enhancement, chroma enhancement, etc., using the MTF of the primary image, which is essentially a low value, as shown by the curve A in FIG. In the process, correction is performed so as to approach (reach) the characteristic indicated by the curve B in FIG.
A characteristic indicated by a curve B in FIG. 16 is a characteristic obtained when the wavefront is not deformed without using the wavefront forming optical element as in the present embodiment, for example.
It should be noted that all corrections in the present embodiment are based on spatial frequency parameters.

In the present embodiment, as shown in FIG. 16, in order to achieve the MTF characteristic curve B that is finally realized with respect to the optically obtained MTF characteristic curve A with respect to the spatial frequency, each spatial frequency is changed to each spatial frequency. On the other hand, as shown in FIG. 17, strength such as edge enhancement is added, and the original image (primary image) is corrected.
For example, in the case of the MTF characteristic of FIG. 16, the curve of edge enhancement with respect to the spatial frequency is as shown in FIG.

  That is, a desired MTF characteristic curve B is virtually realized by performing correction by weakening edge enhancement on the low frequency side and high frequency side within a predetermined spatial frequency band and strengthening edge enhancement in the intermediate frequency region. To do.

As described above, the imaging apparatus 200A according to the embodiment basically includes the optical system 210A and the imaging element 220 that form a primary image, and the image processing apparatus 230A that forms the primary image into a high-definition final image. In the optical system, a wavefront shaping optical element is newly provided, or an optical element such as glass, plastic or the like is formed for wavefront shaping, thereby forming an imaging wavefront. The wavefront is deformed (modulated), and such a wavefront is imaged on the imaging surface (light-receiving surface) of the imaging element 220 including a CCD or CMOS sensor, and the imaged primary image is obtained through the image processing device 230A. An image forming system.
In the present embodiment, the primary image from the image sensor 220 has a light flux condition with a very deep depth. For this reason, the MTF of the primary image is essentially a low value, and the MTF is corrected by the image processing device 230A.

Here, the imaging process in the imaging apparatus 200 </ b> A according to the present embodiment will be considered in terms of wave optics.
A spherical wave diverging from one of the object points becomes a convergent wave after passing through the imaging optical system. At that time, aberration occurs if the imaging optical system is not an ideal optical system. The wavefront is not a spherical surface but a complicated shape. Wavefront optics lies between geometric optics and wave optics, which is convenient when dealing with wavefront phenomena.
When dealing with the wave optical MTF on the imaging plane, the wavefront information at the exit pupil position of the imaging optical system is important.
The MTF is calculated by Fourier transform of the wave optical intensity distribution at the imaging point. The wave optical intensity distribution is obtained by squaring the wave optical amplitude distribution, and the wave optical amplitude distribution is obtained from the Fourier transform of the pupil function in the exit pupil.
Further, since the pupil function is exactly from the wavefront information (wavefront aberration) at the exit pupil position itself, the MTF can be calculated if the wavefront aberration can be strictly calculated numerically through the optical system 210A.

Accordingly, if the wavefront information at the exit pupil position is modified by a predetermined method, the MTF value on the imaging plane can be arbitrarily changed.
In this embodiment, the wavefront shape is mainly changed by the wavefront forming optical element, but the target wavefront is formed by increasing or decreasing the phase (phase, optical path length along the light beam). .
Then, if the desired wavefront formation is performed, the light flux emitted from the exit pupil is from the dense and sparse portions of the light, as can be seen from the geometric optical spot images shown in FIGS. It is formed.
The MTF in the luminous flux state shows a low value at a low spatial frequency and a characteristic that the resolving power is managed up to a high spatial frequency.
That is, if this MTF value is low (or such a spot image state in terms of geometrical optics), the phenomenon of aliasing will not occur.
That is, a low-pass filter is not necessary.
Then, the flare-like image that causes the MTF value to be lowered may be removed by the image processing device 230A composed of a DSP or the like at the subsequent stage. Thereby, the MTF value is significantly improved.

  Next, the response of the MTF of this embodiment and the conventional optical system will be considered.

FIG. 18 is a diagram showing the MTF response when the object is at the focal position and when the object is out of the focal position in the case of a general optical system.
FIG. 19 is a diagram showing the response of the MTF when the object is at the focal position and when the object is out of the focal position in the optical system of the present embodiment having the light wavefront modulation element.
FIG. 20 is a diagram illustrating a response of the MTF after data restoration of the imaging apparatus according to the present embodiment.

As can be seen from the figure, in the case of an optical system having a light wavefront modulation element, the change in the response of the MTF is less than that in an optical system in which no light wavefront modulation element is inserted even when the object deviates from the focal position.
The image formed by this optical system is processed by a convolution filter, so that the MTF response is improved.

The absolute value (MTF) of the OTF of the optical system having the phase plate shown in FIG. 19 is preferably 0.1 or more at the Nyquist frequency.
This is because, in order to achieve the OTF after restoration shown in FIG. 20, the gain is increased by the restoration filter, but the noise of the sensor is also raised at the same time. For this reason, it is preferable to perform restoration without increasing the gain as much as possible at high frequencies near the Nyquist frequency.
In the case of a normal optical system, resolution is achieved if the MTF at the Nyquist frequency is 0.1 or more.
Therefore, if the MTF before restoration is 0.1 or more, the restoration filter does not need to increase the gain at the Nyquist frequency. If the MTF before restoration is less than 0.1, the restored image becomes an image greatly affected by noise, which is not preferable.

Next, the blurred image restoration process of the image processing apparatus 230A will be described.
FIG. 21 is an MTF (Modulation Transfer Function) characteristic diagram at the best focus position of a general optical system.
FIG. 22 is a diagram showing the MTF characteristics of the optical system of the present embodiment.

Since the picked-up image obtained by the image pickup element 220 after passing through the optical system 210A of the present embodiment is blurred, the MTF decreases from the middle range to the high range. This MTF is raised by calculation. In contrast to the MTF, which is the amplitude characteristic of a single lens, the total amplitude characteristic including image processing is called SFR (Spatial Frequency Response).
Since the frequency characteristic of a PSF that generates a blurred image is MTF, a blur restoration filter is designed to have a gain characteristic that is increased to a desired SFR characteristic. The degree of gain is determined by the balance with noise and false images.

  There are two methods for digitally filtering this blur restoration filter to the original image: Fourier transforming the image and multiplying the filter and frequency in the frequency domain, and convolution (convolution) in the spatial domain. is there. Here, the latter implementation method will be described. The convolution operation is expressed by the following equation.

Here, f indicates a filter kernel (here, the one rotated 180 degrees is used for easy calculation).
A indicates an original image, and B indicates a filtered image (blurred restored image).
As can be seen from this equation, f is superimposed on the image and the result of summing the products of the taps is taken as the value of the center coordinate that has been superimposed.

Next, a 3 * 3 filter will be specifically described with reference to FIGS. 23A to 23C.
The restoration filter of FIG. 23A (already rotated by 180 degrees) is overlaid with the filter center f (0,0) on A (i, j) of the blurred image shown in FIG. The product is taken and the nine total values are set as B (i, j) of the blurred restored image shown in FIG.
When (i, j) is scanned over the entire image, a new B image is generated. This is a digital filter. Here, since the filter is used for blur restoration, blur restoration processing can be performed by performing this processing.

Next, the configuration and processing of the image processing device 230A will be described.
FIG. 24 is a block diagram illustrating a configuration example of the image processing apparatus according to the present embodiment.

  As shown in FIG. 24, the image processing device 230A includes a raw (RAW) buffer memory 231, a two-dimensional convolution operation unit 232, a kernel data storage ROM 233 as a storage unit, and a convolution control unit 234.

  The convolution control unit 234 controls the convolution process on / off, the screen size, the replacement of kernel data, and the like, and is controlled by the control device 240.

  In addition, the kernel data storage ROM 233 stores kernel data for convolution calculated by the PSF of each optical system prepared in advance as shown in FIG. 25, and a distance set in advance by the control device 240. The kernel data used for the filtering process is selectively controlled through the convolution control unit 234 according to the information.

  In the example of FIG. 25, the kernel data A is data corresponding to distance information of 125 mm, the kernel data B is data corresponding to distance information of 100 mm, and the kernel data C is data corresponding to distance information of 88 mm.

FIG. 26 is a flowchart of the switching process based on the distance information of the control device 240.
First, distance information is set and supplied to the convolution control unit 234 (ST101).
In the convolution control unit 234, the kernel size and the numerical operation coefficient are set in the register from the supplied information (ST102).
The image data captured by the image sensor 220 and input to the two-dimensional convolution calculation unit 232 is subjected to convolution calculation based on the data stored in the register, and the calculated and converted data is controlled. It is transferred to the device 240 (ST103).

  A more specific example of the signal processing device and kernel data storage ROM of the image processing device 230A will be described below.

FIG. 27 is a diagram illustrating a first configuration example of the signal processing device and the kernel data storage ROM.
The example of FIG. 27 is a block diagram when a filter kernel corresponding to acquired information is prepared in advance.

  The distance information is set, and the kernel data is selected and controlled through the convolution control unit 234. The two-dimensional convolution operation unit 232 performs convolution processing using kernel data.

FIG. 28 is a diagram illustrating a second configuration example of the signal processing device and the kernel data storage ROM.
The example of FIG. 28 is a block diagram in the case where the signal processing apparatus has a noise reduction filter processing step at the beginning, and noise reduction filter processing ST1 corresponding to distance information is prepared in advance as filter kernel data.

The distance information is set, and the kernel data is selected and controlled through the convolution control unit 234.
In the two-dimensional convolution operation unit 232, after performing the noise reduction filter process ST1, the color space is converted by the color conversion process ST2, and then the convolution process (OTF restoration filter process) ST3 is performed using the kernel data.
The noise reduction filter process ST4 is performed again, and the original color space is restored by the color conversion process ST5. The color conversion process includes, for example, YCbCr conversion, but other conversions may be used.
It is possible to omit the noise reduction filter process ST4 again.

FIG. 29 is a diagram illustrating a third configuration example of the signal processing device and the kernel data storage ROM.
The example of FIG. 29 is a block diagram when an OTF restoration filter corresponding to distance information is prepared in advance.

The distance information is set, and the kernel data is selected and controlled through the convolution control unit 234.
The two-dimensional convolution operation unit 232 performs the convolution process ST13 using the OTF restoration filter after the noise reduction filter process ST11 and the color conversion process ST12.
Noise reduction filter processing ST14 is performed again, and the original color space is restored by color conversion processing ST15. The color conversion process includes, for example, YCbCr conversion, but other conversions may be used.
Note that only one of the noise reduction filter processes ST11 and ST14 may be used.

FIG. 30 is a diagram illustrating a fourth configuration example of the signal processing device and the kernel data storage ROM. For simplification, AFE and the like are omitted.
The example of FIG. 30 is a block diagram in the case where a noise reduction filter processing step is included and a noise reduction filter corresponding to distance information is prepared in advance as filter kernel data.
It is possible to omit the noise reduction filter process ST24 again.
The type (characteristic) of the information code is acquired, and kernel data is selected and controlled through the convolution control unit 234.
In the two-dimensional convolution operation unit 232, after performing the noise reduction filter process ST21, the color space is converted by the color conversion process ST22, and then the convolution process ST23 is performed using the kernel data.
The noise reduction filter process ST24 corresponding to the distance information is performed again, and the original color space is restored by the color conversion process ST25. The color conversion process includes, for example, YCbCr conversion, but other conversions may be used.
The noise reduction filter process ST21 can be omitted.
The filter selection method described above is also effective in reading monochrome information codes.

  In the above, the example in which the filtering process is performed in the two-dimensional convolution calculation unit 232 according to the type (characteristic) information of the information code has been described. For example, a more suitable calculation coefficient is extracted or calculated based on the information code and subject distance information. Can be performed.

FIGS. 31A to 31C illustrate the case where the distance between the optical system and the information code as the subject is 125 mm, 100 mm, and 88 mm by the information code reader 100 having the imaging device of FIG. 11 according to the present embodiment. It is a figure which shows the image before and behind an image restoration filter process.
In this example, the focus is on the 125 mm image, but this is only an example, and the present invention is not limited to this.
According to the information code reading apparatus 100 of the present embodiment, as shown in FIGS. 31A to 31C, even if blurred image data is captured, decoding is performed by using an image restoration filter corresponding to the distance. It is possible to perform a better restoration process than in the case of FIGS. 10A to 10C so that decoding is possible in the availability determination.
In particular, as shown in FIG. 31 (C), so that the image after the image restoration filter processing in the case where the distance between the optical system that is the most blurred and the information code that is the subject is the image can be decoded by the decoding possibility determination. Since the fine pitch is better than in the case of FIG. 10C, a better restoration process can be performed.

  As described above, according to the present embodiment, the optical system 210 and the image sensor 220 including the light wavefront modulation element that forms the primary image, and the image processing device 230 that forms the primary image into a high-definition final image. A decoding function for receiving a signal subjected to the filtering process in the image processing device 230 and determining whether or not the information code can be decoded with respect to the filtered image data, and a filtering function of the image processing device 230. Since it has a control device 240 that includes a determination function for filtering image data with an image restoration filter and determining that the decoding function determines whether the decoding is possible or not as decoded data, the success rate of decoding the information code is increased. As a result, the reliability of decoding can be improved.

  Further, in the determination function of the control device 240, for example, when the image data is acquired a predetermined number of times for the same information code, and the decoding function determines whether or not the predetermined number of times is possible in the decoding function, the final decoding is performed. By adopting the configuration as a result, the reliability of decoding can be further improved.

  Further, in the determination function of the control device 240, for example, the type of the image restoration filter that has obtained a result that can be determined by the determination of whether or not decoding is possible is stored, and is stored when the determination of whether or not decoding is possible in the next information code reading is performed. By configuring so as to preferentially use the type of restoration filter, it is possible to read the information code more accurately and at high speed and with high quality.

  Further, in the determination function of the control device 240, for example, in the determination of whether or not decoding is possible, the determination of whether or not decoding is possible is linked in accordance with the level of the filter gain of the plurality of restoration filters, so that even at a large defocus distance. While the contrast can be increased, the decoding determination range can be expanded without being caught by noise determination.

In this embodiment, the imaging lens system having a wavefront forming optical element that deforms the wavefront of the imaging on the light receiving surface of the imaging element 220 by the imaging lens 212 and the primary image FIM by the imaging element 220 are received. In addition, the image processing apparatus 230A that forms a high-definition final image FNLIM by performing a predetermined correction process for so-called lifting of the MTF at the spatial frequency of the primary image and the like can be obtained. There is an advantage of becoming.
In addition, the configuration of the optical system 210A can be simplified, manufacturing becomes easy, and cost reduction can be achieved.

By the way, when a CCD or CMOS sensor is used as an image sensor, there is a resolution limit determined by the pixel pitch, and if the resolution of the optical system exceeds the limit resolution, a phenomenon such as aliasing occurs, which adversely affects the final image. It is a well-known fact that
In order to improve image quality, it is desirable to increase the contrast as much as possible, but this requires a high-performance lens system.

However, as described above, aliasing occurs when a CCD or CMOS sensor is used as an image sensor.
Currently, in order to avoid the occurrence of aliasing, the imaging lens apparatus uses a low-pass filter made of a uniaxial crystal system to avoid the occurrence of aliasing.
The use of a low-pass filter in this way is correct in principle, but the low-pass filter itself is made of crystal, so it is expensive and difficult to manage. Moreover, there is a disadvantage that the use of the optical system makes the optical system more complicated.

As described above, in order to form a high-definition image, the optical system must be complicated in the conventional imaging lens apparatus in spite of the demand for higher-definition image due to the trend of the times. . If it is complicated, manufacturing becomes difficult, and if an expensive low-pass filter is used, the cost increases.
However, according to this embodiment, the occurrence of aliasing can be avoided without using a low-pass filter, and high-definition image quality can be obtained.

  In this embodiment, the example in which the wavefront forming optical element of the optical system is arranged closer to the object side lens than the stop is shown. An effect can be obtained.

1 is an external view showing an example of an information code reading device according to an embodiment of the present invention. It is a figure which shows the example of an information code. It is a block which shows the structural example of the imaging device applied to the information code reader of FIG. It is a figure which shows the relationship between filter gain and RMS of MTF. It is a figure which shows that MTF can be made high when filter gain is made high, but noise amount also increases in connection with this. It is a flowchart for demonstrating the basic process of the decoding determination process of the read information code in the control apparatus which concerns on this embodiment. It is a flowchart which shows the process made into a final decoding result, when it becomes possible more than a fixed number of times by decoding decision | availability determination. It is a flowchart which shows the process which uses preferentially the kind of restoration filter which was memorized. It is a figure which shows the relationship between the noise determination threshold value NVTH before and behind the filter process which concerns on this embodiment, and the noise level NLVL. It is a figure which shows the image before and behind an image restoration filter process in case the distance of an optical system and the information code which is a to-be-photographed object is 125 mm, 100 mm, and 88 mm by the information code reading apparatus which concerns on this embodiment. It is a block diagram showing an example of composition of an imaging device which has an optical system containing a light wavefront modulation element concerning this embodiment. It is a figure which shows typically the structural example of 210 A of optical systems containing the optical wavefront modulation element concerning this embodiment. It is a figure for demonstrating the principle of DEOS. It is a figure which shows the spot image in the light-receiving surface of the image pick-up element which concerns on this embodiment, Comprising: (A) is a case where a focus shifts 0.2 mm (Defocus = 0.2 mm), (B) is a focus point ( Best focus), (C) is a diagram showing each spot image when the focal point is deviated by −0.2 mm (Defocus = −0.2 mm). It is a figure for demonstrating MTF of the primary image formed with the image sensor which concerns on this embodiment, Comprising: (A) is a figure which shows the spot image in the light-receiving surface of the image sensor of an imaging lens apparatus, (B ) Shows the MTF characteristics with respect to the spatial frequency. It is a figure for demonstrating the MTF correction process in the image processing apparatus which concerns on this embodiment. It is a figure for demonstrating concretely the MTF correction process in the image processing apparatus which concerns on this embodiment. It is a figure which shows the response (response) of MTF when an object exists in a focus position in the case of a general optical system, and it remove | deviates from a focus position. It is a figure which shows the response of MTF when an object exists in a focus position in the case of the optical system of this embodiment which has a light wavefront modulation element, and remove | deviates from a focus position. It is a figure which shows the response of MTF after the data restoration of the imaging device which concerns on this embodiment. It is a MTF (Modulation Transfer Function amplitude characteristic) characteristic view in the best focus (Best Focus) position of a general optical system. It is a figure which shows the MTF characteristic of the optical system of this embodiment. It is explanatory drawing of the blur decompression | restoration process in this embodiment. It is a block diagram which shows the structural example of the image processing apparatus which concerns on this embodiment. It is a figure which shows an example of the storage data of kernel data ROM. It is a flowchart which shows the outline | summary of the image process according to distance information. It is a figure which shows the 1st structural example about a signal processing apparatus and a kernel data storage ROM. It is a figure which shows the 2nd structural example about a signal processing apparatus and kernel data storage ROM. It is a figure which shows the 3rd structural example about a signal processing apparatus and kernel data storage ROM. It is a figure which shows the 4th structural example about a signal processing apparatus and kernel data storage ROM. FIG. 12 is a diagram showing images before and after image restoration filter processing when the distance between the optical system and the information code as the subject is 125 mm, 100 mm, and 88 mm by the information code reader 100 having the imaging device of FIG. 11 according to the present embodiment. is there. It is a figure which shows typically the structure and light beam state of a general imaging lens apparatus. FIG. 33A is a diagram showing a spot image on the light receiving surface of the imaging element of the imaging lens device of FIG. 32, where FIG. 33A shows a case where the focal point is shifted by 0.2 mm (Defocus = 0.2 mm), and FIG. In the case (Best focus), (C) is a diagram showing each spot image when the focal point is shifted by -0.2 mm (Defocus = -0.2 mm).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Information code reading device, 121 ... Information code, 200 ... Imaging device, 210, 210A ... Optical system, 220 ... Imaging element, 230, 230A ... Image processing device, 240 ... Control device, 211 ... Object side lens, 212 ... Image forming lens, 213 ... Optical element for wavefront formation, 213a ... Phase plate (light wavefront modulation element), 232 ... Two Dimensional convolution operation unit, 233... Kernel data ROM, 234... Convolution control unit.

Claims (10)

Optical system,
An image sensor that captures an image of an information code that is a subject through the optical system;
A plurality of image restoration filters prepared in advance for each of a plurality of point spread functions (PSFs) according to the distance between the optical system and the subject;
Filter means for performing filtering by the image restoration filter on image data output from the image sensor;
Decoding means including a determination of whether or not the information code can be decoded for the filtered image data,
An information code reading device that causes the filter means to filter the image data with the plurality of image restoration filters and outputs a result that is determined by the decoding means as to whether or not decoding is possible as decoded data. The information code reader according to claim 1, wherein an image is acquired a predetermined number of times with respect to the same information code, and is adopted as a final decoding result when the predetermined number of times is permitted in the determination as to whether or not decoding is possible. The type of the restoration filter for which a result that is permitted by the decoding possibility determination is obtained is stored, and when the decoding possibility determination is performed in the next information code reading, the stored type of restoration filter is stored. The information code reader according to claim 1 or 2, wherein the information code reader is used preferentially. The optical system is
The information code reader according to claim 1, further comprising an optical wavefront modulation function for modulating an optical transfer function (OTF). The optical system is
The information code reading device according to claim 4, comprising: a light wavefront modulation element, or a light wavefront modulation surface formed on an optical element forming the optical system. Storing means for storing the restoration filter;
The information code reading device according to any one of claims 1 to 5, wherein the value of the restoration filter can be changed for each individual optical system or for each required distance between the optical system and a subject. The information code reading device according to any one of claims 1 to 6, wherein the plurality of restoration filters are generated by changing a coefficient of a Wiener filter so that a value of a filter gain FG shown below is substantially equal.
FG = (1 / a * ΣΣfilt (u, v) ^ 2) ^ 0.5
a is the total number of elements in the filter The plurality of restoration filters are:
8. The filter gain is set to be higher as the distance to the subject is farther from the center of the focus than to the distance to the subject that is the center of focus of the optical system. The information code reading device described in 1. The information code reading device according to claim 8, wherein the determination of whether or not decoding is possible is also linked in accordance with the level of the filter gain of the plurality of restoration filters. An information code reading method in which an image of an information code that is a subject that has passed through an optical system is picked up by an image sensor and the information code is read.
Filtering image data output from the image sensor with a plurality of image restoration filters prepared in advance for each of a plurality of point spread functions (PSFs) according to the distance between the optical system and the subject;
Determining whether or not the information code can be decoded with respect to the filtered image data,
An information code reading method that employs, as decode data, a result that is determined by the determination of whether or not decoding is possible.