Patent Publication Number: US-2002002410-A1

Title: Information acquisition method and apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-197585, filed Jun. 30, 2000, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002] The present invention relates to an information acquisition method and apparatus, which is capable of acquiring information such as characters, barcodes, marks, figures (images), or the like formed on a form using fluorescent ink which is excited upon being irradiated with ultraviolet light and emits visible light having a wavelength different from the irradiated ultraviolet light in, e.g., an optical character reader (to be referred to as an OCR hereinafter).  
       [0003] Conventionally, in order to read characters, marks or the like formed using fluorescent ink on a form by an OCR, a light source for emitting ultraviolet light, an optical filter for intercepting transmission of ultraviolet light and transmitting light emitted by the fluorescent ink upon being irradiated with the ultraviolet light, and a photosensor are provided in addition to a light source and photosensor originally equipped in the OCR, as disclosed by Jpn. Pat. Appln. KOKAI Publication No. 6-96298. In the OCR, characters, marks, or the like formed using the fluorescent ink are detected by detecting light transmitted through the optical filter by the photosensor such as a CCD (charge coupled device) or the like.  
       [0004] In this manner, upon detecting characters, marks, or the like formed on a form using fluorescent ink by the conventional OCR, the dedicated light source for emitting ultraviolet light, optical filter, and photosensor must be added, resulting in a complicated and bulky apparatus.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005] Accordingly, it is an object of the present invention to provide an information acquisition method and apparatus, which is capable of detecting characters, marks, or the like formed using fluorescent ink without using any special components such as a light source for emitting ultraviolet light, an optical filter for intercepting transmission of ultraviolet light, or the like, and acquiring information such as characters, barcodes, marks, figures (images), or the like formed on a form using fluorescent ink.  
       [0006] According to one aspect of the present invention, there is provided a method of acquiring information from a form on which the information is recorded using fluorescent ink, comprising the steps of: irradiating the form with light which is emitted by a white light source, the light containing near ultraviolet light; outputting an analogue signal according to an amount of light reflected by the form; converting the output analogue signal into a multi-level digital signal; detecting from the digital signal a reference level of the digital signal corresponding to a position of the form where no information is recorded; and comparing a level of the digital signal corresponding to the information recorded using fluorescent ink with the reference level, and binarizing the digital signal based on a result of the comparison to obtain image information.  
       [0007] According to another aspect of the present invention, there is provided an apparatus for acquiring information from a form on which the information is recorded using fluorescent ink, comprising: a white light source for irradiating the form with light containing near ultraviolet light; photoelectric conversion means for outputting an analogue signal according to an amount of light reflected by the form; A/D conversion means for converting the output analogue signal into a multi-level digital signal; reference level detection means for detecting from the digital signal a reference level of the digital signal corresponding to a position of the form where no information is recorded; and binarization means for comparing a level of the digital signal corresponding to the information recorded using fluorescent ink with the reference level, and binarizing the digital signal based on a result of the comparison to obtain image information.  
       [0008] According to still another aspect of the present invention, there is provided a character recognition apparatus for recognizing characters from a form on which the characters are recorded using fluorescent ink, comprising: a white light source for irradiating the form with light containing near ultraviolet light; photoelectric conversion means for outputting an analogue signal according to an amount of light reflected by the form; A/D conversion means for converting the output analogue signal into a multi-level digital signal; reference level detection means for detecting from the digital signal a reference level of the digital signal corresponding to a position of the form where no information is recorded; binarization means for comparing a level of the digital signal corresponding to the information recorded using fluorescent ink with the reference level, and binarizing the digital signal based on a result of the comparison to output image information; and recognizing means for recognizing the form as being recorded using the fluorescent ink based on the image information output from the binarization means.  
       [0009] According to still another aspect of the present invention, there is provided a character recognition apparatus for reading characters from a form on which the characters are recorded and recognizing the read character, comprising: determining means for determining whether or not one of a character and a mark is recorded on a form using the fluorescent ink; and rejecting the form in a case where the determining means determines that the one of the character and mark is recorded on the form using the fluorescent ink.  
       [0010] Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
     
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
     [0011] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.  
     [0012]FIG. 1 is a view for explaining processes in an embodiment of the present invention;  
     [0013]FIG. 2 is a view for explaining limit character recognition target areas with marks of the fluorescent ink;  
     [0014]FIG. 3 is a schematic view showing the arrangement of a scanner apparatus used in the embodiment of the present invention;  
     [0015]FIG. 4 is a view showing the arrangement of a color image sensor;  
     [0016]FIG. 5 is a block diagram showing the arrangement of a processing circuit in the embodiment of the present invention;  
     [0017]FIG. 6 is a flow chart for explaining an operation in the embodiment of the present invention;  
     [0018]FIG. 7 is a flow chart for explaining a detailed operation including steps for the fluorescent ink detection;  
     [0019]FIG. 8 is a flow chart for explaining details of step S 5  in FIG. 7;  
     [0020]FIG. 9 is a graph showing the waveform of the output signal from a color image sensor before shading correction;  
     [0021]FIG. 10 is a graph showing the waveform of the output signal from a color image sensor after shading correction; and  
     [0022]FIG. 11 is a graph showing the white level of the sheet surface of a form. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0023] An embodiment of the present invention will be described hereinafter with reference to the accompanying drawings. The embodiment to be described below will exemplify a case wherein the present invention is applied to an OCR.  
     [0024] First, a numbering print technique and a technique of limiting character recognition target areas using fluorescent ink will be described below.  
     [0025] As shown in FIG. 1, characters written on a form are read by a form reading process  100 , and character recognition is executed by a character recognition process  110 . The printing for numbering is executed on the form that has been effected a character recognition process in order to differentiate from a form that is not yet effected a character recognition process. That is, conventional numbering print has executed onto vacant areas (i.e., plain areas where no character is written) of a form using a specific color (e.g., red), whereas in this embodiment, the printing for numbering is executed using colorless fluorescent ink by a numbering print process  120 . Such the numbering print using colorless fluorescent ink would not make the form dirty as an advantage.  
     [0026] However, the colorless fluorescent ink on the form is invisible to a human, resulting in a problem that it is not easy to determine whether or not each form has already been effected a character recognition process. This embodiment resolves the above problem.  
     [0027] Apart from the numbering print process, as shown in FIG. 2, it may be useful to limit character recognition target areas by printing, e.g., marks X of the fluorescent ink for one or more target lines to be read of a plurality of character lines on a form.  
     [0028]FIG. 3 is a schematic view of the mechanism of a scanner apparatus used in this embodiment. A scanner apparatus  10  shown in FIG. 3 is of a flatbed type, and has a housing  11  with a transparent glass  12  on which a form  18  to be read is placed, and a cover  13 . An optical head  14  is arranged inside the housing  11 , and moves along a rail  15  in the directions of arrows A and B by a driving motor such as a stepping motor (not shown), which is controlled by a control circuit (not shown).  
     [0029] The optical head  14  is provided with a white light source  16  for emitting visible light falling within the wavelength range from 400 nm to 700 nm, and a color image sensor  17 . Light emitted by the white light source  16  is reflected by the form  18  placed on the glass  12 , and is detected by the color image sensor  17  of the optical head  14 . The color image sensor  17  is provided as a photoelectric conversion means. As the white light source  16 , a light source used as that for a conventional OCR may be used. The white light source  16  also emits near ultraviolet light. The wavelength of near ultraviolet light emitted by the white light source  16  falls within the range from 400 nm to 450 nm.  
     [0030] As the color image sensor  17 , a commercially available CCD image sensor is used. The color image sensor  17  includes three line image sensors  171 ,  172 , and  173  for respectively detecting three primary color light components R, G, and B, as shown in FIG. 4.  
     [0031] The line image sensor  171  is formed by arranging a plurality of photodetection elements on one line. The line image sensor  171  detects a red (R) light component of incoming light reflected by the form  18 , and photoelectrically converts the detected red (R) light to output an output voltage (analog signal) corresponding to the detected red (R) light component.  
     [0032] The line image sensor  172  is formed by arranging a plurality of photodetection elements on one line. The line image sensor  172  detects a green (G) light component of incoming light reflected by the form  18 , and photoelectrically converts the detected green (G) light to output an output voltage (analog signal) corresponding to the detected green (G) light component.  
     [0033] The line image sensor  173  is formed by arranging a plurality of photodetection elements on one line. The line image sensor  173  detects a blue (B) light component of incoming light reflected by the form  18 , and photoelectrically converts the detected blue (B) light to output an output voltage (analog signal) corresponding to the detected blue (B) light component.  
     [0034] The line image sensor  171  includes an optical filter for transmitting red light alone to detect the red light. Likewise, the line sensor  172  includes an optical filter for transmitting green light alone. The line image sensor  173  includes an optical filter for transmitting blue light alone.  
     [0035] A white reference plate  19  is provided inside the housing  11 , and has a surface that opposes the optical head  14  and is painted in white. The white reference plate  19  is used for shading correction and white correction of an output voltage output from the color image sensor  17 .  
     [0036]FIG. 5 is a block diagram showing the arrangement of a processing circuit in this embodiment.  
     [0037] Upon receiving light reflected by the form  18 , the color image sensor  17  outputs to a signal processing circuit  30  output voltages (analog signals) obtained by detecting and photoelectrically converting red (R), green (G), and blue (B) color components in the reflected light. The signal processing circuit  30  has variable-gain amplifiers for amplifying input signals, and amplifies and outputs the output voltages (analog signals) input from the color image sensor  17  to an analog-to-digital conversion circuit (to be referred to as an A/D conversion circuit hereinafter)  31 . The signal processing circuit  30  implements shading correction and white correction of input voltages (analog signals) by controlling the gains of the amplifiers. Details of shading correction and white correction will be described later.  
     [0038] The A/D conversion circuit  31  converts the output voltages (analog signals) of red (R), green (G), and blue (B) color components input from the signal processing circuit  30  into digital data defined by 256 levels ranging from 0 to 255, and outputs the digital data to an image buffer memory  32 . The 256-level digital data can be expressed by an 8-bit signal.  
     [0039] The image buffer memory  32  stores digital data for one form output from the A/D conversion circuit  31  as form image data indicating an image of the form. An image processing unit  33  processes form image data stored in the image buffer memory  32 . The image processing unit  33  has a sheet surface white level detection circuit  331 , fluorescent ink detection circuit  332 , and binarization circuit  333 .  
     [0040] A character recognition unit  34  performs character recognition of a binary image obtained by binarizing the form image data stored in the image buffer memory  32  by the binarization circuit  333  in the image processing unit  33 , and outputs character codes as a recognition result.  
     [0041] It is to be noted that character recognition target areas may be limited on a form using fluorescent ink as shown in FIG. 2 and corresponding character recognition target lines may be identified on an image acquired from the fluorescent ink detection circuit  332 , so that only the binarized image of the character recognition target lines is recognized.  
     [0042] The character codes output from the character recognition unit  34  are recorded in a recording device such as an HDD (hard disk drive) or the like. A character recognition function of the character recognition unit  34  may be implemented using a conventional one.  
     [0043] The OCR in this embodiment includes the scanner apparatus for capturing an image of the form, and a character recognition apparatus for recognizing character images included in the form image output from the scanner apparatus. The OCR may be realized by arranging the scanner and character recognition apparatuses either in a single housing or in independent housings. The character recognition apparatus may be implemented as either a dedicated apparatus including dedicated circuits or a program (software) which executes a character recognition process and is installed in a personal computer. In FIG. 5, the color image sensor  17 , signal processing circuit  30 , and A/D conversion circuit  31  are included in the scanner apparatus. On the other hand, the image buffer memory  32 , image processing unit  33 , and character recognition unit  34  are included in the character recognition apparatus.  
     [0044] An operation of this embodiment will be described below using the flow chart shown in FIG. 6.  
     [0045] A fluorescent ink detection process is executed on the forms on which the printing for numbering has been effected using fluorescent ink and the forms on which character recognition target areas have been limited by printing marks using fluorescent ink (step  130 ). If it is detected that the printing for numbering has been effected to a form (YES in step  131 ), this form is rejected from the targets because a character recognition process for this form has already been completed (step  132 ). On the other hand, if it is NO in step  131  and one or more character recognition target areas (one or more target lines) with fluorescent ink are detected, a character recognition process for the detected lines is executed (step  133 ).  
     [0046] Next, a detailed operation including steps for the fluorescent ink detection will be described below using the flow chart shown in FIG. 7.  
     [0047] A case will be exemplified below wherein an image of the form  18 , on which characters are printed using transparent fluorescent ink which is excited by near ultraviolet rays having a wavelength of, e.g., 450 nm, and emits light having a wavelength of 650 nm, is captured by the scanner apparatus, and images of the characters formed using the fluorescent ink undergo character recognition.  
     [0048] In step S 1 , the optical head  14  is moved to a position opposing the white reference plate  19 , and shading correction is done for output voltages respectively output from the line image sensors  171 ,  172 , and  173 .  
     [0049] Shading correction adjusts the gains in the signal processing circuit  30  so that output voltages output from all photodetection elements of the color image sensor assume identical values when light emitted by the white light source  16  and reflected by the white surface of the white reference plate  19  is input to the line image sensors. The reason why such shading correction is required will be explained below.  
     [0050] In general, when light emitted by the white light source  16  and reflected by the white surface of the white reference plate  19  is input to a color line image sensor, output voltages output from all the photodetection elements of the color line image sensor do not assume identical values, and output voltages from end photodetection elements of those arranged in a line become lower than those output from central photodetection elements. This is caused by light source nonuniformity (distortion) and the characteristics of the color line image sensor. In the graph shown in FIG. 9, the X-axis plots the positions of a plurality of photodetection elements arranged in a line, and the Y-axis plots output voltages from the respective photodetection elements. The output voltage of a photoelectric conversion element becomes higher with increasing amount of incoming light. For this reason, the output of the central portion of the waveform of the output voltage shown in FIG. 9 is set as a white reference voltage, and output voltages from all the photodetection elements must be corrected to become equal to the white reference voltage.  
     [0051] Hence, in step S 1  the outputs from the line image sensors  171 ,  172 , and  173  respectively undergo shading correction. More specifically, output voltages output from the respective photodetection elements of the line image sensor  171  are monitored, and the gains upon amplifying the output voltages from all the photodetection elements are controlled so that all the photodetection elements output identical voltages, as shown in FIG. 10. Likewise, the outputs from the line image sensors  172  and  173  undergo shading correction.  
     [0052] Such shading correction can be achieved by the signal processing circuit  30  which includes a plurality of variable-gain amplifiers, and a control circuit which monitors the outputs from the amplifiers and controls the gain of the individual amplifiers to obtain identical outputs. It is best to implement the control circuit by a microprocessor that operates based on a control program called firmware.  
     [0053] In step S 2 , the signal processing circuit  30  executes white correction by controlling the gains of the amplifiers so that the output voltages output from the line image sensors  171 ,  172 , and  173  assume identical values. White correction adjusts the output voltages of red (R), green (G), and blue (B) color components to assume identical values, so that the color image sensor  17  generates a white output upon receiving light reflected by a white portion. As a result of white correction, voltage values are preferably standardized to those which are converted into the highest level values “255” by the A/D conversion circuit  31 .  
     [0054] In step S 3 , an image of the form  18  is captured. Specifically, the surface of the form  18  is irradiated with light emitted by the white light source  16  while moving the optical head  14  within the range of the form  18  placed on the glass  12 , light reflected by the surface of the form  18  is photoelectrically converted by the color image sensor  17  to obtain analog signals as output voltages of red (R), green (G), and blue (B) color components, and the obtained analog signals are amplified by the signal processing circuit  30 . The analog signals amplified by the signal processing circuit  30  are converted into 256-level digital data by the A/D conversion circuit  31 , and the digital data are output to the image buffer memory  32 .  
     [0055] With this operation, the form image of the form  18  is stored as digital data in the image buffer memory  32 .  
     [0056] In step S 4 , the sheet surface white level detection circuit  331  of the image processing unit  33  is enabled to detect the level of image data on a blank portion where no information is recorded at the leading end of the form  18 , i.e., the white level of the sheet surface, with reference to the image data of the form  18  stored in the image buffer memory  32 .  
     [0057] In general, the white level of the sheet surface is lower than level “220” which is the output value of white reference obtained from the A/D conversion circuit  31  after white correction in step S 2 . Also, the white level of the sheet surface varies depending on paper quality such as the paper thickness, paper color, and the like of the form  18 . For example, assume that the white level of the sheet surface detected in step S 4  falls within the range from 220 to 200, as shown in the graph of FIG. 11. In this case, level “220”, as the highest value is detected as the white level of the sheet surface, and is stored in the image processing unit  33 . In FIG. 11, level “220” indicates the white level as white reference after white correction obtained in step S 3  using the white reference plate  19 .  
     [0058] In step S 5 , the fluorescent ink detection circuit  332  of the image processing unit  33  is enabled to detect images formed on the form  18  using fluorescent ink with reference to the image data of the form  18  stored in the image buffer memory  32 .  
     [0059] Some specific fluorescent ink has characteristics in which when the image sensor detects visible light which is emitted by ink excited upon being irradiated with ultraviolet rays, the output level after photoelectric conversion of the image sensor is saturated and assumes a value higher than level “220”, as the white level of white reference shown in FIG. 11. This invention uses the fluorescent ink having such characteristics to detect images such as characters, figures, marks, or the like formed on the form  18  using the fluorescent ink. In this embodiment, as described above, the image buffer memory  32  stores an image of the form  18  on which characters or the like are printed using transparent fluorescent ink which is excited by near ultraviolet rays having a wavelength of, e.g., 450 nm, and emits light having a wavelength of 650 nm. The fluorescent ink used has the aforementioned characteristics.  
     [0060] Fluorescent ink detection in step S 5  will be explained below with reference to the flow chart shown in FIG. 8.  
     [0061] In step S 51 , image data of the form  18 , which is obtained by A/D-converting the output voltage from, e.g., the line image sensor  171 , of those stored in the image buffer memory  32  is read out.  
     [0062] In step S 52 , the level of the readout image data is compared with level “220”, as the white level of the sheet surface detected in step S 3 . If the level of the readout image data is higher than level “220”, a binary value “1” is assigned to the readout image data in step S 53 . On the other hand, if the level of the readout image data is lower than level “220”, a binary value “0” is assigned to the readout image data in step S 54 .  
     [0063] Since the readout image data is binarized based on the comparison result in step S 52 , an image of a character or the like formed using the fluorescent ink expressed by a binary value “1” can be detected. The image processing unit  33  transfers the detected images formed using the fluorescent ink to the character recognition unit  34 .  
     [0064] In step S 6  in FIG. 7, the character recognition unit  34  recognizes characters, figures, marks, or the like based on the image data which are obtained by binarizing the characters formed using the fluorescent ink and are transferred from the image processing unit  33 . For example, if a form is recognized as being recorded using fluorescent ink by the numbering print process, the form is rejected. On the other hand, if character recognition target areas with fluorescent ink on a form are detected, the binarized image of the character recognition target areas is acquired and character recognition process is executed.  
     [0065] The operation shown in the flow chart in FIG. 7 is done every time one form is read. This is because the output voltages from the color image sensor  17  change due to aging and temperature characteristics, and the amount of light emitted by the white light source  16  is not constant and lowers due to aging. For these reasons, shading correction and white correction are required every time the form is read.  
     [0066] In the aforementioned embodiment, transparent fluorescent ink, which is excited by near ultraviolet rays and emits light having a wavelength of 650 nm, is used. However, the present invention is not limited to such specific fluorescent ink. More specifically, any other fluorescent inks may be used as long as they satisfy the following three conditions. That is, ink need satisfy: (1) it is excited by near infrared light contained in visible light output from the white light source; (2) the wavelength of visible light emitted upon exciting it has one of the three wavelengths enumerated below; and (3) the output level of a voltage output from the image sensor that detects visible light emitted by exciting the ink assumes a value higher than the white level as white reference.  
     [0067] The three wavelengths in condition (2) include a wavelength (e.g., around 450 nm) which can be detected by the line image sensor  171  for detecting a red color component, a wavelength (e.g., around 540 nm) which can be detected by the line image sensor  172  for detecting a green color component, and a wavelength (e.g., around 430 nm) which can be detected by the line image sensor  173  for detecting a blue color component.  
     [0068] When fluorescent ink that emits visible light of a wavelength which can be detected by the line image sensor  172  for detecting a green color component is used, an image must be detected based on image data output from the line image sensor  172  for detecting a green color component. Likewise, when fluorescent ink that emits visible light of a wavelength which can be detected by the line image sensor  173  for detecting a blue color component is used, an image must be detected based on image data output from the line image sensor  173  for detecting a blue color component.  
     [0069] In the description of the above embodiment, transparent ink which is invisible to a human is used. However, the present invention is not limited to such specific ink. That is, ink visible to a human may be used by adding a pigment depending on applications.  
     [0070] In the present invention, white correction in step S 2  is not always indispensable. If the color image sensor  17  is used to read a color image, white correction is indispensable, but if the color image sensor  17  is used to read only an image formed using fluorescent ink, only shading correction is required.  
     [0071] In this embodiment, the flatbed type scanner apparatus is used. However, the present invention is not limited to such specific scanner apparatus. For example, a scanner apparatus which stacks a plurality of forms to be read on a hopper, and feeds the forms one by one from the hopper may be used.  
     [0072] When the color image sensor  17 , signal processing circuit  30 , A/D conversion circuit  31 , buffer memory  32 , and image processing unit  33  shown in FIG. 5 are included in the scanner apparatus, an information acquisition apparatus that acquires information from a form on which information is recorded using fluorescent ink can be constituted.  
     [0073] As described in detail above, according to the present invention, characters and marks formed using fluorescent ink can be detected and recognized without using any special components such as a special light source for emitting ultraviolet light, an optical filter for intercepting transmission of ultraviolet light, or the like. Moreover, it is possible to execute numbering print process and limit recognition target areas using fluorescent ink, without making forms dirty.  
     [0074] Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.