Image processing apparatus, reading device, image forming apparatus, image processing method, and recording medium

Abstract

The image processing apparatus includes: a light source configured to irradiate an object with at least invisible light; an image sensor having sensitivity to a visible light wavelength range and an invisible light wavelength range; an image processor configured to generate an image according to the image information output by the image sensor; a switching unit configured to switch the image processor to a monochrome image generation mode in which a monochrome image is generated, the monochrome image being a monochrome image; and a controller configured to control the switching unit to switch the image processor to a monochrome image generation mode in response to selection of an action mode in which invisible light is irradiated.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to an image processing apparatus, a reading device, an image forming apparatus, an image processing method, and a recording medium. Background Art

[0002] As is known in the art, for example, a latent image that cannot be recognized under visible light is formed on some public certificates. A reading device that emits invisible light (e.g., infrared light) reads a document on which a latent image is formed, whereby the latent image in an image output from the reading device can be perceived by the naked eye. Thus, authenticity is checked.

[0003] Patent Document 1 discloses a technique for solving the difficulty of viewing an infrared image in a nighttime imaging mode of a surveillance camera. The disclosed technique enhances the visual recognizability of an image by synthesizing an infrared image and a visible color image.

[0004] Citation list

[0005] Patent Literature

[0006]

PTL1

[0007] Technical issues

[0008] However, since the image generation mode using visible light is usually selected, the settings for generating the image must be changed each time the image output using invisible light is performed. When the image output using invisible light is performed without changing the settings, the image processing is performed using the color settings when using visible light. In this case, there is a disadvantage that the appearance of the output image is unnaturally colored differently from the appearance of the original of the object, and a large sense of incongruity is generated when the output image is confirmed.

[0009] In view of the above problems, an object of the present disclosure is to provide an image processing device, a reading apparatus, an image forming device, and an image processing method, which can select an image generation mode according to the coloring method of the original object of the object when using the setting of invisible light.

[0010] Solutions to the problem

[0011] An embodiment of the present disclosure includes an image processing device. The image processing device includes:

[0012] a light source configured to illuminate the object with at least invisible light;

[0013] An image sensor having sensitivity in the visible light wavelength range and the invisible light wavelength range;

[0014] an image processor configured to generate an image based on image information output by the image sensor;

[0015] a switching unit configured to switch the image processor to a monochrome image generation mode for generating a monochrome image, the monochrome image being a monochrome image; and

[0016] The controller is configured to control the switching unit to switch the image processor to a monochrome image generation mode in response to selection of the invisible light irradiation action mode.

[0017] An embodiment of the present disclosure includes a reading device, which includes a scanner, and the scanner includes the light source and the image sensor of the above-mentioned image processing device.

[0018] An embodiment of the present disclosure includes an image forming device. The image forming device includes:

[0019] A scanner comprising the light source and the image sensor of the above-mentioned image processing device; and

[0020] The image forming section is configured to form an image based on the output image output from the image processor.

[0021] An embodiment of the present disclosure includes an image processing method. The image processing method includes:

[0022] Illuminating the object with at least invisible light;

[0023] outputting image information of the object from an image sensor having sensitivity to a visible light wavelength range and an invisible light wavelength range;

[0024] generating an image based on the image information output from the image sensor; and

[0025] In response to the selection of the action mode of irradiating invisible light, the mode switches to a monochrome image generation mode for generating a monochrome image, which is a monochrome image.

[0026] An embodiment of the present disclosure includes a recording medium storing a program, wherein the program stores instructions, and when the instructions are executed by one or more processors of a computer, the one or more processors perform an image processing method. The method includes:

[0027] Illuminating the object with at least invisible light;

[0028] outputting image information of the object from an image sensor having sensitivity to a visible light wavelength range and an invisible light wavelength range;

[0029] generating an image based on the image information output from the image sensor; and

[0030] In response to the selection of the action mode of irradiating invisible light, the mode switches to a monochrome image generation mode for generating a monochrome image, which is a monochrome image.

[0031] Effects of the Invention

[0032] According to one or more embodiments of the present disclosure, in the case of using the setting of invisible light, it is possible to select an image generation mode according to the coloring method of the original object of the object. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] A more complete understanding of the embodiments and many of the attendant advantages and features can be readily obtained and understood from the following detailed description taken in conjunction with the accompanying drawings.

[0034] [ Figure 1 ]

[0035] Figure 1 This is a block diagram showing an example of the structure of the image processing device according to the first embodiment of the present invention.

[0036] [ Figure 2 ]

[0037] Figure 2 This is a graph showing an example of spectral sensitivity characteristics of a general silicon image sensor.

[0038] [Figure 3]

[0039] FIG. 3A to FIG. 3E : is a diagram showing an example of comparison between an output image in a multi-color image generation mode and an output image in a monochrome image generation mode according to an embodiment of the present disclosure.

[0040] [ Figure 4 ]

[0041] Figure 4 is a flowchart representing an example of image processing performed by the image processing apparatus according to an embodiment of the present disclosure.

[0042] [ Figure 5 ]

[0043] Figure 5 is a diagram showing a configuration of a reading device according to an example.

[0044] [ Figure 6 ]

[0045] Figure 6 : is a graph showing an example of spectral reflectance characteristics of general paper and a reference white plate.

[0046] [ Figure 7 ]

[0047] Figure 7 This is a block diagram showing an example of a reading device according to a first variation of this example.

[0048] [ Figure 8 ]

[0049] Figure 8 This is a flowchart showing an example of the flow of image processing performed by the reading device according to Modification 1 of this example.

[0050] [Figure 9]

[0051] 9A to 9F 1 is a diagram showing an example of comparison between a case where background correction processing is included and a case where background correction processing is not included according to Modification 1 of this example.

[0052] [ Fig.10 ]

[0053] Fig.10 This is a block diagram showing an example of the structure of a reading device involved in Modification Example 2 of this example.

[0054] [ Fig.11 ]

[0055] Fig.11 This is a flowchart showing an example of the flow of image processing performed by the reading device according to Modification 2 of this example.

[0056] [Figure 12]

[0057] Fig. 12A , Fig. 12B and Fig. 12C 2 is a diagram for describing a print correction process according to Modification 2 of this example.

[0058] [ Fig.13 ]

[0059] Fig.13 It represents the spectral sensitivity characteristics of a general silicon image sensor ( Figure 2 ) and the emission distribution characteristics of a near-infrared (NIR) light source.

[0060] [ Fig.14 ]

[0061] Fig.14 This is a block diagram showing an example of the structure of a reading device involved in Modification 3 of this example.

[0062] [ Fig.15 ]

[0063] Fig.15 This is a flowchart showing an example of the flow of image processing performed by the reading device according to Modification 3 of this example.

[0064] [ Fig.16 ]

[0065] Fig.16 It is the spectral sensitivity characteristic of red (R), green (G), and blue (B) pixels. Figure 2 ) and infrared (IR) pixels.

[0066] [ Fig.17 ]

[0067] Fig.17 This is a block diagram showing an example of the structure of a reading device involved in Modification 4 of this example.

[0068] [ Fig.18 ]

[0069] Fig.18 This is a block diagram showing an example of the structure of a reading device involved in Modification 5 of this example.

[0070] [ Fig.19 ]

[0071] Fig.19 This is a flowchart showing an example of the flow of image processing by the reading device according to Modification 5 of this example.

[0072] [Figure 20]

[0073] Fig. 20A , Fig. 20B and Fig. 20C : is a diagram showing an example of comparison between an output image in a case where background correction processing is performed using correction values ​​and an output image in a case where background correction is performed without using correction values ​​according to Modification 5 of this example.

[0074] [ Fig.21 ]

[0075] Fig.21 This is a flowchart showing an example of the flow of image processing performed by the reading device according to Modification 6 of this example.

[0076] [Figure 22]

[0077] Fig.22A , Fig. 22B , Fig. 22C 1 is a diagram showing a comparative example of a monochrome multi-valued image and a monochrome binary image according to Modification 6 of this example.

[0078] [ Fig.23 ]

[0079] Fig.23This is a flowchart showing an example of the flow of image processing performed by the reading device according to Modification 7 of this example.

[0080] [Figure 24]

[0081] Fig.24A , Fig. 24B , Fig.24C 1 is a diagram showing a comparative example of a monochrome multi-valued image and a monochrome binary image according to Modification 7 of this example.

[0082] [ Fig.25 ]

[0083] Fig.25 This is a flowchart showing an example of the flow of image processing performed by the reading device according to Modification 8 of this example.

[0084] [ Fig.26 ]

[0085] Fig.26 1 is a schematic diagram showing the structure of the image forming apparatus of Embodiment 2.

[0086] The accompanying drawings are intended to describe embodiments of the present disclosure and should not be interpreted as limiting the scope thereof. Unless explicitly noted, the accompanying drawings should not be considered to be drawn to scale. Moreover, throughout the several views, the same or similar reference numerals represent the same or similar components. DETAILED DESCRIPTION

[0087] In describing the embodiments shown in the drawings, specific terms are used for clarity. However, the disclosure of this specification is not intended to be limited to the specific terms selected, and it should be understood that each specific component includes all technical equivalents having similar functions, operating in a similar manner and achieving similar results.

[0088] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0089] Hereinafter, embodiments of an image processing apparatus, a reading device, an image forming apparatus, and an image processing method will be described in detail with reference to the accompanying drawings.

[0090] Example 1

[0091] Figure 1 This is a diagram showing an example of the structure of the image processing apparatus 1 according to the first embodiment. Figure 1 The image processing apparatus 1 shown includes a controller 11 , a switching unit 12 , and an image processor 13 .

[0092] The controller 11 and the switching unit 12, and the switching unit 12 and the image processor 13 are connected, for example, by signal lines. The imaging device 2 may be mounted on a substrate of the image processing apparatus 1, or may be connected to an external terminal of the image processing apparatus 1 via a communication cable.

[0093] The camera device 2 includes a light source 21 and an image sensor 22. The light source 21 includes a light source capable of irradiating the object P with at least invisible light. The light source 21 may also include a light source that irradiates visible light to the object P. The image sensor 22 is an image sensor that is sensitive to the visible light wavelength range and the invisible light wavelength range, such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). For ease of explanation, an example in which the image sensor includes pixels of three colors of red (R) pixels, green (G) pixels, and blue (B) pixels is described, but this is only an example. Any suitable image sensor can be used as long as it includes pixels of at least two colors.

[0094] In response to receiving a request signal to start imaging from the controller 11, the imaging device 2 starts imaging in a specified operation mode and sends image information to the image processor 13. The image processor 13 performs image processing in an image generation mode corresponding to the operation mode of the imaging device 2 based on the image information output from the imaging device 2.

[0095] The operation mode of the camera device 2 includes a first operation mode for outputting visible image information and a second operation mode for outputting invisible image information. The visible image information is image information output in response to the image sensor 22 receiving reflected light from the object P under visible light. The invisible image information is image information output in response to the image sensor 22 receiving reflected light from the object P under invisible light.

[0096] As an example, in the first operation mode, the camera 2 captures the object P in a state where the invisible light of the light source 21 is turned off, and the camera 22 outputs visible image information of the object P. When the light source 21 includes a visible light source, the illumination of the visible light is turned on. In addition, in the second operation mode, the camera 2 captures the object P in a state where the invisible light of the light source 21 is turned on, and the camera 22 outputs invisible image information of the object P. When the light source 21 includes a visible light source, the illumination of the visible light is turned off.

[0097] The image generation mode of the image processor 13 includes a plurality of image generation modes. As an example, the image processor 13 has a multi-color image generation mode and a monochrome image generation mode. The multi-color image generation mode is an image generation mode that generates output images of multiple colors by multiplying visible image information of multiple colors from the camera 2 by a coefficient for correcting sensitivity deviations between colors. As a multi-color image generation mode, there is, for example, a color image generation mode that generates an RGB color image. The monochrome image generation mode is an image generation mode that generates a monochrome output image of the object P.

[0098] The controller 11 receives an operation instruction from, for example, an operation unit used by a user to configure settings. The controller 11 receives an image capture start instruction and an action mode from the operation unit, and sends signals corresponding to the image capture start instruction and the action mode, respectively, to the image capture device 2. The switching unit 12 detects whether the signal sent from the controller 11 to the image capture device 2 is an instruction for the second action mode. In response to detecting the instruction for the second action mode, the switching unit 12 sends a signal for switching the image generation mode to the image generation mode corresponding to the second action mode to the image processor 13. For example, when the default setting of the image generation mode of the image processor 13 is the multi-color image generation mode, the multi-color image generation mode is switched to the monochrome image generation mode.

[0099] The image processor 13 applies the setting of the multi-color image generation mode or the monochrome image generation mode to the image information output from the image sensor 22 , and outputs a generated image to which the setting is applied as an output image.

[0100] About the difference between multi-color image generation mode and monochrome image generation mode

[0101] Figure 2 This is a graph showing an example of spectral sensitivity characteristics of a general silicon image sensor. Figure 2 The spectral sensitivity characteristics of represent the comparative spectral sensitivity of R pixels, G pixels, and B pixels. Since R, G, and B have characteristic curves of different shapes, when receiving visible light, a deviation in sensitivity occurs between colors. Therefore, even if the amount of light is the same, the value obtained by electrical conversion differs depending on the color.

[0102] In the first operation mode, the setting of the multi-color image generation mode is applied to the image processor 13. Therefore, the visible image information of each color is multiplied by a coefficient for correcting the sensitivity deviation between colors, and an output image of each color is generated.

[0103] As a result, the deviation in sensitivity between colors is corrected, and an image obtained by synthesizing the output images of the respective colors is reproduced in colors close to the original.

[0104] like Figure 2As shown, a general silicon image sensor is sensitive not only to the visible light wavelength range (wavelengths of approximately 400 nm to 780 nm), but also to the invisible light wavelength range (for example, wavelengths of 780 nm or greater). In the invisible light wavelength range, the characteristic curves of the R pixel, the G pixel, and the B pixel basically overlap with each other, and there is almost no deviation in sensitivity between the colors. Therefore, for the invisible image information, if the same deviation correction as that of the visible light is performed while the image processor 13 maintains the setting of the multi-color image generation mode, an unnaturally colored output image different from the appearance of the original object is generated. For example, G in RGB is emphasized, and thus the output image becomes greenish as a whole. When compared with the original object image, the output image becomes inconsistent.

[0105] FIG. 3A to FIG. 3E : is a diagram showing an example of comparison between an output image in the multi-color image generation mode and an output image in the monochrome image generation mode. Figure 3A to Figure 3D This is a diagram showing an example of an output image when the multi-color image generation mode is applied to invisible image information. Figure 3E This is a diagram showing an example of an output image when the monochrome image generation mode is applied to invisible image information.

[0106] When outputting an image captured under visible light, for R image information, G image information, and B image information output from the image sensor 22, a coefficient for correcting the sensitivity deviation between the colors of the image sensor 22 is determined, and the determined coefficient is applied. On the other hand, when outputting an image captured under invisible light, when generating an output image in the multi-color image generation mode, a coefficient effective in the visible light wavelength range is applied. Since the coefficient is not effective for the invisible image, G is emphasized, for example, compared with R and B. In this case, as shown in FIG. Figure 3D As shown, the output image is colored a different green than the original image.

[0107] On the other hand, in the case of outputting an image captured under invisible light, when the mode is switched to the monochrome image generation mode, the output image is not colored. Figure 3E The image is a monochrome image, for example, a monochrome image generated based on the G image information. Since the R image information and the B image information are not used, the output image is generated as a monochrome image, and an image that does not look out of place compared to the original image is obtained.

[0108] Furthermore, in the case where the output image is stored in the storage device, since the output image is Figure 3E The monochrome image shown is not Figure 3D The composite image shown includes images of a plurality of colors, and therefore, there is also an advantage that the amount of data is approximately one-third.

[0109] Figure 4 1 is a flowchart showing an example of image processing performed by the image processing apparatus 1. First, the controller 11 stands by until receiving an image capture start request from the operation unit (step S1). It is assumed that the image capture device 2 is also in a standby state until receiving an image capture start request.

[0110] When the imaging start request is not received (step S2: No), the controller 11 maintains the standby state of step S1. When the imaging start request is received (step S2: Yes), the controller 11 sends an imaging start signal to the imaging device 2 via the switching unit 12. The switching unit 12 detects whether the signal sent from the controller 11 is a second imaging start signal instructing to start imaging in the second action mode, that is, the mode of outputting invisible image information (step S3).

[0111] When the switching unit 12 detects that the camera start signal sent by the controller 11 is the second camera start signal (step S3: yes), it sends a signal for switching to the monochrome image generation mode to the image processor 13, and switches the mode of the image processor 13 from the default multi-color image generation mode to the monochrome image generation mode (step S4).

[0112] When the imaging start signal transmitted by the controller 11 is not the second imaging start signal (step S3: No), the switching unit 12 does not switch the setting of the image processor 13 but maintains the default setting (step S5).

[0113] After the image processor 13 is set, the camera 2 starts capturing images in the operation mode corresponding to the request signal sent from the switching unit 12 (step S6). The image processor 13 generates an image by applying the default image generation mode or the switched image generation mode to the image information output from the camera 2 (step S7), and outputs the generated image as an output image (step S8).

[0114] The output destination to which the output image is to be outputted may be any desired location determined according to the configuration. Examples of output destinations include a display or a storage device. In another example, in the case where a printing mechanism for printing on a paper medium is provided, the output destination may be a printing device.

[0115] As described above, when the operation mode of the camera 2 is the second operation mode for invisible images, the image processing apparatus 1 automatically switches the setting of the image processor 13 to the setting for obtaining an output image corresponding to the second operation mode. Therefore, even when the camera 2 is operating in the second operation mode, an image that does not feel out of place compared to the original image is obtained.

[0116] The image processing device described in this embodiment can be applied to a reading device. In addition, the image processing device can be applied not only to a reading device but also to, for example, a vehicle-mounted camera. Hereinafter, an example of applying the image processing device to a reading device will be described. In the following description, points different from the embodiment will be described, and repeated descriptions described in the embodiment will be appropriately omitted.

[0117] Example of Embodiment 1

[0118] Figure 5 FIG. 2 is a diagram showing the structure of a reading device 3 as an example. The reading device 3 is a scanner. Figure 5 As shown, the reading device 3 has a reading unit 31, a controller 32, a switching unit 33, and an image processor 34. The reading unit 31 corresponds to the camera 2. The light source 311 corresponds to the light source 21. The image sensor 312 corresponds to the image sensor 22. The controller 32 corresponds to the controller 11. The switching unit 33 corresponds to the switching unit 12. The image processor 34 corresponds to the image processor 13.

[0119] The reading object of the reading unit 31 is a document P1. The document P1 is, for example, a public certificate such as a residence certificate. Some public certificates include latent image information for determining authenticity. Such a document P1 is described as an example. A document such as a public certificate is only an example. The document P can be any other suitable document as long as the document includes visible information perceptible to the human eye under visible light and latent image information that can be confirmed on an image obtained by reading the document, wherein the document is irradiated with invisible light.

[0120] Most latent image information such as public certificates can be read by infrared light. Infrared light is only an example of invisible light. As invisible light, light in a short wavelength range such as ultraviolet light or X-rays can be applied.

[0121] General image sensors also have sensitivity in the near-infrared region (approximately from 750 nm to 1100 nm) (see Figure 2 ). Therefore, this example can be applied to use Figure 7 The conventional reading device of a general silicon image sensor having a pixel sensor including an R pixel m1, a G pixel m2, and a B pixel m3 is shown.

[0122] The R pixel m1 of the image sensor 312 reads light in the R wavelength range under visible light, and outputs visible image information as R image information 51. The G pixel m2 reads light in the G wavelength range under visible light, and outputs visible image information as G image information 52. The B pixel m3 reads light in the B wavelength range under visible light, and outputs visible image information as B image information 53. The R pixel m1, the G pixel m2, and the B pixel m3 read light in the invisible wavelength range under invisible light, and output the invisible image information as R image information 51, G image information 52, and B image information 53, respectively. The image information is sent to the image processor 34. The image processor 34 generates an output image by setting it to a multi-color image generation mode or a monochrome image generation mode. The output image output by the image processor 34 can be output to, for example, a display or a storage device of the reading device 3. Alternatively, the output image can be output to an external device from an external output terminal.

[0123] In the reading device 3 of this example, the image sensor 312 having RGB pixels acquires image information of three colors under visible light, and synthesizes the acquired image information to obtain a color output image. That is, the reading device 3 of this example can be used as a color scanner and a black and white scanner. In addition, since the reading device 3 has a light source of invisible light and can output invisible image information, it can also be used as an invisible light scanner for special purposes. Since one reading device 3 can be switched to a color scanner, a black and white scanner, and an invisible light scanner, it can be expected that the convenience will be significantly improved.

[0124] Modification 1 of the example

[0125] As an example, the structure of a reading device having a background correction unit for correcting the background level of a document is described. At present, terminals installed in public places such as convenience stores can output public certificates using personal identification number cards. In such public places, certificates output from the terminal are printed on ordinary paper, and certificates issued by government agencies are printed on thick paper or paper with a colored background pattern. Therefore, among the terminals installed in such public places, there are terminals that have a unique mechanism for preventing unfair behavior by embedding information for authenticity determination into certificates printed on ordinary paper. Latent images are one of the information for authenticity determination embedded in certificates. Latent images can be read by a reading device using an infrared light source. However, unlike certificates issued by government agencies, terminals installed in public places do not have strict regulations on printed paper. Therefore, even if the paper used by the terminal is white to the naked eye of the human body, when a certificate printed by a different terminal is read by a reading device using infrared light, the density of the background of the output image output from the reading device will be biased, such as white or gray, due to the paper used in the terminal.

[0126] Figure 6 This is a graph showing an example of the spectral reflection characteristics of general paper and a reference white board. Figure 6 The spectral reflection characteristics of three different types of plain paper (paper A, paper B, and paper C) that appear substantially white to the naked eye are shown as an example of general paper.

[0127] like Figure 6 As shown, although substantially the same white output image is obtained when the reading device reads the three types of ordinary paper using visible light, when the reading device reads the three types of ordinary paper using infrared light, as shown in the infrared wavelength range, there are large differences in spectral reflectance between paper A, paper B and paper C.

[0128] Therefore, in the image of the certificate read by the reading device using infrared light, the background may have a density different from the apparent density of the original, such as a gray density. The output image output from the reading device is not the background density of the original certificate, so it leaves a sense of incongruity as evidence of the stored image.

[0129] Figure 7 1 is a block diagram showing an example of the structure of the reading device 3 of the modified example 1 of the example. Figure 7 As shown, the image processor 34 of the reading device 3 according to the first modification includes a background correction processing unit 341 .

[0130] Since the image generation mode of the image processor 34 is switched from the multi-color image generation mode to the monochrome image generation mode in the second operation mode, the background correction processing unit 341 operates in the monochrome image generation mode.

[0131] The background correction processing unit 341 performs background correction processing for correcting the background level of the document on the image information output in the second operation mode. For example, the background correction processing unit 341 uniformly corrects the area of ​​the invisible image corresponding to the "white" area in the visible image to the "white" image level, thereby correcting the gray area in the invisible image to the background level of the document.

[0132] Figure 8 This is a flowchart showing an example of the flow of image processing performed by the reading device 3 according to Modification 1 of the example.

[0133] exist Figure 8 In the process shown, Figure 4 The flow shown adds background correction processing.

[0134] As Figure 8 The overall process of steps S11 to S18 corresponds to Figure 4 Steps S1 to S8 are described. Figure 8In step S14, when the switching unit 33 switches the multi-color image generation mode of the image processor 13 to the monochrome image generation mode, the background correction process is started.

[0135] 9A to 9F 1 is a diagram showing an example of comparison between a case where background correction processing is included and a case where background correction processing is not included.

[0136] Fig. 9A , Fig. 9B and Fig. 9C This is an example of an output image obtained by reading paper A, paper B, and paper C by the reading device 3 in the second operation mode and outputting the read images without performing background correction processing. Each of paper A, paper B, and paper C used in this modification has a white background to the naked eye of a person.

[0137] Since no background correction is performed, Fig. 9A , Fig. 9B and Fig. 9C The difference in reflectance in the infrared wavelength range between the three types of paper appears on the output image of . Therefore, although the three types of paper have the same or substantially the same white color, the density of the three types of paper is different from each other.

[0138] on the contrary, Fig.9D , Fig.9E and Fig.9F This is an example of an output image obtained by reading paper A, paper B, and paper C by the reading device 3 in the second operation mode and outputting the read image on which the background correction process is performed. Since the background correction process is performed, the density difference caused by the difference in reflectivity in the infrared wavelength range between the three types of paper is corrected. Therefore, Fig.9D , Fig.9E and Fig.9F The background color of each output image is white, which is the same color as the original object viewed by the naked eye.

[0139] By performing background correction processing such as processing for correcting the background region to white in this manner, even when different white papers having different reflectances in the invisible light wavelength region are used, the background can be uniformly made white.

[0140] In this modification, the case where the background of the paper is white and the image level of the background is uniformly white is described, but this is only an example. Alternatively, the density may be changed according to the background density of the paper or the black character information printed on the paper. For example, assuming that black is at level 0 and white is at level 255, the image level may be slightly lowered to a level of about 200 to 230. Alternatively, the image level may be further lowered to correct the background to a constant level without lowering the density of the black character information, etc., that is, without lowering the visual recognition.

[0141] According to the configuration of the above modification example 1, background correction is performed on the invisible image read in the second operation mode. Even when the prescribed type of paper is not used, an output image that is the same or substantially the same as the original certificate to the naked eye can be obtained. Therefore, the output image including the invisible image information can be evidence of the stored image including the visible information.

[0142] Modification 2 of the example

[0143] As a variation 2 of this example, the structure of a reading device having a print correction processing unit that performs image correction suitable for printing is described. In the case where latent image information in a document is read by a reading device using invisible light and an output image obtained by reading is printed on paper or the like, when the required density is a density that can be visually recognized, there is no problem even if the density of the latent image information is low. However, when the latent image information is code information, a low density causes an error in reading the code. Therefore, it is necessary to correct the density. Therefore, in variation 2, it is described that a print correction processing unit is added so that the density of the latent image information can be corrected when printing the latent image information.

[0144] Fig.10 1 is a block diagram showing an example of the structure of the reading device 3 of the second variant of the example. Fig.10 As shown, the image processor 34 of the reading device 3 has a print correction processing unit 342 .

[0145] Since the image generation mode of the image processor 34 is switched from the multi-color image generation mode to the monochrome image generation mode, the print correction processing unit 342 is caused to operate in the monochrome image generation mode.

[0146] The print correction processing unit 342 of the image processor 34 performs image correction suitable for printing.

[0147] Fig.11 This is a flowchart showing an example of the flow of image processing performed by the reading device 3 according to Modification 2 of the example. Fig.11 The process shown is similar to Figure 8 The difference between the flow shown is that a print correction process is added. Fig.11 In step S24, the print correction process is added to the process of step S14.

[0148] In step S24, when the switching unit 33 switches the multi-color image generation mode of the image processor 13 to the monochrome image generation mode, the print correction process is further started.

[0149] Fig. 12A , Fig. 12B and Fig. 12Cis a diagram for describing the print correction process. Fig. 12A A document in which code information is formed as a latent image with invisible ink is shown. Fig. 12B It means that the print correction process is not performed, and the reading device 3 uses invisible light to read the Fig. 12A FIG. 1 is an example of outputting invisible image information obtained by using a document as shown in FIG. 1 to a paper. In the case where the purpose is only to visually recognize the latent image information, such as Fig. 12B As shown, there is no problem even if the code information x1 is output at an appropriate density.

[0150] However, when multiple people use their own imaging devices such as mobile cameras to read the code information printed on paper, the white of the background and the black of the dots must be corrected to appropriate levels so that the code information can be recognized by any imaging device, so that the imaging devices used by multiple people can read the code information.

[0151] exist Fig. 12B In , part of the code information x1 is 128-level gray, and the other part is 255-level white. Fig. 12B At the image density shown, when the code information printed on paper is read by the image forming apparatus, it is difficult to recognize the read code information.

[0152] On the contrary, when the image processor 34 performs the print correction processing, as shown in FIG. Fig. 12C As shown, the black dots are corrected to high density, and the background portion is corrected to low density. This improves the recognition rate of code information of each imaging device used by multiple people. Fig. 12C In the example shown, a part of the code information x1 is corrected to 16-level black, and the other part is corrected to 200-level white.

[0153] As described above, when the latent image information is, for example, code information to be read by another device, the print correction process can improve the recognition rate.

[0154] Modification 3 of the example

[0155] By printing on a document using a material that exhibits different absorption and transmission characteristics in the visible light wavelength range and the infrared wavelength range, invisible latent image information that is not visible to the naked eye can be embedded. Since a general image sensor can read infrared light, the embedded latent image information can be visualized by outputting a monochrome image in an infrared light reading mode. As an example, variant example 3 describes the structure of a reading device using a near infrared (NIR) light source as the light source 311.

[0156] Fig.13 It represents the spectral sensitivity characteristics of a general silicon image sensor ( Figure 2 ) and the luminous distribution characteristics of the NIR light source. Fig.13 As shown, silicon constituting the pixels of a general image sensor has sensitivity not only in the visible light wavelength region but also in the invisible infrared light region. In addition, the light emitted from the NIR light source is within the infrared light range and is not visible to the human eye. In contrast, the image sensor can receive the light emitted from the NIR light source and convert the received light into an image. Therefore, it is effective to use a near-infrared light source as invisible light.

[0157] Fig.14 1 is a block diagram showing an example of the structure of the reading device 3 of the modified example 3 of the example. Fig.14 As shown, as the light source 311 of the reading device 3, a near-infrared light source 311a is used.

[0158] In the first action mode, the image sensor 312 reads the document P1 using RGB pixels under visible light, and outputs image information of each RGB color respectively. In the second action mode, the document P1 is irradiated with near-infrared light, and the image sensor 312 reads the document P1 in monochrome with each RGB pixel. In this case, monochrome image information of the three colors is also output respectively. In the second action mode, image information corresponding to the three colors is output respectively, but in the second action mode, the image processor 34 switches to a monochrome image generation mode. Therefore, for example, image information corresponding to one of the three colors can be output as a monochrome image, or each image information corresponding to the three colors can be adjusted to monochrome and output. Therefore, an image is generated in a manner different from that in the multi-color image generation mode.

[0159] Fig.15 FIG. 1 is a flowchart showing an example of the flow of image processing performed by the reading device 3 according to the third variation of the example. Fig.15 In the process shown, Figure 8 The process of step S13 in the flow shown in FIG. 1 is replaced by the determination of the infrared light reading mode (step S23). Fig.15 The example shown does not include background correction processing, but background correction processing may be included.

[0160] As described above, by using a general-purpose image sensor, the same effect can be obtained in a simpler and lower-cost reading device.

[0161] Modification 4 of Example

[0162] As an example of Modification 4, a configuration of a reader 3 including infrared (IR) pixels having a peak sensitivity in a near-infrared wavelength region in addition to R pixels, G pixels, and B pixels will be described.

[0163] Fig.16 is the spectral sensitivity characteristic of R pixel, G pixel, and B pixel ( Figure 2 ) and the spectral sensitivity characteristics of IR pixels. Fig.15 As shown, the sensitivity of the IR pixel is low in the visible wavelength range and has a peak in the infrared wavelength range.

[0164] Fig.17 1 is a block diagram showing an example of the structure of the reading device 3 according to the modification example 4 of the example. Fig.17 As shown, the image sensor 312a of the reader 3 includes an IR pixel m4 having sensitivity characteristics different from those of the R pixel m1, G pixel m2, and B pixel m3. The light source 311 may be any light source including light in the infrared wavelength range, and may be a light source including visible light and infrared light.

[0165] In the first operation mode, the image sensor 312a reads the document P1 using RGB pixels (R pixel m1, G pixel m2, and B pixel m3), and outputs image information corresponding to RGB colors (R image information 51, G image information 52, and B image information 53). In the second operation mode, the image sensor 312a reads the document P1 in monochrome using IR pixel m4. In the second operation mode, since the image processor 34 switches to the setting of the monochrome image generation mode, the image information 54 of the IR pixel m4 can be output as a monochrome image. The image information 54 of the IR pixel m4 corresponds to infrared image information.

[0166] In having Fig.17 In the reading device 3 of the structure shown, in the first operation mode and the second operation mode, the light source 311 is set to light up, and the R image information 51 read by the R pixel m1, the G image information 52 read by the G pixel m2, the B image information 53 read by the B pixel m3, and the image information 54 read by the IR pixel m4 are output to the image processor 34, so that a visible image and an invisible image can be obtained by a single scan. The image processor 34 outputs three image information corresponding to the three colors of the R image information 51 output by the R pixel m1, the G image information 52 output by the G pixel m2, and the B image information 53 output by the B pixel m3 as a visible image by setting the multi-color image generation mode. The image processor 34 outputs the monochrome image information 54 output from the IR pixel m4 as a monochrome image when the monochrome image generation mode is set.

[0167] By acquiring the visible image at the same time as the evidence image used to verify the authenticity of the certificate, the original certificate image can also be retained. Currently, a copy of the original document is required in applications to government agencies, etc., and an image is required to confirm the authenticity in response to an emergency. By acquiring these images at the same time in one scan, convenience can be improved.

[0168] Modification 5 of Example

[0169] As a fifth modification of this example, a configuration of a reading device capable of changing the correction level of the background correction process will be described.

[0170] Fig.18 1 is a block diagram showing an example of a reading device 3 according to a fifth variation of the example. Fig.18 As shown, the reading device 3 of the modification 5 includes a background correction level setting unit 41 as a “setting section”.

[0171] The background correction level setting unit 41 can be set by the controller 32 , and the correction value set in the background correction level setting unit 41 is set by the background correction processing unit 341 .

[0172] Fig.19 FIG. 4 is a flowchart showing an example of the flow of image processing performed by the reading device 3 according to the modified example 5 of the example. Fig.19 In the process shown, Figure 8 The illustrated flow adds setting of a background correction level (step S21 ).

[0173] In the second operation mode, in step S21, the correction value of the background correction level setting unit 41 is set in the background correction processing unit 341. After the processing of step S21, in the second operation mode, the reading process is executed (step S16), the image processor 34 executes the monochrome image generation, and the background correction process using the correction value is executed (step S17).

[0174] Although the description given above is directed to the case where the background correction is not performed in the other reading modes other than the second action mode, the background correction may be performed in the other reading modes.

[0175] Fig. 20A , Fig. 20B , Fig. 20C 1 is a diagram showing an example of comparison between an output image when background correction processing is performed using correction values ​​and an output image when background correction is performed without using correction values. Fig. 20A Represents a document. Fig. 20B This is a diagram showing an output image obtained by performing a fixed-value background correction on an invisible image of a document. Fig. 20C This figure shows an output image after background correction is performed on an invisible image of a document by changing the correction value of the set value.

[0176] like Fig. 20A As shown in FIG. 1 , it is assumed that there is a document on which characters (A, B, and C) are printed with insufficient coating amount of invisible light ink. When background correction processing is performed on such a document, as shown in FIG. Fig. 20BAs shown, when the background is corrected to white as usual, although the latent image information is visualized, an output image is obtained in which the characters “A, B, C” are blurred and the visual recognition is poor.

[0177] On the other hand, Fig. 20C As shown in the figure, if the correction level is set to a slightly lower level, the background is slightly darker, but the density of the characters becomes higher, so the visual recognition is significantly improved. In addition, in the above description, the case where the document is latent image information is described, but in the case where the latent image is code information, if the visual recognition is poor, it will affect the recognition performance. Therefore, the configuration in which the background correction level can be changed to a desired value produces an effect that the latent image information after visualization can be processed in a simple manner.

[0178] Modification 6 of Example

[0179] As a modification example 6, the operation when the monochrome image generation mode is set to the monochrome binary image generation mode is described. The monochrome image generation mode includes a monochrome multi-value image generation mode and a monochrome binary image generation mode. The monochrome multi-value image generation mode is a mode for generating a monochrome multi-value (also called "grayscale") image. The monochrome binary image generation mode is a mode for generating a black and white binary image.

[0180] Fig.21 FIG. 1 is a flowchart showing an example of the flow of image processing performed by the reading device 3 according to the modification example 6 of the example. Fig.21 In the flow shown, the monochrome image is set as a monochrome binary image in step S14 of the above-mentioned image processing flow.

[0181] Fig.22A , Fig. 22B , Fig. 22C It is a diagram showing a comparative example between a monochrome multi-valued image and a monochrome binary image. Fig.22A Represents a document. Fig. 22B is a diagram representing an output image of an invisible image of a multi-valued generated document. Fig. 22C is a diagram showing an output image of an invisible image of a binary generated document. An output image in which each pixel is formed by a multi-valued image and an output image in which each pixel is formed by a binary image are equivalent to each other from the perspective of latent image information visualization. Fig. 22B In the case of multi-valued images, the characters and background are formed as multi-bit information. Fig. 22C In the case of a binary image, the image is formed by one bit of information, so that the characters are black and the background is white. Therefore, in the case of a monochrome binary image, since the background is white, a large image area can be compressed and a higher compression ratio can be obtained. The amount of image data can be reduced.

[0182] Modification 7 of Example

[0183] As a modification example 7, an operation in the case where the monochrome image generation mode is set to the monochrome multi-value image generation mode will be described.

[0184] Fig.23 FIG. 1 is a flowchart showing an example of the flow of image processing performed by the reading device 3 according to the modification example 7 of the example. Fig.23 In the flow shown, in step S14 of the above-mentioned image processing flow, the monochrome image is set to a monochrome multi-valued image.

[0185] Fig.24A , Fig. 24B , Fig.24C It is a diagram showing a comparative example between a monochrome multi-valued image and a monochrome binary image. Fig.24A Represents a document. Fig. 24B is a diagram representing an output image of an invisible image of a multi-valued generated document. Fig.24C is a diagram representing the output image of the invisible image of the binary generated document.

[0186] like Fig.24C In the case of setting the invisible image information whose density itself forms the design, or invisible image information whose density difference has meaning, as shown in the logo mark, the image cannot be reproduced when it is set to binary. In order to cope with such a situation, image formation is performed in a monochrome multi-value image generation mode for invisible image information whose density has meaning. As a result, the embedded invisible image information can be reproduced more faithfully.

[0187] Modification 8 of Example

[0188] The control for switching to a mode other than the monochrome image generation mode, such as the default mode, after the monochrome image generation mode is completed is described. Regarding the reading device, for example, in general offices or public places, color scanning operations, monochrome scanning operations, or copy operations that use visible light for scanning are often selected over scanning using invisible light. Therefore, by switching to, for example, a full-color mode or a mode that is set as a default mode alone instead of the invisible light scanning mode for a more special purpose, the convenience of the user is enhanced.

[0189] Fig.25 This is a flowchart showing an example of the flow of image processing performed by the reading device 3 according to Modification 8 of the example. Fig.25The flow shown includes step S19 of switching to a mode other than the monochrome image generation mode after the image is output. In this modification, the case where the mode is switched after the image is output is described, but as long as the image processing can be appropriately performed, the mode may be switched after other image processing is performed. In addition, considering the case where reading using invisible light is performed continuously, for example, a predetermined standby time may be set by a timer between image output and mode switching.

[0190] For convenience, the scanner is usually set to the automatic color mode by default, in which the document is read and it is determined whether the document is in color or monochrome, or the scanner is usually set to the full color mode. When the document is scanned unintentionally using invisible light with the default setting, an image with unnatural coloring or density processing may be output, which is different from what the naked eye can perceive. This leads to the disadvantage that the user feels uncoordinated when viewing the output image. In this case, the document must be scanned again with invisible light using a mode reset to a suitable mode, which takes time and effort. In addition, in the case where the scanning / copying action of the certificate for custody is returned to the owner immediately after only confirming the scan / copy action of the certificate for custody, re-reading cannot be performed. In this embodiment, at the moment when the second action mode for generating an image using invisible light is selected, the action mode is automatically switched to the monochrome image generation mode. Therefore, without the user having to switch the setting, the image generation mode that is optimal for the action mode using invisible light is automatically set, and the unnatural coloring of the output image can be prevented. In addition, when the action mode using invisible light is selected, the image processing device according to the present embodiment switches to the most appropriate monochrome image generation mode, regardless of whether the object is a moving object or a stationary object, thereby improving the image quality. In addition, scanning and copying are performed with appropriate settings at the time of first reading. Each of the image processing apparatus 1 and the reading device 3 includes, for example, a central processing unit CPU and a memory. The CPU executes a program loaded into the memory to implement one or more of the controller 11, the switching unit 12, the image processor 13, the controller 32, the switching unit 33, the image processor 34, the background correction processing unit 341, the print correction processing unit 342, and the background correction level setting unit 41. Or one or more of the controller 11, the switching unit 12, the image processor 13, the controller 32, the switching unit 33, the image processor 34, the background correction processing unit 341, the print correction processing unit 342, and the background correction level setting unit 41 may be implemented by hardware such as an application specific integrated circuit ASIC.

[0191] Example 2

[0192] Fig.26 Schematic diagram showing the structure of the image forming apparatus of Embodiment 2. Fig.26In the embodiment, a copy machine 100 as an example of an image forming apparatus includes an automatic document feeder (ADF) 3A having a function as a reading device, an image forming unit 4, and a paper feeding unit 5.

[0193] The paper supply unit 5 includes paper supply trays 521 and 522 and a paper supply roller unit 523. Recording media of different sizes are placed on the paper supply trays 521 and 522. The paper supply roller unit 523 includes a plurality of roller pairs that convey the recording media from the paper supply trays 521 and 522 to an image forming position where the image forming unit 4 forms an image on the recording medium.

[0194] The image forming unit 4 includes an exposure device 431, a photosensitive drum 432 each having a drum shape, a developing device 433, a transfer belt 434, and a fixing device 435. The image forming unit 4 forms a latent image on the photosensitive drum 432 by exposing the photosensitive drum 432 using the exposure device 431, and develops the latent image on the photosensitive drum 432 by supplying toners of different colors to the photosensitive drum 432 using the developing device 433. The image forming unit 4 transfers the toner image developed on the photosensitive drum 432 by the transfer belt 434 to the recording medium supplied from the paper supply unit 5, and fixes the toner of the toner image transferred to the recording medium by the fixing device 435, and fixes the synthesized color image to the recording medium.

[0195] Therefore, the reading device of the embodiment or the modified example can be applied to the image forming apparatus.

[0196] The above embodiments are illustrative and do not limit the present invention. Therefore, many additional modifications and variations are possible based on the above teachings. For example, within the scope of the present invention, the elements and / or characteristics of the different illustrative embodiments may be combined and / or replaced with each other. Any of the above operations may be performed in various other ways, such as in an order different from that described above.

[0197] The present invention can be implemented in any convenient form, such as using dedicated hardware, or a mixture of dedicated hardware and software. The present invention can be implemented as computer software implemented by one or more networked processing devices. The processing device includes any appropriately programmed device, such as a general-purpose computer, a personal digital assistant, a wireless application protocol (WAP) or a third generation (3G) compatible mobile phone, etc. Since the present invention can be implemented as software, each aspect of the present invention includes computer software that can be implemented on a programmable device. Any traditional carrier medium (carrier device) can be used to provide computer software to a programmable device. The carrier medium includes a transient carrier medium, such as an electrical, optical, microwave, acoustic or radio frequency signal carrying a computer code. An example of such a transient medium is a transmission control protocol / Internet protocol (TCP / IP) signal that carries a computer code through an IP network such as the Internet. The carrier medium also includes a storage medium for storing processor readable code, such as a floppy disk, a hard disk, a CD-ROM (CD-ROM), a magnetic tape device or a solid-state memory device.

[0198] The functions of the elements disclosed herein can be implemented using circuits or processing circuits, which include general-purpose processors, special-purpose processors, integrated circuits, application-specific integrated circuits (ASICs), digital signal processors (DSPs), field-programmable gate arrays (FPGAs), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. Processors are considered processing circuits or circuits because they include transistors and other circuits therein. In the present disclosure, a circuit, unit, or device is hardware that performs or is programmed to perform the functions described. The hardware can be any hardware disclosed herein or otherwise known that is programmed or configured to perform the functions described. When the hardware is a processor, it can be considered to be a type of circuit, and the circuit, device, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0199] This patent application is based upon and claims the benefit of priority from Japanese patent application No. 2022-073501 filed with the Japan Patent Office on April 27, 2022, the disclosure of which is incorporated herein in its entirety by reference.

[0200] Reference numerals list

[0201] 1 Image processing equipment

[0202] 2 Camera device

[0203] 11 Controller

[0204] 12 Switching unit

[0205] 13 Image Processor

[0206] 21 Light Source

[0207] 22 Image Sensor

[0208] P object

Claims

1. An image processing device, comprising: a light source configured to illuminate the object with at least invisible light; An image sensor having sensitivity in the visible light wavelength range and the invisible light wavelength range; an image processor configured to generate an image based on image information output by the image sensor; a switching unit configured to switch the image processor to a monochrome image generation mode for generating a monochrome image, the monochrome image being a monochrome image; and The controller is configured to control the switching unit to switch the image processor to a monochrome image generation mode in response to selection of the invisible light irradiation action mode.

2. The image processing apparatus according to claim 1, wherein: The image processor has a plurality of image generation modes, and The plurality of image generation modes include a color image generation mode that generates a red, green, and blue (RGB) color image.

3. The image processing device according to claim 1 or 2, further comprising a background correction processing unit configured to correct the background level of the image, wherein When the operation mode of emitting invisible light is selected, the background correction processing unit corrects the background level of the monochrome image.

4. The image processing apparatus according to claim 1 or 2, further comprising a print correction processing unit configured to correct the density of the monochrome image, wherein When the operation mode of emitting invisible light is selected, the print correction processing unit corrects the density of the monochrome image.

5. The image processing device according to claim 1 or 2, wherein: The light source emitting invisible light is a near-infrared light source configured to emit light in the infrared range, and The image sensor has sensitivity to an infrared light wavelength range as the invisible light wavelength range.

6. The image processing apparatus according to claim 1 or 2, wherein: The image sensor includes pixels having peak sensitivity to an infrared wavelength range, and The image processor generates the monochromatic image based on infrared image information output from the image sensor.

7. The image processing apparatus according to claim 3, further comprising a setting unit configured to set a correction level of the background correction processing unit, wherein When the setting unit changes the setting of the correction level, the background correction processing unit corrects the background level of the monochrome image using the changed setting.

8. The image processing apparatus according to claim 1 or 2, wherein: In the monochrome image generation mode, the image processor generates a black and white binary image as the monochrome image.

9. The image processing apparatus according to claim 1 or 2, wherein: In the monochrome image generation mode, the image processor generates a monochrome multi-valued image.

10. The image processing apparatus according to claim 1 or 2, wherein: After generating an image in the monochrome image generation mode, the switching unit switches the image processor from the monochrome image generation mode to a mode different from the monochrome image generation mode.

11. A reading device, comprising: A scanner comprising the light source and the image sensor of the image processing device of claim 1 or 2.

12. An image forming device comprising: A scanner comprising the light source and the image sensor of the image processing device of claim 1 or 2; and The image forming section is configured to form an image based on the output image output from the image processor.

13. An image processing method, comprising: Illuminating the object with at least invisible light; outputting image information of the object from an image sensor having sensitivity to a visible light wavelength range and an invisible light wavelength range; generating an image based on the image information output from the image sensor; and In response to the selection of the action mode of irradiating invisible light, the mode switches to a monochrome image generation mode for generating a monochrome image, which is a monochrome image.

14. A recording medium storing a program, wherein the program stores instructions, and when the instructions are executed by one or more processors of a computer, the one or more processors are caused to perform an image processing method, the method comprising: Illuminating the object with at least invisible light; outputting image information of the object from an image sensor having sensitivity to a visible light wavelength range and an invisible light wavelength range; generating an image based on the image information output from the image sensor; and In response to the selection of the action mode of irradiating invisible light, the mode switches to a monochrome image generation mode for generating a monochrome image, which is a monochrome image.

Images