JP2005196470A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably read the image of an object by miniaturizing the composition of a reading part using a one-dimensional imaging element. <P>SOLUTION: A light source 21 and a one-dimensional imaging element 24 are arranged at a position where they are linearly symmetrical to each other so that the irradiation light axis of the light irradiated from the light source 21 to a reading transparent plate 30 and the imaging optical axis of the one-dimensional imaging element 24 which introduces the light, which is irradiated from the light source 21 and reflected in the reading transparent plate 30, may form an angle, which is smaller than all the reflection angles on a reading surface, to the normal line of the reading surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus for reading image data such as a fingerprint pattern.

  In recent years, as a device for identifying a person, a pattern matching device that reads a person's fingerprint pattern as image data and executes a matching process on the fingerprint pattern has been used. Yes.

  Conventionally, in an image reading apparatus that reads image data of a fingerprint pattern, for example, a one-dimensional imaging element (photoelectric conversion element) is used (for example, Patent Document 1). In the fingerprint detection device described in Patent Document 1, an optical unit, an optical imaging unit, and a one-dimensional image sensor are arranged inside a housing so that the optical finger base is held by a slider. It is configured. The optical finger base is composed of a microprism plate having a large number of microprisms formed on the back surface.

Irradiation light from the light source means for illumination enters the incident surface of the microprism. Irradiation light from the light source means totally reflected on the surface is emitted from the emission surface of the microprism. The light emitted from the emission surface is imaged on the imaging surface through the optical imaging means. A photoelectric conversion element of a one-dimensional image sensor is arranged on this image formation surface, and the imaged light is converted into an electric signal according to its strength. A one-dimensional image signal is output from the one-dimensional image sensor corresponding to the optical pattern that can be placed on the surface.
Japanese Patent No. 2980051

  As described above, the fingerprint detection device described in Patent Document 1 is configured to read a fingerprint image by pressing a finger against a microprism (microplate), and the imaging optical system uses total reflection on the reading surface. ing. Therefore, the light source means and the one-dimensional image sensor are arranged so that the angle formed between the light emitted from the light source means and the optical axis of the light imaged on the optical imaging means is equal to or greater than the total reflection angle. Accordingly, the arrangement position of the light source means and the one-dimensional image sensor is restricted, and the optical system is complicated, so that there is a limit to downsizing the reading unit.

  Further, in the conventional fingerprint detection apparatus, the light emitted from the fingerprint convex portion of the finger that is in contact with the reading surface is subjected to surface irregular reflection, internal absorption, internal diffusion, and dimming to read the grayscale image of the fingerprint. For this reason, for example, when trying to read an object other than a finger (fingerprint), for example, a character or a picture described on paper, an optically complete contact cannot be obtained. The image (text or picture) could not be read.

  An object of the present invention is to provide an image reading apparatus that can further reduce the size and can stably read an image of an object in a configuration of a reading unit using a one-dimensional image sensor.

  The invention according to claim 1 is an image reading apparatus that reads an image of an object in contact with a reading surface, an irradiation optical axis of light emitted from a light source to the reading surface, and irradiation from the light source to the reading surface. The light source and the image sensor are line-symmetric so that the imaging optical axis of the image sensor that receives the reflected light is at an angle smaller than the total reflection angle on the reading surface with respect to the normal line of the reading surface. It is arranged at a position where

  According to a second aspect of the present invention, in the first aspect of the present invention, a two-dimensional image generated based on an image read by the imaging device with respect to an object moved while contacting the reading surface is used as the reading surface. Correction means for correcting the object based on a plurality of two-dimensional images respectively read in different movement directions of the object.

  According to a third aspect of the present invention, in the second aspect of the present invention, the correction unit performs correction based on a reference pattern included in the two-dimensional image.

  The invention according to claim 4 is the invention according to claim 3, wherein the two-dimensional image is a fingerprint image including a wrinkle of a first joint portion of a finger, and the correction means corresponds to a wrinkle of the first joint portion. The correction is based on the pattern to be corrected.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, a two-dimensional image generated based on an image read by the imaging device with respect to an object moved while contacting the reading surface is obtained. The image processing apparatus includes a correcting unit that performs correction based on the first image read in a stationary state and the second image read at the beginning of the movement of the object.

  According to a sixth aspect of the present invention, in the image reading apparatus that reads light reflected from an object irradiated from a light source by an imaging device, a hollow transparent rotating roller that rotates when the object is moved in a pressed state is provided, and the transparent Reflected by the irradiation optical axis of the light emitted from the light source and the reading surface which is irradiated from the light source and the object of the transparent rotating roller is pressed against the rotation of the roller in the hollow of the rotation roller. The light source and the image sensor are axisymmetric so that an imaging optical axis of the image sensor on which light is incident is at an angle smaller than a total reflection angle on the reading surface with respect to a normal line of the reading surface. It arrange | positions in the position which becomes.

  According to the first aspect of the present invention, the reading optical surface includes the irradiation optical axis of light emitted from the light source to the reading surface and the imaging optical axis of the image sensor that receives the light irradiated from the light source and reflected by the reading surface. By placing the light source and the image sensor in a line-symmetric position so that the angle is smaller than the total reflection angle on the reading surface with respect to the normal line, restrictions on the position of the light source and the image sensor are relaxed Therefore, the overall size of the apparatus can be reduced. In addition, by arranging the light source and the image sensor to be axisymmetric, it is possible to effectively convert, for example, fingerprint irregularities as light / dark information of an image using surface reflected light on the reading surface. Since reflection is not used, it is possible to read image information such as letters and pictures recorded on objects that are not optically close to each other, such as paper. be able to.

  According to the invention of claim 2, in addition to the effect of the invention of claim 1, a two-dimensional image generated on the basis of an image read by an imaging device with respect to an object moved while contacting the reading surface, Since correction is made based on a plurality of two-dimensional images that are read in different movement directions of the object, for example, the difference in the movement direction that occurs when the object is moved with non-uniform contact pressure on the reading surface. It is possible to correct distortions of different images due to.

  According to the third aspect of the invention, in addition to the effect of the second aspect of the invention, by correcting based on the reference pattern included in the two-dimensional image, a plurality of objects read in different moving directions of the object, respectively. The correction using the two-dimensional image can be stably performed.

  According to the invention of claim 4, in addition to the effect of the invention of claim 3, by correcting based on the pattern corresponding to the wrinkle of the first joint portion of the fingerprint image, there is an individual difference in this pattern. Therefore, correction using a plurality of two-dimensional images can be performed stably.

  According to the fifth aspect of the present invention, in addition to the effect of the first aspect of the invention, the first image read in the stationary state of the object and the second image read at the beginning of the movement of the object are also included. In addition, by correcting the two-dimensional image, for example, distortion that occurs when the object is moved in a state where the contact pressure is not uniform with respect to the reading surface is likely to appear greatly at the beginning of the movement of the object. Distortion and the like can be effectively corrected.

  According to the sixth aspect of the present invention, the irradiation optical axis of the light irradiated from the light source and the reading surface of the transparent rotating roller irradiated from the light source so as not to be interlocked with the rotation of the roller in the hollow of the transparent rotation roller. Position the light source and the image sensor in line symmetry so that the imaging optical axis of the image sensor on which the reflected light is incident is smaller than the total reflection angle on the reading surface with respect to the normal of the reading surface. By arranging, the restriction on the arrangement position of the light source and the image sensor is relaxed, and the entire apparatus can be reduced in size. In addition, by arranging the light source and the image sensor to be axisymmetric, it is possible to effectively convert, for example, fingerprint irregularities as light / dark information of an image using surface reflected light on the reading surface. Since reflection is not used, it is possible to read image information such as letters and pictures recorded on objects that are not optically close to each other, such as paper. be able to.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing a configuration of an electronic circuit of a mobile phone equipped with an image reading apparatus according to the first embodiment of the present invention.

  The mobile phone shown in FIG. 1 includes a CPU 10 connected to various devices such as a storage device 12, a RAM 14, a call unit 16, a display unit 18, a key unit 19, and a fingerprint reading unit 20 via a bus. . The fingerprint reading unit 20 reads an image of a fingerprint pattern on the fingertip using the subject as a human fingertip.

The CPU 10 implements various functions by executing programs stored in the program area of the RAM 14. In addition to controlling the function of the mobile phone, the CPU 10 executes reading control of fingerprint pattern image data (fingerprint image) by the fingerprint reading unit 20 and various processes for the image pattern.
The storage device 12 stores programs, data, and the like and is read out as necessary and stored in the RAM 14.

  The RAM 14 stores programs and various data and is accessed by the CPU 10. In addition to various programs for controlling the mobile phone, the RAM 14 executes a processing program for executing processing on the image data of the fingerprint pattern read by the fingerprint reading unit 20. Is stored. When the fingerprint reading unit 20 reads the image data of the fingerprint pattern, the read image data is stored.

The call unit 16 is a unit for performing wireless communication as a mobile phone.
The display unit 18 displays various data when executing various functions realized by the CPU 10.
The key unit 19 includes a plurality of keys including numeric keys for inputting telephone numbers and various function keys.

  The fingerprint reading unit 20 reads image data representing a fingerprint pattern. For example, a reading surface is provided on the surface of a casing of a mobile phone. The fingerprint reading unit 20 in this embodiment includes a light source 21, a lens optical system (selfoc lens 22), a one-dimensional imaging device 24, an imaging control circuit 26, an A / D conversion circuit 28, a movement amount detection device 29, and reading transparency. A plate 30 is included.

  Reading of the fingerprint pattern in the fingerprint reading unit 20 is performed by pressing the fingertip, which is the subject, on the reading surface and moving it in a predetermined direction in that state. In the fingerprint reading unit 20, the light reflected from the fingertip, which is the subject that is irradiated from the light source 21 and pressed (contacted) with the reading surface, is condensed on the one-dimensional imaging device 24 by the Selfoc lens 22. Under the control of the imaging control circuit 26, the light condensed through the Selfoc lens 22 is photoelectrically converted by the one-dimensional imaging device 24, and further converted by the A / D conversion circuit 28 as image data representing a fingerprint pattern. Data is periodically read from the one-dimensional image sensor 24 at a predetermined timing, and the data is buffered in the RAM 14. When the movement amount detection device 29 detects that the subject (finger) has moved by a predetermined amount with respect to the data read by the one-dimensional image sensor 24, the CPU 10 captures it as image data representing a fingerprint pattern. A two-dimensional image (fingerprint image) is generated by recording in the RAM 14.

FIG. 2 shows a schematic configuration (side sectional view) of the mechanism portion of the fingerprint reading unit 20.
As shown in FIG. 2, a reading transparent plate 30 serving as a fingerprint image reading surface is provided on the casing of the mobile phone. The reading transparent plate 30 is formed, for example, in the shape of a rectangular plate with a transparent material such as acrylic or glass so that light can pass therethrough. The length of the reading transparent plate 30 in the longitudinal direction is, for example, as long as the width of the finger that is the subject (the length in the direction perpendicular to the finger moving direction). In addition, the short side direction of the reading transparent plate 30 (the short width direction of the rectangular plate) is reflected by a subject (finger) that is in contact with the reading transparent plate 30 as shown in FIG. However, it is only necessary to secure a condensable width by the SELFOC lens 22.

  In the vicinity of the reading transparent plate 30, a movement amount detection device 29 for detecting the movement amount of the finger and stabilizing the movement is provided. The movement amount detection device 29 has a rotating member formed in a roller shape, and this rotating member is provided so as to be exposed from a slit provided on the surface of the casing. When the subject is brought into contact with the reading transparent plate 30 and moved, the subject is simultaneously brought into contact with the rotating member of the movement amount detection device 29 and rotated. The movement amount detection device 29 detects the rotation of the rotating member and notifies the CPU 10 to use it to control the timing of capturing image data read by the one-dimensional image sensor 24.

  As shown in FIG. 2, the light source 21 (for example, an LED (Light Emitting Diode)), the Selfoc lens 22, and the one-dimensional image sensor 24 are fixedly held by a support member 32 in the housing. In the first embodiment, the irradiation optical axis of light emitted from the light source 21 to the reading transparent plate 30 (reading surface) and the light irradiated from the light source 21 and reflected by the surface (subject) of the reading transparent plate 30 are used. The imaging optical axis of the incident one-dimensional imaging device 24 (and the imaging optical system including the SELFOC lens 22) is normal to the reading transparent plate 30 (a line indicating a direction perpendicular to the surface of the reading transparent plate 30). On the other hand, the light source 21 and the one-dimensional imaging device 24 are arranged in a line-symmetric position so that the angle is smaller than the total reflection angle on the reading surface. For example, the light source 21 and the one-dimensional imaging device 24 are set so that the refraction angle at the reading surface formed by the irradiation optical axis and the imaging optical axis is smaller than 90 °, and is symmetrical with respect to the normal to the reading surface. And are arranged.

  In the configuration shown in the first embodiment, since the total reflection of light emitted from the light source 21 is not used, the irradiation optical axis (incident angle of irradiation light) can be reduced, and the light source 21 and the one-dimensional imaging device 24 (and the cell). There are few restrictions about the arrangement position of the Fock lens 22). For example, the arrangement positions of the light source 21 and the one-dimensional imaging element 24 can be made closer as shown in FIG. 2, optical members such as prisms can be omitted, and the optical distance can be shortened. The fingerprint reading unit 20 can be downsized.

  The Selfoc lens 22 forms an image on the one-dimensional image sensor 24 at a portion (reading surface) where the subject is pressed on the reading transparent plate 30. In addition, it is not restricted to a Selfoc lens, It is possible to use the imaging optical system comprised by a rod lens group.

  The one-dimensional imaging device 24 is formed in a strip shape by a CCD line sensor or a CMOS line sensor, and the arrangement of the imaging devices is substantially perpendicular to the moving direction of the subject, that is, parallel to the longitudinal direction of the reading transparent plate 30. It is implemented to be. For example, the one-dimensional imaging device 24 has an imaging range corresponding to the length of the reading transparent plate 30.

  In order to emphasize the surface reflected light on the reading surface, a polarizing element may be arranged in the optical axis path between the light source 21 (illumination system) and the one-dimensional imaging element 24 (imaging optical system).

  FIG. 3 is a diagram showing a state of image reading for the subject (finger) in the first embodiment. The thickness of the arrow in FIG. 3 represents the light amount, and the thicker the light, the greater the amount of light. The shading representing the fingerprint of the fingerprint image is detected as follows.

  That is, as shown in FIG. 3A, the fingerprint projection at the fingertip absorbs light emitted from the light source 21 so as to be in close contact with the reading transparent plate 30, and becomes dark because the amount of reflected light is reduced. . On the other hand, as shown in FIG. 3B, the fingerprint concave portion is not in close contact with the reading transparent plate 30, so that the amount of light absorbed by the finger is small, and the amount of reflected light is increased, resulting in brightening.

  In this way, the image data corresponding to the unevenness of the fingerprint is read by the one-dimensional image sensor 24 as the finger moves on the transparent reading plate 30. The CPU 10 generates (synthesizes) a two-dimensional image representing a fingerprint pattern by sequentially capturing a plurality of image data in accordance with the amount of movement of the subject detected by the movement amount detection device 29.

  In the above description, the subject is a finger and image data (fingerprint image) representing a fingerprint pattern is read. However, paper or the like is used as a subject to read a character or picture image recorded on paper. You may do it.

  An object such as paper does not have unevenness like a fingerprint and does not optically adhere to the reading transparent plate 30, but is light and shade in which surface reflected light is offset to light and dark depending on the presence or absence of characters or pictures recorded on paper. Can be obtained.

  In this manner, in the image reading apparatus of the first embodiment, the irradiation optical axis of the light emitted from the light source 21 and the light emitted from the light source 21 and reflected by the reading surface are incident on the reading surface of the reading transparent plate 30. The light source 21 and the one-dimensional image pickup device 24 are set so that the imaging optical axis of the one-dimensional image pickup device 24 (Selfoc lens 22) is smaller than the total reflection angle on the reading surface with respect to the normal line of the reading surface. Are placed in line-symmetric positions, restrictions on the arrangement positions of the light source 21 and the one-dimensional imaging device 24 are relaxed, and the entire apparatus can be reduced in size. Further, by arranging the light source 21 and the one-dimensional imaging device 24 to be line-symmetric, it is possible to effectively convert, for example, the unevenness of a fingerprint as light / dark information of an image using surface reflected light on the reading surface. Because it does not use total reflection, it can read image information such as text and pictures recorded on objects that are not optically closely contacted, such as paper. Reading can be realized.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
In the first embodiment, the reading transparent plate 30 is provided on the reading surface of the fingerprint reading unit 20, and the movement amount of the finger as the subject is detected by the movement amount detection device 29. In the second embodiment, the subject is examined. Is provided with a hollow transparent transparent roller 35 that rotates by being moved in pressure contact, and a movement amount reading pattern 36 provided on the outer peripheral surface of the rotary transparent roller 35 is used to detect the movement amount of the finger. . Therefore, the fingerprint reading unit 20 of the second embodiment does not require the configuration of the movement amount detection device 29 shown in FIG. About another structure, detailed description is abbreviate | omitted as the same thing as 1st Embodiment.

  FIG. 4 shows the configuration of the rotating transparent roller 35 used in the second embodiment. The rotating transparent roller 35 is made of a transparent material such as acrylic or glass so that light can be transmitted, and is mounted so as to rotate with a part of the outer peripheral surface exposed from a slit provided in the housing.

  The rotating transparent roller 35 has a hollow inside, and a light source 21 (for example, an LED (Light Emitting Diode)), a lens optical system (Selfoc lens 22), and a one-dimensional image sensor 24 are placed in the hollow. Including an imaging function unit. FIG. 5 is a cross-sectional view showing a state in which the imaging function unit is mounted in the hollow of the rotating transparent roller 35. The light source 21, the Selfoc lens 22, and the one-dimensional imaging device 24 are held by a support member 32 so as not to be interlocked with the rotation of the rotating transparent roller 35 inside the rotating transparent roller 35.

  As shown in FIG. 4, the rotating transparent roller 35 is provided with a pattern formed by making the outer peripheral surface non-uniform or a printed pattern.

  The pattern formed by making the surface shape non-uniform is formed in a step shape in which the cross-sectional shape of the shaft of the rotating transparent roller 35 changes in outer diameter step by step, and the movement amount reading pattern 36 composed of the same shape pattern is formed. It is attached over one circumference of the outer peripheral surface.

  Similarly, in the case of a print pattern, the same pattern is applied over the entire circumference of the outer peripheral surface.

  The pattern applied to the rotating transparent roller 35 is such that, for example, linear portions having a predetermined angle with respect to the axial direction of the rotating transparent roller 35 (linear portions each having a constant angle with respect to the axis) are continuous. Is formed. Note that the pattern shown in FIG. 4 is an example, and other shape patterns may be used.

  The pattern attached to the surface of the rotating transparent roller 35 is read simultaneously with the image of the subject (finger), and the position of the line-shaped image data that is sequentially read changes to capture the finger movement, that is, the fingerprint image. Timing is determined.

  The CPU 10 can generate a two-dimensional image by synthesizing image data read by the one-dimensional imaging device 24 as image data representing a fingerprint pattern in accordance with the determination of the capture timing.

  As shown in FIG. 5, the light source 21 (for example, LED (Light Emitting Diode)), the Selfoc lens 22, and the one-dimensional imaging device 24 are fixed and held by the support member 32 in the hollow of the rotating transparent roller 35. In the second embodiment, the irradiation optical axis of light irradiated from the light source 21 to the reading transparent plate 30 (reading surface) and the light irradiated from the light source 21 and reflected by the surface (subject) of the reading transparent plate 30 are reflected. The imaging optical axis of the incident one-dimensional imaging device 24 (and the imaging optical system including the Selfoc lens 22) is normal to the reading transparent plate 30 (a line indicating a direction perpendicular to the surface of the rotating transparent roller 35). On the other hand, the light source 21 and the one-dimensional imaging device 24 are arranged in a line-symmetric position so that the angle is smaller than the total reflection angle on the reading surface. For example, the light source 21 and the one-dimensional imaging device 24 are set so that the refraction angle at the reading surface formed by the irradiation optical axis and the imaging optical axis is smaller than 90 °, and is symmetrical with respect to the normal to the reading surface. And are arranged.

  In the configuration shown in the first embodiment, since the total reflection of light emitted from the light source 21 is not used, the irradiation optical axis (incident angle of irradiation light) can be reduced, and the light source 21 and the one-dimensional imaging device 24 (and the cell). There are few restrictions about the arrangement position of the Fock lens 22). For example, the arrangement positions of the light source 21 and the one-dimensional imaging device 24 can be made closer as shown in FIG. 5, optical members such as prisms can be omitted, and the optical distance can be shortened. The optical imaging system that needs to be mounted on the rotating transparent roller 35 can be downsized.

  In this way, in the fingerprint reading unit 20 of the second embodiment, the irradiation optical axis of the light emitted from the light source 21 and the irradiation from the light source 21 so as not to be interlocked with the rotation of the roller in the hollow of the rotating transparent roller 35. The light source so that the imaging optical axis of the imaging element 24 that receives the light reflected by the reading surface of the transparent rotating roller 35 is smaller than the total reflection angle on the reading surface with respect to the normal line of the reading surface. By arranging 21 and the image sensor 24 at positions that are line-symmetric, restrictions on the arrangement positions of the light source 21 and the image sensor 24 are alleviated, and the entire apparatus can be reduced in size. In addition, by making the arrangement positions of the light source 21 and the image sensor 24 line symmetrical, it is possible to effectively convert, for example, fingerprint irregularities as light / dark information of an image using surface reflected light on the reading surface, In addition, since total reflection is not used, image information such as text and pictures recorded on objects that are not optically close to each other, such as paper, can be read, which enables stable reading of images of objects. Can be realized.

  Next, correction processing for an image read in the first embodiment and the second embodiment described above will be described.

  In the configuration of the fingerprint reading unit 20 shown in the first embodiment and the second embodiment, for example, the subject (finger) is moved in contact with the imaging surface of the image sensor, so that the contact pressure at the center of the belly of the finger When the contact pressure with respect to the reading surface is moved in a non-uniform state, for example, the intensity of the image becomes strong, the read image may be distorted. Also, different image distortions may occur due to differences in movement direction (forward direction or reverse direction). Corrections are made for such image distortion.

  FIG. 6 is a diagram showing an example of a fingerprint image for explaining the first method in the correction process. FIG. 6A shows a normal fingerprint image with no distortion.

  One fingerprint image (two-dimensional image) is generated from a plurality of pieces of image data (partial fingerprint image) that are read sequentially with respect to a finger moved on the reading surface. In this case, the contact pressure with respect to the reading surface of the finger tends to be higher in the central portion than in the peripheral portion of the fingertip. For this reason, the frictional resistance is increased, and the synthesized fingerprint image is distorted by causing the central portion to shift in the direction opposite to the moving direction with respect to the peripheral portion.

  FIG. 6B shows an example of a fingerprint image read while moving a finger toward the front. FIG. 6C shows an example of a fingerprint image read while moving the finger toward the front. As shown in FIGS. 6B and 6C, fingerprint images having different distortions due to differences in finger movement directions are read.

  The CPU 10 reads two fingerprint images read by the fingerprint reading unit 20 in different movement directions (forward direction and reverse direction) with respect to the reading surface. The CPU 10 uses one of the fingerprint images as a reference, and distorts the other fingerprint image so that the evaluation value of image matching with the reference fingerprint image is maximized (similar state). . Then, the CPU 10 generates a corrected fingerprint image by correcting the fingerprint image in the direction opposite to the finger movement direction by using half of the distorted deformation amount as a correction value. Thereby, as shown in FIG. 6D, a corrected fingerprint image close to a normal fingerprint image can be obtained.

  In the above description, image matching for the entire image is used, but feature points in the fingerprint image may be used. For example, feature points may be extracted from two fingerprint images, the amount of change in the position of the corresponding feature point may be calculated, and the fingerprint image may be corrected using the intermediate value as a correction value.

  In the above description, the fingerprint image is corrected using two fingerprint images read for each finger moved in the forward direction and the reverse direction. However, the correction is performed using three or more fingerprint images. You may make it do. In this case, a corrected fingerprint image is generated so as to be close to a normal fingerprint image by performing correction so as to reflect the respective reading situations for a plurality of fingerprint images read according to different reading situations.

  FIG. 7 is a diagram illustrating an example of a fingerprint image for explaining a second method in the correction process. FIG. 7A shows a normal fingerprint image with no distortion.

  In the second method, the fingerprint image is corrected based on the reference pattern included in the image. Here, a pattern corresponding to a wrinkle appearing at the first joint of the finger is used as the reference pattern. Therefore, when the second method is used, the fingerprint reading unit 20 reads not only the fingerprint portion but also the wrinkle pattern of the first joint as shown in FIG. 7A.

  FIG. 7B shows an example of a fingerprint image read while moving the finger toward the front. As shown in FIG. 7B, distortion corresponding to the direction of finger movement occurs.

  The CPU 10 uses the fact that the pattern corresponding to the heel of the first joint is substantially linear, and performs correction processing on the entire fingerprint image so that this pattern most closely approximates the straight line. In the example of the fingerprint image shown in FIG. 7B, the distortion is greater near the center than around the finger.

  The CPU 10 generates a corrected fingerprint image by correcting the fingerprint image in a direction opposite to the finger moving direction in accordance with the distortion of the heel pattern of the first joint. Thereby, as shown in FIG.7 (c), the correction | amendment fingerprint image close | similar to a normal fingerprint image can be obtained.

  FIG. 8 is a diagram showing an example of a fingerprint image for explaining a third method in the correction process. FIG. 7A shows a two-dimensional fingerprint image that is not distorted and is read by another two-dimensional sensor.

  In the third method, a two-dimensional fingerprint image read by another two-dimensional sensor is prepared in advance, and the fingerprint image read by the fingerprint reading unit 20 is corrected based on the two-dimensional fingerprint image. . As for the two-dimensional fingerprint image, for example, a fingerprint image to be subjected to authentication processing is separately read by a reading device equipped with another two-dimensional sensor and stored in the own device. In the two-dimensional sensor, since reading is not performed while moving the finger, distortion associated with the movement of the finger does not occur, and it can be used as a reference fingerprint image described later.

  FIG. 8B shows an example of a fingerprint image read while moving a finger toward the front. FIG. 8C shows an example of a fingerprint image read while moving the finger toward the front. As shown in FIGS. 8B and 8C, fingerprint images having different distortions due to differences in finger movement directions are read.

  The CPU 10 uses the two-dimensional fingerprint image as a reference fingerprint image, distorts the fingerprint image read by the fingerprint reading unit 20, and the evaluation value of image matching with the reference fingerprint image is maximum (similar state). To be.

  Then, the CPU 10 generates a corrected fingerprint image by correcting the fingerprint image in the direction opposite to the finger moving direction using the distorted deformation amount as a correction value. As a result, as shown in FIG. 8D, a corrected fingerprint image close to a normal fingerprint image can be obtained for a fingerprint image read in any moving direction.

  In the above description of the third method, image matching for the entire image is used. However, feature points in the fingerprint image may be used. For example, feature points are extracted from two fingerprint images, the amount of change in the position of the corresponding feature point is calculated, and the fingerprint image read by the fingerprint reading unit 20 is corrected using the amount of change as a correction value. You may do it.

FIG. 9 is a diagram illustrating an example of a fingerprint image for explaining a fourth method in the correction process.
In the fourth method, a partial fingerprint image (first image) read with the finger stationary and a partial fingerprint image (second image) read at the beginning of finger movement are used. Thus, the entire fingerprint image read by the fingerprint reading unit 20 is corrected.

  In the case of using the fourth method, it is assumed that a part of the fingerprint image can be read when the finger is in contact with the reading surface in a stationary state.

  FIG. 9A shows an example of a partial fingerprint image (still image) read when the finger is in a stationary state. FIG. 9B shows an example of a partial fingerprint image (motion start image) read when the finger is started to move toward the front. FIG. 9C shows an example of the entire fingerprint image read while moving the finger forward. As shown in FIG. 9C, distortion corresponding to the moving direction of the finger occurs.

  For example, the CPU 10 sets a still image read in a still state as a reference fingerprint image, distorts the image at the start of movement, and maximizes the image matching evaluation value with the reference fingerprint image (similar state).

  Then, the CPU 10 generates a corrected fingerprint image by correcting the entire fingerprint image in the direction opposite to the finger moving direction using the distorted deformation amount as a correction value. As a result, as shown in FIG. 9D, a corrected fingerprint image close to a normal fingerprint image can be obtained.

  In the above description, correction processing is performed using a still image read in a still state before starting reading (FIG. 9A) and a motion start image read at the beginning of movement, but near the end of reading. The correction process can also be executed in the same manner as described above using the motion end image read in step 1 and the still image read when the reading of the entire fingerprint image is completed and the movement of the finger is stopped.

  In this manner, it is possible to correct different image distortions or the like caused by the difference in the moving direction, which occurs when the finger is moved with a nonuniform contact pressure on the reading surface. Therefore, it is possible to easily obtain an accurate collation result when executing a collation process for a fingerprint image. Moreover, since the fingerprint image is corrected with less distortion, it is possible to collate with a fingerprint image obtained by another type of fingerprint reading device without depending on the difference in the configuration of the fingerprint reading unit 20.

  Further, since the distortion of the fingerprint image can be corrected based on the image obtained at the time of reading (other than the third method), a corrected fingerprint image with little distortion according to the change of the finger state or environment is obtained. be able to.

  Note that the above embodiment includes inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, at least one of the problems described in the column of problems to be solved by the invention can be solved, and described in the column of the effect of the invention. In a case where at least one of the obtained effects can be obtained, a configuration in which this configuration requirement is deleted can be extracted as an invention.

1 is a block diagram showing a configuration of an electronic circuit of a mobile phone equipped with an image reading apparatus according to a first embodiment of the present invention. The schematic structure (side sectional drawing) of the mechanism part of the fingerprint reading part 20 in 1st Embodiment. The figure which shows the condition of the image reading with respect to the test object (finger) in 1st Embodiment. The figure which shows the structure of the rotation transparent roller 35 used by 2nd Embodiment. The figure which shows the state by which the imaging function part in 2nd Embodiment was mounted in the hollow of the rotation transparent roller 35 by a cross section. The figure which shows an example of the fingerprint image for demonstrating the 1st method in a correction process. The figure which shows an example of the fingerprint image for demonstrating the 2nd method in a correction process. The figure which shows an example of the fingerprint image for demonstrating the 3rd method in a correction process. The figure which shows an example of the fingerprint image for demonstrating the 4th method in a correction process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... CPU, 12 ... Memory | storage device, 14 ... RAM, 16 ... Call unit, 18 ... Display part, 19 ... Key part, 20 ... Fingerprint reading part, 21 ... Light source, 22 ... Selfoc lens (lens optical system), 24 DESCRIPTION OF SYMBOLS ... One-dimensional image sensor, 26 ... Imaging control circuit, 28 ... A / D conversion circuit, 29 ... Movement amount detection circuit, 30 ... Reading transparent plate, 32 ... Support member, 35 ... Rotating transparent roller, 36 ... Movement amount reading pattern .

Claims (6)

In an image reading device that reads an image of an object in contact with a reading surface,
An irradiation optical axis of light emitted from a light source to the reading surface and an imaging optical axis of an image sensor that receives light irradiated from the light source and reflected by the reading surface are relative to the normal line of the reading surface. The image reading apparatus is characterized in that the light source and the image sensor are arranged in a line-symmetrical position so that the angle is smaller than a total reflection angle on the reading surface.   A plurality of two-dimensional images, each of which is read in a different moving direction of the object with respect to the reading surface, from a two-dimensional image generated based on an image read by the imaging device with respect to the object moved while contacting the reading surface The image reading apparatus according to claim 1, further comprising a correction unit that performs correction based on the image.   The image reading apparatus according to claim 2, wherein the correction unit performs correction based on a reference pattern included in the two-dimensional image.   4. The two-dimensional image is a fingerprint image including a wrinkle of a first joint portion of a finger, and the correction unit performs correction based on a pattern corresponding to the wrinkle of the first joint portion. The image reading apparatus described.   A two-dimensional image generated based on an image read by the imaging device with respect to an object moved while contacting the reading surface, a first image read in a stationary state of the object, and the movement of the object The image reading apparatus according to claim 1, further comprising a correction unit configured to correct based on the second image read first. In an image reading device that reads light reflected from an object irradiated from a light source by an image sensor,
Provide a hollow transparent rotating roller that rotates by moving the object in pressure contact,
In the hollow of the transparent rotating roller, in order not to interlock with the rotation of the roller, an irradiation optical axis of light irradiated from the light source, and a reading surface that is irradiated from the light source and presses the object of the transparent rotating roller The light source and the image sensor are lined so that the imaging optical axis of the image sensor on which the reflected light is incident is at an angle smaller than the total reflection angle on the reading surface with respect to the normal line of the reading surface. An image reading device arranged at a symmetrical position.

Images