JP2008036058A - Imaging device and biometric authentication device - Google Patents

Abstract

An imaging apparatus capable of effectively suppressing the generation of noise is provided.
An imaging apparatus 100 according to the present invention includes a light receiving unit 10 in which a plurality of light receiving elements 11 are arranged, a microlens array 50 having a plurality of microlenses 51, and a space between the light receiving unit 10 and the microlens array 50. The light shielding layer 20 is provided. Here, the light shielding layer 20 includes openings 30 respectively provided corresponding to the plurality of light receiving elements 11, and the actual length d1 of the opening width of the opening 30 on the light receiving element side and the distance between the adjacent microlenses 51. , The air conversion length t0 of the distance between the vein 2001 and the apex of the microlens 51, and the air conversion of the thickness between the apex of the microlens 51 and the opening position on the light receiving unit side of the opening 30 The optical relationship with the length t1 is 1.36 · t1 / p ≦ d1 ≦ 2.4 · t1 / p + p · t1 / t0.
[Selection] Figure 1

Description

    The present invention relates to an imaging device and a biometric authentication device, and for example, relates to an imaging device and a biometric authentication device suitable for imaging a blood vessel of a living body.

  Biometric authentication that uses a part of the body of a person such as a fingerprint, iris, or blood vessel pattern as a key as a security method that does not require the use of a key or the like, is highly convenient, and is less likely to be illegally used due to loss or theft. Yes. Among them, the authentication method using a blood vessel pattern has the advantage that there is less psychological resistance because it does not associate criminal investigations like fingerprints or irradiates light directly to the eyeballs like irises. . In addition, the authentication method using the blood vessel pattern has an advantage that it is difficult to counterfeit because it uses information inside the living body, not the surface of the living body that can be easily observed.

  Conventionally, authentication using a blood vessel pattern of a finger has been realized as follows. A light source that irradiates the finger with near-infrared light and a camera that images near-infrared light that passes through the finger are installed. The camera is equipped with an optical filter that allows only light in the near-infrared region to pass through. At the time of biometric authentication, a finger is placed in near-infrared light from a light source, and an image of the finger at that time is taken with a camera. Near-infrared light passes through muscles, fats, bones, and the like in the living body, but is absorbed by pigment components such as hemoglobin and melanin in the blood.

  For this reason, the image captured by the camera is expressed in white when transmitted light is received, but the blood vessel portion is expressed in black because near-infrared light is absorbed by hemoglobin, melanin, or the like in the blood. Biometric authentication is performed by comparing the blood vessel pattern thus taken with the registered blood vessel pattern. Such biometric authentication technology is described in, for example, Patent Document 1 and Patent Document 2.

In recent years, it has been required to reduce the size and thickness of a biometric authentication apparatus that performs such biometric authentication. Conventionally, a monocular reduction optical system that uses reduction imaging of a single lens or a plurality of lenses has been used for an imaging device used in a biometric authentication device. There is a limit.
Therefore, there is an attempt to apply a compound eye optical system combining a microlens array and a plurality of light receiving elements to a biometric authentication apparatus. As a conventional compound eye optical system imaging device, for example, a technique described in Patent Document 3 is known.

In Patent Document 3, a microlens array composed of a plurality of microlenses formed on a transparent substrate, and a light receiving section (contact image) provided facing the microlens array and having a plurality of light receiving elements (light detection sections). And a light shielding layer (light shielding spacer) provided between the microlens array and the light receiving unit, and a cylindrical shape provided in an area sandwiched between the microlens and the light receiving element in the light shielding layer. An imaging device including a plurality of openings (light transmission holes) having at least a part of the light absorption surface as disclosed is disclosed.
JP 2005-312749 A (particularly, paragraphs 0027 to 0034, paragraphs 0064 to 0070, FIG. 3 and FIG. 8) Japanese Patent Laying-Open No. 2005-71118 (particularly, paragraph 0016, FIG. 1) Japanese Patent Laid-Open No. 3-157602

  FIG. 5 shows a longitudinal sectional view of a conventional imaging device disclosed in Patent Document 3. The technique described in Patent Document 3 is a light-shielding layer (light-shielding layer) having a plurality of cylindrical openings (light-transmitting holes) 30A between a microlens array (lens array plate) 50A and a light-receiving part (contact image sensor) 10A. Spacer) 20A is formed. The plurality of cylindrical openings 30A are formed corresponding to the positions of the microlens (microlens) 51A and the light receiving element (light detection unit) 11A.

  Moreover, the black coating material is apply | coated inside 30 A of openings, and functions as a light absorption surface. In the technique described in Patent Document 3, by adopting such a configuration, light from the adjacent microlens 51A enters the light receiving element 11A, which is a disadvantage of the compound-eye optical system. The effect is suppressed.

  However, although the technique described in Patent Document 3 can remove the crosstalk from the adjacent microlens 51A, the light receiving element 11A has all the desired imaging area “area A” of the microlens 51A corresponding thereto. Since the projection information “region B” is incident, there is a problem that the image is blurred and the quality of the image captured by the light receiving element 11A is deteriorated.

  In particular, when the distance between the microlens array 50A and the light receiving element 11A is narrowed in response to the demand for thinner thickness, the “region B” becomes wider, and the quality of the image captured by the light receiving element 11A is further significantly deteriorated. Become.

  The present invention has been made to solve such a problem, and an object thereof is to provide an imaging apparatus and a biometric authentication apparatus that can effectively suppress the generation of noise.

An imaging apparatus according to the present invention includes a light receiving unit in which a plurality of light receiving elements are arranged, a microlens arranged in correspondence with each of the plurality of light receiving elements, and a light shielding layer provided between the light receiving unit and the microlens. The light-shielding layer includes an opening provided corresponding to each of the plurality of light receiving elements, the actual length d1 of the opening width of the opening on the light receiving element side, and the distance between adjacent microlenses. , The air-converted length t0 of the distance between the imaging object existing in the direction from the light receiving element toward the microlens and the apex of the microlens, and the aperture on the light receiving unit side of the apex and opening of the microlens The relationship between the thickness and the air equivalent length t1 is 1.36 · t1 / p ≦ d1 ≦ 2.4 · t1 / p + p · t1 / t0.
By adopting such a configuration, it is possible to suppress the incidence of information from other than the desired imaging region to the light receiving element, and to effectively suppress the generation of noise.

  Here, it is preferable that the relationship among d1, p, t0, and t1 is 1.6 · t1 / p ≦ d1 ≦ 1.9 · t1 / p + p · t1 / t0. Thereby, generation | occurrence | production of noise can be suppressed more reliably. The opening is formed such that the opening area on the light receiving element side of the opening is equal to or smaller than the opening area on the microlens side. In addition, at least a portion of the light shielding layer that forms a boundary with the opening is made of a light absorbing member, and at least a portion other than the opening on the surface facing the light receiving element or the surface facing the microlens is light. It is an absorbing member or a light reflecting member. Further, the actual length d2 of the opening width on the light receiving element side of the opening, the air conversion length t2 of the thickness between the apex of the microlens and the opening position of the opening on the microlens side, t0, t1, The relationship with p is preferably d2 ≧ p (1−t2 / t1 + t2 / t0).

  Moreover, it is preferable that the relationship between t1, t2, d1, d2, and p is t2 ≦ t1 · (1− (d1 + d2) / (2 · p + d1)). Moreover, it is preferable that the optical relationship between the air conversion length t3 of the thickness between the light receiving element and the opening position of the opening on the light receiving element side and t1 is t3 <t1 / 3. The inside of the opening may be filled with a material that is transparent to at least one wavelength in the wavelength range that can be received by the light receiving element. Moreover, you may provide the optical filter which interrupts | blocks that a visible ray injects into a light receiving element.

A biometric authentication apparatus according to the present invention includes a light source that irradiates light in the direction of a biological part, an imaging part that images a biological part irradiated with light from the light source, a storage part that stores a plurality of biological information, and an imaging part A biometric authentication device comprising: a collation unit that collates biometric information obtained from a biometric part to be imaged with biometric information stored in the storage unit; and a control unit that performs biometric authentication according to a collation result of the collation unit The imaging unit includes a light receiving unit in which a plurality of light receiving elements are arranged, a microlens arranged in correspondence with each of the plurality of light receiving elements, and a light shielding layer provided between the light receiving unit and the microlens. The light-shielding layer includes an opening provided corresponding to a plurality of light receiving elements, and is adjacent to the actual length d1 of the opening width of the opening on the light receiving element side. The actual length p between the microlenses and the light receiving element The air conversion length t0 of the distance between the living body part existing in the direction from the microlens to the microlens and the apex of the microlens, and the air conversion of the distance between the apex of the microlens and the opening position on the light receiving part side of the opening The relationship with the length t1 is 1.36 · t1 / p ≦ d1 ≦ 2.4 · t1 / p + p · t1 / t0.
By adopting such a configuration, it is possible to suppress the incidence of information from outside the desired imaging region to the light receiving element, and to effectively suppress the generation of noise.

  Here, it is preferable that the relationship among d1, p, t0, and t1 is 1.6 · t1 / p ≦ d1 ≦ 1.9 · t1 / p + p · t1 / t0. Thereby, generation | occurrence | production of noise can be suppressed more reliably. The opening is formed such that the opening area on the light receiving element side of the opening is equal to or smaller than the opening area on the microlens side. In addition, at least a portion of the light shielding layer that forms a boundary with the opening is made of a light absorbing member, and at least a portion other than the opening on either the surface facing the light receiving element or the surface facing the microlens. Consists of a light absorbing member or a light reflecting member. Further, the actual length d2 of the opening width on the microlens side of the opening, the air conversion length t2 of the thickness between the apex of the microlens and the opening position on the microlens side of the opening, t0, t1, The relationship with p is preferably d2 ≧ p (1−t2 / t1 + t2 / t0).

  Moreover, it is preferable that the relationship between t1, t2, d1, d2, and p is t2 ≦ t1 (1− (d1 + d2) / (2 · p + d1)). Moreover, it is preferable that the relationship between the air conversion length t3 of the thickness between the light receiving element and the opening position of the opening on the light receiving element side and t1 is t3 <t1 / 3. In addition, the inside of the opening may be filled with a material that is transparent to at least one wavelength between 680 nm and 1200 nm. Moreover, you may provide the optical filter which interrupts | blocks that a visible ray injects into a light receiving element.

  According to the present invention, generation of noise can be effectively suppressed.

Embodiment 1 of the Invention
The configuration of the biometric authentication device according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing the configuration of the imaging unit of the biometric authentication apparatus according to Embodiment 1 of the present invention. FIG. 2 is a block diagram showing the configuration of the biometric authentication apparatus according to the present invention. In addition, each dimension shown by FIG. 1 has shown actual length.
As shown in FIG. 2, the biometric authentication apparatus 1000 according to Embodiment 1 of the present invention includes an imaging unit 100, an image processing unit 200, light sources 301 and 302, a storage unit 400, a verification unit 500, A control unit 600 is provided.

The imaging unit 100 is connected to the image processing unit 200 and images a pattern (biological information) of a vein 2001 in a finger 2000 as a biological part irradiated with near infrared light from the light sources 301 and 302. As shown in FIG. 1, the finger 2000 is disposed on the upper part of the imaging unit 100. The configuration of the imaging unit 100 will be described later in detail.
The image processing unit 200 is connected to the image capturing unit 100 and the control unit 600 and performs image processing such as correction on the image data of the pattern of the vein 2001 converted by the light receiving unit 10 of the image capturing unit 100.

The light sources 301 and 302 are connected to the control unit 600. The light sources 301 and 302 are composed of a plurality of near-infrared light emitting elements, and near-infrared light (wavelength: 680 nm to 1200 nm, preferably 800 nm to 950 nm) in a direction that transmits the finger 2000 disposed on the upper part of the imaging unit 100. ).
The storage unit 400 is connected to the control unit 600. The storage unit 400 stores a plurality of vein patterns imaged by the imaging unit 100 in advance.

The collation unit 500 is connected to the control unit 600. The collation unit 500 collates the vein pattern in the finger 2000 imaged by the imaging unit 100 with the vein pattern stored in advance in the storage unit 400 under the control of the control unit 600.
The control unit 600 is connected to the image processing unit 200, the light sources 301 and 302, the storage unit 400 and the collation unit 500, and controls these 200, 301, 302, 400 and 500. Further, the control unit 600 performs biometric authentication according to the collation result of the collation unit 500.

Next, a biometric authentication method performed by the biometric authentication device 1000 will be described.
First, the finger 2000 is placed on the top of the imaging unit 100. Next, the near-infrared light is irradiated to the finger 2000 using a plurality of near-infrared light emitting elements of the light sources 301 and 302. Near-infrared light passes through the inside of the finger 2000 and enters each light receiving element 11 through the optical filter 60, the microlens array 50, and the light shielding layer 20. Each light receiving element 11 receives a pattern image of the vein 2001 in the finger 2000 with infrared light, and the light receiving unit 10 converts the image of the vein 2001 pattern in the finger 2000 received by each light receiving element 11 into image data. To do. In this way, the blood vessel pattern of the vein 2001 in the finger 2000 is imaged by the imaging unit 100.

  Next, the image processing unit 200 performs image processing such as correction on the image data converted by the light receiving unit 10 of the imaging unit 100. Specifically, processing such as removal of unclear portions from the imaged vein 2001 pattern is performed. Next, the collation unit 500 collates the pattern of the vein 2001 in the finger 2000 imaged by the imaging unit 100 with the vein pattern stored in advance in the storage unit 400. Then, control unit 600 performs biometric authentication according to the collation result of collation unit 500.

  Specifically, when the collation unit 500 determines that the vein pattern in the finger 2000 captured by the imaging unit 100 matches the vein pattern stored in advance in the storage unit 400, the control unit 600 Generates an authentication success signal and causes the authentication result output means such as a display unit (not shown) to output the authentication result in accordance with the authentication success signal. On the other hand, when the collation unit 500 determines that the vein pattern in the finger 2000 captured by the imaging unit 100 does not match the vein pattern stored in advance in the storage unit 400, the control unit 600 performs authentication. A failure signal is generated, and an authentication result is output to an authentication result output means such as a display unit (not shown) according to the authentication failure signal.

  Next, a configuration around the imaging unit 100 will be specifically described. As shown in FIG. 1, light sources 301 and 302 configured by arranging a plurality of near-infrared light emitting elements on the both sides of the finger 200 on the upper side of the imaging unit 100 are provided. As shown in FIG. 1, the light sources 301 and 302 are provided so as to irradiate near-infrared light in a direction that transmits a finger 2000 disposed on the upper part of the imaging unit 100. In addition, the plurality of near-infrared light emitting elements of the light sources 301 and 302 are arranged along the finger 2000 disposed on the upper part of the imaging unit 100. The vein pattern in the finger 2000 is imaged by the imaging unit 100 in a state where the finger 2000 is arranged on the upper part of the imaging unit 100 and irradiated with near-infrared light emitted from the light source 300.

  In FIG. 1, the light sources 301 and 302 are arranged on both sides of the finger 2000 so that near infrared light emitted from the light sources 301 and 302 is emitted from both sides of the finger 2000 toward the finger 2000. However, the light sources 301 and 302 are arranged on the upper side of the finger 2000 so that the near infrared light emitted from the light sources 301 and 302 is irradiated from the upper side of the finger 2000 toward the finger 2000. Also good. Alternatively, the light sources 301 and 302 may be arranged below the finger 2000 so that near infrared light emitted from the light sources 301 and 302 is emitted from the lower side of the finger 2000 toward the finger 2000. Good. In FIG. 1, the two light sources 301 and 302 are provided. However, the number of light sources is not limited to two, and may be one or three or more.

The imaging unit 100 includes a light receiving unit 10, a light shielding layer 20, an opening 30, a microlens array 50, and an optical filter 60.
As shown in FIG. 1, a plurality of light receiving elements 11 are arranged in the light receiving unit 10 at regular intervals. The light receiving element 11 only needs to be sensitive to near infrared light, and may be configured using a CCD (Charge Coupled Devices) or a CMOS (Complementary Metal Oxide Semiconductor). In addition, you may form each light receiving element 11 with the aggregate | assembly of a some light receiving element further.

  The light shielding layer 20 is provided between the light receiving unit 10 and the microlens array 50. The light shielding layer 20 is formed on the surface of the microlens array 50 opposite to the surface on which the microlenses 51 are formed. A light absorbing member is used as the material of the light shielding layer 20, and for example, a pigment or a photosensitive resin is used.

  A plurality of openings 30 are formed corresponding to the light receiving element 11 by opening the light shielding layer 20. Each opening 30 is provided to control an incident optical path of light incident on each light receiving element 11 from each microlens 51. That is, by appropriately setting the opening width of the opening 30 or the like, light incident from other than a desired region, light from the gap between adjacent microlenses 51, light from other microlenses 51, So-called crosstalk is absorbed by the inner wall of the opening 30 to suppress the generation of noise.

  As shown in FIG. 1, the opening 30 is formed such that the opening area of the opening 30 on the light receiving element 11 side is equal to or smaller than the opening area on the microlens 51 side. A transmissive portion 31 is formed inside each opening 30. Each transmission part 31 is formed by filling a transparent resin that is transparent to near infrared light inside each opening 30. The specific opening width and the like of the opening 30 will be described in detail later. In addition, as a transparent material which forms each permeation | transmission part filled inside each opening part 30, what is necessary is just a member which is transparent with respect to at least 1 wavelength in the wavelength range of 680 nm to 1200 nm, for example, transparent glass Transparent resins such as epoxy and acrylic are used. Also, each transmission part 31 formed inside each opening 30 may be a cavity.

  The microlens array 50 is provided with a plurality of convex microlenses 51. The microlens array 50 is configured, for example, by arranging a plurality of microlenses 51 on a transparent substrate. The plurality of microlenses 51 are arranged corresponding to the plurality of light receiving elements 11. That is, the distance between adjacent microlenses 51 is set to be approximately the same as the distance between adjacent light receiving elements 11.

The focal length of each microlens 51 is set so that light from the vein 2001 in the finger 2000 that is the imaging target is condensed on the surface of the opening 30 on the light receiving element 11 side. Transparent resin or transparent glass is used as the material of the microlens array 50. Each microlens 51 may be a refractive lens or a diffractive lens.
The optical filter 60 is provided on the imaging object side of the microlens array 50 so as to block visible light from entering each light receiving element 11. The optical filter 60 only needs to block visible light and transmit at least one wavelength of near infrared light, particularly in the wavelength range of 680 nm to 1200 nm, and may be a light absorption type or a reflection type due to light interference.

  Here, as shown in FIG. 1, the actual length of the opening width of the opening 30 on the light receiving element 11 side is d1, the actual length of the distance between the adjacent microlenses 51 is p, and the inside of the finger 2000 that is the imaging object Tn0 is the actual length of the distance between the vein 2001 and the apex of the microlens 51, and tn1 is the actual length of the thickness between the apex of the microlens 51 and the opening position of the opening 30 on the light receiving element 11 side. . The air-equivalent length t0 of the distance between the vein 2001 in the finger 2000 that is the imaging object and the apex of the microlens 51 is one type or a plurality of substances that exist between the vein 2001 and the apex of the microlens 51, respectively. 1 is defined as the sum of the values divided by the respective refractive indexes. In the case of FIG. 1, t0 = (depth from the surface of the finger 2000 on the light receiving element side to the vein 20001) / (refractive index of the finger 2000). + (Thickness of the optical filter 60) / (refractive index of the optical filter 60). Needless to say, tn0 = (depth from the surface of the finger 2000 on the light receiving element 11 side to the vein 2001) + (thickness of the optical filter 60). Similarly, the air equivalent length of the thickness between the apex of the microlens 51 and the opening position of the opening 30 on the light receiving element 11 side is defined as t1.

At this time, the relationship between d1, p, t0, and t1 is
1.36 · t1 / p ≦ d1 ≦ 2.4 · t1 / p + p · t1 / t0 (1)
Set to be. By doing in this way, since the light with the information from the area | region exceeding a desired imaging area | region is suppressed injecting into the light receiving element 11, generation | occurrence | production of noise can be suppressed effectively.

  When the light from the imaging object is condensed on the surface of the opening 30 on the side of the light receiving element 11 by the microlens 51, the light spot size S has a light wavelength of λ and a lens opening diameter of D as wave optics. Therefore, it can be roughly estimated as S = 2 · λ · t1 / D. When λ is 680 nm, which is the shortest wavelength value generally used in vein authentication, and D≈p, S = 1.36 · t1 / p. Therefore, when d1 is smaller than 1.36 · t1 / p, the amount of received light decreases and the image becomes dark. Therefore, d1 needs to be 1.36 · t1 / p or more.

  Similarly, the light spot size S of 1200 nm, which is the longest wavelength value generally used in vein authentication, can be estimated as 2.4 · t1 / p. Further, of the light from the imaging object, the light from the position away from the optical axis of the microlens 51 by p / 2 is from the optical axis of the microlens 51 on the surface of the opening 30 on the light receiving element 11 side ( p / 2) · (t1 / t0). Light that reaches a position farther than this is light having information from a position that is p / 2 or more away from the optical axis of the microlens 51 in the imaging target, that is, a region that exceeds the desired imaging area, and becomes a noise component. .

  From the above, it can be seen that when d1 exceeds 2.4 · t1 / p + p · t1 / t0, a noise component is incident on the light receiving element. In this case, since the image has a lot of noise and poor quality, d1 needs to be 2.4 · t1 / p + p · t1 / t0 or less.

  The optimum wavelength range used for vein authentication is 800 nm to 950 nm. The light spot size at a wavelength of 800 nm is 1.6 · t1 / p, and the light spot size at a wavelength of 950 nm is 1.9 · t1 / p.

Therefore, the relationship between d1, p, t0, and t1 is
1.6 · t1 / p ≦ d1 ≦ 1.9 · t1 / p + p · t1 / t0 (2)
It is more preferable to set so that noise can be effectively removed.

  As shown in FIG. 1, when the actual length of the opening width of the opening 30 on the microlens 51 side is d2, light can be efficiently incident on the light receiving element 11 if d2 is equal to or greater than d1. .

Further, as shown in FIG. 1, when the air equivalent length of the thickness between the apex of the micro lens 51 and the opening position of the opening 30 on the micro lens 51 side is t2, the light from the imaging object is reflected. Of these, light from a position away from the optical axis of the microlens 51 by p / 2 passes through the microlens 51 and then geometrically optically passes through the microlens 51 on the opening position on the microlens 51 side. Passes through a position away from the axis by a maximum of p / 2 · (1−t2 / t1 + t2 / t0). Therefore, the relationship between d2, t0, t1, and p is
d2 ≧ p (1−t2 / t1 + t2 / t0) (3)
If the above condition is satisfied, noise can be suppressed, and light having necessary information can be efficiently incident on the light receiving element 11 without causing a loss due to light shielding of the light shielding layer 20.

Also, the relationship between t1, t2, d1, d2, and p is
t2 ≦ t1 (1− (d1 + d2) / (2 · p + d1) (4)
It is preferable that By doing so, the light from the other microlenses 51 can be prevented from entering the light receiving element, that is, the occurrence of crosstalk can be suppressed, so that the generation of noise can be more effectively suppressed.

Further, as shown in FIG. 1, when the air equivalent length of the thickness between the light receiving element 11 and the opening position of the opening 30 on the light receiving element 11 side is t3, the relationship between t1 and t3 is
t3 <t1 / 3 (5)
It is preferable that By doing so, the light from the other microlenses 51 can be reliably prevented from entering the light receiving element after passing through the adjacent opening 30, that is, the occurrence of crosstalk can be suppressed. Occurrence can be suppressed more effectively.

  Next, a method for manufacturing the imaging unit according to Embodiment 1 of the present invention will be described with reference to the drawings. By fabricating the light receiving unit 10 in which a plurality of light receiving elements 11 are arranged, the light shielding layer 20 and the opening 30, and the microlens array 50, respectively, and sequentially arranging these as shown in FIG. The imaging unit 100 is completed.

First, a method for manufacturing the microlens array 50 will be described with reference to the drawings. FIG. 3 is a diagram showing a method for manufacturing a microlens array.
First, as shown in FIG. 3A, a glass transparent substrate 52 is prepared, and a lens is formed by applying a photosensitive resin (negative transparent resist) over the entire area of the transparent substrate 52. Layer 510 is formed. Application methods include spin coating and slit coating. Here, for example, a quartz glass substrate (refractive index of 1.45) having a size of 5 inches and a thickness of 300 μm is used as the transparent substrate 52.

Next, as shown in FIG. 3B, the lens forming layer 510 is patterned using a mask (not shown) so that the lens forming layer 510 has a plurality of cylindrical shapes. Here, the mask is formed corresponding to the shape of the microlens 51.
Next, as shown in FIG. 3C, heat treatment is performed on the cylindrical lens forming layer 510 formed on the transparent substrate 52 to cure the lens forming layer 510 into the shape of a microlens.

  Next, as shown in FIG. 3D, the shape of the microlens is transferred onto the transparent substrate 52 by etching. Then, as shown in FIG. 3E, the microlens 51 is formed on the transparent substrate 52.

  As described above, the microlens array 50 is completed. Here, the distance between the apexes of adjacent microlenses 51 is set to 100 μm, and the diameter of each microlens is set to 97 μm. Further, the focal length of each microlens 51 is set so that the light from the vein 2001 in the finger 2000 is condensed at the center of the opening 30 on the light receiving element 11 side. Specifically, the focal length of each microlens 51 is set by adjusting the thickness of the lens forming layer 510 and the etching rate ratio.

Next, a method for forming the light shielding layer 20 and the opening 30 will be described.
A transparent photosensitive resin (transparent resist) is applied over the entire surface of the microlens array 50 opposite to the surface on which the microlenses 51 are formed. Next, a cylindrical transmission part 31 corresponding to the microlens 51 is formed by performing exposure and development using a mask.
Here, the thickness of the transparent photosensitive resin is 345 μm, and the diameter of the cylinder is 75 μm. Moreover, the transmission part 31 was transparent with respect to near-infrared light, and the refractive index was 1.60.

Next, after injecting a black photosensitive resin as a light absorbing member between the transmissive portions 31, the absorbing member is cured to form the light shielding layer 20. The black photosensitive resin has a thickness of 350 μm so as to completely cover the transmission part 31.
Further, an etching process is performed on the surface of the light shielding layer 20 opposite to the surface facing the microlens 50 to form an opening on the light receiving element 11 side. Here, the diameter of the opening is set to 12 μm.

  As described above, the light shielding layer 20 and the opening 30 are formed on the microlens array 50. Here, the distance between the adjacent openings 30 is 100 μm, the opening width of the opening 30 on the microlens 51 side is 75 μm, the opening width of the opening 30 on the light receiving element 11 side is 12 μm, and the thickness of the opening is 350 μm (transparent resin 345 μm + air 5 μm).

  In the above, the example in which the light shielding layer is formed on the surface opposite to the surface on which the microlens 51 of the microlens array 50 is formed has been described, but it may be formed on the light receiving unit 10. Further, a separate light shielding layer holding substrate may be provided, and a light shielding layer may be formed thereon.

  As the light receiving unit 10, a commercially available one using a double gate thin transistor for the plurality of light receiving elements 11 is used. Here, the distance between the adjacent light receiving elements 11 was 100 μm, and the size of the light receiving unit 10 was 15 mm × 20 mm. Further, a protective insulating layer made of silicon oxide having a refractive index of 1.50 is formed on the electrode of the double gate type thin transistor, and a transparent resin layer having a refractive index of 1.50 is further formed thereon with a thickness of 50 μm. Was formed.

Next, as shown in FIG. 1, for example, alignment marks are formed so that the light receiving unit 10 in which a plurality of light receiving elements 11 are arranged, the light shielding layer 20, the transmission unit 31, and the microlens array 50 are sequentially stacked. And stick together. Then, the optical filter 60 is attached on the surface opposite to the surface facing the light shielding layer 20 of the microlens array 50. Here, the thickness of the optical filter 60 was 500 μm. The refractive index of the optical filter 60 was 1.5. And finally, it cut out to the magnitude | size of 16 mm x 21 mm using the dicing blade.
By performing the above operations, the imaging unit 100 is manufactured.

The vein 2001 in the finger 2000 is imaged using the imaging unit 100 manufactured in this way.
As shown in FIG. 1, the finger 2000 is placed on the optical filter 60 provided on the upper part of the imaging unit 100, and the imaging unit is set to a position at a depth of 2.5 mm from the epidermis of the finger 2000. 100. In general, the finger vein is present at a depth of 2.5 mm from the epidermis of the finger. The refractive index of the finger skin with respect to near-infrared light is 1.34.

At this time, an air-equivalent length t0 of the distance between the vein 2001 in the finger 2000 that is the imaging target and the apex of the microlens 51 is calculated.
t0 = 2500 / 1.34 + 500 / 1.5 = 2199 (μm) (6)
Next, the air equivalent length t1 between the apex of the micro lens 51 and the opening position of the opening 30 on the light receiving element 11 side is calculated.
t1 = 300 / 1.45 + 345 / 1.6 + 5/1 = 428 (μm) (7)

Next, the air equivalent length t2 between the apex of the micro lens 51 and the opening position of the opening 30 on the micro lens 51 side is calculated.
t2 = 300 / 1.45 = 207 (μm) (8)
Next, an air equivalent length t3 between the light receiving element 11 and the opening position of the opening 30 on the light receiving element 11 side is calculated.
t3 = 50 / 1.5 = 33 (μm) (9)

Here, when the calculation results of the equations (8) to (9) are substituted into the equation (2), the following equation (10) is obtained, and the above d1 = 12 (μm) satisfies the condition of the equation (10). It becomes.
6.9 (μm) ≦ d1 ≦ 27.6 (μm) (10)
Further, when the calculation results of the equations (8) to (9) are substituted into the equation (3), the following equation (11) is obtained, and the above d2 = 75 (μm) satisfies the condition of the equation (11). Become.
d2 ≧ 61 (μm) (11)

Further, when the calculation results of the equations (7) and (8) are substituted into the equation (4), the following equation (12) is obtained, and the above-described t2 = 205 (μm) satisfies the condition of the equation (12). Become.
t2 <252 (μm) (= t1 · (1− (d1 + d2) / (2 · p + d1))) (12)
Further, when the calculation results of the expressions (7) and (8) are substituted into the expression (5), the following expression (13) is obtained, and the above-described t3 = 33 (μm) satisfies the condition of the expression (13). Become.
t3 <141 (μm) (= t1 / 3) (13)

  Using the imaging unit 100 manufactured in this way, an attempt was made to image the vein 2001 in the finger 2000, and the comparison was made with an image captured by the imaging unit in which all of the light shielding layer 20 manufactured as a comparison was made of a transparent resin. An image with little noise was obtained.

Embodiment 2 of the Invention
The configuration of the biometric authentication device according to the second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a cross-sectional view schematically showing the configuration of the imaging unit 101 of the biometric authentication apparatus according to Embodiment 2 of the present invention. Each dimension shown in FIG. 4 indicates the actual length.

  In the first embodiment, as shown in FIG. 1, a plurality of microlenses 51 are formed on the surface of the microlens array 50 on the finger 2000 side, whereas in the second embodiment, as shown in FIG. As described above, the difference is that a plurality of microlenses 51 are formed on the surface of the microlens array 50 on the light receiving unit 10 side.

In the first embodiment, as shown in FIG. 1, an optical filter 60 that blocks visible light from entering the light receiving element is provided as a separate member from the microlens array 50. In the second embodiment, as shown in FIG. 4, it is obtained by applying a resin that absorbs visible light to the surface of the microlens array 50 opposite to the surface on which the plurality of microlenses 51 are formed. The difference is that the optical filter 60 is integrated with the microlens array 51 by providing the visible light absorbing layer 80 and the hard coat layer 70 thereon.
It should be noted that the relationships represented by the equations (1) to (5) in the first embodiment are also applied as they are in the second embodiment.

  By doing so, as in the first embodiment, light incident from other than the desired imaging region, light from the gap between adjacent microlenses 51, light from other microlenses 51, so-called cross Since the talk is prevented from entering the light receiving element 11, the generation of noise can be effectively suppressed.

  Next, a method for manufacturing the imaging unit according to Embodiment 2 of the present invention will be described with reference to the drawings. As shown in FIG. 4, a light receiving unit 10 in which a plurality of light receiving elements 11 are arranged, a light blocking layer 20 and an opening 30 formed on the light blocking layer holding substrate 40, and a microlens array 50 are produced. The image pickup unit 101 is completed by sequentially stacking these.

First, the microlens array 50 is manufactured according to the description of FIG.
Specifically, the microlens 51 is formed on a transparent substrate 52 which is a quartz glass substrate (refractive index: 1.45) having a size of 5 inches and a thickness of 300 μm. At this time, the distance between the apexes of adjacent microlenses 51 is set to 100 μm, and the diameter of each microlens is set to 95 μm. In addition, the focal length of each microlens 51 is set so that light from the vein 2001 in the finger 2000 is collected at the center of the opening 30 on the light receiving element 11 side. Specifically, the focal length of each microlens 51 is set by adjusting the thickness of the lens forming layer 510 and the etching rate ratio.

Further, visible light absorption is achieved by applying and curing a commercially available resin that is transparent to near-infrared light and absorbs visible light on the surface of the microlens array 50 opposite to the surface on which the microlenses 51 are formed. Layer 80 is formed.
Further, the hard coat layer 70 is formed by applying a commercially available hard coat material on the surface of the visible light absorbing layer 80 opposite to the surface facing the microlens array 50. As described above, the optical filter 60 integrated on the microlens array 50 is manufactured. At this time, the refractive index of both the visible light absorption layer 80 and the hard coat layer was 1.60, and the total thickness of both was 100 μm.

Next, the light shielding layer 20 and the opening 30 are formed on the light shielding layer holding substrate 40.
Specifically, after forming the columnar transmission part 31 on the light-shielding layer holding substrate 40 by photolithography, the light-shielding layer 40 is formed by injecting a black photosensitive resin between the transmission parts 31 as a light absorbing member. Then, the opening 30 is formed by an etching process. At this time, the distance between the adjacent openings 30 is 100 μm, the opening width of the opening 30 on the microlens 51 side is 85 μm, the opening width of the opening 30 on the light receiving element 11 side is 12 μm, and the thickness of the opening 30 is The light shielding layer 20 and the opening 30 were formed on the light shielding layer holding substrate 40 so as to be 300 μm (transparent resin 295 μm + air 5 μm).

Note that the distance between the adjacent openings 30 corresponds to the distance between the apexes of the microlenses 51. The light shielding layer holding substrate 40 is a BK7 substrate (refractive index of 1.51) having a size of 5 inches and a thickness of 200 μm. Moreover, the refractive index of the transmission part 31 was 1.60.
In the above, an example in which the light shielding layer is formed on the light shielding layer holding substrate 40 has been described, but it may be formed on the light receiving unit 10.

  As the light receiving unit 10, a commercially available one using a CMOS sensor in which minute light receiving elements are arranged in a 15 mm × 20 mm region at intervals of 10 μm as a plurality of light receiving elements 11 is used. Here, the CMOS sensor is divided by 100 μm × 100 μm, and each region is used as each light receiving element 11. The thickness of the protective layer (silicon oxide) formed on the light receiving portion of the CMOS sensor was 1 μm or less.

Next, as shown in FIG. 4, the light receiving unit 10 in which the plurality of light receiving elements 11 are arranged, the light shielding layer 20 and the transmission unit 31, the light shielding layer holding substrate 40, and the microlens array 50 are sequentially stacked. For example, they were bonded using alignment marks.
And finally, it cut out to the magnitude | size of 16 mm x 21 mm using the dicing blade.
The imaging unit 101 is manufactured by performing the above operations.

The vein 2001 in the finger 2000 will be imaged using the imaging unit 101 manufactured in this way.
As shown in FIG. 4, the finger 2000 is placed on the optical filter 60 provided on the upper part of the image pickup unit 101, and the position of the depth of 2.5 mm from the skin of the finger 2000 is set as an image pickup target. 101.

At this time, the air equivalent length t0 of the distance between the vein 2001 in the finger 2000 that is the imaging object and the apex of the microlens 51 is calculated.
t0 = 2500 / 1.34 + 100 / 1.6 + 300 / 1.45 = 2135 (μm) (14)
Next, the air equivalent length t1 between the apex of the micro lens 51 and the opening position of the opening 30 on the light receiving element 11 side is calculated.
t1 = 200 / 1.51 + 295 / 1.6 + 5/1 = 322 (μm) (15)

Next, the air equivalent length t2 of the distance between the apex of the micro lens 51 and the opening center part of the opening 30 on the micro lens 51 side is calculated.
t2 = 200 / 1.51 = 132 (μm) (16)
Next, an air equivalent length t3 between the light receiving element 11 and the opening position of the opening 30 on the microlens 30 side is calculated.
t3 = 1 / 1.5 = 33 (μm) (17)

Here, when the calculation results of the equations (14) to (16) are substituted into the equation (2), the result is as follows, and the above-described d1 = 12 (μm) satisfies the condition of the equation (18).
5.1 (μm) ≦ d1 ≦ 21.2 (μm) (18)
Further, when the calculation results of the equations (14) to (16) are substituted into the equation (3), the result is as follows, and the above d2 = 85 (μm) satisfies the condition of the equation (19).
d2 ≧ 65 (μm) (19)

Further, when the calculation results of the equations (14) and (15) are substituted into the equation (4), the following is obtained, and the above-described t2 = 133 (μm) satisfies the condition of the equation (20).
t2 <189 (μm) (= t1 · (1− (d1 + d2) / (2 · p + d1))) (20)
Further, when the calculation results of the expressions (14) and (15) are substituted into the expression (5), the following is obtained, and the above-described t3 = 0.67 (μm) satisfies the condition of the expression (21).
t3 <107 (μm) (= t1 / 3) (21)

  When imaging of the vein 2001 in the finger 2000 was attempted using the imaging unit 101 manufactured in this way and compared with an image captured by the imaging unit in which all of the light shielding layer 20 is made of a transparent resin as a comparison, noise was clearly observed. I was able to obtain an image with little.

  The above description describes the embodiment of the present invention, and the present invention is not limited to the above embodiment. Moreover, those skilled in the art can easily change, add, and convert each element of the above embodiment within the scope of the present invention.

It is sectional drawing which shows typically the structure of the imaging part of the biometrics apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the biometrics apparatus which concerns on this invention. It is a figure which shows the manufacturing method of a micro lens array. It is sectional drawing which shows typically the structure of the imaging part of the biometrics apparatus which concerns on Embodiment 2 of this invention. It is a longitudinal cross-sectional view of the imaging device of the conventionally well-known example shown by patent document 3. FIG.

Explanation of symbols

1000 biometric authentication device, 100, 101 imaging unit, 10 light receiving unit,
11 light receiving element, 20 light shielding layer, 30 opening, 31 transmitting part,
40 light-shielding layer holding substrate, 50 microlens array,
51 microlens, 52 transparent substrate, 60 optical filter,
70 hard coat layer, 80 visible light absorbing layer,
200 image processing unit, 301, 302 light source, 400 storage unit,
500 verification unit, 600 control unit, 2000 fingers

Claims (18)

An imaging apparatus comprising: a light receiving unit in which a plurality of light receiving elements are arranged; a microlens arranged corresponding to each of the plurality of light receiving elements; and a light shielding layer provided between the light receiving unit and the microlens. There,
The light shielding layer includes openings provided corresponding to the plurality of light receiving elements, respectively.
The actual length d1 of the opening width on the light receiving element side of the opening, the actual length p of the distance between the adjacent microlenses, the imaging object existing in the direction from the light receiving element to the microlens, and the micro The relationship between the air conversion length t0 of the distance between the apexes of the lens and the air conversion length t1 of the thickness between the apex of the microlens and the opening position of the opening on the light receiving element side is as follows:
1.36 · t1 / p ≦ d1 ≦ 2.4 · t1 / p + p · t1 / t0
An imaging device characterized by being: The relationship among the d1, the p, the t0, and the t1 is
1.6 · t1 / p ≦ d1 ≦ 1.9 · t1 / p + p · t1 / t0
The imaging device according to claim 1.   The imaging apparatus according to claim 1, wherein the opening is formed such that an opening area on the light receiving element side of the opening is equal to or smaller than an opening area on the microlens side.   The light shielding layer has at least a portion that forms a boundary with the opening made of a light absorbing member, and at least a portion excluding the opening on either the surface facing the light receiving element or the surface facing the microlens. The imaging device according to any one of claims 1 to 3, comprising a light absorbing member or a light reflecting member. The actual length d2 of the opening width of the opening on the microlens side, the air conversion length t2 of the thickness between the apex of the microlens and the opening position of the opening on the microlens side, and t0 , And the relationship between t1 and p is
d2 ≧ p (1−t2 / t1 + t2 / t0)
The imaging device according to any one of claims 1 to 4. The relationship between the t1, the t2, the d1, the d2, and the p is
t2 ≦ t1 · (1− (d1 + d2) / (2 · p + d1))
The imaging device according to any one of claims 1 to 5. The relationship between the air conversion length t3 of the thickness between the light receiving element and the opening position of the opening on the light receiving element side, and the t1 is:
t3 <t1 / 3
The imaging device according to any one of claims 1 to 6.   The imaging device according to claim 1, wherein the opening is filled with a material that is transparent to at least one wavelength in a wavelength range that can be received by the light receiving element.   The imaging apparatus according to claim 1, further comprising an optical filter that blocks visible light from being incident on the light receiving element. A light source that emits light in the direction of a biological part, an imaging unit that images the biological part irradiated with light from the light source, a storage unit that stores a plurality of biological information, and the biological part that the imaging unit images A biometric authentication apparatus comprising: a collation unit that collates biometric information obtained from the biometric information stored in the storage unit; and a control unit that performs biometric authentication according to a collation result of the collation unit ,
The imaging unit includes a light receiving unit in which a plurality of light receiving elements are arranged, a microlens arranged corresponding to each of the plurality of light receiving elements, and a light shielding layer provided between the light receiving unit and the microlens. An imaging unit that images the living body part having
The light shielding layer includes an opening provided corresponding to each of the plurality of light receiving elements,
The actual length d1 of the opening width of the opening on the light receiving element side, the actual length p of the distance between the adjacent microlenses, the living body part and the micro that exist in the direction from the light receiving element to the microlens The relationship between the air equivalent length t0 of the distance between the apex of the lens and the air equivalent length t1 of the thickness between the apex of the micro lens and the opening position of the opening on the light receiving element side is as follows:
1.36 · t1 / p ≦ d1 ≦ 2.4 · t1 / p + p · t1 / t0
A biometric authentication device characterized by the above. The relationship among the d1, the p, the t0, and the t1 is
1.6 · t1 / p ≦ d1 ≦ 1.9 · t1 / p + p · t1 / t0
The biometric authentication device according to claim 10.   The biometric authentication device according to claim 10 or 11, wherein the opening is formed such that an opening area on the light receiving element side of the opening is equal to or smaller than an opening area on the microlens side.   The light shielding layer includes a light absorbing member at least at a portion that borders the opening, and at least a portion of the surface that faces the light receiving element or the surface that faces the microphone lens, excluding the opening. The biometric authentication device according to any one of claims 10 to 12, comprising a light absorbing member or a light reflecting member. The actual length d2 of the opening width of the opening on the microlens side, the air conversion length t2 of the thickness between the apex of the microlens and the opening position of the opening on the microlens side, and t0 , And the relationship between t1 and p is
d2 ≧ p (1−t2 / t1 + t2 / t0)
The biometric authentication device according to any one of claims 10 to 13. The relationship between the t1, the t2, the d1, the d2, and the p is as follows:
t2 ≦ t1 · (1− (d1 + d2) / (2 · p + d1))
The biometric authentication device according to any one of claims 10 to 14. The relationship between the air conversion length t3 of the thickness between the light receiving element and the opening position of the opening on the light receiving element side, and the t1 is as follows.
t3 <t1 / 3
The biometric authentication device according to any one of claims 10 to 15.   The imaging device according to claim 10, wherein a material transparent to at least one wavelength between at least wavelengths of 680 nm and 1200 nm is filled inside the opening.   The imaging device according to claim 10, further comprising an optical filter that blocks visible light from being incident on the light receiving element.

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