JP5863094B2 - Image pickup device and image pickup apparatus using the same - Google Patents

Description

  The present invention relates to an imaging element that captures images of electromagnetic waves in a plurality of different frequency bands, and an imaging apparatus using the imaging element.

  Optical elements that can operate in a plurality of greatly different frequency bands are required in various areas. For example, by observing infrared light, the temperature of an object or a person can be detected, and by observing terahertz waves, natural radiation from the human body can be visualized to detect concealed objects, or a substance can be covered. It can be discriminated by contact. Therefore, if an imaging system that operates in the visible light and infrared light or visible light and terahertz wave regions is constructed, it can be used in fields such as security and chemical analysis. In addition, in-vehicle radar can detect a living thing and avoid a collision by combining millimeter waves of about 0.1 THz and thermography using infrared light.

  In general, in order to detect images of electromagnetic waves having greatly different frequency bands, such as visible light, infrared light, terahertz waves, and millimeter waves, imaging elements having different structures and sizes are required. For example, an antenna is used for microwaves and millimeter waves, a bolometer is used for terahertz waves, and a photodiode (PD) is used for light waves. Thus, such a wide-band imaging system corresponding to a plurality of greatly different frequency bands can be realized by using together an imaging system configured for each band. However, such a system requires a huge amount of processing for “association” between images (videos) detected in different bands in addition to a complicated and large configuration.

  For this reason, it is desirable that electromagnetic waves in a plurality of greatly different frequency bands can be imaged by one image sensor. In view of this, a technique has been proposed in which a visible light image and a far-infrared image are acquired almost simultaneously by a detector disposed on the same substrate (see, for example, Patent Document 1). In the imaging device described in Patent Document 1, a visible light detection unit and an infrared detection unit are alternately arranged two-dimensionally on a substrate, and the infrared detection unit detects visible light in order to increase a light receiving area. It is connected to an infrared absorption part that is transparent to visible light and is arranged so as to cover the upper part of the part. Thereby, the image of visible light and a far infrared ray can be imaged with one image sensor.

Japanese Unexamined Patent Application Publication No. 2008-204978

  However, in the imaging device described in Cited Document 1, since the infrared absorption unit is disposed in front of the visible light detection unit, visible light from an observation target that requires a higher resolution than infrared light passes through the infrared absorption unit. In this case, there is a problem that the detection efficiency is lowered and the resolution is deteriorated due to absorption or scattering.

  Further, since the infrared detection unit and the visible light detection unit are arranged with the same density and the same pattern, in order to increase the detection efficiency of the infrared detection unit, the area of the infrared absorption unit connected to the infrared detection unit is increased. Must. For this reason, the density of the infrared detection unit cannot be increased, and as a result, the density of the visible light detection unit, that is, the resolution by visible light must be sacrificed.

  Accordingly, an object of the present invention, which has been made paying attention to these points, is to use an image pickup device that picks up images of electromagnetic waves in a plurality of frequency bands that are greatly different from each other without reducing detection efficiency and resolution. It is to provide an image pickup apparatus.

The invention of an image pickup device that achieves the above object is an image pickup device comprising a plurality of types of pixel groups, wherein the plurality of types of pixel groups detect electromagnetic waves in mutually different frequency bands and have different pixel arrangement patterns. or have a pixel density, the plurality of types of pixel groups comprises a first group of pixels having a photodiode, and a second pixel group having a patch antenna,
At least a part of the patch antenna also serves as a light-shielding film of the first pixel group .

  Preferably, the center frequency of at least two electromagnetic waves among the electromagnetic waves in different frequency bands is different by 5 times or more.

  In addition, it is preferable that each pixel group of the plurality of types of pixel groups has a higher density of pixels constituting the pixel group as the frequency band of the detected electromagnetic wave is higher. Alternatively, it is preferable that each pixel group of the plurality of types of pixel groups has a larger detection surface area of the pixels constituting the pixel group as the frequency band of the electromagnetic wave to be detected is lower.

  Furthermore, the plurality of types of pixel groups may be three or more types of pixel groups that detect electromagnetic waves in three or more frequency bands different from each other.

  The plurality of types of pixel groups include a first pixel group and a second pixel group, and the first pixel group and the second pixel group include a first detection surface and a first detection surface stacked on each other. Each may be arranged on the second detection surface. Alternatively, the plurality of types of pixel groups include a first pixel group and a second pixel group, and the first pixel group and the second pixel group are respectively provided on a front surface and a back surface of the same substrate. You may arrange in the formed 1st detection surface and 2nd detection surface, respectively.

  Here, preferably, the first pixel group detects an electromagnetic wave in a first frequency band, and the second pixel group detects an electromagnetic wave in a second frequency band lower than the first frequency band. The electromagnetic wave in the second frequency band incident from the first detection surface passes through the first detection surface and is detected by the second pixel group.

The first group of pixels may be configured as a CCD.

An invention of an imaging device that achieves the above object is an imaging device comprising a plurality of types of pixel groups, wherein the plurality of types of pixel groups detect a plurality of electromagnetic waves in different frequency bands and are arranged An image sensor that is different in pattern or density, and an imaging optical system that forms an image of a subject by electromagnetic waves in different frequency bands on a detection surface of the image sensor; The imaging optical system is an electromagnetic wave element configured by a composite dielectric material in which a second dielectric material having a dielectric constant different from that of the first dielectric material is dispersed in a first dielectric material, The element has an effective dielectric constant substantially equal to an electromagnetic wave having a predetermined first wavelength and an electromagnetic wave having a predetermined second wavelength longer than the first wavelength, and an average of the second dielectric The particle size and average spacing are An electromagnetic wave element having a wavelength smaller than the first wavelength is provided, and the electromagnetic waves in the different frequency bands are electromagnetic waves in two frequency bands, and the inside of the electromagnetic wave element is at the first wavelength and the second wavelength, respectively. It is characterized by propagation .

  Preferably, the imaging optical system includes a branching unit that branches the electromagnetic waves in different frequency bands, a multiplexing unit that combines the electromagnetic waves in different frequency bands branched by the branching unit, and the branching And an imaging element that is provided between the combining unit and that combines the electromagnetic waves having different frequency bands with each other at the combining unit and then forms an image on the detection surface.

  Further, preferably, at least one of the first dielectric and the second dielectric has a resonance wavelength at which a dielectric constant changes greatly between the first wavelength and the second wavelength. Have.

  According to the present invention, a plurality of types of pixel groups that detect electromagnetic waves in different frequency bands have different pixel arrangement patterns or pixel densities, so that the detection efficiency is not reduced and the resolution is not deteriorated. Images with electromagnetic waves in different frequency bands can be taken.

1 is a perspective view of an image sensor according to a first embodiment of the present invention. It is a perspective view of the image sensor which concerns on 2nd Embodiment of this invention. It is a figure which shows the image pick-up element which concerns on 3rd Embodiment of this invention. It is a figure showing pixel arrangement of an image sensor concerning a 4th embodiment of the present invention. It is sectional drawing which shows schematic structure of the image pick-up element which concerns on 5th Embodiment of this invention. It is a figure which shows the optical system of the imaging device which concerns on 6th Embodiment of this invention. It is a schematic diagram which shows the structure of the composite dielectric material which comprises the imaging lens of FIG. 7 is a graph showing the effective dielectric constant of the imaging lens of FIG. 6 as a function of 2πa / λ ₁ . It is a figure which shows the optical system of the imaging device which concerns on 7th Embodiment of this invention. It is a figure which shows the optical system of the imaging device which concerns on 8th Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view of an image sensor according to the first embodiment of the present invention. The imaging device 10 includes a plurality of first pixels 11, second pixels 12, and third pixels 13 that detect electromagnetic waves having _three different frequencies f ₁ , f _2, and f ₃ , respectively. In the following, a pixel group composed of the plurality of first pixels 11, second pixels 12, and third pixels 13 will be referred to as a first pixel group, a second pixel group, and a third pixel, respectively. Call a group. The same applies to the following embodiments.

The three different frequencies f ₁ , f ₂ and f ₃ belong to frequency bands having greatly different wavelengths and satisfy the following relationship.
f ₁ > f ₂ > f ₃ (1)
At least two of these frequency bands differ greatly in frequency. The large difference includes, for example, the case where the center frequencies are different from each other by 5 times or more, such as visible light, infrared light, and millimeter wave. If the frequency is different by 5 times, a large chromatic aberration is generated by a general optical element.

The first pixel 11, the second pixel 12 and the third pixel 13 each have a detection unit provided corresponding to the frequencies f ₁ , f ₂ and f ₃ . For example, if f ₁ belongs to a visible light (about 400 THz to 750 THz), f ₂ belongs to a terahertz wave (about 0.3 to ₃ THz), and f ₃ belongs to a millimeter wave (about 30 GHz to 0.3 THz), the first The pixel 11 can be configured by disposing a wavelength filter in front of a photodiode (PD), the second pixel 12 using a bolometer, and the third pixel 13 using a patch antenna. of course. The combination of the frequencies f ₁ , f _2, and f ₃ is not limited to this, and can include frequency regions such as ultraviolet rays and infrared rays. In addition, as the detection units of the first pixel 11, the second pixel 12, and the third pixel 13 corresponding to this, various detection units such as a planar antenna, a semiconductor detector, and a temperature sensor can be used.

  The first pixel 11, the second pixel 12, and the third pixel 13 have substantially the same area, and the first pixel 11 is on the light receiving surface of the image sensor 10 in the vertical direction and the horizontal direction, respectively. They are regularly arranged so that one region of a checkered pattern is alternately formed with an interval of one pixel. On the other hand, for example, the third pixels 13 are arranged at the vertexes of the squares and the positions of the centers of gravity of the squares arranged with an interval of three pixels in the vertical and horizontal directions. The second pixel 12 is disposed at a position where the first pixel 11 and the third pixel 13 are not disposed. As described above, the pixel arrangement pattern is different for each pixel group formed by each pixel.

  In addition, each pixel group of the first pixel 11, the second pixel 12, and the third pixel 13 is arranged such that the higher the frequency of the electromagnetic wave to be detected, the higher the pixel density. Here, the pixel density represents the number of pixels per unit area. For example, in FIG. 1, out of a total of 100 pixels in the displayed area, the number of first pixels is 50, the number of second pixels is 38, and the number of third pixels is 12. That is, the pixel densities of the first pixel group, the second pixel group, and the third pixel group are different from each other.

When the present image sensor 10 is applied to the image pickup apparatus with the above-described configuration, the frequency f ₁ , the frequency f ₁ , and the frequency of the first pixel group, the second pixel group, and the third pixel group are respectively determined by one image sensor 10. 2-dimensional data of an electromagnetic wave f ₂ and _{f 3} can be obtained. That is, three images corresponding to the respective frequencies are obtained. In addition, since the first pixel 11, the second pixel 12, and the third pixel 13 are arranged on the same light receiving surface, the image data can be easily associated with each other. Accordingly, by performing image processing on the two-dimensional data of the electromagnetic waves having the frequencies f ₁ , f _2, and f ₃ output from the imaging device 10, for example, it is obtained by observing a terahertz wave on a visible light image. Images obtained by observing millimeter waves or the like can be displayed in a superimposed manner.

  As described above, according to the present embodiment, a plurality of types of pixel groups that detect electromagnetic waves in different frequency bands have different pixel arrangement patterns and pixel densities, thereby reducing detection efficiency and resolution. Thus, it is possible to capture an image of electromagnetic waves in a plurality of frequency bands that are greatly different from each other.

That is, in the present embodiment, a part of the detection unit of the second pixel 12 or the third pixel 13 having a longer wavelength covers the front surface of the first pixel 11 corresponding to the frequency f ₁ having a shorter wavelength. Therefore, the electromagnetic wave having the frequency f ₁ from the observation target for which high resolution is required is not absorbed or scattered when passing through the detection unit having the other frequencies f ₂ and f _3. There is no reduction in resolution or resolution degradation.

  Further, since the first pixel 11, the second pixel 12, and the third pixel 13 are arranged so that the higher the frequency to be detected, the higher the pixel density, the spatially fine information is detected as the frequency increases. can do. As a result, it is possible to obtain a higher definition image with higher frequency electromagnetic waves corresponding to the resolution characteristics of each frequency band. In particular, the first pixel group can obtain a high-resolution image in the visible light region where high definition is required.

(Second Embodiment)
FIG. 2 is a perspective view of an image sensor according to the second embodiment of the present invention. The imaging device 20 includes a plurality of first pixels 21, second pixels 22, and third pixels 23 that detect electromagnetic waves of _three different frequencies f ₁ , f _2, and f ₃ , respectively. The frequencies f ₁ , f _2, and f ₃ satisfy the relationship of the expression (1) as in the first embodiment.

  The pixel density of the first pixel 21, the second pixel 22, and the third pixel 23 is higher as the frequency of the electromagnetic wave to be detected is higher. Further, the first pixel 21, the second pixel 22, and the third pixel 23 are configured such that the area of the detection surface of the pixel is larger as the frequency band of the electromagnetic wave to be detected is lower. This is based on the fact that a detector smaller than the wavelength of the electromagnetic wave to be detected can detect the electromagnetic wave, but the detection efficiency at the time of detection decreases. In FIG. 2, the third pixels 23 are arranged so as to surround some of the first pixels 21.

According to the present embodiment, since pixels corresponding to lower frequencies are configured to be larger, detection efficiency or signal intensity that is more uniform with respect to electromagnetic waves of different frequencies f ₁ , f _2, and f _3. You can take an image. Further, by varying the pixel arrangement patterns and pixel density depending on the frequency, the first pixel 21 without mating overlap the second pixel 22, and the third pixel 23 from each other, the corresponding high frequency f ₁ while ensuring the pixel density of the first pixel 21, thereby increasing the detection sensitivity of the third pixel 23 corresponding to the lower frequency f _3. As a result, similarly to the first embodiment, the detection efficiency does not decrease and the resolution does not deteriorate.

In the first and second embodiments, the imaging element that detects _three different frequencies f ₁ , f _2, and f ₃ has been illustrated, but the detected frequencies are not limited to three, but two or four. An image sensor corresponding to the above frequency band can be configured.

(Third embodiment)
3A and 3B are views showing an image pickup device according to the third embodiment of the present invention. FIG. 3A is a perspective view of the image pickup device 30 and FIG. 3B shows only the laminated lower substrate 33. It is a perspective view shown. The image sensor 30 has two detection surfaces, a first detection surface 32 on the first substrate 31 and a second detection surface 34 on the second substrate 33. On the first detection surface 32 and the second detection surface 34, a plurality of first pixels 35 and a plurality of second pixels 36 that detect electromagnetic waves of two different frequencies f ₁ and f ₂ are arranged. .

Here, the frequencies f ₁ and f ₂ satisfy the following relationship.
f ₁ > f ₂ (2)
The electromagnetic wave having the frequency f ₁ is, for example, visible light, and the electromagnetic wave having the frequency f ₂ is infrared light or an electromagnetic wave having a frequency lower than that. Second pixel 36 corresponding to a lower frequency f ₂ is compared to the first pixel 35 corresponding to a higher frequency f _1, the area of the detection surface becomes larger.

The detection unit of the first pixel 35 is configured by a PD. In general, most of the semiconductor material constituting the PD is transparent to electromagnetic waves from the infrared to the low frequency side, and the first pixel 35 of the present embodiment also includes such a PD. Accordingly, when the first detection surface 32 is irradiated with electromagnetic waves having the frequencies f ₁ and f ₂ , the pixel group (first pixel group) by the first pixels 35 has the first frequency f ₁ . detecting an electromagnetic wave, a second wave of frequency f ₂ of the frequency f ₂ that has passed through the first detection surface 32, the pixel group by the second pixel 36 (second pixel group) is detected.

According to the present embodiment, the image sensor 30 is configured to be larger as the pixel corresponding to the lower frequency, so that the image pickup is performed with more uniform detection efficiency with respect to the electromagnetic waves having different frequencies f ₁ and f _2. can do. In addition, the detection unit of the first pixel 35 has a frequency while overlapping the first substrate 31 and the second substrate 33 each having the pixel group of the first pixel 35 and the pixel group of the second pixel 36. Since it is transparent to the electromagnetic wave of f _2, the electromagnetic wave of frequency f ₂ is not absorbed or scattered when passing through the detection unit of the first pixel 35, so that the detection efficiency is reduced and the resolution is reduced. No deterioration occurs.

In the present embodiment, the first pixel 35 and the second pixel 36 corresponding to the two types of frequencies f ₁ and f ₂ are provided. However, the image sensor detects only two frequency bands. Alternatively, electromagnetic waves having three or more frequencies may be detected. In that case, three or more substrates each having a pixel group corresponding to a different frequency are stacked. At this time, it is assumed that the electromagnetic wave corresponding to the pixel on the rear substrate stacked when viewed from the incident side of the electromagnetic wave passes through the detection unit of each pixel on the front substrate. Alternatively, the image sensor 10 or the image sensor 20 described in the first embodiment or the second embodiment may be used for the second substrate.

(Fourth embodiment)
4A and 4B are diagrams showing a pixel arrangement of an image sensor according to a fourth embodiment of the present invention, where FIG. 4A is a plan view and FIG. 4B is a cross-sectional view. The imaging element 40 has a first detection surface 41 and a second detection surface 42 on the front and back surfaces of the same substrate, respectively. The first detection surface 41 and the second detection surface 42 are provided with a plurality of first pixels 43 and a plurality of second pixels 44 that detect electromagnetic waves having two different frequencies f ₁ and f ₂ , respectively. One pixel group and a second pixel group are formed. Similarly to the third embodiment, the frequency f ₁ and the frequency f ₂ satisfy the relationship of the expression (2), and the electromagnetic wave of the frequency f ₁ is, for example, visible light. In this case, the detection unit of the first pixel 43 is configured by a PD, for example. Further, the second pixel 44 corresponding to a lower frequency f ₂ is compared to the first pixel 43 corresponding to a higher frequency f _1, the area of the detection surface becomes larger.

With the configuration as described above, when the imaging element 40 is applied to an imaging device, when electromagnetic waves having frequencies f ₁ and f ₂ are incident on the first detection surface 41, the first pixel 43 performs the first operation. The pixel group detects the electromagnetic wave in the first frequency band f ₁ , and transmits the electromagnetic wave in the _second frequency band f ₂ having the frequency f ₂ transmitted through the first detection surface 43 to the second pixel 44. A pixel group detects. Thereby, two image signals corresponding to the frequencies f ₁ and f ₂ are obtained.

According to the present embodiment, as in the third embodiment, the image sensor 40 can capture images with more uniform detection efficiency or signal intensity with respect to electromagnetic waves having different frequencies f ₁ and f ₂ . Further, since the detection portion of the first pixel group is transparent to electromagnetic waves of a frequency f _2, or is absorbed when an electromagnetic wave of frequency f ₂ is transmitted through the detection portion of the first pixel 43, or be scattered Therefore, the detection efficiency is not lowered and the resolution is not deteriorated.

  In the present embodiment, the image sensor has two pixel groups arranged on the two detection surfaces 41 and 42 formed on the front surface and the back surface. It is also possible to arrange two or more types of pixel groups. Alternatively, a substrate having a third detection surface for further detecting an electromagnetic wave transmitted through the second detection surface on the back surface may be disposed so as to be in contact with or close to the back surface. In this case, the third detection surface may be configured to have the pixel arrangement of the image sensor 10 or the image sensor 20 shown in the first embodiment or the second embodiment.

(Fifth embodiment)
It is sectional drawing which shows schematic structure of the image pick-up element which concerns on 5th Embodiment of this invention. The imaging device 50 is configured by integrating _two electromagnetic wave detection mechanisms having different frequencies f ₁ and f ₂ . The frequency f ₁ is in the visible light or infrared light region, and the frequency f ₂ is lower than f ₁ and belongs to, for example, the millimeter wave band.

The imaging device 50 has a configuration based on a general CCD, and a plurality of photodiodes (PD) 52 are two-dimensionally arranged on a semiconductor substrate 51. The image sensor 50 includes a microlens array 53, a buried channel 54, and a transfer electrode 55. Light of frequency f ₁ (indicated by an arrow in FIG. 5) is converged by the microlens array 53, irradiated to the PD 52, and converted into signal charges. This electric charge is transferred to an output unit (not shown) by the buried channel 54 and the transfer electrode 55. Further, unnecessary noise is generated when the photoelectric effect is generated except for the PD 52, and thus a metal (aluminum) light shielding film 56 is formed on the transfer electrode 55.

Furthermore, in addition to the general CCD configuration as described above, the imaging device 50 is configured to provide a metal ground plate 57 on the back surface of the substrate 51 to be grounded, and to connect a wiring (not shown) to the light shielding film 56. The ground plate 57 and the light shielding film 56 constitute a patch antenna array. This patch antenna, detecting the electromagnetic wave of the frequency f _2.

  The light-shielding film 56 is divided into a plurality of regions so as to cover other than the opening above the PD 52, whereby the shape and arrangement of the patch antenna can be appropriately set. When the imaging device 50 is viewed from the upper surface side, the positional relationship between the PD 52 and the patch antenna may be alternately arranged like a checkered pattern, and the first pixel 21 and the third pixel 23 in FIG. As described above, the patch antenna may be arranged so as to surround the photodiode.

With the configuration described above, the electromagnetic wave having the frequency f ₁ is detected by the PD 52 among the electromagnetic waves having the frequencies f ₁ and f ₂ imaged on the image sensor 50. On the other hand, the electromagnetic wave having the frequency f ₂ is detected by a patch antenna including the light shielding film 56 and the ground plate 57.

Therefore, according to the present embodiment, a patch antenna function is added by adding a simple configuration such as a wiring and a ground plate while using a general CCD configuration as a base, and electromagnetic waves having different frequencies f ₁ and f ₂ . Can be detected. In addition, the density and arrangement of the patch antennas can be designed in various ways, so that the electromagnetic waves having the frequencies f ₁ and f ₂ can be detected well without causing a decrease in the detection light rate or deterioration in resolution. Can do.

The imaging device of the first to fifth embodiment, it is assumed that each detects an electromagnetic wave of frequency _f 1, _{f 2,} or _f 1, _{f 2} and _{f 3,} these frequencies _f 1, _{f 2} and f ₃ is not strictly limited to electromagnetic waves of these frequencies, but may be electromagnetic waves having a certain bandwidth with these frequencies f ₁ , f ₂ and f ₃ as the center frequencies. The bandwidth can be various bandwidths depending on the detection unit of each pixel group of the image sensor.

(Sixth embodiment)
FIG. 6 is a diagram showing an optical system of an imaging apparatus according to the sixth embodiment of the present invention. In the present application, the term “optical system” is used for a path for guiding an electromagnetic wave from an object to an image sensor even for an electromagnetic wave that is not generally classified into a light region. The imaging system 60 includes an imaging element 61 and an imaging lens 62 (electromagnetic wave element). The image sensor 61 is an image sensor that detects electromagnetic waves having _two different frequencies f ₁ and f _2. For example, the image sensors 30, 40 and 50 of the third to fifth embodiments can be used. The imaging lens 62 is an element having the same refractive index with respect to the electromagnetic waves having the frequency f ₁ and the frequency f ₂ , and forms an image 64 of the object 63 on the imaging element 61. The electromagnetic wave emitted from one point of the object is collected again at one point on the image sensor by the imaging lens to form an image.

This imaging system is configured to operate at _two frequencies f ₁ and f ₂ , and among the light rays in the figure, the solid line corresponds to the electromagnetic wave of f ₁ and the broken line corresponds to the electromagnetic wave of f ₂ . Images 64 of electromagnetic waves having respective frequencies are converted into electrical signals by the image sensor 61, and image information is formed by an image processing system (not shown). Normally, when the frequencies are greatly different, chromatic aberration due to the difference in refractive index of the imaging system in each band occurs. According to the present embodiment, since the imaging lens 62 having the same refractive index is used for the electromagnetic waves having the frequency f ₁ and the frequency f ₂ , there is no influence of chromatic aberration. Such an imaging lens 62 can be configured by using a composite dielectric described below with reference to FIGS. In the following description, the wavelength of electromagnetic waves in vacuum will be described, but the wavelength λ ₁ of the electromagnetic waves corresponds to the frequency f ₁ and the wavelength λ ₂ corresponds to the frequency f ₂ .

FIG. 7 is a schematic diagram showing a configuration of a composite dielectric that constitutes the imaging lens of FIG. In the composite dielectric 65, a second dielectric 67 having a dielectric constant different from that of the first dielectric 66 is dispersed in the first dielectric 66. Here, the dielectric constant of the first dielectric 66 is ε ₁ , and the dielectric constant of the second dielectric 67 is ε ₂ . For simplicity, the second dielectrics 67 are all spheres having a radius a and are not shown in the figure, but are arranged three-dimensionally to form a square lattice with period p (> a). Assume that In this case, the volume occupation ratio of the second dielectric 67 occupying the whole is given by equation (3).

Hereinafter, this f is simply referred to as volume occupancy. Such a composite dielectric 65 is used for electromagnetic waves having two different wavelengths, and the wavelengths of the respective electromagnetic waves to be used in the vacuum are λ ₁ and λ ₂ . It is assumed that the relationship (4) holds between the period p of the grating on which the second dielectric 67 is arranged and the wavelengths λ ₁ and λ _{2 of} the first and second electromagnetic waves.

In this case, an effective dielectric constant can be defined for the composite dielectric 65. This is called the effective dielectric constant and expressed by ε _eff . The effective dielectric constant ε _eff is known to be expressed by the equation (5) (see CL Holloway et al., IEEE Transactions on Antenna and Propagation, Vol. 51, p.2596-2603 (2003)).

  Here, F (θ) is defined by equation (6).

FIG. 8 is a graph showing the effective dielectric constant expressed by the equation (5) when λ ₁ as the first wavelength is 500 nm, with 2πa / λ ₁ as the horizontal axis. Here, SiO ₂ (ε ₁ (λ ₁ ) = 2.14) is used as the first dielectric 66, and ZnS (ε ₂ (λ ₁ ) = 5.86) is used as the second dielectric 67, respectively. The volume occupation ratio was set to f = 0.268. The dielectric constants ε ₁ (λ ₁ ) and ε ₂ (λ ₁ ) of the first dielectric 66 and the second dielectric 67 are values for the wavelength λ ₁ = 500 nm. The effective dielectric constant at the left end (2πa / λ ₁ = 0) of this graph is ε ⁰ _eff (λ ₁ ) = 2.84. As 2πa / λ ₁ increases from the left end of the graph, the effective dielectric constant increases and rapidly increases and diverges in the vicinity of 2πa / λ ₁ = 1.39. This is because a dielectric sphere having a dielectric constant ε ₂ constituted by the second dielectric 67 acts as a resonator. In this region, the structural period of the composite dielectric 65 is adjusted. Any effective dielectric constant greater than or equal to 2.84 can be realized.

On the other hand, when the second wavelength λ ₂ is 100 μm, the dielectric constants of the first dielectric 66 and the second dielectric 67 are ε ₁ (λ ₂ ) = 3.88 and ε ₂ (λ ₂ , respectively). ) = 9.36. Also in this case, the graph of the effective dielectric constant with respect to the second wavelength λ ₂ is a curve that diverges at a predetermined 2πa / λ _{2 as} in FIG. Here, considering that λ ₂ is approximately 200 times λ ₁ , the value of the radius a ₂ of the second dielectric 67 where the effective dielectric constant diverges with respect to the electromagnetic wave having the second wavelength λ _2. Is considerably larger (about two digits) than the value of the radius a ₁ at which the effective permittivity diverges with respect to the electromagnetic wave having the first wavelength λ ₁ . Therefore, in the range of a satisfying 0 <2πa / λ ₁ <1.39, no divergence occurs with respect to the second wavelength λ ₂ , and the effective dielectric constant is substantially constant at ε _eff (λ ₂ ) = 4.97. Value.

Therefore, by setting the radius a to an appropriate value, it is possible to make the effective dielectric constant ε _eff of the electromagnetic wave having the first wavelength λ ₁ substantially coincide with the effective dielectric constant ε _eff of the second electromagnetic wave. Specifically, in FIG. 2, when 2πa / λ ₁ = 1.18, the effective dielectric constant for the first electromagnetic wave is ε _eff = 4.98, so that the wavelength λ ₁ is equal to 500 nm. _{Even for 2} = 100 μm, an effective dielectric constant having substantially the same value can be obtained. Since the dielectric does not exhibit a magnetic response, the effective refractive index (effective refractive index) of the composite dielectric is equal to the square root of the effective dielectric constant. Therefore, in the above example, the composite dielectric exhibits an effective refractive index having substantially the same value for both wavelengths λ ₁ and λ ₂ .

In the above description, the radius a of the sphere constituting the second dielectric 67 is adjusted in the vicinity of 2πa / λ ₁ = 1.39, and the effective dielectric constant ε _eff for the electromagnetic wave having the first wavelength λ ₁ is adjusted. _{Is set} to the same value as the effective dielectric constant ε _eff of the second wavelength λ ₂ . On the other hand, the effective dielectric constant ε _eff can also be changed by adjusting the first wavelength λ ₁ in the vicinity of 2πa / λ ₁ = 1.39.

Therefore, by using the imaging lens 62 composed of the above-described composite dielectric 65, the same refractive index can be obtained for the _two frequencies f ₁ and f ₂ electromagnetic waves with a simple configuration without considering correction of chromatic aberration. An optical system can be configured. In addition, although a simple optical system including one imaging lens 62 is illustrated in FIG. 6, the optical system may be configured using a plurality of elements including the composite dielectric 65.

The imaging apparatus 60 according to the present embodiment is substantially the same as the imaging element 61 having two pixel groups that detect electromagnetic waves of _two frequencies f ₁ and f ₂ that are greatly different from each other, and the electromagnetic waves of the frequencies f ₁ and f _2. Since it is constituted by an imaging optical system having an imaging lens 62 (electromagnetic wave element) constituted by a composite dielectric having an equal refractive index, an image by electromagnetic waves in two greatly different frequency bands can be obtained as a single imaging device. 60 can be taken. In particular, by using the composite dielectric 65, the optical system can be simplified, and the apparatus can be made small and light. As a result, for example, an image based on a combination of visible light, infrared light, visible light, and millimeter wave can be simultaneously captured using the same imaging element 61, and the captured images can be easily associated with each other. is there.

(Seventh embodiment)
FIG. 9 is a diagram showing an optical system of an imaging apparatus according to the seventh embodiment of the present invention. When the frequencies f ₁ and f ₂ are greatly different, chromatic aberration caused by the difference in refractive index of the imaging lens (system) in each band cannot be sufficiently corrected by a normal aberration correction (lens design) technique. In view of this, the imaging device 70 is configured such that an imaging lens (system) is individually provided for each frequency and is operated at _two frequencies f ₁ and f ₂ , respectively. Of the light rays in the figure, the solid line corresponds to the electromagnetic wave f ₁ and the broken line corresponds to the electromagnetic wave f ₂ . The configuration of the optical system of the imaging device 70 will be described below. Note that only the electromagnetic waves having the frequencies f ₁ and f ₂ are to be imaged, but the electromagnetic waves emitted from the object may include other frequency components.

  The imaging device 70 includes an imaging element 71, a first dichroic mirror 72, a second dichroic mirror 73, a first filter 74, a first mirror 75, a first imaging lens 76, a second filter 77, An imaging optical system including a second mirror 78 and a second imaging lens 79.

The first dichroic mirror 72 is an element that branches an electromagnetic wave including the frequency f ₁ and an electromagnetic wave including the frequency f ₂ and constitutes a branching portion. One electromagnetic wave emitted from the object 80 travels straight, and the other electromagnetic wave is reflected and separated by the first dichroic mirror 72. FIG. 9 shows an example in which the electromagnetic wave having the frequency f ₁ travels straight and the electromagnetic wave having the frequency f ₂ is reflected, which will be described below.

The electromagnetic wave that has passed through the first dichroic mirror 72 has its components other than the frequency f ₁ removed by the first filter 74 and reflected by the first mirror 75, and then the first imaging lens 76 (imaging element). As a result, an image is formed on the image sensor 71. Here, a second dichroic mirror 73 serving as a multiplexing unit is provided between the first imaging lens 76 and the image sensor 71, and an electromagnetic wave having a frequency f ₁ is directed toward the detection surface of the image sensor 71. Reflect.

Further, the electromagnetic wave reflected by the first dichroic mirror 72 is subjected to removal of components other than the frequency f ₂ by the second filter 77 and reflected by the second mirror 78, and then the second imaging lens 79 (concatenation). The image is formed on the image sensor 71 by the image element). The second dichroic mirror 73 described above is disposed between the second imaging lens 79 and the image sensor 71, and transmits the electromagnetic wave having the frequency f ₂ toward the detection surface of the image sensor 71.

Therefore, the second dichroic mirror 73 combines the electromagnetic wave having the frequency f _{1 and} the electromagnetic wave having the frequency f ₂ so as to form an image 81 on the detection surface of the same image sensor 71.

As the imaging device 71, for example, each imaging device 30, 40 or 50 of the third to fifth embodiments can be used. Images by electromagnetic waves of the respective frequencies f ₁ and f ₂ are converted into electrical signals by the image sensor 71, and image information is created by an image processing system.

According to the present embodiment, electromagnetic waves in _two frequency bands f ₁ and f ₂ that are significantly different from each other are separated and imaged on the image sensor 71 using different imaging lenses 76 and 79, respectively. An image 81 using electromagnetic waves in two different frequency bands can be picked up by a single image pickup device 70. Further, since the electromagnetic wave to be imaged by each imaging lens is limited to a single frequency, the design of the imaging lens can be optimized for that frequency, and any of f ₁ and f ₂ can be optimized. Good imaging performance can be easily obtained with respect to frequency.

(Eighth embodiment)
FIG. 10 is a diagram showing an optical system of an imaging apparatus according to the eighth embodiment of the present invention. The imaging device 90 according to the present embodiment is an imaging device that performs imaging using electromagnetic waves having _three frequencies f ₁ , f _2, and f ₃ .

The imaging device 90, each of the frequencies _f 1, _{f 2,} and individually provided an imaging lens (system) relative to _{f 3,} and configured to operate in three frequencies _f 1, _{f 2} and _{f 3} ing. Among the light rays in the figure, the alternate long and short dash line corresponds to the electromagnetic wave having the frequency f ₁ , the solid line corresponds to the frequency f ₂ and the broken line corresponds to the electromagnetic wave having the frequency f ₃ . The configuration of the optical system of the imaging device 90 will be described below.

The imaging device 90 includes an imaging element 91, a first dichroic mirror 92, a second dichroic mirror 93, a third dichroic mirror 94, a fourth dichroic mirror 95, and an optical element disposed therebetween. And an image optical system. The first dichroic mirror 92 branches the electromagnetic wave having the frequency f _{1 and} the electromagnetic waves having the frequency f ₂ and the frequency f ₃ among the electromagnetic waves emitted from the object 104. The second dichroic mirror 93 diverts the electromagnetic wave of the electromagnetic wave and the frequency f ₃ of the frequency f _2. The third dichroic mirror 94 combines the electromagnetic wave with the frequency f _{1 and} the electromagnetic wave with the frequency f ₂ . Further, the fourth dichroic mirror 95 combines the electromagnetic waves having the frequencies f ₁ and f _{2 and} the electromagnetic wave having the frequency f ₃ . Therefore, the first dichroic mirror 92 and the second dichroic mirror 93 correspond to a branching portion, and the third dichroic mirror 94 and the fourth dichroic mirror 95 correspond to a multiplexing portion.

In addition, a first filter 96, a first mirror 97, and a first imaging lens 98 are disposed between the first dichroic mirror 92 and the third dichroic mirror 94. The electromagnetic wave emitted from the object 104 and transmitted through the first dichroic mirror 92 is subjected to the first imaging lens after components other than the frequency f ₁ are removed by the first filter 96 and reflected by the first mirror 97. An image 105 is formed on the detection surface of the image sensor 91 by 98 (imaging element).

Further, a second filter 99 and a second imaging lens 100 are disposed between the second dichroic mirror 93 and the third dichroic mirror 94. The electromagnetic wave emitted from the object 104 and reflected by the second dichroic mirror 93 is imaged by the second imaging lens 100 (imaging element) after components other than the frequency f ₂ are removed by the second filter 99. An image 105 is formed on the detection surface of the element 91.

Further, a third filter 101, a third imaging lens 102, and a second mirror 103 are disposed between the second dichroic mirror 93 and the fourth dichroic mirror 95. The electromagnetic wave emitted from the object 104 and transmitted through the third dichroic mirror 93 has components other than the frequency f ₃ removed by the third filter 101, and a third image formed in front of the second mirror 103. An image 105 is formed on the detection surface of the image sensor 91 by the lens 102 (imaging element).

As the image sensor 91, for example, the image sensor 10 or 20 according to the first or second embodiment of the present application can be used. Images by electromagnetic waves of the respective frequencies f ₁ , f _2, and f ₃ are converted into electric signals by the image sensor 91, and image information is created by an image processing system.

According to the present embodiment, electromagnetic waves in _three frequency bands f ₁ , f ₂ and f _{3 which} are greatly different from each other are separated and imaged on the image sensor 91 using different imaging lenses 98, 100 and 102. Therefore, an image using electromagnetic waves in three greatly different frequency bands can be captured by the single imaging device 90. Further, since the electromagnetic wave to be imaged by each imaging lens is limited to a single frequency, the design of the imaging lens can be optimized for that frequency, and f ₁ , f ₂ and f ₃ can be optimized. Good imaging performance can be easily obtained for any of these frequencies.

  The image pickup device and the image pickup apparatus of the present invention are further effective when the influence of chromatic aberration becomes very large, for example, when the frequency differs by 100 times or more.

In the sixth to eighth embodiments, the example of the imaging system using the two frequencies f ₁ and f ₂ or the three frequencies f ₁ , f _2, and f ₃ has been described. It is not limited to two or three frequencies. If it contains a broadband frequency component in the electromagnetic waves emanating from the object, for example, an electromagnetic wave having a certain band around the frequency f ₁ can be equally good imaging and an electromagnetic wave of frequency f ₁ is. The same applies to the frequency f ₂ and f ₃ electromagnetic waves. The band in which good imaging can be obtained is mainly determined by the degree of chromatic aberration of the imaging lens. When the chromatic aberration of the imaging lens is small or well corrected at the frequency f ₁ , a good imaging can be obtained using an electromagnetic wave in a wider band centered on f ₁ . In order to adjust the band of the electromagnetic wave that contributes to imaging in consideration of the purpose of imaging and the chromatic aberration of the imaging lens, a dichroic mirror or filter having a desired frequency characteristic may be used.

  Further, the sixth embodiment may include a configuration in which the optical path is branched for each different frequency as in the seventh and eighth embodiments. In that case, it is preferable to adjust so that the difference between the optical path lengths of the respective frequency bands before entering the imaging lens made of the composite dielectric becomes substantially zero. Further, in the sixth to eighth embodiments, as in the third and fourth embodiments, the positions in the optical axis direction of the detection surface for each frequency as shown in the third and fourth embodiments are different. If the difference is not negligible, it is preferable to provide an optical path difference in consideration of the difference.

  In addition, this invention is not limited only to the said embodiment, Many deformation | transformation or a change is possible. For example, the plurality of types of pixel groups of the image sensor may be four or more types of pixel groups. Further, the frequency regions detected by all the pixel groups need not all be greatly different from each other. For example, there are four types of pixel groups, three of which correspond to R, G, and B visible light, and the other one type of pixel detects millimeter waves and terahertz waves. good.

  In addition, the imaging optical system of the imaging device according to the seventh and eighth embodiments corresponds to two or three different frequency bands, but by branching to more frequency bands at the branching unit, An imaging optical system corresponding to four or more frequency bands can also be constructed.

10, 20, 30, 40, 50 Image sensor 11, 21, 35, 43 First pixel 12, 22, 36, 44 Second pixel 13, 23 Third pixel 31 First substrate 32, 41 First Surface 33 second substrate 34, 42 second surface 35 first substrate 36 second substrate 51 substrate 52 photodiode 53 microlens array 54 buried channel 55 transfer electrode 56 light shielding film 57 ground plate 60, 70 imaging device 61, 71, 91 Image sensor 62 Imaging lens 63, 80, 104 Object 64, 81, 105 Image 65 Composite dielectric 66 First dielectric 67 Second dielectric 72, 92 First dichroic mirror 73, 93 Second Dichroic mirrors 74, 96 First filter 75, 97 First mirror 76, 98 First imaging lens 77, 99 Second fill 78, 103 Second mirror 79, 100 Second imaging lens 94 Third dichroic mirror 95 Fourth dichroic mirror 101 Third filter 102 Third imaging lens

Claims (12)

An image sensor comprising a plurality of types of pixel groups,
The plurality of types of pixel groups, respectively detect the electromagnetic waves of different frequency bands from each other, and, have a different pixel arrangement pattern or pixel density to each other,
The plurality of types of pixel groups include a first pixel group having a photodiode and a second pixel group having a patch antenna,
At least a part of the patch antenna also serves as a light-shielding film of the first pixel group .   The imaging device according to claim 1, wherein center frequencies of at least two electromagnetic waves among the electromagnetic waves in different frequency bands are different by 5 times or more.   2. The image pickup device according to claim 1, wherein each pixel group of the plurality of types of pixel groups has a higher density of pixels constituting the pixel group as the frequency band of the electromagnetic wave to be detected is higher.   2. The imaging according to claim 1, wherein each pixel group of the plurality of types of pixel groups has a larger area of a detection surface of a pixel constituting the pixel group as the frequency band of the electromagnetic wave to be detected is lower. element.   The image pickup device according to claim 1, wherein the plurality of types of pixel groups are three or more types of pixel groups that detect electromagnetic waves in three or more frequency bands different from each other.   The plurality of types of pixel groups include a first pixel group and a second pixel group, and the first pixel group and the second pixel group include a first detection surface and a second pixel layer stacked on each other. The image pickup device according to claim 1, wherein the image pickup device is arranged on each of the detection surfaces.   The plurality of types of pixel groups include a first pixel group and a second pixel group, and the first pixel group and the second pixel group are respectively formed on a front surface and a back surface of the same substrate. The imaging device according to claim 1, wherein the imaging element is arranged on each of the first detection surface and the second detection surface.   The first pixel group detects an electromagnetic wave in a first frequency band, the second pixel group detects an electromagnetic wave in a second frequency band lower than the first frequency band, and the first pixel group The imaging according to claim 6 or 7, wherein the electromagnetic wave in the second frequency band incident from the detection surface is transmitted through the first detection surface and detected by the second pixel group. element. The imaging device according to claim 1, wherein the first pixel group is configured as a CCD. An image pickup device including a plurality of types of pixel groups, wherein the plurality of types of pixel groups detect a plurality of electromagnetic waves having different frequency bands, and are different from each other in an arrangement pattern or density. An image sensor
An imaging optical system that forms an image of a subject by electromagnetic waves in different frequency bands from each other on a detection surface of the imaging device ;
The imaging optical system is an electromagnetic wave element composed of a composite dielectric material in which a second dielectric material having a dielectric constant different from that of the first dielectric material is dispersed in a first dielectric material,
The electromagnetic wave element has an effective dielectric constant substantially equal to an electromagnetic wave having a predetermined first wavelength and an electromagnetic wave having a predetermined second wavelength longer than the first wavelength, and is an average of the second dielectric The average particle size and the average interval include an electromagnetic wave element smaller than the first wavelength,
2. The imaging apparatus according to claim 1, wherein the electromagnetic waves in different frequency bands are electromagnetic waves in two frequency bands, and propagate in the electromagnetic wave element at the first wavelength and the second wavelength, respectively. The imaging optical system includes a branching unit that branches the electromagnetic waves of different frequency bands, a multiplexing unit that combines the electromagnetic waves of different frequency bands branched by the branching unit, the branching unit, and the branching unit An imaging element that is provided between a multiplexing unit and forms the image on the detection surface after the electromagnetic waves in the different frequency bands are combined by the multiplexing unit, respectively. The imaging device according to 10 . At least one of the first dielectric and the second dielectric has a resonance wavelength in which a dielectric constant changes greatly between the first wavelength and the second wavelength. The imaging device according to claim 10 .

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