JP4952329B2 - Imaging apparatus, chromatic aberration correction method, and program - Google Patents

Description

  The present invention relates to an imaging apparatus such as a digital camera, and more particularly to an imaging apparatus that corrects chromatic aberration by image processing, a chromatic aberration correction method, and a program.

  Usually, a lens used in an imaging apparatus such as a digital camera has chromatic aberration, which greatly affects the quality of a captured image. Chromatic aberration is a color shift that occurs when passing through a lens.

  That is, since the refractive index of the lens differs depending on the color of light, when white light is passed through the lens, the focal point is tied to one point, blue with a high refractive index is focused on the lens side, and red with a low refractive index is Focus far from the lens. This is a phenomenon that occurs because the refractive index and the dispersion rate differ depending on the wavelength of light, and the aberration caused by the difference in wavelength is called chromatic aberration.

  Conventionally, a method for correcting such chromatic aberration by image processing is known. For example, Patent Document 1 discloses that an image obtained through an image sensor such as a CCD (charge coupled device) is decomposed into RGB color images, and then a B (blue) image is obtained with reference to a G (green) image. It is disclosed that the chromatic aberration is corrected by enlarging and reducing the R (red) image and combining them.

  The reason for enlarging the B (blue) image is that the color of B has a higher refractive index than G and the image becomes smaller. The reason for reducing the R (red) image is that the color of R has a low refractive index and the image becomes large.

In Patent Document 2, incident light is split into three colors of RGB by a beam splitter (spectral member), and these lights are received by three image sensors to generate images of each color, thereby correcting chromatic aberration. Is disclosed.
JP 2004-336106 A JP 2006-166336 A

  However, in the method of creating color R, G, and B images by providing a color filter on the image sensor as in Patent Document 1, the resolution of each color image decreases, which affects the correction of chromatic aberration. As a result, there is a problem such as deterioration of image quality. On the other hand, the configuration using a large number of image sensors corresponding to the spectral colors as in Patent Document 2 has problems such as high cost and a large mounting area.

  The present invention has been made in view of the above points, and an imaging apparatus and a chromatic aberration correction method capable of appropriately correcting chromatic aberration caused by a photographing lens and obtaining a high-quality photographed image while maintaining high resolution. And to provide a program.

The present invention corresponds to an imaging device that converts light incident through a photographing lens into an electrical signal, a spectral filter that is disposed in front of the photographing lens and has a narrow-band transmission characteristic, and a focal length of the photographing lens. The table means for storing the chromatic aberration characteristic data for each wavelength region, the filter driving means for sequentially switching the transmission characteristics of the spectral filter by continuous photographing, and the switching operation of the spectral filter by the filter driving means An imaging control unit that acquires a spectral image for each of a plurality of wavelength regions from the imaging device in a time-sharing manner, reads out characteristic data of chromatic aberration in each wavelength region corresponding to the focal length at the time of imaging from the table unit, and Te, subjected to correction processing of chromatic aberration in accordance with the wavelength region in each of a plurality of spectral images sequentially obtained by the photographing control means A correction process unit, characterized by comprising a composition processing unit that generates one shot image by combining the respective spectral image corrected processed by the correcting means.

The present invention also provides an imaging device that converts light incident through the photographing lens into an electrical signal, a spectral filter that is disposed in front of the photographing lens and has a narrow- band transmission characteristic, and a focal length of the photographing lens. In the chromatic aberration correction method of the imaging apparatus , comprising: a table storing chromatic aberration characteristic data corresponding to each wavelength region; a first step of sequentially switching transmission characteristics of the spectral filter by continuous shooting; A second step of acquiring, in a time-division manner, spectral images for each of a plurality of wavelength regions from the imaging device in conjunction with the switching operation of the spectral filter in the step of step, and each wavelength corresponding to the focal length at the time of photographing from the table read characteristic data of the chromatic aberration of the region, based on the characteristic data, the wavelength in each of a plurality of spectral images obtained sequentially in the second step A third step of performing correction processing of chromatic aberration in accordance with the area, and a fourth step of generating one captured image by combining the spectral images corrected by the third step. And

The present invention also provides an imaging device that converts light incident through the photographing lens into an electrical signal, a spectral filter that is disposed in front of the photographing lens and has a narrow- band transmission characteristic, and a focal length of the photographing lens. to a table storing characteristic data of chromatic aberration corresponding to each wavelength region, the computer controlling the imaging apparatus having a first of the continuous shooting sequentially switching the transmission characteristics of the spectral filter function, the first A second function for acquiring spectral images for each of a plurality of wavelength regions from the image sensor in a time-division manner in conjunction with the switching operation of the spectral filter by the function , and for each wavelength region corresponding to the focal length at the time of photographing from the table It reads the chromatic aberration characteristic data, on the basis of the characteristic data, chromatic aberration in accordance with the wavelength region in each of the sequential plurality of spectral images obtained at the second function The third function of performing a correction process, characterized in that to realize the fourth function of generating a one shot image by combining the respective spectral image corrected processed by the third function.

  According to the present invention, it is possible to obtain a high-quality captured image by appropriately correcting chromatic aberration while maintaining high resolution, using a spectral image of each wavelength band obtained by switching spectral filters by continuous imaging. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration when a digital camera capable of high-speed photography is taken as an example of an imaging apparatus according to an embodiment of the present invention.

  The digital camera 11 includes an image sensor 12, a DSP (digital signal processor) unit 13, a photographing lens 14, and a spectral filter 15. The image pickup device 12 is composed of an image sensor such as a complementary metal oxide semiconductor (CMOS) capable of continuous shooting at a high resolution of 6 million pixels or more and at a high speed of 60 or more images per second. Note that a physical color generating member such as a general Bayer array RGB color filter is not provided on the surface of the imaging element 12.

  The DSP unit 13 receives and processes image signals continuously output from the image sensor 12 at high speed. The photographing lens 14 includes a focus lens, a zoom lens, and the like, and is provided in front of the image sensor 12 so as to be movable in the optical axis direction. Actually, for example, a blur correction mechanism, a diaphragm mechanism, a shutter mechanism, and the like are provided between the imaging element 12 and the photographing lens 14, but the illustration is omitted because they are not directly related to the present invention.

  The spectral filter 15 is disposed in front of the photographing lens 14 and has a narrow band transmission characteristic. As the spectral filter 15, a liquid crystal tuning filter called LCTF (Liquid Crystal Tunable Filter) or a liquid crystal Fabry-Perot etalon filter called LCFP (Liquid Crystal Fabry-Perot etalo) is used. These filter configurations will be described in detail later.

  The digital camera 11 is provided with a control unit 16. The control unit 16 controls the entire camera and is mainly composed of a CPU. In the present embodiment, the DSP unit 13 and the control unit 16 are separated and image processing is performed at high speed on the DSP unit 13 side. However, as a matter of course, all processing is performed on the control unit 16 side. It may be a configuration.

  As shown in FIG. 1, a lens driving unit 17 and a filter driving unit 18 are connected to the control unit 16. The lens driving unit 17 moves the photographing lens 14 in the optical axis direction according to the lens driving signal output from the control unit 16. The photographing lens 14 includes a zoom lens, and when a zoom operation is instructed, the zoom lens moves back and forth along the optical axis. The filter driving unit 18 drives the spectral filter 15 in accordance with the filter driving signal output from the control unit 16, and sequentially switches the transmission characteristics of the spectral filter 15 to take in light of each wavelength band.

  In addition, the digital camera 11 includes a strobe 19 and a strobe drive circuit 20, an LED 21 and an LED drive circuit 22, angular velocity sensors 22a and 22b that detect vertical / horizontal vibrations, and a shake detection that performs shake detection using these sensor signals. Circuits 23a and 23b, a display unit 24 and a display drive circuit 25, an operation input unit 26, a program memory 27, a data memory 28, a memory card 29, a USB terminal 30, and the like are provided.

  The display unit 24 includes, for example, a color liquid crystal device with a backlight, and displays a through image on the monitor as an electronic viewfinder in the shooting mode, while playing back and displaying the selected image and the like in the playback mode. The display drive circuit 25 receives the drive signal from the control unit 16 and drives the display unit 24 for display.

  The operation input unit 26 is used when a user performs a shooting operation or a reproduction operation. The operation input unit 26 includes various keys such as a “power” key, a “shutter” key, a “photograph” key, a “playback” key, a “strobe” key, a “zoom” key, a “menu” key, and a “cursor” key. Has operation keys.

  The program memory 27 stores various programs for operating the digital camera 11. Among them, a program for realizing the present invention is also included. The data memory 28 stores various data including a filter control table 28a described later. The memory card 29 is detachable from the main body of the digital camera 11 and is used as an external recording medium.

  Further, the digital camera 11 is provided with a battery 31 and a power supply control unit 32, and power is supplied from the power supply control unit 32 to each unit using the battery 31 as a drive source.

  Next, the configuration of each part of the digital camera 11 will be described.

(A) Spectral filter In the digital camera 11 according to the present embodiment, the transmission characteristics of the spectral filter 15 provided in front of the photographic lens 14 are switched and controlled so that spectral images for each of a plurality of wavelength regions are acquired, and these spectral images are obtained. By synthesizing the images, one color image is generated. In practice, enlargement / reduction processing for correcting chromatic aberration is performed when combining the spectral images, which will be described in detail later.

  Here, a liquid crystal tuning filter (LCTF), a liquid crystal Fabry-Perot etalon filter (LCFP), or the like is used as the spectral filter 15. Before describing the configurations of these filters, the configurations of the Rio filter and the Fabry-Perot etalon filter, which are the basis of these filter principles, will be described.

(Rio filter)
FIG. 2 is a diagram showing the configuration of the Rio filter, and an example of a three-layer structure of A to C is shown. In the figure, reference numerals 41a, 41b, 41c and 41d denote polarizing plates, and 42a, 42b and 42c denote crystal plates. FIG. 3 is a diagram showing the transmission characteristics of the Rio filter. Waveforms (A), (B), and (C) show the transmission wavelengths of light in the A, B, and C layers of FIG. Waveforms (A + B) and (A + B + C) indicate the transmission wavelengths of light in the A layer + B layer and the A layer + B layer + C layer of FIG.

  As shown in FIG. 2, in the Rio filter, crystal plates 42a, 42b, and 42c having birefringence such as calcite and quartz are disposed between parallel polarizing plates 41a, 41b, 41c, and 41d. It has a structure.

  If only one layer is described, the light incident from the polarizing plate 41a and transmitted through the crystal plate 42a is separated into two light beams of normal light and extraordinary light in vibration directions perpendicular to each other. have.

Here, assuming that the thickness of the crystal plate 42a is d, the refractive index N _e for the light linearly polarized in the X-axis direction and the refractive index N _o for the light linearly polarized in the Y-axis direction. In this case, the phase difference δ and the transmittance T are expressed as follows.

δ = (2π / λ) (N _e −N _o ) d (1)
T = cos ² (δ / 2) (2)
In the separated normal light and extraordinary light, only light having a wavelength equal to an integral multiple of the optical path length in the same polarization state is emitted from the crystal plate 42a. When the crystal plate 42b is rotated 45 degrees between the two parallel polarizing plates 41a and 41b, the entire wavelength characteristic is periodically made up of a number of transmission peaks as shown by the waveform (A) in FIG. There is a comb-like transmission characteristic. By rotating the angle of the crystal plate 42a with a motor or the like, the peak of the transmission wavelength can be changed and the filter characteristics can be tuned.

Further, as in the example of FIG. 2, ^Nk (here, three) crystal plates 42a, 42b, and 42c are used, and dk = 2 ^k so that the thickness d of the previous crystal plate is doubled in order. ^When stacked as ⁻¹ × d (k: 1, 2,..., N−1), it is possible to finally obtain a narrow band characteristic as shown by the waveform (A + B + C) in FIG. Thereby, only the light of a desired wavelength can be selected from many peaks of the transmission wavelength. The overall transmittance T by the multilayer filter is expressed by the following equation when x = δ / 2.

T = T ₁・ T ₂・ T ₃・ ・ ・ ・ T _N-1
= Cos ² (x), cos ² (2x), cos ² (4x), ... cos ² (2 ^N-1 x) (3)
(Fabry-Perot Etalon Filter)
FIG. 4 is a diagram showing the principle of the Fabry-Perot etalon filter, in which 43a and 43b are semi-transparent mirrors (high reflection and low constant absorption mirrors), 44 is a lens system, and 45 is a focal plane (imaging device). Indicates. FIG. 5 is a diagram showing a transmission characteristic pattern of a Fabry-Perot etalon filter.

  The Fabry-Perot etalon filter transmits only light in a narrow wavelength range by utilizing the interference effect of multiple reflected light rays. It has a simple structure in which a reflective film such as a metal thin film or a dielectric multilayer thin film is coated on both surfaces of a parallel plate of quartz or the inner surfaces of two glass plates, and is widely used in various optical devices.

  As shown in FIG. 4, the light beam that has passed through the semi-transparent mirror 42 a and entered the inside is subjected to multiple reflections between the semi-transparent mirror 42 a and the semi-transparent mirror 42 b. The wavefront of the transmitted light is a superposition of the component wavefronts that are transmitted after receiving an even number of reflections. When the phase difference is δ, it is expressed by the following equation.

δ = (2π / λ) 2nd cos θ
= 4πnd cosθ / λ (4)
For the incident light Iin, the transmitted light It is
Since It = Iin × (1−R) ² / {(1−R) ² + 4Rsin ² (δ)}, the transmittance T is expressed by the following equation.

T = (1-R) ² / {(1-R) ² + 4Rsin ² (δ)} (5)
Here, δ: phase difference, λ: wavelength, θ: incident angle, d: physical distance between mirrors, n: refractive index of medium (n = 1 in the case of air), and R: reflectance of mirror.

  The transmitted light is maximized when there is no phase difference between the component wavefronts. At this time, the difference in optical distance is an integral multiple of the wavelength λ as follows.

mλ = 2nd cos θ (m = 1, 2, 3,...) (6)
At this time, at other wavelengths, canceling interference occurs between the transmitted component wavefronts, and the transmitted light is reduced to near zero.

Although the semi-transparent mirrors 42a and 42b can be coated with a metal film in which Ag, Au, Al, Cr, Rh, or the like is vapor-deposited with visible light, a multilayer dielectric thin film or the like is mainly used because of a large absorption loss. In the visible light region, a dielectric multilayer film in which a high refractive index H film (ZnS or the like) and a low refractive index L film (MgF ₂ or the like) are alternately stacked by 13 layers each having a thickness of λ / 4 is 99.5%. A degree of reflectivity is obtained.

  The distance d between the semi-transparent mirrors 42a and 42b can be designed variously from several microns (μm) to several centimeters (cm). By changing the distance d or the refractive index n of the medium, the wavelength to be transmitted can be selected. Further, the wavelength characteristic can be finely adjusted by adjusting the inclination of the filter.

  The Fabry-Perot etalon filter has a very high resolution compared to a prism or a diffraction grating, and has a higher transmittance and less absorption than a Rio filter using a polarizing plate. The value obtained by dividing the interval FSR (Free Spectral Range) with the adjacent peak wavelength by the full width at half maximum (FWHM) of the transmission peak, which is the minimum bandwidth, is called Finesse. Represent. If the finesse is F, it can be expressed as follows.

F = FSR / FWHM
= Δλ / δλ
= Π√R / (1-R) (7)
Here, the interval FSR is expressed as follows.

FSR = Δλ
= Λ ₀ ² / (2nd) (8)
Further, the full width at half maximum FWHM of the peak wavelength is expressed as follows.

FWHM = δλ
= FSR / F (9)
As shown in the transmittance characteristics of FIG. 5, as the reflectance R of the mirror surface is increased, the finesse F is increased, and the wavelength resolution FWHM = δλ can be narrowed and the transmission peak can be sharpened. Further, the intensity It (θ, λ) of the transmitted light having the wavelength λ incident at the incident angle θ is expressed by the following equation.

It (θ, λ) = I0 (λ) / [1+ {4R / (1-R) ² } sin ² (2πnd · cos θ / λ)]
= I0 (λ) / {1+ (F / π) ² sin ² (δ / 2)} (10)
Here, I0 (λ) represents the transmitted light intensity at the center of the concentric interference pattern (Hadinger fringe).

  If the light source is monochromatic (single wavelength), the etalon will only transmit light at incident angles that meet certain conditions. For this reason, when a monochromatic spherical wave is incident, a concentric ring (interference pattern) is generated.

  When a Fabry-Perot etalon (the one with a fixed interval is called an etalon plate) is used as a spectral filter, the incident angle θ is made smaller than the incident angle corresponding to the innermost interference ring (ring). In addition, it is necessary to limit the viewing angle FOV (Field of View) of the following equation.

FOV = √ {(8 / λ) × δλ} (11)
Transmission characteristics can be varied by combining the above-mentioned Rio filter and Fabry-Perot etalon filter with a birefringent element such as a liquid crystal element or an electro-optic crystal in which liquid crystal molecules are aligned in parallel and sealed. A narrow-band filter can be configured, and spectroscopic imaging can be performed at a desired wavelength.

  Hereinafter, a liquid crystal tuning filter (LCTF) and a liquid crystal Fabry-Perot etalon filter (LCFP) used as the electronically controllable spectral filter 15 will be described.

(LCD tuning filter)
FIG. 6 is a diagram showing the principle of the liquid crystal tuning filter. In the figure, 51 and 52 are polarizers (polarizing plates), 53 is a liquid crystal element, 54 is a transparent electrode, 55 is a liquid crystal molecule, and 56 is an alternating voltage. FIG. 7 is a diagram illustrating a configuration example of the liquid crystal tuning filter. In the figure, 61 and 62 are polarizing plates, 63 is a fixed crystal plate, 64 is a liquid crystal panel, and 65 is an alternating voltage.

  As shown in FIG. 7, the liquid crystal tuning filter has a sandwich structure in which a liquid crystal panel 64 and a crystal plate 64 having birefringence such as crystal are sandwiched between two polarizing plates 61 and 62. is there. In the example of FIG. 7, a multistage type is formed by stacking a plurality of stages. This is the same as the structure in which a liquid crystal element is inserted in each layer of the Rio filter shown in FIG. However, in the Rio filter, the filter characteristics were adjusted by rotating the crystal plate with a motor, etc., whereas in the liquid crystal tuned filter, the crystal plate was fixed, and the filter characteristics were adjusted by moving the liquid crystal element with voltage. It differs in the point to adjust.

  That is, the principle of the liquid crystal tuning filter will be briefly explained. As shown in FIG. 6, the light incident through the polarizer 51 on the input side is set at a crystal axis of 45 degrees with respect to the polarization axis of the polarizing plate 51. The birefringent crystal plate (not shown) is divided into two components of ordinary light and extraordinary light having different phase velocities.

  Here, due to the difference in refractive index between the major axis direction and the minor axis direction of the liquid crystal molecules 55, an optical path length difference (Δφ) between the light polarized in the major axis direction and the light in the orthogonal polarization direction. = 2πΔz / λ). When the voltage applied between the pair of transparent electrodes 54 is changed, the major axis direction of the liquid crystal molecules 55 is inclined, so that the optical path length difference is reduced. Depending on the value of the voltage (V) applied between the transparent electrodes 54, the refractive index of one of the crystal axes of the liquid crystal molecules 55 changes, so that one light is delayed compared to the other light.

  Thus, the liquid crystal element 53 functions as a phase retarder, and the two components exiting the liquid crystal element 53 are combined by the polarizer plate 52 on the output side, but have periodic transmission characteristics with respect to wavelength due to interference.

  The portion indicated by the dotted line frame in FIG. 7 is a single step, and the thickness t of the crystal plate 63 is successively doubled so that the final transmission characteristic of incident light is narrowed. It can be a band. In this case, if there is only one stage, a broad characteristic such as the waveform (A) in FIG. 3 is obtained. However, by using a multistage structure, a narrow band characteristic such as the waveform (A + B + C) in FIG. 3 is obtained. be able to.

  As described above, in the liquid crystal tuned filter, instead of rotating the crystal plate like the Rio filter, the voltage applied between the transparent electrodes of the liquid crystal element inserted in each layer is controlled, and the wavelength of each layer is continuously adjusted. It can be varied at high speed, and the combination makes it possible to selectively transmit only light of a desired narrow band wavelength that transmits all layers.

  Even in the case of a single-stage liquid crystal tuned filter, by sampling the signal change between when a voltage is applied and when the voltage reaches a predetermined voltage value, the change in the refractive index due to the liquid crystal is used to change the wavelength. Different signals can be extracted. However, since the single stage has a broad characteristic as shown by the waveform (A) in FIG. 3, a multi-stage configuration that obtains a narrow band characteristic is preferable.

(Wavelength characteristics and wavelength selection control of liquid crystal tuned filter)
FIG. 8 is a diagram showing an example of the characteristics of the spectral transmittance in each layer of the liquid crystal tuning filter and the total spectral transmittance combining them. FIG. 9 is a diagram showing an example of a combination of transmission characteristics of each narrow band obtained by the liquid crystal tuning filter.

  As in the example of FIG. 8, in order to align the transmittance peak in all filters at a desired wavelength, the voltage of the AC (alternating current) or direct current (DC) rectangular wave applied to the liquid crystal is adjusted to obtain the desired peak. It is necessary to adjust the transmittance peak to a narrow band wavelength.

  FIG. 10 is a diagram showing an example of the change characteristics of the voltage applied to both ends of the liquid crystal of the liquid crystal tuning filter and the refractive index of the liquid crystal layer. FIG. 11 is a diagram showing an example of the change in spectral transmittance characteristics due to the voltage change of the liquid crystal tuning filter, and shows how the spectral transmittance changes when the voltage applied to both ends of the liquid crystal in a certain layer is changed. Has been.

  In the example of FIG. 11, when the voltage V = 0, the transmittance peaked at λa, and the transmittance became 0 at λb. When V = V1 is applied to both ends of the liquid crystal layer, the transmittance decreases at λa, and the transmittance reaches a peak at λb. In this way, when the voltage is increased, the bandwidth where the transmittance reaches a peak or 0 can be sequentially adjusted.

  Therefore, when a laminated liquid crystal tuning filter is used as the spectral filter 15, the characteristic data of the spectral transmittance at each voltage of each layer described above or the liquid crystal element of each layer is adjusted in order to adjust each wavelength (λi). The voltage value data is tabulated and stored in advance in the data memory 28 (see FIG. 1) as a filter control table 28a. The control unit 16 refers to the filter control table 28a, applies a predetermined voltage to the spectral filter 15 for each wavelength band, and adjusts and controls the filter characteristics (light transmission characteristics).

  In the liquid crystal tuning filter as shown in FIG. 7, polarizing plates are necessary on both sides of the liquid crystal and the crystal plate in order to block polarized light in unnecessary directions. In addition, in order to obtain a spectral image by capturing a selected wavelength band with light of only a narrow band of about 5 to 10 nm, the number of filter layers, that is, the number of crystal plates and liquid crystal layers is increased and transmitted simultaneously. It is necessary to separate wavelengths, and the number of polarizing plates increases, so the transmittance decreases. In this case, as seen in the transmission characteristic diagram of FIG. 9, there is a problem that the transmittance is considerably lowered (darkened) particularly on the short wavelength side. The transmittance varies between the central portion and the peripheral portion, and is not uniform.

  Further, in the liquid crystal tuned filter, high-speed shooting is limited when it takes time for the rise time of the liquid crystal or the wavelength band switching processing and adjustment processing. For example, when photographing the visible light region of 400 to 700 nm at every 10 nm wavelength interval, it is necessary to shoot 31 images, and if it takes about 50 ms or more for the rise time of the liquid crystal and the switching of the wavelength, the exposure condition is satisfied. However, since only about 20 shots (band) can be taken per second, there is a limitation that it takes 1 second or more to shoot all bands.

(Liquid crystal Fabry-Perot Etalon filter)
FIG. 12 is a diagram illustrating a configuration example of a liquid crystal Fabry-Perot etalon filter. In the figure, 71 is a substrate such as a glass plate or quartz plate, 72 is a spacer / sealing material, 73 is a liquid crystal, 74 is a dielectric reflecting film, 75 is a transparent ITO (indium tin oxyde) film, and 76 is an AC voltage. . FIGS. 13 and 14 are graphs showing the characteristics of the liquid crystal Fabry-Perot etalon filter. FIG. 13 shows the FSR in various gap dimensions, and FIG. 14 shows the transmittance characteristics of each layer.

  Liquid crystal Fabry-Perot Etalon. The filter has a liquid crystal layer sealed between two glass plates on which a thin film mirror is formed in the Fabry-Perot etalon filter using the multiple reflection of FIG. 4 and transparent electrodes are formed on both sides. is there. In the example of FIG. 12, a configuration having a multilayer structure is shown.

  In addition to optimally designing the mirror interval (gap) so as to have a predetermined wavelength characteristic, by changing the voltage applied to both side electrodes of the liquid crystal layer filling the gap width of the etalon, as in FIG. The refractive index n of the liquid crystal layer is changed to change the wavelength so as to give a transmittance peak to a wavelength that was not the peak until then, and is tuned to a desired transmission wavelength.

  In addition, by stacking etalons with different mirror spacings in multiple layers and changing the voltage applied to both ends of the liquid crystal layer provided in each layer, only the light of the desired narrowband wavelength that passes through all the filters in multiple layers is imaged. Can be used for spectroscopic photography.

  However, as a characteristic of the liquid crystal, this refractive index change functions only in one of the two orthogonal components of polarized light, so other components cannot contribute to tuning, and LCFP and It is necessary to insert a polarizing plate in series.

(Design of liquid crystal Fabry-Perot etalon)
When the operating wavelength range of a filter used in spectroscopic imaging is, for example, the entire visible light with a wavelength of 400 nm to 700 nm, it is necessary to deposit a coating having high reflectivity over the entire area on an etalon substrate with high flatness. .

  In addition, the finesse F that can be practically and easily realized from the reciprocity of the reflectance and transmittance of the coating, the flatness of the etalon surface and the parallel accuracy of the interval, and the like are, for example, F ≦ 8 at a wavelength of 400 nm and a wavelength of 600 nm. F ≦ 10 at a wavelength of 800 nm, F ≦ 12 at a wavelength of 800 nm, F ≦ 15 at a wavelength of 1200 nm, F ≦ 20 at a wavelength of 1500 nm, and so on.

  When it is desired to set the wavelength resolution (minimum bandwidth) in a desired band to FWHM = δλ = 50 nm or 10 nm, for example, in the visible light range of 400 to 700 nm, it is considered that finesse F is about 8 to 10 From the above equation (6), finesse F = Δλ / δλ.

  Therefore, when δλ = 50 nm, the peak wavelength interval FSR = Δλ = δλ × F = 50 nm × 8 = 400 nm, and even a single etalon can be used in the entire visible light range, but when δλ = 10 nm, FSR = δλ × F = 10 nm × 8 = 80 nm, and 3 to 4 peak wavelengths are simultaneously transmitted within the band, and 3 to 4 order separation filters are required.

  Further, as shown in FIG. 13, even if a desired FSR is possible in terms of finesse, for example, the minimum gap width of etalon that can be realized from the relationship between the FSR and the wavelength λ with respect to various gap widths (mirror intervals). Is 3 μm, a single etalon can obtain an FSR of only about 30 to 80 nm over the entire visible light range, and thus it is understood that about 4 to 10 order separation filters are required. In such a case, a multilayer LCFP in which a plurality of etalon is combined is used.

(Combination of multi-layer LCFP)
When multiple etalons are used in series, the first etalon with the larger gap width (wavelength-resolved etalon) defines the transmission width of the entire system, and the second etalon with the smaller gap width (order suppression etalon). Defines the FSR. The overall system FSR depends on the ratio of the FSRs of both etalons.

And FSR ₁ of the first etalon, an integer ratio of the FSR ₂ of the second etalon, when can be represented by B / A, is expressed by the following formula.

FSR = A × FSR ₁ = B × FSR ₂ (12)
When B = 1, the FSR _{2 of} the second etalon itself becomes the FSR of the entire system. Otherwise, the overall FSR is B times larger than the FSR _{2 of the} order suppression etalon.

  From the equation (12), in the system combining two etalons, the FSR of the wavelength-resolved etalon is expanded A times, and the total number of transmission bands that can exist in the FSR of the entire system is also A times (FSR expansion coefficient). ). In order to minimize the number of order separation filters, it is necessary to maximize the etalon FSR within a range that does not exceed the tunable range (refractive index change range) of the liquid crystal.

  For example, in an etalon with a gap width of 3 μm, the visible light region (400 nm to 700 nm) is filled with 10 orders. However, as shown in FIG. 14, when an etalon with a gap width of 6 μm and 7.5 μm is combined, it can be obtained. The FSR that can be realized is equivalent to a single etalon having a gap width of 3 μm and a single etalon having a gap width of 1.5 μm.

(B) Image Sensor In this embodiment, a CMOS image sensor is used as the image sensor 12. When the image pickup device 12 is constituted by a CCD image sensor, the signal charge generated in the photodiode by the incident light is not amplified and transferred as it is through the vertical and horizontal CCD transfer paths, and the first FD ( Floating Diffusion) The signal voltage is amplified and output by an amplifier. The imaging signal output from the CCD is subjected to noise removal and sample and hold processing by a CDS (Correlated Double Sampling) circuit, amplified by an AGC (automatic gain control) amplifier, and ADC (A / D converter). Is converted into a digital imaging signal and output to a DSP (signal processing circuit).

  On the other hand, when the imaging device 12 is constituted by a CMOS image sensor, a general APS (Active Pixel Sensor) type CMOS image sensor includes an amplification device for each unit pixel circuit including a photodiode. Has been. The signal charge photoelectrically converted by the photodiode is once amplified by an amplifier in the pixel circuit, and is selected for each pixel selected by the XY address method by the row address selection signal from the vertical scanning circuit and the column selection signal from the horizontal scanning circuit. Imaging signals can be taken out sequentially.

  Here, in the CMOS, it is possible to take out only the imaging signals of arbitrary pixels and regions in an arbitrary order without taking out them sequentially like a CCD. Therefore, when a predetermined region is cut out by digital zoom processing and read out at a high speed, etc. Can be read.

  In CCD, signal charge is transferred as it is, so it is vulnerable to smear and noise. However, CMOS can be read by random access for each pixel, and each pixel circuit is electrically separated, so it is resistant to transmission noise and the same. There is an advantage that a logic circuit such as an addition operation circuit and a signal processing circuit can be highly integrated around the image sensor in the CMOS manufacturing process.

  On the other hand, in CMOS, there are problems such as fixed pattern noise (FPN), dark current, and kTC noise due to variations in individual elements such as the threshold value of the amplifier for each pixel, but recently, a structure using embedded photodiodes and FD amplifiers. As a result, dark current and KTC noise can be reduced.

  Also, fixed pattern noise (FPN) can be removed by subtracting the signal before and after resetting the photodiode by a column type CDS / ADC circuit or the like provided in a column circuit arranged in parallel for each column signal line. Therefore, an integration type, a cyclic type, a sequential type or the like AD converter is incorporated in each column circuit, and an image pickup signal can be output as a digital signal.

  Here, when the image sensor 12 is used in a high-speed spectroscopic camera, an image area of an arbitrary size is selected and an image signal of pixels in the area can be read out.

  In addition, an adder circuit and an arithmetic circuit for adding image signals of a plurality of pixels as digital signals are provided in a subsequent stage or a horizontal scanning circuit of a CDS / ADC circuit (not shown), so that the selected area can be used during digital zoom or high-sensitivity shooting. The image signal obtained by adding a plurality of pixels of the pixel data for each arbitrary matrix is read out. As a result, the shooting sensitivity per pixel can be increased substantially by the number of additions, shooting with good exposure can be achieved even with a short exposure time, and imaging signals with a small amount of image data even during high-speed movie shooting or continuous shooting. It is desirable to be able to output by converting to.

  The image pickup signal of the image pickup device 12 is sequentially output as a column signal selected by the column selection signal of the horizontal scanning circuit from the CDS / ADC circuit. At this time, it is output as a parallel digital signal in synchronization with a high-speed clock, or the parallel digital signal is encoded, converted by a parallel / serial conversion circuit (not shown), and output as a serial digital imaging signal. Thereby, it is possible to transfer and output a high-resolution imaging signal to the DSP unit 13 at a high rate.

  As described above, the digital signal of the imaging signal read from the imaging element 12 is sequentially converted into a serial (serial) digital signal by the parallel / serial conversion circuit and transferred to the DSP unit 13. In order to capture an image with a high resolution and a high-speed frame, naturally, it is necessary to transfer the imaging signal to the DSP unit 13 at a high speed.

  Here, in the general CMOS input / output circuit, the amplitude of the input / output signal is swung within the full range of the power supply voltage range, so that the power consumption is increased and the transfer speed is also reduced. Therefore, for example, an input / output circuit of CML (Current Mode Logic) or LVDS (Low-Voltage Differential Signaling) is used.

  In a CML system input / output circuit, a method is used in which a transistor is used in an unsaturated region to reduce impedance and turn on / off current rather than swing voltage. Therefore, the amount of charge / discharge of the stray capacitance can be reduced and high speed operation can be performed.

  In addition, the LVDS input / output circuit is a differential signal system that carries information using two signal lines, and can transmit data at a high speed of several hundred to several thousand Mbps (megabits / second) per single channel. In addition, the number of signal lines of the internal bus can be reduced as a differential data transmission system with low power consumption at the mW level. In LVDS, common mode noise can be removed by using a current mode driver and a small amplitude that swings within the upper and lower amplitudes of 0.3V around the + 1.2V potential, and high noise resistance is obtained over a wide frequency range. It is done.

(C) DSP
The digital image signal read from the image sensor 12 is given to the DSP unit 13. The DSP unit 13 first performs shading correction, black level correction, defective pixel correction, and the like, and then amplifies the digital AGC and performs white balance adjustment, color balance adjustment, and the like.

  Here, in an ordinary RGB three-color image sensor, digital image data having gradation values for each RGB color difference component for each pixel according to the arrangement of a mosaic RGB color filter provided in front of the image sensor The process of converting to (color interpolation process) is performed. On the other hand, the present embodiment is configured to acquire a spectral image for each wavelength band while sequentially switching the transmission characteristics of the spectral filter 15 by continuous shooting at a high speed without providing the image sensor 12 with a color filter. ing.

  FIG. 15 is a block diagram showing a functional configuration of the DSP unit 13 of the digital camera 11 in the embodiment, showing a configuration for processing a plurality of spectral images obtained by continuous shooting.

  The DSP unit 13 is provided with a buffer memory 81, a correction processing unit 82, a composition processing unit 83, and a correction table 84. As shown in FIG. 16, the buffer memory 81 stores a spectral image for each wavelength band obtained by continuous imaging.

  The correction processing unit 82 corrects chromatic aberration by performing enlargement / reduction processing on each spectral image stored in the buffer memory 81 in accordance with each wavelength band. At this time, when the photographing lens 14 is a zoom lens, a focal length that changes depending on the zoom magnification is detected, and chromatic aberration characteristic data in each wavelength band corresponding to the focal length is read from the correction table 84, and the chromatic aberration characteristic is read. The chromatic aberration in each wavelength band is corrected based on the data. The composition processing unit 83 synthesizes the spectral images corrected by the correction processing unit 82 to generate one photographed image.

  The correction table 84 stores chromatic aberration characteristic data ΔX (λi) and ΔY (λi) for each wavelength band in the photographing lens 14 in advance for each focal length.

  FIG. 17 shows an example of chromatic aberration characteristics for each wavelength band in the photographing lens 14 of the digital camera 11. The horizontal axis indicates the wavelength λ, and the vertical axis indicates the chromatic aberration amount ΔY in the Y direction at the focal length f = f1.

  Actually, when the DSP unit 13 acquires each spectral image, the following processing is performed in order to convert these spectral images into one broadband captured shadow image.

(Correction processing of spectral characteristics of imaging system)
For each wavelength band (λi), the transmittance T of the spectral filter 15 and the spectral sensitivity S (λi) of the image sensor 12 are stored in advance in a spectral characteristic table 85 as shown in FIG. The DSP unit 13 multiplies the luminance signal V (x, y; λi) of the spectral image in each wavelength band λi by a predetermined ratio corresponding to the reciprocal of these to correct the sensitivity characteristic variation for each wavelength band. A spectral image V ′ (x, y; λi) is obtained.

V ′ (x, y; λi) = V (x, y; λi) / T (λi) · S (λi) (13)
(Tristimulus value calculation process)
Further, the DSP unit 13 refers to a color matching function table 86 as shown in FIG. 19, and r￣ (λi), g￣ (λi), b￣ (λi) in the wavelength band (λi) of each spectral image. The tristimulus value Ri for each pixel (x, y) is obtained by multiplying the color matching functions.

Ri (x, y) = V '(x, y; λ i) × r￣ (λ i)
Gi (x, y) = V '(x, y; λ i) × g￣ (λ i)
Bi (x, y) = V '(x, y; λ i) × b￣ (λ i) (14)
(Multiplane addition processing)
Further, the DSP unit 13 adds and synthesizes the RGB values of each pixel (x, y) for each wavelength band (λi) and converts it into a single piece of broadband image data.

R (x, y) = Σ _i Ri (x, y)
G (x, y) = Σ _i Gi (x, y)
B (x, y) = Σ _i Bi (x, y) (15)
Note that tone correction and gamma correction are performed in accordance with the gamma characteristics of a standard monitor, etc., and conversion to other color space coordinates such as rgb chromaticity values and YUV (YCrCb) signals for each pixel (x, y) is performed. May be output.

  In this way, a spectral image that is continuously shot at a high speed within a minute time that is substantially the same timing for each of a plurality of wavelength bands is read at high speed, and these are added and synthesized to produce a single high-resolution image with high color reproducibility. Broadband image data is generated so that it can be output or recorded.

Next, the operation of the embodiment will be described.
20 and 21 are flowcharts showing the processing operation at the time of photographing by the digital camera 11 in the embodiment, FIG. 20 shows the flow of the entire processing, and FIG. 21 shows the processing related to the spectral photographing.

  Each process shown in this flowchart is stored in advance in the program memory 27 shown in FIG. 1 in the form of a program code. The control unit 16, which is a computer, reads the program and controls the respective units of the digital camera 11 to execute the following processing.

  That is, as shown in FIG. 20, when a shooting mode is set through the operation input unit 26 (Yes in step S101), the control unit 16 first sets shooting conditions such as a shutter speed as an initial setting. A predetermined voltage is applied to the spectral filter 15 to set a transmission wavelength band for a through image (step S102).

  Subsequently, the control unit 16 performs zoom processing and AF (automatic focusing) processing by moving the photographing lens 14 in accordance with operation of a zoom key provided in the operation input unit 26 (step S103). In addition, the control unit 16 obtains a through image of a subject in a predetermined band from the DSP unit 13 and displays it on the display unit 24 (step S104).

  Here, when shooting is instructed by operating a shutter key provided in the operation input unit 26 (Yes in step S105), the control unit 16 performs photometry processing, WB (white balance) processing, and the like (step S106). ), Spectral imaging processing is executed at predetermined time intervals (step S107). The spectroscopic imaging process will be described later in detail with reference to FIG.

  When a single captured image is obtained by the spectral imaging process, the control unit 16 compresses the captured image by a predetermined method such as JPEG (Joint Photographic Experts Group) (step S108), and then the data memory 28. Alternatively, it is recorded and held in the memory card 29 (step S109). Further, the control unit 16 displays the photographed image as a review on the display unit 24 (step S110), and ends the series of processes here.

Next, the spectral imaging process executed in step S107 will be described.
As shown in FIG. 21, the control unit 16 first sets the number (n) of wavelength bands and the exposure time (T / n) according to the photometric value and the imaging conditions (step S201). Subsequently, the control unit 16 selects the first wavelength band λ i (λ 1) (step S202), applies a predetermined voltage to the spectral filter 15, and sets the transmission wavelength band to λ i (step S203).

  The control unit 16 drives and controls a diaphragm mechanism (not shown) according to the set exposure time and drives and controls the imaging device 12 to capture a subject (steps S204 and S205), so that the wavelength band from the imaging device 12 is obtained. The spectral image of λi is read and given to the DSP unit 13 (step S206).

  Here, as shown in FIG. 15, the DSP unit 13 temporarily stores the spectral image of the wavelength band λi in the buffer memory 81, and then performs correction processing of chromatic aberration through the correction processing unit 82. Specifically, first, after detecting the focal length f of the photographing lens 14 including the zoom lens (step S207), chromatic aberration characteristic data in the X direction and the Y direction of the photographing lens 14 based on the focal length f and the wavelength band λi. ΔX (λi) and ΔY (λi) are read from the correction table 84 (step S208).

Next, the spectral image V (x, y; λ i) in the wavelength band λ i is obtained as {X + ΔX _f (λ i)} / X, which is the ratio between the chromatic aberration (magnification chromatic aberration) in the wavelength band λ i and the reference values X and Y. , {Y + ΔY _f (λ i)} / Y, that is, the reciprocal thereof, that is, X / {X + ΔX _f (λ i)} in the X direction and Y / {Y + ΔY _f (λ _i ) in the Y direction with respect to the original image. } Is enlarged or reduced, and the chromatic aberration corresponding to the wavelength band λi is corrected (step S209).

  Thereafter, in the same manner, n spectral images are acquired while sequentially switching the transmission characteristics of the spectral filter 15 in synchronization with the timing of continuous imaging, and these spectral images are obtained in accordance with the respective wavelength bands λi. The correction process of the chromatic aberration is performed (steps S210 and S211).

  Specifically, after correcting the chromatic aberration for each wavelength band, the tristimulus values Ri, Gi, Bi of each pixel are calculated, and then added up and summed up in all wavelength bands, so that an image signal of normal color space coordinates such as RGB is obtained. The process to convert to is included.

  When shooting of all n spectral images is completed (Yes in step S210), the DSP unit 13 combines the spectral images through the synthesis processing unit 83 to generate a single captured image, which is corrected for chromatic aberration. The captured image is transferred to the control unit 16 (step S212). The control unit 16 compresses the captured image by a predetermined method, and then records and saves it in the data memory 28 or the memory card 29.

  As described above, multiple spectral images with different wavelength bands are obtained by continuously shooting at high speed while switching the transmission characteristics of the spectral filter, and these are combined after being enlarged / reduced according to the wavelength band. By doing so, it is possible to correct the chromatic aberration while maintaining the resolution of each spectral image and obtain a high-quality captured image.

  In addition, since RGB image pickup signals using a general color filter are the total of light energy distributions in a wide wavelength band, light of many wavelengths (and thus different refractive indexes) is actually mixed. For this reason, even when the focus points are in focus, the image formation points are distributed with a certain width. In particular, the higher the image quality of the high-pixel, high-definition image sensor, the more prominent false colors and fringes become, and the average wavelength of each RGB Therefore, it is necessary to correct chromatic aberration or to perform sharpening processing such as edge enhancement filter processing.

  In contrast, in this method, not only images for three wavelengths of R, G, and B but also spectral images of each wavelength band are created using a spectral filter having a narrow band transmission characteristic. Therefore, such a problem can be solved and a higher quality image can be obtained.

  Further, in the case of a photographing lens whose focal length changes like a zoom lens, the characteristics of chromatic aberration also change according to the focal length. Therefore, by storing the chromatic aberration characteristic data according to the focal length in advance in a table for each wavelength band and storing it in the memory, even if the focal length changes, the chromatic aberration in each wavelength band can be corrected and corrected. Quality captured images can be obtained.

  In the above embodiment, the liquid crystal tuning filter (LCTF) and the liquid crystal Fabry-Perot etalon filter (LCFP) are exemplified as the electronically controllable spectral filter, but other filters may be used. In short, any filter having a narrow band transmission characteristic capable of producing a spectral image of each wavelength band can be applied regardless of its structure and accuracy.

  Moreover, although the said embodiment demonstrated the structure which has arrange | positioned the spectral filter in front of the photographic lens, the spectral filter is good also as a structure arrange | positioned after a photographic lens. In any case, it suffices to have a structure in which the split imaging light is incident on the image sensor.

  In the embodiment, the digital camera has been described as an example. However, the present invention can be applied to any apparatus having an imaging function such as a movie camera or an electronic device with a camera.

  In short, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  In addition, the method described in the above-described embodiment is a program that can be executed by a computer, such as a magnetic disk (flexible disk, hard disk, etc.), an optical disk (CD-ROM, DVD-ROM, etc.), a semiconductor memory, etc. The program can be written on a medium and applied to various apparatuses, or the program itself can be transmitted through a transmission medium such as a network and applied to various apparatuses. A computer that implements this apparatus reads a program recorded on a recording medium or a program provided via a transmission medium, and performs the above-described processing by controlling operations by this program.

FIG. 1 is a diagram showing a configuration when a digital camera capable of high-speed photography is taken as an example of an imaging apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing the configuration of the Rio filter. FIG. 3 is a diagram showing the transmission characteristics of the Rio filter. FIG. 4 is a diagram showing the principle of the Fabry-Perot etalon filter. FIG. 5 is a diagram showing a transmission characteristic pattern of a Fabry-Perot etalon filter. FIG. 6 is a diagram showing the principle of a liquid crystal tuning filter used as the spectral filter of the same embodiment. FIG. 7 is a diagram illustrating a configuration example of a liquid crystal tuning filter used as the spectral filter of the embodiment. FIG. 8 is a diagram showing an example of the characteristics of the spectral transmittance in each layer of the liquid crystal tuning filter and the total spectral transmittance combining them. FIG. 9 is a diagram showing an example of the combination of transmission characteristics of each narrow band obtained by the liquid crystal tuning filter. FIG. 10 is a diagram showing an example of the change characteristics of the voltage applied to both ends of the liquid crystal of the liquid crystal tuning filter and the refractive index of the liquid crystal layer. FIG. 11 is a diagram illustrating an example of a change in spectral transmittance characteristics due to a change in voltage of the liquid crystal tuning filter. FIG. 12 is a diagram showing a configuration example of a liquid crystal Fabry-Perot etalon filter used as the spectral filter of the same embodiment. FIG. 13 is a diagram showing FSR in various gap dimensions of the liquid crystal Fabry-Perot etalon filter. FIG. 14 is a diagram showing the transmittance characteristics of each layer of the liquid crystal Fabry-Perot etalon filter. FIG. 15 is a block diagram showing a functional configuration of a DSP unit of the digital camera in the embodiment. FIG. 16 is a diagram showing the contents of a buffer memory provided in the DSP unit of the digital camera in the embodiment. FIG. 17 is a diagram illustrating an example of chromatic aberration characteristics for each wavelength band of the imaging lens provided in the digital camera according to the embodiment. FIG. 18 is a view showing the contents of a spectral characteristic table provided in the digital camera in the embodiment. FIG. 19 is a view showing the contents of a color matching function table provided in the digital camera in the embodiment. FIG. 20 is a flowchart showing the overall processing at the time of shooting by the digital camera in the embodiment. FIG. 21 is a flowchart showing processing relating to spectral photographing of the digital camera in the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Digital camera, 12 ... Image sensor, 13 ... DSP part, 14 ... Shooting lens, 15 ... Spectral filter, 16 ... Control part, 17 ... Lens drive part, 18 ... Filter drive part, 19 ... Strobe, 20 ... Strobe drive Circuit, 21 ... LED, 22 ... LED drive circuit, 23a, 23b ... blur detection circuit, 24 ... display unit, 25 ... display drive circuit, 26 ... operation input unit, 27 ... program memory, 28 ... data memory, 28a ... Filter control table, 29 ... Memory card, 30 ... USB terminal, 31 ... Battery, 32 ... Power supply control unit, 41a, 41b, 41c, 41d ... Polarizing plate, 42a, 42b, 42c ... Crystal plate, 43a, 43b ... Half Transmission mirror, 51, 52 ... Polarizer (polarizing plate), 53 ... Liquid crystal element, 54 ... Transparent electrode, 55 ... Liquid crystal molecule, 56 ... AC voltage, 61, 62 ... Polarizing plate, 63 Fixed crystal plate, 64 ... liquid crystal panel, 65 ... alternating voltage, 71 ... substrate, 72 ... spacer / sealing material, 73 ... liquid crystal, 74 ... dielectric reflection film, 75 ... transparent ITO film, 76 ... alternating voltage, 81 Reference numeral: Buffer memory, 82: Correction processing unit, 83: Composition processing unit, 84: Correction table, 85: Spectral characteristic table, 86: Color matching function table

Claims (3)

An image sensor that converts light incident through the taking lens into an electrical signal;
A spectral filter disposed in front of the photographing lens and having a narrow-band transmission characteristic;
Table means storing chromatic aberration characteristic data corresponding to the focal length of the photographing lens for each wavelength region;
Filter driving means for sequentially switching transmission characteristics of the spectral filter by continuous photographing;
In conjunction with the switching operation of the spectral filter by the filter driving means, imaging control means for acquiring spectral images for each of a plurality of wavelength regions from the imaging device in a time-sharing manner,
Read characteristic data of chromatic aberration of each wavelength region corresponding to the focal length at the time of photographing from the table means, and based on the characteristic data, each of a plurality of spectral images sequentially obtained by the photographing control means corresponds to the wavelength region. Correction processing means for correcting the chromatic aberration,
An image pickup apparatus comprising: a combining processing unit configured to combine each spectral image corrected by the correction processing unit to generate one captured image. An image sensor that converts light incident through the photographing lens into an electrical signal, a spectral filter that is disposed in front of the photographing lens and has a narrow-band transmission characteristic, and chromatic aberration characteristic data corresponding to the focal length of the photographing lens In a method for correcting chromatic aberration of an imaging apparatus comprising: a table storing each wavelength region;
A first step of sequentially switching transmission characteristics of the spectral filter by continuous shooting;
A second step of acquiring, in a time division manner, spectral images for each of a plurality of wavelength regions from the image sensor in conjunction with the switching operation of the spectral filter in the first step;
The characteristic data of the chromatic aberration of each wavelength region corresponding to the focal length at the time of photographing is read from the table, and based on the characteristic data, each of the plurality of spectral images sequentially obtained in the second step is stored in the wavelength region. A third step of performing a corresponding chromatic aberration correction process;
A fourth step of synthesizing the spectral images corrected by the third step to generate one captured image;
A chromatic aberration correction method comprising: An image sensor that converts light incident through the photographing lens into an electrical signal, a spectral filter that is disposed in front of the photographing lens and has a narrow-band transmission characteristic, and chromatic aberration characteristic data corresponding to the focal length of the photographing lens A computer that stores an image for each wavelength region, and a computer that controls the imaging device,
A first function for sequentially switching transmission characteristics of the spectral filter by continuous shooting;
A second function for acquiring, in a time-division manner, spectral images for each of a plurality of wavelength regions from the imaging device in conjunction with the switching operation of the spectral filter by the first function;
The characteristic data of the chromatic aberration of each wavelength region corresponding to the focal length at the time of shooting is read from the table, and based on the characteristic data, each of the plurality of spectral images sequentially obtained by the second function is stored in the wavelength region. A third function for performing a correction process of the corresponding chromatic aberration,
A fourth function for synthesizing the spectral images corrected by the third function to generate one captured image
A program characterized by realizing.

Images