JP2017220765A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus on which a lens suitable for miniaturizing is mounted with a precondition of an image recovery after manufacturing error adjustment.SOLUTION: An imaging apparatus comprises: a zoom lens; an image pickup device; and an image processing part, and performs an image recovery processing by performing a convolution processing to an image with an image recovery filter generated so that a filter value has a two-dimensional distribution on the basis of aberration information of the zoom lens. The zoom lens adjusts one-sided defocusing caused by a manufacturing error so as to be reduced by being decentered a part of a specific lens groups in accordance with a specific zoom state in a manufacturing step of the lens. Further, the zoom lens adapts the image recovery filter recovering a coma aberration remained after the adjustment.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a compact and low-cost zoom lens suitable for a digital still camera and the like, and an image pickup apparatus having the zoom lens, and particularly to a digital camera excellent in portability in which the total lens length is shortened. is there.

  Along with the digitization of information, various correction processing methods have been proposed for captured images by handling images as signal values. When a subject is imaged with a digital camera to form an image, the obtained image is deteriorated to some extent due to aberrations of the imaging optical system.

  The blur component of the image is caused by spherical aberration, coma, field curvature, astigmatism, and the like of the optical system. The blur component of the image due to these aberrations is the one in which the light beam emitted from one point of the subject should be collected again at one point on the imaging surface and forms an image when there is no aberration and no influence of diffraction. pointing. Optically, this is called a point spread function (PSF). This is called a blur component in the image. Speaking of image blur, for example, an out-of-focus image is also blurred, but here it refers to an image that is blurred due to the above-mentioned aberration of the optical system even if it is in focus.

  In addition, regarding color bleeding in a color image caused by on-axis chromatic aberration, chromatic spherical aberration, and chromatic coma in the optical system, it can be said that the blurring is different for each wavelength of light. Further, in the case where the lateral color shift is caused by the chromatic aberration of magnification of the optical system, it can be said that it is a positional shift or a phase shift due to a difference in imaging magnification for each wavelength of light.

  An optical transfer function (OTF, Optical Transfer Function) obtained by Fourier-transforming the point spread function (PSF) is aberration frequency component information and is represented by a complex number. The absolute value of the optical transfer function (OTF), that is, the amplitude component is called MTF (Modulation Transfer Function), and the phase component is called PTF (Phase Transfer Function). Therefore, MTF and PTF are the frequency characteristics of the amplitude component and phase component of image degradation due to aberration, respectively. Here, the phase component is represented by the following formula a with the phase angle. Re (OTF) and Im (OTF) represent the real part and the imaginary part of the OTF, respectively.

PTF = tan ⁻¹ (Im (OTF) / Re (OTF)) (Expression a)
Thus, since the optical transfer function (OTF) of the imaging optical system deteriorates the amplitude component and the phase component of the image, the deteriorated image is in a state where each point of the subject is asymmetrically blurred like coma aberration. .

  Further, lateral chromatic aberration is caused by shifting the imaging position due to the difference in imaging magnification for each wavelength of light, and acquiring this as, for example, RGB color components according to the spectral characteristics of the imaging device. Accordingly, not only the image formation position is shifted between RGB, but also the image formation position shift for each wavelength, that is, the spread of the image due to the phase shift, occurs in each color component. Therefore, the chromatic aberration of magnification is not merely a parallel shift color shift, but unless otherwise specified, the color shift is described as having the same meaning as the lateral chromatic aberration.

  As a method for correcting the deterioration of the amplitude (MTF) and the deterioration of the phase (PTF), a method of correcting using the information of the optical transfer function (OTF) of the imaging optical system is known. This method is called the term image restoration or image restoration.

  Hereinafter, processing for correcting image degradation using information on the optical transfer function (OTF) of the imaging optical system will be referred to as image restoration processing or restoration processing. Although details will be described later, as one of image restoration methods, there is known a method of convolving an image restoration filter having an inverse characteristic of an optical transfer function (OTF) with respect to an input image (non-patent document 1). ).

  In order to effectively use image restoration, it is necessary to obtain more accurate OTF information of the imaging optical system. For example, if there is design value information of the imaging optical system, the method for obtaining the OTF can be obtained by calculation from the information. It can also be obtained by photographing a point light source and subjecting the intensity distribution to Fourier transform.

  Patent Document 1 discloses an invention that performs image processing while retaining a filter coefficient for correcting image degradation. By using these image restorations, an image deteriorated due to the aberration of the imaging optical system can be processed with high definition, and a high-definition image can be obtained.

  Patent Document 2 discloses an invention for performing image image processing that includes an adjustment step and a recovery step of an optical system, evaluates and classifies the imaging performance of the adjusted image, and applies a recovery filter to the filter corresponding to the classification. Has been. By using these image restorations, an image deteriorated due to a manufacturing error of the imaging optical system can be processed with high definition, and a high-definition image can be obtained.

JP 2005-509333 A JP 2012-113690 A

  By allowing lens aberration due to manufacturing errors on the premise of image restoration, the degree of freedom in designing the aberration sensitivity can be increased, and the photographic optical system can be reduced in size, increased in magnification, and increased in diameter. In order to reduce the size of the photographic optical system and achieve a high magnification while maintaining the same size as before, increasing the refractive power of each lens group constituting the photographic optical system increases the sensitivity to aberrations, resulting in manufacturing errors. The image deteriorates due to the aberration generated by the above.

  By correcting the deteriorated image to the same level as that of the conventional photographing optical system by image restoration, it becomes possible to achieve high specification of the lens while maintaining the same image quality.

  On the other hand, a manufacturing process is known in which an optical system of a digital camera corrects an error by displacing a part of the optical system in order to reduce performance deterioration due to one-side blur, coma aberration, and the like due to various manufacturing errors.

  However, these adjustments in the manufacturing process are adjusted at a site different from the cause of the manufacturing error in consideration of the simplicity of the process, so that there is a problem that the imaging performance deteriorates due to residual aberration caused by the adjustment. is there. It is possible to improve the functionality of the optical system by assuming that the aberration caused by the adjustment is restored, but the time required for the adjustment increases if an attempt is made to evaluate the image degradation after adjustment and select a restoration filter. However, there is a problem of increasing costs.

  The object of the present invention is to restore the adjusted image after the optical adjustment, and to select a zoom lens suitable for downsizing and large aperture, and to select a recovery processing filter by a simple method. An object of the present invention is to provide an imaging device that can be manufactured.

In order to achieve the above object, an imaging apparatus according to the present invention includes:
A zoom lens, an image sensor, and an image processing unit, and an image restoration filter created so that the filter value has a two-dimensional distribution based on the aberration information of the zoom lens of the previous period is used to control the image. Perform volume processing.

  In the imaging apparatus, wherein the image restoration process is performed, the zoom lens has a manufacturing error caused by displacing a part of a specific lens group in a specific zoom state in a process of manufacturing the lens in a direction substantially perpendicular to the optical axis. Make adjustments.

  In the adjustment step, adjustment is performed in a direction to reduce one-sided blur, and the image restoration filter that recovers coma aberration remaining after adjustment is applied.

  The recovery filter has means for storing a plurality of types, and means for measuring a displacement amount due to adjustment of the adjustment lens in the adjustment step. The displacement filter is manufactured by classifying the displacement amount and applying a recovery filter corresponding to the classification. It has been done.

  Alternatively, in the adjustment step, the same effect can be obtained even if the apparatus has a means for measuring the amount of displacement due to adjustment of the adjustment lens, and manufactures by classifying the amount of displacement and determining and adapting the recovery gain of the recovery filter corresponding to the classification. You can expect.

  Furthermore, in order to approach the best mode, the following configuration is preferably satisfied.

  In the image pickup apparatus, the aberration to be restored is coma aberration and chromatic coma aberration, and is performed in a specific region in a wide angle region or a telephoto region.

  The zoom lens mounted in the image pickup apparatus includes a negative first lens group, a positive second lens group, and a subsequent lens group from the object side.

  The second lens group includes at least three positive lenses, and is manufactured through a manufacturing process in which assembly adjustment is performed by displacing the positive lens disposed closest to the object side in a direction substantially perpendicular to the optical axis.

  The zoom lens mounted in the image pickup apparatus includes a positive first lens group, a negative second lens group, a positive third lens group, and a subsequent lens group from the object side.

  The third lens group includes at least three positive lenses and is manufactured through a manufacturing process in which assembly adjustment is performed by displacing the positive lens disposed closest to the object side in a direction substantially perpendicular to the optical axis.

  In the lens system, the first group having a negative first lens group, a positive second lens group, and a negative third lens group from the object side has a locus that is convex toward the image side during zooming from the wide angle end to the telephoto end. Corrects image plane fluctuations due to magnification change.

  The second group moves to the object side and is responsible for the main scaling. The third group draws a trajectory close to the second group, but corrects the image fluctuation in the intermediate area by changing the air distance from the second group.

  Focusing on short-distance objects by moving the third lens group toward the image side.

  The first lens group positive from the object side in the lens system The second lens group negative, the third lens group positive, the fourth lens group negative, the fifth lens group positive, and zooming from the wide-angle end to the telephoto end Each group moves, and the third group moves to the object side.

  A focusing operation on a short-distance object is performed by extending the fourth group or the fifth group to the object side.

  When the focal length of the entire lens group to be adjusted in the lens system is adjusted by fa and the maximum displacement amount when adjusting the lens unit closest to the object side in the direction perpendicular to the optical axis is Iy Satisfy the conditional expression.

0.3 <Iy / fa × 10000 <50 (1)
An image restoration process is performed by performing a convolution process on the image using an image restoration filter created so that a filter value has a two-dimensional distribution based on aberration information of the zoom lens.

In the imaging apparatus, the aberration in the zoom specific region to which the image restoration filter is applied when the adjustment lens is displaced by 0.01 × fa in the direction perpendicular to the optical axis satisfies the following numerical range.
0.35 <| (Δwyu7 + Δwyl7) | / 2p <16.0 (2)
0.00 <| (Δwyu7 + Δwyl7n) / (Δwyu-7 + Δwyl-7) | <3.5 (3)
fa: Focal length ΔWyu7 of the entire lens group including the adjusting lens: d-line lateral aberration amount of the upper line (70% of the effective luminous flux) at the image height of 70%
ΔWyl7: d-line lateral aberration amount at 70% of image height underline (70% of effective luminous flux)
ΔWyu-7: The amount of lateral aberration of the d-line of the upper line (70% of the effective luminous flux) at the image height of -70%
ΔWyl-7: d-line lateral aberration amount underlined at 70% image height (70% of effective luminous flux)
P: Pixel pitch
In the imaging apparatus, the filter region is an asymmetric region from the center to the periphery of the screen.

  In the imaging apparatus, the filter is adapted from the center to the peripheral area in the telephoto area.

  According to the present invention, it is possible to provide a zoom lens suitable for miniaturization and cost reduction and an image pickup apparatus capable of simple process processing on the premise of image restoration by the above-described configuration.

Lens sectional view of Example 1 Lens sectional view of Example 2 Longitudinal aberration diagram at the wide-angle end of Example 1 Aberration diagram in middle longitudinal direction of Example 1 Longitudinal aberration diagram at the telephoto end of Example 1 Lateral aberration diagram during adjustment at the telephoto end in Example 1 Longitudinal aberration diagram at the wide-angle end of Example 1 Longitudinal aberration diagram in the middle of Example 1 End longitudinal aberration diagram of Example 1 at telephoto Lateral aberration during adjustment at the telephoto end of Example 1 Explanatory drawing of the manufacturing error adjustment in Embodiment 1 of this invention Explanatory drawing of the restoration filter generation method after adjustment of the present invention Explanatory drawing of the image restoration filter concerning the image processing method of this invention Explanatory drawing of the image restoration filter concerning the image processing method of this invention Explanatory drawing of the correction state of the point image concerning the image processing of this invention Explanatory drawing of the amplitude and phase concerning the image processing of this invention Explanatory drawing of the adjustment flow of the present invention, Explanatory drawing of example of adjustment direction and recovery adaptation area of this invention

  First, definitions of terms used in the embodiments of the present invention and image restoration processing will be described with reference to the drawings. The image processing method described here can be used as appropriate in each embodiment described later.

[Input image]
The input image is a digital image obtained by receiving light with an image pickup device via an image pickup optical system, and is deteriorated by an optical transfer function (OTF) due to aberration of the image pickup optical system including a lens and various optical filters. Yes. The imaging optical system can also use a mirror (reflection surface) having a curvature in addition to the lens.

  Further, the color component of the input image has information on, for example, RGB color components. As the handling of color components, other commonly used color spaces such as brightness, hue, and saturation expressed in LCH, luminance expressed in YCbCr, and color difference signals can be selected and used. As other color spaces, XYZ, Lab, Yuv, and JCh can be used. It is also possible to use a color temperature.

  The input image and the output image can be accompanied by shooting conditions such as the focal length of the lens, aperture value, shooting distance, and various correction information for correcting this image. When the image is transferred from the imaging apparatus to another image processing apparatus and correction processing is performed, it is preferable to add shooting condition information and correction information to the image as described above. As another delivery method of the imaging condition information and the correction information, the imaging device and the image processing device can be directly or indirectly connected and delivered.

[Image recovery processing]
An outline of the image restoration processing is shown. The degraded image is g (x, y), the original image is f (x, y), and the point spread function (PSF) that is a Fourier pair of the optical transfer function (OTF) is h (x, y). Then, the following equation holds. Here, * indicates convolution (convolution integration, sum of products), and (x, y) indicates coordinates on the image.
g (x, y) = h (x, y) * f (x, y)
Moreover, when this is Fourier-transformed and converted into a display format on the frequency plane, it becomes a product format for each frequency as shown in the following equation. H is an optical transfer function (OTF) because it is a Fourier transform of the point spread function (PSF) h, and G and F are Fourier transforms of g and f, respectively. (U, v) indicates coordinates on a two-dimensional frequency plane, that is, a frequency.
G (u, v) = H (u, v) · F (u, v)
In order to obtain the original image from the captured degraded image, both sides may be divided by H as follows.
G (u, v) / H (u, v) = F (u, v)
This F (u, v), that is, G (u, v) / H (u, v) is subjected to inverse Fourier transform to return to the actual surface, whereby the original image f (x, y) is obtained as a restored image. It is done.

Here, ^assuming that the result of inverse Fourier transform of H ⁻¹ is R, the original image f (x, y) is obtained similarly by performing convolution processing on the actual image as in the following equation. be able to.
g (x, y) * R (x, y) = f (x, y)
This R (x, y) is called an image restoration filter. When the image is two-dimensional, generally this image restoration filter is also a two-dimensional filter having taps (cells) corresponding to each pixel of the image. In general, the greater the number of taps (cells) of the image restoration filter, the higher the restoration accuracy. Therefore, the number of taps that can be realized is set according to the required image quality, image processing capability, aberration characteristics, and the like. . Since the filter for image restoration needs to reflect at least aberration characteristics, it is a technical field that is different from the conventional edge enhancement filter (high-pass filter) of about 3 taps each in horizontal and vertical directions. Needless to say.

  Since the image restoration filter is based on the optical transfer function (OTF), it is possible to correct both the amplitude component and the deterioration of the phase component with high accuracy. In addition, since an actual image has a noise component, if an image restoration filter created by taking the reciprocal of the optical transfer function (OTF) as described above is used, the noise component is greatly amplified as the degraded image is restored. . This is because the MTF is raised so that the MTF (amplitude component) of the optical system is returned to 1 over the entire frequency in a state where the amplitude of noise is added to the amplitude component of the image.

  The MTF, which is amplitude degradation due to the optical system, returns to 1, but at the same time, the noise power spectrum also rises. As a result, the noise is amplified according to the degree to which the MTF is raised (recovery gain).

Therefore, when there is noise, a good image cannot be obtained as a viewing image. This can be expressed as follows: N represents a noise component.
G (u, v) = H (u, v) .F (u, v) + N (u, v)
G (u, v) / H (u, v) = F (u, v) + N (u, v) / H (u, v)
Regarding this point, for example, a method of controlling the degree of recovery according to the intensity ratio (SNR) of the image signal and the noise signal as in the Wiener filter shown in Equation 1 is known.

  M (u, v) is the frequency characteristic of the Wiener filter, and | H (u, v) | is the absolute value (MTF) of the optical transfer function (OTF). This method suppresses the recovery gain (recovery degree) as the MTF decreases for each frequency, and increases the recovery gain as the MTF increases. In general, since the MTF of the imaging optical system is high on the low frequency side and low on the high frequency side, it is a method of substantially suppressing the recovery gain on the high frequency side of the image.

  Schematic diagrams for explaining the image restoration filter are shown in FIGS.

  The image restoration filter can determine the number of taps according to the aberration characteristics of the image pickup optical system and the required restoration accuracy. In FIG. 13, an 11 × 11 tap two-dimensional filter is used as an example. In FIG. 13, values (coefficients) in each tap are omitted, but one section of this image restoration filter is shown in FIG. The distribution of the values (coefficient values) of each tap of the image restoration filter serves to return the signal value (PSF) spatially spread by the aberration to the original one point ideally.

  Each tap of the filter is subjected to convolution processing (convolution integration, product sum) in the image restoration processing step corresponding to each pixel of the image. In the convolution process, in order to improve the signal value of a certain pixel, the pixel coincides with the center of the image restoration filter. This is known as a process of taking the product of the image signal value and the filter coefficient value for each corresponding pixel of the image and the image restoration filter and replacing the sum as the signal value of the central pixel.

  The characteristics of image restoration in real space and frequency space will be described with reference to FIGS.

  FIG. 15A shows a PSF before recovery, and FIG. 15B shows a PSF after recovery. 16 (M) (a) shows the MTF before recovery, (M) (b) shows the MTF after recovery, (a) in FIG. 16 (P) shows the PTF before recovery, ( (B) of P) shows the PTF after recovery. The PSF before recovery has an asymmetric spread, and due to this asymmetry, the PTF has a non-linear value with respect to the frequency. Since the recovery process amplifies the MTF and corrects the PTF to zero, the PSF after recovery is symmetrical and sharp.

  The method for creating the image restoration filter can be obtained by performing inverse Fourier transform on a function designed based on the inverse function of the optical transfer function (OTF) of the imaging optical system. The image restoration filter used in the present invention can be appropriately changed. For example, the above-described Wiener filter can be used. When the Wiener filter is used, a real-space image restoration filter that is actually convolved with an image can be created by performing inverse Fourier transform on Equation (1).

Further, since the optical transfer function (OTF) changes according to the image height (image position) of the image pickup optical system even in one shooting state, the image restoration filter is changed and used according to the image height.
The above is the outline of the image restoration process.

  In an optical system having no manufacturing error in image restoration, it is conceivable to use a filter created from a design value. In an actual lens, since the decentering or tilting in each lens group or the decentering or tilting between the lens groups causes field curvature or one-sided blur, the aberration state is different from the design value. Image restoration cannot be performed if the state of the generated aberration is large, so adjustment is performed by displacing some of the lenses that make up the lens group in the direction perpendicular to the axis to reduce one-side blur caused by manufacturing errors. It is possible.

  For the lens to be displaced, a lens group suitable for adjustment is installed upward on the tool in consideration of the simplicity of the normal process, and the lens placed at the top on the tool is displaced so that adjustment with a low-cost tool can be performed. It is possible. Since the lens used for the adjustment is adjusted at a site different from the cause of the manufacturing error, residual aberration such as coma generated by the adjustment may occur. It is possible to improve the functionality of the optical system by assuming that the aberration caused by the adjustment is restored. However, if an attempt is made to evaluate the image degradation after adjustment and select a restoration filter, the adjusted image is evaluated. It takes time to make adjustments because a process is required.

  Therefore, the present invention is configured to include means for detecting and storing the adjustment amount and the adjustment direction during the adjustment action. When the lens to be adjusted is displaced, the one-side blur is changed and the coma aberration is generated at the same time. Therefore, although the one-side blur is reduced by the adjustment, the coma aberration may be increased.

  In view of this, there is provided means for preparing and recording a plurality of filters for correcting coma aberration and the like caused by the adjustment in accordance with the adjustment amount. A restoration filter is selected based on the adjustment amount detected in the adjustment step, and image restoration is performed to correct coma caused by the adjustment. On the premise of restoration of the adjusted image after optical adjustment, a low-cost imaging device is provided by a simple adjustment process by selecting a zoom lens suitable for downsizing and a recovery processing filter by a simple method.

  In Embodiment 1 of the present invention, the second group of the first group that is negative from the object side, the second group that is negative from the object side, and the first group that is negative from the object side, and the third group that is positive. It consists of a group and a successor group. Optical adjustment is performed by displacing the most object side lens of the second group in the former and the third group in the latter in the direction perpendicular to the optical axis.

  Actually, in the adjustment, even if it is decentered in parallel with the optical axis, there is a case where the tilt is about 5 degrees or less with respect to the direction perpendicular to the optical axis. In particular, when the lens surface is decentered along the lens barrel holding portion, the lens surface may be decentered along with the curvature of the contacting lens surface, but even in this case, the tilt is kept within 5 degrees.

  The first embodiment of the present invention has a zoom ratio of about 3 times, but particularly corresponds to a sensor larger than a normal compact digital camera. During zooming from the wide-angle end to the telephoto end, the first group has a locus convex toward the image side, and corrects the image plane variation due to zooming. The second group moves to the object side and is responsible for the main scaling. The third group draws a locus close to the second group, but the image plane variation in the intermediate region is corrected by changing the air distance from the second group. By moving the third lens group toward the image side, focusing operation on a short-distance object is performed.

In the second embodiment of the present invention, an optical system having a zoom ratio of about 4 times is provided. In particular, from the wide-angle end to the telephoto end, an optical system that is bright in all zoom ranges and has a small Fno is provided. From the object side, it has a positive first group, a negative second group, a positive third group, a negative fourth group, and a positive fifth group. During zooming from the wide-angle end to the telephoto end, the first lens group once moves to the image side, then moves to the object side, and is arranged from the wide-angle end to the object side at the telephoto end. The second group moves to the image side, and the third group moves to the object side. The diaphragm is arranged between the second group and the third group. The fourth group moves a minute amount relative to the image plane, and the fifth group moves.

  In Numerical Example 1, the second group is a group responsible for main image formation, and correction of spherical aberration and coma aberration is performed over the entire zoom range. The lens configuration of the second group is composed of four lenses, a positive lens, a positive lens, a negative lens, and a positive lens, from the object side. The positive lens arranged closest to the object side converges the divergent light beam emitted from the first group with a strong power positive lens and emits it to the subsequent lens side, so coma aberration when the lens is decentered or It has the property of greatly affecting the field curvature.

  In the manufacturing process of the entire lens system, decentering and tilting of a plurality of lenses constituting the second group, and decentering and tilting between the lens groups cause spherical aberration, coma aberration, and one-sided blur due to asymmetry of field curvature. Since the first lens of the second group described above is highly sensitive to aberrations, it is suitable for correcting deterioration in optical performance by adjusting aberrations occurring in other parts of the entire lens system during the manufacturing process. It is possible to adjust the eccentricity.

  For example, an adjustment error generated in the second group can be adjusted by performing adjustment on the tool before the second group is incorporated into the lens system. In addition, when the second lens group is installed after the second lens group is installed, and the leading lens of the second group is adjusted, aberrations caused by decentration and tilting of the second lens group and the subsequent lens group can be corrected. I can do it.

  The adjustment includes a method for adjusting the imaging performance and contrast in the vicinity of the central portion, and a method for adjusting so that one side blur in the peripheral portion is reduced. In the former case, the location where the error occurs and the location to be adjusted are different, so if the center contrast is corrected to near the design value, one side blur or astigmatism may occur due to the eccentricity due to the adjustment.

  In the latter case, on the contrary, the location where the error occurs and the location to be adjusted are different, so if one blur is corrected to near the design value, coma will occur due to the eccentricity due to the adjustment, and the contrast near the center and in the peripheral area will decrease There is. In such a lens, a reduction in contrast due to adjustment can be compensated by performing image processing correction in the recovery process.

  In the present invention, the aberration remaining after adjustment is corrected by reducing the curvature of field and allowing the coma in the center and the periphery, which is not good for the recovery process, and the adjusted coma is suitable for the recovery process. It is possible to perform a good recovery process by combining the aberrations. In this case, it is preferable to prepare a plurality of types of restoration processing filters according to the amount of residual aberration after adjustment and selectively adapt which filter is used.

  In the present invention, as a method for selecting the plurality of types of filters, a method is devised in which the displacement amount of the adjustment lens is measured, and the aberration remaining after the adjustment is predicted and selected from the displacement amount. With this method, it is possible to select a filter that can be applied instantaneously after adjustment, reducing the number of adjustment steps and reducing the manufacturing cost for adjustment integration. In this example, the coma aberration generated by the adjustment action as in Examples 1 and 2 appears in one direction, so that there is a tendency that the peripheral portion of the screen has different characteristics in the direction opposite to the direction in which the adjustment lens is moved.

On the other hand, in the direction, coma aberration occurs due to the eccentricity of the adjusting lens, and the MTF decreases.
In the reverse direction, there is a case where the MTF does not decrease due to the cancellation relationship with the aberration that the lens originally has. The degree of decrease in MTF in the region from the center to the periphery can be predicted to some extent from the adjustment amount of the adjustment lens, so the filter is applied only to the region where the coma generated in the peripheral region from the center of the angle of view is large. By doing so, the data capacity can be reduced.

In this case, there is an area where MTF decreases due to inward coma and color flare at the periphery of the screen, but even in lenses that have undergone general aberration correction that is not premised on recovery, this area also deteriorates. It can be omitted. The concept of typical filter generation in the present invention will be described by taking Numerical Example 1 as an example.

  11 to 12 show the adjustment method in the present invention of a lens having three groups of negative, positive and negative from the object side. In FIG. 11, the dotted line and the alternate long and short dash line indicate the portion where one blur occurs due to a manufacturing error. One-sided blur occurs due to the eccentricity or tilting of each lens constituting the partial second group indicated by the dotted line. The portion indicated by the alternate long and short dash line indicates the entire second group and the third group, but one-sided blur also occurs due to the relative eccentricity or collapse of the second group and the third group. By decentering the leading lens indicated by the solid line in the second lens unit in the direction perpendicular to the optical axis, the one-sided blur error can be adjusted to be small.

  FIG. 12 shows how the defocus characteristics of the MTF at the center and the periphery change due to the adjustment. A) in the figure is the state of the design value, and the MTF is sufficiently high at the periphery of the center of the screen, and the field curvature of the center and the periphery is not different in the + image height direction and -image height direction, and there is no blurring. It is.

  If there is a manufacturing error in the portion indicated by the dotted line and the alternate long and short dash line, a difference in image plane position between the + image height and the −image height occurs as shown in B), causing a one-sided blur. The image plane position in the + image height direction and in the −image height direction is represented by C) by decentering one positive lens in the solid line portion in a direction substantially perpendicular to the optical axis, as shown in C). You can align and adjust one blur. However, as shown in C), coma aberration is generated by decentering the adjustment lens in the solid line portion, and the MTF in the + image height direction at the center portion and the peripheral portion of the screen is lowered.

  The change in coma due to adjustment can be calculated from the change when only the adjustment lens is decentered, as shown in D). The MTF shown in D) includes both the one-side blur change and the coma aberration change due to the adjustment, but as shown in E), if the one-blurring component is removed from here, the reduction in the coma aberration due to the adjustment is estimated. I can do it.

  By creating a recovery filter from the characteristics shown in E) and applying it to the adjusted image, it is possible to correct image degradation due to the adjustment.

  In the adjusting method, there are a case where the second group is adjusted on the tool and a case where the second group is incorporated after the third group is incorporated in the product state and a part of the two groups is adjusted. In the former case, the error in the dotted line portion can be adjusted, and in the latter case, the error in both the dotted line portion and the one-dot chain line portion can be adjusted. Since a manufacturing error in the case of mass production of lenses differs depending on each lens, the amount of one-side blur before adjustment differs depending on the error amount, and the displacement amount due to adjustment of the adjustment lens also differs.

  In the present invention, a plurality of types of filters corresponding to the displacement amount and the displacement direction are prepared, the displacement amount and the displacement direction are obtained from the adjustment displacement amount measuring means, and any filter classified in advance from the information is adapted. To decide.

  In the present invention, it is possible to select an appropriate classification filter instantly from the amount of displacement at the time of adjustment without analyzing the image after adjustment, so that it is possible to reduce the number of assembly steps for adjustment.

  FIG. 17 shows a manufacturing flow of the imaging apparatus according to the present invention.

  In this flow, the recovery means is a plurality of types of filters classified in advance according to the above-described adjustment amount. To obtain an optical system with improved performance in a process that reduces the image evaluation process as much as possible by adjusting the optical system including manufacturing errors through image evaluation and performing recovery processing according to the displacement of the adjustment. I can do it.

  FIG. 18 is a diagram showing an example of the adjustment direction of the adjustment lens for optical adjustment and the recovery filter adaptive range.

  The lens viewed from the front of the camera conceptually shows the adjustment direction in the direction of the arrow and the adjustment amount in the length of the arrow. The hatched area on the right side of the adjustment diagram is a conceptual diagram of the recovery filter adaptation range on the image plane, and the gray density conceptually indicates the recovery gain. That is, the direction of the adaptive area is changed according to the adjustment direction, and the gain is changed according to the adjustment amount.

  In this example, the direction is set to four directions every 90 degrees, but various division methods such as six directions every 60 degrees and two directions every 180 degrees are conceivable. In this example, the recovery filter is adapted to a part of the screen, but various examples such as adaptation to the entire screen or to the center of the screen are conceivable.

  In Numerical Example 2, the first lens group that is positive from the object side, the second lens group that is negative, the third lens group that is positive, the fourth lens group that is negative, the fifth lens group that is positive, and from the wide-angle end to the telephoto end During zooming, each group moves and the third group moves to the object side. In this optical system, one positive lens on the most object side in the third group is used as an adjustment lens. In this lens, a step of adjusting the third lens on the tool or adjusting the adjusting lens in a state where the third to fifth groups are incorporated can be considered.

  When adjusting the former three groups on a tool, it is possible to adjust one-sided blur caused by errors due to eccentricity or tilting of a plurality of lenses constituting the third group. When adjusting the adjustment lens with the latter 3 group to 5 group incorporated, in addition to the error in the 3 group, due to the relative eccentricity of the 3rd group, the 4th group and the 5th group, the manufacturing error due to the tilt One-sided blur can also be adjusted by the eccentricity of the front lens of the three groups. An optical system with improved performance can be obtained by performing image processing by applying a recovery filter to the deterioration due to coma generated by adjusting the decentering of the first lens in the three groups.

  Next, the meaning of each conditional expression will be described.

  Conditional expressions (1) to (3) are conditional expressions for providing a zoom lens suitable for downsizing and large aperture on the premise of image restoration after adjustment of manufacturing errors.

  In order to reduce the size of a zoom lens or achieve a large aperture while maintaining the same size as that of a conventional zoom lens, it is necessary to increase the refractive power of each lens group constituting the zoom lens. However, since the sensitivity of aberration of each lens constituting the zoom lens increases at that time, adjustment is performed by displacing the head lens of the group that mainly forms a single blur due to a manufacturing error in a direction substantially perpendicular to the optical axis. Do.

  The condition for appropriately setting the amount of adjustment is conditional expression (1). Equation (1) is obtained by normalizing the maximum displacement amount by adjustment with the focal length of the entire group including the adjustment lens. If the maximum displacement amount over the adjustment amount exceeds the upper limit value of Equation (1), Since the aberration deterioration due to the adjustment becomes large, the residual aberration exceeds the allowable amount. If the maximum displacement amount applied to the adjustment amount is too small beyond the lower limit of equation (1), it is difficult to sufficiently correct aberration due to manufacturing error, and residual aberration due to manufacturing error exceeds the allowable amount, which is not good.

  Equations (2) and (3) are conditions for appropriately setting the remaining coma aberration that becomes asymmetric after correction by adjustment and enabling effective recovery processing. Equation (2) is obtained by normalizing coma aberration at an image height of 70% with a pixel pitch. If the upper limit of equation (2) is exceeded and the coma of n percent of the image height with respect to the pixel pitch becomes too large, the MTF will deteriorate significantly in the high frequency region, making it difficult to obtain the effect of the recovery filter. In order to reduce the coma aberration at the image height n% beyond the lower limit of equation (2), it is difficult to achieve a compact optical system due to the increase in the number of lenses and the lens diameter due to the large aperture. come.

  Equation (3) relates to the ratio of coma at 70% image height to 70% of effective light flux and coma at −70%. If the coma aberration at −70% is too small beyond the upper limit of the expression (3), in order to reduce the coma aberration, the number of lenses and the lens diameter are increased to achieve a compact optical system. It becomes difficult. Since it is an absolute value, the value of equation (3) is always greater than or equal to the lower limit value 0.

In order to bring the object of the present invention closer to the best, it is better to satisfy the following conditions.
5 <Iy / fa x 10000 <30 (1)
0.4 <| (Δwyu7 + Δwyl7) | / 2p <8.0 (2)
0.03 <| (Δwyu7 + Δwyl7n) / (Δwyu-7 + Δwyl-7) | <3.0 (3)

[Numerical Example 1]
Unit mm

Surface data surface number rd nd vd
1 105.495 0.50 1.91082 35.3
2 13.534 2.54
3 * -32.614 0.40 1.81000 41.0
4 * 382.536 0.29
5 15.186 1.68 2.00272 19.3
6 31.579 (variable)
7 * 7.246 2.09 1.58313 59.5
8 * -897.226 0.20
9 9.992 2.19 1.77250 49.6
10 -17.051 0.40 1.90366 31.3
11 7.319 0.89
12 -58.768 1.64 1.55332 71.7
13 * -11.359 (variable)
14 (Aperture) ∞ (Variable)
15 -20.186 1.47 2.00330 28.3
16 -9.642 0.75
17 * -6.874 0.30 1.81000 41.0
18 -24.709 (variable)
Image plane ∞

Aspheric data 3rd surface
K = 0.00000e + 000 A 4 = 1.60013e-004 A 6 = -4.54658e-007

4th page
K = 0.00000e + 000 A 4 = 2.22568e-004

7th page
K = 0.00000e + 000 A 4 = 1.61956e-005 A 6 = 2.10 100e-006

8th page
K = 5.16750e + 004 A 4 = 3.66194e-004 A 6 = -5.87897e-007

Side 13
K = 1.88643e + 000 A 4 = 4.34848e-004 A 6 = 3.12838e-005

17th page
K = 3.17908e-001 A 4 = 2.96339e-004 A 6 = 5.98863e-006 A 8 = 2.33686e-007

Various data Zoom ratio 2.85
Wide angle Medium Telephoto focal length 10.56 20.45 30.13
F number 2.88 4.22 5.55
Angle of view 32.47 21.36 14.87
Image height 6.72 8.00 8.00
Total lens length 42.93 37.35 39.50
BF 7.71 13.89 20.24

d 6 16.05 4.37 0.43
d13 0.50 0.50 0.50
d14 3.34 3.25 2.99
d18 7.71 13.89 20.24

Zoom lens group data group Start surface Focal length
1 1 -20.45
2 7 12.09
3 14 ∞
4 15 -38.46

[Numerical Example 2]

Unit mm

Surface data surface number rd nd vd
1 29.194 1.00 1.85478 24.8
2 22.456 4.62 1.69680 55.5
3 159.397 (variable)
4 47.728 0.80 1.88300 40.8
5 8.276 5.22
6 -26.153 0.80 1.60311 60.6
7 21.283 0.30
8 17.287 1.87 1.95906 17.5
9 65.570 (variable)
10 (Aperture) ∞ (Variable)
11 * 14.356 3.08 1.76802 49.2
12 * -34.617 0.80
13 -20.971 0.70 1.64769 33.8
14 -97.299 1.64 1.88300 40.8
15 -19.654 1.11
16 27.687 0.70 1.92286 18.9
17 8.581 4.21 1.49700 81.5
18 -15.335 (variable)
19 10.726 1.20 2.00272 19.3
20 18.520 0.39
21 174.532 0.60 1.77250 49.6
22 6.659 (variable)
23 * 19.229 1.77 1.85 135 40.1
24 -313.167 (variable)
25 ∞ 0.60 1.51633 64.1
26 ∞ (variable)
Image plane ∞

Aspheric data 11th surface
K = -4.84236e-001 A 4 = -4.94791e-005 A 6 = 3.16581e-008

12th page
K = 2.13838e + 000 A 4 = 1.06182e-004

23rd page
K = 0.00000e + 000 A 4 = 5.74439e-005 A 6 = 1.58141e-006

Various data Zoom ratio 3.43
Wide angle Medium telephoto focal length 6.15 16.85 21.08
F number 1.85 2.06 2.06
Angle of view 37.08 15.42 12.43
Image height 4.65 4.65 4.65
Total lens length 60.92 61.89 63.48
BF 3.96 3.96 3.96

d 3 0.35 12.07 14.35
d 9 16.98 4.93 2.05
d10 3.83 0.72 1.50
d18 0.50 3.49 4.10
d22 4.49 5.90 6.69
d24 1.82 1.82 1.82
d26 1.74 1.74 1.74

Zoom lens group data group Start surface Focal length
1 1 54.59
2 4 -9.91
3 10 ∞
4 11 11.60
5 19 -16.87
6 23 21.33
7 25 ∞
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a sectional view of Example 1 according to the embodiment of the present invention.

[Example 1]
Hereinafter, with reference to FIGS. 1-2, the structure of the 1st-3rd Example in this invention is demonstrated. A), B), and C) indicate the wide-angle end, the middle, and the telephoto end, respectively. Numerical Example The first group has a locus convex toward the image side during zooming from the wide-angle end to the telephoto end, and corrects image plane variation due to zooming. The second group moves to the object side and is responsible for the main scaling. The third group draws a locus close to the second group, but the image plane variation in the intermediate region is corrected by changing the air distance from the second group.

  By moving the third lens group toward the image side, focusing operation on a short-distance object is performed. The first lens group includes three lenses, a negative meniscus lens having a convex surface from the object side, a biconcave negative lens, and a positive meniscus lens having a convex surface on the object side. The second lens group includes four lenses: a positive lens having a strong object-side convex surface, a cemented lens in which a positive lens and a negative lens are cemented, and a positive lens having a strong image-side convex surface. The third lens group is composed of a positive meniscus lens having a convex surface on the image side and a negative meniscus lens having a convex surface on the image side.

  Camera shake correction is performed by displacing the entire second lens unit in a direction substantially perpendicular to the optical axis. The manufacturing error is adjusted by displacing one positive lens closest to the object in the second group in a direction substantially perpendicular to the optical axis. In Numerical Example 2, the first lens unit is composed of a positive first group, a negative second group, a positive third group, a negative fourth group, and a positive fifth group from the object side. During zooming from the wide-angle end to the telephoto end, the first lens unit moves to the minute image side and then moves to the object side. The second group moves to the image side, and the third group and the fourth group move to the object side.

  The diaphragm is arranged between the second group and the third group, and moves so that the air gap between the diaphragm and the third group decreases during zooming. The air gap between the third group and the fourth group moves so as to increase. The fifth group moves in a minute amount nonlinearly. In Numerical Example 2, the first group is composed of two lenses, a negative lens and a positive lens. The second group has a three-lens configuration including a negative meniscus lens having a convex surface on the object side, a biconcave negative lens, and a positive meniscus lens having a convex surface on the object side.

  The third group is a biconvex positive lens, and a cemented lens of a negative lens having a concave surface on the object side and a positive lens. The object side has a five-lens configuration including a negative lens having a convex surface and a biconvex positive lens. The fourth group has a two-lens configuration including a positive lens having a convex surface on the object side and a negative lens having a concave surface on the image side. The fifth group is a single lens configuration of a positive lens having a convex surface on the object side. It has an anti-vibration mechanism that corrects camera shake by shifting the entire third lens unit in a direction perpendicular to the optical axis. Focusing is performed by moving the fourth group toward the object side or the fifth group. Optical adjustment is performed by displacing the lens on the most object side in the third group in a direction substantially perpendicular to the optical axis.

  In the second embodiment, the focusing is performed by the fourth group or the fifth group, but may be performed by a part of the first group, the second group, or the third group.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  The present invention relates to an imaging apparatus equipped with a lens suitable for miniaturization on the premise of image restoration after adjustment of manufacturing errors.

d d line, g g line, △ M meridional image plane

Claims (13)

A zoom lens, an image sensor, and an image processing unit are used to control the image using an image restoration filter that has a filter value having a two-dimensional distribution based on aberration information of the zoom lens. In an imaging apparatus characterized by performing an image restoration process by performing a volume process,
The zoom lens adjusts in a direction to reduce one-sided blur due to manufacturing error by decentering a part of a specific lens group from the optical axis in a specific zoom state in the manufacturing process of the lens, and recovers coma aberration remaining after adjustment The image restoration filter is adapted, and the restoration filter has means for storing a plurality of types and means for measuring a displacement amount due to adjustment of the adjustment lens in the adjustment step, and classifies the displacement amount and corresponds to the classification An imaging device manufactured by adapting a recovery filter. A zoom lens, an image sensor, and an image processing unit are used to control the image using an image restoration filter that has a filter value having a two-dimensional distribution based on aberration information of the zoom lens. In an imaging apparatus characterized by performing an image restoration process by performing a volume process,
The zoom lens adjusts in a direction to reduce one-sided blur due to manufacturing error by decentering a part of a specific lens group from the optical axis in a specific zoom state in the manufacturing process of the lens, and recovers coma aberration remaining after adjustment The image restoration filter is adapted.
An imaging device comprising: means for measuring a displacement amount due to adjustment of an adjustment lens in the adjustment step; and classifying the displacement amount, and determining and adapting a recovery gain of a recovery filter corresponding to the classification. apparatus.   The imaging apparatus according to claim 1, wherein the adjustment lens selects a recovery filter that classifies and adapts the displacement direction as well as the displacement amount.   The imaging apparatus according to claim 1, wherein the aberration to be restored is coma aberration and chromatic coma aberration, and is performed in a wide-angle region or a specific region in the telephoto region. The zoom lens mounted in the imaging device is composed of a negative first lens group, a positive second lens group and a subsequent lens group from the object side,
The second lens group includes at least three positive lenses and is manufactured through a manufacturing process in which assembly adjustment is performed by displacing a positive lens disposed closest to the object side in a direction perpendicular to the optical axis. The imaging device according to any one of claims 1 to 4. The zoom lens mounted in the imaging apparatus is composed of a positive first lens group, a negative second lens group, a positive third lens group, and a subsequent lens group from the object side.
The third lens group includes at least three positive lenses and is manufactured through a manufacturing process in which assembly adjustment is performed by displacing a positive lens disposed closest to the object side in a direction perpendicular to the optical axis. The imaging device according to any one of claims 1 to 4. The zoom lens mounted in the imaging device is composed of a first lens group and a subsequent lens group from the object side,
A manufacturing process in which one of the subsequent lens groups is composed of at least one lens, and assembly adjustment is performed by displacing a positive lens arranged closest to the object side in the direction perpendicular to the optical axis. The imaging apparatus according to any one of claims 1 to 4, wherein the imaging apparatus is manufactured through a process. In the lens system, the first lens group has a negative first lens group, a positive second lens group, and a negative third lens group from the object side, and the first group has a convex locus toward the image side during zooming from the wide angle end to the telephoto end. Corrects image plane fluctuations due to magnification change.
The second group moves to the object side and is responsible for the main scaling.
The third group draws a trajectory close to the second group, but corrects the image fluctuation in the intermediate area by changing the air distance from the second group.
6. The imaging apparatus equipped with a zoom lens according to claim 5, wherein a focusing operation is performed on a short-distance object by retracting the third group toward the image side. The first lens group positive from the object side in the lens system The second lens group negative, the third lens group positive, the fourth lens group negative, the fifth lens group positive, and zooming from the wide-angle end to the telephoto end Each group moves and the third group moves to the object side,
7. The image pickup apparatus equipped with a zoom lens according to claim 6, wherein a focusing operation for a short-distance object is performed by extending the fourth group or the fifth group toward the object side. When the focal length of the entire lens group to be adjusted in the lens system is fa, and the maximum displacement amount when adjusting by adjusting the lens closest to the object side of the lens group to be adjusted in the direction perpendicular to the optical axis is Iy, The imaging apparatus according to claim 1, wherein the conditional expression is satisfied.
0.3 <Iy / fa × 10000 <50 (1) An image restoration process is performed by performing a convolution process on the image using an image restoration filter created so that a filter value has a two-dimensional distribution based on aberration information of the zoom lens. The aberration of the zoom specific region to which the image restoration filter is applied when the adjustment lens is displaced by 0.01 × fa in the direction perpendicular to the optical axis satisfies the following numerical range. The imaging device according to any one of claims 1 to 9.
0.35 <| (Δwyu7 + Δwyl7) | / 2p <16.0 (2)
0.00 <| (Δwyu7 + Δwyl7n) / (Δwyu-7 + Δwyl-7) | <3.5 (3)
fa: Focal length ΔWyu7 of the entire lens group including the adjusting lens: d-line lateral aberration amount of the upper line (70% of the effective luminous flux) at the image height of 70%
ΔWyl7: d-line lateral aberration amount at 70% of image height underline (70% of effective luminous flux)
ΔWyu-7: The amount of lateral aberration of the d-line of the upper line (70% of the effective luminous flux) at the image height of -70%
ΔWyl-7: d-line lateral aberration amount underlined at 70% image height (70% of effective luminous flux)
P: Pixel pitch   9. The imaging apparatus according to claim 1, wherein the filter area is an asymmetric area from a center portion to a peripheral portion of the screen.   The image pickup apparatus according to claim 1, wherein the filter is adapted from a center part to a peripheral part area in a telephoto range.