JP2011028166A - Optical device, imaging apparatus using the same, and imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve an effective image recovery process by providing an optical device having a property matching the image recovery process, an imaging apparatus using the optical device, and an imaging system. <P>SOLUTION: The optical device forms an image of an object onto an imaging element, performs the image recovery process to the image obtained by the imaging element, and has MTF satisfying the following conditional expression (1): 0.1≤La/Lb≤1, 10<a<30, 5<b<20 (1), where, La: MTF width at a% of MTF, Lb: MTF width at b% of MTF. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical device used for a digital camera or the like, an imaging device using the optical device, or an imaging system including an imaging device and an external device, and is particularly executed for a captured image. And an optical system suitable for image restoration processing.

  2. Description of the Related Art Conventionally, various imaging devices are known that project an image of a subject condensed through an optical system onto an imaging element such as a CCD. In such an imaging apparatus, it is common to perform various types of image processing on an image obtained by imaging using a filter having predetermined characteristics.

  As such an imaging apparatus capable of image processing, Patent Literature 1 includes an optical system, an imaging element, a conversion unit, and a signal processing unit, and uses an first filter and a second filter. Is disclosed. The optical system is formed so that the amount of defocusing is substantially constant at the in-focus position and the distances before and after the in-focus position. The image pickup device picks up a subject image formed by the optical system. The conversion unit corrects the focal blur in the image obtained from the image sensor and generates a restored image. The signal processing means performs predetermined image processing on the image signal. The first filter is used for the image restoration process of the conversion means in the still image shooting mode. The second filter is used for the image restoration process of the conversion means in the moving image shooting mode or when the through image is displayed.

  According to the disclosure of Patent Document 1, it is possible to perform simple image restoration processing using the second filter in the moving image shooting mode or when displaying a through image. As a result, the optical system can be simplified without the need for expensive conversion means, thereby reducing costs. It is also possible to provide an imaging device that does not degrade the restored image.

JP 2008-011492 A

  In Patent Document 1, the image is restored by correcting the focal blur in the image. However, the reconstructed image was not sufficiently resolved.

  An object of the present invention is to easily obtain an image in which a sufficient resolution is obtained in the restored image and the depth of focus is enlarged.

  In order to solve the above-described problems, an optical device of the present invention, an imaging device using the optical device, and an imaging system are any of the following.

According to a first configuration of the optical device of the present invention, an optical device that forms an image of a subject on an image sensor and performs image restoration processing on an image obtained by the image sensor, the following conditional expression (1 It is characterized by having an MTF that satisfies (1).
0.1 ≦ La / Lb ≦ 1, 10 <a <30, 5 <b <20 (1)
However,
La: MTF width when MTF is a%,
Lb: MTF width when MTF is b%,
It is.

According to a second configuration of the optical device of the present invention, in the first configuration, the MTF satisfies the following conditional expression (2).
1 ≦ MTF_H / MTF_L ≦ 2 (2)
However,
MTF_H: Maximum peak value of MTF,
MTF_L: Minimum bottom value of MTF,
It is.

A third configuration of the optical device of the present invention is characterized in that, in the first or second configuration, the MTF satisfies the following conditional expression (3).
1 ≦ MTF_H / MTF_ave ≦ 1.7 (3)
However,
MTF_H: Maximum peak value of MTF,
MTF_ave: average value of MTF within La range,
It is.

According to a fourth configuration of the optical device of the present invention, in any one of the first to third configurations, the MTF satisfies the following conditional expression (4).
0.2 ≦ La / Lc ≦ 1.2 (4)
However,
Lc: half width of MTF.

A first configuration of an imaging apparatus according to the present invention includes an imaging device, an optical system that forms an image of a subject on the imaging device, and an image processing unit that performs image processing on an image obtained by the imaging device. And the optical system has an MTF that satisfies the following conditional expression (1).
0.1 ≦ La / Lb ≦ 1, 10 <a <30, 5 <b <20 (1)
However,
La: MTF width when MTF is a%,
Lb: MTF width when MTF is b%,
It is.

The second configuration of the imaging apparatus of the present invention is characterized in that, in the first configuration, the MTF satisfies the following conditional expression (2).
1 ≦ MTF_H / MTF_L ≦ 2 (2)
However,
MTF_H: Maximum peak value of MTF,
MTF_L: Minimum bottom value of MTF,
It is.

According to a third configuration of the imaging apparatus of the present invention, in the first or second configuration, the MTF satisfies the following conditional expression (3).
1 ≦ MTF_H / MTF_ave ≦ 1.7 (3)
However,
MTF_H: Maximum peak value of MTF,
MTF_ave: average value of MTF within La range,
It is.

According to a fourth configuration of the imaging apparatus of the present invention, in any one of the first to third configurations, the MTF satisfies the following conditional expression (4).
0.2 ≦ La / Lc ≦ 1.2 (4)
However,
Lc: half width of MTF.

According to a fifth configuration of the imaging apparatus of the present invention, in the first to fourth configurations, the MTF has a spatial frequency that satisfies the conditional expression (5).
ν = 1 / (2 × P × A), 1 <A <20 (5)
However,
ν: spatial frequency,
P: Pixel pitch of the image sensor,
It is.

According to a sixth configuration of the imaging apparatus of the present invention, in the first to fourth configurations, the MTF has a spatial frequency that satisfies the conditional expression (6).
ν = 1 / (2 × P × A), 2 <A <8 (6)
However,
ν: spatial frequency,
P: Pixel pitch of the image sensor,
It is.

According to a seventh configuration of the imaging apparatus of the present invention, in the first to fourth configurations, the MTF has a spatial frequency that satisfies the conditional expression (7).
0.001 <ν / N <3 (7)
However,
ν: spatial frequency,
N: the number of pixels on one side of the image sensor,
It is.

  In addition, it is more preferable that the first to seventh configurations of the imaging apparatus simultaneously satisfy any of the configurations described below.

  According to an eighth configuration of the imaging apparatus of the present invention, in any one of the first to seventh imaging apparatuses, the MTF satisfies each conditional expression at an open F number.

  According to a ninth configuration of the imaging apparatus of the present invention, in any one of the first to eighth imaging apparatuses, the MTF intersects with MTFs of other spatial frequencies in a range where the contrast does not become zero. Is.

  According to a tenth configuration of the imaging apparatus of the present invention, in the ninth imaging apparatus, the MTF intersects with an MTF of another spatial frequency at a position of 10% or less.

According to an eleventh configuration of the imaging apparatus of the present invention, in any of the first to tenth imaging apparatuses, the spherical aberration characteristic of the optical system has a peak.

  According to a twelfth configuration of the imaging apparatus of the present invention, in the eleventh imaging apparatus, the spherical aberration characteristic of the optical system has two or more peaks.

  According to a thirteenth configuration of the imaging apparatus of the present invention, in the twelfth imaging apparatus, the spherical aberration characteristic peaks are located on the plus side and the minus side.

  According to a fourteenth configuration of the imaging device of the present invention, in the first to thirteenth imaging devices, the optical system includes a wavefront control element for realizing the MTF.

  According to a fifteenth configuration of the imaging apparatus of the present invention, in the fourteenth imaging apparatus, the wavefront control element for realizing the MTF has an aspherical surface.

  According to a sixteenth configuration of the imaging apparatus of the present invention, in the fourteenth imaging apparatus, the wavefront control element for realizing the MTF is a phase plate.

  According to a seventeenth configuration of the imaging device of the present invention, in the fourteenth imaging device, the wavefront control element for realizing the MTF is a lens having a plurality of curvatures on one surface. .

  According to an eighteenth configuration of the imaging apparatus of the present invention, in the fourteenth imaging apparatus, the wavefront control element for realizing the MTF is a lens having different curvatures at the center and the periphery. .

  According to a nineteenth configuration of the imaging apparatus of the present invention, in the seventeenth or eighteenth imaging apparatus, the wavefront control element for realizing the MTF is a lens having three curvatures on one surface. Is.

  According to a twentieth configuration of the imaging apparatus of the present invention, in any one of the fourteenth to nineteenth imaging apparatuses, a birefringent crystal is used as a material of a wavefront control element for realizing the MTF. It is what.

  A twenty-first configuration of the imaging device of the present invention is characterized in that, in any one of the fourteenth to twentieth imaging devices, the wavefront control element for realizing the MTF is detachable. .

  According to a twenty-second configuration of the imaging apparatus of the present invention, in any one of the first to twenty-first imaging apparatuses, the image processing executed in the image processing means is an image restoration process for an image obtained by the imaging element. It is characterized by including.

  According to a twenty-third configuration of the imaging apparatus of the present invention, in the twenty-second imaging apparatus, the image restoration process uses an imaging characteristic of the optical system.

According to a twenty-fourth configuration of the imaging apparatus of the present invention, in the twenty-third imaging apparatus, the image restoration process executes a process in which the restored image is represented by the following differential equation.
f (x, y) = g (x, y) + a ₁ (x, y) · g ′ (x, y) +
... + a _n (x, y) · g ⁽ⁿ⁾ (x, y)
However,
f: the restored image, g: the image, a ₁ , a ₂ ,... a _n : deterioration parameter,
g ⁽ⁿ⁾ : nth-order derivative with respect to the image,
It is.

  The configuration of the first imaging system of the present invention includes any one of the first to twenty-fourth imaging devices and an external device that executes an image restoration process on an image obtained by the imaging device. It is what.

  The configuration of the second imaging system of the present invention is characterized in that, in the first imaging system, the image restoration processing uses an imaging characteristic of the optical system.

The configuration of the third imaging system of the present invention is characterized in that, in the first or second imaging system, the image restoration process executes a process in which the restored image is represented by the following differential equation. .
f (x, y) = g (x, y) + a ₁ (x, y) · g ′ (x, y) +
... + a _n (x, y) · g ⁽ⁿ⁾ (x, y)
However,
f: the restored image, g: the image, a ₁ , a ₂ ,... a _n : deterioration parameter,
g ⁽ⁿ⁾ : nth-order derivative with respect to the image,
It is.

  According to a fourth imaging system of the present invention, the imaging device and the external device each include a communication unit, and an image obtained by the imaging element is transmitted to the external device via the communication unit. It is what.

  According to the present invention, sufficient resolution can be obtained in the restored image. In addition, it is possible to easily obtain an image with an increased focal depth.

The figure for demonstrating various parameters in the MTF characteristic of this invention. Sectional drawing which developed the optical system of the comparative example 1 and Examples 1-3 of this invention along the optical axis. The figure which shows the MTF characteristic of the comparative example 1. FIG. 6 is a diagram showing spherical aberration characteristics of Comparative Example 1. FIG. 6 is a diagram showing MTF characteristics of the optical system according to Example 1 of the present invention. FIG. 6 is a diagram showing spherical aberration characteristics of Example 1 of the present invention. FIG. 6 is a schematic diagram showing the configuration of a bifocal lens used in Example 2 of the present invention. FIG. 6 is a diagram showing MTF characteristics of an optical system according to Example 2 of the present invention. FIG. 6 is a diagram showing spherical aberration characteristics of Example 2 of the present invention. FIG. 6 is a schematic diagram showing the configuration of a bifocal lens used in Example 3 of the present invention. FIG. 6 is a diagram showing MTF characteristics of an optical system according to Example 3 of the present invention. FIG. 6 is a diagram showing spherical aberration characteristics of Example 4 of the present invention. FIG. 6 is a schematic diagram showing the configuration of a trifocal lens used in Example 4 of the present invention. FIG. 6 is a diagram showing MTF characteristics of an optical system according to Example 4 of the present invention. FIG. 6 is a diagram showing spherical aberration characteristics of Example 4 of the present invention. Sectional drawing which developed the optical system of the comparative example 2 and taken along the optical axis. The figure which shows the MTF characteristic of the comparative example 2. FIG. 6 is a diagram showing spherical aberration characteristics of Comparative Example 2. Sectional drawing which developed the optical system of Example 4 of this invention and took along the optical axis. FIG. 6 is a diagram showing MTF characteristics of an optical system according to Example 4 of the present invention. FIG. 6 is a diagram showing spherical aberration characteristics of Example 4 of the present invention. 1 is a schematic diagram illustrating a configuration of an imaging apparatus according to the present invention. Schematic which shows the image restoration process of this invention. Schematic which shows the structure of the imaging system of this invention.

The first configuration of the optical device according to the present embodiment is an optical device that forms an image of a subject on an image sensor and performs image restoration processing on an image obtained by the image sensor. It has MTF which satisfies 1).
0.1 ≦ La / Lb ≦ 1, 10 <a <30, 5 <b <20 (1)
However,
La: MTF width when MTF is a%,
Lb: MTF width when MTF is b%,
It is.

  Below, the reason and effect | action which employ | adopt the 1st structure of this optical apparatus are demonstrated.

  In an optical device, an image of a subject is formed by an optical system. At this time, the position of the formed image varies depending on the position of the subject. When the positions of the plurality of subjects are different, the positions of the images of the subjects are also different. Here, it is assumed that the subject is focused on a certain subject. In this case, images of other subjects are formed before and after the subject image position (hereinafter referred to as a reference image position). An in-focus subject image is obtained at the reference image position, but the subject image is out of focus (blurred) before and after the reference image position.

  The first configuration defines that the shape of the MTF characteristic is constant or substantially constant. Note that MTF stands for Modulation Transfer Function. FIG. 1 is a schematic diagram for explaining various parameters in the MTF characteristic of the optical device of the present embodiment, more specifically, the optical system. This figure shows the MTF characteristics that take the MTF value with respect to the defocus amount, that is, the distance in the direction along the optical axis (horizontal axis in the figure). The MTF width referred to in the present embodiment refers to the distance between the extreme ends of the MTF characteristics, and even when the MTF characteristics intersect in the middle between the extreme ends, the intersection is not considered. As shown in this figure, the MTF width is La when the MTF is a%, and the MTF width is Lb when the MTF is b%.

  By satisfying conditional expression (1), the shape of the MTF characteristic can be made constant or substantially constant. In this case, the image characteristics (image quality, degree of blur, etc.) can be made substantially the same for the images obtained at the reference position and its neighboring positions. Therefore, when image restoration processing is performed on this image, image restoration can be performed effectively.

  Specifically, for example, when a recovery process for increasing the MTF characteristic is performed, the MTF can be recovered in the same manner in each pixel of the image. That is, the resolution can be sufficiently improved for each pixel constituting the image. As a result, a fully resolved image can be recovered. Further, it can be restored as an image with a wide focal depth. Note that the substantially constant MTF is a range (variation range) in which image recovery is performed in the same way for many pixels (for example, sufficient resolution can be obtained) when image recovery processing is executed. Say.

  On the other hand, if the above condition is not satisfied, the difference (variation width) in MTF at a predetermined position before and after the installation position of the image sensor increases. In this case, even if the image restoration process is executed, an image in which a change in resolution is conspicuous is obtained.

The second configuration of the optical device according to the present embodiment is characterized in that, in the first configuration, the MTF satisfies the following conditional expression (2).
1 ≦ MTF_H / MTF_L ≦ 2 (2)
However,
MTF_H: Maximum peak value of MTF,
MTF_L: Minimum bottom value of MTF,
It is.

Below, the reason and effect | action which employ | adopt the 2nd structure of this optical apparatus are demonstrated. In the second configuration of the optical device, the upper limit of the ratio of the maximum peak value MTF_H of the MTF to the minimum bottom value MTF_L of the MTF is set to 2 and the lower limit is set to 1, so that the shape of the MTF characteristic is constant or substantially constant. It is stipulated. Here, the peak value of the MTF is a value when the MTF changes from rising to falling, and corresponds to the maximum value of the MTF characteristic. On the other hand, the bottom value of the MTF refers to a value when the MTF turns from rising to rising. FIG. 1 shows the maximum peak values MTF_H and MTF_L in a schematic diagram of the MTF characteristics.

In the second configuration, in particular, the upper limit is set in the ratio of the maximum peak value MTF_H of the MTF to the minimum bottom value MTF_L of the MTF, so that the change of the MTF with respect to the defocus amount can be suppressed. Thereby, the shape of the MTF characteristic becomes substantially constant. According to such an optical apparatus, the image restoration process can be effectively performed. That is, a sufficiently resolved image can be restored.

  On the other hand, if the above condition is not satisfied, the difference (variation width) in MTF at a predetermined position before and after the installation position of the image sensor increases. In this case, even if the image restoration process is executed, an image in which a change in resolution is conspicuous is obtained.

The third configuration of the optical device of the present embodiment is characterized in that, in the first or second configuration, the MTF satisfies the following conditional expression (3).
1 ≦ MTF_H / MTF_ave ≦ 1.7 (3)
However,
MTF_H: Maximum peak value of MTF,
MTF_ave: average value of MTF within La range,
It is.

Below, the reason and effect | action which employ | adopt the 3rd structure of this optical apparatus are demonstrated. The third configuration of the optical device is based on the MTF average value MTF_ave within the range of the MTF width La.
By setting the upper limit of the ratio of the maximum peak value MTF_H of MTF to 1.7 and the lower limit to 1, it is defined that the shape of the MTF characteristic is constant or substantially constant.

  When the above conditions are not satisfied, the difference (variation width) in MTF at a predetermined position before and after the installation position of the image sensor increases. In this case, even if the image restoration process is executed, an image in which a change in resolution is conspicuous is obtained.

According to a fourth configuration of the optical device of the present embodiment, in any one of the first to third configurations, the MTF satisfies the following conditional expression (4).
0.2 ≦ La / Lc ≦ 1.2 (4)
However,
Lc: half width of MTF.

Below, the reason and effect | action which employ | adopt the 4th structure of this optical apparatus are demonstrated. In the fourth configuration of the optical device, the upper limit of the ratio of the maximum peak value MTF_H of the MTF to the half width Lc of the MTF is set to 1.2, and the lower limit is set to 0.2. It stipulates that it is constant. Here, the half-value width Lc of the MTF means the MTF width at the MTF value that is half of the maximum peak value (maximum value) of the MTF.

  When the above conditions are not satisfied, the difference (variation width) in MTF at a predetermined position before and after the installation position of the image sensor increases. In this case, even if the image restoration process is executed, an image in which a change in resolution is conspicuous is obtained.

  Moreover, in this 4th structure, it is preferable to satisfy the conditions in case a lower limit is 0.2. In this way, more preferable MTF characteristics can be obtained.

The first configuration of the imaging apparatus according to the present embodiment includes an imaging device, an optical system that forms an image of a subject on the imaging device, and an image processing unit that performs image processing on an image obtained by the imaging device. And the optical system has an MTF that satisfies the following conditional expression (1).
0.1 ≦ La / Lb ≦ 1, 10 <a <30, 5 <b <20 (1)
However,
La: MTF width when MTF is a%,
Lb: MTF width when MTF is b%,
It is.

The second configuration of the imaging apparatus of the present embodiment is characterized in that, in the first configuration, the MTF satisfies the following conditional expression (2).
1 ≦ MTF_H / MTF_L ≦ 2 (2)
However,
MTF_H: Maximum peak value of MTF,
MTF_L: Minimum bottom value of MTF,
It is.

The third configuration of the imaging apparatus according to the present embodiment is characterized in that, in the first or second configuration, the MTF satisfies the following conditional expression (3).
1 ≦ MTF_H / MTF_ave ≦ 1.7 (3)
However,
MTF_H: Maximum peak value of MTF,
MTF_ave: average value of MTF within La range,
It is.

According to a fourth configuration of the imaging apparatus of the present embodiment, in any one of the first to third configurations, the MTF satisfies the following conditional expression (4).
0.2 ≦ La / Lc ≦ 1.2 (4)
However,
Lc: half width of MTF.

The imaging devices in the first to fourth configurations execute image processing on the imaging device and the image obtained by the imaging device in the first to fourth configurations of the optical device (optical system) described above, respectively. By adding an image processing means, the imaging apparatus is realized. According to the configurations of the first to fourth imaging devices, an image of a subject is formed by an optical system in which the shape of the MTF characteristic is constant or substantially constant. Then, an image of the subject (observation image) can be obtained by capturing the subject image with the image sensor. When the image restoration process is performed on this image, the image restoration process can be effectively performed. That is, it is possible to recover a sufficiently resolved image.

According to a fifth configuration of the imaging apparatus of the present embodiment, in the first to fourth configurations, the MTF has a spatial frequency that satisfies the conditional expression (5).
ν = 1 / (2 × P × A), 1 <A <20 (5)
However,
ν: spatial frequency,
P: Pixel pitch of the image sensor,
It is.

Below, the reason and effect | action which employ | adopt the 5th structure of this imaging device are demonstrated. The fifth configuration defines a spatial frequency where a substantially constant MTF exists. In the fifth configuration, the spatial frequency at which a substantially constant MTF exists is defined using the maximum spatial frequency νmax = 1 / (2 × P) and the coefficient A in the image sensor having the pixel pitch P. In the fifth configuration, in particular, the lower limit of the spatial frequency ν is defined as νmax / 20. It is a condition that there is at least one MTF that is substantially constant within the range of the spatial frequency ν at the installation position of the image sensor and a predetermined distance before and after the image sensor. By using an optical system having such conditions, it is possible to effectively perform image restoration processing. That is, a sufficiently resolved image can be recovered.

According to a sixth configuration of the imaging apparatus of the present embodiment, in the first to fourth configurations, the MTF has a spatial frequency that satisfies the conditional expression (6).
ν = 1 / (2 × P × A), 2 <A <8 (6)
However,
ν: spatial frequency,
P: Pixel pitch of the image sensor,
It is.

Below, the reason and effect | action which employ | adopt the 6th structure of this imaging device are demonstrated. Similar to the fifth configuration, the sixth configuration defines a spatial frequency in which a substantially constant MTF exists, and the spatial frequency range is narrower than that of the fifth configuration, so that an even better image restoration process is performed. It is possible to do. Specifically, when the maximum spatial frequency is νmax, the upper limit of the spatial frequency is νmax / 2 and the lower limit is νmax / 8. By satisfying this condition, the image restoration process can be performed more effectively. That is, a more resolved image can be recovered.

According to a seventh configuration of the imaging apparatus of the present embodiment, in the first to fourth configurations, the MTF has a spatial frequency that satisfies the conditional expression (7).
0.001 <ν / N <3 (7)
However,
ν: spatial frequency,
N: the number of pixels on one side of the image sensor,
It is.

Below, the reason and effect | action which employ | adopts the 7th structure of this imaging device are demonstrated. The seventh configuration also defines a spatial frequency where a substantially constant MTF exists. In the fourth configuration, the upper and lower limits of the spatial frequency are defined using the number of pixels on one side of the image sensor used in the imaging apparatus. Here, in the case of a rectangular image sensor, the number of pixels on one side of the image sensor means the larger number of pixels in the vertical or horizontal pixel array. As described above, the conditional expression (7) is based on the condition that there is at least one MTF that is substantially constant within the range of the spatial frequency ν at the installation position of the image sensor and the predetermined distance before and after the image sensor. By satisfying this condition, the image restoration process can be performed effectively. That is, a sufficiently resolved image can be recovered.

  In addition, it is more preferable that the first to seventh configurations of the imaging apparatus simultaneously satisfy any of the configurations described below.

  According to an eighth configuration of the imaging apparatus of the present embodiment, in any one of the first to seventh imaging apparatuses, the MTF satisfies the above conditional expressions at the open F number.

  The eighth configuration stipulates that the optical system has a substantially constant MTF at the open F number where the depth of focus is the shallowest. When the optical system has a variable stop, it is defined that the open F number has a substantially constant MTF. In this way, a substantially constant MTF can be obtained even when the variable aperture is changed. As a result, an effective image restoration process can be realized for an image obtained by photographing at any aperture position. That is, a sufficiently resolved image can be recovered.

  According to a ninth configuration of the imaging apparatus of the present embodiment, in any one of the first to eighth imaging apparatuses, the MTF intersects with MTFs of other spatial frequencies in a range where the contrast does not become zero. To do.

  In the ninth configuration, in the MTF of the target spatial frequency, the MTF at the installation position of the imaging device and the MTF at a predetermined position before and after the MTF has a substantially constant location in relation to the MTFs of other spatial frequencies. It is guaranteed. Specifically, it is assumed that the MTF at the target spatial frequency and the MTF at another spatial frequency are overlapped. In this case, if the MTF of the target spatial frequency is substantially constant, it intersects with MTFs of other spatial frequencies as long as the contrast is not zero. Note that the contrast of 0 corresponds to a position where the black and white are reversed in the MTF of the spatial frequency of interest, and exactly where the MTF is 0.

  According to a tenth configuration of the imaging apparatus of the present embodiment, in the ninth imaging apparatus, the MTF intersects with an MTF of another spatial frequency at a position of 10% or less.

  The tenth configuration defines conditions that are even better in the ninth configuration. According to the tenth configuration, in the MTF having the target spatial frequency, the MTF at the installation position of the imaging device and the MTF at a predetermined position before and after the imaging element has a substantially constant location. Further assurance can be made in the relationship.

  The eleventh configuration of the imaging apparatus of the present embodiment is characterized in that, in any of the first to tenth imaging apparatuses, the spherical aberration characteristic of the optical system has a peak value.

  The eleventh configuration stipulates that the MTF at the installation position of the imaging element and the predetermined positions before and after the imaging element is substantially constant based on the spherical aberration characteristics of the optical system. When the spherical aberration characteristic has a peak value, the spherical aberration characteristic fluctuates in both the positive and negative directions. In this way, by changing the spherical aberration characteristics in both directions, it is possible to disperse the light rays in the vicinity of the installation position of the image sensor. By giving such characteristics, it is possible to form a substantially constant MTF.

  According to a twelfth configuration of the imaging apparatus of this embodiment, in the eleventh imaging apparatus, the spherical aberration characteristic of the optical system has two or more peak values.

  The twelfth configuration defines conditions that are even better in the eleventh configuration. As described above, since the spherical aberration characteristic has two or more peak values, the spherical aberration characteristic fluctuates at least twice in both the positive and negative directions. By giving such characteristics, an optical system having a substantially constant MTF can be realized.

  A thirteenth configuration of the imaging apparatus according to the present embodiment is characterized in that, in the twelfth imaging apparatus, the peak values of the spherical aberration characteristics are located on the plus side and the minus side.

  The thirteenth configuration defines conditions that are even better in the twelfth configuration. Thus, by positioning the peak value of the spherical aberration characteristic on both the plus side and the minus side, an optical system having a substantially constant MTF can be realized.

  According to a fourteenth configuration of the imaging apparatus of the present embodiment, in the first to thirteenth imaging apparatuses, the optical system includes a wavefront control element for realizing a substantially integrated MTF.

  By providing the light wavefront control element, an optical system having a substantially constant MTF can be realized.

  The fifteenth configuration of the imaging device of this embodiment is characterized in that, in the fourteenth imaging device, the wavefront control element for realizing a substantially constant MTF has an aspherical surface.

  Since the wavefront control element has an aspherical surface, an optical system having a substantially constant MTF can be realized. As the wavefront control element having an aspherical surface, an aspherical lens, an aspherical plate, or a multifocal lens having an aspherical surface in any region can be adopted.

  According to a sixteenth configuration of the imaging apparatus of the present embodiment, in the fourteenth imaging apparatus, the wavefront control element for realizing the MTF is a phase plate.

  By using the phase plate as a wavefront control element, an optical system having a substantially constant MTF can be realized.

  According to a seventeenth configuration of the imaging device of this embodiment, in the fourteenth imaging device, the wavefront control element for realizing MTF is a lens having a plurality of curvatures on one surface.

  An optical system having a substantially constant MTF can be realized by using a lens having a plurality of curvatures on one surface as a wavefront control element. One curvature includes a curvature having a predetermined radius of curvature such as a spherical shape, and a curvature obtained by a predetermined calculation formula such as an aspherical shape.

  According to an eighteenth configuration of the imaging apparatus of the present embodiment, in the fourteenth imaging apparatus, the wavefront control element for realizing the MTF is a lens having different curvatures at the center and the periphery.

  By using lenses having different curvatures at the center and the periphery as the wavefront control element, an optical system having a substantially constant MTF can be realized.

  According to a nineteenth configuration of the imaging device of this embodiment, in the seventeenth or eighteenth imaging device, the wavefront control element for realizing MTF is a lens having three curvatures on one surface. .

  An optical system having a substantially constant MTF can be realized by using a lens having three curvatures on one surface as a wavefront control element.

  According to a twentieth configuration of the imaging apparatus of this embodiment, in any one of the fourteenth to nineteenth imaging apparatuses, a wavefront control element for realizing MTF is made of a birefringent crystal as a material thereof. And

  By using a birefringent crystal as the material of the wavefront control element, an optical system having a substantially constant MTF can be realized.

  A twenty-first configuration of the imaging device of the present embodiment is characterized in that, in any one of the fourteenth to twentieth imaging devices, the wavefront control element for realizing the MTF is detachable.

  According to such a configuration, the wavefront control element can be removed from the optical system or replaced with another optical element. An optical system having a substantially constant MTF and another optical system can be realized by one apparatus, and can be changed to a desired MTF characteristic when necessary.

  According to a twenty-second configuration of the imaging apparatus of the present embodiment, in any one of the first to twenty-first imaging apparatuses, the image processing executed in the image processing means is an image restoration process for an image obtained by the imaging element. It is characterized by including.

  According to the twenty-second configuration, it is possible to perform imaging with only one imaging device and to perform image restoration processing on an image obtained by imaging.

  The twenty-third configuration of the image pickup apparatus of the present embodiment is characterized in that, in the twenty-second image pickup apparatus, the image restoration process uses the imaging characteristics of the optical system.

  According to the twenty-third configuration, more effective image recovery processing can be performed by performing image recovery processing using the imaging characteristics of the optical system.

According to a twenty-fourth configuration of the imaging apparatus of the present embodiment, in the twenty-third imaging apparatus, the image restoration process executes a process in which the restored image is represented by the following differential equation.
f (x, y) = g (x, y) + a ₁ (x, y) · g ′ (x, y) +
... + a _n (x, y) · g ⁽ⁿ⁾ (x, y)
However,
f: recovered image, g: image, a ₁ , a ₂ ,... a _n : degradation parameter,
g ⁽ⁿ⁾ : nth derivative with respect to the image,
It is.

  According to the twenty-fourth configuration, more effective image restoration processing is performed by filtering with a deterioration parameter that changes according to the position of the image, that is, a so-called space variant parameter, as the imaging characteristics of the optical system. be able to.

  The configuration of the first imaging system of the present embodiment includes any one of the first to 24th imaging devices and an external device that executes an image restoration process on an image obtained by the imaging device. And

According to the configuration of the first imaging system, it is possible to reduce the processing load in the imaging apparatus by performing the image restoration process in the external apparatus. As a result, cost reduction of the imaging device,
High-speed processing can be realized.

  The configuration of the second imaging system of the present embodiment is characterized in that in the first imaging system, the image restoration process uses the imaging characteristics of the optical system.

  According to the configuration of the second imaging system, more effective image recovery processing can be performed by performing image recovery processing using the imaging characteristics of the optical system.

The configuration of the third imaging system of the present embodiment is characterized in that, in the first or second imaging system, the image restoration process executes a process in which the restored image is represented by the following differential equation.
f (x, y) = g (x, y) + a ₁ (x, y) · g ′ (x, y) +
... + a _n (x, y) · g ⁽ⁿ⁾ (x, y)
However,
f: recovered image, g: image, a ₁ , a ₂ ,... a _n : degradation parameter,
g ⁽ⁿ⁾ : nth derivative with respect to the image,
It is.

  According to the third configuration of the imaging system, it is possible to perform filtering with a deterioration parameter that changes according to the position of the image, a so-called space variant parameter, as the imaging characteristics of the optical system. Thereby, more effective image restoration processing can be performed.

  The configuration of the fourth imaging system of the present embodiment is characterized in that the imaging device and the external device each include a communication unit, and an image obtained by the imaging device is transmitted to the external device via the communication unit. .

  According to the configuration of the fourth imaging system, an image obtained by the imaging device can be easily provided to an external device. In addition, it is possible to reduce the recording capacity and processing amount in the imaging apparatus.

  The optical system used in the imaging apparatus according to the present embodiment will be described with reference to FIGS.

  FIG. 2 is a cross-sectional view taken along the optical axis by developing an outline of the optical system used in Comparative Example 1 and Examples 1 to 4 of the present invention. Comparative Example 1 and Examples 1 to 4 differ in the details of the third lens L3 in the drawing.

  The comparative example 1 is illustrated for explaining the first to fourth embodiments, and both surfaces of the third lens L3 are spherical. In contrast, in Example 1, the six surfaces of the third lens L3 are aspherical, in Examples 2 and 3, the five surfaces of the third lens L3 are bifocal lenses, and in Example 4, the third lens L3 is used. Are different in that the five surfaces are trifocal lenses.

  In Comparative Example 1, the optical system O shown in FIG. 2 includes a first lens L1, a second lens L2, a third lens L3, and an aperture stop S in order from the object side to the emission side. In the drawing, an imaging element such as a CCD is installed on the imaging surface indicated by r8.

  The first lens L1 is a positive meniscus single lens having a convex surface facing the object side, the second lens L2 is a biconcave single lens having negative refractive power, and the third lens L3 is positively refracted. It is a biconvex single lens having force.

  In this comparative example, the imaging device installed on the imaging surface is designed assuming that the maximum number of pixels in the vertical or horizontal direction is 4000 and the pixel pitch is 1.7 (μm). This also applies to the embodiments.

  The numerical data of the comparative example 1 is shown below. In the numerical data, r is a radius of curvature of each lens surface (optical surface), d is a distance between each lens surface (optical surface), nd is a refractive index of d-line of each lens (optical medium), and Vd is each lens ( The Abbe number of the optical medium), F is the focal length. Note that the symbol “∞” written in the radius of curvature indicates infinite.

  Various data indicate the focal length and F number of the optical system. The unit of the focal length is millimeter (mm), and the F number is shown in the open state used for this measurement.

  The depth characteristic indicates the width of each MTF when the MTF is 20% and 10% at an evaluation spatial frequency of 84 (lp / mm), and the unit is millimeter (mm).

Numerical comparison example 1
Unit mm
Surface data surface number r d nd Vd F
1 3.0139 1.2800 1.72341 50.20 6.1743
2 7.6146 0.1923
3 -10.5848 0.2367 1.70448 30.10 -3.5085
4 3.2544 0.3997
5 10.7443 0.4438 1.81067 41.00 5.0931
6 -6.5817 0.2367
7 (Aperture) ∞ 7.7389
8 (imaging surface) ∞

Various data focal length 9.9902
F number 3.5

Depth characteristics (Evaluation spatial frequency: 84 [lp / mm])
Depth MTF 20% 0.09
MTF 10% 0.11.

  FIG. 3 is a diagram showing the MTF characteristic at the evaluation spatial frequency 84 (lp / mm) in Comparative Example 1. FIG. 2 shows the MTF (unit:%) with respect to the defocus amount (unit: millimeter (mm)) on the axis. The MTF characteristic of Comparative Example 1 has a shape having a sharp peak of about 70% near −0.05 (mm) with respect to the reference position. FIG. 4 is a diagram showing the spherical aberration characteristic in the comparative example 1. Here, the spherical aberration characteristic at a wavelength of 546.07 (nm) is shown.

  Next, numerical examples and various characteristics of the first embodiment will be described below. In the first embodiment, the six surfaces of the third lens L3 in FIG. 2 are aspherical, thereby realizing a substantially constant MTF at the installation position of the imaging element and a predetermined distance before and after the installation position. The meaning of each numerical value and various design conditions are the same as those described in Comparative Example 1. In the surface data, an asterisk “*” attached to the right side of the surface number indicates that the lens surface is aspherical.

  The comparative example described in the depth characteristics shows the ratio of the width of each MTF at 20% and 10% of MTF with respect to Comparative Example 1. Further, the converted F number indicates the F number required when the width of the MTF of the first embodiment is realized in the first comparative example.

  The aspherical shape is expressed by the following equation, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis.

x = (y ² / r) / [1+ {1- (K + 1) (y / r) ² } ^1/2 ]
+ A2y ² + A4y ⁴ + A6y ⁶ + A8y ⁸ + A10y ¹⁰ +
Here, r is a paraxial radius of curvature, K is a conical coefficient, and A2 to A10 are secondary to 10th order aspherical coefficients, respectively. The symbol “E” indicates that the subsequent numerical value is a power exponent with 10 as the base. For example, “1.0E-5” means “1.0 × 10 ⁻⁵ ”.

Numerical example 1
Unit mm
Surface data surface number r d nd Vd F
1 3.0139 1.2800 1.72341 50.20 6.1743
2 7.6146 0.1923
3 -10.5848 0.2367 1.70448 30.10 -3.5085
4 3.2544 0.3997
5 10.7443 0.4438 1.81067 41.00 5.0931
6 * -6.5817 0.2367
7 (Aperture) ∞ 7.7389
8 (imaging surface) ∞

Aspheric data 6th surface
K = 0
A2 = -2.01E-12
A4 = 5.98E-03
A6 = -2.08E-02
A8 = 2.19E-02
A10 = -7.06E-03

Various data focal length 9.9902
F number 3.5

Depth characteristics (Evaluation spatial frequency: 84 [lp / mm])
Depth vs. comparative example [%] Converted F number MTF 20% 0.16 182 6.4
MTF 10% 0.25 223 7.8.

  FIG. 5 is a diagram showing the MTF characteristics in Example 1, and FIG. 5A shows the MTF characteristics on the axis. FIG. 5B shows the off-axis MTF characteristics. Here, MTF characteristics in two off-axis directions are shown, 0.25d and 0.35d (where 0.5d is the maximum imaging surface height). 5A and 5B, the evaluation spatial frequency is 84 (lp / mm).

  FIG. 5C shows MTF characteristics when the evaluation spatial frequencies are different. Here, the same 84 (lp / mm) MTF characteristics as in FIG. 5A and 50 (lp / mm) two MTF characteristics are shown.

  As described above, the MTF characteristics on the axis shown in FIG. 5A are compared with the MTF characteristics of Comparative Example 1 in FIG. In the predetermined distance range before and after the position where the element is installed, a substantially constant MTF is realized although the value is low.

  In the MTF having such a characteristic (curve), it is possible to uniformly increase the MTF in an image defocused within a predetermined range by performing various image restoration processes on the obtained image. Thereby, an image having sufficient resolution can be restored. In addition, an image with a deep focal depth can be realized. Note that the position where the defocus amount is 0, that is, the installation position of the image sensor can be set to an appropriate position in consideration of the shape of various MTF characteristics.

  From FIG. 5 (b), it can be seen that, as well as on the axis, the MTF characteristic is substantially constant even outside the axis. From FIG. 5C, the 84 (lp / mm) MTF characteristic intersects with the MTF characteristic of 84 (lp / mm) and the MTF characteristic of 50 (lp / mm) in a range where the contrast does not become zero in the MTF characteristic of 84 (lp / mm). Yes. In such a state, it can be said that the MTF characteristic of 84 (lp / mm) is guaranteed to be substantially constant. Note that the contrast of 0 corresponds to a position where black and white are reversed and the MTF becomes 0 in the MTF of the target evaluation spatial frequency.

  FIG. 6 is a diagram showing the spherical aberration characteristics in Example 1. Here, the spherical aberration characteristics at a wavelength of 546.07 (nm) are shown. In this spherical aberration characteristic, the curve representing the aberration fluctuates on the plus side and the minus side as compared with the spherical aberration characteristic of FIG. In FIG. 6, the aberration curve has three peaks as indicated by arrows. Before and after this peak, the aberration occurs in the direction from the plus side to the minus side or vice versa. .

  Thus, by changing the spherical aberration characteristics in both the positive and negative directions, a substantially constant MTF can be realized in the vicinity of the position where the defocus amount is zero. As in Example 1, it is preferable to form a plurality of peaks on both the positive side and the negative side in the spherical aberration characteristics. In the spherical aberration characteristic, the MTF can be made substantially constant simply by having two or more peaks.

  Next, a numerical example and various characteristics will be described for the second embodiment. In the second embodiment, the fifth surface of the third lens L3 in FIG. 2 is a bifocal lens, thereby realizing a substantially constant MTF at the installation position of the image sensor and a predetermined distance before and after that. The meaning of various numerical values and various design conditions are the same as those described in Comparative Example 1 and Example 1.

  FIG. 7 is a front view of a bifocal lens employed on the fifth surface of the third lens L3 and a cross-sectional view taken along the optical axis. This figure is a diagram schematically illustrating the multifocal lens for easy understanding, and its shape is different from the actual numerical value.

As shown in FIG. 7, the bifocal lens has a region A at the center thereof and a region B so as to surround the region A. In this embodiment, both the region A and the region B have a spherical shape, and the region A and the region B have a shape that changes continuously without a step. In the following numerical examples, the radius for each region, the curvature, and the distance d4 between the lens surfaces (optical surfaces).
, D5 is shown. Here, as shown in FIG. 7, the surface intervals d4 and d5 of the region B are the surface intervals (d4 ′ and d5 ′ in the drawing) at the position where the virtual surface formed by the lens surface of the region B intersects the optical axis. It means something.

Numerical example 2
Unit mm
Surface data surface number r d nd Vd F
1 3.0139 1.2800 1.72341 50.20 6.1743
2 7.6146 0.1923
3 -10.5848 0.2367 1.70448 30.10 -3.5085
4 3.2544 0.3997
5 (2 focal points) 10.7443 0.4438 1.81067 41.00 8.1189
6 -6.5817 0.2367
7 (Aperture) ∞ 7.7389
8 (imaging surface) ∞

Bifocal lens data (surface number 5)
Radius curvature d4 d5
Area A 0.715 10.7443 0.3997 0.4438
Region B 1.2 11.0443 0.4003 0.4432

Various data focal length 9.9902
F number 3.5

Depth characteristics (Evaluation spatial frequency: 84 [lp / mm])
Depth vs. comparative example [%] Converted F number MTF 20% 0.16 177 6.2
MTF 10% 0.19 175 6.1.

  FIG. 8 is a graph showing the MTF characteristics on the axis in the second embodiment. The evaluation spatial frequency is 84 (lp / mm) as in Comparative Example 1. As described above, in the MTF characteristics on the axis shown in FIG. 8 as well, a substantially constant MTF is obtained in a position where the defocus amount is 0, that is, a position where the image sensor is installed and a predetermined distance range before and after the position. You can see it happen.

  FIG. 9 is a diagram showing the spherical aberration characteristic in Example 2, and shows the spherical aberration characteristic at a wavelength of 546.07 (nm) as in Comparative Example 1. This spherical aberration characteristic has several peak values on the plus side and the minus side. Therefore, also in the second embodiment, the MTF is substantially constant at positions before and after the defocus amount is zero.

  Next, a numerical example and various characteristics of the third embodiment will be described. In the third embodiment, as in the second embodiment, the fifth surface of the third lens L3 in FIG. ing. However, the second embodiment differs from the second embodiment in the details of the bifocal lens. The meaning of various numerical values and various design conditions are the same as those described in Comparative Example 1 and Examples 1 and 2.

FIG. 10 is a front view of a bifocal lens employed on the fifth surface of the third lens L3 and a cross-sectional view taken along the optical axis. This figure is a diagram schematically illustrating the multifocal lens for easy understanding, and its shape is different from the actual numerical value.

  As shown in FIG. 10, this bifocal lens is provided with a region A at the center and a region B so as to surround the region A. The third embodiment is different from the second embodiment in that the radius of the region A is large. In the following numerical examples, the radius, curvature, and distances d4 and d5 between lens surfaces (optical surfaces) for each region are shown.

Numerical Example 3
Unit mm
Surface data surface number r d nd Vd F
1 3.0139 1.2800 1.72341 50.20 6.1743
2 7.6146 0.1923
3 -10.5848 0.2367 1.70448 30.10 -3.5085
4 3.2544 0.3997
5 (2 focal points) 10.7443 0.4438 1.81067 41.00 8.1189
6 -6.5817 0.2367
7 (Aperture) ∞ 7.7389
8 (imaging surface) ∞

Bifocal lens data (surface number 5)
Radius curvature d4 d5
Area A 0.78 10.7443 0.3997 0.4438
Region B 1.2 11.0443 0.4005 0.4430

Various data focal length 9.9902
F number 3.5

Depth characteristics (Evaluation spatial frequency: 84 [lp / mm])
Depth vs. comparative example [%] Converted F number MTF 20% 0.14 157 5.5
MTF 10% 0.20 176 6.2.

  FIG. 11A shows the MTF characteristics on the axis when the evaluation spatial frequency is 84 (lp / mm), as in the first comparative example.

  As described above, in the MTF characteristics on the axis shown in FIG. 11A as well, the position where the defocus amount is 0, that is, the position where the image sensor is installed and within a predetermined distance range before and after the position, It can be seen that a constant MTF is achieved.

  FIG. 12 is a diagram showing the spherical aberration characteristic in Example 3, and shows the spherical aberration characteristic at a wavelength of 546.07 (nm), as in Comparative Example 1. This spherical aberration characteristic has several peaks on the plus side and the minus side. Therefore, also in the third embodiment, the MTF is substantially constant at positions before and after the defocus amount becomes zero.

  Next, numerical examples and various characteristics of the fourth embodiment will be described. In Example 4, the five surfaces of the third lens L3 in FIG. 2 are trifocal lenses, thereby realizing a substantially constant MTF at the installation position of the image sensor and a predetermined distance before and after the installation position. The meanings of various numerical values and various design conditions are the same as those described in Comparative Example 1 and Examples 1 to 3.

  FIG. 13 shows a front view of a trifocal lens employed on the fifth surface of the third lens L3 and a cross-sectional view taken along the optical axis. This figure is a diagram schematically showing the multifocal lens for easy understanding, and the shape thereof is different from the actual numerical value.

  As shown in FIG. 13, the trifocal lens has a region A at the center thereof, a region B surrounding the region A, and a region C surrounding the region B. In Example 4, each of the regions A, B, and C has a spherical shape, and has a shape that continuously changes without a step between the regions. In the following numerical examples, the radius, curvature, and distance d4, d5 between lens surfaces (optical surfaces) for each region are shown. Here, the surface intervals d4 and d5 of the region B are as shown in FIG. 13 in the positions where the virtual plane formed by the lens surface of the region B intersects the optical axis (d4 ′ and d5 ′ in the figure). Further, the surface intervals d4 and d5 of the region C are the surface intervals (d4 ″ and d5 ″ in the drawing) at the position where the virtual surface formed by the lens surface of the region C intersects the optical axis.

Numerical Example 4
Unit mm
Surface data surface number r d nd Vd F
1 3.0139 1.2800 1.72341 50.20 6.1743
2 7.6146 0.1923
3 -10.5848 0.2367 1.70448 30.10 -3.5085
4 3.2544 0.3997
5 (3 focal points) 10.7443 0.4438 1.81067 41.00 8.1189
6 -6.5817 0.2367
7 (Aperture) ∞ 7.7389
8 (imaging surface) ∞

Trifocal lens data (surface number 5)
Radius curvature d4 d5
Area A 0.715 10.7443 0.3997 0.4438
Region B 1.105 11.0443 0.4003 0.4432
Region C 1.2 11.2943 0.4025 0.4410

Various data focal length 9.9902
F number 3.5

Depth characteristics (Evaluation spatial frequency: 84 [lp / mm])
Depth vs. Comparative Example [%] Converted F number MTF 20% 0.17 184 6.5
MTF 10% 0.22 195 6.8.

  Example 4 using this trifocal lens also shows its MTF characteristics and spherical aberration characteristics.

FIG. 14 is a diagram showing the MTF characteristics on the axis in Example 4, and FIG. 14A shows the axis on the axis when the evaluation spatial frequency is 84 (lp / mm), as in Comparative Example 1. This shows the MTF characteristics. FIG. 14C shows MTF characteristics when the evaluation spatial frequencies are different. Here, the same 84 (lp / mm) and 100 (l as in FIG.
p / mm) and shows two MTF characteristics together.

  As described above, in the MTF characteristics on the axis shown in FIG. 14A as well, the position where the defocus amount is 0, that is, the position where the image sensor is installed, and the predetermined distance range before and after the position are substantially A constant MTF is realized. In FIG. 14C, the MTF characteristic of 84 (lp / mm) and the MTF characteristic of the evaluation spatial frequency 100 (lp / mm) are within the range where the contrast does not become zero in the MTF characteristic of 84 (lp / mm). Crossed. In such a state, it can be said that the MTF characteristic of 84 (lp / mm) is guaranteed to be substantially constant. Further, in Example 4, the crossing is performed at a position of 10% or less, further confirming that the MTF characteristic of 84 (lp / mm) is substantially constant.

  FIG. 15 is a diagram showing the spherical aberration characteristics in Example 4. As in Comparative Example 1, the spherical aberration characteristics at a wavelength of 546.07 (nm) are shown. This spherical aberration characteristic has several peaks on the plus side and the minus side. Therefore, also in Example 4, the MTF is substantially constant at the positions before and after the defocus amount is zero.

  Next, Example 5 using another optical system will be described together with Comparative Example 2. FIG. 16 is a cross-sectional view taken along the optical axis of the optical system used in Comparative Example 2. FIG.

  The optical system O of Comparative Example 2 includes a first lens L1, an aperture stop S, a second lens L2, and a third lens L3 arranged from the object side to the emission side. In the drawing, an imaging element such as a CCD is installed on the imaging surface indicated by r9.

  The first lens L1 is a positive meniscus single lens having a convex surface facing the object side, the second lens L2 is a positive meniscus single lens having a concave surface facing the object side, and the third lens L3 is It is a biconvex single lens having positive refractive power. Further, for comparison with the fifth embodiment, the design is performed by providing the virtual surface r3 in front of the aperture stop S.

  Further, in this embodiment, the imaging device installed on the imaging surface is designed assuming that the maximum number of pixels in the vertical or horizontal direction is 353 and the pixel pitch is 3.0 (μm).

  The numerical example of the comparative example 2 is shown below. The meanings of various numerical values are the same as those described in Comparative Example 1 and Examples 1 to 4. The evaluation spatial frequency in the depth characteristic is 111 (lp / mm).

Numerical comparison example 2
Unit mm
Surface data surface number r d nd Vd F
1 * 1.0577 0.4200 1.59008 29.90 3.5608
2 1.8160 0.3820
3 ∞ 0.0500
4 (Aperture) ∞ 0.2020
5 -0.3626 0.4200 1.49380 57.40 4.1989
6 * -0.4268 0.0380
7 1.1353 0.3530 1.69979 55.50 1.2981
8 -3.9640 0.6686
9 (imaging surface) ∞

Aspheric data first surface
K = 0
A2 = 0.00E + 00
A4 = 1.58E-01
A6 = 0.00E + 00
A8 = 0.00E + 00
A10 = 0.00E + 00
6th page
K = 0
A2 = 0.00E + 00
A4 = 1.08E + 00
A6 = -5.63E + 00
A8 = 7.40E + 01
A10 = 0.00E + 00

Various data focal length 0.9971
F number 2.8

Depth characteristics (Evaluation spatial frequency: 111 [lp / mm])
Depth MTF 20% 0.06
MTF 10% 0.07.

  FIG. 17 is a diagram showing the MTF characteristic at the evaluation spatial frequency 111 (lp / mm) in Comparative Example 2, and the MTF (unit:%) with respect to the defocus amount (unit: millimeter (mm)) on the axis. )It is shown. The MTF characteristic of Comparative Example 1 has a shape having a sharp peak value of about 65% in the vicinity of 0 (mm).

  FIG. 18 is a diagram showing the spherical aberration characteristics in Comparative Example 2. Here, the spherical aberration characteristics at a wavelength of 546.07 (nm) are shown. From this figure, spherical aberration characteristics with little fluctuation can be seen.

  Next, a numerical example and various characteristics of Example 5 will be described below. FIG. 19 shows a cross-sectional view taken along the optical axis by developing the optical system of the fifth embodiment. In the fifth embodiment, an aspheric plate C is inserted between the virtual surface r3 and the aperture stop S in FIG. 16, thereby realizing a substantially constant MTF at the installation position of the image sensor and a predetermined distance before and after the installation position. is there. The meaning of each numerical value and various setting conditions are the same as those in Comparative Example 2.

Numerical Example 5
Unit mm
Surface data surface number r d nd Vd F
1 * 1.0577 0.4200 1.59008 29.90 3.5608
2 1.8160 0.3820
3 * ∞ 0.0500 2.11986 36.80 11.0766
4 (Aperture) ∞ 0.2020
5 -0.3626 0.4200 1.49380 57.40 4.1989
6 * -0.4268 0.0380
7 1.1353 0.3530 1.69979 55.50 1.2981
8 -3.9640 0.6222
9 (imaging surface) ∞

Aspheric data first surface
K = 0
A2 = 0.00E + 00
A4 = 1.58E-01
A6 = 0.00E + 00
A8 = 0.00E + 00
A10 = 0.00E + 00
Third side
K = 0
A2 = 4.01E-02
A4 = -3.95E + 00
A6 = 6.19E + 02
A8 = -7.92E-01
A10 = -1.04E + 06
6th page
K = 0
A2 = 0.00E + 00
A4 = 1.08E + 00
A6 = -5.63E + 00
A8 = 7.40E + 01
A10 = 0.00E + 00

Various data focal length 0.9973
F number 2.8

Depth characteristics (Evaluation spatial frequency: 111 [lp / mm])
Depth vs. comparative example [%] Converted F number MTF 20% 0.09 159 4.4
MTF 10% 0.11 158 4.4.

  FIG. 20 is a diagram showing the MTF characteristics in Example 5, and FIG. 20A shows the MTF characteristics on the axis. FIG. 20B shows off-axis MTF characteristics. Here, MTF characteristics in two off-axis directions are shown, 0.25d and 0.35d (where 0.5d is the maximum imaging surface height). In FIGS. 20A and 20B, the evaluation spatial frequency is 111 (lp / mm).

  As can be seen from the comparison of the MTF characteristics on the axis shown in FIG. 20A with the MTF characteristics of Comparative Example 2 in FIG. 17, the position where the defocus amount is 0, that is, the imaging In the predetermined distance range before and after the position where the element is installed, a substantially constant MTF is realized although the value is low.

  Further, from FIG. 20B, it can be seen that, as with the on-axis, it has a substantially constant MTF characteristic even on the off-axis.

FIG. 21 is a diagram showing the spherical aberration characteristics in Example 5, and here, the wavelength 54
The spherical aberration characteristic at 6.07 (nm) is shown. This spherical aberration characteristic is a characteristic that varies greatly compared to the spherical aberration characteristic of FIG. 18, and it can be seen that the spherical aberration characteristic varies with two peak values on the minus side.

  As described above, by changing the spherical aberration characteristics, it is possible to realize a substantially constant MTF in the vicinity of the position where the defocus amount is zero.

  As mentioned above, although Example 1-Example 4 and its comparative example 1 were demonstrated using FIGS. 2-15, Example 5 and its comparative example 2 were demonstrated using FIGS. 16-21, According to the optical systems of Examples 1 to 5 as described above, a substantially constant MTF is realized at a position where the defocus amount is 0, that is, at an installation position of the image sensor and a predetermined distance before and after the installation position. When an image is obtained via such an optical system, an image having sufficient resolution can be obtained by performing image restoration processing on the obtained image. It is also possible to obtain an image with a wide depth of focus.

  In order to achieve a substantially constant MTF, the first embodiment is provided with an aspherical shape in the first embodiment, a bifocal lens in the second and third embodiments, and a trifocal lens in the fourth embodiment. However, Example 5 is different from Comparative Example 2 in that an aspheric plate is provided. As a wavefront control element for realizing a substantially constant MTF, not only the aspherical shape of the lens, the multifocal lens and the aspherical plate, but also a phase plate may be used. Furthermore, a substantially constant MTF may be realized by a plurality of wavefront control elements. In Examples 2 to 4, each region of the multifocal lens has a spherical shape, but any region may have an aspherical shape. Further, a substantially constant MTF may be realized by using a birefringent crystal as the material of the wavefront control element.

  Further, the wavefront control element for realizing these substantially constant MTFs may be detachable. By doing in this way, you may enable it to use as a normal optical system (Comparative Example 1 and Comparative Example 2) which has a sharp MTF characteristic. For example, in Examples 1 to 4, the optical system of Comparative Example 1 can be changed by exchanging the third lens L3. In Example 5, the aspherical plate C is removed, and the optical system of Comparative Example 2 is removed. It becomes possible to change to an optical system.

  About the said Example 1- Example 5, the value of each conditional expression (1)-conditional expression (7) is shown below. Note that these are values at a = 20 and b = 10. In addition, with respect to Example 1 and Example 5, 0.25d and 0.35d (however, 0.5d: imaging surface maximum height), off-axis data in two off-axis directions are shown.

Example 1 Example 2 Example 3 Example 4 Example 5
Conditional expression (1) 0.66 0.82 0.72 0.77 0.77
Conditional expression (2) 1.34 1.25-1.08 1.10
Conditional expression (3) 1.01 1.16 1.23 1.08 1.08
Conditional expression (4) 0.73 0.89 0.90 0.91 0.93
Conditional expression (5) 84 84 84 84 111
Conditional expression (6) 84 84 84 84 111
Conditional expression (7) 0.021 0.021 0.021 0.021 0.314
.
Off-axis data
-------- Example 1 -------- -------- Example 5 --------
(0.25d) (0.35d) (0.25d) (0.35d)
Conditional expression (1) 0.25 0.25 0.72 0.715
Conditional expression (2) 1.20 1.16 1.16 1.10
Conditional expression (3) 1.10 1.17 1.12 1.10
Conditional expression (4) 0.21 0.22 0.82 0.80
Conditional expression (5) 84 84 111 111
Conditional expression (6) 84 84 111 111
Conditional expression (7) 0.021 0.021 0.314 0.314
.

  Next, the imaging apparatus and imaging system used in the present embodiment will be described with reference to FIGS. FIG. 22 is a schematic diagram illustrating a configuration of the imaging apparatus according to the present embodiment. The image pickup apparatus 10 includes an optical system 11, an image pickup element 12, an image processing unit 14, and a control unit 13. In the present embodiment, the image restoration processing 30 is executed by the image processing unit 14, but the image restoration processing 30 may be performed outside the imaging apparatus 10.

  In this imaging apparatus 10, the optical system 11 has a substantially constant MTF at the installation position of the imaging element 12 described so far and at a predetermined distance before and after that. The light from the subject is collected by the optical system 11, and an image of the subject is formed at the light collection position. An imaging element 12 such as a CCD is disposed at this condensing position. The image sensor 12 is formed by a group of photoelectric conversion elements (pixels) regularly arranged.

  The light beam incident on the image sensor 12 is converted into an electric signal (image signal) by the photoelectric conversion element of the image sensor 12. This electrical signal is input to the image processing means 14 and subjected to various signal processing such as development processing, gamma correction, image compression processing, and image restoration processing 30 in the image processing means 14. The electric signal subjected to the signal processing is output to an external memory or an external device via a built-in memory or various interfaces in the imaging device 10 (not shown).

  The control unit 13 is a unit that controls the optical system 11, the image sensor 12, and the image processing unit 14 in an integrated manner. The control means 13 includes a CPU, storage means such as ROM and RAM, and various programs stored in the storage means. The control means 13 may also be used as the image processing means 14.

  In the image restoration process 30, a process based on the imaging characteristics of the optical system 11 is performed. In this case, the control means 13 acquires information relating to the imaging characteristics of the optical system 11 and passes it to the image restoration processing 30. According to such a configuration, the image restoration processing 30 corresponding to the optical system 11 can be executed even in the imaging apparatus 10 having the replaceable optical system 11. The imaging characteristics of the optical system 11 are not limited to the information that actually shows the imaging characteristics such as the aperture value and the focal length, but the identification information of the optical system 11 such as the product number is used, and the control means 13 corresponds to the identification information. It may be converted into actual imaging characteristics.

Next, image restoration processing in the imaging apparatus according to the present embodiment will be described. In the following description, an image (image obtained by an image sensor) that is a target of image restoration processing is referred to as an observation image. Various processes (conversions) can be used in the image restoration process, but the available image restoration processes can be roughly classified into the following three types.
(1) Image restoration processing that uses the imaging characteristics of the optical system 11 and performs processing according to the position of the observed image.
(2) Image restoration processing that uses the imaging characteristics of the optical system 11 and that performs certain processing on the entire observed image.
(3) Image restoration processing in which certain processing is performed on the entire observed image without using the imaging characteristics of the optical system 11.

The image restoration process (1) is an image process in which a different process, that is, a so-called space variant process is performed on each pixel of the observed image. This image processing can perform very effective image restoration on the image captured by the optical system 11 of the present embodiment. That is, the position where the image sensor 12 is installed and the MTF in the vicinity thereof can be increased substantially uniformly. Details of this image restoration processing will be described later. Note that the processing may be different for each pixel group, instead of different processing for each pixel.

  The image restoration processing (2) and (3) is image processing in which the same processing, that is, so-called space invariant processing is performed on each pixel of the observation image. As the image restoration processing as in (2), effective image restoration can be performed by filtering the observed image with an inverse function of the degradation function corresponding to the imaging characteristics of the optical system 11.

  The image restoration process (3) includes band enhancement for raising a predetermined band and edge enhancement for adding edge information extracted from the observation image. If these image restoration processes are used, the optical system 11 can be connected. Image recovery can be easily performed without using image characteristics. These image restoration processes (2) and (3) may be a process performed on space or a process performed on the frequency axis using Fourier transform or the like.

  A detailed description of the image restoration process (1) will be given below.

  When a subject whose depth changes continuously is taken, observation images with different blurring directions are obtained from the near side to the far side. Assuming that the center of the subject is in focus, the amount of blur in the observed image of the subject obtained by shooting changes with continuity from large to small to large. Such a case can be defined as a so-called space variant state where the blur of each pixel of the observation image varies according to the coordinate position of the observation image.

  First, if the restored image is defined as f (x, y), the observed image is defined as g (x, y), and the deterioration function is defined as h (x, y, α, β), f (x, y), g (x, The m and nth order derivatives of y) around x and y and the i and kth moments of h (x, y, α, β) can be defined by the equations shown in (Equation 1), respectively. However, the deterioration function h (x, y, α, β) is a blur amount that varies depending on the pixel position of the observed image g (x, y) and the PSF (α, β) indicating the imaging characteristics of the optical system. It is a function to show.

次に観測画像ｇ、回復画像ｆ、劣化関数ｈの関係をモデル化すると（数２）のようにｇは、ｈとｆの畳み込み積分で表すことができる。

Next, when the relationship between the observed image g, the restored image f, and the deterioration function h is modeled, g can be expressed by a convolution integral of h and f as shown in (Expression 2).

この（数２）において、右辺のｈ、ｆをそれぞれテーラー展開（ｈ：Ｎ次打ち切り、ｆ
：Ｍ次打ち切り）にて展開すると、

In this (Equation 2), h and f on the right side are respectively Taylor expansions (h: Nth order truncation, f
: Mth order censoring)

（数３）を（数２）に代入し、ｈ、ｆの積より導かれる各項毎の積分で表すと、各積分の項は、数１にて定義したｈのモーメントに置き換えることが可能となり、（数４）を導くことができる。

Substituting (Equation 3) into (Equation 2) and expressing the integral for each term derived from the product of h and f, each integral term can be replaced with the moment h defined in Equation 1. (Equation 4) can be derived.

この（数４）の両辺をｘ、ｙに関して微分し、ｆ、ｈの微分係数＞Ｎ、Ｍの場合には、各微分係数を０とし、これをｇ^(p,q)＝ｆ^(p,q)となるまでｘ、ｙについてｐ、ｑ回繰り返し、逆算して（数４）のｆの微分値に代入していく。このような手順により（数４）に残るｆの関数は０次の微分の項のみとなり、回復画像ｆは、下記に示すように観測画像ｇと劣化関数ｈの積和演算により表すことができる。

Both sides of this (Equation 4) are differentiated with respect to x and y, and when f and h differential coefficients> N and M, each differential coefficient is set to 0, and this is expressed as g ^{(p, q)} = f ^{(p, p, It} repeats p and q times for x and y until ^q), and back-calculates and substitutes into the differential value of f in (Equation 4). By such a procedure, the function of f remaining in (Equation 4) is only the 0th-order derivative term, and the restored image f can be expressed by the product-sum operation of the observed image g and the degradation function h as shown below. .

f (x, y) = g (x, y) + a ₁ (x, y) · g ′ (x, y) +
... + a _n (x, y) · g ⁽ⁿ⁾ (x, y)
However,
f: restored image, g: observed image, a ₁ , a ₂ ,... a _n : degradation parameter,
g ⁽ⁿ⁾ : nth-order derivative with respect to the observed image,
It is.

  Here, the deterioration parameter is a parameter determined by the deterioration function h, and is a parameter that varies depending on the pixel position of the observed image g (x, y) and the imaging characteristics of the optical system.

  In the present embodiment, the image restoration process of (1) is performed on the observation image while using the imaging characteristics of the optical system 11 and performing conversion according to the position of the observation image. That is, when the subject is imaged by an optical system having a substantially constant MTF at the installation position of the imaging element and a predetermined distance before and after the imaging element, the image processing of (1) is performed on the observation image obtained by imaging ( Compared with the image restoration processing of 2) and (3), the resolution of the image can be restored more effectively (a sufficiently resolved image).

  Now, an example of the image recovery process 30 will be described with reference to FIG. FIG. 23 shows a block diagram of the image restoration processing 30. In this embodiment, the image restoration processing 30 includes an input signal differentiating means 31, a deterioration parameter reading means 32, a deterioration parameter lookup table 33, and a multiplication / addition means 34. Yes.

The input signal differentiating means 31 is a means for differentiating the observed image g, and here uses a Sobel filter for executing the first order differentiation, a Laplacian filter for executing the second order differentiation, and two filters.

The degradation parameter lookup table 33, the pixel position of the observation image g (x, y), and, deterioration parameter a ₁ corresponding to the optical characteristics of the optical system 11, a _2, is ... a _n are stored in advance. As described above, in the present embodiment, the calculation time can be shortened by preparing a lookup table based on the design value of the optical system 11 in advance. In the case of using the Sobel filter and the Laplacian filter, the coefficient read from degradation parameter lookup table 33 is up to _{a 1, a 2, a 3} ~a n may not use.

  The acquisition of the deterioration parameter is not performed by preparing such a look-up table 33, but is calculated by real-time calculation from the optical characteristics, or a plurality of approximate expressions according to the optical characteristics are prepared in advance, and selectively. It is good also as calculating using.

  The deterioration parameter reading unit 32 reads a value corresponding to the pixel position (x, y) from the deterioration parameter lookup table 33 and outputs the value to the multiplication and addition unit 34.

  The multiplication / addition unit 34 multiplies and adds the signal output from the input signal differentiation unit 31 and the read deterioration parameter, and adds the observed image g to output the recovered image f.

  FIG. 24 is a schematic diagram illustrating a configuration of the imaging apparatus 10 when the image restoration process is performed by an external apparatus, and a configuration of an imaging system including the imaging apparatus 10 and the external apparatus 20. In the present embodiment, the image restoration processing 30 is performed by the external device 20.

  The imaging device 10 includes an optical system 11, an imaging device 12, a first image processing unit 14, and a first control unit 13. Each configuration is the same as the configuration having the same sign in the imaging device described in FIG. . In the present embodiment, the first communication means 15 is provided. The first communication unit 15 transmits an image (observation image) captured by the imaging device 10 to the external device 20. In the image restoration process 30 executed by the external device 20, when the imaging characteristic of the optical system 11 is required, the imaging characteristic may be transmitted so as to correspond to the observation image.

  On the other hand, the external device 20 is provided with a second communication means 21, a second image processing means 22 that enables the image restoration process 30, and a second control means 23. The second communication unit 21 is a unit for receiving the image transmitted from the first communication unit 15. These first communication means 15 and second communication means may employ various types of methods regardless of wired or wireless.

  In the second image processing means 22, the image restoration process 30 is executed based on the observation image received via the second communication means 21 or the observation image and the imaging characteristics. The image subjected to the image restoration process 30 is output to an external memory or another external device via an internal memory (not shown) and various interfaces. The second image processing means 22 may perform not only the image restoration processing 30 but also various other image processing.

  As described above, by executing the image restoration processing 30 in the external device 20, it is possible to reduce the processing load in the imaging device 10. In the present embodiment, the communication means 15 and 21 exchange various information such as observation images. However, the various information is exchanged via an external memory that can be attached to the imaging device 10 and the external device 20. It may be.

The imaging apparatus and imaging system according to the present invention have been described above. However, the imaging apparatus and imaging system according to the present invention are used not only for general digital cameras (whether OVF or EVF) but also in the medical field. It can be used in various optical devices such as an endoscope that is inserted into the subject to be observed, a capsule endoscope that is to be observed by the patient who is the subject, and that is observed inside the body, or a microscope.

  Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and embodiments configured by appropriately combining the configurations of the respective embodiments also fall within the scope of the present invention. Is.

L1 ... 1st lens L2 ... 2nd lens L3 ... 3rd lens S ... Brightness stop C ... Aspherical plate 10 ... Imaging device 11 ... Optical system 12 ... Imaging element 13 ... (1st) Control means 14 ... (1st ) Image processing means 15 ... first communication means 20 ... external device 21 ... second communication means 22 ... second image processing means 23 ... second control means 30 ... image restoration processing 31 ... input signal differentiation means 32 ... deterioration parameter reading means 33 ... Deterioration parameter LUT
34 ... Multiplicative addition

Claims (32)

In an optical device that forms an image of a subject on an image sensor and performs image restoration processing on an image obtained by the image sensor,
An optical device comprising an MTF that satisfies the following conditional expression (1):
0.1 ≦ La / Lb ≦ 1, 10 <a <30, 5 <b <20 (1)
However,
La: MTF width when MTF is a% Lb: MTF width when MTF is b% The optical apparatus according to claim 1, wherein the MTF satisfies the following conditional expression (2).
1 ≦ MTF_H / MTF_L ≦ 2 (2)
However,
MTF_H: Maximum peak value of MTF MTF_L: Minimum bottom value of MTF The optical apparatus according to claim 1, wherein the MTF satisfies the following conditional expression (3).
1 ≦ MTF_H / MTF_ave ≦ 1.7 (3)
However,
MTF_H: Maximum peak value of MTF MTF_ave: Average value of MTF within La range The optical apparatus according to any one of claims 1 to 3, wherein the MTF satisfies the following conditional expression (4).
0.2 ≦ La / Lc ≦ 1.2 (4)
However,
Lc: Half width of MTF An image sensor;
An optical system for forming an image of a subject on the image sensor;
Image processing means for performing image processing on an image obtained by the imaging device;
The optical system includes an MTF that satisfies the following conditional expression (1).
0.1 ≦ La / Lb ≦ 1, 10 <a <30, 5 <b <20 (1)
However,
La: MTF width when MTF is a%,
Lb: MTF width when MTF is b%,
It is. The imaging apparatus according to claim 5, wherein the MTF satisfies the following conditional expression (2).
1 ≦ MTF_H / MTF_L ≦ 2 (2)
However,
MTF_H: Maximum peak value of MTF,
MTF_L: Minimum bottom value of MTF,
It is. The imaging apparatus according to claim 5, wherein the MTF satisfies the following conditional expression (3).
1 ≦ MTF_H / MTF_ave ≦ 1.7 (3)
However,
MTF_H: Maximum peak value of MTF,
MTF_ave: average value of MTF within La range,
It is. The imaging apparatus according to any one of claims 5 to 7, wherein the MTF satisfies the following conditional expression (4).
0.2 ≦ La / Lc ≦ 1.2 (4)
However,
Lc: half width of MTF. The imaging apparatus according to any one of claims 5 to 8, wherein the MTF has a spatial frequency that satisfies a conditional expression (5).
ν = 1 / (2 × P × A), 1 <A <20 (5)
However,
ν: spatial frequency,
P: Pixel pitch of the image sensor,
It is. The imaging apparatus according to any one of claims 5 to 8, wherein the MTF has a spatial frequency that satisfies the conditional expression (6).
ν = 1 / (2 × P × A), 2 <A <8 (6)
Where ν: spatial frequency, P: pixel pitch of the image sensor The imaging apparatus according to any one of claims 5 to 8, wherein the MTF has a spatial frequency that satisfies the conditional expression (7).
0.001 <ν / N <3 (7)
However,
ν: spatial frequency,
N: the number of pixels on one side of the image sensor,
It is. The imaging apparatus according to claim 5, wherein the MTF satisfies each of the conditional expressions at an open F number. The imaging apparatus according to any one of claims 5 to 12, wherein the MTF intersects with an MTF having another spatial frequency within a range where the contrast does not become zero. The imaging apparatus according to claim 13, wherein the MTF intersects with an MTF having another spatial frequency at a position of 10% or less. The imaging apparatus according to claim 5, wherein the spherical aberration characteristic of the optical system has a peak. The imaging apparatus according to claim 15, wherein the spherical aberration characteristic of the optical system has two or more peaks. The imaging apparatus according to claim 16, wherein the spherical aberration characteristic peaks are located on a plus side and a minus side. The imaging apparatus according to claim 5, wherein the optical system includes a wavefront control element for realizing the MTF. The imaging apparatus according to claim 18, wherein the wavefront control element for realizing the MTF has an aspherical surface. The imaging apparatus according to claim 18, wherein the wavefront control element for realizing the MTF is a phase plate. The imaging apparatus according to claim 18, wherein the wavefront control element for realizing the MTF is a lens having a plurality of curvatures on one surface. The imaging apparatus according to claim 21, wherein the wavefront control element for realizing the MTF is a lens having different curvatures in the center and the periphery. The imaging apparatus according to claim 21, wherein the wavefront control element for realizing the MTF is a lens having three curvatures on one surface. The imaging apparatus according to any one of claims 18 to 23, wherein the wavefront control element for realizing the MTF uses a birefringent crystal as a material thereof. The imaging apparatus according to any one of claims 18 to 24, wherein a wavefront control element for realizing the MTF is detachable. The image pickup apparatus according to any one of claims 5 to 25, wherein the image processing executed by the image processing unit includes an image restoration process for an image obtained by the image pickup device. 27. The imaging apparatus according to claim 26, wherein the image restoration process uses an imaging characteristic of the optical system. 28. The imaging apparatus according to claim 27, wherein the image restoration process executes a process in which a restored image is represented by the following differential equation.
f (x, y) = g (x, y) + a ₁ (x, y) · g ′ (x, y) +
... + a _n (x, y) · g ⁽ⁿ⁾ (x, y)
However,
f: restored image, g: observed image, a ₁ , a ₂ ,... a _n : degradation parameter,
g ⁽ⁿ⁾ : nth-order derivative with respect to the observed image,
It is. An imaging device according to any one of claims 5 to 28;
An imaging system comprising: an external device that executes an image restoration process on an image obtained by the imaging device. 30. The imaging system according to claim 29, wherein the image restoration processing uses imaging characteristics of the optical system. 31. The imaging system according to claim 29 or 30, wherein the image restoration process executes a process in which a restored image is represented by the following differential equation.
f (x, y) = g (x, y) + a ₁ (x, y) · g ′ (x, y) +
... + a _n (x, y) · g ⁽ⁿ⁾ (x, y)
However,
f: the restored image, g: the image, a ₁ , a ₂ ,... a _n : deterioration parameter,
g ⁽ⁿ⁾ : nth-order derivative with respect to the image,
It is. The imaging device and the external device each include a communication unit,
The imaging system according to any one of claims 29 to 31, wherein an image obtained by the imaging device is transmitted to the external device via the communication unit.

Images