JP2000098301A - Optical system with enlarged depth of field - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system with a zoom lens to impart always adequate image processing results. SOLUTION: A video microscope to which this optical system is applied has a zoom lens 2 which forms the image of an object 1, a CCD camera 3 which picks up the image of the object 1 subjected to the image formation, a CCD controller 4 which controls this CCD camera 3, an image processor 5 which processes the image picked up by the CCD camera 3 and a monitor 6 which displays the result processed by this image processor 5. The zoom lens 2 has two stationary lenses 7 and 11, two moving lenses 8 and 9 and a cubic phase modulating mask 10. The video microscope further has an encoder 23 which detects the position of the one moving lens 9 of the zoom lens 2, an NA arithmetic unit 24 which determines the NA of the zoom lens 2 in accordance with the information from this encoder 23 and a filter arithmetic unit 25 which determines the filter coefficient according to the NA determined by this NA arithmetic unit 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for increasing the depth of field of an incoherent optical system.

[0002]

2. Description of the Related Art A technique for increasing the depth of field of an incoherent optical system is disclosed in, for example, US Pat. No. 5,748,371.
And "Edward R. Dowski, Jr., W. Thomas Cathey,"
Extended depth of field through wave-front codin
g ", Appl. Opt. Vol. 34, 1859-1866 (1995)", "Sara
Bradburn, Wade Thomas Cathey, Edward R. Dowski, J
r., "Realization of focus invariance in optical-di
gital systems with wave-front coding ", Appl. 0pt.
Vol. 36, 9157-9166 (1997).

As shown in FIG. 14, an apparatus according to this method is provided with an image pickup means such as a CCD, a lens system for forming an image of an object on a light receiving surface of the image pickup means, and a pupil position of the optical system. A cubic phase modulation mask (see FIG. 15),
An image processing device for constructing an image based on image data from the imaging means.

A cubic phase modulation mask has a plane on one side and a plane on the other side as shown in FIG.
It has a shape represented by z = k (x ³ + y ³ ). The cubic phase modulation mask gives a phase shift of P (x, y) = exp (jα (x ³ + y ³ )) to the phase of light passing therethrough.

In an ordinary optical system having no such cubic phase modulation mask, the intensity distribution of the optical transfer function (0TF) is changed as the object deviates from the in-focus position.
FIG. 17 is changed from FIG. 16 to FIG.

In contrast, in an enlarged depth-of-field optical system having a cubic phase modulation mask, the OTF intensity distribution for the same shift is as shown in FIGS. 19, 20 and 21, respectively. Few. The image formed by this optical system is processed by an image processing apparatus as shown in FIG.
2 is performed by the inverse filter having the characteristic shown in FIG.
The intensity distributions of the OTFs shown in FIGS. 19, 20 and 21 are compared with those shown in FIGS. 23, 24 and 25, respectively.
The intensity distribution of F is obtained. Each of these has a shape close to the intensity distribution of the OTF at the time of focusing of an ordinary optical system.

Next, a description will be given using an actual image. In an ordinary optical system, as the object deviates from the focal position, the image obtained by the imaging device changes from FIG. 26 to FIG. 27 and further to FIG. 28, causing blur due to defocus. 26, 27, and 28 correspond to FIGS. 16, 17, and 1, respectively.
8 corresponds to the intensity distribution of the OTF.

On the other hand, in the enlarged depth-of-field optical system, images obtained by the image pickup apparatus for the same shift, that is, images before image processing are shown in FIGS. 29, 30, and 31, respectively.
Becomes Although these images are all blurred, the degree of blurring is almost constant. When these images are subjected to the image processing by the above-described inverse filter, the images shown in FIGS. 32, 33 and 34 are obtained.
Although these images are not as large as the images in FIG. 26, they are almost similar to the images with little defocus. That is,
It can be seen that the apparatus of FIG. 14 has increased the depth of focus.

[0009]

The above-described enlarged depth-of-field optical system cannot be directly applied to an optical system having a zoom lens. In an optical system having a zoom lens, the OTF of the optical system changes as the zoom ratio of the zoom lens changes. Accompanying this, the coefficient and size of the inverse filter suitable for image processing also change.

Therefore, simply using a configuration in which the lens system of the enlarged depth-of-field optical system shown in FIG. 14 is changed to a zoom lens, it is not always possible to obtain a favorable image processing result.

An object of the present invention is to provide an enlarged depth-of-field optical system applicable to an optical system having a zoom lens. In other words, it is an object of the present invention to provide an enlarged depth-of-field optical system having a zoom lens that always provides a suitable image processing result.

[0012]

SUMMARY OF THE INVENTION An enlarged depth-of-field optical system according to the present invention includes a zoom lens system for converging incoherent light from an object on an image plane, and a zoom lens system for condensing incoherent light on an image plane. Image pickup means for picking up the obtained image, and cubic phase modulation arranged between the object and the image pickup means for constantly changing the optical transfer function (OTF) of the zoom lens system regardless of the position of the object in the optical axis direction. A mask, NA calculating means for calculating the NA of the zoom lens system, and a filter for calculating a filter coefficient for restoring the deformation of the optical transfer function (OTF) by the cubic phase modulation mask based on the NA calculated by the NA calculating means. Using the coefficient calculating means and the filter coefficient calculated by the filter coefficient calculating means, the optical data which is not deformed with respect to the image data obtained by the imaging means. And an image processing means for performing a process for returning to the function (OTF).

The NA calculating means has, for example, position detecting means for detecting the position of the movable lens included in the zoom lens system, and calculates the NA based on the output of the position detecting means.

Alternatively, the NA calculating means may calculate the NA by spatial frequency analysis of the observation image of the standard sample.

[0015]

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

[First Embodiment] A first embodiment of the present invention will be described with reference to FIGS. This embodiment is an example in which the enlarged depth of field optical system according to the present invention is applied to a video microscope.

As shown in FIG. 1, a video microscope includes a zoom lens 2 for imaging an object 1 on an image plane.
A CCD camera 3 that captures an image of the object 1 formed by the zoom lens 2, a CCD controller 4 that controls the CCD camera 3, and an image processing device that performs processing on the image captured by the CCD camera 3. 5
And a monitor 6 for displaying a result processed by the image processing device 5.

The zoom lens 2 has two fixed lenses 7,
11 and two movable lenses 8 and 9. The fixed lenses 7 and 11 are fixed to fixed lens frames 14 and 15 fixed to a lens barrel 16, respectively. The movable lenses 8 and 9 are fixed to movable lens frames 12 and 13 that can move in a lens barrel 16 respectively.

Cam pins 17 and 18 are attached to the movable lens frames 12 and 13, respectively. Cam pin 17,
Numerals 18 respectively engage with cam grooves 19a and 19b extending obliquely across the axial direction of the cam barrel 19 through guide holes 16a and 16b extending parallel to the axial direction of the lens barrel 16. The cam barrel 19 is rotatable with respect to the lens barrel 16, so that the movable lens frames 12, 13 are moved in a direction approaching or moving away from each other in parallel to the optical axis by the rotation of the cam barrel 19. Thereby, the magnification of the zoom lens 2 is changed. That is, the zoom magnification operation can be performed.

In the lens frame 13, in addition to the movable lens 9,
The cubic phase modulation mask 10 is also fixed. The cubic phase modulation mask 10 includes a zoom lens 2
Is constantly deformed regardless of the position of the object in the optical axis direction.

A light guide 20 that transmits light from a light source device 22 that emits illumination light is disposed around the lens barrel 16, and is emitted from the light guide 20 near the tip of the light guide 20. An illumination head 21 for irradiating the object 1 with illumination light is provided.

The video microscope further includes a cam pin 1 attached to a movable lens frame 13 of the zoom lens 2.
An encoder 23 for detecting the position of the movable lens 9, that is, the position of the movable lens 9, an NA calculator 24 for obtaining the NA of the zoom lens 2 based on information from the encoder 23, and a filter coefficient according to the NA obtained by the NA calculator 24. And a filter operation unit 25 for obtaining the calculated value.

The illumination light from the light source device 22 passes through the light guide 20 and is reflected by the illumination head 21 to illuminate the object 1. The reflected light from the object 1 due to the illumination light passes through the fixed lens 7, the movable lenses 8, 9, the cubic phase modulation mask 10, and the fixed lens 11, and forms an image on the image sensor of the CCD camera 3. The imaging magnification at this time is determined by the zoom magnification operation of the zoom lens 2.

The image picked up by the CCD camera 3 is a CCD
It is sent to the image processing device 5 via the controller 4. The encoder 23 detects the position of the cam pin 18 attached to the movable lens frame 13 of the zoom lens 2, and the output signal is sent to the NA operation device 24.

The NA operation device 24 processes the input encoder output signal in accordance with the flowchart shown in FIG.

The NA arithmetic unit 24 starts control after initialization at power-on (step S1). The NA operation device 24 first determines whether or not the encoder output has changed (step S2), and if there is no change in the encoder output, repeats step S2. If there is a change in the output of the encoder, the encoder output is stored (step S3). Subsequently, the NA is calculated based on the newly stored encoder output (Step S).
4), which is output to the filter operation device 25 (step S5). Thereafter, the process returns to step S2. This series of operations (Steps S2 to S5) are always repeated after initialization at the time of power-on.

The determination in step S2 is made by comparing the input encoder output signal with the encoder output signal stored in the previous cycle.
The first determination is made by comparing with a reference value stored in advance.

The calculation of NA in step S4 is performed as follows.

The NA of the optical system of the zoom lens 2 changes according to the movement of the movable lenses 8 and 9 accompanying the zooming operation. The change of the NA of the zoom lens 2 can be calculated at the design stage. Also, since the movable lenses 8 and 9 are linked, if one of the positions is known, the NA of the zoom lens 2 at that time can be known.

FIG. 3 is a graph showing the relationship between the position of the movable lens 9, that is, the encoder output and the NA of the zoom lens. Since the NA of the zoom lens changes continuously, the curve in FIG. 3 can be approximated by a function. The NA calculation device 24 stores this function in advance, and can calculate the NA based on the encoder output. The calculated NA is the NA on the image side.

The filter operation device 25 includes the NA operation device 2
4 is processed in accordance with the flowchart shown in FIG.

The filter operation device 25 starts the control after the initialization at the time of turning on the power (step S10).
The filter operation device 25 first determines whether or not the NA has changed (step S11), and if the NA has not changed, repeats step S11. If there is a change in the output of NA, that NA is stored (step S
12). Subsequently, a filter coefficient is calculated based on the newly stored NA (step S13), and this is output to the image processing device 5 (step S14). Thereafter, the process returns to step S11. This series of operations (steps S11 to S11)
In step S14), after initialization at power-on,
It is always repeated.

The determination in step S11 is made by comparing the input NA with the NA stored in the previous cycle. The first determination is made by comparing with a reference value stored in advance.

The calculation of the filter coefficient in step S13 is performed as follows.

The filter used here is a filter for returning the optical transfer function (OTF) of the zoom lens 2 deformed by the cubic phase modulation mask 10 to the optical transfer function (OTF) not deformed. The intensity component of the untransformed optical transfer function (OTF) is as shown in FIG. 5, and the intensity component of the optical transfer function (OTF) deformed by the cubic phase modulation mask 10 is shown in FIG. It is supposed to be. Therefore, the intensity component of the optical transfer function (OTF) of the filter is calculated as shown in FIG.
FIG. 6 shows the intensity component of the optical transfer function (OTF) shown in FIG.
Is divided by the intensity component of the optical transfer function (OTF) shown in FIG. At this time,
The limit frequency in FIG. 7 is ± 2 NA / λ.

Assuming that the pixel size of the image processed by the image processing device 5 is d, the filter size n is represented by n = (α / 5) ² (λ / dNA) as a formula obtained from an experiment. Here, α is the phase shift P (x, y) due to the cubic phase modulation mask described in the background art.
= Exp (jα (x ³ + y ³ )).

The spatial frequency that can be represented by the pixel size d and the filter size n is the maximum frequency 1
/ 2d and fundamental frequency 1 / nd. Accordingly, the filter coefficient to be obtained is obtained by sampling the optical transfer function (OTF) of FIG. 7 at the maximum frequency 1 / 2d and the fundamental frequency 1 / nd and performing a Fourier transform. From the above calculations, the filter coefficients can be calculated in step S13.

The image processing device 5 includes a filter operation device 25
On the basis of the filter coefficient input from, the processing is performed on the image sent from the CCD controller 4 in accordance with the flowchart shown in FIG.

The image processing apparatus 5 starts control after initialization at the time of power-on (step S20). An observer using the video microscope designates whether to process an image from the CCD controller 4 using a switch (not shown). The image processing device 5 determines whether to perform image processing by determining the state of the switch (step S21). If it is determined not to perform the image processing, the image from the CCD controller 4 is output to the monitor 6 as it is (step S22), and the process returns to step S21.

If it is determined in step S21 that image processing is to be performed, it is determined whether or not the filter coefficient has changed (step S23). This determination is made by comparing the filter coefficient input from the filter operation device 25 with the stored filter coefficient. If it is determined that the filter coefficient has changed, the stored filter coefficient is changed (step S24), and image processing is performed on the image from the CCD controller 4 according to the changed filter coefficient (step S25).

If it is determined in step S23 that the filter coefficient has not changed, the image processing is performed on the image from the CCD controller 4 according to the already stored filter coefficient without changing the filter coefficient. Do.

Thereafter, the result of the image processing is output to the monitor 6 (step S26), and the process returns to step S21.

In the video microscope according to the present embodiment described above, even when the optical transfer function (OTF) changes due to the zooming operation during observation, an appropriate filter always corresponds to the NA at that time. Since the image processing is performed using the coefficient, a suitable image is always obtained.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIGS. This embodiment is also an example in which the enlarged depth of field optical system according to the present invention is applied to a video microscope. In addition,
In the drawings, members equivalent to those described in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted in the following description without duplication.

As shown in FIG. 9, the video microscope according to the present embodiment does not include an encoder for checking the NA of the zoom lens 2, unlike the first embodiment. Accordingly, the NA calculation device 32 calculates the NA according to the information input from the image processing device 31, and the filter calculation device 33 calculates the filter coefficient based on the calculated NA. The other configuration is the same as that of the first embodiment.

The image processing device 31 is a CCD controller 4
Are processed according to the flowchart of FIG.

The image processing device 31 starts the control after the initialization at the time of power-on (step S30). An observer using the video microscope specifies whether to process an image from the CCD controller 4 by using a switch A (not shown). The image processing device 31 determines whether to perform image processing by determining the state of the switch A (step S31). If it is determined not to perform image processing, the CCD controller 4
Is output to the monitor 6 as it is (step S3).
2) Return to step S31.

If it is determined in step S31 that image processing is to be performed, it is next determined whether to change the filter coefficient (step S33). The observer specifies whether to change the filter coefficient. That is, the observer, based on the image being viewed, ie, the image processing result,
It is determined whether the inverse filter used at that time is appropriate or not, and the necessity of changing the filter coefficient is designated by a switch B (not shown). The image processing device 31 determines whether to change the filter coefficient by determining the state of the switch B (step S33).

When the observer determines that the filter coefficient needs to be changed, the observer specifies the change of the filter coefficient by the switch B and replaces the object 1 with the standard sample 30. That is, the observation target of the video microscope is changed to the standard sample 30. The standard sample 30 is
For example, as shown in FIG.
Any shape may be used as long as it has an edge component in the x direction and the y direction.

If it is determined in step S33 that the filter coefficient is to be changed, the image processing device 31 converts the input image, that is, the image of the standard sample 30 into an NA operation device 32.
(Step S34).

The NA calculator 32 calculates the NA according to the flowchart shown in FIG. NA arithmetic unit 3
2 starts an operation (step S40), receives an image from the image processing device 31 (step S41), and performs a Fourier transform of the received image (step S42). Since the limit frequency of the optical system is given by 2NA / λ, the NA of the optical system is obtained from this and the maximum frequency as a result of the Fourier transform of the image (step S43). The obtained NA is sent to the filter operation device 33 (step S44).

The filter operation device 33 calculates a filter coefficient according to the flowchart shown in FIG. The filter operation device 33 starts the operation (step S5).
0), and inputs the NA from the NA operation device 32 (Step S)
51), a filter coefficient is calculated based on the NA (step S52). The method of calculating the filter coefficient is the same as in the first embodiment. The calculated filter coefficient is output to the image processing device 31 (step S53).

After the above processing, returning to FIG. 10, the filter coefficient is input from the filter operation device 33 (step S3).
5) The stored filter coefficient is changed to the newly input filter coefficient (step S36). Image processing is performed according to the changed filter coefficient (step S3).
7) Output the image processing result to the monitor 6 (Step S)
38). Thereafter, the process returns to step S31.

When the observer determines that the image processing result is appropriate, the user cancels the designation of the change of the filter coefficient, returns the observation target from the standard sample 30 to the object 1, and returns the object 1 as the original object. Observe.

If it is determined in step S33 that the filter coefficient is not to be changed, the image processing is performed without performing any operation or processing such as changing the filter coefficient or changing the observation target (step S37). The processing result is output to the monitor 6 (step S38).
Thereafter, the process returns to step S31.

In the video microscope according to the present embodiment, even when the optical transfer function (OTF) is changed by the zooming operation, the image processing is always performed by the filter coefficient which the observer considers to be within the allowable range. Image is obtained.

In the above-described embodiment, the video microscope to which the enlarged depth of field optical system according to the present invention is applied has been exemplified. However, the application of the present invention is not limited to the video microscope. The enlarged depth of field optics according to the present invention comprises:
The present invention can be suitably applied to any optical system having a zoom lens system.

The present invention is not limited to the above-described embodiment, but includes all implementations that do not depart from the gist of the invention. The present invention includes the inventions described in the following items.

(1) An optical system including a lens system for condensing incoherent light from an object on an image plane and an image pickup means for picking up an image condensed on the image plane by the lens system; A cubic phase modulation mask placed between the image pickup means for deforming the optical transfer function (OTF) of the optical system to be constant irrespective of the position of the object in the optical axis direction, and an image picked up by the image pickup means by image processing And an image processing means for performing a process of returning to an optical transfer function (OTF) that has not been deformed, wherein the lens system is a zoom lens system, and is constituted by the zoom lens system. NA for calculating NA during observation of optical system
Calculating means for calculating, from the NA calculated by the NA calculating means, a filter coefficient for restoring a deformation of an optical transfer function (OTF) by the cubic phase modulation mask, wherein the image processing means The enlarged depth of field optical system is an image processing unit that performs image processing using the filter coefficient calculated by the filter coefficient calculation unit. (2) The NA calculation unit configures the zoom lens system. (1) characterized by comprising a position detecting means for detecting the position of the movable lens to be operated, and NA calculating means for calculating the NA of the optical system based on the output of the position detecting means. Enlarged depth of field optics.

(3) The NA calculating means calculates NA by spatial frequency analysis of the observed image of the standard sample.
The enlarged depth-of-field optical system according to item (1), which is an A calculating means.

[0061]

According to the present invention, there is provided an enlarged depth-of-field optical system having a zoom lens which always provides a suitable image processing result. This enables observation by the enlarged depth-of-field optical system at an arbitrary zoom ratio that can be continuously changed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a video microscope to which an enlarged depth-of-field optical system according to a first embodiment of the present invention is applied.

FIG. 2 is a flowchart illustrating a process of the NA operation device illustrated in FIG. 1;

FIG. 3 shows the position and NA of a movable lens in a zoom lens.
6 is a graph showing the relationship of.

FIG. 4 is a flowchart showing a process of the filter operation device shown in FIG. 1;

FIG. 5 is a graph of the intensity component of the untransformed optical transfer function (OTF).

FIG. 6 is a graph showing an intensity component of an optical transfer function (OTF) deformed by a cubic phase modulation mask.

FIG. 7 shows the intensity component of the optical transfer function (OTF) of the filter that returns the intensity component of the optical transfer function (OTF) transformed by the cubic phase modulation mask to the original optical transfer function (OTF); 6 is a graph showing the ratio of the intensity component of the optical transfer function (OTF) of FIG. 5 to the intensity component of the optical transfer function (OTF) of FIG.

FIG. 8 is a flowchart illustrating a process of the image processing apparatus illustrated in FIG. 1;

FIG. 9 is a diagram illustrating a configuration of a video microscope to which an enlarged depth of field optical system according to a second embodiment of the present invention is applied.

FIG. 10 is a flowchart illustrating a process of the image processing apparatus illustrated in FIG. 9;

11 is a plan view of an example of the standard sample shown in FIG.

FIG. 12 is a flowchart showing a process of the NA operation device shown in FIG. 9;

13 is a flowchart showing a process of the filter operation device shown in FIG.

FIG. 14 is a schematic diagram schematically showing a configuration of an enlarged depth of field optical system according to a conventional example.

FIG. 15 is a perspective view showing an external shape of the cubic phase modulation mask shown in FIG. 7;

FIG. 16 is a graph showing an intensity distribution of an optical transfer function (0TF) when an object is at a focal position in a normal optical system.

FIG. 17 is a graph showing an intensity distribution of an optical transfer function (0TF) when an object deviates from a focal position in a normal optical system.

FIG. 18 is a diagram showing an optical transfer function (0) when an object further deviates from the focal position in FIG.
It is a graph which shows the intensity distribution of TF).

FIG. 19 is a graph showing an intensity distribution of an optical transfer function (0TF) when an object is at a focal position in an enlarged depth of field optical system.

FIG. 20 is a graph showing an intensity distribution of an optical transfer function (0TF) when an object deviates from a focal position in an enlarged depth-of-field optical system.

21 is a graph showing an intensity distribution of an optical transfer function (0TF) when an object is further deviated from a focal position in the enlarged depth-of-field optical system than in FIG.

FIG. 22 is a graph showing characteristics of an inverse filter of a process performed on an intensity distribution of an optical transfer function (0TF) in an enlarged depth-of-field optical system.

23 is a graph showing the intensity distribution of the optical transfer function (0TF) obtained by performing the processing by the inverse filter having the characteristics of FIG. 22 on the intensity distribution of the optical transfer function (0TF) of FIG. 19; .

24 is a graph showing an intensity distribution of the optical transfer function (0TF) obtained by performing a process using an inverse filter having the characteristics of FIG. 22 on the intensity distribution of the optical transfer function (0TF) of FIG. 20; .

25 is a graph showing an intensity distribution of the optical transfer function (0TF) obtained by performing a process using an inverse filter having the characteristics of FIG. 22 on the intensity distribution of the optical transfer function (0TF) of FIG. 21; .

FIG. 26 is a photograph of a halftone image displayed on a monitor obtained when an object is at a focal position in a normal optical system.

FIG. 27 is a photograph of a halftone image displayed on a monitor obtained when an object deviates from a focal position in a normal optical system.

FIG. 28 is a photograph of a halftone image displayed on a monitor obtained when an object further deviates from the focal position in FIG. 27 in a normal optical system.

FIG. 29 is a photograph of a halftone image displayed on a monitor obtained when an object is at a focal position in an enlarged depth of field optical system.

FIG. 30 is a photograph of a halftone image displayed on a monitor obtained when an object deviates from a focal position in an enlarged depth of field optical system.

FIG. 31 is a photograph of a halftone image displayed on a monitor obtained when an object further deviates from the focal position in FIG. 30 in the enlarged depth of field optical system.

FIG. 32 is a photograph of a halftone image displayed on a monitor obtained by performing a process using an inverse filter having the characteristics of FIG. 22 on the image of FIG. 29;

FIG. 33 is a photograph of a halftone image displayed on a monitor obtained by performing a process using an inverse filter having the characteristics of FIG. 22 on the image of FIG. 30;

FIG. 34 is a photograph of a halftone image displayed on a monitor obtained by performing a process using an inverse filter having the characteristics of FIG. 22 on the image of FIG. 31;

[Explanation of symbols]

 2 Zoom lens 3 CCD camera 4 CCD controller 5 Image processing device 6 Monitor 6 7,11 Fixed lens 8,9 Movable lens 10 Cubic phase modulation mask 23 Encoder 24NA arithmetic device 25 Filter arithmetic device

Claims (3)

[Claims] 1. A zoom lens system for converging incoherent light from an object on an image plane, an image pickup unit for picking up an image condensed on the image plane by the zoom lens system, and a unit between the object and the image pickup unit A cubic phase modulation mask that is arranged at a position, and that constantly deforms an optical transfer function (OTF) of the zoom lens system regardless of the position of the object in the optical axis direction; NA calculating means for calculating the NA of the zoom lens system; Optical transfer function (OTF) by a cubic phase modulation mask based on the NA calculated by the NA calculating means
Using a filter coefficient calculating means for calculating a filter coefficient for restoring the deformation of the image data, and an optical transfer function (OTF) of the image data obtained by the imaging means, which is not deformed, using the filter coefficient calculated by the filter coefficient calculating means. An enlarged depth-of-field optical system having an image processing means for performing a process of returning to (1). 2. The NA according to claim 1, wherein said NA calculating means has a position detecting means for detecting a position of a movable lens included in a zoom lens system, and calculates the NA based on an output of the position detecting means. Enlarged depth of field optics. 3. The magnified depth-of-field optical system according to claim 1, wherein said NA calculating means calculates NA by spatial frequency analysis of an observation image of a standard sample.