JP2002031585A - Delineation performance evaluation device of lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a delineation performance evaluation device of a lens having extremely high flexibility, capable of coping with evaluation by various kinds of charts, coping with lenses having various diameters and focal distances, and measuring delineation performance highly accurately. SOLUTION: This device has an optical fiber bundle 5 having one end arranged on the image forming position of a lens 1 facing to a chart 4 for delineation performance evaluation as a light entrance plane and the other end elongated in the backward direction of the lens in the state parallel to the optical axis of the lens 1 as a light outgoing plane, a CCD camera 8 for imaging a chart image obtained through the optical fiber bundle 5, an XYZθ stage 10 for executing three-dimensional movement and rotational movement around the optical axis of the optical fiber bundle 5 and the CCD camera 8, and an operation processing device 11 for controlling the three-dimensional movement and the rotational movement of the XYZθ stage 10 based on imaging information of the chart image by the CCD camera 8, to thereby position the optical fiber bundle 5 and the CCD camera 8 on the optimum imaging position to the chart 4, and measuring the delineation performance of the lens l based on the chart image imaged by the CCD camera 8 in the positioned state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drawing performance evaluation apparatus for evaluating the drawing performance of a lens used in a camera or the like.

[0002]

2. Description of the Related Art Conventionally, in evaluating the depiction performance of a photographic lens of a camera, a chart plate on which a chart for resolving power evaluation is described is placed on a film of a camera (camera to be inspected) having a lens to be inspected. A method for visually judging the resolving power of the chart diagram using this image, and an MTF (Modulation Tra)
There is known a method of evaluating performance using an nsfer function) method. In addition, a method of visually determining the resolving power or an optical fiber bundle such as a fiber optic plate (hereinafter referred to as “FOP”) in an MTF inspection apparatus.
The use of a solid-state imaging device (hereinafter, referred to as a CCD) and the use of a solid-state imaging device are also known in Japanese Patent Application Laid-Open Nos. 10-206993 and 9-243515.

[0003] For example, an apparatus for evaluating the depiction performance of a camera disclosed in Japanese Patent Laid-Open No. 10-206993 is shown in FIGS.
This will be described with reference to FIG.

In FIG. 5, reference numeral 101 denotes a zoom lens 101a having a variable focal length movable between a telephoto state (hereinafter abbreviated as a T state) and a wide-angle state (hereinafter abbreviated as a W state).
Camera body 1 to which this taking lens 101a is attached
01b, and the camera to be inspected 101
Is attached to the transport device 103 while being detachably held by the holder 102.

Here, when the camera 101 to be inspected is attached to the holder 102, the back cover (not shown) is open. In front of the taking lens 101a of the camera 101 to be inspected, a chart plate 104 composed of a chart plate 104a for depiction performance evaluation in a T state and a chart plate 104b for depiction performance evaluation in a W state at a predetermined distance. Is the photographing lens 101 of the camera 101
It is arranged so as to be movable in the optical axis direction of a.

The chart plate 104b for the W state is used.
Can be retracted laterally from the optical axis. Further, on the chart plate 104, a drawing performance evaluation diagram including a resolution evaluation chart such as a known stripe chart is drawn.

On the other hand, a flat fiber optic plate (Flat-fiber) is provided at a position corresponding to the focal plane of the camera 101 to be inspected (a position where the film is disposed).
One end 105a of an optical fiber bundle 105 in which optical fibers each having a diameter of about 3 μm are bundled as shown in FIG. 6 called an “Optical Plate” (hereinafter abbreviated as “F-FOP”).
It is arranged while being held at one end of a hollow cylindrical holder 108 formed in a letter shape.

That is, one end 1 of the optical fiber bundle 105
Reference numeral 05a denotes an incident surface of the chart image passing through the photographing lens 101a. The optical fiber bundle 10
The other end 105b of 5 extends rearward along the optical axis, and serves as an emission surface of the chart image.

Further, the holder 108 holds an optical system 107 for enlarging the chart image emitted from the optical fiber bundle 105 about twice. This optical system 107
It is composed of a high refractive index (large NA) objective lens, and specifically uses a microscope objective lens.

A mirror 109 for bending the optical path of the image from the magnifying optical system 107 by 90 degrees is fixed to the L-shaped refraction portion of the holder 108.

Further, a CCD camera 110 is attached to the other end of the holder 108 so as to receive an image from the optical system 107 via the mirror 109.
These optical fiber bundle 105, optical system 107, holder 10
The inspection block 111 is composed of 8, the mirror 109, and the CCD camera 110.

The inspection block 111 is movable in the xyz directions, and the transport device 10 is moved by an appropriate means.
3 is held. Further, the CCD camera 110 is held by the holder 108 so as to be rotatable in the w direction about the imaging optical axis.

Further, the CCD camera 110 is connected to an arithmetic unit 112 as a judging means by an appropriate means.
This computing device 112 is connected to the display device 113.

Here, the arithmetic unit 112 outputs data of the drawing performance of the photographing lens 101a as digital values based on the chart image picked up by the CCD camera 110.

Specifically, in the arithmetic unit 108, the maximum output portion (Bmax) and the minimum output portion (Bmin) in each cell of the CCD camera 110 are used to calculate C
= (Bmax-Bmin) / (Bmax + Bmin) to calculate and output the contrast C.

The display unit 113 displays the output result of the arithmetic unit 112 on a cathode ray tube. It is also possible to print the output result of the arithmetic unit 112 with a printer. The computing device 114 and the display device 115 are attached to the transport device 103 by appropriate means.

In the evaluation apparatus, first, the camera 101 to be inspected is held by the holder 102 and the photographing lens 101 is held.
The focal length of a is set to the focal length to be inspected, such as the W end or the T end, and the position of the chart plate 104a or 104b is set accordingly.

Next, the optical fiber bundle 1 is
The incident end face 105a of the part 05 is moved to a position corresponding to the chart to be analyzed.

At this time, the incident end face 10 of the optical fiber bundle 105
5a, a real image of the chart is formed. Further, since the holder 108 is movable in the xyZ directions, it is possible to freely perform an image analysis of a required portion.

Next, an appropriate switch (not shown) is operated, and the result of imaging by the CCD camera 110 is calculated by the arithmetic unit 11.
2, and output a value based on the contrast C as a digital value as a value for the description performance evaluation.
This is displayed on the display device 113.

[0021]

However, in the above-described conventional device for evaluating the drawing performance of a conventional lens, the CCD
Since the three-dimensional movement and rotation of the camera 110 are constant movements programmed in advance, the versatility corresponding to various test lenses is low. In addition, horizontal (Hori)
zontal), vertical (Vertical) chart (hereinafter referred to as H / V chart), and horizontal (M
The versatility corresponding to various kinds of charts such as eridional and vertical (Sagittal) charts (hereinafter referred to as S / M charts) was low.

Furthermore, the three-dimensional position and angle of the chart to be imaged are slightly different depending on the optical characteristics of the lens to be evaluated.
The position of the P fiber is changed, and the descriptive performance to be evaluated also includes variations in the optical characteristics of the CCD element and the FOP fiber, resulting in a problem that the evaluation accuracy is reduced.

The present invention has been made in view of the above circumstances, and is applicable to evaluations of various types of charts such as H / V charts and S / M charts, and has various diameters and focal lengths. It is an object of the present invention to provide an imaging performance evaluation apparatus for a lens which is extremely versatile and can measure imaging performance with high accuracy.

[0024]

According to a first aspect of the present invention, there is provided an apparatus for evaluating a drawing performance of a lens, wherein one end is disposed at an image forming position of a lens facing a chart for evaluating the drawing performance with one end as a light incident surface, and the other end. An optical fiber bundle extending rearward of the lens in a state of being parallel to the optical axis of the lens with a light exit surface, an imaging unit that captures a chart image obtained through the optical fiber bundle, the optical fiber bundle, and the imaging unit Moving and rotating means for performing three-dimensional movement and rotational movement about the optical axis, and controlling the three-dimensional movement and rotational movement of the moving and rotating means based on imaging information of a chart image by the imaging means; A control unit that positions the bundle and the imaging unit at an optimal imaging position with respect to the chart, and measures the drawing performance of the lens based on the chart image captured by the imaging unit in the positioned state. It is characterized in that it has and.

According to the present invention, the position of the optical fiber bundle for picking up an image of the chart chart and the position of the image pickup means are controlled by the moving / rotating means under the control of the control means based on the image pickup information obtained from the picked-up chart image. By performing dimensional movement and rotational movement, the lens is positioned at an optimal imaging position with respect to the chart, and the imaging performance of the lens is measured based on the chart image captured by the imaging unit in the positioned state.

Therefore, it is possible to evaluate the depiction performance of the lens using various types of charts such as the H / V chart and the S / M chart, and the versatility is extremely high, and the depiction performance is extremely high. Can be measured.

According to a second aspect of the present invention, there is provided the apparatus for evaluating a drawing performance of a camera lens according to the first aspect, wherein the moving and rotating means is controlled by a control means based on positional information of the imaging means obtained at the image forming position. Driving the imaging unit to match the center position of the chart of the chart with a certain portion of the imaging device forming the imaging unit, and match the chart angle of the chart with the parallel configuration angle of the imaging device. It is characterized by the following.

According to this invention, by moving the image pickup means three-dimensionally and rotationally by the operation of the moving and rotating means, the chart center position of the chart always coincides with the fixed image pickup device of the image pickup means. The imaging of the chart is performed by matching the chart angle of the chart with the parallel configuration angle of the image sensor.

Thus, it is possible to capture an image of the chart in which the alignment direction of the image sensor and the pattern direction of the chart, at which the resolution of the imaging means is the highest, are matched, and it is possible to measure the drawing performance with higher precision.

According to a third aspect of the present invention, in the camera lens depiction performance evaluation apparatus according to the first or second aspect, the optical fiber bundle faces a depiction performance evaluation chart with one end having a small diameter as a light incident surface. Placed at the imaging position of the lens to be
The other end of the large diameter is used as a light exit surface, extending rearward along the optical axis direction of the lens, and attached to the image pickup device surface of the image pickup means.

According to the present invention, loss of light amount and blurring of an image between an optical fiber bundle and an image sensor can be eliminated, and the depiction performance of a lens can be evaluated by using a bright and clear image of an enlarged chart image. Becomes possible.

[0032]

Embodiments of the present invention will be described below in detail.

(Embodiment 1) (Configuration) FIG. 1 is a configuration diagram of a lens depiction performance evaluation apparatus according to Embodiment 1 of the present invention. FIG. 2 is an enlarged view of the vicinity of the image sensor according to the first embodiment.

In the configuration of the lens depiction performance evaluation apparatus shown in FIG. 1, reference numeral 1 denotes a photographing lens, which is mounted on a movable portion of the transport device 3 while being positioned by the holder 2. An evaluation chart plate 4 is movably disposed in front of the photographing lens 1 at a predetermined distance.

That is, the evaluation chart plate 4 is composed of a chart plate 4a for evaluating the drawing performance in the telephoto state and a chart plate 4b for evaluating the drawing performance in the wide-angle state.
Drive means (not shown) is used to move the photographing lens 1 in the optical axis
Direction) and a direction (X direction) orthogonal to the optical axis direction. A chart for resolving power evaluation is drawn on the evaluation chart plate 4.

On the other hand, behind the photographing lens 1, a flat fiber optic plate (F-FO)
An optical fiber bundle 5 referred to as P) is arranged.

One end 5a of the optical fiber bundle 5 is an incident surface of a chart image passing through the photographing lens 1. On the other hand, the other end 5b of the optical fiber bundle 5 is an emission surface of a chart image.

Further, an optical system (magnifying optical system) 7 for enlarging the chart image emitted from the optical fiber bundle 5 is disposed behind the optical fiber bundle 5. Behind the optical system 7, a CCD camera 8 serving as an image pickup means is attached so as to receive an image from the optical system 7, and a CCD element 8a serving as an image pickup device constituting the CCD camera 8 is provided in front of the CCD camera 8a. , A cover glass 8b.

The optical fiber bundle 5, the optical system 7, and the CCD camera 8 constitute a photographing block 9.

This photographing block 9 is composed of three XYZ directions.
XYZθ stage 1 which is configured to be movable in three dimensions and is also rotatable in the θ direction about the Z-axis.
It is held by 0. XYZDθ stage 1
0 is held on the transport device 3.

Further, the CCD camera 8 is connected by appropriate means (for example, cable connection) to an arithmetic processing unit 11 which functions as a control means and a judgment means.

The arithmetic processing unit 11 performs the operation of the optical fiber bundle 5 based on the information of the image of the chart 4 captured by the CCD camera 8.
The three-dimensional position of the incident surface 5a is calculated, and the position of the XYZθ stage 10 is controlled so that the positions and angles of the pattern of the CCD element 8a and the chart 4 are fixed. The arithmetic processing unit 11 includes a display device 12
Connected to

Further, the arithmetic processing unit 11 outputs a calculated value of the depiction performance of the photographing lens 1 as a digital value based on the information of the chart image picked up by the CCD camera 8. The display device 12 includes a CRT display or a liquid crystal display for displaying the output result of the arithmetic processing device 11.

(Operation) Next, a method of evaluating the depiction performance of the photographic lens 1 by the lens depiction performance evaluation apparatus of the first embodiment will be described.

In the depiction performance evaluation apparatus, first, the photographing lens 1 is held by the holder 2, and the focal length of the lens is set to a focal length in a telephoto state or a wide-angle state. The evaluation chart plate 4 is moved so that one of the plates 4b faces the photographing lens 1 and is located at the focal plane.

Next, the incident surface 5a of the optical fiber bundle 5 is
Initially operated by the Zθ stage 10 and moved to a position corresponding to the chart to be analyzed. At this time, a real image of the chart is formed on the incident end face 5a of the optical fiber bundle 5,
Further, the luminous flux of the real image enters the CCD camera 8 via the emission end face 5b and is imaged.

The arithmetic processing unit 11 calculates the three-dimensional position of the incident surface 5a of the optical fiber bundle 5 from the information of the image of the chart 4 picked up by the CCD camera 8, and
The position of the XYZθ stage 10 is controlled so that “a” matches the position and angle of the pattern of the chart 4.

Thus, the incidence surface 5a of the optical fiber bundle 5
After determining the position of the CCD camera 8 and the position of the CCD camera 8, the information of the image captured by the CCD camera 8 is further calculated by the arithmetic processing unit 11, and the digital value which is a value for evaluating the drawing performance of the imaging lens 1 is obtained. And output the same on the display device 12.

(Effect) According to the lens performance evaluation apparatus of the first embodiment, the position of the CCD camera 8 that captures the image of the formed chart 4 is calculated based on the position information obtained from the image. The XYZθ stage 10 is automatically controlled according to the calculation result by the device 11 to perform three-dimensional movement,
The chart 4 is rotated to adjust the fixed CCD element 8a of the CCD camera 8 to the position and angle of the pattern of the chart 4.

Therefore, even if the chart 4 is of various types such as an H / V chart and an S / M chart, the chart 4 can be evaluated and its drawing performance is evaluated in correspondence with the photographing lens 1 having various diameters and focal lengths. A highly versatile lens depiction performance evaluation device can be provided.

Also, by the three-dimensional movement and rotation of the XYZθ stage 10, it is possible to always execute the imaging of the chart image using the fixed CCD element 8a or the fixed optical fiber bundle 5 and the resolution of the CCD camera 8. It is possible to perform imaging in which the direction in which the CCD elements 8a, which are the highest, are aligned, and the direction of the pattern of the chart 4 are matched, and it is possible to provide a lens rendering performance evaluation device capable of measuring the rendering performance with higher accuracy. .

(Embodiment 2) (Structure) FIG. 3 shows an apparatus for evaluating the imaging performance of a lens according to Embodiment 2 of the present invention. FIG. 4 is an enlarged view of the vicinity of the image sensor according to the second embodiment.

The second embodiment employs basically the same configuration as that of the first embodiment. Here, different configurations will be mainly described.

The depiction performance evaluation apparatus according to the second embodiment shown in FIGS. 3 and 4 comprises a tapered fiber optic plate (hereinafter referred to as T-FOP) instead of the optical fiber bundle 5 and the optical system 7. The feature is that an optical fiber bundle 6 is used, and the other configuration is the same as that of the first embodiment.

The exit surface 6b of the optical fiber bundle 6 is a CCD
It is directly attached to the surface of the CCD element 8a of the camera 8. The entrance surface 6a of the optical fiber bundle 6 has a small diameter, and the exit surface 6b has a large diameter.

Further, the optical fibers of the optical fiber bundle 6 are connected in such a direction that the alignment direction of the optical fibers coincides with the alignment direction of the CCD element 8a.

(Operation) The operation of the depiction performance evaluation apparatus according to the second embodiment is basically the same as that of the first embodiment, but different operations will be described here.

In the first embodiment, the optical system 7
Is used to enlarge the captured image and re-image it on the CCD element 8a. In the second embodiment, however, the captured image is enlarged using the optical fiber bundle 6.

That is, the optical fiber bundle 6 made of T-FOP
Are formed so that the diameter of each optical fiber is different between the incident surface 6a side and the output surface 6b side. The chart image entered from the small-diameter incident surface 6a has a different size and a large-diameter output surface. 6b.

That is, the chart image can be enlarged by the ratio of the fiber diameter of the optical fiber bundle 6 on the incident surface 6a to the fiber diameter of the optical fiber bundle 6 on the emission surface 6b. And
Since the optical fiber bundle 6 is directly adhered to the CCD element 8a of the CCD camera 8, the exit surface 6b
, That is, the chart image of the chart 4 that has been enlarged and formed, can be directly captured and output to the arithmetic processing unit 11.

(Effects) According to the lens depiction performance evaluation apparatus of the second embodiment, the optical fiber bundle 6 made of T-FOP
And the CCD element 8a of the CCD camera 8 are arranged in close contact with each other, so that the optical fiber bundle 6 and the CCD element 8a
Loss of light and blurring of the image between the lens and the lens can be evaluated, and the depiction performance of the photographing lens 1 can be evaluated using the enlarged chart image captured brightly and clearly. A description performance evaluation device can be provided.

[0062]

According to the present invention described in detail above, the position of the image pickup means for picking up the formed chart image is automatically controlled based on the picked-up information obtained from the formed chart image, thereby enabling three-dimensional movement. By rotating the lens, it is possible to respond to evaluation using various types of chart diagrams such as an H / V chart and an S / M chart, and it is also possible to respond to lenses having various diameters and defocus. It is possible to provide a high lens performance evaluation apparatus.

Further, according to the present invention, by constantly moving and rotating the position of the image pickup means, it is possible to always execute image pickup using a fixed image pickup element or a fixed optical fiber.
In addition, it is possible to perform imaging in which the direction of the imaging element and the direction of the chart are matched so that the resolution of the imaging means is the highest, and it is possible to provide a lens depiction performance evaluation device capable of performing more accurate measurement.

Further, according to the present invention, it is possible to eliminate loss of light amount and blur of an image between the optical fiber bundle and the image sensor, and to evaluate the depiction performance of the lens using a bright and clear image of the enlarged chart image. It is possible to do.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a lens depiction performance evaluation device according to a first embodiment of the present invention.

FIG. 2 is an enlarged view around a CCD element according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram illustrating a lens depiction performance evaluation device according to a second embodiment of the present invention.

FIG. 4 is an enlarged view around a CCD element according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a conventional camera performance evaluation apparatus.

FIG. 6 is an enlarged view showing an optical fiber bundle in a conventional camera imaging performance evaluation apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photographing lens 2 holder 3 transfer device 4 evaluation chart plate 4 a chart plate 4 b chart plate 5 optical fiber bundle 6 optical fiber bundle 7 optical system 8 CCD camera 9 photographing block 10 XYZθ stage 11 arithmetic processing unit 12 display device

Claims (3)

[Claims] An end is disposed at an image forming position of a lens facing a chart for evaluating a drawing performance with one end as a light incident surface, and the other end is extended rearward of the lens in a state parallel to the optical axis of the lens as a light emitting surface. An emitted optical fiber bundle, an imaging unit that captures a chart image obtained through the optical fiber bundle, a moving rotation unit that performs three-dimensional movement of the optical fiber bundle and the imaging unit and a rotational movement around the optical axis, Based on the imaging information of the chart image by the imaging means, controlling the three-dimensional movement and the rotational movement of the moving / rotating means to position the optical fiber bundle and the imaging means at an optimal imaging position with respect to the chart, and in a positioned state And a control means for measuring the depiction performance of the lens based on the chart image picked up by the imaging means. 2. The moving / rotating means drives the imaging means under the control of control means based on position information of the imaging means obtained at the image forming position, and moves the chart center position of the chart and the imaging means. 2. A camera lens depiction performance evaluation apparatus according to claim 1, wherein the matching is performed with a certain portion of the image sensor constituting the image sensor, and the chart angle of the chart and the parallel configuration angle of the image sensor are matched. 3. The optical fiber bundle, wherein one end of a small diameter is disposed at an image forming position of a lens facing a chart for evaluating depiction performance with one end of a light incident surface, and the other end of a large diameter is used as a light exit surface. 3. The lens delineation performance evaluation apparatus according to claim 1, wherein the lens extension performance extends rearward along the optical axis direction of the lens and is attached to an imaging element surface of the imaging means.