JPH0868721A - Evaluation method of focusing of optical system, adjusting method, focusing evaluation device, adjustment device, and chart device - Google Patents

Abstract

PURPOSE: To provide evaluation method and device of the position of the best image surface which can be evaluated easily and quickly. CONSTITUTION: The system is provided with a chart plate 11 where an edge image 13i can be formed, an optical system 15 where the image of the chart plate 11 can be formed, a light reception member 17 for converting an edge image 13i which is laid out at a position where the edge image 13i of the above chart plate 11 can be formed or near the position, and a sampling circuit for sampling an electrical signal outputted by the light reception member 17 in a direction crossing the edge image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus adjustment and evaluation method for a lens, in particular, a wide-angle lens with a large change in magnification, for example, an endoscope lens, and an apparatus to which these methods are applied. Still another aspect of the present invention is a focus evaluation and adjustment method for performing focus evaluation and adjustment of an optical device having a pan focus optical system that does not perform focus adjustment during observation and photographing, such as a compact camera, a TV camera for monitoring, and an endoscope. And a focus evaluation device and an adjustment device. Still another invention relates to a chart device used in the above evaluation, adjustment method and device.

[0002]

2. Description of the Related Art Conventionally, in the method of inspecting and evaluating the focus state of an imaging optical system, the width of a slit image such as a bright and dark stripe chart (expansion in the case of blur) is the MTF value obtained by Fourier transforming the slit image. Parameters such as the resolution limit frequency based on the periodic chart were used as criteria for evaluation.

However, since the width of the slit image is finite with the parameter of, the problem that the change of the slit image width due to the change of the magnification of the lens to be inspected and the spread of the slit image width due to the focus shift cannot be separated, and the image There was a light quantity problem such as darkness. In order to calculate the MTF, the calculation by Fourier transform must be executed, which requires a long time for calculation, and there is a problem that the cost increases if a high-speed calculation means is used. In the method of obtaining the parameter, the magnification of the imaging optical system may be different, or even if the magnification is the same, the image magnification is different when the subject distance is different. Since it is necessary to use a chart according to the magnification, it is necessary to prepare a large number of charts according to the magnification, and moreover, it is necessary to select an optimal chart from among them, which is troublesome. It was

Further, as the evaluation of the optical system, the lens performance evaluation utilizing the MTF value based on the interference of the transmitted wavefront, the spread of the image of the point light source and the line light source, the reading of the resolving power chart, and the measurement from the image surface side. There is an image performance evaluation by back projection.
Furthermore, there is also a method in which parallel light is made incident by a collimator lens to adjust the focus position to infinity.

However, in an optical system including an optical element having a periodic structure, for example, in an endoscope having an optical fan bar bundle, when the optical performance and focus of an optical system including an objective lens, a fiber bundle and an eyepiece lens are adjusted, It appears as an image in which the structure of the fiber bundle (hexagonal close-packed structure) is superimposed on the image plane. Therefore, when performing the performance evaluation based on the resolution chart, an obstacle such as moire occurs. There are various factors that cause moire, but the main moire is the moire due to the chart with the periodic structure and the periodic structure of the fiber, the moire due to the sampling of the fiber and the periodic structure of the fiber, the periodic structure of the image and the image signal. There are moire due to sampling.

Further, the image through the fiber bundle does not generate an averaged point image by each fiber, but the central part (core) having an intensity distribution similar to a Gaussian distribution due to the structure of the optical fiber and the bundle. Part)
Since the image of the annular portion (clad portion) where light is not transmitted is repeatedly formed, there is a problem that the obtained data includes noise repeatedly.

As a focus evaluation and adjustment method for a pan-focus optical system such as an endoscope, for example, a method in which parallel light is made incident on an objective lens system by a collimator lens to adjust the focus on an object at infinity, and its optics A method is known in which chart members are placed at the closest distance and the farthest distance expected in the system, and focus adjustment is performed so that the defocus amounts for these chart members become equal. For moving the chart plate, for example, the chart plate is moved to different object distances, and at each object distance, the focusing accuracy and the like are confirmed based on the chart image formed on the light receiving element by the lens under test. It was

However, the method using parallel light cannot evaluate the focus position and image performance at a short distance. Further, when the chart plates are sequentially moved, the measurement time becomes long, and since the chart plates are moved, errors such as position and inclination occur each time the chart plates are moved, and repeat accuracy is unstable. Further, when a resolution chart composed of three or more lines or patterns is used as the chart plate, the image magnification varies depending on the object distance. Therefore, in order to obtain the chart images of the same size on the light receiving surface, it is necessary to prepare a large number of chart plates of different sizes in advance and select a chart plate of an appropriate size according to the image magnification. It was
Moreover, conventionally, there is a problem in that a plurality of chart plates cannot be imaged on the image plane at the same time, so that a plurality of chart plates must be sequentially replaced.

Further, an endoscope is required to have a sufficient image (focus) performance from several mm to several tens of centimeters, a compact camera from several tens of centimeters to infinity such as a landscape, and a surveillance camera several meters.
Sufficient image performance is required up to several tens of meters.

In the focus adjustment by each of the above methods, it is difficult to balance the image performance when the object distance is different, and the image performance for a long-distance object is better than necessary, but the image performance for a short-distance object is too bad. On the contrary, the image performance for an object at a short distance is better than necessary, but the image performance for an object at a long distance is too bad.

Further, generally, the imaging magnification of the optical system depends on the object distance. That is, even if the objects are the same size, an object at a short distance looks very large, but an object at a long distance looks very small. Therefore, the human sense of vision has a characteristic that how defocus is felt by defocus also changes depending on the magnification, and even if the amount of blur is the same, the blur becomes more conspicuous as the distance is lower.

Further, in the case of a medical endoscope, when observing a wide range of organs such as the esophagus, stomach, and intestines, a high focusing performance is required over several cm to several tens of cm. In the case of the target, it is sufficient if the focusing performance at a short distance of several mm is good, and the focusing performance at several cm or more may be meaningless at all. Since these focusing performances depend on the observation target and the subjectivity of the doctor who uses them, in the far and near focus balances where the amount of blur is equal on the image plane side,
The user was not always satisfied. As a method for focusing the optical system, a collimator lens is used to make parallel light incident on the optical system to adjust the focus position for infinity and to evaluate the image plane performance, or to move the chart plate to multiple object distances. Things are known.

However, the method using parallel light cannot evaluate the focus position and image performance at a short distance. When the chart plates are sequentially moved, the measurement time becomes long, and each time the chart plates are moved, errors such as the position and inclination of the chart plate occur, and repeated measurement accuracy is unstable.

As a chart of the chart plate, a plurality of lines,
When a resolution chart composed of patterns is used, the image magnification varies depending on the object distance. Therefore, in order to obtain the chart images of the same size on the light receiving surface, it is necessary to prepare a large number of chart plates of different sizes in advance and select a chart plate of an appropriate size according to the image magnification. It was Moreover, the conventional focus evaluation method is
Since the chart plate was placed at a reference distance irrelevant to the user's preference, it often deviated from the focus position actually desired by the user.

Further, in the conventional evaluation method, when there is a large variation in the performance of the lens under test and the focus evaluation values for the chart plates placed at different object distances deviate from the reference evaluation values unevenly. , The evaluation became difficult because the standard became ambiguous.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is a method for evaluating focus and best image plane position, which allows easy evaluation and setting of focus and best image plane position in a short time. And to provide an evaluation device. Another object of the present invention is to provide an evaluation method capable of evaluating an optical system having a periodic structure in a short time regardless of the structure.

Still another object of the present invention is to provide a chart device capable of easily and accurately measuring the focus adjustment of an optical system and the image performance with respect to a plurality of different object distances.

Still another object of the present invention is to provide a focus adjusting method and a focus adjusting device which can easily perform the focus adjustment desired by the user according to the user, operating conditions and the like.

Still another aspect of the present invention is a focus evaluation method for evaluating a focus state based on a total evaluation value obtained by a predetermined calculation from a plurality of evaluation values, not the evaluation value itself obtained from each chart plate, and a focus evaluation method. It is an object of the present invention to provide a focus adjustment method that determines an adjustment amount.

[0020]

SUMMARY OF THE INVENTION According to the present invention, which achieves this object, a chart member capable of forming an edge image, an optical system for forming an image of the chart member, and an edge image of the chart member is formed by the optical system. It is characterized in that it is provided with light receiving means arranged near the position for converting an edge image into an electric signal, and sampling means for sampling an electric signal output by the light receiving means in a direction intersecting with the edge image. .

According to a third aspect of the present invention, a step of forming an edge image of the chart member in the vicinity of the light receiving means by an optical system and a sampling step of sampling a light quantity distribution in a direction intersecting with the formed edge image. And a step of calculating the line spread function (LSF) by differentiating the sampled light amount distribution signal in the sampling direction.

According to the twelfth aspect of the present invention, the step of forming an edge image of the chart member on the light receiving means or its vicinity by an optical system and the sampling of the light amount distribution in the direction intersecting with the formed edge image. The sampling stage and two points on the object field side that are conjugate with the two points on the image field side, which are equidistant from each other in the opposite direction from the best image plane position expected in the image field, are arranged in one or more positions. Evaluating the image plane position based on an output signal from the light receiving means based on a chart.

A fifteenth aspect of the present invention is an evaluation system for an optical system including an optical element having a periodic structure, wherein a chart member that forms an edge image and an edge image of the chart member are formed by the optical system. It is characterized in that it is provided with a light receiving means arranged at or near the above position and a calculating means for performing a predetermined calculation based on the output of the light receiving means.

A sixteenth aspect of the present invention is a method for evaluating an optical system including an optical element having a periodic structure, wherein a chart member having a light-dark difference in a one-dimensional direction is provided to the light receiving means or its vicinity by the optical system. Forming an image, smoothing the chart member image received by the light receiving means to obtain one-dimensional data in the direction of change in brightness of the chart member image, and performing a predetermined calculation based on the one-dimensional data. And a step.

According to a thirtieth aspect of the present invention, there is provided a chart device for forming an image of a chart member on an observation surface at a predetermined distance by an optical system to be inspected, wherein a plurality of chart members are provided.
It is characterized in that they are arranged at different object distances, and that the images of the respective chart members are simultaneously formed by the optical system under test at different positions on the observation surface at a predetermined distance.

The invention described in Item 45 is a focus evaluation method for an optical system, which is a step of arranging one or a plurality of chart members at different object distances of the optical system, and an imaging position of the optical system. Or a step of forming an image of each chart member on the light receiving means arranged in the vicinity thereof, and a predetermined target value for forming an image on the light receiving means of the chart member having the different object distance, Calculating an evaluation value of the formed image of each chart member.

A fiftieth aspect of the present invention is a method for adjusting the focus of an optical system, wherein the step of arranging one or more chart members at different object distances of the optical system to be inspected and the connection of the optical system. Forming the image of each chart member on the light receiving means arranged at or near the image position, and forming an image on the light receiving means with respect to a preset target value for the image on the light receiving means of each chart member. A focus evaluation step of calculating the evaluation value of the image of each chart member, and a focus adjustment step of adjusting the focus position of the optical system to be tested based on the target evaluation value and the calculated evaluation value. It has characteristics.

According to a 56th aspect of the present invention, there is provided a focus adjusting device for an optical system, comprising a chart member arranged at a plurality of object distances of an optical system to be inspected, and an image forming position of the optical system or its vicinity. The arranged light receiving means, the blur amount calculating means for calculating the blur amount of the image of each chart member formed on the light receiving means, and the calculated blur amount of the image of each chart member are set to a preset target value. And a focus adjusting means for adjusting the focus position of the optical system to be inspected so that they coincide with each other.

The fifty-seventh aspect of the present invention is a method for evaluating the focus of an image-forming optical system, wherein a predetermined distance range sandwiching an object distance for which the best focus is expected for the test image-forming optical system. Converting the image formed by the image forming optical system to be inspected by N chart means (where N is an integer of 2 or more) located within the above; into each of the converted data. Calculating a focus evaluation value y _n (n = 1 to N) for each chart means based on the above; and a function based on the N evaluation values y _n , S = g (y ₁ , y ₂ , ..., y _n , ..., Y _N ), the step of calculating the actual measurement comprehensive evaluation value S;

According to the invention described in Item 60, the near chart means located closer to the object distance for which the best focus is expected for the test imaging optical system and the far chart located at the same distance. Means and an intermediate chart means located between the two chart means, for converting the image formed by the imaging optical system under test into electrical data; each based on the transformed data. Calculating focus evaluation values y ₁ , y ₂ , y ₃ for the chart means; and a function based on the above three evaluation values y ₁ , y ₂ , y ₃ , S = g (y ₁ , y ₂ , y ₃ ), the step of calculating the actual measurement comprehensive evaluation value S by;

According to a sixty-fifth aspect of the present invention, there are N pieces (where N is 2) located within a predetermined distance range sandwiching the object distance for which the best focus is expected for the test imaging optical system.
A step of converting the image formed by the image forming optical system to be examined into electrical data by the chart means of the above integer); focus evaluation value y _n for each chart means based on each of the converted data. (N = 1 to N); a step of changing the focus state by the focus adjustment amount x; the focus evaluation value y _n is a function of the focus adjustment amount x, y
_n = f _n (x); a function based on the N focus evaluation values y _n (n = 1 to N), S = g (y ₁ , y ₂ , ..., Y _n , ..., y _N ) to calculate the actual measurement comprehensive evaluation value S; and based on the functions f _n , g, the focus evaluation value y _n, and the actual measurement overall evaluation value S, a preset reference overall evaluation value S ₀ is set. And a step of obtaining a satisfactory focus adjustment target value x ₀ by calculation.

According to a sixty-seventh aspect of the present invention, the near chart means is located closer than the object distance for which the best focus is expected for the test imaging optical system, and the far chart is located at the same distance. Means and an intermediate chart means located between the two chart means, for converting the image formed by the image-forming optical system under test into electrical data; based on each of the converted data The step of calculating the focus evaluation values y ₁ , y ₂ , y ₃ for each chart means; the step of changing the focus state by the focus adjustment amount x; the focus evaluation values y ₁ , y ₂ , y ₃ of the focus adjustment amount x. Function, y ₁ = f ₁ (x) y ₂ = f ₂ (x) y ₃ = f ₃ (x); the above three focus evaluation values y ₁ , y ₂ , y
A step of calculating a measured total evaluation value S by a function S = g (y ₁ , y ₂ , y ₃ ) based on ₃ ; and the functions f ₁ , f ₂ , f ₃ , g and the focus evaluation value y ₁ , y
₂ , y ₃ and a step of calculating a focus adjustment target value x ₀ satisfying a preset reference total evaluation value S ₀ based on the actually measured total evaluation value S.

In the 72nd aspect of the present invention, there are N pieces (where N is 2) located within a predetermined distance range sandwiching an object distance for which the best focus is expected for the test imaging optical system.
(The above integer) chart means; means for converting the image of each chart means formed by the test imaging optical system into electrical data; and for each chart means based on each converted data. Focus evaluation value y _n (n =
1 to N), and a function based on the N evaluation values y _n , S = g (y ₁ , y ₂ , ..., Y _n , ..., y _N ) to calculate the actually measured total evaluation value S. It is characterized in that it is provided with a computing means.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments. First, the configuration of an optical device to which the image plane position evaluation method of the present invention is applied will be described with reference to FIGS. The optical system in this embodiment is of a type in which the relative positional relationship of each optical element does not change during normal use.

The chart plate 11 capable of forming an edge image by the imaging optical system has a bright portion 12 and a dark portion 14 on its surface,
The light portion 12 and the dark portion 14 are switched with the straight edge 13 as a boundary. The chart plate 11 is arranged on the image field side of the optical system (imaging lens) 15 so as to be orthogonal to the optical axis O, and at a position where almost the center of the edge 13 passes through the optical axis O. An image sensor 17 is arranged in the image field of the imaging lens 15, and an image of the chart plate 11 (hereinafter referred to as “chart plate image 11i”) is generated by the image sensor 1.
An image is formed on 7 or near the front and back thereof. The chart plate image 11i is an inverted real image, and the edge image 13i (the bright portion 12
(Image formed at the boundary between the image 12i of 12) and the image 14i of the dark portion 14) passes through the optical axis O. In this state, the image sensor 17 is moved in parallel with the optical axis to adjust the focus. The image sensor 17 of the present embodiment can be constituted by, for example, a CCD image pickup element in which a large number of photoelectric conversion elements are arranged in a matrix, but the present invention is not limited to this, and a line sensor can also be used.

The image sensor 17 converts the chart image into an electric signal. The electrical signal is sampled (read out) by the sampling circuit 19 and a predetermined arithmetic processing is performed by the arithmetic means 21 to calculate an evaluation value and the like, and the arithmetic result is displayed as a numerical value or in the form of a graph. 23 is displayed. Further, based on the calculation result, the evaluation means 25 evaluates the best image plane position and the like by the evaluation method described later (see FIG. 13). Computing means 2
As 1 and the evaluation means 25, computers such as personal computers and workstations are used. The evaluation result and the like may be displayed in another format, for example, printed out by a printer. The evaluation may be performed by the operator based on the evaluation value.

FIG. 2 shows a second embodiment applied to an optical device using the optical fiber bundle 33.
In the second embodiment, the image of the chart plate 11 (inverted real image) is formed on the incident end face of the optical fiber bundle 33 by the first imaging lens 31, and the optical fiber bundle 3 is formed.
An image (inverted real image) emitted from 3 is formed on the image sensor 17 as an erect real image by the second imaging lens 35. Focus adjustment in this embodiment is performed by adjusting the distance between the first imaging lens 31 and the optical fiber bundle 33, and the optical fiber bundle 33 and the second imaging lens 3 are adjusted.
The distance between 5 and the image sensor 17 is not changed.

FIGS. 3 and 4 show the optical device of FIG.
An evaluation mode in the case of observing or photographing an object within a certain field distance range is shown. In this embodiment, the chart plates 11 are arranged at the far point, which is the farthest distance of the object field in normal observation, and the near point, which is the closest distance. In this state, the image sensor 17 is moved in the optical axis direction to adjust the focus. In this embodiment, the chart plate image 11i formed on the image sensor 17 is an inverted real image whose edge image passes through the optical axis O as in the embodiment shown in FIG. That is, if the contour (outer shape) of the chart image 11i is larger than the light receiving surface of the image sensor 17, the edge images of the far point and the near point on the image sensor 17 are substantially different only in the blurred state. Therefore, the same chart plate 11 can be used in the embodiments of FIGS. 3 and 4. In other words, the same chart member can be used regardless of the focal length and magnification of the test optical system.

5 and 6 show a transmission type chart member 41 and a reflection type chart member 41 as examples of the chart member. In the transmissive type, the lighting device 43 is
The chart member 41 is arranged on the back surface of the chart member 41 to illuminate the chart member 41 through transmission. In the reflection type, the illuminating device 43 is arranged outside the optical path composed of the chart member 45, the imaging lens 15 and the image sensor 17 to illuminate the chart member 45.

As the transmission type chart member 41, it is possible to use, for example, a transparent or milky white resin or frosted glass which is entirely coated with black paint on a dark portion. As the reflection type chart member 45, for example, white paper or a resin plate is used, the dark portion is formed by painting black, the light portion is ground color, and a solid surface such as magnesium oxide is used.
Alternatively, a light emitting member such as an electroluminescence (EL) panel is used. The bright and dark parts of the chart member are shown in black and white, but the color is not limited to this.
Any color scheme with a large contrast difference may be used.

Next, regarding the evaluation method of the above optical device,
Further description will be made with reference to FIGS. Hereinafter, the sampling is performed by the sampling circuit 19, the operation is performed by the operation means 21, the operation result is displayed as a graph on the display device 23, and the evaluation based on the operation result is performed by the evaluation means 25 or by the operator. In this embodiment, the chart plate image 11i formed on the image sensor 17 is positioned in a direction orthogonal to the edge image 13i (in FIG. 7, position coordinates are set in the lateral direction orthogonal to the optical axis, and the coordinate x _{0 is set.}
To x _n ). The light intensity distribution curve sampled in this way is shown in the graph of FIG. Here, the horizontal axis represents the position in the direction orthogonal to the edge image 13i, and the vertical axis represents the light intensity. In this graph, the light intensity is
There is a sharp change before and after the edge image 13i. here,
When the edge image 13i is clear, that is, in the focused state, the light intensity changes in a state close to a right angle, but when it is unclear, that is, in the so-called defocused state, the larger the defocus amount is, the gentler the inclination is. Changes. Therefore, it can be seen that the state of FIG. 8B is closer to the in-focus state than the state of FIG.

In FIGS. 9A and 9B, the above-mentioned FIG.
The differential curves of the light intensity curves of (A) and (B) are shown. In this embodiment, this differential curve is used as LSF. In these graphs, α is the interval between two sampling points where the LSF first falls to 0 from the LSF peak to the left and right, and β is 2 when the LSF becomes 1/2 of the peak value (max). The width (half-width) of one sampling point, γ, represents the width of two sampling points when LSF becomes ¼ of the peak value (max). FIG.
0 represents the average value m and the standard deviation σ of FIG. When LSF is an f (x) function, m and σ are expressed by the following equations 1 and 2, respectively.

[Equation 1]

[Equation 2] In the above equation, x ₁ and x ₂ indicate the start point and the end point of the calculation section.

The above evaluation values (α, β, γ, σ) are obtained by moving the image sensor 17 along the optical axis or by changing the distance between the first lens 31 and the end face of the fiber bundle 33. Then, based on at least one of the evaluation values α, β, γ, σ obtained by the above processing, the position in the optical axis direction of the image sensor 17 having the smallest evaluation value, or the first lens 31. And the end surface of the fiber bundle 33 is determined as the best position. Alternatively, two points (far point and near point) on the object side that are conjugate with two points that are equidistant in opposite directions from the best image plane position expected on the image field side are set as one set, and The intersection of the change curves of the two evaluation values is taken as the best image plane position. The specific method for evaluating (determining) the best image plane position is shown below.

The evaluation value becomes larger as the lens performance becomes worse or the defocus becomes larger, and the performance becomes better.
Alternatively, the smaller the defocus, the smaller the value. When moving the image sensor 17 in the optical axis direction, the chart plate 11 is placed at the reference object distance, and the image sensor 17 is moved in the optical axis direction to determine the position where the evaluation value is the smallest as the best position. . The graph in this case is
It is shown in FIG. In this graph, the position z having the smallest evaluation value is the best image plane position.

Further, in the embodiment shown in FIGS. 3 and 4,
The chart plate 11 is placed at the far point and the near point, and the image sensor 17 is moved along the optical axis with respect to the chart plate 11 at each position to obtain the same evaluation value as in FIG. The relationship between these evaluation values and the position of the image sensor 17 is shown in the graph of FIG. 12 as a far point chart evaluation value (solid line) and a near point chart evaluation value (broken line). In this embodiment, the far point,
The position z where the evaluation values on the near point chart are equal is defined as the best image plane position. As described above, in the illustrated embodiment, the case where the width and the standard deviation are used as the evaluation value is shown. However, when the width is used, the calculation time is shortened, and when the standard deviation is used, the evaluation value is stabilized.

14 to 26, the above-mentioned
The Example of this invention which suppresses the moire of and is shown. In the present invention, the moire of is suppressed by using a chart having no periodic structure, the moire of is suppressed by increasing the number of samplings per fiber, and the moire of is suppressed by smoothing. .

FIG. 14 shows the focus evaluation method of the present invention.
Example 3 used for the position evaluation of the objective lens of an endoscope is shown. Usually, the objective lens 51 of the endoscope is fixed to the fiber bundle, so that the position is adjusted so that an object within a predetermined subject distance range can be observed.
According to the evaluation method of the present invention, this objective lens can be positioned easily and easily. The embodiment shown in FIG. 14 is equivalent to the embodiment shown in FIG. In this embodiment, the inverted real image of the chart plate 11 is formed on the incident end surface 53a of the optical fiber bundle 53 through the objective lens 51, the inverted real image is emitted from the exit surface 53b, and the eyepiece lens group 5 is formed.
5 forms an erect real image on the light receiving surface of the image sensor 17. The optical fiber bundle 53 is formed by bundling a large number of optical fibers 52 with a hexagonal close packing structure.

15 to 17, the incident end face 53a is shown.
The chart image in FIG. The chart image includes a bright area image 12i, a dark area image 14i, and a bright area image 12i and a dark area image 1.
It consists of an edge image 13i formed at the boundary with 4i,
Since the ratios of the light portion image 12i and the dark portion image 14i applied to the respective optical fibers 52 are different, the vertical light and dark distribution of the edge image 13i may not be uniform. That is, the portion of the same brightness in the optical fiber 52 unit is not linear (see FIGS. 15 and 17). Therefore, when the light intensity of the image of the end face of each optical fiber 52 is sampled one-dimensionally (in a straight line) in the horizontal direction, the intensity distribution shifts if the vertical sampling position is different, and an accurate light intensity distribution can be obtained. Can not. Further, as shown in FIG. 16, even if the arrangement of the optical fibers 52 coincides with the direction in which the edge image 13i extends, if the horizontal position is one-dimensionally sampled, the light intensity distribution in the horizontal direction also changes when the vertical position is different. It will be different. Therefore, in the focus evaluation method of the present embodiment, the above problem is solved by two-dimensionally sampling and averaging.

FIGS. 18 and 19 are diagrams for explaining how the image of the chart plate 11 is transmitted in the third embodiment shown in FIG. The image of the chart plate 11 is the objective lens 51.
Is formed as an inverted real image on the incident end face 53a,
The light is emitted from the emission end surface 53b and is formed as an erect real image on the light receiving surface by the eyepiece lens group 55. The degree of blurring caused by the objective lens 51 and the eyepiece lens group 55 during focusing is
It can be calculated from the lens design data. Normal,
The blur caused by the objective lens at the time of focusing is designed to be about one optical fiber. Further, since the diameter of each optical fiber 52 is also clear, the size of the image and the degree of blurring on the light receiving surface of the image sensor 17 can be calculated in advance.

18 and 19, reference numeral 57 indicates the intensity distribution when the image of the chart plate 11 formed on the image sensor 17 is sampled in the horizontal direction for one row of the light receiving elements. The image formed on the incident end face 53a is transmitted in units of one optical fiber, and the width of the light receiving element is smaller than the diameter of each optical fiber (4 in this embodiment:
1). Therefore, the light intensity distribution gradually changes for each optical fiber. Here, FIG. 18 shows a focused state, and FIG.
Is out of focus.

By the way, the optical fiber bundle 53 is
Since the hexagonal close-packed structure is composed of a large number of optical fibers 52 composed of the core 52a and the clad 52b, the structure is changed by rotation as shown in FIGS. 15 to 17, and the optical fiber bundle 53 is rotated about the optical axis. The transmitted pattern changes depending on the corner. Where if
If one pixel is associated with one optical fiber, moire will occur. Therefore, in this embodiment, one optical fiber is associated with 4 pixels in the diameter direction, and each optical fiber 52 is sampled with 4 pixels or more. Thereby, the generation of moire was suppressed.

FIG. 20 shows how one-dimensional data is obtained by averaging the sampled images in the extending direction of the edge image 13i. The average number of rows is (two optical fibers) × (pixel density) in the state of FIGS.
In the state of No. 7, (4 to 5 optical fibers) × (pixel density) is used. In FIG. 18, 15 lines are used.

The light intensity of the one-dimensional data in the horizontal direction thus obtained is shown in FIG. As is clear from this figure, in this state, periodic noise remains in the lateral direction.
Therefore, smoothing is performed as shown in FIG.
In the smoothing of this embodiment, data for 8 pixels from the upper left side is averaged to form one new pixel. The average number of pixels depends on the size of the image of the periodic structure of the optical fiber bundle 53 and the size of the pixels on the sampling side (8 to 10 pixels in the illustrated embodiment). As a result of this smoothing, the one-dimensional data in the horizontal direction is as shown in FIG.
Horizontal noise is reduced. The evaluation value can be obtained at this stage. Although not shown, in the graph of FIG. 23, the rising and falling intervals of the graph, the ratio of the minimum value and the maximum value to the area determined by the inflection point interval, and the like can be used as the evaluation value.

Further, when a differential value is obtained in the horizontal direction with respect to the data shown in FIG. 23, a line spread function (line spread function (LSF)) as shown in FIG. 24 is obtained. On the left side of the curve in the figure, the vibration due to the periodic structure that has not been removed by smoothing is seen. The mountain width at the center of the curve corresponds to the degree of edge blur. The part of the right side of the curve where the light intensity is small has no periodic component due to smoothing. By subjecting this data to Fourier transform, the MTF shown in FIG. 26 can be obtained, and the transfer characteristics of the system in this focused state can be evaluated. Further, the width α of the tail of the peak shown in FIG. 24, the half width β, or the standard deviation σ calculated based on the distribution shown in FIG. 25 can be used as the evaluation value without performing the Fourier transform. It should be noted that although the Fourier transform is general, it has a problem that the calculation time is long, but according to the present embodiment, there is an advantage that the evaluation value can be obtained in a short time.

In the above description, the case where the sensor is an area sensor is shown, but an image can be obtained by scanning using a line sensor or a point sensor. Further, the image is optically smoothed by disposing the optical low-pass filter in front of the light receiving means without performing the smoothing by the computing means, and the smoothing computation processing becomes unnecessary. In this case, the optical system becomes complicated, but the calculation time is shortened. Further, although the bright and dark edges are shown as the chart to be used in this embodiment, a line chart is also possible.
If you use the line chart, the input image is LSF as it is.
Therefore, the calculation processing is reduced and the calculation time is shortened.

The present invention relating to the chart device will be described based on illustrated embodiments. 27 to 29 show an embodiment of the chart device of the present invention. The chart device 110 is an embodiment used for focus adjustment and inspection of an optical system such as an endoscope or a pan-focus camera in which an object distance to be observed or photographed is limited to a certain range.

The chart device 110 comprises four fan-shaped chart plates 1 fixed at different axial positions of the rotary shaft 111.
13, 115, 117, and 119 are provided. Each of the chart plates 113 to 119 is formed in a fan shape having a center angle of different radius of about 90 °. Each chart board 11
The surfaces of Nos. 3 to 119 are painted in black and white in the angular direction so as to have substantially equal center angles. In other words, the bright part (white,
(Light part) 113w, 115w, 117w, 119w and dark part (black, dark part) 113b, 115b, 117b, 1
A black and white (grayscale) chart composed of 19b is formed. The light portions 113w, 115w, 117w, 119w and the dark portions 113b, 115b, 117b, 119b divide the chart plates 113, 115, 117, 119 into equal angles, and radial one-dimensional chart images are formed at the radial divisions. Forming edges 113e, 115e, 11
7e and 119e are formed.

The rotating shaft 111 is rotatably supported by two columns 123 fixed to the base 121 so as to be separated from each other in the optical axis direction. Then, the rotation shaft 111, that is, the chart plates 113 to 119 is drive-controlled by the drive device 125 to be freely rotated and stopped at an arbitrary rotation position.
This driving device 125 may be a motor driven by
It may be manually driven by an operator.

Each of the chart plates 113 to 119 has a rotation angle such that each of the chart plates 113 to 119 does not overlap with other chart plates when viewed from the front (the optical system side to be inspected), that is, the edges 113e, 115e ,.
117e and 119e are fixed in a spiral staircase at an angle of 90 °. The distance between the chart plate 113 and the chart plate 119 is set corresponding to the distance between the shortest distance (near point) and the farthest distance (far point) normally observed by the optical system to be inspected, and depending on the optical system to be inspected. When the first and fourth chart plates 113 and 119 are in the equal defocus state, the second and third chart plates 115 and 117 are also in the equal defocus state.
The positions of 5, 117 are also set. The radius of the chart plates 113 to 119 is set in consideration of cost, weight, etc.
Almost proportional to the object distance. For example, chart board 1
The radii of 13 to 119 are R1, R2, R3 and R4, and the object distances of the chart plates 113 to 119 are D1, D2, D3 and D.
When it is set to 4, it is formed to satisfy the following equation. R1 / D1 = R2 / D2 = R3 / D3 = R4 / D4 These may all have the same radius.

FIG. 28 shows a usage state in which the chart device 110 is used for focus adjustment of the endoscope 140. In this embodiment, the distance between the first chart plate 113 and the fourth chart plate 119 is set between the closest position (near point) and the farthest distance position (far point) of the object observed by the endoscope 140. Matched to the spacing.

In the chart device 110, the axis of the rotary shaft 111 is aligned with the optical axis O of the objective lens 141 of the endoscope 140, and the first chart plate 113 is aligned with the near point. In this arrangement, the chart plates 113-119
The light flux reflected by is imaged on the incident end surface of the optical fiber bundle 143 by the objective lens 141, emitted from the exit end surface of the optical fiber bundle 143, and imaged on the CCD image pickup element 147 via the eyepiece lens system 145. Then, it is observed on the display 149 as an image in the state shown in FIG. Each dark part 113b, 115b, 11
7b and 119b images 113b ', 115b', 117
b ', 119b' and bright parts 113w, 115w, 11
7w, 119w 113w ', 115w', 117
The w'and 119w 'are fan-shaped and have substantially the same size and shape. The light receiving surface of the CCD image pickup element 147 and its position correspond to the observation surface of the endoscope 140 at a predetermined distance and its position.

The image thus obtained is displayed on the display 149.
When the image is displayed and observed, the state of the image at each object distance can be observed at the same time, and the focus can be adjusted. Moreover, according to the present chart device 110, the chart plate 11
Since 3 to 119 can rotate around the rotation shaft 111, it is possible to easily change the rotation angle of the chart plates 113 to 119 (change the inclination of the chart image), change the position, rotate, and the like. Also, the optical fiber bundle 143
Is an anisotropic optical system, that is, a hexagonal close-packed structure of a large number of optical fibers, so the state of the image changes depending on the rotational position of the optical fiber bundle 143 around the optical axis. Therefore, the driving device 125 is driven to rotate the chart plates 113 to 119, and the respective chart plates 113 to 119 are stopped at the same position for observation, thereby observing the defocused state or the like under substantially the same conditions for all object distances. You can measure.

In the illustrated embodiment, four chart plates 113 to
Although 119 was used, the number of chart plates is not limited to this. When the defocus state is measured as a set of two, the number of chart plates may be two, or six or more.
When placing one of the chart plates in the focus position,
It is composed of three or an odd number of five or more. When three chart plates are used, the central angle of each chart plate is set to approximately 120 ° (360 ° / 3). That is, when the number of chart plates is n, the central angle of the chart plates is set to about 360 ° / n. However, n is an integer of 2 or more. Then, the respective chart plates are arranged at such an angle that they do not overlap with each other when viewed from the optical axis direction. The chart plates may be formed such that the contours of the respective chart plates in the radial direction overlap each other, or conversely, they may be formed so as not to overlap at all. In addition, each chart plate 113 to 1
19 may be configured to be movable and fixable along the rotating shaft 111.

Although the embodiment applied to the endoscope 140 has been described above, the present invention can be applied to other optical devices.
Further, in this embodiment, the chart image is displayed by the CCD image pickup device 147.
Although it is captured by and displayed on the display 149,
The operator may directly observe the chart image through the eyepiece lens system 145. Alternatively, the images of the chart plates 113 to 119 may be exposed on a film, and observation may be performed based on the image of the film.

30 and 31, the chart plate 11 is shown.
The example which changed the bright-dark edge chart of 3 to 119 into a line chart is shown. In the second embodiment, the edge 11 formed by the light-dark boundary in the first embodiment is used.
3e to 119e are formed by black lines 114 to 120, and FIG. 30 corresponds to FIG. 27 and FIG. 31 corresponds to FIG. 29. In this second embodiment, the edges 113e-1
Similar to the first embodiment except that the line 19e is changed to the lines 114 to 120, the lines 114 to 120 are formed as line images 114 'to 120' which are radial and are equally spaced.

32 to 34 show another embodiment of the present invention. In the third embodiment, the first, second and third chart plates 131, 133 and 135 are formed in a rectangular shape. Each of the chart plates 131 to 135 includes bright portions 131w, 133w, 135w and dark portions 131b, 133b, 135b with a center line at the center in the longitudinal direction sandwiched therebetween, and the edges 131e, 133e, 135e are formed by these divisions. The chart plates 131 to 135 are separated from each other by a predetermined distance in the optical axis O direction, and the first and third chart plates 131 and 135 have edges 131e and 1 with respect to the optical axis O.
In the figure, they are arranged in a stepwise manner with a vertical offset in the direction in which 35e extends. Therefore, the light receiving element 1
On the light receiving surface (imaging surface) of 53, the chart lens images 131 ′ to 135 ′ are vertically arranged from the bottom by the lens 151 to be inspected.
Are formed in this order. The lower sides 131s to 135s of the respective chart plates 131 to 135 and the images 131s' on these image planes.
The relationship with ~ 135s' is as shown in FIGS. 33 and 34. The steps of the chart plates 131 to 135 are regulated as shown by the broken lines in FIG. Further, the edge images 131e 'to 135e' are located on a straight line passing through the optical axis.

In this embodiment, the chart plates 131 to 13 are used.
5 cannot be measured simultaneously on the optical axis O under the same conditions,
Since both are close to the optical axis O, there is practically no problem. For the same reason, the edge images 131e 'to 135e'
Need not be aligned on a straight line as long as they are close to the optical axis O. In this embodiment, the chart plates 131 to 135 are simultaneously imaged within about 30% of the imaging range (observation range) about the optical axis, that is, within the range shown by the broken line in the figure. When the chart plates 131 to 135 are moved toward and away from the optical axis, the chart images 131 'to 135' move, so that a predetermined inspection can be performed at a desired object distance position. By rotating the chart plates 131 to 135 around the optical axis, even if the optical system to be tested is an anisotropic optical system, measurement can be easily performed under the same conditions.

The above chart plate may be of a reflection type, a transmission type, or a self-luminous type, and the positions of light and dark may be opposite to those of the illustrated embodiment. In the illustrated embodiment, the rotation axis 111 and the optical axis O coincide with each other, but the rotation axis and the optical axis do not necessarily have to coincide with each other.

Still another invention relating to a focus evaluation method and apparatus and a focus adjustment method and apparatus will be described below with reference to illustrated embodiments. 35 to 39,
It is a block diagram showing the important section of the whole composition of the focus adjustment device of the endoscope objective optical system to which the present invention is applied. FIG. 35 is a chart plate 251 that forms an edge image by dividing light and dark.
FIG. 36 shows an example in which a chart device that moves in the optical axis direction is used, and FIG. 36 is an example of a device that evaluates the focus of an endoscope using this chart device. In this example,
The image of the chart plate 251 is evaluated based on the blur amount.

Fiberscope 2 for focus adjustment
Reference numeral 10 denotes a fiber bundle 211 in which a large number of optical fibers are bundled in a hexagonal close-packed structure and an end portion 2 on the object side thereof.
The objective lens 215 attached to the lens 12 is provided. The objective lens 215 is fixed in the objective lens fixing cylinder 217, and is attached to the object side end portion 212 of the fiber bundle 211 via the objective lens fixing cylinder 217.

The fiber bundle 211 has an end 2 on the object side.
12 is fixed to the moving stage 233, and the objective lens fixing barrel 217 (objective lens 215) is fixed to the fixing base 235. The moving stage 233 and the fixed base 235 are mounted on a common bench 231.
Can be moved linearly toward and away from the fixed base 235. The objective lens 215 is held on the fixed base 235 so that the optical axis O is parallel to the moving direction of the moving stage 233,
The object-side end portion 212 has a movable stage 23 at a position where the end surface is orthogonal to the optical axis O and the center of the end surface is substantially coincident with the optical axis O.
It is fixed at 3. The fiber bundle 211
The objective lens fixing barrel 217 is fixed to the moving stage 233 and the fixing base 235, respectively, by a clamping means (not shown), for example. The moving stage 233 is configured to be movable electrically by a manual operation dial operation (not shown) or by control of a computer 243 described later.

On the object side of the objective lens 215, a transmission type chart plate 251 illuminated by a rear light source 255 is arranged. The chart plate 251 is divided into two by a light portion 252 that transmits light and a dark portion 254 that does not transmit light, and is oriented in a direction orthogonal to the optical axis O with the edge 253 (the boundary between the light portion 252 and the dark portion 254) being the vertical direction. It is arranged. The chart plate 251 is supported by a chart plate moving mechanism (not shown) and moved in the optical axis direction.
In this embodiment, the chart plate 251 is arranged between the closest object distance (near point), the farthest object distance (far point), and the far point and the near point that are to be observed by the fiber scope 210. Then, it moves to the object distance (middle point) where focusing is planned in design. In this example, the near point is about
The distance is 5 mm, the midpoint is about 11 mm, and the far point is about 111 mm.

An eyepiece 219 is attached to the end 213 of the fiber bundle 211 on the observation system side, and a CCD camera 223 is connected to the eyepiece 219 via a camera adapter 221. The chart plate 251 is imaged on the object side end surface of the fiber bundle 211 by the objective lens 215, and the image is transmitted by the fiber bundle 211 and emitted from the observation system side end surface of the fiber bundle 211. Then, this end face image is the eyepiece lens 219.
The image is converted into an electric image signal by the CCD camera 223 via the, and output to the image input / output device 241. In the normal use state of the fiberscope 210,
An image of the object is formed on the end surface of the object-side end portion 212 of the fiber bundle 211 via the objective lens 215, and this image is transmitted to the end surface of the fiber bundle 211 on the observation system side.
Direct observation through eyepiece 219, or CC
An image is taken by a D camera or the like and displayed on a monitor TV.

The image input / output device 241 converts the image signal into a video signal and displays it on the TV monitor 247, while converting the input image signal into digital image data of a predetermined standard, and an image processing device such as a personal computer. , To a computer 243 such as a workstation. The image input / output device 241 and the computer 243 constitute an evaluation value detecting means (blur amount detecting means) and a target evaluation value setting means (target blur amount setting means).

Of the input image data, the computer 243 samples the horizontal image data in the vicinity of the optical axis O for a plurality of lines in the vertical direction and performs averaging processing to calculate a horizontal light intensity distribution curve. The relationship between the sampling position and the sampling direction of the chart image is shown in FIG. 37, and the intensity distribution is shown in FIG.

In FIG. 38, (A) shows a non-focused state (large defocus), and (B) shows a focused state (small defocus). That is, when the subject is in focus, the outlines of the bright portion image 252i and the dark portion image 254i are clearly formed. Therefore, the edge image 253i, which is a switching of these images, is also clearly formed.
The light intensity in the direction orthogonal to 3i rapidly changes in the edge image 253i. In the non-focus state, the blur width of the edge image 253i increases as the absolute value of defocus increases, so that the change in light intensity in the edge image becomes gentle.

Further, the light intensity distribution curve is calculated by the computer 2
43 differentiates. The differentiation results are shown in FIGS. 39 (A) and (B).
Is shown in the graph. This differential curve shows that the higher the peak value (max) and the narrower the tail of the peak, the smaller the defocus value. In this embodiment, FIG. 39A shows a non-focused state, and FIG. 39B shows a focused state. In these graphs, α is the interval between the two sampling points that fall to the left and right from the peak of the differential curve and first become 0, and β is the two sampling points when the differential value is about ½ of the peak value. Γ is the interval between the points, and γ is the interval between the two sampling points when the differential value becomes about ¼ of the peak value. The smaller the calculated values α, β, and γ, the smaller the defocus amount, that is, the closer to the in-focus state.

Further, the computer 243 calculates the average value m and the standard deviation σ by the above equation 1 and equation 2 using the differential value as a function f (x). The calculated value α, β, γ or σ is used as the evaluation value. Figure 40
6 is a graph showing the relationship between the evaluation value and the distance between the object-side end surface of the fiber bundle 211 and the objective lens 215 (hereinafter referred to as “lens-bundle distance Z”). This graph represents that the peak position of the evaluation value is the in-focus position.

The moving stage 233 is moved to move the lens-
While changing the bundle interval Z stepwise or continuously, the evaluation value is obtained stepwise or continuously by the above arithmetic processing, and the result is displayed on the display 245. This process is repeated on the chart plate 251 at the near point, the intermediate point, and the far point.

FIG. 41 shows the relationship between the evaluation value and the distance Z between the fiber bundle 211 and the objective lens 215 thus obtained. Here, the standard deviation σ described above is used as the evaluation value. In this graph, the smaller the evaluation value, the smaller the defocus and the better the image performance. In the figure, symbol (a) represents the average value of evaluation values for near points, (b) represents the average value of evaluation values for intermediate points, and (c) represents the average value of evaluation values for far points.

According to the conventional focus adjustment method, the defocus amounts (absolute values) at the far point and the near point are equalized, or the defocus amount is minimized at the intermediate point. . When this conventional adjustment criterion is applied to the graph of FIG. 41, the best lens-bundle distance P1 is about 625 μm.

On the other hand, when evaluated by the eyes of the person who actually operates, the evaluation distribution is as shown by the curve H, and the best lens-bundle distance H1 according to the eyes is obtained.
Is about 600 μm. The present invention enables the focus adjustment as close as possible to the human visual sense. In this embodiment, the evaluation value (a1) for the near point is the largest,
Then, the evaluation value (b1) for the far point and the evaluation value (c1) for the intermediate point become the smallest, and the focus adjustment is performed with the image performance being emphasized in the order of the intermediate point, the far point, and the near point. This places greater importance on the far distance side than the adjustment based on the conventional adjustment standard.

In this embodiment, the evaluation values (a1, b1, c1) based on this human evaluation are set as the target evaluation values. Then, for each endoscope to be inspected, the moving stage 233 is moved so that the measured evaluation value approaches the target evaluation value, and focus adjustment is performed. In the present invention, the image performance can be adjusted by focusing on the near point rather than the far point, while setting the target evaluation value, in contrast to the above embodiment.

Now, assuming that the lens-bundle spacing is the value indicated by P2 (about 575 μm), the evaluation value for the near point is larger than a1, the evaluation value for the intermediate point is larger than b1, and the evaluation value for the far point is. The evaluation value is smaller than c1.
From these magnitude relationships and the shapes of the average values a, b, and c, it becomes clear whether the lens-bundle spacing is made smaller or larger. In the case of this embodiment, the value of a becomes smaller as the lens-bundle spacing is increased. Similarly, the value of c increases as the lens-bundle spacing increases.
Therefore, it can be seen that the interval may be larger than the current interval P2. By repeating this operation, each evaluation value approaches the target evaluation values a1, b1, c1, and as a result, the best lens-bundle distance H1 can be achieved.

Note that, in FIG. 41, a, b, and c are shown by taking into account the error ± α ′ that occurs in the evaluation value measurement at the same interval due to the measurement error or the like. Because of this error ± α ',
In the case of the present embodiment, there is a possibility that an error with an interval of about the width shown as the total error may occur. However, since the width of this error is within the range of the human evaluation curve H, it can be seen that the accuracy is sufficient.

FIG. 42 shows a chart apparatus in which the chart plates placed at the near point, the intermediate point and the far point are separately formed, and the chart plates placed at the respective points are simultaneously imaged on the image forming plane of the optical system under test. An example is shown. In this embodiment, the end of the fiber bundle 271 on the object side and the objective lens 27 are
3 is attached to the endoscope assembling jig 275, and at the observation side end portion, although not shown, similarly to the embodiment shown in FIG. 36, the eyepiece lens 219, the adapter 221 and the CCD camera 2 are provided.
23 is attached. The CCD camera 223 is connected with focus evaluation means including an image input / output device 241, a computer 243, a display 245, a TV monitor 247, and the like. In addition, the assembly jig 275
Although not shown in detail, the objective lens 273 and the fiber bundle 2 are similar to those of the microstage shown in FIG.
The distance between the object 71 and the end surface on the object side can be adjusted.

In this embodiment, three chart plates 261 and 26, which are sequentially formed larger for the near point, the intermediate point and the far point, are formed.
2, 263 are arranged at the near point, the middle point and the far point. The midpoint chart plate 262 is arranged at a position where its center passes through the optical axis 0, and the near point and far point chart plates 261 and 26 are arranged.
Reference numerals 3 are arranged so as to be vertically offset from the optical axis O, respectively. Each chart plate 261, 262, 263 is shown in FIG.
5 is a transmission-type bright and dark chart plate similar to the chart plate 251 shown in FIG.

A light source 264 is arranged at an offset position behind the chart plates 261, 262, 263. The light source 264 reduces the optical path length difference to the chart plates 261, 262, 263 so that the chart plates 261, 262, 263.
In order to equalize the brightness of
1, 262 illuminate directly, and the far point chart plate 263 illuminates by reflecting off the mirror 265.

The chart plates 261, 262, 263 illuminated and transmitted by the light source 264 are imaged on the object side end surface of the fiber bundle 271 by the objective lens 273. The state of the image formation is shown in FIG. As can be seen from this figure, the midpoint chart plate 262 is located approximately in the center of the image plane.
Image 262i is formed, an image 261i of the near point chart plate 261 is formed under the image 262i, and an image 263i of the far point chart plate 263 is formed on the image 262i.
These images 261i to 263i are picked up by the CCD camera 223, and for each of the images 261i to 263i,
The intensity distribution, differential curve, and evaluation value are obtained by sampling and averaging in the horizontal direction (horizontal direction).

Using this evaluation value, the focus adjustment of the endoscope objective optical system to be inspected is performed. That is, the objective optical system of the endoscope to be inspected is set to obtain an evaluation value, and the fiber bundle 71 is moved based on the evaluation value and a preset target evaluation value to adjust the focus.

In the embodiments shown in FIGS. 35 and 42, the present invention is applied to an endoscope using a fiber bundle for the objective optical system, but a CCD is used instead of the fiber bundle.
The present invention can also be applied to focus adjustment of an objective optical system of an electronic endoscope using a light receiving element such as. In this case, CC
The relationship between D and the objective lens is the same as in FIG.

45 and 46 show an embodiment for adjusting the focus of the pan-focus camera. FIG.
5 is an example applied to a compact camera using a silver salt film. Note that the taking lens 302 is not fixed to the camera body 301, and can be moved in the optical axis direction from a designed fixed position. In this embodiment, the camera body 301 is attached to the moving stage 28 of the micro stage 281.
2, the photographing lens 302 is fixed to the fixed base 283, and the moving stage 282 is moved toward and away from the fixed base 283 to move the photographing lens 302 and the camera body 30.
Adjust the distance from 1 (film surface).

In the compact camera 301, a CCD image pickup device (detector) 303 is arranged with its case back opened. The CCD image pickup device 303 is fixed to the moving stage 282 by the sensor holder 304 with the light receiving surface of the CCD image pickup device 303 aligned with the film surface of the compact camera 301.

Further, in front of the taking lens 302, chart plates 291 and 292 are arranged at near and far points. The structure of the chart plates 291 and 292 is the same as that of the chart plate 2
51, but in this embodiment, the near point chart plate 291 is arranged at a position where its upper side overlaps the optical axis O, and the far point chart plate 292 is arranged at a position where its lower side overlaps the optical axis O. is there. Therefore, these chart plates 291, 2
In the image forming plane 92, the image of the near point chart plate 291 is below the center and the image of the far point chart plate 2 is above the center.
92 images are formed.

The images of the chart plates 291 and 292 incident on the CCD image pickup device 303 through the taking lens 302 are C
It is converted into an electric signal by the CD image pickup device 303 and inputted to the computer 286 via the image input / output device 285. Then, the evaluation value is calculated by the computer 286, and is graphed and displayed on the display 287 as shown in FIGS. 41 and 42, for example. Then, based on the preset target evaluation values of the near point chart image and the far point chart image and the measurement evaluation value, the photographing lens-film interval is changed to perform focus adjustment.

FIG. 46 shows an example applied to a surveillance camera equipped with a CCD image pickup device. In this embodiment, the body 311 of the surveillance camera is fixed to the moving stage 282, and the taking lens 212 is fixed to the fixed base 283. Then, the moving stage 282 is moved to move the taking lens 212 and the CCD.
The interval (focus) with the image sensor 313 is adjusted. The configurations of the chart plates 291, 292, the image input / output device 385, the computer 286, and the display 287 are similar to those shown in FIG.

In the embodiment shown in FIGS. 45 and 46,
An evaluation value is obtained based on the chart plates 291 and 292 placed at the near point and the far point, and focus adjustment is performed based on the measured evaluation value and a preset target evaluation value. With this focus adjustment, a well-balanced focus adjustment can be performed from a distance to a near distance.

As described above, in this embodiment, the blur amount of the chart image is evaluated by the intensity distribution of the edge image and its differential value and its standard deviation, but the present invention is not limited to this.
You may evaluate by the magnitude of the amount of waste. Regarding the setting of the target evaluation value, one or a plurality of reference lenses are set, and a lens-bundle distance adjustment operation is performed by a person, and the evaluation value at that time is set as the target evaluation value. Alternatively,
The lens-bundle distance may be calculated from the design value and adjusted, and the evaluation value at that time may be used.

Still another focus evaluation / adjustment method and an apparatus for implementing these methods will be described based on the illustrated embodiment. FIG. 47 shows an embodiment of an apparatus for carrying out the focus evaluation method and the focus adjustment method of the present invention.
0 is another embodiment of the apparatus for carrying out the method of the present invention. FIG. 47 shows an endoscope 41 which is one of the imaging optical systems to be inspected.
0, the focus state (position) of the objective lens 415 is evaluated,
FIG. 50 shows an objective lens 41 of the endoscope 410, which is a focus adjusting device for performing focus adjustment based on the evaluation value.
It is an apparatus for evaluating the focus state of No. 5. Of course, the present invention can be applied to an optical device having an imaging optical system other than an endoscope.

First, the main structure of the embodiment shown in FIG. 47 will be described. In the endoscope 410, the tip portion 413 of the optical fiber bundle 411 is fixed to the moving stage 423 of the micro stage 421, and the tip portion 413 is moved in a direction orthogonal to the incident end surface 413a. Tip 4
The objective lens 415 fixed to No. 13 is integrally fixed to the micro stage 421 and supported by the objective lens fixing member 425. That is, the distance between the objective lens 415 and the incident end surface 413a is adjusted by moving the moving stage 423. Although not shown, the objective lens 415 is fixed to a lens barrel slidably fitted in the tip portion 413, and is fixed to the tip portion 413 via this lens barrel.

On the object side of the objective lens 415, three chart plates 427 (471, 472, 473) are arranged at different object distances, and at the same time formed so as to form an image on the incident end face 413a. Has been done. That is,
A near chart plate 471 located closest to the objective lens 415 and above the optical axis O, and the objective lens 415.
It is provided with a distant chart plate 472 located farthest away from the optical axis O and an intermediate chart plate 473 located between them and orthogonal to the optical axis O. The near chart plate 471 and the far chart 472 are located apart from each other before and after the object position where the best focus is desired. Further, as shown in FIG. 48, these chart plates 427 are edge charts that have a rectangular outer shape and are divided into a translucent portion and a light shielding portion that are milky white from the center to the left and right. The shape of the chart plate and the mode of the chart are not limited to this embodiment.

The near and intermediate chart plates 471 and 473 are
Illuminated by the light source 431, the far chart 472 is illuminated by the light source 435. Illumination light emitted from the light source 431 is guided by the optical fiber bundle 432, and is closer to the intermediate chart plates 471 and 47 by the irradiation lens 433.
Illuminate 3. The light source 435 illuminates the far chart plate 472 from behind. The illuminating means is not limited to the illustrated embodiment as long as it can illuminate the near and far intermediate chart plates 471, 472, 473.

Images 471i and 472 of the respective chart plates 471, 472 and 473 illuminated by these light sources 31 and 35.
i and 473i are moved to the front end portion 413 by the objective lens 415.
As shown in FIG. 49, the light-incident end surface 413a is formed at the lower, upper, and middle positions with the optical axis O as the center.

The chart images 471i, 472i, 473i formed on the incident end surface 413a are guided by the optical fiber bundle 411 and emitted from the eyepiece lens 417 attached to the other end of the optical fiber bundle 411.
The eyepiece lens 417 is connected to the CCD camera 443 via the connector 441, and an image of the incident end surface 413a is captured. The image captured by the CCD camera 443 is input to the computer (calculation unit) 447 via the image input / output interface 445.

The computer 447 samples the images of the near, far, and intermediate chart plates 471, 472, and 473 in the horizontal direction (X-axis direction) in the same manner as the embodiment described above with reference to FIG. In the intensity data distribution of the sampled light and dark, for example, the intensity curve, the boundary between the bright portion and the dark portion changes rapidly in the focused state.

By differentiating this intensity curve, the rate of change at the light-dark boundary is obtained (see FIG. 39). The focus evaluation value is obtained from the information about the height of the change rate curve or the width of the skirt. 38 and 39, (A) shows a non-focused state, and (B) shows a focused state.

The focus evaluation value is obtained for each chart plate 427. Further, the tip portion 413 is moved toward and away from the objective lens 415 to move the incident end surface 413a and the objective lens 41.
The distance from 5, that is, the focus adjustment amount is changed. And
The above calculation is repeated for each different focus adjustment amount, and each chart plate 471, 472, 47 at a plurality of focus adjustment amounts.
A focus evaluation value for each 3 is calculated. This focus evaluation value is displayed on the display 449 or the monitor TV 451, for example.
It is displayed as the graph shown in FIG.

The measuring device shown in FIG. 47 does not move.
Although the chart plates 471, 472, 473 are used,
The measuring apparatus shown in FIG. 50 is different from the first measuring apparatus in that one chart plate 428 is moved to near, intermediate and distant positions. Since other configurations are similar to those of the first device, only main parts are shown. That is, the eyepiece lens 417 is attached to the other end of the optical fiber bundle 411 as in the embodiment shown in FIG. 47, and the eyepiece lens 417 is
It is connected to the CCD camera 443 via the adapter 41. The image captured by the CCD camera 443 is input to the computer 447 via the image input / output interface 445.

An embodiment of the focus evaluation method and focus adjustment method of the present invention using the measuring apparatus shown in FIG. 47 will be described with reference to FIGS. 51 to 59. In this embodiment, first, near, far and intermediate chart plates 47 are provided.
1, 472, 473 images 471i, 472i, 473
The i is imaged a plurality of times by changing the interval (focus adjustment amount) between the objective lens 415 and the end surface 413a, and the focus evaluation value is calculated for each focus adjustment amount. 51 is a drawing of an evaluation value curve with the focus adjustment amount on the X axis and the focus evaluation value on the Y axis.
As shown in. This evaluation value curve indicates that the lower the value on the Y-axis, the higher the evaluation.

Here, the curve drawn by the evaluation value for the near chart plate 471 is y1 = f1 (x), and the far chart plate 4 is
The curve drawn by the evaluation value for 72 is y2 = f2 (x), and the curve drawn by the evaluation value for the intermediate chart plate 473 is y3 =
Let f3 (x). The position of the intermediate chart plate 473 is at or near the best position.

In the endoscope 410 to be inspected, the focus adjustment amount preferred by the user is the intersection point (x1, y ₂₁ = y ₁₁ ) of the near evaluation value curve and the far evaluation value curve, and the midpoint evaluation value curve. It was found to be in between the intersection of distant evaluation value curve _{(x2, y 22 = y 32} ). Therefore, the present invention focuses on this section,
Interval [x2, x1] that is the distance between the intersections in the X-axis direction
Are evaluated value curves y1 = f1 (x), y2 = f2 (x),
Calculated from y3 = f3 (x). That is, f1
The focus adjustment amounts x1 and x2 at the points where (x) = f2 (x) and f2 (x) = f3 (x) hold are obtained.

The interval [x2, x1] obtained in this way
It can be seen that the desired focus adjustment amount x is included in the above. By narrowing the focus adjustment range to this section [x2, x1], the focus evaluation and focus adjustment of the test imaging optical system can be performed easily and quickly.

In one embodiment of the present invention, the total focus evaluation value S is obtained from the focus adjustment amount x within the section [x2, x1]. On the contrary, when the comprehensive evaluation value S is clear,
The focus adjustment amount x to be adjusted can also be obtained by inverse calculation.

A method of obtaining the total evaluation value S from the focus adjustment amount x will be described with reference to FIGS. 51 to 53. When the focus adjustment amount x is determined, the focus evaluation values y1, y2, y3 for each chart plate 427 are calculated. Overall evaluation value S
Can be obtained as S = g (y1, y2, y3) by a function g using these three focus evaluation values y1, y2, y3. The function g can be defined as, for example, the following three expressions (1), (2) or (3). g = (y1-y2) / (y2-y3) (1) g = (y2-y3) / (y1-y3) (2) g = y3 / y2-y2 / y1 (3) By using the comprehensive evaluation value function S = g (y1, y2, y3), the overall evaluation value S of the focus at a certain focus adjustment amount x can be obtained.

In the present invention, the function g (y1, y2, y3) using y1, y2, y3 other than the above (1), (2), and (3) is used.
Can also be applied.

In the above embodiment, the three chart plates 47 are used.
Although 1, 472 and 473 are used, the present invention is not limited to this, and the number of chart plates may be two or four or more. If the number of chart plates is N (integer of 2 or more), the evaluation value yn (n = 1 to N) is calculated for each chart plate, and the comprehensive evaluation value function is calculated based on the N evaluation values yn. The total evaluation value S is obtained by S = g (y1, y2, ..., Yn, ..., YN).

The above is the method of obtaining the total evaluation value S from a certain focus adjustment amount x, but conversely, the desired total evaluation value S is obtained in advance, and the focus adjustment amount x is calculated based on that total evaluation value S. Can be asked. For example, the reference optical system is used to adjust the focus by a reference person, and the desired comprehensive evaluation value S is obtained. This comprehensive evaluation value S
Is set as the standard comprehensive evaluation value S0,
The focus adjustment target value x0 is calculated based on
The focus of the endoscope 410 to be inspected is adjusted by the focus adjustment target value x0 calculated.

A focus adjusting method for adjusting the focus of the endoscope 410 to be inspected corresponding to the reference optical system by using the reference comprehensive evaluation value S ₀ will be described. Here, the known data is only the reference comprehensive evaluation value S ₀ . Therefore, by changing the focus adjustment amount x of the endoscope 410 to be inspected, the evaluation value y for each chart plate 427 at different focus adjustment amounts x is obtained.
Calculate 1, y2 and y3.

Evaluation values y1, y2, y3 thus obtained
The section focus adjustment amounts x1 and x2 are determined based on the following, and the functions f1 and f2 for the respective chart plates 471, 472 and 473 in the focus adjustment section [x2, x1],
Calculate f3. If the value of the function f1, f2, f3 is Sadamare, g (x) = by S ₀ is calculated back focus adjustment amount x which satisfies, is obtained focus adjustment target value x _0. If the focus adjustment target value x ₀ is obtained, the focus adjustment of the endoscope 410 to be inspected is performed based on this. As a matter of course, the comprehensive evaluation value function g used when the reference comprehensive evaluation value S ₀ is obtained,
It must be the same as the total evaluation value function g used for back calculation.

In the focus adjustment section [x2, x1] used for obtaining the function f, the point where the distance evaluation value and the distance evaluation value match, and the point where the intermediate evaluation value and the distance evaluation value match. It does not have to be between. For example, as in the section [x2 ', x1'] of the endoscope under examination shown in FIG. 53, y ₃₂ ′ ≠
This is the case where y ₂₂ ′ and y ₁₁ ′ ≠ y ₂₁ ′.

Since the function f can be defined even in the case of the section [x2 ', x1'] in FIG. 53, the comprehensive evaluation value S can be used. Here, the function f in FIG.
Is the same as the function f in FIG. 51 except that the sections are different.

As described above, according to the focus adjustment method of this embodiment, the focus adjustment amount by which the total evaluation value S becomes equal to the reference total evaluation value S ₀ even when the near, distant, and middle evaluation value curve characteristics are different. Therefore, it is possible to easily adjust the balance of the perspective state by the objective lens 415 to be inspected.

In the focus adjusting method described above, the function f is obtained by changing the focus adjusting amount x within a predetermined section. According to this adjusting method, the evaluation values y1, y2,
The accuracy is improved because y3 is calculated, but it takes a relatively long time.

Therefore, an embodiment in which the accuracy is suppressed within the allowable range and the adjustment time can be shortened will be described with reference to FIGS. 54 and 55. 54 and 55 are graphs obtained by linearly approximating the focus adjustment section [x2, x1] based on the evaluation value data obtained in FIG. Here, the focus adjustment section [x
[2, x1], the focus adjustment amount x is not changed to calculate the evaluation values y1, y2, y3.
, X1], and the evaluation values y1, y2, y3 at both end points are connected by a straight line, and this is used as an approximate expression of the function f. For example, in FIG. 55, two points _{(x1, y 11), (} x2, y
_{Since a} straight line passing through ₁₂ ) is determined, the function f '
You get 1. Similarly, the functions f'2 and f'3 are obtained. According to this method, the point x1 at which the distant evaluation value y2 and the near evaluation value y1 match and the point x2 at which the intermediate evaluation value y3 and the distant evaluation value y2 match are calculated or calculated on a graph. The functions f'1, f'2, f'3 can be obtained.

If the functions f'1, f'2 and f'3 are determined,
The focus adjustment amount x for which g (x) = S ₀ holds is calculated back to obtain the focus adjustment target value x ₀ , and the focus adjustment of the endoscope 410 to be inspected can be performed based on this.

Further, also in the case of this method, as shown in FIG. 55, it is understood that the focus adjustment section does not have to be the point where the evaluation values y1, y2 and y3 coincide. However, if the focus adjustment section becomes too long, the deviation between the actual curve and the approximated straight line becomes large, and the accuracy may decrease.
However, the section [x1 ', x shown in the figure obtained in this embodiment is
If it is about 2 '], it is within the error range. In this case, the method of obtaining the total evaluation value S and the method of calculating backwardly the focus adjustment amount are the same as the methods shown in connection with FIGS.

Next, an example of the focus evaluation method will be described. Since this is an evaluation method performed on the product with the imaging lens fixed after the focus adjustment, it can be performed by the device shown in FIGS. 47 and 50 without using the focus adjustment device.

With this focus evaluation method, the function f cannot be obtained directly, but since the evaluation values y1, y2, y3 can be obtained, the total evaluation value S can be calculated. Then, by comparing the reference comprehensive evaluation value S ₀ at the time of focus adjustment with the obtained comprehensive evaluation value S, it can be determined whether or not the focus position is deviated. 56 to 58 show the above expressions (1), (2) and (3) as the function g for obtaining the total evaluation value S.
It is the figure which showed the relationship between the focus adjustment amount x and comprehensive evaluation value S when using. Also, FIG.
It is the figure which expanded the vertical axis of the graph.

Using the equation (1), the total evaluation value S is x = x
It becomes a hyperbola with 2 as an asymptote, and when x> x0, S <-1 x = x0, S = -1 x1>x> x0, 0>S> -1 When x = x1, S = 0 x1> When x> x2, S> 0. When x1 <x2, S <0.

Using the equation (2), the total evaluation value S is x = x
It is a hyperbola with 1 as an asymptote, and when x> x ₀ , S <0 x1>x> x ₀ , S> 1 When x = x1, S = 1 x1>x> x2 When S> 0 x = x2 In case of S = 0, and in case of S <x2, S <0.

When the equation (3) is used, the total evaluation value S is a decreasing function, and has a value of about 0.5 to -0.4 in the section [x2, x1]. In this case, the allowable range of the comprehensive evaluation value S is 0.
Assuming 3 to −0.2, if there are evaluation values y1, y2, y3 in which “•” is plotted in FIG. 58, S = 0.2.
Therefore, it can be evaluated that the focus state of this optical system is within the allowable range. As described above, the same function g is used when adjusting and evaluating the focus, but the same applies to the combination of chart positions.

In the above embodiment, the case where the intermediate chart is arranged near the best position has been described. However, since the intermediate chart only needs to be between the far chart and the near chart, either the far chart or the near chart is used. It is also possible to arrange it at a position close to. FIG. 59 shows the evaluation value at that time. In this case, the focus adjustment amount x that determines the reference total evaluation value S ₀ is outside the section [x2, x1], but the section [x2
It is possible to extend the function g obtained by [2, x1] outside the interval. When the equation (2) is used as the function g, the reference total evaluation value S ₀ becomes negative, and therefore the focus adjustment and the focus evaluation can be performed by the above-described method based on this.

As described above, in this embodiment, one total evaluation value is obtained by calculating from the three evaluation values based on the near, far, and intermediate charts, and the focus adjustment amount and the focus are calculated based on this total evaluation value. Evaluating position. Therefore, even if the three evaluation values of the lens under test deviate from the reference evaluation values,
Accurate focus evaluation and focus adjustment are possible.

[0134]

As is apparent from the above description, according to the present invention described in claim 1, since there is no influence by the magnification, it is possible to easily perform evaluation regardless of the optical system to be tested. Further, since the edge image is differentiated to obtain the LSF and the evaluation value is obtained from this, the calculation time can be reduced. According to the invention described in claim 12, even in an optical system having a periodic structure such as an optical fiber bundle, the optical system is evaluated in a short time without being affected by the periodic structure, and the focus adjustment is performed based on this evaluation. And so on.

According to the thirtieth aspect of the present invention, it is possible to easily obtain a necessary chart image without being affected by a change in magnification of the test optical system, a chart orientation, and anisotropy of the test optical system. Therefore, the focus adjustment of the optical system and the image performance at different object distances can be evaluated and inspected easily and quickly.

According to the forty-fifth aspect of the invention, in the focus adjustment of the pan-focus optical system, target values are set for the blur amounts of the images of the chart members placed at different subject distances, and the measured blur amount is set in advance. Since the focus is adjusted so as to approach the set target value, a well-balanced focus evaluation can be easily performed from a distance to a near distance.

In the present invention as defined in claims 57 and 72, one comprehensive evaluation value can be obtained from a plurality of evaluation values for the chart means at a plurality of different object distances by calculation. Even if there are variations, a constant focus balance can be evaluated. In the invention described in Item 59, since the comprehensive evaluation value is calculated based on the chart plates at three different object distances, the focus can be evaluated in a shorter time. According to a sixty-fifth aspect of the present invention, a plurality of focus evaluation values are obtained while adjusting the focus of the imaging optical system to be measured with respect to the chart means at different object distances, and the plurality of focus evaluation values are obtained. Since it is possible to calculate the focus adjustment target value, that is, the focus adjustment amount to be adjusted based on the reference comprehensive evaluation value obtained in advance based on the actual measurement comprehensive evaluation value for the imaging optical system to be tested in the same manner, By adjusting the test imaging optical system based on this focus adjustment target value, optimum focus evaluation and adjustment with excellent perspective balance can be easily performed. In the invention described in Item 67, since the focus adjustment target value can be obtained by calculation in the same manner as in Item 65 for the chart means at three different object distances, the optimum focus adjustment can be performed more easily. You can

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a configuration of an optical system to be inspected evaluated by an image plane position evaluation method of the present invention.

FIG. 2 is a diagram showing an example of a configuration of an optical system to be inspected, which is evaluated by the image plane position evaluation method of the present invention.

FIG. 3 is a diagram showing an example of a configuration of an optical system to be inspected, which is evaluated by the image plane position evaluation method of the present invention.

FIG. 4 is a diagram showing an example of a configuration of an optical system to be inspected, which is evaluated by the image plane position evaluation method of the present invention.

FIG. 5 is a diagram showing an example of a chart used for carrying out the present invention.

FIG. 6 is a diagram showing an example of a chart used for carrying out the present invention.

FIG. 7 is a diagram illustrating an image of a chart and a sampling direction in the example of the present invention.

FIG. 8 is a graph showing an intensity distribution of a chart image.

9 is a graph showing a differential value of the intensity curve shown in FIG.

FIG. 10 is a graph showing a differential value of an intensity curve.

FIG. 11 is a graph showing a transition of the evaluation value obtained from the differential value graph with respect to the movement amount of the optical system.

FIG. 12 is a graph showing the transition of the evaluation values of the examples shown in FIGS. 3 and 4 with respect to the movement amount of the optical system.

FIG. 13 is a block diagram showing a circuit configuration of the present invention.

FIG. 14 is a diagram showing an example in which the present invention is used for evaluation of an endoscope.

FIG. 15 is a diagram showing an image forming state according to the embodiment.

FIG. 16 is a diagram showing an image formation state according to the embodiment.

FIG. 17 is a diagram showing an image formation state according to the same example.

FIG. 18 is a diagram for explaining a state of image transmission according to the same embodiment.

FIG. 19 is a diagram illustrating a manner of image transmission according to the same embodiment.

FIG. 20 is a diagram showing a state in which image averaging is performed in a direction in which edges of an edge image extend in the same example.

FIG. 21 is a graph showing an intensity curve of an edge image of the same example.

FIG. 22 is a diagram illustrating a smoothing mode of the example.

FIG. 23 is a graph showing an intensity curve of an edge image after smoothing.

FIG. 24 is a graph showing a differential value of an intensity curve of an edge image.

FIG. 25 is a graph showing a differential value of an intensity curve of an edge image.

FIG. 26 is a graph showing the MTF by Fourier transforming the same differential value.

FIG. 27 is a front view showing an example of the radial chart plate of the present invention related to the chart device.

FIG. 28 is a side view showing a usage state of a chart device including the chart plate.

FIG. 29 is a diagram showing an appearance of an image of the chart device.

FIG. 30 is a front view showing a second embodiment of the chart plate.

FIG. 31 is a diagram showing an image aspect of the second example.

FIG. 32 is a perspective view showing a third embodiment of the chart plate of the present invention.

FIG. 33 is a side view of the third embodiment.

FIG. 34 is a side view showing an appearance of an image of the chart device according to the third embodiment.

FIG. 35 is a block diagram showing an outline of another embodiment of a chart device and a focus adjustment device to which another focus evaluation method and adjustment method of the present invention are applied.

FIG. 36 is a block diagram showing an embodiment of a control system for performing focus evaluation and adjustment of the endoscope by the chart device and the focus adjustment device.

FIG. 37 is a diagram illustrating a chart image and a sampling state in the example.

FIG. 38 is a diagram showing a light intensity distribution in the sampling direction of the chart image.

FIG. 39 is a graph showing a differential value of a light intensity curve.

FIG. 40 is a graph showing the relationship between the distance between the objective lens and the image plane and the focus evaluation value.

FIG. 41 is a graph illustrating the relationship between the evaluation value and the target value of each chart image placed at different object distances.

FIG. 42 is a schematic diagram showing an embodiment in which chart plates placed at different object distances are formed so as to form images on the light receiving surface of the optical device in a non-overlapping state.

FIG. 43 is a perspective view showing the configuration of the chart plate.

FIG. 44 is a diagram showing an imaged state on the light receiving surface of each chart plate.

FIG. 45 is a diagram showing an example of performing focus adjustment of a pan-focus compact camera according to the present invention.

FIG. 46 is a diagram showing an example of performing focus adjustment of a pan-focus monitoring camera.

FIG. 47 is a diagram showing an example of a measuring apparatus for carrying out the focus evaluation method and the focus adjustment method of the present invention.

FIG. 48 is a perspective view showing a structure of a chart plate of the measuring apparatus.

FIG. 49 is a diagram showing an image state of the chart plate formed by the endoscope under test in the measuring apparatus.

FIG. 50 is a diagram showing an example of a measuring apparatus for carrying out the focus evaluation method of the present invention.

FIG. 51 is a graph showing the relationship between the evaluation value of the endoscope to be inspected and the focus adjustment amount evaluated by the method of the present invention.

FIG. 52 is a graph showing the relationship between the evaluation value and the focus adjustment amount of the endoscope under test.

FIG. 53 is a graph showing the relationship between the evaluation value and the focus adjustment amount of the subject endoscope.

FIG. 54 is a graph obtained by linearly approximating each evaluation value in the section [x ₂ , x ₁ ] in FIG. 52;

FIG. 55 is a graph in which each evaluation value in the section [x _{2 ′} , x _{1 ′} ] shown in FIG. 53 is linearly approximated.

FIG. 56 is a graph showing an example of the relationship between the evaluation value of the endoscope to be inspected and the focus adjustment amount evaluated by the method of the present invention.

FIG. 57 is a graph showing the relationship between the total evaluation value obtained from the evaluation values of each chart and the focus adjustment amount.

FIG. 58 is an enlarged view showing the vertical axis of the graph.

FIG. 59 is a graph showing still another example of the relationship between the evaluation value of the endoscope to be inspected and the focus adjustment amount evaluated by the method of the present invention.

[Explanation of symbols]

 11 chart plate 11i chart plate image 12 bright part 13 edge part 13i edge image 14 dark part 17 image sensor 19 sampling circuit 21 computing means 23 display device 25 evaluation means 31 first imaging lens 33 optical fiber bundle 35 second imaging lens 41 Transmission type chart member 45 Reflection type chart member 51 Objective lens 53 Optical fiber bundle 53a Incident end face 53b Emission end face 55 Eyepiece lens group 110 Chart device 111 Rotating shaft 113 Chart plate 113e Edge 114 line 115 Chart plate 115e Edge 116 line 117 Chart plate 117e Edge 118 Line 119 Chart plate 120 Line 131 Chart plate 133 Chart plate 135 Chart plate 140 Endoscope 141 Objective lens 143 Fiber Bundle 145 Eyepiece 147 CCD image sensor 210 Fiberscope 211 Fiber bundle 215 Objective lens 219 Eyepiece 223 CCD camera 231 Microstage 241 Image input / output means 243 Computer 245 Display 247 TV monitor 251 Chart board 255 Light source 281 Microstage 285 Image input / output Device 286 Computer 287 Display 301 Compact camera body 302 Photographing lens 303 CCD image pickup device 311 TV camera body 312 Photographing lens 411 Optical fiber bundle 413 Tip part 413a Incident end face 415 Objective lens 417 Eyepiece 421 Microstage 423 Moving stage 425 Objective lens fixing member 428 Chart board (near, middle, far Chart board) 431 light source 435 light source 443 CCD camera (photoelectric conversion means) 447 computer (image analysis means) 449 display 451 monitor TV 471 near chart board 472 distant chart board 473 middle chart board

 ─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. 6-137448 (32) Priority date Hei 6 (1994) June 20 (33) Priority claim country Japan (JP)

Claims (72)

[Claims] 1. A chart member capable of forming an edge image, an optical system for forming an image of the chart member, and a position arranged at or near a position where an edge image of the chart member is formed by the optical system. Focus evaluation of an optical system, comprising: light receiving means for converting an edge image into an electric signal; and sampling means for sampling an electric signal output by the light receiving means in a direction intersecting with the edge image. apparatus. 2. The evaluation device according to claim 1, further comprising arithmetic means for calculating a line spread function (LSF) by differentiating an electric signal concerning the light amount distribution sampled by the sampling means in the sampling direction. A focus evaluation device for an optical system. 3. A step of forming an edge image of a chart member on a light receiving means or its vicinity by an optical system, and a sampling step of sampling a light amount distribution of an image received by the light receiving means in a direction intersecting with the edge image. Calculating the line spread function (LSF) by differentiating the sampled light amount distribution in the sampling direction. 4. The method according to claim 3, comprising the step of calculating an imaging state evaluation value based on the LSF.
A focus evaluation method for an optical system, characterized by: 5. The optical system according to claim 4, wherein the LSF peak value is sandwiched, and the interval between sampling points at which the relative value to the peak value is a specific value is set to a good LSF width. System focus evaluation method. 6. The optical system according to claim 4, wherein a good LSF width is provided by a distance between two sampling points that are left and right from the peak value of the LSF and first become 0. Focus evaluation method. 7. The optical system according to claim 4, wherein the width is defined as an interval between two sampling points that drop before and after the peak value of the LSF and become ½ of the peak value first. Focus evaluation method. 8. The LS as the evaluation value according to claim 4.
Calculating a standard deviation of F; 9. The focus evaluation method for an optical system according to claim 5, wherein a standard deviation of LSF is calculated in the width section as an evaluation value. 10. The chart according to claim 4, wherein:
A focus evaluation method for an optical system, which comprises arranging at a desired position on the object field side for evaluation. 11. The focus evaluation method for an optical system according to claim 4, wherein the light receiving means is moved in the optical axis direction, and a position having the smallest evaluation value is set as a best image plane position. 12. A step of forming an edge image of a chart member on a light receiving means or its vicinity by an optical system, a sampling step of sampling a light quantity distribution in a direction intersecting the formed edge image, and an image field. Output from the light receiving means based on a chart in which two points on the object field side that are conjugate with two points on the image field side that are equidistant from the expected best image plane position are set at one or more positions as one set. And a step of evaluating an image plane position based on a signal, the focus evaluation method for an optical system. 13. The focus evaluation method for an optical system according to claim 12, wherein the two points are a long-distance point and a short-distance point observed by the optical system. 14. The best image plane position according to claim 12, wherein the light receiving means is moved in the optical axis direction, and a point at which the evaluation values of the edge images of the chart member placed at the respective points become substantially equal to each other, A focus evaluation method for an optical system, characterized by: 15. An evaluation apparatus for an optical system including an optical element having a periodic structure, comprising: a chart member forming an edge image; and a position at or near the position where the edge image of the chart member is formed by the optical system. An evaluation system for an optical system, comprising: an arranged light receiving means; and an operation means for performing a predetermined operation based on the output of the light receiving means. 16. A focus evaluation method for an optical system including an optical element having a periodic structure, which comprises forming an image of a chart member having a difference in brightness in a one-dimensional direction on a light receiving means or its vicinity by the optical system. Smoothing the chart member image received by the light receiving means to obtain one-dimensional data in the direction of change in brightness of the chart member image; and performing a predetermined calculation based on the one-dimensional data. A focus evaluation method for an optical system, characterized by: 17. The focus evaluation method for an optical system according to claim 16, further comprising the step of averaging the one-dimensional data in a direction orthogonal to the light-dark change direction. 18. The focus evaluation method for an optical system according to claim 17, further comprising the step of optically smoothing the chart member image with a low-pass filter arranged in the optical path of the optical system. . 19. A focus evaluation method for an optical system, wherein the chart member image according to claim 16 is an edge image. 20. The focus evaluation method for an optical system according to claim 19, wherein the calculation step directly calculates an evaluation value from the edge image. 21. The calculation step according to claim 19, wherein the calculation step includes a step of differentiating the one-dimensional data of the edge image to calculate an LSF and a step of calculating an evaluation value from the LSF. Optical system focus evaluation method. 22. A focus evaluation method for an optical system, wherein the chart member image according to claim 16 is a linear image. 23. The focus evaluation method for an optical system according to claim 22, further comprising the step of calculating an LSF based on the line image data output from the light receiving means. 24. The calculation step according to claim 21 or 23,
A focus evaluation method for an optical system, which comprises a step of calculating MTF by Fourier transforming LSF as the evaluation value. 25. The calculation step according to claim 21 or 23,
And a step of calculating a standard deviation of LSF as the evaluation value. 26. The calculation step according to claim 21 or 23,
And a step of calculating the width of the LSF. 27. The focus evaluation method for an optical system according to claim 26, wherein the width of the LSF is used as an evaluation value. 28. The focus evaluation method for an optical system according to claim 26, further comprising the step of Fourier-transforming the LSF within the width to calculate an MTF as the evaluation value. 29. The evaluation value according to claim 26,
And a step of calculating a standard deviation of the LSF within the width, which is a focus evaluation method for an optical system. 30. A chart device for forming an image of a chart member on an observing surface of a predetermined distance by an optical system to be inspected, wherein a plurality of chart members are arranged at different object distances, and further, an image of each chart member. Is arranged so as to be simultaneously formed at different positions on the observation surface at a predetermined distance by the test optical system. 31. At least two chart members are arranged at an object distance at which it is expected that their images will have an equal defocus amount at the position of the predetermined observation plane of the optical system to be inspected. A chart device characterized by the above. 32. The at least one chart member according to claim 31, wherein the at least one chart member is arranged at an object distance at which the predetermined observation surface position of the optical system to be inspected is expected to be the best imaging position. Chart device characterized by. 33. The chart device according to claim 30, wherein the chart member comprises a chart plate that forms a one-dimensional chart image in which a shade portion changes in a one-dimensional direction. 34. The chart device according to claim 33, wherein the one-dimensional chart image is formed by an edge chart formed on the chart plate at a boundary between bright and dark portions. 35. The chart device according to claim 33, wherein the one-dimensional chart image is formed by a line chart formed on the chart plate. 36. The chart device according to claim 34 or 35, wherein the one-dimensional chart is formed in a radial direction. 37. The chart device according to claim 34, wherein the one-dimensional chart plates are arranged at different distances with respect to the optical axis. 38. A chart device according to claim 30, wherein the chart member is rotatably formed. 39. The chart plate according to claim 38, wherein each of the chart plates is a sector chart plate fixed to a rotatable shaft, and a central angle of each sector is approximately when the number of chart plates is n. The chart device is characterized in that it is 360 ° / n. 40. A chart device according to claim 39, wherein the radius of the sector chart plate is proportional to the distance from the optical system to be tested. 41. The chart device according to claim 38, wherein the center of rotation coincides with the optical axis of the optical system under test. 42. The chart device according to claim 38, wherein the center of rotation is separated from the optical axis of the optical system under test. 43. The chart device according to claim 30, wherein the respective chart members are simultaneously imaged within approximately 30% of an image plane of the optical system under test. . 44. A focus evaluation method for an optical system, comprising: arranging one or a plurality of chart members at different object distances of the optical system; and receiving light arranged at or near an image forming position of the optical system. Each chart member imaged on the light receiving means with respect to a step of forming an image of each chart member on the means, and a preset target value for forming an image on the light receiving means of the chart member having the different object distance. And a step of calculating an evaluation value of the image. 45. The focus evaluation method for an optical system according to claim 44, wherein the evaluation value of the chart member on the long distance side is more important than the evaluation value of the chart member on the short distance side. 46. The focus evaluation method for an optical system according to claim 44, wherein the evaluation value of the chart member on the short distance side is more important than the evaluation value of the chart member on the long distance side. 47. In any one of claims 44 to 46, an intermediate chart member is placed between the chart member on the far distance side and the chart member on the short distance side, and the target value of the intermediate chart member is: A focus evaluation method for an optical system, which is smaller than a target value of the chart member on the long distance side and a target value of the chart member on the short distance side. 48. The target value and the evaluation value according to claim 44, wherein the target value and the evaluation value are values relating to a blur amount of an image of each chart member formed on the light receiving unit. And the focus evaluation method of the optical system. 49. The chart member according to claim 48, wherein a plurality of chart members are provided, and different target values are set for the blur amount of the chart image at a plurality of object distances for each chart member. Optical system focus evaluation method. 50. A focus adjusting method for an optical system, comprising the steps of: arranging one or more chart members at different object distances of an optical system to be inspected; and arranging the chart members at or near an imaging position of the optical system. Forming an image of each chart member on the received light receiving means, and an image of each chart member imaged on the light receiving means with respect to a preset target value for the image on the light receiving means of each chart member. A focus evaluation step of calculating an evaluation value of, and a focus adjustment step of adjusting a focus position of the optical system to be tested based on the target evaluation value and the calculated evaluation value, and an optical system characterized by: Focus adjustment method. 51. The focus adjusting method for an optical system according to claim 50, wherein the evaluation value of the chart member on the long distance side is more important than the evaluation value of the chart member on the short distance side. 52. The focus adjusting method for an optical system according to claim 50, wherein the evaluation value of the chart member on the near distance side is more important than the evaluation value of the chart member on the far distance side. 53. The intermediate chart member according to any one of claims 50 to 52, wherein an intermediate chart member is placed between the long distance side chart member and the short distance side chart member, and a target value of the intermediate chart member is: A focus adjustment method for an optical system, which is smaller than a target value of the long-distance side chart member and a target value of the short-distance side chart member. 54. The target value and the evaluation value according to any one of claims 50 to 53, wherein the target value and the evaluation value are values relating to a blur amount of an image of each chart member formed on the light receiving means. How to adjust the focus of the optical system. 55. The chart member according to claim 54, wherein a plurality of chart members are provided, and different target values are set for the blur amount of the chart image at a plurality of object distances for each chart member. Optical system focus evaluation method. 56. A focus adjusting device for an optical system, comprising: a chart member arranged at a plurality of object distances of the optical system to be inspected; and a light receiving means arranged at or near an image forming position of the optical system. A blur amount calculation unit that calculates the blur amount of the image of each chart member formed on the light receiving unit, and the calculated blur amount of the image of each chart member so that the calculated blur amount matches a preset target value. A focus adjusting device for adjusting the focus position of the optical inspection system, and a focus adjusting device for the optical system. 57. A method for evaluating the focus of an imaging optical system, comprising N pieces located within a predetermined distance range sandwiching an object distance for which the best focus is expected with respect to the imaging optical system to be tested. However, N is an integer of 2 or more), the step of converting the image formed by the above-mentioned image forming optical system to be examined into electrical data by the chart means; focusing on each chart means based on each of the converted data. A step of calculating an evaluation value y _n (n = 1 to N); and a function based on the N evaluation values y _n , S = g (y ₁ , y ₂ , ..., Y _n , ..., Y _N ), The step of calculating the measured total evaluation value S by
A focus evaluation method characterized by. 58. The focus evaluation, wherein the evaluation method according to claim 57 further includes a step of comparing the actual measurement comprehensive evaluation value S with a preset reference comprehensive evaluation value S _0. Method. 59. A near chart means located closer than the object distance for which the best focus is expected for the test imaging optical system, a far chart means located at the same distance,
And a step of converting the image formed by the image-forming optical system to be inspected of the intermediate chart means located between the two chart means into electrical data; each chart means based on each of the transformed data. A step of calculating focus evaluation values y ₁ , y ₂ , y ₃ for, and a function based on the above three evaluation values y ₁ , y ₂ , y ₃ , S = g (y ₁ , y ₂ , y ₃ ), The step of calculating the measured total evaluation value S by
A focus evaluation method characterized by. 60. The focus evaluation according to claim 59, further comprising a step of comparing the actually measured total evaluation value S with a preset reference total evaluation value S _0. Method. 61. The focus evaluation method according to claim 59 or 60, wherein the function g is represented by (y ₁ -y ₂ ) / (y ₂ -y ₃ ). 62. The focus evaluation method according to claim 59 or 60, wherein the function g is represented by (y ₂ −y ₃ ) / (y ₁ −y ₃ ). 63. The focus evaluation method according to claim 59 or 60, wherein the function g is represented by y ₃ / y ₂ −y ₂ / y ₁ . 64. The focus adjusting method according to claim 58, further comprising a step of changing a focus state based on the comparison result. 65. N (where N is an integer of 2 or more) chart means positioned within a predetermined distance range sandwiching an object distance for which the best focus is expected with respect to a test imaging optical system, Converting the image formed by the image forming optical system to be examined into electrical data; focus evaluation value y _n for each chart means based on each of the converted data
Calculating (n = 1 to N); changing the focus state according to the focus adjustment amount x; expressing the focus evaluation value y _n by a function of the focus adjustment amount x, y _n = f _n (x); The N focus evaluation values y _n (n = 1 to 1)
N) a function, S = g (y ₁ , y ₂ , ..., Y _n , ..., Y _N ) to calculate the measured total evaluation value S; and the functions f _n , g and the focus evaluation. A step of calculating a focus adjustment target value x ₀ satisfying a preset reference comprehensive evaluation value S ₀ based on the value y _n and the actually measured overall evaluation value S; and adjusting the focus. Method. 66. The function f _{n according to} claim 65,
The (x) using a function f _'n which is obtained by linear approximation (x), by calculating the focus adjustment target value x ₀ which satisfies the above criteria overall evaluation value S _0, the Adjustment of focus, wherein . 67. A near chart means located closer to an object distance for which the best focus is expected for the test imaging optical system, a far chart means located at the same distance,
And a step of converting an image formed by the image-forming optical system to be tested into electrical data of an intermediate chart means located between the two chart means; each chart based on each of the converted data. Calculating the focus evaluation values y ₁ , y ₂ , y ₃ for the means; changing the focus state by the focus adjustment amount x; the focus evaluation value y
_A step of expressing ₁ , y ₂ and y ₃ by a function of the focus adjustment amount x, y ₁ = f ₁ (x) y ₂ = f ₂ (x) y ₃ = f ₃ (x); the above three focus evaluation values y ₁ , y ₂ , y
A step of calculating a measured total evaluation value S by a function S = g (y ₁ , y ₂ , y ₃ ) based on ₃ ; and the functions f ₁ , f ₂ , f ₃ , g and the focus evaluation value y
A step of calculating a focus adjustment target value x ₀ satisfying a preset reference comprehensive evaluation value S ₀ on the basis of ₁ , y ₂ , y ₃ and the actual measured comprehensive evaluation value S. How to adjust the focus. 68. The adjusting method according to claim 67, further comprising a function f ′ (x) ₁ , obtained by linearly approximating the functions f ₁ (x), f ₂ (x) and f ₃ (x), f '(x) ₂ ,
using f ′ (x) ₃ to calculate a focus adjustment target value x ₀ satisfying the above-mentioned reference overall evaluation value S ₀ ,
Focus adjustment method characterized by. 69. The focus adjusting method according to claim 67 or 68, wherein the function g is represented by (y ₁ -y ₂ ) / (y ₂ -y ₃ ). 70. The focus adjusting method according to claim 67 or 68, wherein the function g is represented by (y ₂ −y ₃ ) / (y ₁ −y ₃ ). 71. The focus adjusting method according to claim 67 or 68, wherein the function g is represented by y ₃ / y ₂ −y ₂ / y ₁ . 72. N chart means (where N is an integer of 2 or more) positioned within a predetermined distance range sandwiching an object distance for which the best focus is expected for the test imaging optical system; Means for converting the image of each chart means formed by the test imaging optical system into electrical data; and focus evaluation value y _n (n = 1) for each chart means based on each converted data. To N), and a function based on the N evaluation values y _n , S = g (y ₁ , y ₂ , ..., Y _n , ..., y _N ) Means for evaluating focus.