JPH06342122A - Endoscope provided with focusing function - Google Patents

Abstract

PURPOSE:To efficiently observe the range of depth of field by appropriately interlocking focusing function with diaphragm function. CONSTITUTION:A movable aperture diaphragm 2 having a variable diameter is disposed inside an objective lens 1, and an image pickup unit 6 provided with a CCD 3, a crystal filter 5, and a color temperature correcting filter 4 are disposed behind the lens 1. A piezoelectric element 8 movable in parallel to an optical axis 7 in a direction shown by an arrow is provided on the unit 6, and focusing is performed by a driving device. Since the variation of the piezoelectric element 8 is decided according to an applied voltage, the position change of the image pickup unit 6 by means of the focusing is found by converting the change of an impressed voltage. The diaphragm diameter of the variable aperture diaphragm 2 is adjusted by a driving circuit so that the brightness of the range of depth of field on a farthest point may be constant at the time based on the variation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endoscope having a focusing function.

[0002]

2. Description of the Related Art In conventional endoscopes, in order to avoid complexity during surgery, the one that is used without changing the focus, aperture, focal length, etc. of an optical system is mainly used. Therefore, the aperture stop is previously narrowed down so that the minimum required far point object (several tens of mm) and the near point object point can be observed, and a considerably wide range of depth of field is secured, which is in practical use. However, the brightness and the depth of field have a contradictory relationship, and the brightness decreases when trying to obtain a wider depth, and the depth becomes insufficient when the brightness increases.

Further, in recent years, in electronic endoscopes using a solid-state image pickup device (hereinafter referred to as CCD), further improvement in image quality is desired, and the number of pixels is increasing. However, in the case of an endoscope, there is a limitation on the size of the CCD provided at the distal end portion, and in order to increase the number of pixels, the unit area per pixel must be reduced. Then, if the pixel is made smaller, C
The CD has a double defect that the sensitivity of the CD is lowered and the CD becomes darker, and the optical depth is shallower as the diameter of the circle of confusion is smaller. That is, an optical system having a focus function is indispensable in order to obtain an endoscope capable of ensuring high image quality and brightness that does not pose a practical problem. Then, JP-A-62-229112
In Japanese Patent Application Laid-Open No. 2-18513, a method of moving a focus lens back and forth with respect to an optical axis is disclosed.
A method of focusing by moving the unit back and forth is disclosed.

On the other hand, it is conceivable that an endoscope, such as a video camera or a still camera, may be provided with an autofocus function capable of automatically focusing according to the distance of a subject. As a focus detection means for obtaining the distance to a typical subject at this time, a method of emitting infrared rays or ultrasonic waves toward the subject from the camera side and measuring the distance using the reflected light (wave) (active type) And a method of measuring by capturing only natural light emitted from a subject (passive type). However, the former method is not practical as an endoscope because it requires an infrared ray generating device and a light receiving element at the tip. On the other hand, even in the latter method, since it is a triangulation method in which another sensor for autofocusing such as a line sensor is incorporated in addition to the CCD for picking up an image of a subject, it cannot be said to be practical as in the former method.

Therefore, in the case of an endoscope or the like, a video signal utilizing system (so-called hill climbing servo system) that directly obtains focus information from a video signal and executes autofocus is adopted, so that the tip portion is the most compact. It is optimal because it can be put together. In this method, as shown in FIG. 9, the voltage level of the high frequency component of the video signal corresponds to the definition of the reproduced image, that is, the high frequency output of the video signal becomes maximum at the in-focus point. Focusing attention, focusing is performed by adjusting the lens position and the like so that the high frequency output of the video signal becomes the maximum level. Note that FIG. 9 shows the relationship between the defocus amount (focus shift amount) and the video signal high-frequency output for different subjects. Further, as shown in the figure, the curve of the high frequency output generally changes depending on the subject.

[0006]

By the way, in normal autofocus, focus detection is performed at the center of the screen. This is because, when shooting with a video camera or the like, the subject is usually set so as to be positioned in the center of the screen. Therefore, if focus detection is performed in the center of the screen, the necessary part will be in focus. This is because a matching image can be obtained. However, in the case of an endoscope, the target subject is not limited to a flat surface, and particularly, the large intestine, the bronchus, and the like have a luminal shape. Therefore, if distance measurement is performed in the center of the screen, if the part you actually want to observe is out of the center of the screen, you will be focused far away, which will prevent accurate observation. Will occur.

In the case of a conventional endoscope with focus,
As described above, since the focus adjustment is simply performed by moving the focus lens or the CCD unit, the diameter of the aperture stop does not change and F _no. Is constant. Therefore, if you focus on the near point side, the depth of field will become shallow,
The observation range becomes narrow. In addition, the body cavity is constantly moving,
If the depth of field is narrow, the image will be blurred instantly, which is very difficult to use for diagnosis and treatment.

Therefore, in Japanese Patent Laid-Open No. 63-78119, a lens near the aperture stop in the objective optical system is provided with a surface having different curvatures so that the focal length changes in a plurality of states in the lens surface. Further, there is shown an optical system in which the best distance (the object distance in focus accurately) is shifted to the near point side by providing a variable aperture stop when the aperture stop is stopped down. When this optical system is used, F _no. Becomes large and the depth of field becomes deep during near-point observation, so that the inconvenience in close-up observation is reduced as compared with the conventional focus endoscope. However, in order to prevent the spherical aberration from deteriorating during the far point observation with the diaphragm open, it is necessary to previously match the far point side object distances of the depth of field during both the far point observation and the near point observation. is there. Therefore, the two focal lengths cannot be unnecessarily separated from each other, and it is difficult to widen the width of the focusable object distance. Further, since the depth of field at the time of near point observation must be made very deep, the amount of narrowing down of the aperture stop becomes large. As a result, there is a problem that even if the subject is in focus, the distance is too dark to observe.

In view of the above problems of the prior art, the present invention provides an endoscope in which the range of depth of field can be observed without waste by appropriately interlocking the focus function and the diaphragm operation. The purpose is to do.

[0010]

In order to achieve the above object, the endoscope according to the present invention has a focus function capable of adjusting a focus position according to a change of an object distance to a subject and a brightness of an optical system. With adjustable brightness diaphragm,
In an endoscope capable of adjusting the focus of an object at a focus position at an arbitrary object distance, focus position detection means for detecting a variation amount of a focus lens or an image pickup unit due to variation of a distance to a subject, and the detection thereof. Based on the value detected by the means, a driving device is provided for adjusting the aperture stop so that the brightness of the farthest point of the depth of field at that time is always constant, and the F-number is set at the same time as the focusing. It is characterized in that the expression 0.9A ≦ F _no. '≦ 1.2A is satisfied. However, A = F _no 'is _{{(· x B0 / f l} 2, also, f _l: focal length of the endoscope optical system as a whole system ^{_{Δx B × f l 2 -Δx B}} )}':. Object distance Gaussian image plane shift amount due to change of x x _B0 : Distance from front focus position f _F to best object point before focus (X _B0 <0) F _{no .} : F number before focus F _no. ': After focus It is the F number of.

Further, in the apparatus according to the present invention, in an endoscope having a focusing function using a solid-state image pickup device as an image pickup means, a specific frequency of a video signal obtained from the solid-state image pickup device is extracted, and the extracted frequency component of the extracted frequency component is extracted. It is characterized by providing an autofocus function for integrating the voltage level over the entire imaging surface and performing focusing so that the integrated value becomes maximum.

The operation will be described below. First, the relational expression between the depth of field and F _no. Is shown below. _{(1 / x F0) - (} 1 / x B0) = φ (F no / f l 2.) ··· (1) (1 / x B0) - (1 / x N0) = φ (F no /. f _l ² ) (2) where x _B0 : distance from the front focus position to the best object point (x _B <0) x _F0 : distance from the front focus position to the farthest point of the depth of field ( x _F <0) x _N0 : Distance from the front focus position to the closest point of the depth of field (x _N <0) f _l : Focal length φ: Allowable circle of confusion. A conceptual diagram of the above formulas (1) and (2) is shown in FIG. 8 (the direction of the reference sign is positive to the right). In the figure, (a) shows the state of the optical system at the best object point, (b) shows the near point, and (c) shows the state of the far point, respectively, 61 is the front focal position, 62 is the objective lens, and 63 is the objective lens.
Is the rear focal position, and 64 is the evaluation surface. Here, when the distance x _F0 from the front focus position to the farthest point (far point object point) of the depth of field due to focusing changes to x _F , the following relational expression holds. x _F = kx _F0 (k: coefficient) (3) Since the front focus position is considered to be almost 0 in the case of an endoscope, the amount of change in the distance from the objective lens to the far point object point (ratio)
Can be written as k. That is, it is possible to identify the distance from the front focus to the object point and the object distance. Therefore, assuming that the object is identical, to obtain the same brightness as the far point object point distance x _F0 before change in far point object point distance x _F after the focus change object distance and F _no. And the Since there is an inverse proportional relationship between them, F _no. '= (X _F0 / x _F ) F _no. = (1 / k) F _no. (F _no. ': F number after focus change) ・ ・ ・ ( The relationship of 4) should be established.

At this time, the distance x _B from the front focus position after focus change to the best object point and the distance x _N to the closest point (near object point) of the depth of field are expressed by the above equations (1) to (1). 4) from the _{(1 / x F) -.} . (1 / x B) = φ (F no '/ f l 2) = φ (F no / k / f 1 2) = (1 / k) (1 / x _F0 −1 / x _B0 ) = (1 / x _F ) − (1 / x _B0 ) ∴1 / x _B = 1 / kx _B0 ∴x _B = kx _B0 (5) Similarly, x _N = kx The relationship of _N0 ... (6) is derived. Summarizing the above, when F _no. '= (1 / k) F _no. , The relationship of x _N = kx _N0 , x _B = kx _B0 , x _F = kx _F0 (7) holds, and focusing is performed. An optical system in which the brightness on the far side of the depth of field matches before and after is obtained.

Here, the relational expression of the shift amount of the Gaussian image plane due to the change of the best distance is obtained. Distance x _B 'to the _{x B · x B' = -f} l 2 next to the rear side focal point position to the Gaussian image plane with respect to the distance x _B from the front focal position to the best object point, also Gaussian after focus change Letting the shift amount of the image plane be Δx _B ′, Δx _B ′ = −f _l ² {(1 / x _B ) − (1 / x _B0 )} = − (f _l ² / x _B0 ) {(1 / k) −1} (8) From ^{_{this, k = f l 2 / (}} f l 2 -Δx B '· x B0) relational expression (9) is obtained.

[0015] Equation (9), in order to make constant the brightness of the far point of even moves the image surface depth of field by _{focusing, F no. '= F no} . (F l 2 -Δx It is desirable to set the relationship between the focus adjustment of the endoscope objective system and the F-number change so that _B ′ · x _B0 ) / _fl ² (10). However, actually F _no. 'And F _no. Relationship with strictly rather than having to satisfy Equation _{(10), F no. (} F l 2 -Δx B' · x B0) / f _{When l} ² = A, there is no practical problem if F _no. 'is in the range of 0.9 A ≤ F _no. ' ≤ 1.2 A. Outside this range, the depth becomes shallow and the observation range becomes narrow, or it becomes too dark, and problems such as inability to see far points occur.

FIG. 7 shows an outline of a circuit for performing processing from focusing to driving the aperture stop. In the figure,
Reference numeral 1 is an objective lens, 2 is an aperture stop, 3 is a CCD, 71 is a focus drive and focus position detection means, 72 is a calculation / control means, 73 is an aperture stop drive means, and 74 is a video signal processing means. The object not shown is the objective lens 1.
An image is formed on the CCD 3 by. The output signal of the CCD 3 is displayed on a monitor means (not shown) through a predetermined process by the video signal processing means 74. A part of the video signal is supplied to the arithmetic / control means 72. The focus detection is performed by the calculation / control means 72 based on this video signal, and the result is supplied to the focus drive / focus position detection means 71, and the focusing is performed by moving the CCD 3 back and forth. The movement of the CCD 3 is detected by the focus drive / focus position detection means 71, and a signal indicating the focus position is supplied to the calculation / control means 72. The calculation / control means 72 calculates an F number for keeping the brightness of the far point constant based on this signal.
In response to this signal, the aperture stop driving means 73 changes the aperture of the aperture stop 2 to a predetermined size. Although the focusing is automatically performed here, the autofocus function is not always necessary, and the focus may be manually adjusted. Needless to say, instead of the CCD 3, the whole objective lens or a part of the objective lens may be moved for focusing.

[0017]

EXAMPLES Examples of the present invention will be described below. First, the autofocus system will be described with reference to FIGS. In an endoscope, if a wide area of the entire drawing cannot be clearly seen, it may take time to make a diagnosis, and a problem such as damage to an erroneous place during treatment is likely to occur. For this reason, the distance measuring range is set to the entire image pickup surface so that the observation target can correspond to any position on the screen, and the voltage level of the high frequency component of the video signal obtained therefrom is integrated over the entire image pickup surface. , The lens (or CC
Focusing is preferably performed by adjusting the position of D). FIG. 1 shows an outline of a circuit that performs such control. In the figure, 81 is a preamplifier, 82 is a color separation unit that separates a video signal obtained from the CCD 3 into a color difference signal and a luminance signal Y, 83 is a color difference process unit, 84 is a luminance signal Y process unit, and 85 is an NTSC encoder. Reference numeral 86 is a differentiating circuit that detects the edge of the luminance signal waveform for each horizontal scanning line, 87 is an integrating circuit that integrates the voltage level of the high frequency component of the video signal obtained by the differentiating circuit 86 over the entire imaging surface, and 88 is A control unit that controls the entire system. Further, 89 is a driving means for driving the CCD 3.

In the above, an object (not shown) is imaged on the CCD 3 by the objective lens 1. The output signal of the CCD 3 is amplified by the preamplifier 81 and then separated into a luminance signal Y and a color signal C by the color separation section 82. Then, the color signal C is subjected to signal processing by the color difference processing unit 83 and then supplied to the NTSC encoder 85. On the other hand, the luminance signal Y is subjected to signal processing by the process unit 84, then supplied to the NTSC encoder 85, and combined with the color difference signal Y, the synchronizing signal, etc.
It becomes a video signal and is supplied to a monitor TV (not shown). A part of the luminance signal Y is processed by the process unit 84 and then supplied to the differentiating circuit 86, where the edge detection, that is, the high frequency component in the luminance signal is detected. Integrating circuit 87
Integrates the output signal of the differentiating circuit 86 over the entire screen so that the in-focus portion of the screen becomes the widest. That is, since the outline of the object appears clearly in a sharply focused area, the larger the edge signal, the more the area in focus. Further, the integrated output is supplied to the control unit 88.

Next, in response to the control signal from the control unit 88, the driving means 89 moves the CCD 3 over its entire movable range. When the above operation is performed along with the movement, the control unit 88 can detect the relationship between the magnitude of the integrated output signal and the lens position. Therefore, if the CCD 3 is moved again to the position where the integrated output reaches the peak after the movement of the entire movable range is completed, the autofocus adjustment can be performed to a position where the wide screen is in focus.

However, there is a drawback in the method of performing focusing by performing distance measurement on the entire image pickup surface. That is, the integrated value of the voltage level of the high frequency component becomes the same value when the near point side is focused and when the far point side is focused. That is, in the endoscope objective optical system, since the depth of field is basically wide, when a subject exists within the depth, the integrated value within that range becomes the same value. In this case, it is not possible to determine where to set the focus position, and the focus lens continues to move back and forth within the settable range.
Further, between the focus and the aperture stop, the above formula (1
Since the relationship of 0) is established, opening and closing of the diaphragm continues to move similarly to the focus lens, and the brightness of the screen continues to change, making it difficult to observe.

Therefore, in the case of the above-mentioned state, it is advisable to set the autofocus drive device so as to focus on the far point side. This is particularly effective for an endoscope using a CCD, because it has a low sensitivity of the CCD, and thus an absolute lack of brightness is eliminated. That is, F _no. Is reduced by performing focusing so that the focus is on the far point side, and therefore a bright observation image can be obtained. However, it is not always sufficient to focus on the far point side. For example, when trying to observe the surface of a protrusion called a polyp that exists in the large intestine or the like, it may be difficult to focus with autofocus, which shifts the focus to the far point side, because the area of the part you want to see is small. There is a risk.

Therefore, normally, focusing is set to the far point side, a manual fine adjustment knob is provided, and a mechanism capable of manually adjusting the focus drive device is provided to adjust the focusing range to the near point side. You will be able to shift arbitrarily. For endoscopes, a system capable of arbitrarily fine-tuning is required rather than full automation such as conventional autofocus.

FIG. 2 is an endoscope according to the first embodiment of the present invention.
The objective optical system portion at the tip, (a) is an initial stage described later
State (F_no.2.7) and (b) are F_no.10.8 condition
The respective optical systems are shown. At this time, in the objective lens 1
A variable aperture diaphragm with a variable aperture diameter and an objective lens 1
After CCD 3, crystal filter 5, color temperature correction fill
And an image pickup unit 6 having a camera 4. or,
The objective lens 1 is composed of five lens components,
One lens (front group) is attached to the lens holding member 10, and
The three (rear group) lenses are mounted on the lens holding member 11 respectively.
It is attached. And these lens holding members are
It is fixed to the endoscope body not shown. In addition, the imaging unit
The lens 6 is moved parallel to the optical axis 7 in the direction of the arrow in the figure.
A movable piezoelectric element 8 is provided, and driving (not shown)
Is configured to be focused by the device
There is. The voltage supplied to the piezoelectric element 8 is controlled by the control shown in FIG.
Determined by section 88. As the drive device,
There are various things such as those by ear, those by motor, but especially
In consideration of drive response and compactness,
Is the stacking pressure formed by stacking multiple piezoelectric elements in the optical axis direction.
An electric element is used. Therefore, the driving voltage of the piezoelectric element 8 is
When applied, it expands and contracts in the direction of the optical axis, and the position of the imaging unit 6
Focusing is performed by changing. Change of piezoelectric element 8
Since the amount of charge is determined by the applied voltage, focusing
Change in position of the image pickup unit 6 due to Δx_B’(Equation (8)
Therefore, is to convert the change in applied voltage
Therefore, it can be obtained. Further, from the above formula (1
Δx to 0)_BSubstitute the value of ' _no.The amount of change in
Aperture diameter of the variable aperture stop 2 by a drive circuit (not shown)
Is adjusted.

As the aperture stop 2, an iris stop well known in cameras and the like can be used. Further, an electro-optical diaphragm using a liquid crystal, an electrochromic element or the like can be used, which is convenient because there is no mechanical moving part. Also, the calculation for obtaining F _{no. And the} aperture stop 2
The control of each is controlled by the control unit 88.

Here, at F _no. 2.7, the far point depth is 1000
Table 1 below shows the relationship between Δx _B 'and F _no. and depth of field when mm is the initial state. Permissible circle of confusion diameter phi = 10 [mu] m focal length f _l = 1.0 front focal point f _F = 0.438 x _B0 = - (Best Distance initial state) - (the front focal point) = -35.277-0.438 = -35.718 _(mm)

In Table 1, it can be seen that the brightness at the far point is always constant because the relationship of the equation (4) is established between the change in the far point depth and the change in F _no. . Further, in this apparatus, a focus detection circuit for integrating the voltage level of the high frequency component of the video signal obtained from the CCD 3 as described above over the entire image pickup surface and finding the position of the image pickup unit 6 where the value that can be taken is the maximum is provided. By including a circuit for sending the driving voltage to the piezoelectric element 8, autofocusing becomes possible.

The lens data in the initial state in this embodiment will be shown below. _{r 1 = 9999.0000 d 1 = 0.2538} n 1 = 1.69680 ν 1 = 55.52 r 2 = 0.6493 d 2 = 0.2115 n 2 = 1.00000 ν 2 = 0.00 r 3 = 1.2525 d 3 = 0.2221 n 3 = 1.80518 ν 3 = 25.43 r 4 = -2.7483 d ₄ = 0.1058 n ₄ = 1.53172 ν ₄ = 48.90 r ₅ = 0.8388 d ₅ = 0.2602 n ₅ = 1.00000 ν ₅ = 0.00 r ₆ = 9999.0000 d ₆ = 0.0212 n ₅ = 1.0000 ν ₆ = 0.00 r ₇ = 3.0571 d ₇ = 0.8101 n ₇ = 1.72916 ν ₇ = 54.68 r ₈ ＝ -1.1269 d ₈ ＝ 0.0254 n ₈ ＝ 1.00000 ν ₈ ＝ 0.00 r ₉ ＝ -5.3369 d ₉ ＝ 0.1058 n ₉ ＝ 1.84666 ν ₉ ＝ 23.78 r ₁₀ ＝ 1.2443 d ₁₀ = 0.5753 n ₁₀ = 1.51633 ν ₁₀ = 64.15

R ₁₁ = -1.5550 d ₁₁ = 0.4547 n ₁₁ = 1.00000 ν ₁₁ = 0.00 r ₁₂ = 1.7422 d ₁₂ = 0.6345 n ₁₂ = 1.58913 ν ₁₂ = 60.97 r ₁₃ = 9999.0000 d ₁₃ = 0.6607 n ₁₃ = 1.0000 ν ₁₃ ＝ 0.00 r ₁₄ ＝ 9999.0000 d ₁₄ ＝ 0.3137 n ₁₄ ＝ 1.52000 ν ₁₄ ＝ 74.00 r ₁₅ ＝ 9999.0000 d ₁₅ ＝ 0.5436 n ₁₅ ＝ 1.54869 ν ₁₅ ＝ 45.55 r ₁₆ ＝ 9999.0000 d ₁₆ ＝ 0.1058 n ₁₆ ＝ 1.51633 ν ₁₆ ＝ 64.15 r ₁₇ = 9999.0000 d ₁₇ = 0.0000 n ₁₇ = 1.00000 ν ₁₇ = 0.00

Next, a second embodiment according to the present invention will be described with reference to FIGS. In this embodiment, an area in which the voltage level of the high frequency component of the video signal is a certain value or more is taken out,
Focusing is performed so that the area of the region becomes the largest. In FIG. 3, a video signal obtained from the CCD 3 is separated into a color difference signal and a luminance signal Y by a color separation section 82, and further, a differentiation circuit 86 separates an edge of a luminance signal waveform (A in FIG. 3) for each horizontal scanning line. Detection (ΔY = dY /
dt) is performed. The signal waveform (B in FIG. 3) obtained here is output to a low output level (vi in FIG. 3) by the limiter circuit 91.
A signal waveform (C in FIG. 3) obtained by cutting (corresponding to the waveform of 1) is output, and this is detected by the counter 92. For this line, And this is done for one field. That is, And the lens 1 (or CCD 3) is driven so that this value becomes maximum.

FIG. 4 shows an optical system in which an external television camera 23 is provided after the rigid mirror optical system 21 (the intermediate relay system is not shown) in the second embodiment of the present invention.
Further, FIG. 5 shows only an external television camera 23 disposed after the rigid endoscope eyepiece 22, and (a) in the drawing shows an initial state (F
_Nos. 6.3) and (b) show the optical systems focused on the near point side in F _no. 12.5, respectively. The external television camera 23 is composed of an imaging optical system 9 including a variable diaphragm 2, and an image pickup unit 6 having a CCD 3, a crystal filter 5, and a color temperature correction filter 4. Originally, there is no aperture stop on the rigid endoscope side, and the brightness is determined by the diameter of the relay optical system. Therefore, the variable aperture stop 2 that can be used as a substitute for the aperture stop on the external camera side is provided with the imaging optical system 9. It is arranged near the pupil position. By disposing the diaphragm at this position, the amount of light in the periphery does not change even when the diaphragm is opened and closed, and it becomes possible to uniformly contract from the center to the periphery.
The driving device of the image pickup unit 6 and other methods are the same as those shown in the first embodiment.

At F _no. 6.3, the far point depth is 200 m.
The following Table 2 shows the relationship between Δx _B ', F _no. and depth of field when m is the initial state. Permissible circle of confusion diameter phi = 10 [mu] m focal length f _l = 1.0 front focal point _{f F = 0.47 x B0 = -14.71} (mm)

The lens data in the initial state in this embodiment will be shown below. (Rigid _{endoscope) r 1 = 9999.0000 d 1 =} 0.1069 n 1 = 1.51633 ν 1 = 64.15 r 2 = 9999.0000 d 2 = 0.0428 n 2 = 1.00000 ν 2 = 0.00 r 3 = 9999.0000 d 3 = 0.2352 n 3 = 1.78472 ν 3 = 25.71 r ₄ = -1.7539 d ₄ = 0.0855 n ₄ = 1.69350 ν ₄ = 53.23 r ₅ = 0.3846 d ₅ = 0.2352 n ₅ = 1.0000 ν ₅ = 0.00 r ₆ = 9999.0000 d ₆ = 1.3962 n ₅ = 1.78800 ν ₆ = _{47.43 r 7 = 9999.0000 d 7 =} 0.0747 n 7 = 1.80610 ν 7 = 40.95 r 8 = 9999.0000 d 8 = 0.5475 n 8 = 1.80610 ν 8 = 40.95 r 9 = -1.0616 d 9 = 0.1411 n 9 = 1.00000 ν 9 = 0.00 r ₁₀ = 5.4691 d ₁₀ = 0.6778 n ₁₀ = 1.65844 ν ₁₀ = 50.86

R ₁₁ = -0.6367 d ₁₁ = 0.1668 n ₁₁ = 1.80518 ν ₁₁ = 25.43 r ₁₂ = -4.4618 d ₁₂ = 1.7682 n ₁₂ = 1.00000 ν ₁₂ = 0.00 r ₁₃ = 2.6427 d ₁₃ = 2.3284 n ₁₃ = 1.62004 ν _{13 = 36.25 r 14 = -2.6427 d} 14 = 0.2437 n 14 = 1.00000 ν 14 = 0.00 r 15 = 9999.0000 d 15 = 9.1298 n 15 = 1.62004 ν 15 = 36.25 r 16 = 9999.0000 d 16 = 0.5516 n 16 = 1.00000 ν 16 _{= 0.00 r 17 = 3.0205 d 17} = 0.2138 n 17 = 1.80610 ν 17 = 40.95 r 18 = 1.3799 d 18 = 0.6414 n 18 = 1.65160 ν 18 = 58.67 r 19 = -5.4050 d 19 = 0.3849 n 19 = 1.00000 ν 19 = 0.00 r ₂₀ = 9999.0000 d ₂₀ = 9.3436 n ₂₀ = 1.62004 ν ₂₀ = 36.25

R ₂₁ = -4.0473 d ₂₁ = 1.7105 n ₂₁ = 1.00000 v ₂₁ = 0.00 r ₂₂ = 4.0473 d ₂₂ = 9.3436 n ₂₂ = 1.62004 v ₂₂ = 36.25 r ₂₃ = 9999.0000 d ₂₃ = 0.5516 n ₂₃ = 1.00000 v ₂₃ ＝ 0.00 r ₂₄ ＝ 3.0205 d ₂₄ ＝ 0.2138 n ₂₄ = 1.80610 ν ₂₄ ＝ 40.95 r ₂₅ ＝ 1.3799 d ₂₅ ＝ 0.6414 n ₂₅ ＝ 1.65160 ν ₂₅ ＝ 58.67 r ₂₆ ＝ -5.4050 d ₂₆ ＝ 0.3849 n ₂₆ ＝ 1.00000 ν ₂₆ ＝ 0.00 r ₂₇ = 9999.0000 d ₂₇ = 9.3436 n ₂₇ = 1.62004 v ₂₇ = 36.25 r ₂₈ = -4.0473 d ₂₈ = 1.7105 n ₂₈ = 1.00000 v ₂₈ = 0.00 r ₂₉ = 4.0473 d ₂₉ = 9.3436 n ₂₉ = 1.62004 v ₂₉ = 36.25 r ₃₀ = 9999.0000 d ₃₀ = 0.5516 n ₃₀ = 1.0000 ν ₃₀ = 0.00

R ₃₁ = 3.0205 d ₃₁ = 0.2138 n ₃₁ = 1.80610 ν ₃₁ = 40.95 r ₃₂ = 1.37799 d ₃₂ = 0.6414 n ₃₂ = 1.65160 ν ₃₂ = 58.67 r ₃₃ = -5.4050 d ₃₃ = 0.3849 n ₃₃ = 1.0000 ν _{33 = 0.00 r 34 = 9999.0000 d 34} = 9.3436 n 34 = 1.62004 ν 34 = 36.25 r 35 = -3.0205 d 35 = 5.2897 n 35 = 1.00000 ν 35 = 0.00 r 36 = 6.9773 d 36 = 0.1860 n 36 = 1.78472 ν 36 = _{25.71 r 37 = 2.3519 d 37 =} 0.3891 n 37 = 1.67003 ν 37 = 47.25 r 38 = -4.5914 d 38 = 0.4276 n 38 = 1.00000 ν 38 = 0.00 r 39 = 9999.0000 d 39 = 0.2138 n 39 = 1.51633 ν 39 = 64.15 r ₄₀ = 9999.0000 d ₄₀ = 1.2380 n ₄₀ = 1.0000 ν ₄₀ = 0.00

(Hereinafter, external TV camera) r ₄₁ = 9999.0000 d ₄₁ = 0.2138 n ₄₁ = 1.51633 ν ₄₁ = 64.15 r ₄₂ = 9999.0000 d ₄₂ = 0.6719 n ₄₂ = 1.0000 ν ₄₂ = 0.00 r ₄₃ = 1.463 d ₄₃ = _{0.4854 n 43 = 1.71300 ν 43 =} 53.84 r 44 = -23.0552 d 44 = 0.3806 n 44 = 1.00000 ν 44 = 0.00 r 45 = -1.7967 d 45 = 0.3143 n 45 = 1.75520 ν 45 = 27.51 r 46 = 1.0802 d 46 = 0.7056 n ₄₆ = 1.00000 ν ₄₆ = 0.00 r ₄₇ = 6.3720 d ₄₇ = 0.4062 n ₄₇ = 1.59270 ν ₄₇ = 35.29 r ₄₈ = -2.1668 d ₄₈ = 1.8068 n ₄₈ = 1.0000 ν ₄₈ = 0.00 r ₄₉ = 9999.0000 d ₄₉ = 0.2138 n ₄₉ = 1.51633 ν ₄₉ = 64.15 r ₅₀ = 9999.0000 d ₅₀ = 0.1710 n ₅₀ = 1.0000 ν ₅₀ = 0.00

R ₅₁ = 9999.0000 d ₅₁ = 1.9179 n ₅₁ = 1.54869 v ₅₁ = 45.55 r ₅₂ = 9999.0000 d ₅₂ = 0.2138 n ₅₂ = 1.52630 ν ₅₂ = 51.17 r ₅₃ = 9999.0000 d ₅₃ = 0.0855 n ₅₃ = 1.51633 ν ₅₃ = 64.15 r ₅₄ = 9999.0000 d ₅₄ = 0.0000 n ₅₄ = 1.0000 ν ₅₄ = 0.00

FIG. 6 is a third embodiment of the present invention and shows an optical system in which the CCD 3 is obliquely arranged using prisms 32 and 33. In the figure, (a) is an initial state (F
_No. 5.0) and (b) show the optical systems in the state where the focus lens unit 31 is focused to the near point side with F _no. 20.0. This is the configuration used when using a large CCD. However, in this case, since it is difficult to move the CCD 3 as the image pickup unit in the optical axis direction, the lens unit 31 capable of changing only the focus position without substantially changing the focal length f _l of the optical system as the focus lens. Focusing is performed by driving it back and forth with respect to the optical axis direction. Unlike the case where the CCD is moved for focusing, when the focusing is performed by the lens unit, the displacement amount Δx _B 'of the Gaussian image plane and the displacement amount Δx _B2 ' of the lens unit 31 due to the change of the best distance are the same. Is reversed. Therefore,
When focusing on the near point side, when moving the CCD unit, it is moved away from the object side (+ direction), but when moving the lens unit, the object side (-direction).
To move to and focus. The driving method of the focus lens unit 31 and other autofocus are the same as those in the first embodiment.

Here, at F _no. 5.0, the far point depth is 200 m.
Δx _B ', Δx _B2 ' when m is the initial state,
The relationship between F _{no. And} depth of field is shown in Table 3 below. Allowable circle of confusion φ = 10 μm Focal length f _l = 1.0 Front focus position f _F = 0.433 x _B0 = -18.186 _(mm)

The lens data in the initial state in this embodiment will be shown below. r ₁ = 9999.0000 d ₁ = 0.1836 n ₁ = 1.88300 ν ₁ ＝ 40.78 r ₂ ＝ 0.7810 d ₂ ＝ 1.1854 n ₂ ＝ 1.00000 ν ₂ ＝ 0.00 r ₃ ＝ 11.7498 d ₃ ＝ 0.3698 n ₃ ＝ 1.78590 ν ₃ ＝ 44.18 r _{4 = 1.2730 d 4 = 0.9179 n 4} = 1.64769 ν 4 = 33.80 r 5 = -1.6084 d 5 = 0.2439 n 5 = 1.00000 ν 5 = 0.00 r 6 = 9999.0000 d 6 = 0.1311 n 5 = 1.51633 ν 6 = 64.15 r 7 = _{9999.0000 d 7 = 0.4373 n 7 =} 1.00000 ν 7 = 0.00 r 8 = 4.0241 d 8 = 0.3672 n 8 = 1.53256 ν 8 = 45.91 r 9 = -0.9415 d 9 = 0.1311 n 9 = 1.84666 ν 9 = 23.78 r 10 = - 1.5783 d ₁₀ = 0.0262 n ₁₀ = 1.00000 ν ₁₀ = 0.00

R ₁₁ = 1.8500 d ₁₁ = 0.4144 n ₁₁ = 1.72916 v ₁₁ = 54.68 r ₁₂ = -1.8500 d ₁₂ = 0.1311 n ₁₂ = 1.72825 v ₁₂ = 28.46 r ₁₃ = 1.2754 d ₁₃ = 0.2656 n ₁₃ = 1.00000 v ₁₃ = 0.00 r ₁₄ = 9999.0000 d ₁₄ = 0.6740 n ₁₄ = 1.54869 ν ₁₄ = 45.55 r ₁₅ = 9999.0000 d ₁₅ = 0.3934 n ₁₅ = 1.51633 ν ₁₅ = 64.15 r ₁₆ = 9999.0000 d ₁₆ = 2.0241 n ₁₆ = 1.69500 ν ₁₆ = 42.16 _{r 17 = 9999.0000 d 17 = 0.0003} n 17 = 1.00000 ν 17 = 0.00 r 18 = 9999.0000 d 18 = 0.2838 n 18 = 1.69500 ν 18 = 42.16 r 19 = 9999.0000 d 19 = 0.0004 n 19 = 1.00000 ν 19 = 0.00 r 20 _{= 9999.0000 d 20 = 0.1311 n 20} = 1.51633 ν 20 = 64.15 r 21 = 9999.0000 d 21 = 0.0000 n 21 = 1.00000 ν 21 = 0.00

However, in the above embodiments, r ₁ , r ₂ , ...
··· is the radius of curvature of each lens surface, d ₁ , d ₂ , ··· is the distance between the lenses, n ₁ , n ₂ ··· is the refractive index of each lens, ν ₁ , ν ₂ , · · ... is the Abbe number of each lens. Further, for any of the devices described in the above embodiments,
It is also possible to roughen the focusing step in order to simplify the autofocus device and the variable aperture, that is, to adopt a switching system of 2 to 4 steps. In that case, the brightness on the far point side is adjusted by dimming on the light source side.

[0043]

Since the present invention is constructed as described above, it is practically important that the focusing range can be observed without waste by linking focusing and F number control. Have advantages.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a first embodiment according to the present invention.

FIG. 2 shows a configuration of an optical system of a first embodiment according to the present invention, (a) is an initial state (F _no. 2.7), and (b) is F.
_no. it is a diagram of a state where the imaging unit 6 is focused to the near point side shown respectively at 10.8.

FIG. 3 is a circuit configuration diagram of a second embodiment according to the present invention.

FIG. 4 is a diagram showing a configuration of an optical system of a second embodiment according to the present invention.

FIG. 5 shows a configuration of an external television camera unit in the optical system of the second embodiment, (a) is an initial state (F _no. 6.3),
(B) is a figure which respectively showed the state focused on the near point side by F _no. 12.5.

FIG. 6 shows a configuration of an optical system of a third embodiment according to the present invention, (a) is an initial state (F _no. 5.0), and (b) is F.
_no. diagrams focus state the focus lens unit 31 to the near point side shown respectively at 20.0.

FIG. 7 is a circuit configuration diagram of an apparatus capable of controlling from focusing to driving an aperture stop in an endoscope optical system.

FIG. 8 is a diagram showing the states of the optical systems at the best object point, at the near point, and at the far point, respectively, based on the equations (1) and (2).

FIG. 9 is a diagram showing a relationship between a defocus amount and a video signal high frequency output for different subjects.

[Explanation of symbols]

1 Objective Lens 2 Brightness Aperture 3 CCD 4 Color Temperature Correction Filter 5 Crystal Filter 6 Imaging Unit 7 Optical Axis 8 Piezoelectric Element 9 Imaging Optical System 10, 11 Lens Holding Member 21 Hard Optical System 22 Hard Mirror Eyepiece 23 External TV Camera 31 Lens unit 32, 33 Prism 61 Front focus position 62 Objective lens 63 Rear focus position 64 Evaluation surface 71 Focus detector 72 Depth calculation circuit 73 Brightness stop 74 Video signal processing means 81 Preamplifier 82 Color separation circuit 83 Color difference process section 84 luminance signal Y process section 85 NTSC encoder 86 differentiation circuit 87 integration circuit 88 peak detection circuit 89 driving means 91 limiter 92 counter x _B0 distance from front focus position to best object point before focus x _N0 front focus position to object field Distance to the closest point in depth x _F0 displacement φ permissible circle of confusion of the lens unit 31 'displacement amount [Delta] x _B2 of the Gaussian image plane' distance [Delta] x _B from the front focal distance to the farthest point of the depth of field

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 13, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

The operation will be described below. First, the relational expression between the depth of field and F _no. Is shown below. _{(1 / x F0) - (} 1 / x B0) = φ (F no / f l 2.) ··· (1) (1 / x B0) - (1 / x N0) = φ (F no /. f _l ² ) (2) where x _B0 : distance from the front focus position to the best object point (x _B0 <0) x _F0 : distance from the front focus position to the farthest point of the depth of field ( x _F0 <0) x _N0 : Distance from the front focus position to the closest point of the depth of field (x _N0 <0) _fl : Focal length φ: Allowable circle of confusion. A conceptual diagram of the above formulas (1) and (2) is shown in FIG. 8 (the direction of the reference sign is positive to the right). In the figure, (a) shows the state of the optical system at the best object point, (b) shows the near point, and (c) shows the state of the far point, respectively, 61 is the front focal position, 62 is the objective lens, and 63 is the objective lens.
Is the rear focal position, and 64 is the evaluation surface. Here, when the distance x _F0 from the front focus position to the farthest point (far point object point) of the depth of field due to focusing changes to x _F , the following relational expression holds. x _F = kx _F0 (k: coefficient) (3) Since the front focus position is considered to be almost 0 in the case of an endoscope, the amount of change in the distance from the objective lens to the far point object point (ratio)
Can be written as k. That is, it is possible to identify the distance from the front focus to the object point and the object distance. Therefore, assuming that the object is identical, to obtain the same brightness as the far point object point distance x _F0 before change in far point object point distance x _F after the focus change object distance and F _no. And the Since there is an inverse proportional relationship between them, F _no. '= (X _F0 / x _F ) F _no. = (1 / k) F _no. (F _no. ': F number after focus change) ・ ・ ・ ( The relationship of 4) should be established.

Claims (3)

[Claims] 1. An endoscope optical system having a focus function capable of adjusting a focus position according to a change in a distance to a subject and a variable diaphragm capable of adjusting a brightness of an optical system, wherein a change in an object distance to the subject Focus position detecting means for detecting the amount of fluctuation of the focus lens or the image pickup unit due to, and the brightness at the farthest point of the depth of field at that time is always constant based on the value detected by the detecting means. An endoscope having a focus function, comprising: a drive unit for adjusting a brightness diaphragm. 2. An endoscope having a focus function and a variable brightness diaphragm, wherein the focus position and the F number are changed so as to satisfy the following conditional expression. mirror. _{. 0.9A ≦ F no '. ≦} 1.2A _{where, A = F no × {(} f l 2 -Δx B' is a ^{_{· x B0) / f 2}}} , also, f _l: an endoscope optical system Focal length of entire system Δx _B ': Gaussian image plane shift amount due to change in distance to object x _B0 : Distance from front focus position to best object point before focus adjustment F _{no .} : F number before focus F _no. ': F number after focus. 3. An endoscope having a focusing function using a solid-state image pickup device as an image pickup means, extracting a specific frequency component of a video signal obtained from the solid-state image pickup device, and imaging the voltage level of the extracted frequency component. The endoscope according to claim 1, further comprising an autofocus function that performs integration over the entire surface and performs focusing so that the integrated value becomes maximum.