A design method for the optical system of a small-distortion rigid endoscope

Abstract

The present application relates to a design method for a small-distortion rigid endoscope optical system, comprising the following steps: Step 1: determine parameters, discrete fields of view, and output relative distortion values; Step 2: calculate the discrete fields of view corresponding to the camera adapter and the relative distortion it should produce; Step 3: calculate the actual image height that the camera adapter should achieve; Step 4: coaxially configure the above-mentioned camera adapter behind the optical tube of the rigid endoscope to form a small-distortion rigid endoscope optical system. The present application generates distortion opposite to that of the optical tube through the camera adapter, and performs distortion correction, which can achieve the effect of a large field of view and small distortion of the rigid endoscope; compared with the design method of performing distortion correction at the end of the optical tube with strict lens size restrictions, the present application is less difficult to process and assemble.

Description

Technical Field

[0001] The present application relates to a design method for a small-distortion rigid endoscope optical system. Background Art

[0002] When a rigid endoscope images a target, the target light passes through the objective lens group, the rod lens relay group, the eyepiece group, and the camera adapter in sequence, and finally forms an image on the image detector. The traditional rigid endoscope optical system combines the objective lens group, the rod lens relay group, and the eyepiece into an integrated optical tube design and manufacturing, and the camera adapter is designed and manufactured separately. The two parts independently correct aberrations and are finally connected through a mechanical bayonet. When doctors perform minimally invasive surgery, most of the objective lens group and the rod lens relay group need to be inserted into the human body. The lens of this part has a small aperture, a large field of view, and large distortion; the eyepiece is close to the bayonet and is generally not inserted into the human body. The lens size can be appropriately increased, the field of view is small, and basically no distortion is introduced; the camera adapter does not need to be inserted into the human body, the lens aperture is not strictly limited, the field of view is relatively small, and the distortion will be better corrected. When the objective lens group with large distortion is combined with the rod lens relay group and the eyepiece group and camera adapter with extremely small distortion, the final image also has large distortion, and the relative distortion is usually more than 20%. Conventional methods for correcting large distortions include optical correction and image correction. Image correction loses a certain amount of resolution, and optical correction usually uses aspheric surfaces or increases the complexity of the optical system without using aspheric surfaces (e.g., Chinese patent publication CN107102433B). For rigid endoscope optical tubes, especially otoscopes, sinusoscopes, arthroscopes, cystoscopes, etc., due to the strict limitations on lens size, these two optical correction methods will make processing and assembly more difficult, especially the processing of high-precision and extremely small-diameter glass aspheric lenses. Summary of the invention

[0003] The technical problem solved by the present application is to overcome the above-mentioned deficiencies in the prior art and to provide a design method for a rigid endoscope optical system with a simple structure and easy use, which can realize the small distortion imaging of the rigid endoscope imaging system.

[0004] The technical solution adopted by the present application to solve the above technical problems is: a design method for a small-distortion rigid endoscope optical system, based on the conventional design of a rigid endoscope optical tube (composed of an objective lens group, a rod lens relay group, and an eyepiece), a camera adapter is used to produce a distortion opposite to the front end, so that the distortion of the entire rigid endoscope optical system is corrected. The improved method of the present application comprises the following steps:

[0005] Step 1: Determine the parameters, discretize the field of view, and output the relative distortion value. Determine the combined focal length f of the objective lens group and the rod lens relay group 物 The overall half field of view of the combination of the objective lens group and the rod mirror relay group is θ 物 , eyepiece focal length f目 , Camera adapter focal length f 适 , use conventional design methods to complete the design of the optical tube part; 物 Discretize, each discrete field of view is (i, M are both positive integers, and i≤M); Output the combination of the objective lens group and the rod mirror relay group in each discrete field of view θ in the optical design software 物i The relative distortion value η 物i ;

[0006] Step 2: Calculate the discrete field of view corresponding to the camera adapter and the relative distortion it should produce. Use the following formula to determine the discrete field of view of the camera adapter θ 适i and the relative distortion value η of the camera adapter in each discrete field of view 适i The relative distortion of the camera adapter obtained by this formula can offset the relative distortion of the corresponding field of view of the optical tube, thus realizing the design of the overall small distortion of the rigid endoscope optical system;

[0007]

[0008]

[0009] Step 3: Calculate the actual image height that the camera adapter should achieve. Use the following formula to calculate the actual image height corresponding to each discrete field of view of the camera adapter under the condition of distortion compensation, and use this as the design target in the optical design software to complete the camera adapter design;

[0010] Y 适i =(1+η 适i )f 适 tanθ 适i (Formula 3)

[0011] Step 4: The above-mentioned camera adapter is coaxially arranged behind the optical tube of the rigid endoscope to form a small-distortion rigid endoscope optical system, and the distortion phase offset of the small-distortion rigid endoscope optical system is verified.

[0012] The camera adapter described in the present application consists of a front protective glass, lens one, lens two, lens three, lens four, lens five, lens six, lens seven, lens eight, lens nine, and a rear protective glass which are coaxially installed in sequence, and the front protective glass and the rear protective glass are flat-plate structures.

[0013] The beneficial effects brought by the present application are as follows: the present application generates distortion opposite to that of the optical view tube through a camera adapter, and performs distortion correction, thereby achieving the effect of a large field of view and small distortion of a rigid endoscope; the distortion correction of the present application is achieved by improving the camera adapter, and the size of the lens is not strictly limited compared to the part inserted into the human body. Compared with the design method of performing distortion correction at the end of the optical view tube where the lens size is strictly limited, the processing and assembly difficulty is lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the grid distortion of the combination of the objective lens group and the rod lens relay group.

[0015] Figure 2 This is a schematic diagram of the grid distortion of the eyepiece.

[0016] Figure 3 It is a schematic diagram of the optical sight tube grid distortion of the objective lens group, rod lens relay group, and eyepiece combination.

[0017] Figure 4 It is a schematic diagram of the structure of a camera adapter according to an embodiment of the present application.

[0018] Figure 5 Schematic diagram of grid distortion of the camera adapter according to the embodiment of the present application.

[0019] Figure 6 It is a schematic diagram of grid distortion after the optical viewing tube and the camera adapter are combined in the embodiment of the present application. DETAILED DESCRIPTION

[0020] The present application is further described in detail below with reference to the accompanying drawings and examples. The following examples are explanations of the present application and the present application is not limited to the following examples. Figure 4 The left side is the front and the right side is the back.

[0021] See also Figure 1 to Figure 6 The design method of the small distortion rigid endoscope optical system of the present application embodiment includes the following steps:

[0022] Step 1: Determine the parameters, discretize the field of view, and output the relative distortion value. The combined focal length f of the objective lens group and the rod lens relay group is 物 =1.65mm, the overall half field of view of the objective lens group and the rod lens relay group 物 =40°, eyepiece focal length f 目 =15.9mm, focal length of camera adapter f 适 = 20mm. The design of the optical tube is completed by conventional design methods. The grid distortion of the combination of the objective lens group and the rod lens relay group is as follows: Figure 1 As shown, its maximum relative distortion is -22.5%; the grid distortion of the eyepiece is as follows Figure 2 As shown, the absolute value of its maximum relative distortion is less than 0.1%; the grid distortion of the optical tube of the objective lens group, rod lens relay group, and eyepiece combination is as follows Figure 3 As shown, the distortion introduced by the eyepiece can be ignored. 物 Discretize, each discrete field of view is (i, M are both positive integers, and i≤M), let M = 10, output the combination of the objective lens group and the rod mirror relay group in each discrete field of view θ in the optical design software 物i The relative distortion value η 物i , as shown in the following table;

[0023] <![CDATA[θ 物i ]]> <![CDATA[η 物i ]]> i＝1 4° -0.22％ i＝2 8° -0.89％ i＝3 12° -2.01％ i＝4 16° -3.58％ i＝5 20° -5.60％ i＝6 24° -8.07％ i＝7 28° -11.00％ i＝8 32° -14.39％ i＝9 36° -18.22％ i＝10 40° -22.5％

[0024] Step 2: Calculate the discrete field of view corresponding to the camera adapter and the relative distortion it should produce. Use the following formula to determine the discrete field of view of the camera adapter θ 适i and the relative distortion value η of the camera adapter in each discrete field of view 适i As shown in the following table, the relative distortion of the camera adapter obtained by this formula can offset the relative distortion of the corresponding field of view of the optical tube, thus realizing the design of the overall small distortion of the rigid endoscope optical system;

[0025]

[0026]

[0027] <![CDATA[θ 适i ]]> <![CDATA[η 适i ]]> i＝1 0.415 0.22％ i＝2 0.828 0.90％ i＝3 1.238 2.05％ i＝4 1.644 3.71％ i＝5 2.042 5.93％ i＝6 2.432 8.78％ i＝7 2.811 12.36％ i＝8 3.178 16.80％ i＝9 3.528 22.28％ i＝10 3.861 29.03％

[0028] Step 3: Calculate the actual image height Y that the camera adapter should achieve 适i As shown in the following table, the actual image height corresponding to each discrete field of view of the camera adapter under the condition of distortion compensation is calculated using the following formula. This is used as the design goal in the optical design software to complete the camera adapter design. The designed camera adapter is as follows: Figure 4 As shown, the camera adapter is composed of a front protective glass 1, a lens 1 2, a lens 2 3, a lens 3 4, a lens 4 5, a lens 5 6, a lens 6 7, a lens 7 8, a lens 8 9, and a rear protective glass 10, which are coaxially arranged in sequence. The front protective glass 1 and the rear protective glass 10 are both flat-plate structures, and the image plane 12 is on the far right. The grid distortion is as follows: Figure 5 shown.

[0029] Y 适i =(1+η 适i )f 适 tanθ 适i (Formula 3)

[0030]

[0031]

[0032] Step 4: Combine the optical tube and the camera adapter to verify the distortion offset. Combine the optical tube and the camera adapter in the optical design software to obtain the grid distortion of the entire system. Figure 6As shown, it can be seen that the maximum relative distortion of the system as a whole does not exceed 1.18%, which shows that the distortion has been well corrected.

[0033] As a special case, the specific parameters of each optical element in the embodiment of the present application are as follows, wherein the spacing of an optical element refers to the distance between the center of the rear surface of the optical element and the center of the front surface of the next optical element (or image plane):

[0034] Figure 4 Winning bid number Optical Component Thickness and / or Spacing (mm) Glass material 1 1 SAPPHIRE 0.37 2 2 H-BAF3 7.08 3 1 H-ZLAF78B 9.1 4 1.44 H-FK71 0.37 5 0.5 H-ZF72A 7.58 6 0.5 H-ZLAF55C 2.32 7 1.88 H-FK61 0.94 8 2.76 H-ZLAF52A 0.1 9 1.96 H-LAF1 0.1 10 1 SAPPHIRE 5 11 Image plane

[0035] Any simple deformation or combination of the technical features and technical solutions of this application should be considered to fall within the protection scope of this application.

Claims

1. A design method for a small-distortion rigid endoscope optical system. Features The steps include: Step 1: Determine the parameters, discrete field of view, output relative distortion value, and determine the combined focal length f of the objective lens group and the rod lens relay group 物 The overall half field of view of the combination of the objective lens group and the rod mirror relay group is θ 物 , eyepiece focal length f 目 , Camera adapter focal length f 适 , use conventional design methods to complete the design of the optical tube part; 物 Discretize, each discrete field of view is Where i and M are both positive integers, and i≤M; Output the combination of the objective lens group and the rod lens relay group in each discrete field of view θ in the optical design software 物i The relative distortion value η 物i ; Step 2: Calculate the discrete field of view corresponding to the camera adapter and the relative distortion it should produce. Use the following formula to determine the discrete field of view θ of the camera adapter: 适i and the relative distortion value η of the camera adapter in each discrete field of view 适i The relative distortion of the camera adapter obtained by this formula can offset the relative distortion of the corresponding field of view of the optical tube, thus realizing the design of the overall small distortion of the rigid endoscope optical system; Step 3: Calculate the actual image height that the camera adapter should achieve. Use the following formula to calculate the actual image height Y corresponding to each discrete field of view of the camera adapter under the condition of distortion compensation: 适i , taking this as the design goal in the optical design software, the camera adapter design is completed; Y 适i = (1 + η 适i ) f 适 tan θ 适i (Equation 3) Step 4: The camera adapter is coaxially installed behind the optical tube of the rigid endoscope to form a small-distortion rigid endoscope optical system, and the distortion phase offset of the small-distortion rigid endoscope optical system is verified.

2. The method for designing a small-distortion rigid endoscope optical system according to claim 1, Its characteristics are: The camera adapter is composed of a front protective glass, a lens 1, a lens 2, a lens 3, a lens 4, a lens 5, a lens 6, a lens 7, a lens 8, a lens 9 and a rear protective glass which are coaxially arranged in sequence. The front protective glass and the rear protective glass are flat plate structures.

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