Endoscope and objective lens system thereof

Abstract

The invention discloses an endoscope and an objective lens system thereof, and relates to the technical field of endoscopes. The objective lens system sequentially comprises a first lens group with negative focal power, a second lens group with positive focal power and a third lens group with positive focal power from an object side to an image side, and focusing of the objective lens system is realized by moving the second lens group along an optical axis. Wherein the second lens group comprises a positive first lens and a negative second lens, and the first lens and the second lens are respectively positioned at two sides of the diaphragm, so that most of the phase difference generated by the first lens and the second lens can be mutually offset, and the aberration change caused by the focusing process is less; therefore, images with good performance can be obtained in a wide observation range.

Description

Technical Field

[0001] The present invention relates to the technical field of endoscopes, and in particular to an endoscope and an objective lens system thereof. Background Art

[0002] In the medical field, an endoscope inserted into a body cavity can be used to obtain images of various parts of the body cavity, which can help doctors diagnose lesions effectively. When using an endoscope for observation, it is expected that good images can be obtained in a wide observation range from close-up to distant views.

[0003] In the related art, the observation depth range of the endoscope is adjusted by adjusting the aperture value (hereinafter referred to as F number). In order to expand the observation depth, the aperture is usually reduced, but increasing the observation depth by reducing the aperture will cause the Modulation Transfer Function (MTF) of the objective system to decrease, and it is impossible to ensure that the endoscope objective system has good optical performance.

[0004] It can be seen that how to obtain images with good performance within a wide observation range is a technical problem that people in this field need to solve urgently. Summary of the invention

[0005] The object of the present invention is to provide an endoscope and an objective lens system thereof, which can obtain images with good performance in a wide observation range.

[0006] In order to solve the above technical problems, the present invention provides an objective lens system, comprising: a first lens group with negative optical power, a second lens group with positive optical power and a third lens group with positive optical power, which are arranged in sequence from the object side to the image side of the objective lens system, and focusing is performed by moving the second lens group along the optical axis;

[0007] The second lens group includes a positive first lens and a negative second lens;

[0008] The objective lens system further includes an aperture stop disposed between the first lens and the second lens.

[0009] Exemplarily, during focusing, the aperture moves together with the first lens and the second lens.

[0010] Exemplarily, during the focusing process, the relative positions of the aperture and the first lens and the second lens remain unchanged.

[0011] Exemplarily, the objective lens system satisfies the following conditional formula:

[0012] -2.0 <f5 / f4,

[0013] Wherein, f4 is the focal length of the first lens, and f5 is the focal length of the second lens.

[0014] Exemplarily, the objective lens system satisfies the following conditional formula:

[0015] -2.0 <f5 / f4<-0.6。

[0016] Exemplarily, the image-side surface of the first lens is bent toward the object side, and / or the image-side surface of the second lens is bent toward the image side.

[0017] Exemplarily, the first lens group includes a third lens and a first cemented lens with negative optical power, wherein the third lens is a negative lens, and the first cemented lens includes a fourth lens and a fifth lens cemented in sequence from the object side to the image side, the fourth lens is a negative lens, and the fifth lens is a positive lens.

[0018] Exemplarily, the objective lens system satisfies the following conditional formula:

[0019] f 23 / f G1 >8,

[0020] Among them, f 23 is the focal length of the first doublet lens, f G1 is the focal length of the first lens group.

[0021] Exemplarily, the third lens group includes a sixth lens and a second cemented lens with positive optical power, wherein the sixth lens is a positive lens, and the second cemented lens includes a seventh lens and an eighth lens cemented in sequence from the object side to the image side, the seventh lens is a positive lens, and the eighth lens is a negative lens.

[0022] In order to solve the above technical problems, the present invention also provides an endoscope, comprising the above objective lens system.

[0023] The objective lens system provided by the present invention comprises: a first lens group with negative optical focal length, a second lens group with positive optical focal length and a third lens group with positive optical focal length which are sequentially arranged from the object side to the image side of the objective lens system, and focusing is performed by moving the second lens group along the optical axis; the second lens group comprises a positive first lens and a negative second lens; the objective lens system further comprises an aperture stop which is arranged between the first lens and the second lens.

[0024] In the objective lens system, firstly, by moving the second lens group along the optical axis, the focusing function of the objective lens system is realized, and the state of long-range observation and the state of close-range observation can be switched, thereby expanding the range of observation depth, and thus an image with a wide observation range can be obtained; secondly, compared with the previous method of expanding the observation depth by reducing the aperture, in the objective lens system provided by the present invention, since the observation range is expanded by focusing the objective lens system, the objective lens system can adopt a large aperture design, and the aperture remains basically unchanged before and after focusing, which greatly improves the MTF of the objective lens system and improves the optical performance of the objective lens system; thirdly, the first lens group in the objective lens system has a high negative focal length, which is conducive to realizing the wide-angle of the objective lens system, and the size of the field of view angle remains almost unchanged during the focusing process, thereby ensuring a wider field of view within the entire observation range; in addition, the first lens and the second lens in the second lens group for focusing are located on both sides of the aperture, and the phase difference generated by the two can offset most of each other, thereby reducing the aberration change caused by the focusing process, and thus obtaining an image with good performance within a wide observation range.

[0025] In addition, the present invention also provides an endoscope having the same or corresponding technical features as the above-mentioned objective lens system and having the same effects as above. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 A schematic diagram of the structure of an objective lens system in a long-range observation state provided by an embodiment of the present invention;

[0028] Figure 2 A schematic structural diagram of an objective lens system in a close-up observation state provided by an embodiment of the present invention;

[0029] Figure 3 for Figure 1 Schematic diagram of field curvature and astigmatism of the objective lens system shown;

[0030] Figure 4 for Figure 2 Schematic diagram of field curvature and astigmatism of the objective lens system shown;

[0031] Figure 5 for Figure 1 The vertical axis chromatic aberration curve of the objective lens system shown;

[0032] Figure 6 for Figure 2The vertical axis chromatic aberration curve of the objective lens system shown;

[0033] Figure 7 for Figure 1 The MTF curve of the objective system shown;

[0034] Figure 8 for Figure 2 The MTF curve of the objective system is shown. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The core of the present invention is to provide an endoscope and an objective lens system thereof, which can obtain images with good performance in a wide observation range.

[0037] In the medical field, an endoscope inserted into a body cavity is used to obtain images of various parts of the body cavity, which can help doctors effectively diagnose lesions. When using an endoscope for observation, the objective lens system provided by the present invention has a focusing function, so that images focused within a wide observation range from near view to far view can be obtained during observation.

[0038] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0039] The objective lens system provided by the embodiment of the present invention comprises: a first lens group with negative optical power, a second lens group with positive optical power and a third lens group with positive optical power which are sequentially arranged from the object side to the image side of the objective lens system, and focusing is performed by moving the second lens group along the optical axis;

[0040] The second lens group includes a positive first lens and a negative second lens;

[0041] The objective lens system further includes an aperture stop which is disposed between the first lens and the second lens.

[0042] In the embodiment of the present invention, the objective lens system adopted includes a first lens group, a second lens group, and a third lens group. There is no limitation on the specific positions of the lens groups in the objective lens system, as long as the first lens group, the second lens group, and the third lens group are arranged in sequence from the object side to the image side; there is no limitation on the number of lenses, the type of lenses, etc. in each lens group, as long as the first lens group has a negative optical power, the second lens group has a positive optical power, and the third lens group has a positive optical power. The second lens group adopted in the embodiment of the present invention includes a first lens and a second lens, wherein the first lens is a positive lens and the second lens is a negative lens.

[0043] In order to have a wider field of view within the observation range, the first lens group arranged at the position closest to the object side is a lens group with a high negative optical power.

[0044] In order to observe images in a large range from near to far, in the embodiment of the present invention, by arranging a second lens group that can move along the optical axis between the first lens group and the third lens group, the focusing function of the objective lens system is realized. It should be noted that while the second lens group moves, the third lens group can move or remain stationary. If the third lens group also moves while the second lens group moves, it will lead to a more complex mechanical structure design of the entire objective lens system. Therefore, in implementation, in order to reduce the mechanical structure of the objective lens system, the preferred implementation method is that while the second lens group moves, both the first lens group and the third lens group remain stationary. Since a large range of observation is achieved through the focusing method, compared with the previous method of expanding the depth of observation by reducing the aperture, the objective lens system in this embodiment has a large aperture, and the aperture size hardly changes during focusing, greatly improving the MTF of the objective lens system and enhancing the performance of the objective lens system; in addition, the field of view angle of the objective lens system remains unchanged during the focusing process, ensuring a wide field of view within the entire observation range.

[0045] When the second lens group moves, it will cause changes in aberrations (especially field curvature), resulting in a decrease in the imaging quality and optical performance of the objective lens system. In order to suppress the changes in aberrations (especially field curvature) caused by the movement of the second lens group, in this embodiment, the aperture stop of the objective lens system is arranged between the positive first lens and the negative second lens. In this way, most of the phase differences generated by the first lens and the second lens can cancel each other out, so that the aberration changes caused by the focusing process are less, and thus images with good performance can be obtained within a wide observation range.

[0046] In order to further reduce the aberration changes caused by the movement of the second lens group, in some embodiments, the objective lens system can satisfy the following conditional formula: -2.0 < f5 / f4, where f4 is the focal length of the first lens and f5 is the focal length of the second lens.

[0047] In addition, if the ratio of f5 to f4 is too large, it may cause excessive suppression of aberration variation or the lateral dimension of the objective lens system to become too large. Therefore, in some embodiments, the objective lens system satisfies the following conditional expression: -2.0 < f5 / f4 < -0.6.

[0048] When below the lower limit of the conditional expression, it is difficult to effectively suppress the aberration variation caused by the movement of the lens group or the length of the objective lens system is too long; when above the upper limit of the conditional expression, it will cause the lateral dimension of the objective lens system to become too large.

[0049] It can be seen that in the objective lens system provided in this embodiment, the focal length f4 of the first lens and the focal length f5 of the second lens in the second lens group satisfy -2.0 < f5 / f4 < -0.6, which can effectively suppress the aberration variation caused by the movement of the second lens group. At the same time, it avoids the excessive length of the objective lens system and the excessive lateral dimension of the objective lens system.

[0050] Similarly, in order to suppress the variation of aberration (especially field curvature) caused by the movement of the second lens group, the image side surface of the first lens is bent towards the object side (that is, the image side surface of the first lens bulges towards the image side), and / or the image side surface of the second lens is bent towards the image side (that is, the image side surface of the second lens bulges towards the object side).

[0051] During the focusing process, the aperture stop can move together with the first lens and the second lens. There is no limitation on the relative positions of the aperture stop, the first lens, and the second lens. During the movement, in order to simplify the mechanical structure design of the second lens group and even the entire objective lens system, exemplarily, during the focusing process, the relative positions of the aperture stop, the first lens, and the second lens remain unchanged.

[0052] In order to correct the aberration of the entire objective lens system (regardless of the long-distance state or the short-distance state), in this embodiment, the first lens group includes a third lens and a first cemented lens with negative optical power. Among them, the third lens is a negative lens, for example, it can be a plano-concave lens with a plane object side surface. The first cemented lens includes a fourth lens and a fifth lens cemented together in sequence from the object side to the image side. The fourth lens is a negative lens, and the fifth lens is a positive lens.

[0053] By adding the first cemented lens to the first lens group, aberration correction can be performed.

[0054] Furthermore, in order to achieve a better aberration correction effect, the objective lens system can satisfy the following conditional expression:

[0055] f 23 / f G1 >8,

[0056] wherein, the focal length of the first cemented lens is f 23 , and the focal length of the first lens group is fG1 .

[0057] In order to further correct the aberration of the objective lens system, in this embodiment, the third lens group includes a sixth lens and a second cemented lens with positive optical power, wherein the sixth lens is a positive lens, and the second cemented lens includes a seventh lens and an eighth lens cemented in sequence from the object side to the image side, the seventh lens is a positive lens, and the eighth lens is a negative lens.

[0058] The third lens group converges the divergent light beams passing through the first lens group and the second lens group and forms an image on the image plane, while correcting the residual aberrations of the objective system, especially chromatic aberration, thereby improving the performance of the objective system.

[0059] In practice, in order to reduce the difficulty of manufacturing each lens, each lens in the first lens group, each lens in the second lens group, and each lens in the third lens group in this embodiment are all non-concentric lenses.

[0060] In summary, it can be seen that in the objective lens system provided by the embodiment of the present invention, firstly, by moving the second lens group along the optical axis, the focusing function of the objective lens system is realized, and it can be switched between the long-range observation state and the close-range observation state, thereby expanding the observation depth range, and thus an image with a wide observation range can be obtained; secondly, compared with the previous method of expanding the observation depth by reducing the aperture, in the objective lens system provided by the embodiment of the present invention, since the observation range is expanded by focusing the objective lens system, the objective lens system can adopt a large aperture design, and the aperture remains basically unchanged before and after focusing, which greatly improves the MTF of the objective lens system and improves the optical performance of the objective lens system; thirdly, the first lens group in the objective lens system has a high negative focal length, which is conducive to realizing the wide-angle of the objective lens system, and the field angle remains almost unchanged during the focusing process, thereby ensuring a wider field of view within the entire observation range; in addition, the first lens and the second lens in the second lens group used for focusing are located on both sides of the aperture, and the phase difference generated by the two can offset most of each other, so that the aberration caused by the focusing process changes less, and thus a good performance image can be obtained within a wide observation range.

[0061] In order to enable those skilled in the art to better understand the solution of the present invention, the objective lens system provided by the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0062] Figure 1 A schematic diagram of the structure of an objective lens system in a long-range observation state provided by an embodiment of the present invention, Figure 2 A schematic diagram of the structure of an objective lens system in a close-up observation state provided by an embodiment of the present invention is shown in FIG. Figure 1 and Figure 2As shown in the figure, the objective lens system includes, from left to right, a first lens group G1 with negative optical power, a second lens group G2 with positive optical power, and a third lens group G3 with positive optical power. Among them, the second lens group G2 includes a first lens L4 with positive optical power and a second lens L5 with negative optical power. The image-side surface of the first lens L4 is bent towards the object side, and the image-side surface of the second lens L5 is bent towards the image side. The conditional formula satisfied by the focal length f4 of the first lens L4 and the focal length f5 of the second lens L5 is -0.2 < f5 / f4 < -0.6. An aperture stop ST is placed between the first lens L4 and the second lens L5. The aperture stop ST can move together with the second lens group G2, and the relative positions with the first lens L4 and the second lens L5 remain unchanged during the movement; the first lens group G1 includes a third lens L1 with negative optical power, a fourth lens L2 with negative optical power, and a fifth lens L3 with positive optical power. The fourth lens L2 and the fifth lens L3 are sequentially cemented from the object side to form a first cemented lens with negative optical power. The focal length f G1 of the first lens group G1 and the focal length f 23 of the first cemented lens satisfy the following conditional formula: f 23 / f G1 > 8; the third lens group G3 includes a sixth lens L6 with positive optical power, a seventh lens L7 with positive optical power, and an eighth lens L8 with negative optical power. The seventh lens L7 and the eighth lens L8 are sequentially cemented from the object side to form a second cemented lens with positive optical power. IMG represents the image plane. Moving the second lens group G2 in Figure 1 to the right (the moved figure is as shown in Figure 2 ) realizes the switching from the long-distance viewing state to the close-up viewing state. During the switching process, the first lens group G1, the third lens group G3, and the image plane IMG all remain stationary. Table 1 shows the detailed design data (unit: millimeter) of the objective lens system shown in Figure 1 and Figure 2 .

[0063] Table 1 Detailed Design Data of the Objective Lens System

[0064]

[0065] Table 2 shows the specifications of the objective lens system, including the detailed system specifications under long-distance viewing and close-up viewing: F-number, field angle (unit: degree), object distance D0 (unit: millimeter), group spacing D5 (unit: millimeter), group interval D10 (unit: millimeter), and effective focal length (EFFL). Among them, the group interval D5 is the distance between the first lens group G1 and the second lens group G2 (i.e., the distance between the fifth lens L3 and the first lens L4), and the group interval D10 is the distance between the second lens group G2 and the third lens group G3 (i.e., the distance between the second lens L5 and the sixth lens L6).

[0066] Table 2 Objective system specifications

[0067]

[0068] D0, D5 and D10 change in accordance with the two observation states. Figure 1 In Figure 2 The objective lens system provided in the paper is further analyzed. Figure 3 for Figure 1 The field curvature and astigmatism diagram of the objective lens system shown in the figure. Figure 4 for Figure 2 Schematic diagram of field curvature and astigmatism of the objective system shown. Figure 3 , Figure 4 The solid line in the figure is the meridian direction, and the dotted line is the sagittal direction. Figure 5 for Figure 1 The vertical axis chromatic aberration curve of the objective system shown is Figure 6 for Figure 2 The vertical axis chromatic aberration curve of the objective system shown is Figure 7 for Figure 1 The MTF curve of the objective system shown is Figure 8 for Figure 2 The MTF curve of the objective system is shown.

[0069] It can be seen that the objective lens system provided in the embodiment of the present invention can realize the focusing function of the objective lens system through the second lens group G2 moving along the optical axis, switch between the long-range observation state and the close-range observation state, and expand the observation depth range. During the focusing process, the field angle of the objective lens system remains unchanged, so that a wider field of view is provided in the entire observation range; the aperture of the objective lens system remains basically unchanged, and a large aperture is provided in the entire observation range, and the aberration caused by focusing changes less and is well corrected for aberration, thereby improving the optical performance of the objective lens system; in addition, there is no lens close to concentric circles in the objective lens system, and the lens processing and manufacturing are simple.

[0070] An objective lens system is described above, and this embodiment further provides an endoscope, including the objective lens system. The objective lens system provided above can be used as an objective lens system of an endoscope, and the embodiment of the objective lens system has been described in detail above, and the embodiment of the endoscope is not repeated here, and has the same beneficial effects as the objective lens system mentioned above.

[0071] The above is a detailed introduction to an endoscope and an objective lens system provided by the present invention. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0072] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

Claims

1. An objective lens system, characterized in that: include: A first lens group with negative optical power, a second lens group with positive optical power and a third lens group with positive optical power are sequentially arranged from the object side to the image side of the objective lens system, and focusing is performed by moving the second lens group along the optical axis; The second lens group includes a positive first lens and a negative second lens; The objective lens system further includes an aperture stop disposed between the first lens and the second lens.

2. The objective lens system according to claim 1, characterized in that During focusing, the aperture stops move together with the first lens and the second lens.

3. The objective lens system according to claim 2, characterized in that During the focusing process, the relative positions of the aperture and the first lens and the second lens remain unchanged.

4. The objective lens system according to any one of claims 1 to 3, characterized in that: The objective lens system satisfies the following conditional formula: -2.0 <f5 / f4, Wherein, f4 is the focal length of the first lens, and f5 is the focal length of the second lens.

5. The objective lens system according to claim 4, characterized in that The objective lens system satisfies the following conditional formula: -2.0 <f5 / f4<-0.6。 6. The objective lens system according to claim 4, characterized in that The image-side surface of the first lens is bent toward the object side, and / or the image-side surface of the second lens is bent toward the image side.

7. The objective lens system according to claim 4, characterized in that The first lens group includes a third lens and a first cemented lens with negative optical power, wherein the third lens is a negative lens, and the first cemented lens includes a fourth lens and a fifth lens cemented in sequence from the object side to the image side, the fourth lens is a negative lens, and the fifth lens is a positive lens.

8. The objective lens system according to claim 7, characterized in that The objective lens system satisfies the following conditional formula: f 23 / f G1 >8, Among them, f 23 is the focal length of the first doublet lens, f G1 is the focal length of the first lens group.

9. The objective lens system according to claim 7, characterized in that The third lens group includes a sixth lens and a second cemented lens with positive power, wherein the sixth lens is a positive lens, and the second cemented lens includes a seventh lens and an eighth lens cemented in sequence from the object side to the image side, the seventh lens is a positive lens, and the eighth lens is a negative lens.

10. An endoscope, characterized in that: An objective lens system comprising any one of claims 1 to 9.

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