Optical system and endoscope

Abstract

The application discloses an optical system, which comprises a first lens group, a second lens group and a third lens group, the first lens group and the third lens group are fixed along an optical axis, the second lens group is connected with a traction mechanism and can move to a first position, a second position or a third position along the optical axis under traction of the traction mechanism, so that the optical system enters a long-focus imaging state, a relay imaging state or a wide-angle imaging state, the depth of field of the optical system in the long-focus imaging state and the depth of field of the optical system in the relay imaging state are continuous, and the depth of field of the optical system in the relay imaging state and the depth of field of the optical system in the wide-angle imaging state are continuous. The optical system can perform wide-angle imaging and long-focus imaging, and the depth of field is continuous, so that the defects of the prior art can be made up. The application further discloses an endoscope.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical systems, in particular to an optical system. The present application also relates to an endoscope. BACKGROUND

[0002] In the medical field, an endoscope can help doctors effectively determine the lesion area and the lesion degree in a body cavity as an examination and treatment device. With the development and progress of science and technology, higher magnification or higher optical resolution is required for the endoscope, so as to enable more detailed and accurate observation of the lesion area, so as to determine the benignity and malignancy of the lesion.

[0003] An endoscope with magnification function can have a very high image magnification, and can observe the microstructure and microvessels of the mucosa surface of the cavity, and is used to identify the degree and benignity and malignancy of the mucosa lesion, and has important clinical application value. Therefore, the magnification endoscope has wide application.

[0004] However, in the actual application process, the present application inventors found that: the existing magnification endoscope usually has only two imaging states: wide-angle imaging state and long-focus imaging state, which are respectively used for wide-angle observation and long-focus observation of the lesion area. The depth of field is discontinuous in the two observation states, and there is a depth of field blind area. For example, the depth of field in the wide-angle observation state is 7-100mm, and the depth of field in the long-focus observation state is 1.5-3mm, so that the doctor cannot observe the area within the distance of 3-7mm in actual use, which causes great inconvenience to the actual use and poor user experience. SUMMARY

[0005] The purpose of the present application is to provide an optical system which can perform wide-angle imaging and long-focus imaging, and the depth of field is continuous, which can make up for the shortcomings of the prior art. The present application also provides an endoscope.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0007] An optical system, comprising a first lens group, a second lens group and a third lens group arranged in sequence along an optical axis, the first lens group is close to the object side, and the third lens group is close to the image side:

[0008] The positions of the first lens group and the third lens group along the optical axis are fixed, and the second lens group is connected with a traction mechanism and can be moved to a first position, a second position or a third position along the optical axis under the traction of the traction mechanism, so that the optical system corresponds to enter a long-focus imaging state, a relay imaging state or a wide-angle imaging state;

[0009] The depth of field of the optical system in the long-focus imaging state and the depth of field of the optical system in the relay imaging state are continuous, and the depth of field of the optical system in the relay imaging state and the depth of field of the optical system in the wide-angle imaging state are continuous.

[0010] Preferably, the position of the image plane of the optical system along the optical axis is fixed.

[0011] Preferably, the optical system further comprises a diaphragm arranged between the first lens group and the second lens group.

[0012] Preferably, the optical system satisfies the following conditional expression:

[0013] 2.5 < M M / M W < 3.5, and / or,

[0014] 1.9 < M T / M M < 2.3, and / or,

[0015] 1.9 < (f T +f W ) / f M < 2.1, and / or,

[0016] 1.0 < f T / f W < 1.2,

[0017] wherein M W represents the optical magnification of the optical system in the wide-angle imaging state, M M represents the optical magnification of the optical system in the relay imaging state, M T represents the optical magnification of the optical system in the long-focus imaging state, f W represents the effective focal length of the optical system in the wide-angle imaging state, f M represents the effective focal length of the optical system in the relay imaging state, f T represents the effective focal length of the optical system in the long-focus imaging state.

[0018] Preferably, the optical system satisfies the following conditional expression:

[0019] 1.4 < f1 / f2 < 2.5, and / or,

[0020] 1.5 < f3 / f2 < 2.6,

[0021] wherein f1 represents the focal length of the first lens group, f2 represents the focal length of the second lens group, and f3 represents the focal length of the third lens group.

[0022] Preferably, the optical system satisfies the following conditional expression: 0.15 < θ T2 / θ T1 < 0.25, wherein, θ T1 represents a field angle of the optical system in a long-focus imaging state, and θ T2 represents an angle of incidence of a light ray on an image plane of the optical system in the long-focus imaging state.

[0023] Preferably, the first lens group has positive refractive power, the second lens group has positive refractive power, and the third lens group has positive refractive power.

[0024] Preferably, the first lens group includes a first lens and a second lens, the first lens has positive refractive power, and the second lens has positive refractive power.

[0025] Preferably, the second lens group includes a third lens, and the third lens has positive refractive power.

[0026] Preferably, the third lens group includes a fourth lens, a fifth lens, and a sixth lens, the fourth lens has positive refractive power, the fifth lens has negative refractive power, and the sixth lens has negative refractive power.

[0027] An endoscope includes an optical system and an imaging chip, the imaging chip is disposed at an image plane of the optical system, and the optical system is the optical system described above.

[0028] As can be seen from the above technical solution, the optical system provided by the application includes a first lens group, a second lens group, and a third lens group arranged in sequence along an optical axis, wherein the first lens group and the third lens group are fixed in position along the optical axis, the second lens group is connected with a traction mechanism and can be moved to a first position, a second position, or a third position along the optical axis under traction of the traction mechanism, so that the optical system enters a long-focus imaging state, a relay imaging state, or a wide-angle imaging state, and the depth of field of the optical system in the long-focus imaging state and the depth of field of the optical system in the relay imaging state are continuous, and the depth of field of the optical system in the relay imaging state and the depth of field of the optical system in the wide-angle imaging state are continuous.

[0029] The optical system of the application includes a long-focus imaging state, a relay imaging state, and a wide-angle imaging state, the depth of field of the optical system in the long-focus imaging state and the depth of field of the optical system in the relay imaging state are continuous, and the depth of field of the optical system in the relay imaging state and the depth of field of the optical system in the wide-angle imaging state are continuous, so that the optical system can perform wide-angle imaging and long-focus imaging, and the depth of field is continuous, which can make up for the shortcomings of the prior art.

[0030] The endoscope provided by the application can achieve the above beneficial effects. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the accompanying drawings in the following description only aim to some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0032] Figure 1 A schematic view of an optical system provided by an embodiment of the present application in a long-focus imaging state;

[0033] Figure 2 A schematic view of an optical system provided by an embodiment of the present application in a long-focus imaging state; Figure 1

[0034] Figure 3 A schematic view of an optical system provided by an embodiment of the present application in a long-focus imaging state; Figure 1

[0035] Figure 4 An MTF curve of an optical system provided by an embodiment of the present application in a long-focus imaging state;

[0036] Figure 5 An MTF curve of an optical system provided by an embodiment of the present application in a long-focus imaging state;

[0037] Figure 6 An MTF curve of an optical system provided by an embodiment of the present application in a long-focus imaging state. DETAILED DESCRIPTION

[0038] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the accompanying drawings in the following description only aim to some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0039] The present embodiment provides an optical system, comprising a first lens group, a second lens group and a third lens group arranged along an optical axis in sequence, the first lens group is close to the object side, and the third lens group is close to the image side:

[0040] The positions of the first lens group and the third lens group along the optical axis are fixed, the second lens group is connected with a traction mechanism and can be moved to a first position, a second position or a third position along the optical axis under the traction of the traction mechanism, so that the optical system enters a long-focus imaging state, a relay imaging state or a wide-angle imaging state correspondingly;

[0041] ​​The depth of field of the optical system in the long-focus imaging state and the depth of field of the optical system in the relay imaging state are continuous, and the depth of field of the optical system in the relay imaging state and the depth of field of the optical system in the wide-angle imaging state are continuous.

[0042] Light from the object is sequentially imaged through the first lens group, the second lens group and the third lens group. As the second lens group moves along the optical axis, the field of view, the optical magnification and the depth of field of the optical system change.

[0043] The first position, the second position and the third position are three different positions on the optical axis, respectively. When the second lens group is in the first position, the optical system is in the long-focus imaging state; when the second lens group is in the second position, the optical system is in the relay imaging state; and when the second lens group is in the third position, the optical system is in the wide-angle imaging state. The field of view of the optical system in the wide-angle imaging state is greater than the field of view of the optical system in the other two states. The absolute value of the optical magnification of the optical system in the long-focus imaging state is greater than the absolute value of the optical magnification of the optical system in the other two states. The optical magnification of the optical system in any state refers to the ratio of the size of the object image formed on the image plane by the object in the paraxial region through the optical system in the state to the size of the object.

[0044] The depth of field of the optical system in any state refers to the range of object distance in which a satisfactory image can be obtained on the image plane when the optical system is in the state. The depth of field of the optical system in the long-focus imaging state and the depth of field of the optical system in the relay imaging state are continuous, which means that the minimum object distance of the depth of field of the optical system in the relay imaging state is less than or equal to the maximum object distance of the depth of field of the optical system in the long-focus imaging state. Similarly, the depth of field of the optical system in the relay imaging state and the depth of field of the optical system in the wide-angle imaging state are continuous, which means that the maximum object distance of the depth of field of the optical system in the relay imaging state is greater than or equal to the minimum object distance of the depth of field of the optical system in the wide-angle imaging state.

[0045] Therefore, the optical system of the embodiment can perform wide-angle imaging and long-focus imaging, and the depth of field is continuous, which can image and obtain clear images in the entire depth of field range from the wide-angle state to the long-focus state, and can make up for the shortcomings of the prior art.

[0046] Specifically, the traction mechanism can be any driving mechanism capable of moving the second lens group along the optical axis, one end of which is fixedly connected with the second lens group, and the other end is the control end. The specific implementation can refer to the prior art, which will not be described here. The first position, the second position and the third position can be arranged in order from the object side to the image side along the optical axis. When the second lens group moves from the object side to the image side along the optical axis, it can move to the first position, the second position and the third position in turn, and the corresponding optical system can be in the long-focus imaging state, the relay imaging state and the wide-angle imaging state in turn; conversely, when the second lens group moves from the image side to the object side along the optical axis, it can move to the third position, the second position and the first position in turn, and the optical system can be in the wide-angle imaging state, the relay imaging state and the long-focus imaging state in turn. In actual application, the second lens group can be moved according to the imaging needs of the object.

[0047] Generally, when moving a certain lens or a certain group of lenses in the optical system, the image plane position will change. If the position of the imaging chip is adjusted accordingly to adapt to the change of the image plane position, the control complexity of the optical system will be increased, and it is also difficult to adapt to the installation environment of the endoscope lens. Therefore, in the embodiments of the present application, the position of the image plane in the optical system along the optical axis is fixed and unchanged by optimizing the parameter design of each lens group in the optical system, that is, the image plane position of the optical system does not change during the movement of the second lens group to the first position, the second position or the third position. It should be understood that in the field of optics, the specific parameters in the optical system are determined by a plurality of optimization variables / limiting conditions. In actual application, as long as the structure of the optical system and the optimization variables (for example, keeping the image plane position unchanged) are given, the related optical design software can calculate the optical parameters that meet the requirements from the basic principles. Therefore, the specific design scheme for fixing the image plane position is not described in detail.

[0048] As can be seen from the above, in the present optical system, the positions of the first lens group, the third lens group and the image plane are all fixed, and only the second lens group needs to be moved, so that the optical system can be switched between the wide-angle imaging state, the relay imaging state and the long-focus imaging state, without occupying too much space and being easy to control.

[0049] Preferably, the optical system of the present embodiment satisfies the following conditional expression: 2.5 < M M / M W < 3.5, M M represents the optical magnification of the optical system in the relay imaging state, M Wrepresents the optical magnification of the optical system in the wide-angle imaging state. By satisfying the conditional expression, the design object distance of the relay imaging state of the optical system can be constrained, and the depth of field of the relay imaging state can be ensured to be continuous with the depth of field of the wide-angle imaging state and the depth of field of the long-focus imaging state. When the numerical value of the conditional expression is lower than the lower limit value, the depth of field of the relay imaging state will be biased to the wide-angle imaging state (i.e., biased to the far scene); when the numerical value of the conditional expression is higher than the upper limit value, the depth of field of the relay imaging state will be biased to the long-focus imaging state (i.e., biased to the near scene).

[0050] Preferably, the optical system of the embodiment satisfies the following conditional expression: 1.9 < M < 2.3. T / M M <2.3, M T represents the optical magnification of the optical system in the long-focus imaging state, M M represents the optical magnification of the optical system in the relay imaging state. By satisfying the conditional expression, the size of the optical magnification of the long-focus imaging state can be constrained: when the numerical value of the conditional expression is lower than the lower limit value, the optical magnification of the long-focus imaging state is too small, and the image magnification requirement of the long-focus imaging state cannot be met; when the numerical value of the conditional expression is higher than the upper limit value, the optical magnification of the long-focus imaging state is too large, and the field of view angle will be severely reduced.

[0051] Preferably, the optical system of the embodiment satisfies the following conditional expression: 1.9 < (f T +f W ) / f M <2.1, f W represents the effective focal length of the optical system in the wide-angle imaging state, f M represents the effective focal length of the optical system in the relay imaging state, f T represents the effective focal length of the optical system in the long-focus imaging state. By satisfying the conditional expression, the depth of field of the relay imaging state can be ensured to just fill the depth of field blind area between the wide-angle imaging state and the long-focus imaging state; when the numerical value is higher than the upper limit value, the depth of field of the relay imaging state will be biased to the wide-angle imaging state (i.e., biased to the far scene), and when the numerical value is lower than the lower limit value, the depth of field of the relay imaging state will be biased to the long-focus imaging state (i.e., biased to the near scene).

[0052] In the embodiment, by limiting the optical magnification relationship and the effective focal length relationship in the three imaging states, the depth of field of the relay imaging state can be ensured to just fill the depth of field blind area between the wide-angle imaging state and the long-focus imaging state.

[0053] Preferably, the optical system of the embodiment satisfies the following conditional expression: 1.0 < f T / f W <1.2, fW represents the effective focal length of the optical system in the wide-angle imaging state, f T represents the effective focal length of the optical system in the telephoto imaging state. By satisfying the conditional expression, the field of view in the telephoto imaging state can be prevented from being excessively reduced on the premise of realizing the telephoto imaging function, thereby facilitating system miniaturization. Specifically, when the value of the conditional expression is higher than the upper limit value, the field of view in the telephoto imaging state is greatly reduced, and the optical system length is greatly increased, which is not conducive to system miniaturization; when the value of the conditional expression is lower than the lower limit value, the optical system cannot realize the telephoto imaging function.

[0054] Preferably, the optical system of the present embodiment satisfies the following conditional expression: 1.4 < f1 / f2 < 2.5, f1 represents the focal length of the first lens group, and f2 represents the focal length of the second lens group. By satisfying the conditional expression, the optical system can better correct aberrations, and each lens group can equally bear the correction of aberrations, while avoiding excessive transverse size of the lens groups. When the value of the conditional expression is lower than the lower limit value, the angle of the incident light after being refracted by the first lens group changes too much, which is not conducive to aberration correction and can result in excessively high tolerance sensitivity of the optical system; when the value of the conditional expression is higher than the upper limit value, the transverse size of the first lens group is increased, which increases the burden of aberration correction of the second lens group and the third lens group.

[0055] Preferably, the optical system of the present embodiment satisfies the following conditional expression: 1.5 < f3 / f2 < 2.6, f2 represents the focal length of the second lens group, and f3 represents the focal length of the third lens group. By satisfying the conditional expression, the optical system can better correct aberrations, while avoiding excessive transverse size of the lens groups or increase of the total length of the optical system. When the value of the conditional expression is lower than the lower limit value, the third lens group cannot effectively correct the remaining aberrations of the optical system; when the value of the conditional expression is higher than the upper limit value, the transverse size of the third lens group is increased, and the total length of the optical system is increased, which is not conducive to system miniaturization.

[0056] Preferably, the optical system of the present embodiment satisfies the following conditional expression: 0.15 < θ T2 / θ T1 < 0.25, θ T1 represents the field of view of the optical system in the telephoto imaging state, θ T2 represents the angle of incidence of light on the image surface of the optical system in the telephoto imaging state. By restricting the angle of incidence of light on the image surface through the conditional expression, the optical system has a smaller total length, which is conducive to system miniaturization. When the value of the conditional expression is lower than the lower limit value, the angle of incidence of light on the image surface is too small, and the total length of the optical system is increased, which is not conducive to system miniaturization; when the value of the conditional expression is higher than the upper limit value, the angle of incidence of light on the image surface is too large, which is not conducive to aberration correction.

[0057] Optionally, the optical system of this embodiment may further include an aperture stop disposed between the first lens group and the second lens group. The aperture stop, disposed between the first and second lens groups, helps optimize aberrations in the optical system and facilitates the achievement of good imaging quality. The position of the aperture stop may remain unchanged as the second lens group moves to the first, second, or third position.

[0058] In this embodiment, the number of lenses, lens surface shapes, or spacing between lenses in the first, second, or third lens group are not limited, as long as the optical system can switch between telephoto imaging, relay imaging, and wide-angle imaging modes with continuous depth of field. Optionally, the first lens group, the second lens group, and the third lens group may have positive optical power.

[0059] Examples are available for reference. Figure 1 , Figure 1 This is a schematic diagram of an optical system in telephoto imaging mode according to an embodiment. As shown in the figure, the optical system includes a first lens group G1, a second lens group G2, and a third lens group G3 arranged sequentially from left to right. The first lens group G1 includes a first lens L1 and a second lens L2, both having positive optical power. The second lens group G2 includes a third lens L3, also having positive optical power. The third lens group G3 includes a fourth lens L4, a fifth lens L5, and a sixth lens L6, with the fourth lens L4 having positive optical power, the fifth lens L5 having negative optical power, and the sixth lens L6 having negative optical power. Table 1 below shows detailed optical data for the optical system of this embodiment (where the units for radius of curvature and thickness are millimeters). The surface number in the first column of the table corresponds to the surface number Sn (n is a natural number) in the schematic diagram of the optical system structure. The aperture stop ST is surface S5. The protective glass CG is located between the third lens group G3 and the image plane IMG.

[0060] Table 1

[0061]

[0062] For reference Figure 2 and Figure 3 , Figure 2 for Figure 1 The diagram shown illustrates the optical system in relay imaging mode. Figure 3 for Figure 1The optical system is in a wide-angle imaging state. Table 2 below is the detailed data of the optical system in the wide-angle imaging state, the relay imaging state, and the long-focus imaging state: effective F value, field of view angle (unit: degree), optical magnification, depth of field (unit: millimeter), object distance D0 (unit: millimeter), group interval D5 (unit: millimeter), and group interval D7 (unit: millimeter). Among them, the group interval D5 is the distance between the diaphragm (ST) and the second lens group G2, and the group interval D7 is the distance between the second lens group G2 and the third lens group G3. D0, D5, and D7 change corresponding to the three states.

[0063] Table 2

[0064] Wide field imaging state Relay imaging state Telephoto imaging state WFNO 6.4 6.9 7.8 Field of view 140 110 90 Optical power -0.08 -0.23 -0.49 Depth of field 7-100 3-7 1.5-3 D0 15.00 4.50 2.00 D5 1.55 1.00 0.05 D7 0.05 0.60 1.55

[0065] Please refer to Figure 4 , Figure 5 and Figure 6 , which are the MTF curves of the optical system of the embodiment in the long-focus imaging state, the relay imaging state, and the wide-angle imaging state, respectively. According to Figures 4-6 , it can be seen that the optical system of the embodiment can obtain better imaging effect in the three imaging states.

[0066] The embodiment also provides an endoscope, which comprises an optical system and an imaging chip, the imaging chip is arranged at an image plane of the optical system, and the optical system adopts the optical system described above.

[0067] The endoscope of the embodiment can realize the long-focus imaging state, the relay imaging state, and the wide-angle imaging state by adopting the optical system described above, wherein the depth of field in the long-focus imaging state and the depth of field in the relay imaging state are continuous, the depth of field in the relay imaging state and the depth of field in the wide-angle imaging state are continuous, therefore, the endoscope of the embodiment can perform wide-angle imaging and long-focus imaging, and the depth of field is continuous, which can make up for the deficiency of the prior art.

[0068] The endoscope of the embodiment adds the relay imaging state on the basis of the wide-angle imaging state and the long-focus imaging state of the conventional magnifying endoscope, makes up for the depth of field blind area of the conventional magnifying endoscope, effectively improves the use experience of doctors, and has high clinical application value.

[0069] The optical system and the endoscope provided by the embodiment are described in detail above. The principles and implementation manners of the embodiment are described by applying specific examples in this paper, and the description of the above embodiment is only used to help understand the method and the core idea of the embodiment. It should be pointed out that, for ordinary skilled persons in the technical field, some improvements and modifications can be made to the embodiment without departing from the principles of the embodiment, and these improvements and modifications also fall within the protection scope of the claims of the embodiment.

Claims

1. An optical system characterized by, The optical system comprises a first lens group, a diaphragm, a second lens group and a third lens group arranged in sequence along an optical axis, the first lens group is close to an object side, and the third lens group is close to an image side; The first lens group and the third lens group are fixed along the optical axis, the second lens group is connected with a traction mechanism and can be moved to a first position, a second position or a third position along the optical axis under the traction of the traction mechanism, so that the optical system enters a long-focus imaging state, a relay imaging state or a wide-angle imaging state, and the position of the diaphragm is unchanged during movement of the second lens group to the first position, the second position or the third position; The depth of field of the optical system in the long-focus imaging state and the depth of field of the optical system in the relay imaging state are continuous, and the depth of field of the optical system in the relay imaging state and the depth of field of the optical system in the wide-angle imaging state are continuous. The optical system satisfies the following conditional expression: 2.5 < M M / M W < 3.5; 1.9 < M T / M M <2.3; wherein M W represents the optical magnification of the optical system in the wide-angle imaging state, M M represents the optical magnification of the optical system in the relay imaging state, M T represents the optical magnification of the optical system in the long-focus imaging state.

2. The optical system of claim 1, wherein The position of an image plane of the optical system along the optical axis is fixed.

3. The optical system of claim 1, wherein The optical system satisfies the following conditional expression: 1.9 < (f T +f W ) / f M <2.1, and / or, 1.0 < f T / f W <1.2, wherein f W represents the effective focal length of the optical system in the wide-angle imaging state, f M represents the effective focal length of the optical system in the relay imaging state, f T represents the effective focal length of the optical system in the long-focus imaging state.

4. The optical system of claim 1, wherein The optical system satisfies the following conditional expression: 1.4 < f1 / f2 < 2.5, and / or, 1.5 < f3 / f2 < 2.6, wherein f1 represents a focal length of the first lens group, f2 represents a focal length of the second lens group, and f3 represents a focal length of the third lens group.

5. The optical system of claim 1, wherein The optical system satisfies the following conditional expression: 0.15 < θ T2 / θ T1 <0.25, wherein θ T1 represents the field angle of the optical system in the long-focus imaging state, θ T2 represents the angle of incidence of the light ray on the image plane of the optical system in the long-focus imaging state.

6. The optical system according to any one of claims 1 to 5, characterized in that The first lens group has positive refractive power, the second lens group has positive refractive power, and the third lens group has positive refractive power.

7. The optical system of claim 6, wherein, The first lens group comprises a first lens and a second lens, the first lens has positive refractive power, and the second lens has positive refractive power.

8. The optical system of claim 6, wherein, The second lens group comprises a third lens, and the third lens has positive refractive power.

9. The optical system of claim 6, wherein, The third lens group comprises a fourth lens, a fifth lens and a sixth lens, the fourth lens has positive refractive power, the fifth lens has negative refractive power, and the sixth lens has negative refractive power.

10. An endoscope characterized by comprising: The optical system comprises an optical system and an imaging chip, the imaging chip is arranged at an image plane of the optical system, and the optical system is the optical system according to any one of claims 1-9.

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