Optical module of a dual-mode stereoscopic endoscope

Abstract

The application discloses an optical module of a dual-mode stereoscopic endoscope, which is composed of two groups of optical sub-modules which are symmetrically arranged, have the same structure and are opposite to each other in light exit surface, and sequentially comprises a lens module for light imaging, a prism module for deflecting and splitting light and a sensor module for receiving two modes of light along an optical axis, wherein the advantage is that 3D imaging is realized by using two optical sub-modules to provide stereoscopic vision; the prism module is used to split and deflect light beams of different wave bands or different polarizations to realize a dual-mode imaging function and improve the system frame rate and target imaging accuracy; and by adjusting the performance parameters of the lens module, the structural design of the prism module and the placement direction of the sensor, the axial resolution of the endoscope can be improved while the small size is maintained.

Description

Technical Field

[0001] This invention relates to an optical module for an endoscope, and more particularly to an optical module for a dual-mode stereoscopic endoscope. Background Technology

[0002] Endoscopes are widely used in the medical field. With the development of medical equipment and related technologies, the requirements for the imaging performance and size of endoscopes are also increasing.

[0003] Firstly, with the coordinated development of endoscopic technology and surgical robotic systems, modern minimally invasive surgery is moving towards "fewer incisions and less trauma." Existing surgical robots typically have four robotic arms: one with a larger diameter image acquisition channel (approximately 10-11 mm), and three with smaller diameter instrument channels (approximately 8-9 mm). This difference limits the robot's potential for use in confined spaces. To reduce this difference and achieve diameter compatibility by matching the diameter of the image acquisition channel to that of the instrument channels, miniaturization of optical lenses and modules requires higher standards. Furthermore, to further improve diagnostic accuracy and the ease of operation in minimally invasive surgery, and to reduce the surgeon's learning curve, endoscopes are developing towards 3D stereoscopic vision and fluorescence imaging. Placing two lenses in parallel can simulate the effect of stereoscopic vision, ensuring not only clarity but also added depth information, which helps doctors quickly master relevant medical techniques. By using dyes to mark diseased tissues and then using fluorescence to clearly display their outlines, doctors can perform more precise resections, reducing damage to the patient's body and shortening the operation time. However, once the endoscope enters the human body, it needs to image the tissues. The clarity of the image will affect the doctor's ability to identify subtle pathological changes, while the axial resolution will affect the doctor's accuracy in distinguishing the hierarchical structure of the internal tissues. As an important indicator for evaluating the quality of endoscopic imaging, higher requirements are placed on these key parameters.

[0004] To address the miniaturization of endoscopes, Chinese utility model patent CN221888377U discloses a dual-mode imaging system achieved through the alternating emission of two types of light in a small-aperture system with a single objective and sensor. It uses a single chip to simultaneously receive visible light and fluorescence. This time-division multiplexing method for visible light and fluorescence imaging is currently used by most manufacturers. However, this technology only differentiates in the time dimension, causing the system's frame rate to drop to half its original value when doctors observe the fused visible light and fluorescence mode, resulting in a significant "stuttering" effect and unnecessary image blurring. US patent application US20190265490A1 discloses an imaging scheme using one objective and two sensors, achieving high-frame-rate dual-mode imaging through light splitting with a prism or pentaprism. However, it does not consider the impact of the prism structure on volume. For example, if the angle between the prism's reflecting surface and the optical axis is too large, the angle between the reflected light and the incident light increases, leading to an increase in the prism aperture. The beam splitter is placed between the objective lens and the sensor. Therefore, when designing the optical system, the objective lens needs to have a large back focal length to reserve space for the beam splitter, and it also needs to reduce chromatic aberration caused by the dual-mode wideband. The Chinese invention patent application publication number CN111443457A discloses an endoscope that, through the design of cemented lenses and aperture stops, effectively corrects aberrations and chromatic aberrations, improving image clarity. However, it does not take into account the axial resolution of the endoscope, has a low F-number, and does not leave enough space to place the beam splitter. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an optical module for a dual-mode stereo endoscope that is small in size and has a large depth of field and high definition.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: an optical module of a dual-mode stereo endoscope, wherein the optical module is composed of two sets of optical sub-modules with identical structures and opposite light emission surfaces arranged symmetrically. The optical sub-modules include a lens module, a prism module and a sensor module in sequence along the optical axis. The optical axis of the lens module is perpendicular to the optical axis of the sensor module. The lens module is used for light imaging. The focal length (EFL) of the lens module satisfies: 1.5mm < EFL < 2.5mm, and the back focal length (BFL) satisfies: 3.3mm ≤ BFL ≤ 4.3mm. The prism module is used to deflect and split the light imaged by the lens module to generate two parallel modes of outgoing light. The sensor module consists of a first sensor and a second sensor. The first sensor and the second sensor are used to receive light of different modes respectively.

[0007] Compared with the prior art, the advantages of this invention are that it uses two sets of optical sub-modules to achieve 3D imaging and provide stereo vision; it uses a prism module to split and deflect beams of different wavelengths or different polarizations to achieve dual-mode imaging function, thereby improving the system frame rate and target imaging accuracy; and by adjusting the performance parameters of the lens module, the structural design of the prism module, and the placement of the sensor, the axial resolution of the endoscope can be improved while maintaining a small size.

[0008] Preferably, the incident half-aperture h1 of the lens module satisfies: 0.8mm ≤ h1 ≤ 1.4mm; the prism module does not include the half-aperture h of the side of the sensor module. 21 Satisfies: 1.0mm≤h 21 ≤1.4mm, the prism module includes half-aperture h on the other side of the sensor module. 22 Satisfies: 1.0mm≤h 22 The image plane half-height (imgH) of the lens module satisfies: 1.2mm < imgH < 1.4mm, the working F-number (F / #) satisfies: 5.9 ≤ F / # ≤ 6.1, and the depth of field (DOF) satisfies: 30mm ≤ DOF ≤ 150mm.

[0009] Preferably, the lens module consists of a front aperture group and a rear aperture group along the optical axis, wherein the focal length f of the front aperture group is... 11 Satisfies: -1.1≤f 11 / EFL≤-0.8, the focal length f of the rear group of the aperture stop 12 Satisfy: 1.4≤f 12 / EFL≤1.6.

[0010] Preferably, the front group of the aperture is composed of a protective glass, a first lens with negative optical power, and a viewing prism, wherein the image side of the first lens is concave.

[0011] Preferably, the rear group of the aperture consists of six lens modules arranged sequentially along the optical axis as a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens. The second lens is a negative lens with a concave image side, the third lens is a biconvex positive lens, the fourth lens has a convex object side, the fifth lens has a convex image side, the sixth lens is a positive lens with a convex image side, and the seventh lens is a negative lens with a convex object side and a concave image side.

[0012] Preferably, the second lens and the third lens constitute a first cemented doublet with positive optical power, the fourth lens and the fifth lens constitute a second cemented doublet with positive optical power, and the sixth lens and the seventh lens constitute a third cemented doublet with positive optical power.

[0013] Preferably, the rear group of the aperture consists of five lens modules arranged sequentially along the optical axis as an eighth lens, a ninth lens, a tenth lens, an eleventh lens, and a twelfth lens. The object-side surface of the eighth lens is convex, the ninth lens is a negative lens with a concave image-side surface, the tenth lens is a biconvex positive lens, the eleventh lens is a positive lens with a convex image-side surface, and the twelfth lens is a negative lens with a convex object-side surface and a concave image-side surface.

[0014] Preferably, the eighth lens, the ninth lens, and the tenth lens constitute a first cemented lens with positive optical power, and the eleventh lens and the twelfth lens constitute a fourth cemented lens with positive optical power.

[0015] Preferably, the rear group of the aperture consists of four lens modules arranged sequentially along the optical axis as the thirteenth lens, the fourteenth lens, the fifteenth lens, and the sixteenth lens. The object-side surface of the thirteenth lens is convex, and the image-side surface is concave. The fourteenth lens is a biconvex positive lens. The fifteenth lens is a positive lens with a convex image-side surface. The sixteenth lens is a negative lens with a convex object-side surface and a concave image-side surface.

[0016] Preferably, the thirteenth and fourteenth lenses constitute a fifth cemented doublet with positive optical power, and the fifteenth and sixteenth lenses constitute a sixth cemented doublet with positive optical power.

[0017] Preferably, the prism module comprises a first prism and a second prism. The first prism is a secondary reflection prism, including a first incident surface, a first reflecting surface, a second reflecting surface, a first exiting surface, and a first side surface. The angle between the first reflecting surface and the second reflecting surface is 45°, and the angle between the first reflecting surface and the light beam incident on the first reflecting surface is 90°-θ1. The second prism is a primary reflection prism, including a second incident surface, a third reflecting surface, a second exiting surface, and a second side surface. The angle between the third reflecting surface and the second incident surface is 45°+θ1, where θ1 satisfies 16°≤θ1≤22°.

[0018] Preferably, in the prism module, the incident light ray in the first prism has a first optical path with a geometric length of d1, a second optical path with a geometric length of d2 after reflection, and a third optical path with a geometric length of d3 after secondary reflection. In the second prism, the incident light ray in the second prism has a fourth optical path with a geometric length of d4, and a fifth optical path with a geometric length of d5 after reflection. The following relationships must be satisfied simultaneously: d2 + d3 = d4 + d5, 1.7 mm ≤ d2 ≤ 2.4 mm.

[0019] Preferably, the optical module is provided with a housing, and the maximum outer diameter D of the housing satisfies: 7.7mm≤D≤12mm. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the optical module of the endoscope according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the structure of the optical sub-module that makes up the optical module in an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the prism module according to an embodiment of the present invention;

[0023] Figure 4 This is a three-dimensional structural diagram of the endoscope according to an embodiment of the present invention;

[0024] Figure 5 This is a three-dimensional structural schematic diagram of an endoscope partially cut apart according to an embodiment of the present invention;

[0025] Figure 6 This is a schematic diagram of the sensor and image plane according to an embodiment of the present invention;

[0026] Figure 7 This is a schematic diagram of the lens module in Example 1 of the present invention;

[0027] Figure 8 This is a graph showing the optical transfer function of the lens module in Example 1 of this embodiment.

[0028] Figure 9 This is a schematic diagram of the lens module in Example 2 of the present invention;

[0029] Figure 10 This is a graph showing the optical transfer function of the lens module in Example 2 of this embodiment.

[0030] Figure 11 This is a schematic diagram of the lens module in Example 3 of the present invention;

[0031] Figure 12 This is a graph showing the optical transfer function of the lens module in Example 3 of this embodiment.

[0032] Figure 13 This is a schematic diagram of the lens module in Example 4 of the present invention;

[0033] Figure 14 This is a graph showing the optical transfer function of the lens module in Example 4 of this embodiment.

[0034] Figure 15 This is a schematic diagram of the lens module in Example 5 of the present invention;

[0035] Figure 16 This is a graph showing the optical transfer function of the lens module in Example 5 of this embodiment.

[0036] Figure 17 This is a schematic diagram of the lens module in Example Six of Embodiment 6 of the present invention;

[0037] Figure 18 This is a graph showing the optical transfer function of the lens module in Example Six of Embodiment 6 of the present invention;

[0038] Figure 19 This is a schematic diagram of the lens module structure of Example 7 of the present invention;

[0039] Figure 20 This is a graph showing the optical transfer function of the lens module in Example 7 of this embodiment.

[0040] Figure 21 This is a schematic diagram of the lens module in Example 8 of the present invention;

[0041] Figure 22 This is an optical transfer function curve of the lens module in Example 8 of the present invention.

[0042] Explanation of the reference numerals in the attached diagram: 100 - Optical sub-module, 1 - Lens module, 11 - Front aperture group, P1 - Protective glass, L1 - First lens, G - Viewing prism, 12 - Rear aperture group, P2 - First filter, L2 - Second lens, L3 - Third lens, L4 - Fourth lens, L5 - Fifth lens, P3 - Second filter, L6 - Sixth lens, L7 - Seventh lens, GL1 - First cemented doublet lens, GL2 - Second cemented doublet lens, GL3 - Third cemented doublet lens, L8 - Eighth lens, L9 - Ninth lens, L10 - Tenth lens, L11 - Eleventh lens, L12 - Twelfth lens, GS1 - First cemented lens, GL4 - Fourth cemented lens, L13 - Thirteenth lens, L14 - Fourteenth lens, L15 - Fifteenth lens, L16 - Sixteenth lens, GL5 - Fifth cemented lens, GL6 - Sixth cemented lens, 2 - Prism module, 21 - First prism, S1 - First incident surface, S4 - First reflecting surface, S2 - Second reflecting surface, S5 - First exiting surface, S3 - First side surface, 22 - Second prism, S7 - Third reflecting surface, S8 - Second exiting surface, S6 - Second side surface, 3 - Sensor module, 31 - First sensor, 32 - Second sensor, IMA - Image plane, H - Housing. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The drawings are for reference and illustration only and do not constitute a limitation on the scope of protection of the present invention.

[0044] Example:

[0045] For ease of illustration, the thickness, size, and shape of the lenses have been slightly exaggerated in the accompanying drawings. The drawings are for illustrative purposes only and are not drawn to scale.

[0046] like Figure 1 As shown, an optical module for a dual-mode stereo endoscope comprises two symmetrically arranged optical sub-modules 100 with identical structures and opposing light-emitting surfaces. Each sub-module includes, along its optical axis, a lens module 1, a prism module 2, and a sensor module 3. The optical axis of the lens module 1 is perpendicular to the optical axis of the sensor module 3. The lens module 1 is used for light imaging. The focal length (EFL) of the lens module 1 satisfies: 1.5mm < EFL < 2.5mm. Controlling the focal length (EFL) within a small range allows the endoscope to have better light-gathering capabilities. The back focal length (BFL) satisfies: 3.3mm ≤ BFL ≤ 4.3mm. Controlling the back focal length (BFL) within a range larger than the focal length (EFL) provides sufficient space for the prism module 2. The incident half-aperture (h1) of the lens module 1 satisfies: 0.8mm ≤ h1 ≤ 1.4mm. The half-aperture (h1) of the prism module 2 excluding the side containing the sensor module 3... 21 Satisfies: 1.0mm≤h 21 ≤1.4mm, prism module 2 includes the half-aperture h on the other side of sensor module 3. 22 Satisfies: 1.0mm≤h 22 The image plane half-height (imgH) of lens module 1 must be ≤1.4mm, satisfying the following conditions: 1.2mm < imgH < 1.4mm; working F-number (F / #) must be 5.9 ≤ F / # ≤ 6.1; and depth of field (DOF) must be 30mm ≤ DOF ≤ 150mm. Controlling the aperture size of each component meets miniaturization requirements while allowing space for other mechanical structures within the optical module besides the optical elements. Controlling the image plane half-height within a certain range allows for the use of sensors; this half-height can be the horizontal, vertical, or diagonal half-height of the sensor's photosensitive surface. Controlling the working F-number (F / #) within a larger range provides a wider depth of field, improving the endoscope's axial resolution and providing doctors with more comprehensive and detailed information about internal human tissues.

[0047] like Figure 2 As shown, the lens module 1 consists of a front aperture group 11 and a rear aperture group 12 along the optical axis. The focal length f of the front aperture group 11 is... 11 Satisfies: -1.1≤f 11 / EFL≤-0.8, focal length f of the rear group 12 of the aperture. 12 Satisfy: 1.4≤f 12 / EFL≤1.6. Prism module 2 is used to deflect and split the light rays imaged by lens module 1, producing two parallel modes of outgoing light rays. Sensor module 3 consists of a first sensor 31 and a second sensor 32, which are used to receive light rays of different modes respectively. This dual-mode imaging scheme can realize two imaging modes in the same device: when the first sensor 31 receives visible light, it realizes the visible light imaging mode, which can be applied to the observation of tissue structures under conventional white light illumination; the second sensor 32 receives fluorescence, realizing the fluorescence imaging mode, which is used to observe and identify specific tissues for fluorescent markers excited by specific wavelengths such as near-infrared light. Of course, the first sensor 31 can also receive fluorescence, and the second sensor 32 can also receive visible light. In addition, any one of the sensors can also be used to receive polarized light, realizing the polarized light imaging mode. By using the polarization characteristics of light, the reflection from metal objects such as medical devices and the scattered light from media such as saline are ignored, providing a clearer image. By acquiring information from different channels, the accuracy of the final imaging is improved. The endoscope operates in the 0.42µm~0.9µm wavelength range, with the 0.82µm~0.9µm range being the near-infrared band. One lens module corresponds to two sensors, allowing each sensor to image the two different beam patterns independently, thus improving the frame rate and obtaining clearer images. Simultaneously, having one lens module corresponding to two sensors also reduces the size of the endoscope.

[0048] The optical axis of lens module 1 is perpendicular to the optical axis of sensor module 3. The light rays are deflected by prism module 2 before reaching sensor module 3. Compared with the conventional solution where the light rays do not deflect and directly reach the sensor, this avoids the phenomenon of the endoscope diameter being too large due to the sensor being too large.

[0049] like Figure 3 As shown, prism module 2 consists of a first prism 21 and a second prism 22. The first prism 21 and the second prism 22 are made of the same material, so they can be regarded as a single prism when the beam splitting function is not used. The first prism 21 and the second prism 22 can be glued together or not.

[0050] The first prism 21 is a secondary reflection prism, also known as a pentagonal prism, comprising a first incident surface S1, a first reflecting surface S4, a second reflecting surface S2, a first exiting surface S5, and a first side surface S3. The angle between the first reflecting surface S4 and the second reflecting surface S2 is 45°, which controls the perpendicularity of the incident and exiting light from the first prism 21. The angle between the first reflecting surface S4 and the light beam incident on it is 90°-θ1. The first reflecting surface S4 is coated with a semi-transparent and semi-reflective film, selectively separating the incident light into reflected and transmitted light according to wavelength. The reflected light can be visible light, and the transmitted light can be near-infrared light or polarized light. The second prism 22 is a primary reflection prism, and its second incident surface is the first reflecting surface S4 of the first prism 21. Therefore, the second prism 22 includes a second incident surface, a third reflecting surface S7, a second exiting surface S8, and a second side surface S6. The angle between the third reflecting surface S7 and the second incident surface is 45° + θ1, where θ1 satisfies 16° ≤ θ1 ≤ 22°. The 45° angle ensures that the light emitted from the first prism 21 and the light emitted from the second prism 22 are parallel. By constraining the angles of the two prisms, the light path is controlled, and in conjunction with the field of view of the entire optical module, the light in each field of view and each wavelength band is not blocked. In prism module 2, the incident light ray has a first optical path length of d1 in the first prism 21, a second optical path length of d2 after reflection, and a third optical path length of d3 after secondary reflection. In the second prism, the incident light ray has a fourth optical path length of d4 and a fifth optical path length of d5 after reflection. These conditions must simultaneously satisfy the following relationships: d2 + d3 = d4 + d5, and 1.7 mm ≤ d2 ≤ 2.4 mm. By constraining the optical path lengths of the beam in the two prisms, the optical path lengths of the imaging rays in both modes are made the same, preventing additional aberrations and meeting the focal length requirements of different imaging rays. Simultaneously, the planes containing the two imaging surfaces are made close, allowing for control of the lens size and reducing the difficulty of assembling and focusing the optical module. By controlling the shape of the prisms to distribute the optical path, the heights of the outgoing rays from the first prism 21 and the second prism 22 are made close, ensuring that the image matches the sensor module 3 and guaranteeing the imaging quality of each field of view.

[0051] from Figure 2 and Figure 3 As can be seen, light is imaged in lens module 1, and then split and deflected in prism module 2, producing two modes of light. The light emitted from the first prism 21 reaches the first sensor 31, and the light emitted from the second prism 22 reaches the second sensor 32. The two modes of emitted light are parallel to each other. The optical axis of lens module 1 is perpendicular to the optical axis of sensor module 3. The first sensor 31 and the second sensor 32 are located on the same side. The first sensor 31 is set on the first emission surface S5, and the second sensor 32 is set on the second emission surface S8.

[0052] like Figure 4 and Figure 5 As shown, the optical module is externally enclosed by a housing H, inside which are two sets of identical and symmetrically arranged systems. The maximum outer diameter D of the housing H satisfies: 7.7mm ≤ D ≤ 12mm. In terms of overall structure, controlling the maximum outer diameter D of the housing H within a small range meets the miniaturization requirement. Within this range, the maximum outer diameter D of the housing H can also be relaxed to satisfy 8.3mm ≤ D ≤ 12mm, which can increase the aperture to increase incident light and improve imaging brightness and clarity.

[0053] like Figure 6 As shown, the outer sides of the first sensor 31 and the second sensor 32 are rectangular, while the inner rectangles are the photosensitive surfaces of the first sensor 31 and the second sensor 32. The circle with radius imgH in the figure is the image plane IMA. In practical use, a rectangular portion of the image plane IMA that fits the photosensitive surface of the sensor is selected as the actual image plane. Based on the usage requirements and the performance characteristics of the endoscope, the half-height imgH of the image plane IMA can be selected as half the diagonal of the photosensitive surface of the sensor.

[0054] The following examples of several lens modules, along with their optical transfer function curves, are provided in conjunction with the accompanying drawings.

[0055] Example 1:

[0056] like Figure 7 As shown, the lens module 1 in Example 1 includes a protective glass P1, a first lens L1, a viewing prism G, a first filter P2, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a second filter P3, a sixth lens L6, and a seventh lens L7.

[0057] The first lens L1 has a negative optical power, a flat object-side surface, and a concave image-side surface.

[0058] The second lens L2 has a negative optical power, a flat object-side surface, and a concave image-side surface.

[0059] The third lens L3 has a positive optical power, and both the object-side and image-side surfaces are convex.

[0060] The fourth lens, L4, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0061] The fifth lens, L5, has a negative optical power, a concave object-side surface, and a convex image-side surface.

[0062] The sixth lens, L6, has a positive optical power, a flat object-side surface, and a convex image-side surface.

[0063] The seventh lens, L7, has a negative optical power, a concave object-side surface, and a convex image-side surface.

[0064] The second lens L2 and the third lens L3 together form a first cemented doublet GL1 with positive optical power.

[0065] The fourth lens L4 and the fifth lens L5 together form a second cemented doublet GL2 with positive optical power.

[0066] The sixth lens L6 and the seventh lens L7 together form the third cemented doublet GL3 with positive optical power.

[0067] The main optical structural parameters of Example 1 are shown in Table 1.

[0068] Table 1

[0069]

[0070] Example 1 has a focal length of 1.79mm, a back focal length of 3.36mm, and a working F-number of 6.06, providing sufficient back focal length and axial resolution.

[0071] Figure 8 The optical transfer function curve shown illustrates the imaging performance of Example 1. At 100 lp / mm, the MTF of the central field of view with an image height of 0.0 mm and the edge field of view with an image height of 1.3 mm are greater than 0.4, indicating good imaging sharpness.

[0072] Example 2:

[0073] like Figure 9 As shown, the lens module 1 in Example 2 includes a protective glass P1, a first lens L1, a viewing prism G, a first filter P2, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a second filter P3, a sixth lens L6, and a seventh lens L7.

[0074] The first lens L1 has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0075] The second lens L2 has a negative optical power, a flat object-side surface, and a concave image-side surface.

[0076] The third lens L3 has a positive optical power, and both the object-side and image-side surfaces are convex.

[0077] The fourth lens, L4, has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0078] The fifth lens, L5, has a positive optical power, and both its object-side and image-side surfaces are convex.

[0079] The sixth lens, L6, has a positive optical power, and both its object-side and image-side surfaces are convex.

[0080] The seventh lens, L7, has a negative optical power, a concave object-side surface, and a convex image-side surface.

[0081] The second lens L2 and the third lens L3 together form a first cemented doublet GL1 with positive optical power.

[0082] The fourth lens L4 and the fifth lens L5 together form a second cemented doublet GL2 with positive optical power.

[0083] The sixth lens L6 and the seventh lens L7 together form the third cemented doublet GL3 with positive optical power.

[0084] The main optical structural parameters of Example 2 are shown in Table 2.

[0085] Table 2

[0086]

[0087] Example 2 has a focal length of 1.74mm, a back focal length of 4.16mm, and a working F-number of 6.03, providing sufficient back focal length and axial resolution.

[0088] Figure 10 The optical transfer function curve shown illustrates the imaging performance of Example 2. At 100 lp / mm, the MTF of the central field of view with an image height of 0.0 mm and the edge field of view with an image height of 1.3 mm are greater than 0.4, indicating good imaging sharpness.

[0089] Compared to Example 1, Example 2 mainly reverses the structure of the fourth lens L4 and the fifth lens L5, changing the sign of their optical power, thus expanding the possibilities of optical system structure while maintaining good imaging performance.

[0090] Example 3:

[0091] like Figure 11 As shown, the lens module 1 of Example 3 includes a protective glass P1, a first lens L1, a viewing prism G, a first filter P2, an eighth lens L8, a ninth lens L9, a tenth lens L10, a second filter P3, an eleventh lens L11, and a twelfth lens L12.

[0092] The first lens L1 has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0093] The eighth lens, L8, has a positive optical power, and both its object-side and image-side surfaces are convex.

[0094] The ninth lens, L9, has a negative optical power, and both its object-side and image-side surfaces are concave.

[0095] The tenth lens, L10, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0096] The eleventh lens, L11, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0097] The twelfth lens, L12, has a negative optical power, a concave object-side surface, and a convex image-side surface.

[0098] The eighth lens L8, the ninth lens L9, and the tenth lens L10 constitute the first cemented lens GS1 with positive optical power.

[0099] The eleventh lens L11 and the twelfth lens L12 constitute the fourth cemented doublet GL4 with positive optical power.

[0100] The main optical structural parameters of Example 3 are shown in Table 3.

[0101] Table 3

[0102]

[0103] Example 3 has a focal length of 1.75mm, a back focal length of 4.16mm, and a working F-number of 6.03, providing sufficient back focal length and axial resolution.

[0104] Figure 12 The optical transfer function curve shown illustrates the imaging performance of Example 3. At 100 lp / mm, the MTF of the central field of view with an image height of 0.0 mm and the edge field of view with an image height of 1.3 mm are greater than 0.4, indicating good imaging sharpness.

[0105] Compared to Example 1, Example 3 mainly eliminates the second lens L2 and cements the eighth lens L8 together with the ninth lens L9 and the tenth lens L10, thus reducing the number of lenses while maintaining good imaging performance.

[0106] Example 4:

[0107] like Figure 13 As shown, the lens module 1 in Example 4 includes a protective glass P1, a first lens L1, a viewing prism G, a first filter P2, an eighth lens L8, a ninth lens L9, a tenth lens L10, a second filter P3, an eleventh lens L11, and a twelfth lens L12.

[0108] The first lens L1 has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0109] The eighth lens, L8, has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0110] The ninth lens, L9, has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0111] The tenth lens, L10, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0112] The eleventh lens, L11, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0113] The twelfth lens, L12, has a negative optical power, a concave object-side surface, and a convex image-side surface.

[0114] The eighth lens L8, the ninth lens L9, and the tenth lens L10 constitute the first cemented lens GS1 with positive optical power.

[0115] The eleventh lens L11 and the twelfth lens L12 constitute the fourth cemented doublet GL4 with positive optical power.

[0116] The main optical structural parameters of Example 4 are shown in Table 4.

[0117] Table 4

[0118]

[0119] Example 4 has a focal length of 1.78mm, a back focal length of 4.14mm, and a working F-number of 6.05, providing sufficient back focal length and axial resolution.

[0120] Figure 14 The optical transfer function curve shown illustrates the imaging performance of Example 4. At 100 lp / mm, the MTF of the central field of view with an image height of 0.0 mm and the edge field of view with an image height of 1.3 mm are greater than 0.4, indicating good imaging sharpness.

[0121] Compared to Example 3, Example 4 mainly changed the structure of the cemented triplet lens, which maintained good imaging performance while expanding the possibilities of optical system structure.

[0122] Example 5:

[0123] like Figure 15 As shown, the lens module 1 in Example 5 includes a protective glass P1, a first lens L1, a viewing prism G, a first filter P2, a thirteenth lens L13, a fourteenth lens L14, a second filter P3, a fifteenth lens L15, and a sixteenth lens L16.

[0124] The first lens L1 has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0125] The thirteenth lens, L13, has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0126] The fourteenth lens, L14, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0127] The fifteenth lens, L15, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0128] The sixteenth lens, L16, has a negative optical power, a concave object-side surface, and a convex image-side surface.

[0129] The thirteenth lens L13 and the fourteenth lens L14 together form the fifth cemented doublet GL5, which has positive optical power.

[0130] The fifteenth lens L15 and the sixteenth lens L16 together form the sixth cemented doublet GL6 with positive optical power.

[0131] The main optical structural parameters of Example 5 are shown in Table 5.

[0132] Table 5

[0133]

[0134] Example 5 has a focal length of 1.77mm, a back focal length of 4.15mm, and a working F-number of 6.05, providing sufficient back focal length and axial resolution.

[0135] Figure 16 The optical transfer function curve shown illustrates the imaging performance of Example 5. At 100 lp / mm, the MTF of the central field of view with an image height of 0.0 mm and the edge field of view with an image height of 1.3 mm are greater than 0.4, indicating good imaging sharpness.

[0136] Compared to Example 3, Example 5 mainly eliminates the third lens L3, maintaining good imaging performance while reducing the number of lenses.

[0137] Example 6:

[0138] like Figure 17 As shown, the lens module 1 of Example 6 includes a protective glass P1, a first lens L1, a viewing prism G, a first filter P2, a thirteenth lens L13, a fourteenth lens L14, a second filter P3, a fifteenth lens L15, and a sixteenth lens L16.

[0139] The first lens L1 has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0140] The thirteenth lens, L13, has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0141] The fourteenth lens, L14, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0142] The fifteenth lens, L15, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0143] The sixteenth lens, L16, has a negative optical power, a concave object-side surface, and a convex image-side surface.

[0144] The thirteenth lens L13 and the fourteenth lens L14 together form the fifth cemented doublet GL5, which has positive optical power.

[0145] The fifteenth lens L15 and the sixteenth lens L16 together form the sixth cemented doublet GL6 with positive optical power.

[0146] The main optical structural parameters of Example 6 are shown in Table 6.

[0147] Table 6

[0148]

[0149] Example 6 has a focal length of 1.76mm, a back focal length of 4.15mm, and a working F-number of 6.05, providing sufficient back focal length and axial resolution.

[0150] Figure 18 The optical transfer function curve shown illustrates the imaging performance of Example 6. At 100 lp / mm, the MTF of the central field of view with an image height of 0.0 mm and the edge field of view with an image height of 1.3 mm are greater than 0.4, indicating good imaging sharpness.

[0151] Compared to Example 5, Example 6 has fine-tuned the parameters of each lens while maintaining good imaging performance.

[0152] Example 7:

[0153] like Figure 19 As shown, the lens module 1 of Example 7 includes a protective glass P1, a first lens L1, a viewing prism G, a first filter P2, a thirteenth lens L13, a fourteenth lens L14, a second filter P3, a fifteenth lens L15, and a sixteenth lens L16.

[0154] The first lens L1 has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0155] The thirteenth lens, L13, has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0156] The fourteenth lens, L14, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0157] The fifteenth lens, L15, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0158] The sixteenth lens, L16, has a negative optical power, a concave object-side surface, and a convex image-side surface.

[0159] The thirteenth lens L13 and the fourteenth lens L14 together form the fifth cemented doublet GL5, which has positive optical power.

[0160] The fifteenth lens L15 and the sixteenth lens L16 together form the sixth cemented doublet GL6 with positive optical power.

[0161] The main optical structural parameters of Example 7 are shown in Table 7.

[0162] Table 7

[0163]

[0164] Example 7 has a focal length of 1.77mm, a back focal length of 4.14mm, and a working F-number of 6.06, providing sufficient back focal length and axial resolution.

[0165] Figure 20 The optical transfer function curves shown demonstrate the imaging performance of Example 7. At 100 lp / mm, the MTF of the central field of view with an image height of 0.0 mm is greater than 0.4, and the MTF of the edge field of view with an image height of 1.3 mm is greater than 0.3, indicating good imaging sharpness.

[0166] Compared to Example 5, Example 7 has slightly adjusted the parameters of each lens, resulting in a slight decrease in imaging performance.

[0167] Example 8:

[0168] like Figure 21 As shown, the lens module 1 of Example 8 includes a protective glass P1, a first lens L1, a viewing prism G, a first filter P2, a thirteenth lens L13, a fourteenth lens L14, a second filter P3, a fifteenth lens L15, and a sixteenth lens L16.

[0169] The first lens L1 has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0170] The thirteenth lens, L13, has a negative optical power, a convex object-side surface, and a concave image-side surface.

[0171] The fourteenth lens, L14, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0172] The fifteenth lens, L15, has a positive optical power, a convex object-side surface, and a convex image-side surface.

[0173] The sixteenth lens, L16, has a negative optical power, a concave object-side surface, and a convex image-side surface.

[0174] The thirteenth lens L13 and the fourteenth lens L14 together form the fifth cemented doublet GL5, which has positive optical power.

[0175] The fifteenth lens L15 and the sixteenth lens L16 together form the sixth cemented doublet GL6 with positive optical power.

[0176] The main optical structural parameters of Example 8 are shown in Table 8.

[0177] Table 8

[0178]

[0179] Example 8 has a focal length of 1.78mm, a back focal length of 4.15mm, and a working F-number of 6.04, providing sufficient back focal length and axial resolution.

[0180] Figure 22 The optical transfer function curves shown demonstrate the imaging performance of Example 8. At 100 lp / mm, the MTF of the central field of view with an image height of 0.0 mm is greater than 0.4, and the MTF of the edge field of view with an image height of 1.3 mm is greater than 0.3, indicating good imaging sharpness.

[0181] Compared to Example 5, Example 8 has slightly adjusted the parameters of each lens, resulting in a slight decrease in imaging performance.

[0182] In the above example, the protective glass P1, placed at the front of the lens module, serves a protective function. A first filter P2 can be placed at the aperture stop to filter out light outside the operating wavelength range. A second filter P3 is placed in the rear group 12 of the aperture stop to increase the cutoff depth and improve image quality. The flat and near-flat curved surfaces in the lens module 1 and prism module 2 can also be coated with filter films.

[0183] The first lens L1 is made of Nd... L1 Satisfying: 1.7 < Nd L1 <1.9, selecting high refractive index materials to effectively collect light can reduce aberrations.

[0184] The first cemented doublet lens GL1 has a positive optical power and a focal length f. GL1 Satisfy: 3 < f GL1 / EFL < 5 indicates a larger focal length, causing the light to gradually converge and reducing lens sensitivity.

[0185] Other cemented doublet or triplet lenses use cementation to balance chromatic aberration during the propagation of broadband light, thereby correcting on-axis and off-axis chromatic aberrations and reducing lens sensitivity.

[0186] The lenses in the examples above can be either spherical or aspherical.

[0187] The examples shown above are merely individual examples of the present invention and do not limit the scope of protection of the present invention. Therefore, equivalent changes made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. An optical module of a dual-mode stereoscopic endoscope, characterized by comprising: The optical module is composed of two groups of optical sub-modules which are symmetrically arranged, have the same structure and opposite light exit surfaces, sequentially include a lens module, a prism module and a sensor module along an optical axis, the optical axis of the lens module is perpendicular to the optical axis of the sensor module, the lens module is used for light imaging, the focal length EFL of the lens module satisfies 1.5mmEFL<2.5mm, and the back focal length BFL satisfies 3.3mm≤BFL≤4.3mm, the prism module is used for deflecting and splitting the light imaged by the lens module to generate two modes of parallel exit light, the sensor module is composed of a first sensor and a second sensor, the first sensor and the second sensor are used for receiving different modes of light respectively, the prism module is composed of a first prism and a second prism, the first prism is a two-reflection prism, includes a first incident surface, a first reflection surface, a second reflection surface, a first exit surface and a first side surface, the included angle between the first reflection surface and the second reflection surface is 45°, the included angle between the first reflection surface and the light beam incident to the first reflection surface is 90°-θ1, the second prism is a one-reflection prism, includes a second incident surface, a third reflection surface, a second exit surface and a second side surface, the included angle between the third reflection surface and the second incident surface is 45°+θ1, wherein θ1 satisfies 16°≤θ1≤22°, in the prism module, the geometric length of the first segment of light path of the incident light in the first prism is d1, the geometric length of the second segment of light path after reflection is d2, the geometric length of the third segment of light path after two reflections is d3, the geometric length of the fourth segment of light path of the incident light in the second prism is d4, and the geometric length of the fifth segment of light path after reflection is d5, and the following relationship is simultaneously satisfied: d2+d3=d4+d5, 1.7mm≤d2≤2.4mm.

2. The optical module of a dual mode stereoscopic endoscope according to claim 1, wherein, The incident half aperture h1 of the lens module satisfies: 0.8mm≤h1≤1.4mm; the prism module does not contain the half aperture h 21 of one side of the sensor module satisfies: 1.0mm≤h 21 ≤1.4mm, the prism module contains the half aperture h 22 of the other side of the sensor module satisfies: 1.0mm≤h 22 ≤1.4mm; the image surface half height imgH of the lens module satisfies: 1.2mm<imgH<1.4mm, the working F number F / # satisfies: 5.9≤F / #≤6.1, and the depth of field DOF satisfies: 30mm≤DOF≤150mm.

3. The optical module of a dual mode stereoscopic endoscope according to claim 1, wherein, The lens module is composed of a front diaphragm group and a rear diaphragm group along an optical axis, the focal length f 11 satisfies: -1.1≤f 11 / EFL≤-0.8, the focal length f 12 of the rear diaphragm group satisfies: 1.4≤f 12 / EFL≤1.

6.

4. The optical module of a dual mode stereoscopic endoscope according to claim 3, wherein, The front diaphragm group is composed of a protection glass, a first lens with negative optical power and a view direction prism, and the image side surface of the first lens is a concave surface.

5. The optical module of a dual mode stereoscopic endoscope according to claim 4, wherein, The rear diaphragm group is composed of six lenses which are sequentially arranged along the optical axis as a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens, the second lens is a negative lens with a concave image side surface, the third lens is a double-convex positive lens, the object side surface of the fourth lens is a convex surface, the image side surface of the fifth lens is a convex surface, the sixth lens is a positive lens with a convex image side surface, and the seventh lens is a negative lens with a convex object side surface and a concave image side surface.

6. The optical module of a dual mode stereoscopic endoscope according to claim 5, wherein, The second lens and the third lens constitute a first double cemented lens with positive optical power, the fourth lens and the fifth lens constitute a second double cemented lens with positive optical power, and the sixth lens and the seventh lens constitute a third double cemented lens with positive optical power.

7. The optical module of a dual mode stereoscopic endoscope according to claim 4, wherein, The diaphragm rear group consists of five lenses arranged along the optical axis in order as the eighth lens, the ninth lens, the tenth lens, the eleventh lens and the twelfth lens, the object side surface of the eighth lens is a convex surface, the ninth lens is a negative lens with a concave image side surface, the tenth lens is a biconvex positive lens, the eleventh lens is a positive lens with a convex image side surface, and the twelfth lens is a negative lens with a convex object side surface and a concave image side surface.

8. The optical module of a dual mode stereoscopic endoscope according to claim 7, wherein, The eighth lens, the ninth lens and the tenth lens constitute a first three-cemented lens with positive optical power, and the eleventh lens and the twelfth lens constitute a fourth double-cemented lens with positive optical power.

9. The optical module of a dual mode stereoscopic endoscope according to claim 4, wherein, The diaphragm rear group consists of four lenses arranged along the optical axis in order as the thirteenth lens, the fourteenth lens, the fifteenth lens and the sixteenth lens, the object side surface of the thirteenth lens is a convex surface and the image side surface is a concave surface, the fourteenth lens is a biconvex positive lens, the fifteenth lens is a positive lens with a convex image side surface, and the sixteenth lens is a negative lens with a convex object side surface and a concave image side surface.

10. The optical module of a dual mode stereoscopic endoscope according to claim 9, wherein, The thirteenth lens and the fourteenth lens constitute a fifth double-cemented lens with positive optical power, and the fifteenth lens and the sixteenth lens constitute a sixth double-cemented lens with positive optical power.

11. The optical module of a dual mode stereoscopic endoscope according to claim 1, wherein, The optical module is provided with a shell, and the maximum outer diameter D of the shell satisfies: 7.7mm≤D≤12mm.

Images