SUBASSEMBLY, LENS AND LONG AND SLIM OPTICAL IMAGE TRANSMISSION SYSTEM

Description

[0001] The invention relates to a subassembly for an objective, in particular for a long and slender optical image transmission system, for example an endoscope, an objective and an optical image transmission system, as well as methods for producing a subassembly and an objective.

[0002] Long and slender optical image transmission systems, such as endoscopes, are widely used to examine and diagnose intracavitary organs, intraorgan wall surfaces, or other targets by inserting a tubular insert into a body cavity. Endoscopes are also used in industrial applications to inspect the interior of pipes, boilers, machinery, chemical plants, etc.

[0003] Such image transmission systems typically comprise an optical illumination system for emitting illumination light on the distal side of the image transmission system and an eyepiece on the proximal side of the image transmission system, i.e. on the viewer side.

[0004] Such an image transmission system may have a flexible or a rigid tubular housing.

[0005] Simple image transmission systems are implemented with a straight field of view. This means that the axis of the field of view runs in the direction of the mechanical axis of the tubular housing, and the field of view is limited by the shape of the housing and the optics within it. However, many applications require an enlarged field of view.

[0006] In this case, the image transmission system preferably has an angled lens at the distal end, so that the optical axis of the distal opening forms an angle with the longitudinal axis of the image transmission system.

[0007] For an image transmission system with a flexible, tubular housing, the longitudinal axis is understood to be the direction of the elongated housing.

[0008] A prism is usually used to deflect a light beam in the angled lens.

[0009] US Pat. No. 4,138,192 discloses a lens with a compound prism, in which the actual deflection prism is supported by two prisms arranged on either side, cemented together. Such lenses are complex and therefore expensive to manufacture.

[0010] US Pat. No. 4,850,342 shows lenses with individual prisms. In these cases, creating a mechanical connection is complex.

[0011] US Pat. No. 5,519,532 discloses a lens with a single prism made of plastic. Adequate optical imaging quality with precise reflective surfaces is difficult to achieve.

[0012] CN105403992A discloses an objective lens for a hard tube endoscope, comprising a protective window, a plano-concave lens, three cemented prisms, a plano-convex lens, a single lens, double cemented lenses, and a parallel plate, which are cemented together.

[0013] DE3640186A1 shows an objective lens for endoscopes with a lateral objective lens, which consists of an elongated prism with a convex proximal end surface and a distal end, which are connected to each other by cementing after alignment to an optical axis, and form an inseparable unit with an aperture and a negative lens.

[0014] It is the object of the invention to present a subassembly, a lens, an optical image transmission system, and a method for producing a subassembly and a lens, which avoid the disadvantages of the known and in particular allow easy assembly and good handling with precise display properties.

[0015] The problem is solved by the features of the independent claims.

[0016] A subassembly for a lens, particularly for a long and slender optical image transmission system, such as an endoscope, comprises a prism and a diaphragm element. The prism and the diaphragm element are rigidly connected to each other. Preferably, the prism is directly connected to the diaphragm element, with connecting means, such as an optical cement, being provided directly between the prism and the diaphragm element.

[0017] Preferably, the prism is connected to the aperture element via cementation or direct bonding, such as hydrophilic bonding or laser-assisted bonding.

[0018] Cementing involves joining components with polished surfaces, preferably glass components, by bonding the adjacent surfaces together with a thin, optically transparent layer of cement. A UV-curing optical cement with a similar refractive index to the components to be joined is typically used. For good optical performance, the size of the cement gap must be considered and incorporated into the optical design.

[0019] Bonding eliminates the need for optical cement and brings the adjacent optical surfaces together directly. This process allows for even better optical results. However, the optical surfaces must be manufactured with great precision.

[0020] For example, the bonding force can be generated by adhesion (so-called wringing). The bond can be sensitive to temperature fluctuations.

[0021] In direct bonding, hydrophilic or hydrophobic surfaces are brought together under high temperature and high pressure. Adhesion is based on van der Waals interactions. Typically, a very stable bond can be achieved.

[0022] During anodic bonding, an additional electrical voltage is applied.

[0023] In particular, the prism and the aperture element are connected in such a way that the connection cannot be removed without destruction or can only be removed with great effort, whereby the connecting means is destroyed, for example, if an optical putty is removed with solvent.

[0024] The subassembly forms a single component that can be easily mounted in a housing or socket. During assembly, the relative alignment between the prism and the aperture element is maintained. It is sufficient to align one of the components with respect to the socket or housing. Only the aperture element needs to be attached to the socket or housing.

[0025] The attachment can be made to the side surfaces of the aperture element. The subassembly can be designed so that the aperture element has a larger diameter than the prism, perpendicular to the light transmission direction.

[0026] The aperture element has a cuboidal basic shape with a height of typically approximately 0.5 mm to 1.5 mm, for example, 1 mm, a width of typically approximately 0.5 mm to 5 mm, for example, 1 mm, and a length of typically 1 mm to 3 mm, for example, approximately 3 mm. The exit surface of the primate has the same width as the aperture element, but a shorter length.

[0027] When mounted, the aperture element is at least partially in contact with the housing or mount, for example, with the smaller side surfaces of a cuboid. The prism, on the other hand, can stand freely in space and not touch the housing. The mirror surfaces do not necessarily need to be coated, as reflections can occur due to total internal reflection at the prism-air interface.

[0028] The prism, in particular, has a beam entrance surface and a beam exit surface. The beam exit surface preferably lies against the aperture element. The beam entrance surface and a beam exit surface form an angle γ. This angle corresponds to the angle by which an incident beam is to be deflected by the prism.

[0029] The beam entrance surface and / or the beam exit surface can have an area of ​​0.5mm x 0.5mm to 3mm x 3mm, for example about 1mm x 1mm.

[0030] The angle is preferably in a range of 10° to 80°, more preferably between approximately 20° and 45°, for example 22.5°.

[0031] Preferably, the prism has two reflection surfaces at which light entering through the beam entrance surface is reflected.

[0032] As a rule, incident light can be reflected in the prism by total internal reflection.

[0033] By choosing the right type of glass, reflection within the prism can be achieved by total internal reflection.

[0034] The condition θ>θ c must be fulfilled for all incident rays at the interface, where θ c is the critical angle at which the ray just does not exit: θ c = arcsin n 2 n 1 . Here, n2 is the refractive index of the thinner medium (e.g. air) and n1 is the refractive index of the prism glass.

[0035] The deflection angle γ and the above condition thus provide a measure of the necessary refractive index of the prism glass.

[0036] If no glass is available that meets this requirement for a desired deflection angle, the reflective surfaces must be coated with a mirror layer. A dielectric layer is preferred for this purpose. Alternatively, metal layers or a combination of a metal layer and a dielectric layer can also be used.

[0037] With a coating, reflection is possible even at angles where total internal reflection no longer occurs.

[0038] In an advantageous embodiment of the subassembly, the prism and / or the aperture element are made of glass.

[0039] Glass-made components allow the creation of very flat surfaces, especially mirror surfaces, thus enabling high image quality.

[0040] In particular, the prism has polished glass surfaces.

[0041] Mirroring of the reflective surfaces is not absolutely necessary.

[0042] The problem is also solved by a lens, especially for a long and slender optical image transmission system, such as an endoscope. The lens comprises at least one subassembly as described above.

[0043] In particular, the subassembly is mounted in a cylindrical housing such that the exit surface of the prism is arranged perpendicular to the longitudinal axis of the housing.

[0044] In a preferred embodiment of the lens, the lens comprises a, preferably plano-concave, entrance lens and / or at least one imaging lens.

[0045] The subassembly and the lenses are arranged in a common, particularly cylindrical, housing.

[0046] The optical axis of the entrance lens is arranged perpendicular to the entrance surface of the prism.

[0047] The lens therefore has an oblique angle of view because the optical axis of the entrance lens is inclined relative to the longitudinal axis of the housing.

[0048] The optical axis of the imaging lens is preferably arranged perpendicular to the exit surface of the prism. The objective preferably comprises three imaging lenses whose optical axes are aligned with each other.

[0049] A tuning ring can be arranged between the entrance lens and the subassembly in the lens. This tuning ring can be used to compensate for aberrations that can occur, for example, if the reflecting surfaces of the prism are improperly spaced. A light beam passing through the center of the entrance lens will then not hit the center of the imaging lens. A centering error can lead to aberrations.

[0050] By varying the distance between the entrance lens and the subassembly, the centering required for the required image quality can be achieved. The adjustment ring can be used to determine the appropriate distance for optimal centering. Precise centering can also be achieved by moving the entrance lens, even without the adjustment ring.

[0051] The problem is also solved by an image transmission system, for example, an endoscope, with at least one lens as described above. The lens can, in particular, be detachably attached to a system housing. The lens can be replaced, maintained, and / or cleaned.

[0052] An image transmission system can also have a system housing to which two lenses are attached, thus enabling two image transmission channels. With two image transmission channels, for example, three-dimensional images can be realized.

[0053] The image transmission system can be assembled from a modular system that may include several lenses, for example with different viewing angles, which can each be optionally connected to the system housing.

[0054] In a method for manufacturing a subassembly as described above, a prism with a beam entrance surface and a beam exit surface is fixed to a diaphragm element such that the beam exit surface rests against the diaphragm element and covers the diaphragm opening. The fixation is performed such that the prism is firmly connected to the diaphragm element.

[0055] In particular, a connection is created which cannot be removed without destruction or can only be removed with great effort, whereby the connecting means is destroyed, for example, if an optical putty is removed with solvent.

[0056] Advantageously, the prism is cemented to the aperture element. NOA61 (Norland Optical Adhesive 61), for example, can be used as an optical cement.

[0057] A connection can also be created using hydrophilic bonding. Hydrophilic bonding without cement is a mineral joining technique, particularly suitable for glass and transparent crystalline materials. This joining technique guarantees full transparency at the joint, high mechanical and thermal stability, and allows for precise alignment of the interfaces.

[0058] In an advantageous embodiment of the method, an aperture wafer is provided. This preferably has an aperture substrate coated with black chrome. The substrate can be made of glass, for example, D263T thin glass or quartz glass.

[0059] The aperture wafer has at least one aperture, but preferably an arrangement of a plurality of apertures.

[0060] Outside the apertures, the aperture wafer is opaque. The aperture substrate, made of glass, for example, can be coated with black chrome.

[0061] In addition, at least one prism base body with a beam entry surface and a beam exit surface is provided.

[0062] The aperture wafer may have a thickness between 0.5 mm and 1.5 mm, preferably about 0.7 mm.

[0063] The area of ​​the aperture wafer can be between 10mm x 10mm and 100mm x 100mm, preferably about 45mm x 45mm.

[0064] The aperture diameter can be between 0.1 mm and 1 mm, preferably approximately 0.4 mm. The coating preferably has an optical density greater than 3.

[0065] Typically, a prism base body is provided for each aperture or for a series of apertures of the aperture wafer. The prism base body is preferably rod-shaped and in particular has a length of 10 mm to 100 mm, for example, 40 mm.

[0066] The aperture wafer and prism base body are connected, with one prism base body being placed on each aperture or on a series of apertures.

[0067] The putty gap thickness can be controlled with microbeads, thin threads, thin films, coatings, for example vapor deposition, or with a spacing tool.

[0068] The putty gap thickness is between 0.01mm and 0.05mm, for example 0.03mm.

[0069] The aperture wafer is then cut, for example, using a wafer saw, to create one or more individual subassemblies. If necessary, a prism base body covering a series of apertures is also severed during cutting.

[0070] The aperture wafer can be provided with guide lines that facilitate positioning of the prism base body and specify the separation lines for cutting the aperture wafer. Alternatively and / or additionally, markings can be provided that facilitate the positioning of a cutting machine, for example. Guide lines and / or markings can be engraved into the coating or produced lithographically.

[0071] In a method for assembling a lens as described above, a subassembly is provided, preferably in a method as described above, and the subassembly is fixed, in particular glued, into a housing.

[0072] When assembling the lens, an entrance lens can first be attached to the housing, and preferably a tuning ring is positioned between the entrance lens and the subassembly. The tuning ring determines the distance between the entrance lens and the subassembly, minimizing centering errors.

[0073] Alternatively, the subassembly can be attached to the housing first, then an entrance lens can be moved relative to the subassembly until an optimal position is found. The entrance lens is then attached to the housing.

[0074] During the movement, you can check for any centering errors and adjust the entrance lens position for optimal image quality.

[0075] Advantageously, for bonding the subassembly in a housing, adhesive is introduced through an opening in the housing into the space between the subassembly and the housing and the opening is then closed again with the adhesive.

[0076] In an advantageous embodiment of the method, the subassembly is pushed into the housing using an insertion tool. The insertion tool has a mounting head with a mounting recess for receiving the cover element.

[0077] The mounting recess can have the shape of a groove in which a panel element with a cuboid basic shape can be accommodated.

[0078] The insertion tool also features a guide body whose outer diameter corresponds to the inner diameter of the housing, allowing the insertion tool to be inserted into the housing without tilting. The orientation of the subassembly in the housing is therefore determined by the mounting head, or rather the direction of the mounting recess, and very precise positioning can be achieved.

[0079] The insertion tool may have a guide pin that points radially away from the guide body of the insertion tool and indicates the orientation of the subassembly, in particular the prism. Preferably, the guide pin engages a slot provided in the housing when the subassembly is correctly aligned with respect to the housing and the inclination of the entrance lens.

[0080] An insertion tool for inserting a subassembly into a housing in a method for mounting a lens as described above comprises a mounting head with a mounting recess for receiving the subassembly and a guide body whose outer diameter corresponds to the inner diameter of the housing. Preferably, the insertion tool has a guide pin that indicates the orientation of the subassembly and can cooperate with a slot in the housing.

[0081] Preferred embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings. Corresponding elements are provided with corresponding reference numerals.

[0082] It shows Figure 1 shows a subassembly in a side sectional view; Figure 2 shows a lens in a perspective sectional view; Figure 3 shows a schematic representation of a beam path in a lens in a side sectional view; Figure 4 shows a schematic representation of lenses in comparison in a side sectional view; Figures 5a, 5b show subassemblies in a perspective view; Figures 6a-6b show schematic representations of manufacturing steps; Figure 7 shows a lens and an insertion tool in an exploded view.

[0083] Figure 1 shows a subassembly 1 in a side sectional view. The subassembly 1 comprises a prism 2 and a diaphragm element 3, which are firmly connected to each other, preferably by cementing or direct bonding.

[0084] The prism 2 has a beam entrance surface 4 and a beam exit surface 5. The beam exit surface 5 lies against the aperture element 3.

[0085] The beam entry surface 4 and the beam exit surface 5 enclose an angle γ which corresponds to the angle γ between the direction 8 of an incident beam and the direction 9 of an outgoing beam.

[0086] The prism 2 has two reflection surfaces 6, 7. These can be mirror-coated.

[0087] Figure 2 shows a perspective sectional view of a lens 10. The lens 10 comprises a subassembly 1, a plano-concave entrance lens 11, and three imaging lenses 12a, 12b, 12c, which are arranged in a housing 13.

[0088] The concave surface of the entrance lens 11 is not perpendicular to the longitudinal axis 26 of the housing 13, so that the lens 10 is angled.

[0089] Figure 3 shows a schematic representation of a beam path in an objective 10 in a lateral sectional view.

[0090] The beams 27 pass through the plano-concave entrance lens 11, for example, with a field angle of ±35°. The beam is then guided through the prism 2, where total internal reflection occurs at the reflecting surfaces 6, 7, thereby deflecting the beam. The beam then passes through the aperture 15 of the aperture element 3. The beam subsequently passes through three imaging lenses 12a, 12b, and 12c.

[0091] Figure 4 shows a schematic representation of lenses 10 in comparison in a lateral sectional view.

[0092] In the lens 10 in the upper illustration, the entrance lens 11 and the subassembly 1 are arranged relative to one another such that a centrally imaged light beam 28 corresponds to an incoming light beam 29 which has an offset 30 to the central axis 31 of the entrance lens 11.

[0093] A tuning ring 14 of length L is arranged in the lens 10 of the upper illustration.

[0094] If this is replaced by a tuning ring 14 of length Lc, as shown in the lower illustration, the distance between entrance lens 11 and subassembly 1 is changed such that a centrally incoming beam 32 is imaged as a centrally outgoing beam 28.

[0095] Figures 5a, 5b show subassemblies 1 in perspective view. The subassembly consists of a prism 2 and a diaphragm element 3.

[0096] The aperture element 3 has an aperture 15.

[0097] An opaque coating 32 is applied to a diaphragm substrate 17.

[0098] After assembly, the beam exit surface 5 of the prism 2 lies firmly against the aperture element 3 and covers the aperture opening 15.

[0099] Figures 6a-6b show schematic representations of manufacturing steps. First, at least one prism base body 18 is provided according to Figure 6a .

[0100] In addition, an aperture wafer 16 having a plurality of apertures 15 is provided.

[0101] Auxiliary lines 33 and markings 34 are provided on the aperture wafer 16.

[0102] The auxiliary lines help to arrange the prism base bodies 18 on the aperture wafer 16 in such a way that each row of aperture openings 15 is evenly covered by a prism base body 18.

[0103] The prism base bodies 18 are firmly connected to the aperture wafer 16.

[0104] The aperture wafer 16 can then be cut parallel to the rod-shaped prism base bodies 18, with the markings 34 serving as orientation.

[0105] Finally, the prism base bodies are cut together with the aperture wafer 16 in order to produce individual subassemblies 1, as shown in Figure 5b shown.

[0106] Figure 7shows an objective lens 10 and an insertion tool 19 in exploded view.

[0107] The insertion tool 19 has a mounting head 20 with a mounting recess 21 for receiving the panel element 3 and a guide body 22, the outer diameter of which corresponds to the inner diameter of the housing 13, so that the insertion tool 19 with the subassembly can be pushed precisely into the housing 13.

[0108] The insertion tool 19 has a guide pin 24 that points radially away from the guide body 22 of the insertion tool 19. The guide pin 24 can engage in a slot 25 provided in the housing 13 when the subassembly 1 has the correct orientation with respect to the housing 13.

[0109] An entrance lens 11 is attached to the housing 13. A tuning ring 14 is positioned between the entrance lens 11 and subassembly 1.

Claims

1. Subassembly (1) for an objective (10), in particular for a long and slim optical image transmission system, for example an endoscope (100), comprising a prism (2) and an aperture element (3), wherein the prism (2) and the aperture element (3) are firmly connected to each other, preferably by means of a putty or by direct bonding, wherein the aperture element (3) has a larger diameter than the prism (2) transverse to the direction of light transmission, wherein the prism (2) has a beam entry surface (4) and a beam exit surface (5) and the beam exit surface (5) rests against the aperture element (3), wherein the aperture element (3) has a cuboid basic shape with a height, a width and a length, characterized in that the exit surface of the prism (2) has the same width as the width of the aperture element, but a shorter length, wherein the width and length of the beam exit surface extend in the same directions as the width and length of the basic shape.

2. Subassembly (1) according to claim 1, wherein the prism (2) has a beam entry surface (4) and a beam exit surface (5) and the beam exit surface (5) rests against the aperture element (3), and wherein the beam entry surface (4) and the beam exit surface (5) form an angle γ between 10° and 80°.

3. Subassembly (1) according to claim 1, wherein the prism (2) has two reflection surfaces (6, 7) which are uncoated.

4. Subassembly (1) according to claim 1, wherein the prism (2) has two reflective surfaces (6, 7) which are mirror-coated.

5. Subassembly (1) according to one of the preceding claims, wherein the prism (2) and / or the aperture element (3) are made of glass.

6. Objective (10), in particular for a long and slender optical image transmission system, for example an endoscope (100), comprising at least one subassembly (1) according to one of the preceding claims.

7. Objective (10) according to claim 6, wherein the objective (10) comprises a housing (13), a preferably plano-concave entrance objective (11) and / or at least one imaging lens (12a, 12b, 12c), wherein the entrance lens (11) and / or the at least one imaging lens are arranged in the housing (13).

8. Objective (10) according to claim 6 or 7, wherein the objective (10) comprises a tuning ring (14) and the tuning ring (14) is arranged between the entrance lens (11) and the subassembly (1).

9. Image transmission system (100), for example an endoscope, with at least one objective (10) according to one of claims 7-8.