Long-working-distance double telecentric lens and optical system thereof

Abstract

The invention relates to the technical field of machine vision lenses, and discloses a long-working-distance double telecentric lens and an optical system thereof. The optical system is sequentially provided with a front group A with positive focal power, a diaphragm S and a rear group B with positive focal power from an object side to an image side, the front group A and the rear group B are respectively composed of a plurality of lenses, and the optical axes of all the lenses coincide with a preset optical axis; the combined focal length of the front group A is fA, the combined focal length of the rear group B is fB, and fA and fB meet the relational expression of 0.25 lt; fA / fBlt; and 0.7. Compared with a standard object space telecentric lens, the long-working-distance double telecentric lens provided by the invention has the advantages that through reasonable lens combination and focal length matching, the working distance is longer, the imaging effect is better, and the long-working-distance double telecentric lens is suitable for a long-working-distance high-precision detection application scene.

Description

Technical Field

[0001] The present invention relates to the technical field of machine vision lenses, and in particular to a long working distance double telecentric lens and an optical system thereof. Background Art

[0002] In the machine vision precision optical measurement system, the use of ordinary industrial lenses will have the following problems: changes in object distance will cause different magnifications, parallax, large distortion and other problems, making it difficult to meet high detection requirements. Telecentric lenses can reduce or even eliminate the above problems. Within a certain object distance range, the image magnification will not change with the change of object distance. Its principle advantage makes it very suitable for precision measurement and detection fields, such as product measurement and defect detection in semiconductors, 3C electronics, new energy, packaging and printing, intelligent logistics, automobile manufacturing, and medicine.

[0003] Currently, most small-sized telecentric lenses on the market have two standard working distances: 65mm and 110mm. However, the standard working distance can no longer meet some usage scenarios, and a small working distance is prone to interference with other modules (such as lighting sources). Long working distances are conducive to optical path turning and more complex multi-view detection. Therefore, telecentric lens products with longer working distances are urgently needed.

[0004] The above information is presented as background information only to assist with understanding the present disclosure and no determination or admission is made as to whether any of the above may be used as prior art with respect to the present disclosure. Summary of the invention

[0005] The object of the present invention is to provide a long working distance bi-telecentric lens and an optical system thereof, so as to solve or at least partially solve the technical problems existing in the prior art.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides an optical system of a long working distance double telecentric lens, comprising a front group A with positive focal power, an aperture S, and a rear group B with positive focal power arranged in sequence from the object side to the image side; the front group A and the rear group B are respectively composed of a plurality of lenses, and the optical axes of all the lenses coincide with a predetermined optical axis; wherein the combined focal length of the front group A is f A , the combined focal length of the rear group B is f B , f A and f B Satisfies the relationship: 0.25<|f B / f A |<0.7;

[0008] The front group A includes a first lens G1 with positive optical power, a second lens G2 with positive optical power, a third lens G3 with positive optical power, and a fourth lens G4 with negative optical power; the rear group B includes a fifth lens G5 with negative optical power, a sixth lens G6 with positive optical power, and a seventh lens G7 with positive optical power.

[0009] Optionally, the third lens G3 and the fourth lens G4 are cemented together to form a first cemented lens group U1;

[0010] The focal length of the first lens G1 is f G1 , f G1 With f A Satisfies the relationship: 1.4<|f G1 / f A |<1.9;

[0011] The focal length of the second lens G2 is f G2 , f G2 With f A Satisfies the relationship: 0.75<|f G2 / f A |<1.25;

[0012] The focal length of the first cemented lens group U1 is f U1 , f U1 With f A Satisfies the relationship: 0.2<|f U1 / f A |<0.6.

[0013] Optionally, the first lens G1 and the second lens G2 are meniscus lenses, the third lens G3 is a biconvex lens, and the fourth lens G4 is a biconcave lens;

[0014] The center distance between the first lens G1 and the second lens G2 is smaller than the center distance between the second lens G2 and the third lens G3.

[0015] Optionally, the first lens G1 is made of a high-dispersion glass material, and the Abbe number of the first lens G1 is less than or equal to 35; the second lens G2 is made of a low-dispersion glass material, and the Abbe number of the second lens G2 is greater than or equal to 60.

[0016] Optionally, the fifth lens G5 and the sixth lens G6 are cemented together to form a second cemented lens group U2;

[0017] The focal length of the second cemented lens group U2 is f U2 , f U2 With f B Satisfies the relationship: |f B / f U2 |<0.45; the focal length of the seventh lens G7 is f G7, f G7 With f B Satisfies the following relationship: 0.9<|f G7 / f B |<1.7.

[0018] Optionally, the fifth lens G5 is a biconcave lens, and the sixth lens G6 and the seventh lens G7 are both biconvex lenses.

[0019] Optionally, the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, the sixth lens G6 and the seventh lens G7 form a double telecentric structure, and the working distance of the double telecentric structure is greater than 250 mm and the telecentricity is less than 0.1°.

[0020] Optionally, the aperture of the diaphragm S is a circular hole, and the center of the circular hole is on the predetermined optical axis.

[0021] In a second aspect, the present invention provides a long working distance bi-telecentric lens, including an optical system of the long working distance bi-telecentric lens as described above.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The long working distance bi-telecentric lens provided by the present invention has a longer working distance of up to 250 mm or more, and a better bi-telecentric imaging effect, through reasonable lens combination and focal length matching, compared with a standard object space telecentric lens, and can be suitable for application scenarios of high-precision detection over longer distances.

[0024] The present invention has other features and advantages, which will be apparent from or will be described in detail in the accompanying drawings and the following detailed description incorporated herein, which together serve to explain the specific principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a structural schematic diagram of an optical system of a long working distance double telecentric lens provided by an embodiment of the present invention.

[0027] Figure 2The figure is an MTF curve diagram of an optical system of a long working distance bi-telecentric lens provided by an embodiment of the present invention.

[0028] Figure 3 It is a schematic structural diagram of an optical system of another long working distance double telecentric lens provided in an embodiment of the present invention.

[0029] Figure 4 It is an MTF curve diagram of another optical system of a long working distance bi-telecentric lens provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to explain in detail the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0031] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0032] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0033] In the description of this application, the term "and / or" is an expression used to describe the logical relationship between objects, indicating that three relationships may exist, for example, A and / or B, which means: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally indicates that the objects before and after are in an "or" logical relationship.

[0034] In the present application, terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship of quantity, priority or sequence between these entities or operations.

[0035] Without further limitations, in this application, the words "include", "comprises", "has" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those limited elements, but also other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0036] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than", "less than", "exceed" and the like are understood to exclude the number itself; expressions such as "above", "below", "within" and the like are understood to include the number itself. In addition, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups", "multiple times", etc., unless otherwise clearly and specifically limited.

[0037] In the description of the embodiments of the present application, space-related expressions used, such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or position relationship based on the orientation or position relationship shown in the specific embodiments or drawings, and are only for the convenience of describing the specific embodiments of the present application or facilitating the reader's understanding, and do not indicate or imply that the referred device or component must have a specific position, a specific orientation, or be constructed or operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0038] Unless otherwise expressly specified or limited, in the description of the embodiments of the present application, the terms such as "install", "connect", "connect", "fix", "set", etc. used should be understood in a broad sense. For example, the "connection" can be a fixed connection, a detachable connection, or an integrated setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For technicians in the technical field to which the present application belongs, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0039] Embodiment 1:

[0040] See also Figure 1 , Figure 1 It is a structural schematic diagram of an optical system of a long working distance double telecentric lens provided by an embodiment of the present invention.

[0041] like Figure 1 As shown, the optical system includes:

[0042] A front group A with positive optical power, an aperture S, and a rear group B with positive optical power are arranged in sequence from the object side to the image side; the front group A and the rear group B are respectively composed of a plurality of lenses, and the optical axes of all the lenses coincide with the predetermined optical axis;

[0043] The front group A includes a first lens G1 with positive power, a second lens G2 with positive power, a third lens G3 with positive power, and a fourth lens G4 with negative power; the rear group B includes a fifth lens G5 with negative power, a sixth lens G6 with positive power, and a seventh lens G7 with positive power;

[0044] The aperture is arranged between the fourth lens G4 and the fifth lens G5 to form a double telecentric structure of the optical system.

[0045] Furthermore, the combined focal length of the front group A and the rear group B both have positive focal power; specifically, the combined focal length of the front group A is f A , the combined focal length of the rear group B is f B , f A and f B Satisfies the relationship: 0.25<|f B / f A |<0.7;

[0046] The focal length of the first lens G1 is f G1 , f G1 With f A Satisfies the relationship: 1.4<|f G1 / f A |<1.9.

[0047] In this embodiment, the first lens G1 is made of a glass material with a high refractive index and high dispersion. For a telecentric lens, the working distance increases, resulting in an increase in the height at which the light falls on the first lens G1. Selecting a lens material with a high refractive index can reduce the incident angle of the light and reduce the sensitivity to tolerance. Specifically, in this embodiment, the Abbe number of the first lens G1 is less than or equal to 35.

[0048] The focal length of the second lens G2 is f G2 , f G2 With f A Satisfies the relationship: 0.75<|f G2 / f A |<1.25; the second lens G2 is made of a low-dispersion glass material. Specifically, in this embodiment, the Abbe number of the second lens G2 is greater than or equal to 60; the center interval between the first lens G1 and the second lens G2 is smaller than the center interval between the second lens G2 and the third lens G3.

[0049] The third lens G3 and the fourth lens G4 are cemented together to form a first cemented lens group U1;

[0050] The focal length of the first cemented lens group U1 is f U1 , f U1 With f A Satisfies the relationship: 0.2<|f U1 / f A |<0.6.

[0051] In this embodiment, the center interval between the first lens G1 and the second lens G2 is small, and they bear a greater deflection and refraction effect, which is beneficial to reducing the total length of the lens optical system. Since the deflection and refraction power is shared by two lenses, the degree of deflection of light passing through the lens can be alleviated, and aberrations can be effectively reduced. The second lens G2 and the cemented lens group U1 maintain a large center interval, so that light of different wavelengths forms different height differences on the cemented lens group U1, which is beneficial to correcting the spherical aberration of the optical system.

[0052] Furthermore, the fifth lens G5 and the sixth lens G6 are cemented together to form a second cemented lens group U2;

[0053] The focal length of the second cemented lens group U2 is f U2 , f U2 With f B Satisfies the relationship: |f B / f U2 |<0.45;

[0054] The focal length of the seventh lens G7 is f G7 , f G7 With f B Satisfies the following relationship: 0.9<|f G7 / f B |<1.7.

[0055] In this embodiment, the first cemented lens group U1 and the second cemented lens group U2 can correct chromatic aberration and field curvature, and the two cemented surfaces can correct astigmatism; since the first cemented lens group U1 has negative optical focal length, the first lens G1 and the second lens G2 can be equivalent to positive optical focal length lenses, thereby forming a telephoto system structure, which plays an important role in achieving a long working distance.

[0056] Specifically, in this embodiment, the first lens G1 and the second lens G2 are meniscus lenses, the third lens G3 is a biconvex lens, and the fourth lens G4 is a biconcave lens; the fifth lens G5 is a biconcave lens, and the sixth lens G6 and the seventh lens G7 are both biconvex lenses;

[0057] As an optional implementation, the aperture of the aperture S is set as a circular hole, and the center of the circular hole is on the predetermined optical axis. It can be understood that the aperture value of the aperture S needs to be adjusted accordingly according to the specific application scenario.

[0058] In this embodiment, the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, the sixth lens G6 and the seventh lens G7 form a double telecentric structure, and the working distance of the double telecentric structure is greater than 250 mm and the telecentricity is less than 0.1°.

[0059] The following is a specific embodiment given according to the above-mentioned configuration of this embodiment, and the relevant data of its optical system are specifically shown in Table 1:

[0060] Table 1

[0061] surface Radius(mm) Thickness(mm) Refractive Index Abbe number G1 front surface 187.6 8.7 2.0 20 G1 rear surface 1048.3 8.0 G2 front surface 72.8 13.5 1.60 60 G2 rear surface 441.4 33.2 G3 front surface 39.2 10.2 1.70 - G3, G4 glued surface -96.3 13.0 1.85 - G4 rear surface 16.5 28.5 Aperture S ∞ 3.1 G5 front surface -36.1 4.2 1.70 - G5, G6 bonding surface 30.6 6.5 1.60 - G6 rear surface -22.6 44.3 G7 front surface 124.0 8.6 1.85 - G7 rear surface -106.0 59.2 Image plane /

[0062] It should be noted that in Table 1, the “front surface” corresponds to Figure 1 The left side surface of the lens or lens group corresponds to the "back surface" Figure 1 The corresponding lens or lens group on the right side surface; or can be understood as: the object side is Figure 1 On the left, the image side (or image plane) is Figure 1 On the right side, the surface close to the object side is the "front surface", and the surface close to the image side is the "back surface".

[0063] In this example, the focal length of the first lens G1 is f G1 =229mm; the focal length of the second lens G2 is f G2 =143mm; the focal length of the first cemented lens group U1 is f U1 =-42mm; the focal length of the second cemented lens group U2 is f U2 =135mm; the focal length of the seventh lens G7 is f G7 = 68mm; the combined focal length of the front group A is f A =138mm; the combined focal length of the rear group B is f B =52mm;

[0064] Substituting the above values ​​into each relational expression, we obtain:

[0065] |f B / f A |=0.38,|f G1 / f A |=1.66,|f G2 / f A |=1.04,|f U1 / f A |=0.30,|f B / f U2 |=0.39,|f G7 / f B |=1.31;

[0066] Therefore, the relevant relationship of this embodiment is satisfied, namely:

[0067] 0.25<|f B / f A |<0.7,1.4<|f G1 / f A |<1.9, 0.75<|f G2 / f A |<1.25, 0.2<|f U1 / f A |<0.6,|f B / f U2 |<0.45,0.9<|f G7 / f B |<1.7.

[0068] Please continue to refer to Figure 2 , Figure 2 It is a MTF (Modulation Transfer Function) curve of an optical system of a long working distance double telecentric lens provided by an embodiment of the present invention, the highest resolution can reach 250lp / mm, and can match a 3.45μm pixel chip;

[0069] The above lenses form an optical system with a double telecentric structure, with a working distance of 254mm, a magnification of 0.4 times, a telecentricity of less than 0.1°, a maximum imaging surface of Φ18.4mm, and supports 1.1-inch target surface cameras.

[0070] Embodiment 2:

[0071] See also Figure 3 , Figure 3 It is a schematic structural diagram of an optical system of another long working distance double telecentric lens provided in an embodiment of the present invention.

[0072] like Figure 3 As shown, the optical system includes:

[0073] A front group A with positive optical power, an aperture S, and a rear group B with positive optical power are arranged in sequence from the object side to the image side; the front group A and the rear group B are respectively composed of a plurality of lenses, and the optical axes of all the lenses coincide with the predetermined optical axis;

[0074] The front group A includes a first lens G1 with positive power, a second lens G2 with positive power, a third lens G3 with positive power, and a fourth lens G4 with negative power; the rear group B includes a fifth lens G5 with negative power, a sixth lens G6 with positive power, and a seventh lens G7 with positive power;

[0075] The aperture is arranged between the fourth lens G4 and the fifth lens G5 to form a double telecentric structure of the optical system.

[0076] Furthermore, the combined focal length of the front group A and the rear group B both have positive focal power; specifically, the combined focal length of the front group A is f A , the combined focal length of the rear group B is f B , f A and f B Satisfies the relationship: 0.25<|f B / f A |<0.7;

[0077] The focal length of the first lens G1 is f G1 , f G1 With f A Satisfies the relationship: 1.4<|f G1 / f A |<1.9.

[0078] In this embodiment, the first lens G1 is made of a glass material with a high refractive index and high dispersion. For a telecentric lens, the working distance increases, resulting in an increase in the height at which the light falls on the first lens G1. Selecting a lens material with a high refractive index can reduce the incident angle of the light and reduce the sensitivity to tolerance. Specifically, in this embodiment, the Abbe number of the first lens G1 is less than or equal to 35.

[0079] The focal length of the second lens G2 is f G2 , f G2 With f A Satisfies the relationship: 0.75<|f G2 / f A |<1.25; the second lens G2 is made of a low-dispersion glass material. Specifically, in this embodiment, the Abbe number of the second lens G2 is greater than or equal to 60; the center interval between the first lens G1 and the second lens G2 is smaller than the center interval between the second lens G2 and the third lens G3.

[0080] The third lens G3 and the fourth lens G4 are cemented together to form a first cemented lens group U1;

[0081] The focal length of the first cemented lens group U1 is f U1 , f U1 With f A Satisfies the relationship: 0.2<|f U1 / fA |<0.6.

[0082] In this embodiment, the center interval between the first lens G1 and the second lens G2 is small, and they bear a greater deflection and refraction effect, which is beneficial to reducing the total length of the lens optical system. Since the deflection and refraction power is shared by two lenses, the degree of deflection of light passing through the lens can be alleviated, and aberrations can be effectively reduced. The second lens G2 and the cemented lens group U1 maintain a large center interval, so that light of different wavelengths forms different height differences on the cemented lens group U1, which is beneficial to correcting the spherical aberration of the optical system.

[0083] Furthermore, the fifth lens G5 and the sixth lens G6 are cemented together to form a second cemented lens group U2;

[0084] The focal length of the second cemented lens group U2 is f U2 , f U2 With f B Satisfies the relationship: |f B / f U2 |<0.45;

[0085] The focal length of the seventh lens G7 is f G7 , f G7 With f B Satisfies the following relationship: 0.9<|f G7 / f B |<1.7.

[0086] In this embodiment, the first cemented lens group U1 and the second cemented lens group U2 can correct chromatic aberration and field curvature, and the two cemented surfaces can correct astigmatism; since the first cemented lens group U1 has negative optical focal length, the first lens G1 and the second lens G2 can be equivalent to positive optical focal length lenses, thereby forming a telephoto system structure, which plays an important role in achieving a long working distance.

[0087] Specifically, in this embodiment, the first lens G1 and the second lens G2 are meniscus lenses, the third lens G3 is a biconvex lens, and the fourth lens G4 is a biconcave lens; the fifth lens G5 is a biconcave lens, and the sixth lens G6 and the seventh lens G7 are both biconvex lenses;

[0088] As an optional implementation, the aperture of the aperture S is set as a circular hole, and the center of the circular hole is on the predetermined optical axis. It can be understood that the aperture value of the aperture S needs to be adjusted accordingly according to the specific application scenario.

[0089] In this embodiment, the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, the sixth lens G6 and the seventh lens G7 form a double telecentric structure, and the working distance of the double telecentric structure is greater than 250 mm and the telecentricity is less than 0.1°.

[0090] The following is a specific embodiment given according to the above-mentioned configuration of this embodiment, and the relevant data of the optical system are specifically shown in Table 2:

[0091] Table 2

[0092] surface Radius(mm) Thickness(mm) Refractive Index Abbe number G1 front surface 164.5 11.1 1.95 18 G1 rear surface 440.8 1.0 G2 front surface 82.4 13.5 1.50 65 G2 rear surface 7296.9 35.4 G3 front surface 43.8 10.2 1.65 55 G3, G4 glued surface -106.9 12.9 1.80 - G4 rear surface 24.7 42.9 Aperture S ∞ 2.4 G5 front surface -24.7 7.6 1.70 - G5, G6 bonding surface 36.4 6.4 1.58 - G6 rear surface -23.1 56.8 G7 front surface 115.4 5.2 2.0 25 G7 back surface -217.4 70.6 Image plane /

[0093] It should be noted that in Table 1, the “front surface” corresponds to Figure 3 The left side surface of the lens or lens group corresponds to the "back surface" Figure 3 The corresponding lens or lens group on the right side surface; or can be understood as: the object side is Figure 3 On the left, the image side (or image plane) is Figure 1 On the right side, the surface close to the object side is the "front surface", and the surface close to the image side is the "back surface".

[0094] In this example, the focal length of the first lens G1 is f G1 =267mm; the focal length of the second lens G2 is f G2 =166mm; the focal length of the first cemented lens group U1 is f U1 =-77mm; the focal length of the second cemented lens group U2 is f U2 =-1643mm; the focal length of the seventh lens G7 is f G7 =75mm; the combined focal length of the front group A is f A =147mm; the combined focal length of the rear group B is f B =60mm;

[0095] Substituting the above values ​​into each relational expression, we obtain:

[0096] |f B / f A |=0.41,|f G1 / f A |=1.82,|f G2 / f A |=1.13,|f U1 / f A |=0.52,|f B / f U2 |=0.04,|f G7 / f B |=1.25;

[0097] Therefore, the relevant relationship of this embodiment is satisfied, namely:

[0098] 0.25<|f B / f A |<0.7,1.4<|f G1 / fA |<1.9, 0.75<|f G2 / f A |<1.25, 0.1<|f U1 / f A |<0.6,|f B / f U2 |<0.45,0.9<|f G7 / f B |<1.7.

[0099] Please continue to refer to Figure 4 , Figure 4 This is an MTF curve diagram of another optical system of a long working distance double telecentric lens provided by an embodiment of the present invention, with a maximum resolution of up to 150lp / mm, which is relatively high and can match a 3.45μm pixel chip;

[0100] The optical system with a double telecentric structure formed by the above lenses has a working distance of 335 mm, which is longer than that of Example 1; the magnification is 0.41 times, and it is a double telecentric structure with a telecentricity less than 0.1°, a maximum imaging surface of Φ16 mm, and supports 1-inch target surface cameras.

[0101] Embodiment three:

[0102] This embodiment provides a long working distance bi-telecentric lens, comprising an optical system of a long working distance bi-telecentric lens as described in Embodiment 1 or Embodiment 2;

[0103] Since the optical system has been described in detail in the above embodiments, it will not be described in detail in this embodiment.

[0104] In summary, the embodiment of the present invention has a longer working distance and a better double-telecentric imaging effect through reasonable lens combination and focal length matching compared to a standard object-space telecentric lens, and can be applied to application scenarios of high-precision detection over a longer distance.

[0105] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical system of a long working distance double telecentric lens, characterized in that: The lens comprises a front group A with positive focal power, an aperture S and a rear group B with positive focal power, which are arranged in sequence from the object side to the image side; the front group A and the rear group B are respectively composed of a plurality of lenses, and the optical axes of all the lenses coincide with the predetermined optical axis; wherein the combined focal length of the front group A is f A , the combined focal length of the rear group B is f B , f A and f B Satisfies the relationship: 0.25<|f B / f A |<0.7; The front group A includes a first lens G1 with positive optical power, a second lens G2 with positive optical power, a third lens G3 with positive optical power, and a fourth lens G4 with negative optical power; the rear group B includes a fifth lens G5 with negative optical power, a sixth lens G6 with positive optical power, and a seventh lens G7 with positive optical power.

2. The optical system of a long working distance bi-telecentric lens according to claim 1, characterized in that: The third lens G3 and the fourth lens G4 are cemented together to form a first cemented lens group U1; The focal length of the first lens G1 is f G1 , f G1 With f A Satisfies the relationship: 1.4<|f G1 / f A |<1.9; The focal length of the second lens G2 is f G2 , f G2 With f A Satisfies the relationship: 0.75<|f G2 / f A |<1.25; The focal length of the first cemented lens group U1 is f U1 , f U1 With f A Satisfies the relationship: 0.2<|f U1 / f A |<0.

6.

3. The optical system of a long working distance bi-telecentric lens according to claim 2, characterized in that: The first lens G1 and the second lens G2 are meniscus lenses, the third lens G3 is a biconvex lens, and the fourth lens G4 is a biconcave lens; The center distance between the first lens G1 and the second lens G2 is smaller than the center distance between the second lens G2 and the third lens G3.

4. The optical system of a long working distance bi-telecentric lens according to claim 3, characterized in that: The first lens G1 is made of a high-dispersion glass material, and the Abbe number of the first lens G1 is less than or equal to 35; the second lens G2 is made of a low-dispersion glass material, and the Abbe number of the second lens G2 is greater than or equal to 60.

5. The optical system of a long working distance bi-telecentric lens according to claim 2, characterized in that: The fifth lens G5 and the sixth lens G6 are cemented together to form a second cemented lens group U2; The focal length of the second cemented lens group U2 is f U2 , f U2 With f B Satisfies the relationship: |f B / f U2 |<0.45; the focal length of the seventh lens G7 is f G7 , f G7 With f B Satisfies the following relationship: 0.9<|f G7 / f B |<1.

7.

6. The optical system of a long working distance bi-telecentric lens according to claim 5, characterized in that: The fifth lens G5 is a biconcave lens, and the sixth lens G6 and the seventh lens G7 are both biconvex lenses.

7. The optical system of a long working distance bi-telecentric lens according to claim 6, characterized in that: The first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, the sixth lens G6 and the seventh lens G7 form a double telecentric structure, and the working distance of the double telecentric structure is greater than 250 mm and the telecentricity is less than 0.1°.

8. The optical system of a long working distance bi-telecentric lens according to claim 1, characterized in that: The aperture of the diaphragm S is a circular hole, and the center of the circular hole is on the predetermined optical axis.

9. A long working distance bi-telecentric lens, characterized in that: An optical system comprising a long working distance bi-telecentric lens as described in any one of claims 1-8.

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