Telecentric lens integrated with liquid lens

Abstract

The invention relates to a telecentric lens (100; 100a; 100b; 100c) comprising a lens body (20) extending along an optical axis (X). The lens body (20) is provided with a front optical group (2), a rear optical group (5), a stop (4), a sensor plane (6) and a liquid lens (3). The front optical group (2) is configured to receive incoming light rays (R i ) originating from an object (1). The rear optical group (5) is configured to receive light rays (R j ) from the front optical group (2). The stop (4) is arranged between the front optical group (2) and the rear optical group (5). The sensor plane (6) is configured to collect outgoing light rays (R z ) projected by the rear optical group (5). The stop (4) is substantially arranged at a focal point of the front optical group (2). Furthermore, the liquid lens (3) is arranged between the front optical group (2) and the rear optical group (5). The curvature of the liquid lens (3) can be adjusted to translate a focal plane of the object (1) along the optical axis (X).

Description

Technical Field

[0001] This invention relates to a telecentric lens; more specifically, to a telecentric lens with an integrated liquid lens. Background Technology

[0002] Telecentric lenses can be used, for example, to measure the size of objects. In this case, the telecentric lens for the purpose of this invention is configured to capture images in the visible light band (and also close to the infrared band).

[0003] Telecentric lenses are optical systems widely used in the field of artificial vision for non-contact measurement of objects due to their specific property: they collect a cone of light originating from the illuminated object, wherein the axis of the cone, or the principal ray, is parallel to the axis of the optical system itself. In fact, in this way, the size of the image produced by the lens is independent of the distance to the observed object, and it does not exhibit the perspective effects characteristic of other types of optical systems, making measurements more accurate.

[0004] This property, known as telecentricity, is achieved using a lens in which the entrance pupil is optically located at infinity relative to the observed object. To achieve this, the optical elements arranged between the aperture stop (the lens aperture) and the observed object must collectively form a front optical group with a positive focal length, wherein the focal point of this front optical group coincides with the position of the aperture stop. This arrangement of the aperture stop at the focal point of the front optical group is called "object-side telecentricity," and therefore, a telecentric lens can select only those incident rays parallel to the optical axis originating from the object.

[0005] The known prior art is object-side telecentric lens, but such lenses have a limited depth of field (DoF) and therefore only a single focal plane for the object. Summary of the Invention

[0006] The object of this invention is to provide a telecentric lens that can at least partially overcome the aforementioned disadvantages. Specifically, the object of this invention is to provide a telecentric lens that can overcome the limitations caused by the depth of field of the lens, thus enabling it to move between different focal planes.

[0007] This objective is achieved using the telecentric lens according to claim 1. The dependent claims describe preferred embodiments of the invention. Attached Figure Description

[0008] The features and advantages of the telecentric lens according to the present invention will be clearly shown with reference to the accompanying drawings through the following description of preferred embodiments, which are merely illustrative and not restrictive, in which: - Figure 1A perspective view of the telecentric lens according to the present invention is shown; - Figure 2 This is an optical diagram of the telecentric lens according to the present invention in the first embodiment; - Figure 3 This is an optical diagram of the telecentric lens in the second embodiment; - Figure 4 This is an optical diagram of the telecentric lens in the third embodiment; - Figure 5 An optical diagram of the telecentric lens in the fourth embodiment; and - Figures 6a to 6b These are two images of the same object, in which details located on two different focal planes (i.e., on two different focal planes) are focused. Detailed Implementation

[0009] In this design—throughout the design—the telecentric lens according to the invention is indicated by 100; 100a; 100b; 100c in various exemplary embodiments.

[0010] In the following description, common elements of the various embodiments shown in the accompanying drawings are indicated by the same reference numerals.

[0011] According to one aspect of the invention, telecentric lenses 100; 100a; 100b; 100c include a lens body 20 extending along the optical axis X.

[0012] The lens body 20 is equipped with: a front optical group 2, a rear optical group 5, an aperture 4, a sensor plane 6, and a liquid lens 3.

[0013] Therefore, in addition to the lens body 20, the telecentric lens also includes the front optical group 2, the rear optical group 5, the aperture 4, the sensor plane 6, and the liquid lens 3.

[0014] The front optical group 2 is configured to receive incident light rays R originating from object 1 and parallel to the optical axis X. i This incident light R i Passing through the entrance pupil, which is ideally located at infinity.

[0015] The rear optical group 5 is configured to receive light rays R from the front optical group 2. j .

[0016] Aperture 4 is positioned between the front optical group 2 and the rear optical group 5.

[0017] Sensor plane 6 is configured to collect the outgoing light rays R projected by rear optics group 5. z .

[0018] The aperture 4 is basically positioned at the focal point of the front optical group 2.

[0019] A liquid lens 3 is positioned between the front optical group 2 and the rear optical group 5; the curvature of the liquid lens 3 can be adjusted so that the focal plane of object 1 can be translated along the optical axis X. In other words, by changing the optical power of the adaptive lens, the focusing distance of the entire telecentric lens can be adjusted.

[0020] Preferably, the curvature of the liquid lens 3 can be adjusted by applying an electric field.

[0021] In one embodiment, the liquid lens 3 is positioned significantly close to the aperture 4.

[0022] According to the attached Figure 2 , Figure 4 and Figure 5 In the embodiment shown, the liquid lens 3 is arranged between the front optical group 2 and the aperture 4. For example, the liquid lens 3 is located near the aperture 4 at a distance of less than 1 / 3 (preferably less than 1 / 6) of the distance between the front optical group 2 and the aperture 4.

[0023] according to Figure 3 In one embodiment, the liquid lens 3 is arranged between the aperture stop 4 and the rear optical group 5. For example, the liquid lens 3 is located near the aperture stop 4 with a distance of less than 1 / 3 (preferably less than 1 / 6) of the distance between the aperture stop 4 and the rear optical group 5.

[0024] Preferably, the liquid lens 3 is capable of continuously changing its optical power from negative to zero, and even to positive. The incident light ray R originating from the front optical group 2... i By passing through the liquid lens 3, the focusing distance of the entire telecentric lens can be adjusted.

[0025] According to one embodiment, the front optical group 2 is converging, meaning it has positive optical power as a whole. Specifically, this front optical group 2 includes at least one optical element 21, 22.

[0026] For the purposes of this discussion and unless otherwise stated, the term "optical element" means a single lens or a doublet lens.

[0027] The front optical group 2 sends incident light rays R originating from object 1 toward the aperture 4. i And then it is sent toward the rear optical group 5.

[0028] In one embodiment, the front optical group 2 includes a converging lens 21, which is preferably biconvex, plano-convex, or convex-concave, having a convex surface 2' facing the object 1.

[0029] Preferably, the front optical group 2 consists only of refractive converging optical elements 21 and 22.

[0030] According to one embodiment, the front optical group 2 includes a biplex lens 22, which is preferably concave-convex or plano-convex, wherein the convex surface 2'' of the biplex lens is away from the aperture stop 4.

[0031] Preferably, the convex surface 2'' of the doublet lens faces the converging lens 21.

[0032] According to one embodiment, the front optical group 2 consists of a biconvex converging lens 21 and a concave-convex doublet lens 22.

[0033] In this configuration, the doublet lens 22 is defined by the convex surface 2'' and the concave surface 2''' of the doublet lens. The convex surface 2'' faces the converging lens 21, while the concave surface 2''' is close to the aperture stop 4.

[0034] In one embodiment, the front optical group 2 has positive optical power and includes at least two optical elements; preferably, the front optical group 2 includes only two converging optical elements. According to one embodiment, the front optical group 2 includes at least three optical elements—preferably, the front optical group consists of only three optical elements—where two of the three optical elements are converging and the remaining three optical elements are diverging. Specifically, the three optical elements include a first optical element, a second optical element, and a third optical element. The first optical element faces the object 1, i.e., the first optical element receives R directly from the object 1. i The input light beam is a first converging lens. The second optical element can be a second lens or a second doublet lens. Finally, the third optical element, located away from object 1, can be a third lens or a third doublet lens.

[0035] In this embodiment, the front optical group 2 has two to four optical elements (including the number of endpoints). In other words, the front optical group 2 may include a minimum of two optical elements and a maximum of four optical elements.

[0036] Preferably, the front optical group 2 consists of only four optical elements, wherein at least two of the four optical elements are converging, and at least one of the four optical elements is diverging. Specifically, the four optical elements include a first optical element, a second optical element, a third optical element, and a fourth optical element. The first optical element faces the object 1, that is, the first optical element receives R directly from the object 1. i The input light beam is a first converging lens. A second optical element is located behind the first optical element, moving away from object 1 along the optical axis X, and can be a second lens or a second doublet lens. A third optical element is located behind the second optical element, moving away from object 1 along the optical axis X, and can be a third lens or a third doublet lens. Finally, a fourth optical element, moving away from object 1, can be a fourth lens or a fourth doublet lens.

[0037] According to one embodiment, the aperture 4 is substantially positioned at the focal point of the rear optical group 5.

[0038] When the exit pupil is at infinity, that is, when the aperture 4 of a telecentric lens is essentially positioned at the focal point of the rear optical group 5, the lens is telecentric when viewed from the image side. Specifically, the configuration in which the aperture is positioned at the focal point of the rear optical group is "image-side telecentric".

[0039] Furthermore, when both the entrance pupil and the exit pupil are at infinity, the aperture stop 4 is essentially positioned at the focal point of both the front optical group 2 and the rear optical group 5; thus, in this particular configuration, the lens is referred to as having two telecentrics, namely the object-side telecentric and the image-side telecentric.

[0040] The main characteristics of object-side telecentric lenses and double telecentric lenses are: they only receive incident rays R originating from object 1, with the principal ray parallel to the optical axis X. i A beam of light, in this way producing an image whose perspective effect is eliminated.

[0041] Preferably, the telecentric lens for the purpose of this invention is either bitelecentric or object-side telecentric.

[0042] In one embodiment, the aperture 4 is adjustable, meaning its diameter is variable. Alternatively, the aperture 4 is fixed, meaning it is not adjustable.

[0043] According to one embodiment, the rear optical group 5 is converging, meaning it has positive optical power overall. This rear optical group 5 includes at least one lens 51 and / or a positive biplex lens.

[0044] Preferably, the lens 51 is biconvex, plano-convex, or convex-concave.

[0045] According to one embodiment, at least one lens 51 is a single lens; the rear optical group 5 therefore consists of only one lens 51.

[0046] In another embodiment (not shown in the figure), the rear optical group 5 consists of only one positive biplex lens.

[0047] In another embodiment (not shown in the figure), the rear optical group 5 consists of a single lens 51 and a positive doublet lens.

[0048] Ray R originating from front optical group 2 j The light passes through aperture 4 and reaches the rear optical group 5, which then directs the outgoing light beam R. z Focus on sensor plane 6.

[0049] In one embodiment, the rear optical group 5 includes a rear optical element (preferably consisting only of a rear optical element), wherein the rear optical element is a converging lens.

[0050] In one embodiment, the rear optical assembly 5 includes a first rear optical element and a second rear optical element (preferably consisting only of the first and second rear optical elements), the first rear optical element being close to the object 1. At least one of the first and second rear optical elements is converging. Specifically, the first rear optical element may be a first rear lens or a first rear doublet lens. The second rear optical element may be a second rear lens or a second rear doublet lens.

[0051] In an embodiment, the rear optical group 5 includes a first rear optical element, a second rear optical element, and a third rear optical element (preferably composed only of the first, second, and third rear optical elements). The first rear optical element is close to the object 1, the second rear optical element is located behind the first rear optical element and moves away from the object 1 along the optical axis X, and the third rear optical element is away from the object 1. In the rear optical group 5, at least one rear optical element is converging, and at least one rear optical element is diverging. Specifically, the first rear optical element can be a first rear lens or a first rear doublet lens. The second rear optical element can be a second rear lens or a second rear doublet lens. The third rear optical element can be a third rear lens or a third rear doublet lens.

[0052] In this embodiment, the rear optical group 5 includes a first rear optical element, a second rear optical element, a third rear optical element, and a fourth rear optical element (preferably composed only of the first, second, third, and fourth rear optical elements). The first rear optical element is close to the object 1, the second rear optical element is located behind the first rear optical element and moves away from the object 1 along the optical axis X, the third rear optical element is located behind the second rear optical element and moves away from the object 1 along the optical axis X, and the fourth rear optical element is away from the object 1. In the rear optical group 5, at least two rear optical elements are converging, and at least one rear optical element is diverging. Specifically, the first rear optical element can be a first rear lens or a first rear doublet lens. The second rear optical element can be a second rear lens or a second rear doublet lens. The third rear optical element can be a third rear lens or a third rear doublet lens. Finally, the fourth rear optical element can be a fourth rear lens or a fourth rear doublet lens.

[0053] In an embodiment, the rear optics group 5 has two to four rear optical elements (including the number of endpoints). In other words, the rear optics group 5 may include a minimum of two rear optical elements and a maximum of four rear optical elements.

[0054] In the attached Figure 4 and Figure 5In one embodiment shown, the telecentric lenses 100b and 100c include a light source 8 and a beam splitter 7.

[0055] The light source 8 is, for example, an LED source, and is arranged orthogonally to the optical axis X.

[0056] The beam splitter 7, also known as a beam splitter, is configured to receive light from the light source 8 and illuminate the object 1.

[0057] Specifically, the beam splitter 7 is configured to illuminate the object 1 through the front optical group 2 in a manner substantially coaxial with the optical axis X.

[0058] Preferably, the lens body 20 is provided with a side hole through which light emitted by the light source 8 passes. Specifically, this light source 8 is arranged on the outer surface of the lens body 20.

[0059] According to Figure 4 In this embodiment, the beam splitter 7 is arranged between the front optical group 2 and the aperture 4. Preferably, the beam splitter 7 is located approximately at the midpoint between the front optical group 2 and the aperture 4; more preferably, it is located approximately at the midpoint between the doublet lens 22 and the aperture 4.

[0060] According to the attached Figure 5 In the embodiment shown, the front optical group 2 includes a beam splitter 7. In other words, the beam splitter 7 is arranged inside the front optical group 2. Preferably, the beam splitter 7 is arranged between the biconvex converging lens 21 and the concave-convex doublet lens 22. In one embodiment, the front optical group 2 is thus composed of the biconvex converging lens 21, the beam splitter 7, and the concave-convex doublet lens 22, wherein the convex surface 2'' of the doublet lens faces the beam splitter 7, and the concave surface 2''' of the doublet lens is close to the aperture stop 4.

[0061] Attached Figure 6a and Figure 6b This demonstrates the different details of the same object located on two different focal planes (i.e., on two different focusing planes). These different focal planes are achieved solely by adjusting the optical power of the liquid lens 3 integrated into the telecentric lens.

[0062] Innovatively, the telecentric lens of this invention fully achieves its intended purpose.

[0063] Advantageously, by means of a liquid lens, the focal plane of the entire telecentric lens can be altered. In other words, the focal plane can be shifted along the optical axis. Therefore, integrated liquid lenses are particularly useful for overcoming those limitations related to depth of field, in that they enable the shifting of the focal plane.

[0064] According to one advantageous aspect, the object-side telecentric or double telecentric lens itself has extremely low distortion, which, when superimposed on perspective cancellation, makes it particularly suitable for the measurement and inspection of objects. According to another advantageous aspect, as long as the liquid lens is located near the aperture stop, its distortion value has minimal impact. The liquid lens maintaining this extremely low distortion value makes the telecentric lens described in this invention compatible with applications requiring low distortion and good telecentricity.

[0065] Advantageously, when using a liquid lens, it is possible to focus on objects at different working distances. Therefore, by improving the ability to focus on different object planes, the limitations imposed by the depth of field of telecentric lenses can be overcome.

[0066] For embodiments of the telecentric lens according to the present invention, those skilled in the art may adjust, adapt, and replace elements with functionally equivalent elements to meet possible needs without departing from the scope of protection of the appended claims. Each feature described as belonging to the respective embodiments may be obtained independently of the other described embodiments.

Claims

1. A telecentric lens (100; 100a; 100b; 100c), comprising a lens body (20) extending along an optical axis (X), said lens body (20) being provided with: - The front optical group (2) is configured to receive incident light rays (R) originating from the object (1) and parallel to the optical axis (X). i ); - The rear optical group (5) is configured to receive light (R) from the front optical group (2). j ); - An aperture (4) is arranged between the front optical group (2) and the rear optical group (5); - The sensor plane (6) is configured to collect the outgoing light rays (R rays) projected by the rear optical group (5). z ), in, The aperture (4) is substantially arranged at the focal point of the front optical group (2), and the telecentric lens further includes a liquid lens (3) arranged between the front optical group (2) and the rear optical group (5), the curvature of which can be adjusted so that the focal plane of the object (1) can be translated along the optical axis (X).

2. The telecentric lens (100; 100a; 100b; 100c) according to any one of the preceding claims, wherein, The liquid lens (3) is positioned significantly close to the aperture (4).

3. The telecentric lens (100; 100b; 100c) according to any one of the preceding claims, wherein, The liquid lens (3) is arranged between the front optical group (2) and the aperture (4).

4. The telecentric lens (100a) according to claim 1 or 2, wherein, The liquid lens (3) is arranged between the aperture (4) and the rear optical group (5).

5. The telecentric lens (100; 100a; 100b; 100c) according to any one of the preceding claims, wherein, The front optical group (2) is converging and has positive optical power. The front optical group (2) includes at least one optical element (21, 22).

6. The telecentric lens (100; 100a; 100b; 100c) according to any one of the preceding claims, wherein, The front optical group (2) includes a converging lens (21), which is preferably biconvex, plano-convex, or convex-concave, having a convex surface (2') facing the object (1).

7. The telecentric lens (100; 100a; 100b; 100c) according to any one of the preceding claims, wherein, The front optical group (2) includes a biplex lens (22), which is preferably concave-convex or plano-convex, wherein the convex surface (2'') of the biplex lens is away from the aperture stop (4).

8. The telecentric lens (100; 100a; 100b; 100c) according to claims 6 and 7, wherein, The front optical group (2) consists of a biconvex converging lens (21) and a concave-convex doublet lens (22), wherein the convex surface (2'') of the doublet lens faces the converging lens (21), and the concave surface (2''') of the doublet lens is close to the aperture stop (4).

9. The telecentric lens (100; 100a; 100b; 100c) according to any one of the preceding claims, wherein, The aperture (4) is prominently positioned at the focal point of the rear optical group (5).

10. The telecentric lens (100; 100a; 100b; 100c) according to any one of the preceding claims, wherein, The aperture (4) is adjustable.

11. The telecentric lens (100; 100a; 100b; 100c) according to any one of claims 1 to 9, wherein, The aperture (4) is fixed.

12. The telecentric lens (100; 100a; 100b; 100c) according to any one of the preceding claims, wherein, The rear optical group (5) is converging and has positive optical power. The rear optical group (5) includes at least one optical element (51) and / or a positive biplex lens.

13. The telecentric lens (100b) according to any one of the preceding claims; 100c), including: i) A light source (8), such as an LED source, is arranged orthogonally to the optical axis (X); ii) A beam splitter (7) is configured to receive light from the light source (8) and illuminate the object (1).

14. The telecentric lens (100b) according to the preceding claim, wherein, The beam splitter (7) is arranged between the front optical group (2) and the aperture (4), preferably at approximately the midpoint between the front optical group (2) and the aperture (4).

15. The telecentric lens (100c) according to claim 13, wherein, The front optical group (2) includes the beam splitter (7).

Images