Improved optical breadbord unit

Abstract

An optical breadboard features a modular plurality of holes for mounting optical devices in different predefined angular positions without requiring lengthy calibration operations.

Description

[0001] “IMPROVED OPTICAL BREADBORD UNIT”

[0002] DESCRIPTION

[0003] TECHNICAL FIELD

[0004] The present invention refers to the field of optical breadboards used to create one or more optical paths by means of optical devices mounted in use on board the same, and in particular to an optical breadboard comprising a plurality of holes for the positioning of optical devices defining a grid with an improved geometric arrangement of the holes.

[0005] STATE OF THE ART

[0006] The set up of optical devices and paths, i.e., the path of light rays through optical devices, is crucial for the development of numerous experimental and commercial applications, e.g., from advanced metrology devices to the implementation of quantum photonic technologies, to the creation of instruments such as optical and fluorescence microscopes, laser cutting machines, spectrometers for materials analysis, etc. The development and prototyping of one of the solutions described above generally requires the use of optical breadboards, often integrated into optical tables. Specifically, an optical breadboard comprises a flat support base on which a plurality of holes, preferably threaded, are made. These holes are arranged according to a predefined geometric pattern to define a grid of holes within which optomechanical devices are mounted and then oriented, i.e., devices for positioning, maintaining, or manipulating light through their interaction once they have been appropriately mechanically oriented. However, current solutions have numerous disadvantages. For example, they require a dedicated breadboard design based on the application, which requires high development and design costs to create complex optical paths in compact dimensions, as well as being limited to the specific application. As can be seen, these solutions are only feasible in specialized laboratories, while simpler and more compact solutions with commercially available components are available. However, the correct use of the breadboard in conjunction with optomechanical devices often relies on the user's skill in correctly orienting the various optomechanical devices arranged on the breadboard. Therefore, the accuracy of the results obtained is strongly dependent on the user's experience, i.e., once mounted on the breadboard, the optomechanical devices must be oriented relative to each other by manual adjustment by the user.

[0007] Therefore, it is always a pressing need to create simple and compact solutions, such that the results obtained do not depend on the user's skill and / or experience in correctly arranging and orienting the optomechanical devices relative to each other on the breadboard.

[0008] BRIEF DESCRIPTION OF THE INVENTION

[0009] The present invention is intended to meet at least in part the above-mentioned needs, wherein such scope is achieved by means of an optical breadboard and optical device assembly with an optical axis and a mounting interface, wherein the breadboard comprises: a flat face, a plurality of centers arranged in a grid along equidistant rectilinear directions, the corresponding centers having center axes perpendicular to the face and the centers being equidistant along the corresponding rectilinear direction and at least one direction being defined along which the centers are spaced from each other by a minimum distance less than distances between centers along directions other than said at least one direction; a plurality of holes or pins arranged along a circumference lying on the flat face and centered at at least one of said centers; a first hole or pin of said plurality of holes or pins being angularly disposed on the circumference so that the optical axis of the optical device rigidly mounted on the breadboard via the releasable coupling between the mounting interface and the first hole or pin incident on a first center axis of the circumference of the first hole or pin and a second center axis of a further center of said plurality of centers along a first incidence direction incident on the first center axis, wherein a distance between the center and the further center is greater than said minimum distance along said incidence direction and wherein the further center is adjacent to the center of the circumference.

[0010] According to the present invention, it is possible to direct the optical axis of an optical device mounted at a center of the grating so that said optical axis incident on both the closest centers, e.g., in the case of a square grating, the centers disposed at a distance equal to the side of the square, and on the centers disposed along the diagonal of the square module. It should be noted that, once mounted, the optical axis intersects a plurality of centers aligned along an incidence direction parallel to the diagonal of the square module of the grating and passing through the center of the circumference. Therefore, the optical circuit is created by placing a second optical device along this diagonal incidence direction. This allows for great flexibility in building optical circuits on the breadboard that maintain angular mounting precision over time. In fact, the holes or pins on the circumference are made with very tight tolerances so that the optical device, when mounted on the breadboard, maintains a high alignment between its optical axis and the directions along which the centers of the grating are aligned. In particular, the grid is defined by the repetition of a geometric module (e.g., square, rectangular, triangular, etc.) so that bundles of parallel and equidistant directions are identified, each direction of which is rectilinear and has a plurality of centers equidistant longitudinally from each other. Furthermore, the breadboard may comprise both holes and pins, or a combination of the two, along its circumference, and, correspondingly, the mating interface comprises corresponding holes or pins, or a combination of the two, to mate to the breadboard.

[0011] According to a preferred and non-limiting embodiment, said plurality of holes or pins comprises a second hole or pin positioned along the corresponding circumference so that the optical device rigidly mounted on the breadboard via the releasable coupling between the mounting interface and the second hole or pin incident on the first center axis and on a third center axis along a second incidence direction different from the first incidence direction and incident on the first center axis.

[0012] The optical devices that define an optical circuit on the breadboard are mounted via a rigid and releasable coupling, preferably frictional, along a rectilinear mounting direction coinciding with the axes of the pins / holes on the circumference to ensure greater precision and ease of assembly / disassembly.

[0013] According to a non-limiting embodiment, the angle between the first and second incidence directions is different from a right angle, so that the second center axis is not adjacent to the first center axis.

[0014] This increases the flexibility of optical circuit construction because the optical axis is aligned even along oblique directions, which is especially useful for a square or rectangular grid.

[0015] According to a preferred embodiment, the breadboard is a single body, and the relative position between the mounting interface and the optical axis is fixed.

[0016] For example, the mounting interface is made in a single body and, therefore, it is sufficient to mount the optical device on the breadboard to obtain a precise alignment of the optical axis in the desired direction and defined by the holes / pins on the circumference i.e. without the need for any adjustment. The breadboard is preferably modular and the only body is, in fact, the module so as not to place limitations on the size of the desired optical circuit using an adequate number of breadboard modules joined together.

[0017] DESCRIPTION OF THE DRAWINGS

[0018] The construction and functional characteristics of the optical breadboard can be better understood from the detailed description that follows, which refers to the attached figure, which represents a preferred and non-limiting embodiment.

[0019] • Fig. 1 shows a perspective view of an optical breadboard according to a preferred embodiment of the present invention;

[0020] • Figs. 2a-2d show diagrams for calculating the slope of a segment joining a pair of nodes in a lattice;

[0021] • Fig. 3 shows a schematic view of the hole layout on an optical breadboard according to a preferred embodiment of the present invention;

[0022] • Fig. 4 shows a schematic view of an optical device mountable on the breadboard of Fig. 1;

[0023] • Figs. 5a-5b show a schematic view of an optical path created using an optical breadboard according to a preferred embodiment of the present invention; and

[0024] • Figs. 6 and 7 illustrate grids with centers other than square / rectangular; and

[0025] • Fig. 8 illustrates two breadboards according to the invention with different grids coupled together to create a compact optical path.

[0026] DETAILED DESCRIPTION OF THE INVENTION

[0027] According to a preferred embodiment of the present invention, Fig. 1 shows a perspective view of an optical breadboard B comprising a flat face 1 on which a plurality of first holes Fl are made. Specifically, these first holes are made on face 1 according to a predefined geometric arrangement defining a grid, preferably with rows and columns of perpendicular first holes, in which each hole is spaced from the next hole in the same row by a first distance dl, while that hole is spaced from the next hole in the same column by a second distance d2, preferably different from each other so as to define a rectangular grid. Preferably, the first and second distances dl, d2 are equal, and in this case a square grid of pitch d is defined (Fig. 1).

[0028] Based on the grid arrangement of the first holes Fl indicated above, it is possible to apply known elementary geometric considerations to calculate a relative angle between any pair of first holes Fl in the grid. For example, as shown in Fig.2a-d, one can consider a rectangular grid in which each first hole Fl represents a node spaced from an adjacent node by internodal distances dl and d2 on the two principal axes, respectively. Given a node n, defined by each first hole Fl, the grid nodes located at a distance dl or d2 from it are defined as ‘first proximal’. For example, the ‘second proximal’ are those nodes connected to node n by two lattice translations with a step equal to dl or d2, i.e. M dl + K d2, with M+K=2, while the ‘third proximal’ are those nodes connected to node n by three grid translations with a step equal to dl or d2, according to the relation M dl+K d2, with M+K=3, and so on. In general, an N-proximal node is defined as a node spaced by N distinct grid translations with a step dl or d2 on the grid nodes. With these definitions, as shown in Fig.2a-d, it can be demonstrated that the angles in the first quadrant of the vector joining a node to its N-proximal node are given by ‘theta’=arctan(I< d / M d2), where M,K=0,l,2,.„ and K+M=N. The construction procedure of the incident segments is illustrated schematically for N<=3 in Fig.2a-c. Therefore, there is a simple generating function that defines the relative angle between multiple nodes of a square-symmetric grid, i.e. the geometry commonly adopted for the construction of optical breadboards. Therefore, by exploiting this geometric consideration, it is possible to create an optical breadboard B that provides a precise alignment of the optical axis of an optical device along the axes intersecting different nodes of the grid, so that they are used as geometric axes for the construction of optical paths of arbitrary complexity, without therefore having to manually adjust the mutual orientation between the optical devices once mounted on the optical breadboard to create an optical path. It should be noted that these considerations can be generalized to optical grids with periodic symmetry other than the square one, for example with a triangular arrangement, or equilateral hexagonal grids. In particular, a triangular grid can be expressed in terms of a rectangular grid, defined by the primitive vectors al and a2 according to Figure 6. The rectangular grid provides an immediate calculation of the angles between N-proximal nodes. The internodal distances for the square grid to be considered for the calculation are: dl = al / 2 and d2 = a2sin(theta). It should be noted that an N-proximal node for the square grid corresponds to an N'-proximal node for a triangular grid, where N 7^ N' in general. This is due to the fact that there is no unique decomposition of the triangular grid into a rectangular grid.

[0029] A regular hexagonal grid, defined by the primitive vectors bl and b2, can in turn be reduced to a triangular grid with vectors al and a2 having different composition rules and a fixed angle of 120° between the sides of the hexagon (Figure 7). It can therefore be traced back to a rectangular grid with primitive vectors dl=bl / 2 and d2=b2 sin(theta)=b2 sin(60°) = b2 sqrt(3) / 2. The N-proximal nodes in a hexagonal grid differ from the N- proximal nodes of the corresponding triangular grid.

[0030] According to a first aspect of the present invention, Fig. 3 shows a geometric construction of the grid defined by the first holes Fl on the face of the optical breadboard B. Furthermore, for each first hole Fl, this breadboard includes a plurality of second holes F2 made on face 1 and surrounding this first hole Fl.

[0031] In particular, the second holes F2 are arranged at a predefined distance from the corresponding first hole Fl, and more specifically the centers of the second holes lie along a circumference of radius R having its center in the first hole Fl. According to a further aspect of the present invention, the second holes F2 are arranged in pairs diametrically opposed with respect to the center of the circumference of radius R. Preferably, in square grid geometry the radius R of this circumference is equal to the semi-distance between two adjacent first holes Fl, Fl', i.e. representing two 'nearest neighbor' nodes arranged at the internodal distance d. It should also be noted that within the circumference of radius R on which the plurality of second holes F2 lies, a first hole Fl is contained, while another first hole defining the grid on the flat face 1 of the breadboard is located outside this circumference. Furthermore, the center of each second hole F2 is placed on the circumference of radius R so as to lie on a rectilinear trajectory passing through the center of the corresponding first hole Fl and the center of another first hole Fl’, Fl” of the lattice defined on the flat face 1, i.e. outside the circumference of radius R. In this way, the rectilinear trajectory passing between a pair of first holes Fl, Fl” defines a rectilinear segment whose orientation on face 1 of the breadboard B can be easily calculated by knowing the geometry of the lattice and applying the geometric considerations for calculating the angle of the segment joining two N-proximal nodes, as previously described. Consequently, for each first hole Fl it is possible to define the position of the center of each second hole F2 on the circumference of radius R and each first hole Fl is the center of that circumference. With reference to the paragraphs relating to Figures 1 and 2, an Fl center is surrounded by adjacent Fl centers defined as those centers that are either a single grid translation away from the Fl center along a first modular direction of the grid or a second modular direction of the grid, or a single grid translation along the first modular direction of the grid combined with a single grid translation along the second modular direction of the lattice transversal to the first modular direction. The first and second modular directions converge on the considered Fl center and are arranged along those sides of the grid module that in turn converge on the considered Fl center. With reference to the rectangular module of Figures 2a-d and considering all possible angular orientations of the module, the Fl centers adjacent to the Fl center are a total of eight, four of which are arranged in a cross with their center in the considered Fl center and another four arranged at the vertices of a rectangle formed by four modules arranged so as to have the considered Fl center in common. According to a further aspect of the present invention, through the configuration indicated above it is also possible to define on face 1 the angular orientation of each straight segment that joins a pair of second holes F2 opposite each other with respect to the center of the circumference of radius R of the first hole Fl, i.e. the diameter of this circumference. In this way, it is possible to easily calculate the relative angular relationship between a straight segment that joins a pair of second holes F2 opposite each other with respect to the center of the circumference of radius R of a first hole Fl, and a straight segment that joins the center of the first hole Fl and that of another first hole outside the circumference of radius R. Advantageously, this geometric relationship is exploited in use to position on the breadboard B an optical device T comprising an optical element Tl, e.g. optical filters, lenses, magnifying objectives, diffractive gratings, etc., so that the angular orientation of the corresponding optical axis on a plane parallel to face 1 is known once such optical device is fixed on the breadboard. In particular, in use such optical devices are rigidly fixed to a pair of second holes F2 diametrically opposed with respect to the center of the circumference of radius R. For example, as shown in Fig. 4, such optical devices may comprise an elongated base T2 configured to be rigidly fixed in use to a pair of second holes F2 opposite with respect to the center of the circumference of radius R. Preferably, such elongated base has a pair of through holes T3 spaced at a distance equal to that of the straight segment joining the pair of holes F2, i.e. the diameter of the circumference of radius R, so that the elongated base can be fixed on the breadboard, e.g., by screws or pins. Furthermore, the optical element Tl is mounted on the base T2 so that its optical axis originates at a midpoint along the segment joining the centers of the pair of holes T3. In this way, when the optical device T is rigidly fixed on the optical breadboard B to a generic pair of second holes F2 diametrically opposed to a corresponding first hole Fl, the optical axis of the optical element Tl lies on a plane parallel to the face 1, from the center of such first hole Fl in a manner parallel to the straight segment joining the center of the hole Fl and another first hole Fl" outside this circumference. The hole Fl" intercepted by the optical axis in turn defines the center of a further circumference R" along which another plurality of second holes F2" (not shown in Fig. 3) are formed, configured to house a second optical device T" to define, in use together with the first optical device T, an optical measurement path (Fig. 5a-b) .

[0032] Therefore, based on the above, depending on the mounting position of the first optical device T in any pair of holes F2 selected by a user, it is possible to know, once such a device is in place, the angular orientation of the corresponding optical axis on face 1, i.e., therefore, in use, the direction of propagation of the light, e.g., reflected or transmitted by such a device. Furthermore, knowing the angular orientation of the optical axis once the relevant optical device is fixed on a pair of second holes F2 as previously described, it is consequently possible to know the node or nodes of the breadboard lattice that are intercepted in use by the optical axis of the optical device T, i.e. the first hole or holes Fl” around each of which a plurality of second holes F2” is made as previously described. In this way, by exploiting a pair of second F2" holes made on the circumference of radius R" having its center in a first Fl" hole intercepted by the optical axis of the first device T, it is possible to mount a second optical device T" in a desired orientation, which receives the light propagating parallel to the optical axis from the first optical device T. Similarly, depending on the mounting position of the second optical device T" in any pair of F2" holes selected by a user, it is possible to know, once this device is in place, the angular orientation of the corresponding optical axis on face 1.

[0033] Advantageously, through the construction configuration of this optical breadboard described above, it is possible to define an optical measurement path by mounting a plurality of optical devices T, T" on the optical breadboard, appropriately selecting the desired mounting position of each in the respective second F2, F2" holes of the corresponding first Fl, Fl" holes of the grating without having to make further manual angular adjustments of these devices once fixed on the breadboard.

[0034] The availability of an angle-generating function for N-proximal nodes, where N is an arbitrary integer, allows the creation of networks of arbitrary complexity. The only substantial limitation to the creation of such breadboards is the size of the mounting holes, i.e., the second F2 holes. This must, as a first approximation, be smaller than the arc of a circle joining two adjacent first Fl holes. In other words, the required angular resolution increases with order N and is therefore limited by the physical dimensions of the F2 mounting holes, which allow for adequate system rigidity. However, it is possible to increase the intranodal distance d, at the cost of a limited miniaturization of the optical breadboard.

[0035] Preferably, in order to achieve the creation of alignment holes on high-density breadboards (for orders N > 2) in miniaturized devices, it is possible to arrange a subset of the threaded alignment holes on a second circle centered on the same node of the breadboard. It is in fact possible to define a radius r different from d / 2 (Fig. 6e). In this case, it is possible to use two different types of optical devices T, differing only in the distance between the through holes T3 made on the base T2. This distance will be equal to the diameter of the internal or external circumference, respectively.

[0036] According to a preferred embodiment, a method for making a breadboard is also provided, comprising the following steps:

[0037] - Receiving data representative of the relative position between the optical axis (O) and the mounting interface

[0038] - Receiving data representative of the desired incidence directions for each center or node Fl of the breadboard lattice - Making a breadboard according to Figure 1 in which the holes F2 of the circumference C of each center or node Fl are arranged angularly so that, when the optical device T is mounted on the breadboard on the circumference C, the optical axis O is aligned with the desired incidence directions.

[0039] According to one aspect of the invention, the breadboard is a component of a traditional optical table with an orthogonal lattice, and the breadboard has a lattice different from that of the optical table, e.g., with more closely spaced nodes or a lattice with a different module, e.g., triangular, rhomboid, etc. to obtain, through the angular positions obtainable on the breadboard of the invention, complex and particularly compact optical paths (figure 8). Preferably, the input optical path has an input direction and an output direction orthogonal or parallel to the input direction and in the breadboard, the optical devices T are oriented so as to direct the optical path by deflection in an oblique direction with respect to the orthogonal square grating of angles other than the right angle along the symmetry axes of the grating that intercept the vertices of the grating i.e. along directions parallel to the symmetry axes of order greater than 1. This approach is also applicable e.g. to rectangular gratings with holes or pins arranged at the vertices of a regular hexagon as can be deduced from figure 5a. For example, in the case of a square grating, the deflection of the obtainable optical path is along a diagonal of the module formed by two adjacent squares.

Claims

CLAIMS1. Optical breadboard assembly (B) and optical device (T) with an optical axis (O) and a mounting interface, wherein the breadboard comprises:- A flat face (1),- A plurality of centers or nodes (Fl) arranged in a grid along equidistant rectilinear directions, the centers (Fl) having corresponding center axes (AF1) perpendicular to the face and the centers being equidistant along the corresponding rectilinear direction and at least one direction being defined along which the centers are spaced apart from each other by a minimum intemodal distance (dl) between the centers (Fl), which distance is smaller than distances between the centers along directions other than said at least one direction,- A plurality of holes or pins arranged along a circumference (C) lying on the flat face (1) and centered in at least one of said centers, a first hole or pin (F2) of said plurality of holes or pins being angularly arranged on the circumference (C) so that the optical axis (O) of the optical device (T) rigidly mounted on the breadboard (B) via a releasable coupling between the mounting interface and the first hole or pin (F2) intersects on a first center axis (AF1) of the circumference (C) of the first hole or pin and a second center axis (AF1) of a further center (Fl) of the said plurality of centers along a first incidence direction incident on the first center axis (AF1), wherein a distance between the center and the further center is greater than said minimum distance (dl) along the said incidence direction and wherein the further center is adjacent to the center of the circumference, wherein said plurality of holes or pins comprises a second hole or pin positioned along the corresponding circumference (C) so that the optical device (T) rigidly mounted on the breadboard (B) via the releasable coupling between the mounting interface and the second holeor pin (F2) intersects on the first center axis and on a third center axis (AF1) along a second incidence direction different from the first incidence direction and incident on the first center axis (AF1) and wherein an angle between the first and second incidence directions is different from a right angle so that the second center axis (AF1) is not adjacent to the first center axis (AF1).

2. An optical assembly according to any of the preceding claims wherein a radius of the circumference (C) is less than said minimum distance (dl).

3. An optical assembly according to any of the preceding claims, wherein the grid of centers (Fl) is square or rectangular or rhomboidal or triangular or hexagonal.

4. An optical assembly according to any of the preceding claims, wherein the centers (Fl) are additional holes adapted to engage in use with the mounting interface of the optical device (T).

5. An optical assembly according to any of the preceding claims, wherein, for each of said incidence directions, on the circumference (C) there is a pair of holes or pins and the mounting interface comprises a pair of corresponding pins or holes to achieve the rigid and releasable mounting between the optical device (T) and the breadboard.

6. An optical assembly according to any of the preceding claims, wherein the circumferences (C) of two adjacent centers (Fl) are tangent.

7. An optical assembly according to any of the preceding claims, wherein the breadboard is a single body and a relative position between the mounting interface and the optical axis is constant.

8. Optical assembly according to any of the preceding claims, wherein the optical device (T) is a reflector device and is arranged such that an optical path is deflectedby an angle other than a right angle and, when a first branch of the optical path entering the optical device (T) is parallel to one of the equally spaced rectilinear directions, a second branch of the optical path exiting the optical device (T) is parallel to an axis of diagonal symmetry or of order higher than 1 of a module of the modular lattice.

9. Assembly according to any of the preceding claims, wherein each center or node of said plurality of centers or nodes (Fl) is surrounded by two concentric circumferences (C) in which the larger circumference has a diameter less than or equal to said minimum distance and in which, along each of the circumferences (C), corresponding first and second pluralities of holes or pins (F2) are arranged angularly so that the optical device (T) can be mounted on the same center axis, in at least six different angular mounting positions and that in at least two of the angular mounting positions, the optical axis (O) is incident on a center or node of said plurality of centers or nodes (Fl) having a distance greater than twice the said minimum distance (dl) from said same center axis.

10. Optical table defining a square grid for mounting optical devices and realizing in use an optical circuit, comprising an optical assembly according to any of claims 1 to 9 and wherein an optical path of the optical circuit is realised in part on said optical assembly11. Optical breadboard (B) for supporting an optical device (T) with an optical axis (O) and a mounting interface, comprising:- A flat face (1),- A plurality of centers (Fl) arranged in a grid along equidistant rectilinear directions, the centers (Fl) having corresponding center axes (AF1) perpendicular to the face and the centers being equidistant along the corresponding rectilinear direction and atleast one direction being defined along which the centers are spaced apart by a minimum distance (dl) smaller than distances between centers along rectilinear directions other than said at least one rectilinear direction,- A plurality of holes or pins arranged along a circumference (C) lying on the flat face (1) and centered in at least one of said centers, a first hole or pin (F2) of said plurality of holes or pins being angularly arranged on the circumference (C) so that, in use, the optical axis (O) of the optical device (T) adapted to be rigidly mounted on the breadboard (B) via the releasable coupling between the mounting interface and the first hole or pin (F2) intersects a first center axis (AF1) of the circumference (C) of the first hole or pin and a second center axis (AF1) of a further center (Fl) of the said plurality of centers along a first incidence direction incident on the first center axis (AF1), wherein a distance between the center and the further center is greater than the said minimum distance (dl) along said incidence direction wherein said plurality of holes or pins comprises a second hole or pin positioned along the corresponding circumference (C) such that the optical device (T) rigidly mounted on the breadboard (B) via the releasable coupling between the mounting interface and the second hole or pin (F2) incident on the first center axis and a third center axis (AF1) along a second incidence direction different from the first incidence direction and incident on the first center axis (AF1), and wherein an angle between the first and second incidence directions is different from a right angle so that the second center axis (AF1) is not adjacent to the first center axis (AF1).

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