ES2549977B2 - Optoelectronic methods and devices for collimating and / or for determining the degree of collimation of a light beam - Google Patents

Abstract

Optolectronic methods and devices for collimating and / or determining the degree of collimation of a light beam. # The invention relates to a method for determining the degree of collimation of a light beam and to a method for collimating a light beam by means of the Calculation of the periods of two self-images, or more, generated by a diffraction network at different distances. # In addition, it includes optoelectronic devices designed to carry out both methods. The different devices comprise a diffraction network (3), one or more photodetection systems (4) and an electronic data processing device (5). When a single photodetection system is included, two or more self-images are obtained by mirrors or by tilting the photodetection system with respect to the optical axis of the device. Devices designed to collimate a beam include a collimator element (2).

Description

Optoelectronic methods and devices for collimating and / or for determining the

degree of collimation of a beam of light.

5 Technical sector

The present invention fits into the Optical Technology sector and more

specifically in the Optoelectronic Devices sector.

State of the art

10 The degree of collimation of a beam of light is of great importance in numerous optical applications, such as metrological devices,

systems for lighting, consumer optics, laser applications, etc. It is said that a light beam is collimated when its degree of

Collimation is maximum. In this situation the light beam propagates in parallel and, in the ideal case, the divergence is minimal. There are methods

simple, well known, to collimate a general light source, by

use of a lens or lens system, such as comparing the beam size

at various distances or the method of self-collimation, where a real object is placed in the focus of a converging lens so that the image is formed in the

20 infinity A flat mirror is then placed behind the lens that reflects the rays of light so that the image of the same size is formed on the object. These easy implementation methods are approximate and in the

most industrial or experimental applications produce excessive

uncertainty.

25 Interferometric techniques to collimate a beam of light or measure its degree of collimation known as LSI ("lateral shearing interferometry")

They are among the most accurate, being known for several decades

[D. Malacara, ed., Optical Shop Testing (Wiley, New York, 1978)]. the basis of

These techniques consist of doubling the wavefront under study,

30 Shift it slightly and get the interference pattern between the original and the displaced wavefront. However, to produce such a pattern the use of light beams that have a high degree of coherence is required

temporal and spatial, as lasers are usually.

In many situations it is necessary to collimate or know the degree of collimation

of a beam of light from other sources such as light-emitting diodes (LEDs, from English "Iight-emil! ing diodes"), laser diodes, surface emission lasers with vertical cavity (VCSELs, from English "vertical- cavity

5 surface-emil! Ing lasers ") and other sources that have a certain degree of temporal and / or spatial partial coherence.

Collimators that use diffraction nets, using the Talbot effect, constitute an attractive and very precise technique for collimating light beams from this type of source. The advantage of using the self-images of the 10 diffraction networks to determine the degree of collimation of a light beam

is that the requirements of the lighting source are less restrictive, because the phenomenon is not due to interference, but to diffraction. Thus, it is not necessary that the source be punctual to produce self-images, nor does it need to be monochromatic.

15 Recently, a technique has been developed to determine the degree of

collimation based on a conjunction of linear and circular diffraction networks, as presented in [K. Patorski, K. Pokorski, and M. Trusiak, "Circular-linear grating Talbot interferometry with moiré Fresnel imaging for beam collimation" Opl. Lel! 39, 291 (2014)]. The drawback of this technique is the remarkable difficulty in processing the signals obtained at the exit of the collimation system. Another example for measuring with low uncertainty the degree of collimation of a beam with a degree of partial coherence is shown in [L.M. Sanchez-Brea, EJ. Torcal-Milla, E J. Salgado Rivet, 1. Morlanes, 1. Jimenez-Castillo, and E. Bernabeu, "Collirnation 25 method using a double grating system" Appl. Opl 49, 3363 (2010)] where two linear diffraction networks are used. However, this technique requires a lateral displacement of the network, so that the device becomes complicated and expensive. Also sources with a high degree of polychromaticity can generate self-images when a diffraction network is used. For example, it is known that polychromatic sources can generate stable self-images over a long distance [N Guérineau, B. Harchaoui, J. Primot "Talbot experiment re-examined: demonstration of an achromatic and continuous self-imaging regime," Optics Communications 180 199-203 (2000)]. On the other hand, the degree of collimation of a beam 35 can be determined by measuring the period of a self-image and the comparison with the period of the diffraction network that forms said self-image [L.M. Sanchez

Brea, EJ. Torcal-Milla, J.M. Herrera-Fernandez, T. Marlanes, and E. Bernabeu

"Self-imaging technique far beam collimation" Optics Lellers 39 (19) 57645767 (2014)]. When the period of the self-image is the same as that of the network, then the beam is collimated. The main disadvantage of this technique is the need to know the period of the network with high precision, of the

Nanometer order in many cases. This means very strict control.

of the environmental conditions and the positioning of the different elements

Optical and opto-electronic. Small temperature variations,

rotations, component misalignments, etc. can produce

variations of the period of the diffraction network used or variations of the

period of the self-images. For this, it is necessary to devise a system that does not need prior knowledge of the diffraction network used.

Diffraction is a characteristic phenomenon of light linked to its wave character where a light beam ceases to follow a rectilinear path,

as indicated by geometric optics, when encountering an obstacle or when

through an opening. The Talbot effect takes place when a wave hits

over a diffraction network. In the near field regime you can find replicas of the object shape known as auto images (of

English "self-images") located in Zk = k p2 / A. where k is an integer, p the

network period and A wavelength of incident field. The distances where the self-images, Zk, are located are called Talbo distances!

Based on the mentioned physical phenomena, various devices that check the degree of collimation of a beam are known in the state of the art. Among the patents related to the invention are:

Patent CN1080997 (A) which shows a device that tests the degree of collimation of a laser light source in a comprehensive computerized form.

It includes a wide range of measurements whenever it is a light source

To be.

Patent CN101469977 (A) showing a device that checks the

collimation increasing accuracy and with a compact structure.

Ultimately, there is a need in the state of the art for a method of determining the degree of collimation of a beam in a robust and simple way, and the need for a method for obtaining a beam with a high degree of collimation. In addition, both methods must be very precise, so they must be invariant against environmental and environmental conditions.

positioning of the different elements of those that state their

respective assemblies. They must also be compatible with different types of

light sources, and not only with beams with a high degree of coherence and

monochromaticity On the other hand, these methods must be independent of the period of the diffraction network.

Detailed description of the invention

Optoelectronic methods and devices for collimating and / or for determining the degree of collimation of a light beam.

The present invention relates to a method of measuring the degree of

collimation of a beam of light and a method to collimate a beam of light with

high precision Both use the Talbol effect produced by diffraction

in a near field regime and the self-images generated by a network of

diffraction to check the degree of collimation and perform collimation.

15 These methods can be applied to beams coming from large and / or polychromatic sources with great independence of the environmental conditions, of the positioning of the opto-mechanical elements and of the period of the diffraction network.

In this specification, "beam of light" means 0, simply,

20 "beam" any type of beam of light, including a laser beam, capable of producing self-images when hitting a diffraction network.

To measure the degree of collimation of a beam, a diffraction network 3 of a period p is used in the present invention. When the light spread, due to

diffractive effects, self-images are generated at certain distances from the

25 diffraction net 3 [K. Palorsky, "The self-imaging phenomenon and its applications," Progress in Optics 27 1-108 (1989)]. If; [is the average wavelength of the light beam, and the diffraction network 3 modulates its amplitude, the

generated self-images are located at whole or half-Talbot Talbot distances Zk = k p2 lA. K being an integer. However, it is possible to find auto images at different distances, although they tend to have a smaller amplitude. In the reference [L.M. Sanchez-Brea, F.J. Torcal-Milla, J.M. Herrera-Fernandez, T. Morlanes, and E. Bernabeu "Self-imaging technique for beam collimation" Optics Letlers 39 (19) 5764-5767 (2014)] describes a technique with which the degree of collimation of a beam of light 35 comparing the period of a diffraction network 3 with the period of a

self image For this, a very precise knowledge of the period is required

of the diffraction network 3 and the period of the self image. In the solution of

article by L.M. Sanchez-Brea et al. of 2014, it is assumed that the period of

diffraction net 3 is known. Diffraction networks can be recorded

5

with very small accuracies, of the order of 1 nanometer, under conditions

very controlled, by, for example, electron beam techniques. Without

However, for the practical realization of a device it is not possible

Keep these conditions so strict. For example, when the

ambient temperature, the period of diffraction network 3 can be seen

10

modified due to expansion of the substrate in which it has been recorded.

It is also required that the mechanical conditions of the device be very

strict, very accurately controlling position tolerances and

rotation of the optical elements of the system. For example, if the diffraction network

3 is slightly rotated with respect to a photodetection system used

IS

For the measurement, the period of the observed auto image will be modified.

This makes the measurement procedure described in the scientific article of

L.M. Sanchez-Brea et al. 2014 is not valid for a device that acts

in standard conditions.

In the present invention, to determine the degree of collimation of a beam

twenty

of light, it is proposed, first, to compare the period of at least two

self-images generated by a diffraction network 3, and not as proposed

in the article [L.M. Sanchez-Brea, F.J. Torcal-Milla, J.M. Herrera-Fernandez,

T. Morlanes, and E. Bernabeu "Self-imaging technique for beam collimation"

Optics Lelters 39 (19) 5764-5767 (2014) J between the period of the network of

2S

diffraction 3 and one of its self-images.

Regarding the measurement of the period of the self-image, in said article

consider using a linear array of photodetectors or a two-dimensional camera

to get the data of the experiment. Because the extent of the

luminous intensity of the generated auto images / (x) is usually quite

30

Noisy, the use of the semivariogram function is proposed for the measurement of

period of the self-images, defined as [LM Sanchez-Brea, FJ Torcal

Milla, E Bernabeu "Variogram-based method for contrast measurement"

Applied Optics 46 (22) 5027-5032 (2007) J

y (h) = ~ ([l (x + h) - / (x) J2) x '(1) 2

where x is the central position of the photodetectors and (-) means spatial average with respect to x.

First, since the semivariogram of a periodic function is also periodic with the same period there is no variation in the measurement of

5 same. Second, because it is calculated as averages

spatial statistics, the semivariogram function is able to eliminate

I random fluctuations characteristic of intensity measurements and, therefore, I

1 can calculate the period of the self-image with less uncertainty than if

We made directly from the measurements of light intensity. In

~

10 said article calculates the position of the first minimum of the

semivariogram And, through them, a linear adjustment is made. When the

Signal and semivariogram quality is good, as when using a

beam from a laser, this technique is acceptable. However, in the

The present invention is intended to determine the degree of collimation for

t

15 partially consistent sources spatially and / or temporarily. So the

Self-images may have lower quality and be affected by noise.

l,

Thus, with this way of measuring the period, the required uncertainty results are not obtained.

F

!

To calculate the semivariogram period, an aspect of this

I

The invention refers to using a least squares adjustment to the entire semivariogram, rather than just the position of the minimum of the

f semivariogram, as was done in the cited scientific article. This allows to have a much greater number of points for the adjustment and, therefore, the period

Less uncertainty is calculated.

I

Another aspect of the invention relates to a method of collimating a beam of

!

light accurately by measuring the period of at least two 1, self-images generated by a diffraction network 3.

In Figure 1, an optoelectronic device is shown with which you can

both determine the degree of collimation of a beam of light and collimate a beam

r 30 of light, in both cases by measuring the period of two self-images

t

I produced by a diffraction network 3 whose period is not necessary to know. The only necessary requirement is that these self-images are produced at

Different distances Be a beam of light with a degree of collimation

!

I l · unknown, coming from a light source 1. For example, said beam I

35 may come from a laser, a laser diode, an LED or a type of light source

t.

one:

,

!

with a certain spatial or temporal partial coherence. This beam is

try to collimate using a collimation element 2 that can be a lens of a focal object f, a set of lenses or a diffractive optical element. Subsequently, a location network 3 is located that produces 5 self-images in Talbot's semi-distances Zk = k P '/ A, where k is an integer. If the lighting source 1 is not located at a distance f from the collimation element 2, but has a displacement !! z with respect to

I

I this point, the beam presents a certain convergence or divergence

j '

depending on the sign of !! Z. This beam crosses the diffraction net 3. At a

i 10 distance z "between the diffraction network 3 and the observation plane where a photodetection system 4 is located, a periodic distribution of light is obtained, where the period is determined by

Pt.z = (1 + az,) p, (2)

¡¡

being "'" - !!. z / f'. The distance z, can be that of a self-image,

15 that is, the semi-distance of Talbot Zk = k p2 / A, with k = 1,2, .., etc., or other

distance in which there is a periodic modulation of the light quantity. If we locate two photodetection systems 4 of the self-images

at different distances Z2A and Z2B. about each of the systems of

t ! photodetection 4 self-images will be generated whose period will be PA and Pe, t 20 respectively.

I I Through the measurement of the period of these self-images you can

I determine the degree of collimation of a beam of light. However, the

!

Auto images with light intensity ¡(x) normally present

!

I random fluctuations due to effects such as dirt, 25homogeneities of the light beam, errors in the manufacturing of the networks of

'.

diffraction, etc. That is why equation (1) is used to determine! Self-image period.

I

If a CCD camera, CMOS, or a linear array of photodetectors is used

as a photodetection system 4 to capture the intensity distribution

r

I 30¡ (x), the pixels are distributed periodically. Therefore, the definition of the semivariogram can be simplified as follows:

l '

l '

i.

; •

or.

'.

where N is the total number of pixels, l¡ = I (imflx) is the light intensity

of the beam measured with the pixel i, and Ilx is the distance between pixels.

In Figure 2a, an intensity profile is shown as an example

experimental [(x) for a lighting source 1 LED whose length of 5 medium wave is 880 nanometers and a diffraction network 3 whose period is 100

micrometers the self-image is measured at a distance Zz = 22.72 millimeters

where the photodetection system 4 is located. Figure 2b shows the semivariogram obtained with equation (3) for the example of Figure 2a. As can be seen, although the light intensity distribution [(x)

10 of the self-image is not of great quality, the semivariogram is very smooth and sinusoidal. From a theoretical point of view, the semivariogram of a pure sine function is also a pure sine function of the same period.

However, when the periodic signal has fluctuations, these are reflected

in the semivariogram envelope, not in its period. Therefore, for

15 determine the period accurately, the semivariogram can be adjusted

experimental to the next function

2y (h) = (a, + p, h + y, h '+ 8, h3) - (a, + p, h + y, h' + 8, h3) cos ('; h), (4)

where a polynomial adjustment is made to the upper and lower envelopes. With

this adjustment, which can be done using adjustment algorithms or

20 optimization, the period p of the self-image is obtained. Once determined

the PA and PB period of the two self-images using this procedure is

possible to calculate the degree of collimation of the beam. To do this, we use the

Equation (2) for each of the distances Z'A YZ ,.

P. = (1 + az,.) P, (5) 25 P. = (1 + az,.) P.

Dividing both equations and clearing determines the value of the degree

of collimation to,

a = (6)

Also, it can be determined that the light beam is collimated when the

The period of the two self-images, obtained by the two photodetection systems 4, is the same.

Also, from the definition of a, a; -tlzj [', you can determine the distance between the light source 1 and the focal plane object of the element of

collimation 2, which turns out to be

I1z = PB-PIl f2. (7)

PBZ2A-PAZ28

5 Therefore, one aspect of the invention relates to a method for determining the degree of collimation of an applicable light beam regardless of the degree of coherence and / or the chromaticity of the beam,

as well as the environmental conditions in which you are immersed, and

it is more robust than other prior art options compared to

10 variations of the opto-mechanical conditions of the configuration for

implementation of the mentioned method, The method comprises:

a) make the light beam affect a diffraction network 3,

b) detect at least two self-images generated by the diffraction network 3

from step a), each being at a different distance from Talbot, ZA * -ZB.

15 of said diffraction network 3,

e) determine the PA and P. periods of the self-images detected in step b),

d) calculate the degree of collimation of the beam a through the equation

to;

(6)

20 The period P of the diffraction network 3 may or may not be known. In addition, the

diffraction net 3 can act by reflection or transmission, which determines

that the beam is reflected in the diffraction network or transmitted to its transverse network

diffraction 3 can be a Ronchi network, which modulates the amplitude, although it could also be a network with a sinusoidal modulation or other type of

25 amplitude modulation and phase.

The determination of the PA and PB periods of the self-images can

, be performed using any adjustment algorithm that allows high

I!

resolution; preferably, it is done using the semivariogram adjustment function technique

¡. , 30 2y (h); (a, + p, h + y, h '+ li, h3) - (a, + p, h + y, h' + li, h3) cos (2rrhjp), (4) !

The invention also relates to a method of collimating a beam of light. This

! ! method comprises:

,

,

i

l

0,

a) make the light beam to collide on a collimating element 2,

b) make the collimated beam in step a) impact on a diffraction net 3,

e) detecting at least two auto-images generated by the diffraction network 3 of step b) at least two different distances from Talbot, ZA, Z8 'of said diffraction network 3,

d) modify the distance between the light source 1 and the collimator element 2 by moving the light source 1 and that of the collimator element 2 along the optical axis, and repeat step e) until periods PA and Pe of the self images are the same.

To obtain this position accurately, one option is to determine the

intersection of linear adjustments to least squares obtained by

a scan of the measurements of the periods of the self-images when moving the light source 1 and the collimating element 2 along the optical axis, following

the following steps:

i) Make an adjustment for least squares to each of the expressions

PA = (1 + aZ2A) P, (S)

Pe = (1 + aZ, e) P ·

ii) Determine the intersection of the adjustments made in i).

Another option is to calculate P. = IPAPe / (PA -PB) I and move the light source 1 and the collimating element 2 along the optical axis until P. tends to

infinite.

A third option to determine when PA = PB, in the case that

produce Vernier stripes, is to shift the light source 1 and the element

Collimation 2 until the Vernier stripe pattern visually disappears.

The collimation element 2 can be a lens, a set of lenses or a

diffractive optical element or a diffracto-refractive hybrid.

The period P of the diffraction network 3 may or may not be known. In addition, the diffraction network 3 can act by reflection or transmission, which determines

that the beam is reflected in the diffraction network or transmitted through it. The net

,

,

,

Diffraction 3 can be a Ronchi network that modulates the amplitude, although it could also be a network with a sinusoidal modulation or other type of amplitude and / or phase modulation.

The determination of the p, and P. periods of the self-images can be carried out using any adjustment algorithm that allows a low

uncertainty; preferably. It is done using the semivariogram adjustment function technique

2y (h) = (a, + P, h + y, h '+ 8, h') - (a, + p, h + y, h '+ 8, h') cos (2rrh / p), ( 4)

An example of obtaining the collimation point by determining the intersection of the adjustments made in ii} is shown in Figure 2.

In order to be able to measure the period of two auto images generated by a diffraction network 3 and generate a collimated beam according to the described methods, the present invention also relates to several optoelectronic devices

designed for this purpose. In all of them, to create a collimator device, you

add to the device a collimation element 2 between the light source 1 and the diffraction network 3. The collimation element 2 can be a lens of a

focal object t, a set of lenses or a diffractive optical element.

To determine the degree of collimation of a light beam, a first optoelectronic device is schematically represented in Figure 1 and includes:

-

a diffraction network 3 of period p, which may or may not be known, which is located on the optical axis of the device and which generates self-images,

-

at least two photodetection systems 4, which can be linear arrays of photodetectors, CCD cameras or CMOS cameras, which are located

located outside the optical axis and at different distances Z2A and Z2B with respect to

the diffraction network 3, where two self-images are found,

-

an electronic device 5 for processing the signals received by the photodetection systems 4 for obtaining the periods p, and P. and, in the case that the optoelectronic device is used to collimate a light beam, for the monitoring of the distance! Jz

Figure 1a is a perspective view and Figure 1b is a side view. The photodetection systems 4 and the electronic processing device of the separated auto images 5 are shown for better

understanding but, in this device, at least one of the systems of

Photodetection 4 could be attached to the electronic processing device

of the self-images 5.

A second optoelectronic device is represented in Figure Figure

S

4. In this case, a beam splitter 6 is included in the optical axis between the network of

diffraction 3 and two photodetection systems 4, so that the two

photodetection systems 4 are located at the output of beam splitter 6,

one located on the optical axis of the device and the other on the axis perpendicular to the

same, being able to measure the same area of the diffraction net 3. By placing

10

the two photodetection systems 4 at different distances, taking as

origin of the diffraction network 3, two self-images are obtained from one

single area of the diffraction network 3. It shows the systems of

photodetection 4 and the electronic device for processing

5 separate images for a better understanding but, in this

IS

device, at least one of the photodetection systems 4 could be attached

to the electronic processing device of the self-images S.

A third optoelectronic device includes two mirrors 7 located at the

output of beam splitter 6, one located on the optical axis of the device and the other

perpendicular to it, with the mirrored face facing the divider of

twenty

make 6 so that the two mirrors 7 redirect the light to a single

photodetection system 4, as shown in Figure 5 Figure 5. Each

one of the two mirrors 7 includes on its mirrored face a mask 8 of

an opaque and anti-reflective material that blocks part of the beam in such a way

that the self-images do not overlap.

25

A particular variation with respect to the third optoelectronic device is

refers to a fourth device, shown in Figure Figure 6a, which includes

two mirrors 7 but, in this case, without opaque anti-reflective masks.

These mirrors redirect the light to a single photodetection system 4

where the two auto images sotapan. If light sources are used that are not

30

they have a high degree of coherence, there is no interference between

two images but overlap, producing a new pattern of stripes

known as the Vernier stripe pattern (Figure Figure 6b). In this case,

the period of the Vernier stripe pattern is much longer than the period

of the self-images located in ZA and zB 'that have a period similar to

3S

period of the diffraction network 3 that generates them. Therefore, the

collimation position of the beam significantly increasing accuracy. In

13

In this case, the device is useful for collimating a beam of light, either through the equation Pv = IPAPB / (PA -PB) I, or visually.

A fifth optoelectronic device is represented in Figure Figure 7

and is formed by a diffraction network 3, a photodetection system 4 and an electronic device 5 for processing the self-images generated by the diffraction network 3 and comparing the periods PA and PB 'In this case, the photodetection system 4 an angle 8 is inclined with respect to the optical axis of the device, so that multiple self-images are obtained from which at least two are chosen to measure the degree of collimation of the light beam from the light source 1, of according to the method of the invention. The angle 8 can be 45 "± 30".

photodetection systems 4 can be located in a camera with

Two-dimensional distribution, such as a CMOS camera or a CCD camera.

On the other hand, as an electronic data processing device 5 an electronic board, a microprocessor or a computer can be used.

Brief description of the figures

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, a set of drawings is accompanied as an integral part of said description.

where, for illustrative and non-limiting purposes, the following has been represented:

Figure 1. Schematically shows the basic configuration of one of the optoelectronic devices of the invention and the distribution of the

different components: 1 light source, 2 collimation element which, in this case, is a lens, 3 diffraction network, 4 photodetection system that can be a linear array of photodetectors, a CCD or CMOS camera,

presenting in this configuration two photodetection systems located at distances from Talbat ZZA and 228. respectively, ZZA * "228, 5

electronic device for processing the self-images and comparing the PA and PB periods

Figure 2. (a) Shows an example of experimental intensity profile ¡(x) obtained with a diffraction network 3 of period P = 100 micrometers measured at a distance z of 22.72 milli meters, where a photodetection system 4 is located (b) It shows an example of a semivariogram obtained for the signal of Figure 2a (dashed line) and adjustment of said semivariogram to the function described in equation (4) (continuous line).

Figure 3. Experimental calculation of the period of the auto images according to Example 8, using the technique described in equation (5).

Figure 4. Shows, schematically, the configuration of a device

of the invention in which a beam splitter is used 6. Figure 5 Figure 5.

It shows, schematically, the configuration of a device of the invention in which two mirrors 7 are used at the exit of a beam splitter 10 6, a mirror located on the optical axis and the other mirror located perpendicular to the optical axis, with the mirrored face facing the

beam splitter 6, so that the mirrors redirect the light to a system

of photodetection 4 composed of two or more linear arrays of photodetectors belonging, for example, to a CMOS camera.

Figure 6. (a) Schematically shows the configuration of a device of the invention in which two mirrors 7 are used, without opaque and anti-reflective masks, so that they redirect the light to a system of

photodetection 4 composed of two or several linear photodetector arrays

belonging. for example, to a CMOS camera. (b) Example of Vernier's 20-stripe pattern among the distribution of superimposed intensity from

of the two mirrors 7 when the period of the self-images is different.

Figure 7. Schematically shows the configuration of a device of the invention in which a photodetection system 4 is used, consisting of several linear arrays of photodetectors or a two-dimensional array of 25 photodetectors belonging, for example, to a camera CMOS, whose main characteristic is that a certain angle 9 is inclined with respect to the axis

optical defined by the propagation of the light beam from source 1 to the

diffraction net 3.

Embodiment of the invention

30 Once the system geometry and yield process have been defined, examples of optoelectronic devices to measure the degree of collimation of a beam or collimate the beam and examples of both methods are presented below.

The invention is not limited to the specific embodiments described,

but also covers, for example, the variants that can be

carried out by the average expert in the field (for example. in terms of

choice of materials, dimensions, distances, components,

S

settings, etc.)

In particular, although preferred embodiments of the invention are

described for some specific photodetection systems, elements of

collimation, reflection and division of the beam, and generation of self-images, the

methods and systems described can be applied with other systems or

10

elements that fulfill the same function. They do not exist, therefore,

limitations inherent to the invention regarding the measurement and analysis of

self-images, the number of self-images, the element of collimation

used and its number, the auto image generator element, its number, and

its characteristics, the number of reflective elements and beam splitters as well

1S

as blockers thereof and their characteristics, wavelengths

used as well as the type and characteristics of the beam and / or the light source.

Example 1 An optoelectronic collimating device and an

optoelectronic device to determine the degree of collimation of a

twenty

1 LED light source (Hitachi model HE8807SG) wavelength

centered on A = 880 nanometers. As collimation element 2, it was included

a diffractive optical element (DOE, from English diffraclive oplica / e / emenl)

known as Fresnel lens whose focal length is f = 35 millimeters and

of diameter d = 20 mm manufactured by photolithography, in the case

2S

of the collimating device. In both cases, the device included a network of

diffraction 3 of period p = 110 micrometers manufactured in chrome on a

glass substrate As a photodetection system 4, two arrays were used

linear belonging to two CMOS two-dimensional cameras of the brand

Imaging Source, model DMK 72BUC02, pixel size 2.2 x 2.2

30

micrometers and a resolution of 2592 x 1944 pixels. These cameras are

located in the same plane as the diffraction network 3, perpendicular to the

light beam propagation, outside the optical axis and two distances from Talbot

different, Z 'A = 2p' / A = 27.50 millimeters and Z'B = p '/ A = 13.75 millimeters,

by originating the diffraction network 3. For numerical analysis,

35

he used a computer program running on a computer that acted as

data processing element 5. An outline of both devices

it is shown in Figures 1 a and 1b, in horizontal and transverse view, respectively; The collimating device includes the collimating element 2,

while the device to measure the degree of collimation does not include it.

Example 2. Figure 4 shows a second example. An optoelectronic collimating device and an optoelectronic device were manufactured for

determine the degree of collimation for smaller beams than with the

device described in Example 1. As a diffraction net 3, a network of period p = 100 micrometers made of chromium on glass was used. As collimation element 2, a focal lens f = 40 millimeters and diameter d = 20 millimeters of the Melles Griot brand was included, in the case of the collimating device. Based on the devices of Example 1, a beam splitter cube 6 was included between the diffraction network 3 and the photodetection system 4, placing it on the optical axis. A 6 beam splitter cube was used

N-BK7 substrate, non-polarized, with anti-reflective treatment, formed

by two right angle prisms connected by the hypotenuse, of the TECHSPEC brand ", model 10 mm NIR, of dimensions 10 x 10 x 10 mm, as shown in Figure 4. Beam splitter 6 divides the amplitude of the incident beam in two beams that travel in two directions perpendicular to each other, thus the two photodetection systems 4 were placed on the optical axis at Talbot distances Z'A = 5p '/ A = 56.81 mm and Z'8 = 2p' / A = 22.72 millimeters, taking as origin the diffraction net 3 yen

perpendicular planes to each other. With this provision, the advantage of

pick up the signal from the same area of the diffraction network 3.

Example 3. Figure 5 shows a third example of devices

optoelectronics for situations in which the number of photosensors is

limited. In particular, a collimating device and a

device to determine the degree of collimation in which a single photodetection system 4 is required. To do this, the basis of

devices of Example 2; two mirrors 7 of first surface, / 4 of 25 x 25 square millimeters, of surface area were included in the optical axis

improved aluminum, at distances Z2A = Sp2 / 2J .. = 27.90 mm and Z28 =

2p '/ 2, \ = 11.36 millimeters, taking as origin the diffraction network 3, in planes perpendicular to each other and with the mirrored face facing the beam splitter 6, so that they redirect the light to a single photodetection system 4 which, in this case, is a two-dimensional CMOS camera, of the Imaging Source brand, model DMK 72BUC02, of 2.2 x 2.2 micrometer pixel size and with a resolution of 2592 x 1944 pixels. In this way, a single photodetection system 4 is used instead of two. In addition, in each mirror 7, an opaque and matte black cardboard adhesive sheet of 25 x 12.5 square millimeters of surface was placed, aligned with the perimeter of the

mirror, as an opaque and anti-reflective mask 8, so that the

Self-images do not overlap. The photodetection system 4 and the

electronic device for processing of separate 5 auto images

for a better understanding, but in this device they could go stuck.

Example 4. Figure 6a shows a fourth example of an optoelectronic device for situations where even greater measurement accuracy is required. In particular, a collimating device and a

device for determining the degree of collimation based on the device of Example 3 where the mirrors 7 did not incorporate any opaque mask.

A composite lens system was used as collimation element 2

by two converging lenses of the Melles Griot brand whose focal length in

both cases is f '= 60 millimeters and the separation between them is 30 millimeters. With this arrangement, the self-images overlap the system.

of folodetección 4 producing a pattern of Vernier stripes whose size is larger than the period of the self-images, so the uncertainty

Commitment in its measurement is smaller. An example of this fringe pattern is

shown in Figure Figure 6b.

Figure 6a shows the photodetection system 4 and the electronic processing device of the separated self-images 5 for a better understanding, but in this device they could be attached.

Example 5. Figure 7 shows a fifth example of a device

Optoelectronic for situations in which the available space is limited. A collimating device and a device for determining the degree of collimation were manufactured in which a single photodetection system 4 was included. In this case a diffraction net made of chrome on glass was used.

whose period is p = 20 micrometers. After diffraction net 3, and on the axis

optical, a photodetection system 4 inclined 45 ° with respect to the

optical axis of the device. In this way, with a single system of

Photodetection 4, the periods of several self-images can be measured. In

In this case, the periods of two different self-images were measured in the

S

upper and lower rows of the photodetection system 4. Talbot distances

were Z'A = 4p 'lA = 1.82 millimeters and Z'B = Sp'lA = 2.27 millimeters,

taking as origin the diffraction network 3. As a photodetection system 4

the same chamber of Examples 3 and 4 was used. The system of

photodetection 4 and the electronic device for processing the

10

5 separate images for better understanding, but in this

device could go stuck.

Example 6. The degree of collimation of a beam was determined using the

devices described in Examples 1-3 and 5. For this, it was made

fifteen

pass a beam of light through each of the optoelectronic devices

described in the corresponding example. Since the semivariogram of a

Periodic function is in turn periodic, the semivariogram function was used

for a linear array of fatodiates,

(3)

twenty

to soften the signal of the autoimagenes detected by the systems of

Photodetection 4 and increase the measurement accuracy of the PA and PB 'periods

Periods were obtained through semivariogram adjustment.

corresponding to the function

2y (h) = (a, + Il¡h + y, h '+ Ihh') {(a, + lJ, h + y, h '+ o, h') COS C; h) j, (4)

2S

The degree of collimation a at each position of the light source 1 was obtained at

through expression

Ilz = PB-PA [2 PBzZA PAZZB (7)

since a ~ -MI! '

30

Example 7. A light beam was collided whose emitter is a light source 1.

For this, a beam of light was passed through each of the devices

described in Examples 1-3 and 5 comprising a collimating element 2

located in the position before a diffraction network 3 and in the optical axis of the system, as can be seen in the figures in which the

Schemes of the different optoelectronic devices. Since the semivariogram of a periodic function is in turn periodic, the semivariogram function was used for a linear array of photodiodes,

y (h = nL1x) = - () L7 = -; n (I '+ n _ 1,)', (3)

2 N-n

to soften the signal of the auto images detected by the photodetection systems 4 and increase the accuracy of the measurement of the periods PA and PB '

These were obtained through the adjustment of the semivariograms corresponding to the (anointing

y (h) = (a, + P, h + y, h '+ "lh') - {(a, + p, h + y, h '+", h') cos e: h) j, ( 4)

Then the difference of experimental periods t1p = PB was obtained

PA as a reference point and the light source 1 was shifted in the direction of the optical axis and in the direction of difference decrease monitoring

the modification of t1p until PB;: ;; PA so that t1p ::; :: PB -PA;: ;; OR.

Example 8. A light beam was collided whose emitter is a light source 1.

For this, a beam of light was passed through each of the devices described in Examples 1-3 and 5 comprising a collimating element 2

located in the position before a diffraction net 3 and in the optical axis of the

system, as seen in the figures in which the

schemes of the different devices_ Since the semivariogram of a periodic function is in turn periodic, the semivariogram function was used for a linear array of photodiodes,

y (h = n.1x) = - (1) L7 = -, nU '+ n _1,)', (3)

2 N-n

to soften the signal of the self-images detected by the systems of

photodetection 4 and increase the measurement accuracy of the PA periods and

Ps-These were obtained through the adjustment of the semivariograms corresponding to the function

y (h) = (a, + P, h + y, h '+ "lh') - (a, + p, h + y, h '+", h') cos e: h), (4)

In Figure 2a, an experimental intensity profile measured in

ZZB "In Figure 2b, the semivariogram obtained with the equation is shown

(3) for the intensity profile of Figure 2a (solid line). The period of the self-image is obtained from its adjustment to equation (4) (line

5 discontinuous). Using the device of example 2, two photodetector arrays 4 located at Z2A = 5p '/ 4 = 56.81 millimeters and Z'B = 2p2 / 4 = were used

22.72 millimeters to calculate the period of the self-images at different distances tJ.z between the light source 1 and the collimation element 2. When

the intersection of the linear adjustments is produced by the technique of

10 least squares of the expressions in equation (5), the period coincides, tJ.z = O is obtained and, therefore, is the position in which the

beam is collimated. The collimation point is obtained at the intersection of the

adjustments to least squares of the periods of both autoimagenes (Figure 3) which, in this example, was Z = 27.7842 millimeters.

Example 9. A light beam was collimated whose emitter is a light source 1. For this purpose a light beam was passed through the device described in Example 4 and in Figure 5a. When the self-images are inconsistent, the superposition is the sum of the intensities, so a Vernier stripe pattern shown in Figure 5b was produced. The term

of this periodic intensity distribution was calculated using the equation

Pv = IPAPB / (PA -PBll where PA and PB are the periods of the autoimagenes that were obtained at Talbot distances Z'A = 5p '/ 24 = 27.90 millimeters and Z'B = 2p2 / 24 = 11.36 millimeters, respectively, taking as origin the

25 diffraction net 3.

Since the Vernier stripe pattern is periodic, and the semivariogram of

a periodic function is in turn periodic, the semivariogram function was used for a linear array of photodiodes,

y (h = nt.x) = - (') L ~~ -, n (i "n -1,)', (3)

2 N-n

30 to reduce uncertainty in the measurement of Pv 'The period Pv was obtained through the adjustment of the semivariogram to the function

y (h) = (a, + fi, h + y, h '+ o, h3) - (a, + fi2h + y, h2 + o, h3) cos ('; h). (4)

The light source 1 was then moved in the direction of the optical axis and in the direction of increasing P. until PB; PA, so that P.

visually disappeared and analytically its value tended to infinity. In this

For example, there is the advantage that the period of the stripes of the Vernier patterns can be measured more easily than in the previous examples as the period of the stripes of the Vernier patterns is greater than the period of the self-images of the diffraction net 3.

Claims (25)

1. Method for determining the degree of collimation of a beam of light comprising the following steps: a) make the light beam affect on a diffraction network 3, b) detecting at least two self-images generated by the diffraction network 3 of step a) a, at least two different distances from Talbot, ZA, ZB 'of said diffraction network 3, c) determine the PA and PB periods of the self-images detected in step b), d) determine the value of a through the equation a = (6) where a ~ -f1z / f2, where f1z is the displacement of the light source 1 with respect to the distance f, and f being the focal distance of the element of collimation 2. 2. Method according to claim 1 wherein the periodic signal of the auto images detected in step b) is smoothed by calculating the  semivariogram (3). 3. Method according to claim 2 wherein the PA and PB periods of the auto images detected in step b) are obtained by adjusting each semivariogram to the equation 2y (h) = (a, + fJ, h + y, h2 + olh3) - (a2 + fJ2h + Y2h2 + 02h3) C05 ('; h) (4). 4. Method to collimate a beam of light comprising the following steps: a) make the light beam to collide on an element collimator 2, b) make the collimated beam in step a) impact on a diffraction net 3, c) detecting at least two self-images generated by the diffraction network 3 of step b) at least two different distances from Talbot, ZA, Z8 'of said diffraction network 3, d) modify the distance between the light source 1 and the collimating element 2 by moving the light source 1 and / or the collimating element 2 along the optical axis, and repeat step c) until the periods PA and P8 of the self images are the same. 5. Method according to claim 4 which, in step d), includes the following steps: i) Carry out an adjustment for least squares obtained by scanning the measurements of the periods of the self-images by moving the light source 1 and / or the collimating element 2 along the optical axis, to each of the expressions PA = (1 + az ,,) p, (5) P8 = (1 + aZ'8) P, ii) Determine the intersection of the adjustments made in i). 6. Method according to claim 4 wherein the periodic signal of the auto images detected in step b) is smoothed by calculating the semivariogram ¡¡ I 7. Method according to claim 6 wherein the periods PA and P8 of the Self-images detected in step b) are obtained by adjusting I I every semivariogram to the equation I ! 2y (h) = (a, + P, h + Ylh '+ o, h') - (a, + p, h + y, h '+ o, h') cos ('; h)} (4) . '4 (3). 8. The method according to claim 4, wherein it is detected that the PA and PB periods of the self-images are visually equal when the Vernier stripe pattern. 9. Method according to claim 4, wherein applying the formula PA is equal to PB when Pv tends to infinity. 10. Optoelectronic device for determining the degree of collimation of a light beam according to the method of claims 1-3 which understands:

-

a diffraction network 3,

-

at least two photodelection systems 4 located at different distances from the diffraction network 3, in planes parallel to the plane in which the

15 diffraction net 3 being at least one located outside the optical axis,

-

an electronic device 5 for data processing.

eleven . Optoelectronic device to determine the degree of collimation of a beam of light according to the method of claims 1-3 that 20 comprises:

-

a diffraction network 3,

-

a beam splitter 6 located next to the diffraction network 3 at

length of the optical axis of the device,

-

two photodetection systems 4 located in two different planes, 25 perpendicular to each other and parallel to two faces of the beam splitter 6, and a

different distances of beam splitter 6,

-

an electronic device 5 for data processing.

12. Optoelectronic device for determining the degree of collimation of a light beam according to the method of claims 1-3 which understands:

-

a diffraction network 3,

-

a beam splitter 6 located next to the diffraction network 3 along the optical axis of the device,

-

two mirrors 7 located in two different planes, perpendicular to each other and

parallel to two faces of beam splitter 6, with mirrored faces covered by two opaque and anti-reflective masks that block part of the beam in such a way that the self-images do not overlap, and oriented towards the beam splitter 6,

-

a photodetection system 4 located in a plane parallel to one face of the beam splitter 6 other than the two faces of the beam splitter 6 to which they are

parallel mirrors 7,

-

an electronic device 5 for data processing.

13. Optoelectronic device for determining the degree of collimation of a light beam according to the method of claims 1-3 which understands:

-

a diffraction network 3,

-

a photodetection system 4 located in an inclined plane at an angle e with respect to the plane in which the diffraction network 3 is located,

-

an electronic device 5 for data processing.

14.

Optoelectronic device according to claim 13 wherein the angle is 45 ° ± 30 °.

fifteen.

Optoelectronic device according to claim 14 wherein the angle is 45 °.

16.

Optoelectronic device according to any of claims 10-15 in which the photodetection systems 4 are located in a chamber with CMOS or CCD two-dimensional distribution.

17.

Optoelectronic device according to any one of claims 10-16 wherein the electronic device 5 is selected from the group formed

by: an electronic board, a microprocessor and a computer. 18. Optoelectronic device for collimating a light beam according to the method of claims 4-9 comprising:

-

a collimator element 2,

-

a diffraction network 3,

-

at least two photodetection systems 4 located at different distances from

the diffraction network 3, in planes parallel to the plane in which the diffraction network 3 is located and, at least one, located outside the optical axis,

-

an electronic device 5 for data processing.

19. Optoelectronic device to collimate a beam of light in accordance with the method of claims 4-9 comprising:

-

a collimator element 2,

-

a diffraction network 3,

-

a beam splitter 6 located next to the diffraction network 3 along the optical axis of the device,

-

two photodetection systems 4 located in two different planes, perpendicular to each other and parallel to two faces of the beam splitter 6,

-

an electronic data processing device 5.

t ! t ! I I I I ! I I i I I I, ¡¡ I I I I ! ! , 20. Optoelectronic device to collimate a beam of light in accordance with the method of claims 4-9 comprising:

-

a collimator element 2,

-

a diffraction network 3,

-

a beam splitter 6 located next to the diffraction network 3 along the optical axis of the device,

5-two mirrors 7 located in two different planes, perpendicular to each other and parallel to two faces of the beam splitter 6 and with the mirrored faces oriented towards beam splitter 6,

-

a photodetection system 4 located in a plane parallel to one side of the

beam splitter 6 other than the two faces of beam splitter 6 to those that are 10 parallel mirrors 7,

-

an electronic device 5 for data processing.

twenty-one . Optoelectronic device according to claim 20 wherein Mirrored surfaces of the two mirrors 7 are covered by paths 15 opaque and anti-reflective masks that block part of the beam in such a way that the self-images do not overlap. 22. Optoelectronic device to collimate a beam of light in accordance with the method of claims 4-9 comprising: 20 -a collimator element 2,

-

a diffraction network 3,

-

a photodetection system 4 located on an inclined plane an angle e

with respect to the plane in which the diffraction net 3 is located,

-

an electronic device 5 for data processing.

2. 3.

Optoelectronic device according to claim 22 wherein the angle e is 45 ° ± 30 °.

24.

Optoelectronic device according to claim 23 wherein the angle 8 is 45 "

25.

Optoelectronic device according to any of claims 18-24

5 in which the photodetection system (s) 4 are located in a camera with CMOS or CCD two-dimensional distribution. 26. Optoelectronic device according to any of claims 18-25 wherein the electronic device 5 is selected from the group formed 10 for: an electronic board, a microprocessor and a computer.