DE102017212130A1 - Decoupling element for a light guide for guiding light on a light transit time sensor - Google Patents

Abstract

Arrangement with a light transit time sensor (22) which has an active light transit time pixel (24), a reference pixel line (26) for reference measurements and a decoupling element (200), the decoupling element (200) having a decoupling area (220) for illuminating the reference pixel line (26 ), with a light guide (260) which is guided in the outcoupling region (220) such that the light emerging at the light guide (260) at an angle of incidence αy ≤ 30 ° with respect to an axis (y-axis) transverse to the longitudinal extent ( x-axis) of the reference pixel line (26), - wherein the decoupling region (220) is also designed such that over the longitudinal extent (x-axis) of the coupling-out region (220) via the light guide (260) coupled light the pixels of the reference pixel line (26) achieved with different intensities.

Description

The invention relates to a coupling element for a light guide for guiding light on a light transit time sensor according to the preamble of the independent claim.

In particular, systems are to be encompassed here with the time of flight camera system which determine distances directly from the light transit time or which gain the light transit time from the phase shift of an emitted and received radiation. As a light transit time or 3D cameras in particular PMD cameras with photonic mixer detectors (PMD) are suitable, as in the DE 197 04 496 A1 described and, for example, by the company 'ifm electronic GmbH' or 'pmdtechnologies ag' as O3D camera or as CamBoard relate. In particular, the PMD camera allows a flexible arrangement of the light source and the detector, which can be arranged both in a housing and separately.

The object of the invention is to improve the reliability of the distance measurements of a light transit time camera or a light transit time sensor.

The object is achieved in an advantageous manner by the decoupling element according to the invention of the type of the independent claim.

Advantageously, arrangement is provided with a light transit time sensor, wherein the light transit time sensor has an active light transit time pixel ( 24 ) for distance measurement, a reference pixel line ( 26 ) to reference measurements and a decoupling element ( 200 ), wherein the decoupling element ( 200 ) a decoupling area ( 220 ) for illuminating the reference pixel line ( 26 ) having
and a light guide ( 260 ) into the decoupling area ( 220 ) is guided in such a way that at the light guide ( 260 ) light emerging at an angle of incidence αy ≤ 30 ° (αy denotes the angle of incidence projected onto the yz-plane relative to the z axis) relative to an axis (y-axis) transverse to the longitudinal extent (x-axis) of the reference pixel line ( 26 ),
- where the decoupling area ( 220 ) is also designed such that over the longitudinal extent of the coupling-out region ( 220 ) the light coupled in via the light guide reaches the pixels of the reference pixel line with different intensities.

This approach has the advantage that the reference pixel line can be illuminated on the one hand with a light gradient and, on the other hand, crosstalk of the reference light into the active pixel region can be avoided.

It is particularly advantageous if the material of the decoupling element has a Shore hardness between A40 and A70 and preferably between A45 and A65. In this area, the material on the one hand has sufficient stability to remain dimensionally stable at the intended contact pressure and on the other hand is soft enough to be light-tight against the sensor surface.

Preferably, the coupling-out region is designed to form an intensity gradient over the longitudinal extent as a solid material or as a cavity, wherein the solid material or an inner side of the cavity has particles and / or structures which scatter and / or absorb light.

By virtue of this procedure, it is advantageously possible to adapt the intensity gradient in the decoupling area with regard to the expected dynamics on the basis of, for example, different integration times.

In addition, the decoupling element is designed such that no extraneous light can penetrate into the decoupling element and no coupled-in light can escape outside the provided exit regions.

Preferably, the decoupling element in the areas in which no coupled light is guided, formed opaque.

Particularly advantageous is an arrangement with the aforementioned decoupling element and a light transit time sensor is provided, wherein the arrangement in particular has a frame for placement on a component carrier and receiving the decoupling element, and the frame at the bottom spacer to provide a defined distance between the component carrier and frame.

Advantageously, spacers for providing a defined distance between the frame and a cover glass are also provided on the upper side of the frame.

The use of the spacers has the advantage that a defined distance can be set between the frame and the component carrier as well as the cover glass so that, as a result, the clearance height between cover glass and component carrier or sensor surface can be set in a defined manner.

In addition, it is useful if recesses are arranged in the direction of the underside of the frame on the outer circumference of the frame. These recesses can on the one hand serve to allow a visual inspection of an applied adhesive bead between the frame and the component carrier, on the other hand, UV curable adhesives can specifically be exposed to UV light via these recesses be illuminated, and to ensure a defined adhesive gap thickness.

The invention will be explained in more detail by means of embodiments with reference to the drawings.

They show schematically:

1 Light transit time sensor with a reference pixel,

2 a top view of a light transit time sensor with a reference pixel array,

3 an overview of the arrangement according to the invention,

4 an inventive arrangement with a decoupling region designed as a cavity

5 a geometric orientation of the light guide,

6 an alignment according to 5 related to the sensor areas,

7 a detailed view with an optical fiber guide according to the invention,

8th a detailed view according 7 with a microlens array.

In the following description of the preferred embodiments, like reference characters designate like or similar components.

1 shows a light transit time sensor 22 with several light time pixels 24 and reference time of flight pixels 26 , The reference light-propagation time pixels 26 be over a light guide 260 illuminated with a reference light. The reference light may originate, for example, from a reference light source or directly from the illumination light source 12 come. Preferably, the reference light propagation time pixels are 26 in structure and function identical to the light time pixels 24 of the remaining sensor 22 and are preferably controlled identically. In the illustrated case, the reference light-propagation time pixels become 26 spatially from the remaining light-time pixels 24 discontinued by two rows of light-propagating time pixels or possibly also several rows with an opaque masking 28 be covered.

Such masking 28 has several advantages. On the one hand, the spatial offset causes crosstalk across the optical fiber 260 brought reference light on the active light transit time pixels 24 prevents, on the other hand, over the masked pixels 25 dark measurements can also be made as a further reference.

Of course, arrangements are also conceivable in which masked pixels 25 is omitted and the reference Lichtlaufzeitpixel 26 spatially offset from the pixel array of the light transit time pixels 24 are arranged.

It is also conceivable, in addition or as an alternative to the above-mentioned considerations, the measurement results of the light transit time pixels 24 caused by the light input at the reference light-propagation time pixel 26 be discouraged. In such an arrangement, a spatial spacing of the reference pixels and a masking of the intermediate pixels may also be dispensed with.

In 2 is a plan view of a light transit time sensor 22 according to 1 shown with an additional reference pixel column. About a light guide 260 becomes part of the illumination light source 12 emitted light on the reference pixels 26 directed. Depending on the application and need, additional columns with reference light duration pixels may also be available 26 be provided.

The decoupling of the optical signals of the illumination light source 12 allows it via the reference runtime pixels 26 to provide a reference for the distance measurement. Starting from signals of the reference light-propagation time pixels 26 Reference values can be determined, on the basis of which, for example, system-related effects influencing the distance measurement can be compensated. In particular, effects in the conversion of electrical into optical signals can be taken into account and compensated, such as, for example, a changing response of the electro-optical converters due to temperature and aging effects. Particularly advantageous are the reference light-propagation time pixels 26 preferably operated with the same modulation signals and integration times as the remaining light transit time pixels 24 ,

Furthermore, to avoid saturation of the reference light-propagation time pixels 26 be provided, the light coupling or decoupling in the light guide 260 to affect such that the reference Lichtlaufzeitpixel 26 work in an optimal area.

With the decoupling element according to the invention, it is now provided, the reference Lichtlaufzeitpixel 26 To apply different light intensities, so that, for example, regardless of the sensor 22 used integration times, at least one reference Lichtlaufzeitpixel 26 works in a preferred workspace.

In 3 is an example of a possible arrangement with a decoupling element according to the invention 200 shown. On a component carrier 500 are several components 510 and a light transit time sensor 22 with a time of flight pixel area 24 and a reference light-time-pixel region 26 arranged. For mechanical protection of the light transit time sensor 22 is also a cover glass 310 provided in the installed state on a frame 300 above the sensor 22 is appropriate. The frame has on one side a recess for receiving the Auskoppelements 200 on. The light guide to be introduced 260 is not shown for the sake of clarity.

In 4 is the arrangement according to 3 in the assembled state in cross section along the line XX 'shown. The sensor 22 is inside the frame 300 and becomes of that above the frame 300 mounted cover glass 310 protected. The decoupling element 200 is between frames 300 and the cover glass 310 within the recess of the frame 300 arranged. The decoupling element 300 preferably has a recess for the frame 300 corresponding groove, wherein depression and groove are coordinated so that the coupling element 200 is fixed laterally. A vertical fixation is about the contact pressure of the overlying cover glass 310 reached.

frame 300 and cover glass 310 are preferably glued together, but also clamping connections are conceivable. The frame in turn is with the component carrier, not shown here 500 connected, for example by gluing, screws, clamps, soldering etc.

A further embodiment of the invention may represent the use of a not yet completely cured silicone that loses its contact pressure over time to the splices between frame 300 and component carriers 500 and between frames 300 and glass 310 to relieve. Another advantage would be the improved conformability of the silicone.

The light guide 260 is from above a recess of the cover glass 310 and a recess of the Auskoppelements 200 in a lateral area of a decoupling area 220 the decoupling element 200 approach leads. The decoupling element 200 is in the decoupling area 220 translucent and designed so that the over the light guide 260 introduced light in the decoupling area 220 penetrate and over the bottom of the reference light time pixels 26 can be supplied. The remaining outer surfaces are formed opaque.

The margins of the bottom of the decoupling area 220 are designed so that they lie substantially light-tight on the sensor.

Is the decoupling area 220 formed as a transparent solid material, the arrangement is dimensioned so that the underside of the coupling-out area 220 flat on the reference light time pixels 26 rests.

Preferably, the decoupling element 200 at least in the decoupling area 220 made of an elastic material, such as silicone or other elastic and transparent material and / or hollow. Due to the elasticity of the exit surface nestles particularly close to the surface of the sensor 22 at. The arrangement is preferably designed such that between the exit surface and the reference light-propagation time pixels 26 No air pockets are located and / or forced out. In a hollow outcoupling area 220 The border areas nestle equally against the sensor surface. Preference can here for the coupling element 200 and in particular the decoupling area 220 Materials are used, which have a Shore hardness between A40 and A70 and preferably between A45 and A65. In this case, the opaque areas may, for example, have a carbon black content of 2-8% by weight, preferably 4-7% by weight and especially preferably 5% by weight.

The areas of the decoupling element which are not intended to carry light are preferably made opaque and / or light-absorbing. It can also be provided that additionally or alternatively the surfaces of the coupling-out element 200 where no light should escape are coated with an opaque material.

To illuminate the reference light-time pixels 26 with different light intensities, it is provided according to the invention, the coupling-out area 220 in such a way that the light intensity over the longitudinal extent of the coupling-out area 220 decreases. For example, the coupling-out region can be filled with light-scattering and / or light-absorbing particles. To achieve or enhance an intensity gradient, it is possible if necessary to change the degree of particle filling or particle quantity and / or size. A coloring with other materials is conceivable. The intensity gradient is preferably chosen such that the dynamic range of the selectable integration times is covered.

In the embodiment according to 4 the coupling-out area is not formed as a solid material, but as a cavity. The inner surfaces of the Cavities are preferably coated with a light absorbing material. Alternatively or additionally, the inner surfaces may also have a light-absorbing structure. Also by this procedure, gradient in the light intensity over the longitudinal extent of the coupling-out region 220 realized.

To crosstalk the reference light into the active pixel area 24 to avoid, it is according to the invention as in 5 provided, the light only within predetermined spatial directions in the reference pixel area 26 and the angle of incidence of the light with respect to a lateral axis of the light transit time sensor 22 suitable to align. In the illustrated case, the axes x and y extend laterally and the z-axis perpendicular to the surface of the sensor 22 , wherein the angle of incidence α is controlled according to the invention with respect to a preferred spatial direction. According to the invention, it is provided that the angle of incidence α be controlled in relation to an axis which lies transversely to the extent of the reference pixel line. This is the y-axis in the present case. The angle of incidence αy denotes the angle of incidence projected onto the yz plane relative to the z axis. The angle of incidence αx not shown for the sake of clarity denotes the angle of incidence projected onto the xz plane with respect to the z axis.

In 6 are the coordinate axes according to 5 in relation to the pixel areas 24 . 26 . 28 on the light transit time sensor 22 shown. The lateral x-axis of the coordinate system is in this case parallel to a longitudinal extent of the reference pixel line 26 and the lateral y-axis aligned perpendicularly or transversely to the x-axis. The lateral y-axis points towards the metallization 28 and the active pixels 24 ,

According to the invention, it is now provided that the incidence of light α of the reference light via the light guide 260 be aligned so that the oriented in the y direction angle of incidence α _y does not exceed a critical angle of 30 °. The orientation of the light guide 260 with respect to the x-axis is not critical and can also angle of incidence αx> 30 ° occupy.

7 shows a corresponding embodiment in which the optical fiber 260 in the decoupling area 220 guided and aligned according to the invention. The light guide 260 is in the decoupling area 220 oriented or arranged such that at an exit surface 286 of the light guide 260 emerging light with an angle of incidence αy ≤ 30 ° on the light transit time sensor 22 or the reference pixels 26 occurs.

This approach has the particular advantage that, due to the steep angle of incidence α, a light infiltration of the pixel masking 28 can be avoided.

The coupling-out element according to the invention can be particularly advantageous 200 for a light transit time sensor 22 with microlenses 29 , as in 8th shown used.

microlenses 29 is typically applied as one of the last processes in a receiving chip manufacturing, such as CMOS or CCD manufacturing, such that the illustrated pixel masking 28 lies below the microlens array. In a grazing incidence of light in the decoupling area 220 There is now a risk that light from the decoupling area 220 in the active pixel area 24 arrives. This can be reliably avoided if the light in the above-mentioned limits substantially perpendicular or with an angle of incidence αy ≤ 30 ° to the light transit time sensor 22 As a result, the light conduction becomes inefficient both in the microlens layer and in the masking layer.

LIST OF REFERENCE NUMBERS

12

 Illumination light source

22

 Transit Time Sensor

24

 Light transit time pixels, active light transit time pixels

25

 masked pixels

26

 Reference light-propagation time pixel, reference pixel line

28

 masking

29

 microlenses

200

 outcoupling

220

 delivery region

260

 optical fiber

268

 Light output region

300

 frame

310

 cover glass

320

 light trap

500

 component support

510

 module

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19704496 A1 [0002]

Claims (6)

Arrangement with a light transit time sensor ( 22 ), which has an active light-time-pixel ( 24 ) for distance measurement, a reference pixel line ( 26 ) to reference measurements and a decoupling element ( 200 ), wherein the decoupling element ( 200 ) a decoupling area ( 220 ) for illuminating the reference pixel line ( 26 ), with a light guide ( 260 ) located in the decoupling area ( 220 ) is guided in such a way that at the light guide ( 260 ) emerging light in an angle of incidence αy ≤ 30 ° with respect to an axis (y-axis) transverse to the longitudinal extent (x-axis) of the reference pixel line ( 26 ), where the coupling-out region ( 220 ) is also designed such that over the longitudinal extension (x-axis) of the coupling-out region ( 220 ) via the optical fiber ( 260 ) coupled light the pixels of the reference pixel line ( 26 ) with different intensities. Arrangement according to one of the preceding claims, in which the material of the decoupling element ( 200 ) has a Shore hardness between A40 and A70. Arrangement according to one of the preceding claims, in which the material of the decoupling element ( 200 ) has a Shore hardness between A45 and A65. Arrangement according to one of the preceding claims, in which the coupling-out region ( 220 ) is designed to generate an intensity gradient over the longitudinal extent as a solid material or as a cavity, wherein the solid material or an inner side of the cavity has particles and / or structures which scatter and / or absorb light. Arrangement according to one of the preceding claims, in which the decoupling element ( 200 ) is formed opaque in the areas in which no injected light is guided. Time of flight camera with an arrangement according to one of the preceding claims.

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