FR2512949A1 - OPTICAL MEASURING DEVICE BY COAXIAL LIGHTING - Google Patents

Abstract

A. THE INVENTION RELATES TO AN OPTICAL MEASURING DEVICE BY COAXIAL LIGHTING. B. DEVICE CHARACTERIZED IN THAT IT INCLUDES A LIGHT SOURCE COAXIALLY LIGHTING AN OBJECTIVE 2, ARRANGED IN FRONT OF A LENS 3, TO DETERMINE THE DIMENSIONS OR THE POSITION OF THE OBJECT 2, A PHOTODETECTOR 4 BEING PLACED ON THE IMAGE PLAN OF L 'OBJECTIVE 3 AT THE LOCATION OF THE IMAGE OF OBJECT 2 TO BE MEASURED. C. THE INVENTION FINDS ITS MAIN APPLICATION IN THE OPTICAL MEASUREMENT INDUSTRY.

Description

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  The invention relates to an optical measuring device

by coaxial lighting.

  Optical measuring devices are already known according to which, in order to improve the contrast, a light source is placed behind the object. However, this source

  is still too cumbersome and requires

  tidieux. The object of the present invention is to remedy these drawbacks and proposes to create a universal non-contact measurement device making it possible to determine and measure the position of an object, its dimensions or phenomena.

  such as moving a very fast object.

  Another object of the present invention is to

  kill measurements of dimensions or speeds for objects

  on the move, for quick movements or for

non-solid

  The present invention also aims to create

  an optical measuring device employing photo-

  detectors with great ease of adaptation and a good

  contrast making the measurement more reliable and insensitive to

  ambient lighting, these measurements being carried out with a power

low lighting.

  Finally, the present invention aims to create a lightweight and compact device incorporating lighting and sight, and adapting to most industrial or scientific conditions. For this purpose, the invention relates to an optical measurement device by coaxial illumination, characterized in that it comprises a light source coaxially illuminating an object, arranged in front of an objective to determine the dimensions or the position of the object, a photodetector being arranged on the image plane of the objective at the location of the image of the object

to measure.

  According to another characteristic, the light source

  sends a beam to retroreflective surfaces, the beam being returned to the photodetector associated with a

  electronic signal processing device.

  The use of retroreflective surfaces makes it possible to eliminate or simplify the installations arranged at the rear of the object which one wishes to measure in this way.

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  for example to make up the object with one or more patterns forming the retroreflective surfaces, or to place

  a retroreflective surface behind the object.

  According to another characteristic of the invention, the device comprises a condenser of the light beam in front of which is placed a screen provided with a slot, the light beam passing through the slot by determining a luminous slot, then crossing the lens to illuminate coaxially the object

  located in front of a retroreflective surface.

  According to another characteristic of the invention, the photodetector is arranged perpendicularly to the line of sight and cooperates with a beam splitter located between the photodetector and a light trap for capturing the beam.

unnecessary beam.

  According to another characteristic of the invention, the luminous slot is of a dimension greater than or equal to

to that of the photodetector.

  According to another characteristic of the invention, the light slot and the photodetector are located at a distance

equal of the objective.

  Finally, according to another characteristic of the invention

  the retro-reflective surfaces are arranged either

  behind the illuminated object, either on the object itself.

  The present invention will be better understood with the aid of an embodiment of an optical measuring device according to the invention, shown schematically, by way of non-limiting example, in the accompanying drawings in which: FIG. 1 is a side view of the device, FIG. 2 is a diagram showing the path

of the light beam.

  According to FIG. 1, the optical measurement device 1

  coaxial illumination comprises a light source S illuminates

  coaxially carrying an object 2 disposed in front of an objective 3.

  A photodetector 4 is arranged on the image plane of the objective

  3 at the location of the image of the object 2 to be measured.

  The device 1 also has reflecting surfaces 5 disposed behind the object but which can be

  also arranged on the object itself in the form of pins.

  iu) the function of the reflective surface being to

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  light beam emitted by the source S towards the photodetector

  4 requiring only low lighting power.

  The light beam emitted by the light source S passes firstly into a condenser 6 where it is sent onto a screen 7 having a light slot 8. The light slot 8 is of dimensions greater than or equal to the dimensions of the photodetector 4 In addition, the slot 8 and the photodetector 4 are arranged at an equal distance from the objective 3. The photodetector 4 is furthermore disposed perpendicularly to the line of sight and cooperates with a beam splitter 9 situated on the line of sight X. between the photodetector 4 and a

  light trap 10 for sensing the light beam

  Thus, the light beam emitted by the light source

  S is reflected through the retroreflected surface

  5 to the beam splitter 9 which sends a portion of this beam at right angles to the photodetector 4, the other portion deflected perpendicularly upwards by the beam splitter 9 being picked up by the light trap The photodetector 4 is connected has an electronic device

  signal processing not shown in this figure.

  The device 1 thus makes it possible to determine the size or the position of an object placed in front of the lens

  3 by making the image of this object on a photodetector 4.

  This photodetector 4 may consist for example of a

  photodiode, a CCD array of photodiodes, photoresists

  In the case of a photo-CCD network,

  diodes connected to an electronic device for processing the

  signal, the video signal is made logical in a comparison

  discriminating the illuminated diodes and the dark diodes.

  A counter defines either the dimension of the measured area,

  its position relative to the origin of the photodetector.

  The device 1 coaxially illuminates the object 2 via the shooting objective 3, the light beam being condensed and then passing through a light slot 8 before passing through a beam splitter device 9. This beam splitter device can be consisting of a semi-transparent blade, a lighter cube, or a

  Fresnel prism or the like. The reflected light beam

  chi is separated by semi-transparent wool 9, for example I () on the one hand, downward on the photodetector 's, and, on the other hand,

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  on the upside, where is placed the light trap capturing this useless beam The light trap 10 also makes it possible to

reduce parasitic effects.

  The retroreflective surfaces 5 make it possible to improve the contrast of sight by being placed either on the background, behind the object aimed at, the object then appearing dark on a light background, or being arranged on the object aimed at it. - even in the form of test patterns, for example, to define the position or the limits of this object.

  appears in clear on a dark background.

  The retroreflective surface 5 can be

  stained with paint or adhesive plastic that adapts easily

  It may also be constituted by plastic blocks of the retro-reflector type intended to be glued or screwed. The use of these retroreflective surfaces requires a minimum of implementation. When placed at the rear of the object, they must be larger than the image spot of the light source S Furthermore, these reflecting surfaces are insensitive to the angle of incidence of the light and this in a range depending on their manufacturing technique According to FIG. device 1 reveals the path

  of the light beam E This is emitted by the light source

  S then passes on the condenser 6 before crossing the

  light slot 8 and the semi-transparent plate 9 and the objective

  tif 3 to illuminate the object 2 and hit the

  The reflected beam is returned to the beam splitter 9 consisting of a semitransparent blade from which the useless beam is sent at right angles to the line of sight X towards the beam splitter 9.

  the light trap 10 o this beam portion is captured.

  The light trap 10 is disposed above the semi-circular blade.

  transparent 9 relative to the line of sight X. The useful beam is sent to the photodetector 4 disposed below the line of sight X The photodetector is connected to an electronic device 11 for processing the emitted signal The device It makes it possible to determine the measurement is

  the size of object 2, ie its position or displacement.

  The device 1 makes it possible to use the properties

  retro-reflective surfaces to the optimum of their

  ment, ie for a zero divergence between the beams

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  The result is an impression of the photodetector with a good performance by requiring only a weak and very localized lighting power.

  retroreflective surfaces provides a high contrast

  making precise measurements with the different types of detectors and this with a small influence of ambient lighting. The device 1 also makes it possible to adapt to all the focusing distances and distances of the measured object. Thus, if the lens is moved for a different focusing, the light source S remains focused as soon as the image of the object 2 is clear on the photodetector

  4 This greatly simplifies the adjustment operations.

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Claims (6)

  1) Optical measuring device by coaxial illumination, characterized in that it comprises a light source S coaxially illuminating an object (2) arranged in front of an objective (3), to determine the dimensions or the position of the object (2). ), a photodetector (4) being arranged on the image plane of the objective (3) at the location of the image of the object (2) to measure.   2) Measuring device according to claim 1, characterized in that the light source S sends a beam on retroreflective surfaces (5), the beam being returned to the associated photodetector (4)   to a device -11) electronic signal processing.   3) Measuring device according to the claims   dications 1 and 2 above, characterized in that it comprises a condenser (6) of the light beam in front of which is placed a screen (7) provided with a slot (8), the light beam passing through the slot (8) determining a bright slot, then crossing the lens (3) to light coaxially   the object (2) located in front of a retroreflective surface (5).   4) Measuring device according to one   any of the preceding claims 1 to 3, characterized   in that the photodetector (4) is arranged perpendicularly to the line of sight X and cooperates with a beam splitter (9) located between the photodetector (4) and a light trap (10)   intended to capture the unnecessary beam.   ) Measuring device conforming to one   any of the preceding claims 1 to 4, characterized   in that the light slot (8) is of a larger size   or equal to that of the photodetector (4).   ) Measuring device conforming to one   any of the preceding claims 1 to 5, characterized   in that the light slot (8) and the photodetector (4) are   located at equal distance from the objective (3).   7) Measuring device according to one   any of the preceding claims 1 to 6, characterized in that   the beam splitter (9) is a semitransparent blade, a light cube, a Fresnel prism, or the like. 8) Measuring device according to one 7 2512949   any of the preceding claims to 7, characterized in   the photodetector (4) consists of a photodiode, a CCD array of photodiodes, photoresistors or the like. 9) Measuring device according to one   any of the preceding claims 1 to 8, characterized   in that the retroreflective surfaces are arranged either   behind the illuminated object (2), either on the object (2) itself.