Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/08—Mirrors
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
  • G02B26/02—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the intensity of light
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J1/00—Photometry, e.g. photographic exposure meter
  • G01J1/02—Details
  • G01J2001/0276—Protection

Definitions

• the present invention relates to the field of optical equipment for the observation of scenes having an area of very high luminosity.
• optical equipment for solar observation, or for industrial imaging, in environments using a laser beam.
• Observing scenes with a very bright area produces a dazzling effect when used by a human operator or a photosensitive sensor, or even irreversible degradation of the sensor -
• a large number of optical systems (eye, cameras , sensors) undergo performance disturbances, or even irreparable alterations, in situations of high light contrast in the presence of one or more high intensity light sources.
• the sun is an example, as well as laser beams for military users.
• the natural reaction of any sensor is to close the diaphragm (iris of the human eye) as much as possible in order to protect itself. In return for this protection, the weak light sources are no longer perceived, and affect the performance of the sensor to the point of rendering it possibly unusable.
• PCT patent application WO0023833A1 has also proposed a device and a method for suppressing bright lights by means of holographic techniques.
• This prior art device includes a plurality of switchable holographic elements (SHOEs), a plurality of detectors, as well as a processing circuit coupled to SHOEs and detectors.
• SHOEs switchable holographic elements
• Each SHOE has a field of vision.
• Each SHOE can have a detector with a visual coverage field covering practically the same points as the corresponding visualization field.
• the processing circuit activates the corresponding SHOE, which diffracts part of the incident light with respect to the SHOE in order to distance this light from an individual likely to perceive it.
• SHOEs can be made of a liquid crystal material dispersed in a polymer. The efficiency of this device is limited, and the disturbances in low light areas remain too high for certain applications requiring high image fidelity.
• a dynamic filtration system consisting in slaving the opacity of a filter element as a function of the light intensity detected by a sensor receiving part of the incident signal has also been proposed in American patent application US2000000988855.
• the object of the present invention is to provide a device ensuring that the incident beam containing the source (s) exceeding an adjustable threshold is rid of the amount of excess light coming from these sources, without altering the rest of the beam. The user therefore receives this modified beam and perceives the light coming from its initial source and not from a transformed image (electronic image for example). Besides other advantages, the main reason for this choice is that many users or security services do not accept to use electronic images instead of real images in any manned mobile system.
• the system according to the present invention consists of an input optic (objective), an active filter controlled through a detection / selection / control loop, a possible additional active filtration stage where can also be superimposed various information, and finally an output target adapted to the use.
• the invention relates, in its most general sense, to an optical device comprising a means of dynamic filtration of a source of very high luminosity, characterized in that said means of filtration consists of a mirror having a zone of least reflection and means for controlling the position of said mirror as a function of the position of the very high light source in the image formed on said mirror.
• said zone of least reflection consists of a hole.
• said zone of least reflection is constituted by a diaphragm of variable section.
• the zone of least reflection is constituted by a semi-reflecting zone.
• the device comprises an image analyzer receiving part of the incident beam and delivering a servo signal from the mirror.
• FIG. 1 represents a view of an exemplary embodiment of the invention. This example corresponds to a situation where the source of very high luminosity is the sun, and constitutes the only source of glare.
• the device comprises a mirror (1) having a non-reflecting central zone (2).
• the image is formed on the mirror by a lens (3) whose field and magnification are determined in a known manner.
• the section of the non-reflecting area (2) is determined so as to correspond substantially to the section of the image of the glare source.
• a beam splitter (5) sends an image conforming to the unprocessed incident image to a CCD sensor (4).
• the sensor (4) delivers a signal to a computer determining the position of the center of the image of the glare source.
• the beam splitter (5) is by example constituted by a semi-transparent mirror having a very high transmission rate, so that the sensor (4) receives a light signal from the glare source compatible with its sensitivity.
• This servo signal can also be delivered by a camera (7) integral with the support of the mirror (1) and receiving an image with a constant orientation relative to the optical axis (10) of the device.
• the processed image is then directed to an eyepiece (6) for direct observation or by shooting equipment such as a camera or photographic device.
• FIG. 2 represents the optical diagram of the device described.
• the observer S (the user's eye, a camera, a photographic device or even a metrology instrument) observes a scene at infinity with an optical field Cl.
• This optical field Cl has an active area C2 in which is located the dazzling element, for example the sun.
• the observer S and the field Cl on the one hand, and the field C2 on the other hand, define two cones.
• the plane P perpendicular to the optical axis intersects the two cones.
• the intersection forms two surfaces Ccl and Cc2 which are homothetic to Cl and C2 respectively. These two surfaces are real surfaces, surface C2 being designated by "eclipsed surface”.
• a second series of cones are formed between a sensor S 'and the fields Cl and C2. The intersection with the plane P of these two cones results in surfaces respectively C'cl and C'c2; the latter surface being designated by "the dazzling surface”.
• the surface Cc2 is eliminated and replaced by an equivalent surface coming from the cone Cl.
• the sources of glare are multiple.
• FIG. 3 represents a schematic view of an alternative embodiment, for the production of a compact optical unit. It comprises an assembly of lenses and a diaphragm forming an objective (20) of the “Ed und system” type.
• the objective has a focal length of 50 millimeters and includes a doublet with a diameter of 25 millimeters, referenced M32-323 in the catalog Edmund Industrial Optics (trade name).
• the incident beam is reflected by a mirror
• a group of lenses (22) reverses the image and works in 2f-2f assembly.
• the holey mirror (23) is placed in the focal plane of the lens.
• This perforated mirror (23) is a plane mirror having a diameter of 10 millimeters and a conical bore of 1.5 millimeters in its center. It is mounted on a motorized stage along two X-Y axes perpendicular to the optical axis.
• the conical hole in the bottom of the mirror has the shape of a cone with an angle at the top between 40 ° and 60 ° and a hole with an opening between 1.2 and 2.5 millimeters.
• the movement of the holey mirror (23) is controlled by a computer as a function of the signal delivered by a CCD (charge transfer camera) matrix.
• the signal from output from this matrix is coded for each pixel on 2 bytes, the first being reserved for blue, and the second being shared between red and green.
• the computer performs threshold detection based on a fixed threshold for each of the two bytes. If a pixel has a value greater than the threshold value for one of the two bytes, the computer defines it as belonging to the zone of points Mi for forming the high intensity light spot. The computer then determines the barycenter G of this area, as well as the coordinates of the center of the area.
• the threshold can also be determined dynamically.
• the coordinates of the center of the area are used to control the movement of the positioning motors of the holey mirror. This movement can be performed pixel by pixel. In this case, the position of the hole mirror is recalculated each time the position of the center of the spot is changed. The displacement is calculated according to a reference change formula allowing to pass from the frame of reference of the image to the frame of reference of the holey mirror.
• Displacement can also be calculated within a virtual grid corresponding to a division of the image in boxes. In this case, as long as the image of the center of the bright area remains in the same box, the position of the mirror is unchanged.
• the device described in FIG. 3 also comprises a field lens (24), a deflection mirror (25) and a group of lenses (26) forming an eyepiece.
• This eyepiece has the same focal length as the objective (20).
• the holey mirror can be replaced by equivalent means, and in particular by a matrix mirror formed by a matrix of square micro mirrors with 16 micrometers per side. These micro-mirrors are mounted on actuators ensuring an orientation of ⁇ 10 °.
• the zone corresponding to the light spot is controlled so that the corresponding micro-mirrors return the light in a direction different from that corresponding to the optical axis.
• Such matrix mirrors make it possible to manage a plurality of sources of very high luminosity.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Lenses (AREA)
• Optical Elements Other Than Lenses (AREA)
• Facsimile Scanning Arrangements (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Related Child Applications (1)

Publications (1)

Family

ID=32104426

Family Applications (1)

Country Status (6)

Citations (5)

• 2002
  • 2002-11-04 FR FR0213779A patent/FR2846754B1/fr not_active Expired - Fee Related
• 2003
  • 2003-11-04 BR BR0306664-9A patent/BR0306664A/pt not_active IP Right Cessation
  • 2003-11-04 EP EP03767901A patent/EP1570302A1/fr not_active Withdrawn
  • 2003-11-04 RU RU2005112200/28A patent/RU2005112200A/ru not_active Application Discontinuation
  • 2003-11-04 AU AU2003292334A patent/AU2003292334A1/en not_active Abandoned
  • 2003-11-04 WO PCT/FR2003/003289 patent/WO2004042437A1/fr not_active Application Discontinuation

Patent Citations (5)

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