EP1509812B1 - Method and arrangement used to photographically capture a vehicle - Google Patents

Abstract

The invention relates to a method and an arrangement which are used to photographically capture a vehicle, in which an image document (front photo) is provided and is suitable for identifying both the driver and the number plate in a clear and manipulation-free manner. One single synchronous capture occurs in order to produce two geometrically identical offset images having different intensities in an offset manner on the recording medium which can be both a wet-type film and an electronic sensor arrangement. The arrangement is advantageously made of a traditional recording device which is used for photographing the vehicle and an objective lens.

Description

The invention relates to a method and an arrangement for the photographic recording of a vehicle, with which an image document (front photo) is created, which is suitable to identify both the driver and the license plate clearly and tamper-proof.

In order to obtain a legally usable document in accordance with German law with traffic photography, in addition to a manipulation-free and unambiguous assignment of recorded data such as speed, direction of travel, location, date and time to the front photo, the vehicle driver and license plate must be clearly recognizable. A legally unambiguous assignment of driver to license plate is always given when the front photo is generated with a single shot. However, this results in lighting problems that lead both in the wet film technology, but more when using digital technology, as a recording medium to a high proportion of non-usable front photos.

In order to even allow a picture of the driver, the passenger compartment and thus the driver must be sufficiently illuminated. This is independent of daylight in a distance range of the vehicle from the recording device usually between 30 m and 12 m and at a vehicle speed of up to 250 km / h only with an additional flash light possible. To make matters worse, there is often an optical coloring of the windshields, which additionally reduces the intensity of the radiation, which in any case is slightly reflected by the vehicle driver.
The retroreflective characteristic, on the other hand, reflects the radiation almost 100%.
D. h on the one hand, it is endeavored to record the vehicle at the smallest possible angle, so to direct the recording device frontally on the windshield to capture as much of the reflected radiation from the driver with the recording device, on the other hand, the largest possible angle would be low, so only a small amount of radiation reflected by the license plate is detected.

Additional factors influencing the respective recording situation are the constantly changing light conditions, the recording of the vehicles on different lanes and the changing meteorological influences.

The photometric extremes arising in real conditions, location-dependent on a vehicle to be recorded (dimly lit vehicle interior and overexposed license plate) and their change in successive objects to be recorded (change in daylight, change of lane u.s.w.) make very high demands on the dynamics of the recording medium.

Due to the much higher resolution and the much greater dynamics (2 ¹⁴ gray levels per pixel), the wet film is still preferred in traffic photography. Extremely differently illuminated pixels can be processed by elaborate rework when developing the film within certain limits, so that the image information is visible.

This is far less successful in the digital recording technique due to the still poorer resolution and the significantly lower dynamics (2 ¹⁰ gray levels per pixel). While the image of the driver in the dimly lit interior of the passenger compartment requires high sensitivity and resolution, the overexposed characteristic requires very high dynamics and oversteer stability.

In addition to the constant effort to improve the physics of the recording media, attempts to solve the problems highlighted in traffic photography either by improvements in the evaluation of image information, which represents an electronic solution for digital technology or attempts by optical solutions, the image of the object to influence.

DE 35 35 588 A1 discloses a method and a device for photographing strongly illuminated or reflecting parts of a field of view to be photographed. For example, a retroreflective mark of a Vehicle together with the other, normally lit parts of the field of view to be able to take photographs, a light-attenuating filter is applied in the image plane of the camera, which extends across the image plane. The brightness of the image is attenuated in the area covered by the filter. In order to obtain a photograph in which the radiation reflected by the license plate is being attenuated by the filter, the image of the license plate must arise in the area of the filter. That means the camera has to be very precisely aligned with the vehicle.

In DE 198 02 811 A1 is spoken by an improved identification of the driver and the license plate by a larger number of images and using a contrast method. However, no further details are provided.

DE 297 18 274 U1 discloses a camera recorder for speed measuring devices, which is distinguished by a graduated filter set in front of the objective. This semi-colored filter with a smooth transition from the dark to the bright part is used in such a way that the darker part attenuates in particular the reflection of the mark. However, the locally differentiated attenuation can only be completely inadequate until it does not act when the filter is near or in the entrance pupil of the objective.

In addition to the previously shown optical solutions in which the reflected radiation of the mark is all attenuated, EP 0621 572 A1 proposes a method and a device in which two different image sections of a traffic scene are simultaneously recorded with two digital cameras at a different angle. The electronic image data of both images are stored together for evidence security. Although the introductory problem of greatly differing reflection of different object sections is not explicitly presented here as a problem to be solved, it is obvious that the indicator, when recorded at an angle greater than the angle of the retroreflection, no longer outshines, while the faint scenery was taken at a rather small angle becomes. Such a solution requires only by the need of two cameras (recording devices) a high technical effort and a high outlay for installation on site.

While the optical solutions influence the imaging of the object, the electronic solutions, of which two are to be mentioned below, concern the evaluation of the digital image data.

DE 199 60 888 A1 describes a method and a device in which at least two images of different brightness are generated from the image data of a photograph. For this purpose, the first 8 bits of the CCD sensor, which contain more usable information about the light content, are read out as a dark image, which makes it easier to identify the very bright radiating license plate. The last 8 bits of the sensor generate the bright image, which contains more usable information about the dark portion of the image and thus driver. Advantageously, these two digital images should be combined with each other so that an image is formed on which you can recognize both the license plate and the driver at least better. Whether the recognizability of the license plate in any case is given, seems doubtful.

A second interesting electronic solution is disclosed in DE 100 29 578 A1. With the method described here, the exposure of the license plate and the exposure of the passenger compartment can be treated separately when determining a target value (desired exposure of the object). This way, images optimized for the brightness of the passenger compartment and images optimized for the brightness of the license plate can be generated, which of course requires at least two shots.

The state of the art can be summarized as follows. None of the solutions outlined sufficiently ensure both the recognizability of the vehicle driver and the license plate with a single image of a vehicle, regardless of the recording medium.

It is the object of the invention to provide a method and a device that creates an image document with a single photographic image, on which, regardless of the objective lighting conditions and the recording medium, both the vehicle driver and the license plate are clearly visually recognizable.
The device according to the invention should advantageously be able to be created by retrofitting commercially available recording devices for traffic photography. Preferably, this retrofitting should be possible without intervention in the hardware of the recording device and without a necessary adjustment to the recording device by the user. By retrofitting the recording device, the working regime (eg triggering the recording and the flash, performance of the flash, reading, saving and evaluating the image information) of the recording device should not be affected. The user should not change the handling.

The object of the invention is achieved for a method according to the preamble of claim 1 in that the imaging beam bundle reflected by the vehicle and causing the image is split into two partial beams, the first partial beam having only an insensitely lower light intensity than that of the entire imaging beam, generates a first image on which the driver is clearly visible, while the second partial beam with a light intensity of less than 5% than that of the entire imaging beam, generates a second image on which the license plate is clearly visible and that the two geometrically identical images on the Recording medium to each other at the same time, spatially offset generated and stored.

For an arrangement according to the preamble of claim 2, the object is achieved in that in the beam path of the imaging beam means are provided for dividing the imaging beam into two mutually offset partial beams of different intensity, on the recording medium two geometrically identical images of different intensity effect with a local offset to each other wherein the first partial beam with an imperceptibly lower light intensity than that of the entire imaging beam generates a first image, while the second partial beam with a light intensity less than 5% than that of the entire imaging beam generates a second image, so that the first Image of the driver and the second image the license plate well lit and recognizable maps.

Advantageous embodiments of an inventive arrangement are listed in the subclaims 3 to 8.

The essence of the method according to the invention is that with a single image of an object field, two geometrically identical images of the object field on the same recording medium are generated offset from each other. It is essential to the invention that the second image is generated with a very low light intensity, less than 5%, preferably less than 1%, while for the first image as far as possible the remaining light intensity, which can be up to greater than 99% of the incident radiation in the lens can, is used.
The first image, only imperceptibly lower in light intensity compared to the image with full light intensity, reflects the full object field, whereby as in conventional photographs of the driver in the passenger compartment illuminated by the flashlight is easily visible and the highly reflective indicator often appears only as an overridden light spot. Below the vehicle, which is practically always on a quasi-homogeneous low-contrast road surface, arises on the first image, a low-contrast area.
The second image, on the other hand, is almost completely dark due to the low light intensity, except for the license plate, which is optimally exposed here.
The two images (double images) are offset relative to one another in such a way that the mark which can be recognized in the second image is imaged onto the recording medium to where the low-contrast regions from the first image are imaged without usable image information. Preferably, the area below the vehicle is used here.
Practical experiments have shown that, especially when using electronic recording media (CCD sensor) due to the low dynamics no ghosting. The usable image information of the second image (only the flag) is projected onto an area of the first image in which no usable image information (only road surface) is present.
The image information of both images are simultaneously stored and processed as a single image. Likewise, a wet film used as a recording medium undergoes one-time exposure as just described for a CCD sensor.

Vehicle drivers and license plates are legally recorded clearly and manipulation-proof with the identical imaging optics and stored in an overall image or a data record. About the knowledge about the offset of the images, defined by the device-technical arrangement, at least for the electronic recording medium and a data-like resolution of the overall picture in the first and second image possible and therefore clearly assignable.
Decisive for the ratio of the light intensity to be implemented for the two images is the amount of light with which the indicator is optimally imaged. Since this ratio is device-technically feasible and thus the second image determining amount of light very small, even less than 1% can be selected, there is the principle possibility regardless of the traffic-technical possibilities to direct the recording device frontally on the vehicle.
In contrast to the solutions shown in the prior art, which attempt with only modest success by optical attenuation to solve the problem of the overexposed mark, here is the total incident in the lens amount of light for the generation of the image (here consisting of two overlapping Images).

1. 1. Erzeugung eines Abbildungsstrahlenbündels
2. 2. Auftrennen des Abbildungsstrahlenbündels in zwei Teilstrahlenbündel unter einem bestimmten Lichtintensitätsverhältnis (zur Erzeugung von zwei geometrisch identischen Abbildern unterschiedlicher Intensität)
3. 3. Erzeugung eines optischen Versatzes zwischen den Abbildern
4. 4. Abbildung der beiden Abbilder und Speicherung der Bilddaten

An apparatus suitable for carrying out the method must identify means which fulfill the following subfunctions:

1. 1. Generation of an imaging beam
2. 2. Separating the imaging beam into two partial beams under a certain light intensity ratio (to produce two geometrically identical images of different intensity)
3. 3. Creation of an optical offset between the images
4. 4. Illustration of the two images and storage of the image data

It is clear to the person skilled in the art that the individual subfunctions can be practically fulfilled by different but also the same technical means. Likewise, individual subfunctions can be fulfilled by the interaction of several technical means. From the large number of usable concrete technical means and their arrangement to each other, a variety of arrangement variants can be generated. All arrangement variants basically consist of a lens (means for generating an imaging beam), a recording medium, such as a wet film (chemical storage) or an electronic sensor arrangement (electronic storage) arranged in the image plane of the lens (means for imaging the two images and storing the image data ) and means for dividing the imaging beam and for offsetting the resulting partial beams.
The means for dividing the imaging beam and for the offset of the resulting partial beams differs for the individual performance variants essentially by the physical principle realized by them, the resulting concrete technical realization and their arrangement within the arrangement variant.

In principle, these means can be arranged in front of the objective, inside the objective or between the objective and the recording medium.
Assuming that the object to be imaged (vehicle is always in a distance virtually infinite to the lens), the imaging beam between object and lens is a parallel beam.

For retrofitting recording devices already on the market, the introduction of these means, which cause optical processing of the beam, in particular in front of the lens in question. The additional introduction of optically active means within the lens or between the lens and the recording medium is basically possible only in a redesign of a recording device, as these additional optical means in the calculation of the optical system of the recording device, determined by the taking lens and the recording medium, observed Need to become. Those skilled in the art, knowing the present description, will be able to apply such solutions equivalent to new designs.

Regardless of their arrangement, the means for separating the beam may be based on physical beam splitting eg with a splitter cube, a prism, a coated splitter plate or a Fresnel splitter plate, as well as on geometric beam splitting by pupil division with fixed or variable division ratio.
The offset of the partial beams can be effected by an image angle offset, for example with a wedge, a rotary wedge pair, a prism or an angle mirror (fixed or variable) or a parallel beam offset, for example with a plane plate (fixed or variable).
All of these specific technical means as well as others which are suitable instead are known to the person skilled in the art.

Fig. 1a:

erstes Ausführungsbeispiel als Schnittdarstellung in Seitenansicht

Fig. 1b:

Ausführungsbeispiel nach Fig. 1a in Draufsicht

Fig. 2:

Objektivvorsatz für ein zweites Ausführungsbeispiel als Schnittdarstellung in Seitenansicht

Fig. 3:

Objektivvorsatz für ein drittes Ausführungsbeispiel als Schnittdarstellung in Seitenansicht

Fig. 4a:

Objektivvorsatz für ein viertes Ausführungsbeispiel als Schnittdarstellung in Seitenansicht

Fig. 4b:

Objektivvorsatz nach Fig. 4a in Schnittdarstellung (IVb-IVb) in der Drehwinkelstellung ϕ = 0° zum Objektiv

Fig. 4c:

Objektivvorsatz nach Fig. 4a in Schnittdarstellung (IVb-IVb) in der Drehwinkelstellung ϕ = 45° zum Objektiv

Fig. 4d:

Objektivvorsatz nach Fig. 4a in Schnittdarstellung (IVb-IVb) in der Drehwinkelstellung ϕ = 90° zum Objektiv

Fig. 5:

Objektivvorsatz für ein fünftes Ausführungsbeispiel als Schnittdarstellung in Seitenansicht

Below some advantageous embodiments will be explained in more detail with reference to a drawing. Show:

Fig. 1a:

first embodiment as a sectional view in side view

Fig. 1b:

Embodiment of FIG. 1a in plan view

Fig. 2:

Lens attachment for a second embodiment as a sectional view in side view

3:

Lens attachment for a third embodiment as a sectional view in side view

Fig. 4a:

Lens attachment for a fourth embodiment as a sectional view in side view

Fig. 4b:

Lens attachment according to Fig. 4a in a sectional view (IVb-IVb) in the angular position φ = 0 ° to the lens

4c:

Lens attachment according to Fig. 4a in a sectional view (IVb-IVb) in the angular position φ = 45 ° to the lens

4d:

Lens attachment according to Fig. 4a in a sectional view (IVb-IVb) in the angular position φ = 90 ° to the lens

Fig. 5:

Lens attachment for a fifth embodiment as a sectional view in side view

Since, as already explained in detail, the optical processing is particularly advantageous in the parallel beam path in front of the lens 1, describe all subsequent embodiments arrangements consisting of a recording device 4 with a lens 1, a recording medium 2 in the image plane of the lens 1, which is both a wet film The objective lens 3 is constructed differently for the individual embodiments, in particular, the individual embodiments comprise different concrete technical means for processing the beam integrated in the lens attachment. 3

A first embodiment is shown in FIGS. 1a and 1b.
Shown is a recording device 4, of the stylized housing parts shown only necessary for the understanding of the invention assemblies, namely the lens 1 and the recording medium 2 are shown. The lens attachment 3 is screwed over an existing on the recording device 4 lens filter thread 5 via an outer ring 6. In a, in the outer ring 6 fitted retaining ring 7, a circular segment-shaped optical wedge 8 is fixed at an angle α. It is clear to those skilled in the art that the outer ring 6 shown here, alone so that the retaining ring 7 can be inserted, is at least a two-part assembly. It should be stressed again that the representations in The drawings have been reduced to the essentials in order to clearly present the principle solutions.
Through the wedge 8, the pupil opening 9 is geometrically divided into two sub-areas, while the division ratio and the resulting intensity distribution for the two resulting partial beams of the dimensioning of the wedge surface 10 is determined. The retaining ring 7 is rotatably mounted in the outer ring 6 and can be adjusted by the operator by means of a hole key engaging in holes 12 so that an exactly vertical offset of the second image, which is formed by the partial beam extending through the wedge 8, relative to the first image which is created by the uninfluenced partial beam. The offset is determined by the wedge deflection angle σ1 = α (n-1), where α is the angle of the wedge 8 and n is the refractive index of the wedge 8.

The image location 13 of the first partial beam, which passes unchanged through the remaining free surface 11 of the pupil opening 9, arises as usual on the optical axis of the lens 1 in the plane of the recording medium 2. The passing through the wedge 8 second partial beam strikes at the Keilablenkwinkel σ ₁ on the lens 1 and is so offset to the optical axis on the recording medium 2 imaged (image location 14 of the second partial beam). The lens attachment 3 has on its front side facing away from the lens 1 a thread of the same dimensions as the lens filter thread 5. Thus, all existing conventional filter attachments can continue to be used. For stationary systems, it makes sense to predetermine and adjust both the position of the wedge 8 and the wedge surfaces 10. An extension of the arrangement according to the invention would be a mechanical displacement unit which makes the wedge 8 displaceable in the radial direction. Thus, especially in mobile and mobile-stationary facilities, an optimization of the brightness of the second image of the current lighting situation could be performed.

In Fig. 2, a lens attachment 3 is shown for a second embodiment. This lens attachment 3 is mounted analogously to the first embodiment of a recording device 4.

In contrast to the first embodiment, a plan plate pair 15 is provided here as an optical means, which encloses a fixed angle α enclosing in the retaining ring 7. The flat plate pair 15 represents an angle mirror with a fixed angle. The ray bundle entering the pupil is transformed into a passing and entering surface according to Fresnel's laws on the surface of the plane plates, which each represent an optical interface (glass - air or air - glass) split partial beam reflected. The penetrating partial beam is within the meaning of the invention the first partial beam, which is used for visible imaging of the driver, while the reflected partial beam is the second partial beam, which is provided in the description of the invention consistently for the visible imaging of the license plate.
If these interfaces are not optically antireflective, approximately 4% of the radiation intensity is reflected on each surface (in the case of vertical penetration). Thus, the directly penetrating, first partial beam has an intensity of about 85% of the beam entering the pupil. The beam portion reflected twice on the facing surfaces of the plane plates forms the second partial beam with an intensity of about 1.5% and leaves the plane plate pair 15 at an angular offset equal to the mirror angle deflection σ ₂ = 2α to the optical axis. The remainder of the radiation is essentially lost by the reflection at the first interface. The division ratio can be arbitrarily influenced by targeted optical compensation of the interfaces.
Also in this second embodiment, the direction in which the second image is offset, be determined by turning the retaining ring 7.

According to the same principle as the second embodiment, the third embodiment, which is shown in Fig. 3 works.
In contrast to the second embodiment, the angular offset is equal to the mirror angle deflection σ ₂ variably adjustable by the angle α between the one
Planplattenpaar 15 forming thin glass plates can be varied by an angular range α.
By means of an introduced into the retaining ring 7 screw 16, one of the two flat plates can be tilted against the other variable by the angular range Δα.

The set angle α, can be read on the drum of the adjusting screw 16.
The possibility of changing the angular offset may prove useful in mobile stations, in order to be able to adjust the image offset of the image of the indicator of the imaged vehicle size at different recording distances (about 10 to 25 m).
The fourth embodiment is characterized in that it allows a structurally simple way to vary the intensity ratio, without changing the vertical image offset. Such a solution would be particularly advantageous for mobile devices that should be easily and quickly aligned to different lanes. As already explained, the incidence of the radiation reflected by the license plate is very dependent on the viewing angle at which the vehicle is imaged.

A fourth exemplary embodiment is shown in FIGS. 4a to 4c.
The retaining ring 7 is rotatably mounted to the outer ring 6 and thus to the recording device 4. In the retaining ring 7 is radially aligned with the optical axis a self-aligning ball bearing 17. On the inner ring of the self-aligning ball bearing 17, a gravity pendulum 18 is suspended, to which a wedge 8 is mounted in such a way that the angle α is always in the vertical direction, so that the beam deflection always takes place in the vertical direction.
If the retaining ring 7 is rotated from the zero position shown in FIGS. 4a and 4b to the right or left, the gravity pendulum 18 and thus the wedge 8 continuously pivots out of the beam path of the objective 1. The ratio between the part located in the beam path changes the wedge surface 10 to the free surface 11. Without affecting the offset of the second figure to the first, the intensity of the second image can be continuously reduced to zero and of course also increased again. 4c and 4d show the position of the gravity pendulum 18 at a rotation of the retaining ring 7 relative to the zero position by 45 or 90 °.

In Figure 5, a fifth, particularly suitable for mass production embodiment is shown. Compared with the embodiments shown so far, this fifth embodiment can be produced particularly cheaply by its simplest construction with the lowest means and assembly costs.
The objective 3 is reduced here to the outer ring 6 and the wedge 8 and is attached to the lens 1. The wedge 8 extends over the entire pupil opening 9, whereby, in contrast to the previously considered embodiments with wedge 8, the entire imaging beam passes through the wedge 8. The two partial beams are formed on the one hand by the refraction at the exit from the wedge 8 and by the two-fold reflection in the wedge 8. Both partial beams are deflected here by an angular offset to the optical axis. The first partial beam is deflected by refraction about the wedge deflection angle σ _{1 =} α (n-1) and the second partial beam is deflected by reflection by the mirror angle deflection σ ₂ = 2α. The angle α is equal to the wedges 8 of the other embodiments, an angle to a perpendicular to the optical axis, ie, the entrance surface of the wedge 8 is perpendicular to the optical axis, while the exit surface is inclined relative to this perpendicular by the angle α.

List of used reference numbers

1

lens

2

recording media

3

conversion lens

4

recording apparatus

5

Lens filter thread

6

outer ring

7

retaining ring

8th

wedge

9

pupil opening

10

wedge surface

11

free area

12

hole

13

Image location of the first partial beam

14

Image location of the second partial beam

15

Plane plate pair

16

screw

17

Aligning ball bearings

18

Gravity pendulum

angle of rotation

φ

angle

α

refractive index

n

Keilablenkwinkel

σ ₁

Mirror angular deflection

σ ₂

Claims (8)

1. A method for photographic recording of a vehicle, wherein a flashlight is directed on said vehicle during imaging of the vehicle onto a recording medium (2), characterised in that
   the imaging ray bundle causing said imaging and being reflected by the vehicle is split into two partial ray bundles, wherein the first partial ray bundle having an only imperceptibly lower light intensity than the total imaging ray bundle generates a first image in which the driver of the vehicle is well recognisable, while the second partial ray bundle having a light intensity of less than 5% of that of the total imaging ray bundle generates a second image in which the license plate is well recognisable, and in that the two geometrically identical images are generated and stored on the recording medium (2) at the same time, but locally displaced.
2. An assembly for photographic recording of a vehicle, comprising a camera (4) consisting of a lens (1) for generating an imaging ray bundle and of a recording medium (2) in the image plane of the lens (1), characterised in that
   the beam path of the imaging ray bundle has means for splitting the imaging ray bundle into two partial ray bundles displaced relative to each other and having different intensities, said ray bundles resulting in two geometrically identical images on the recording medium (2), which images have different intensities and are locally displaced relative to each other, wherein the first partial ray bundle having an only imperceptibly lower light intensity than the total imaging ray bundle generates a first image, while the second partial ray bundle having a light intensity of less than 5% of that of the total imaging ray bundle generates a second image, such that the first image depicts the driver of the vehicle and the second image shows the license plate, well illuminated and recognisable.
3. The assembly according to claim 2, characterised in that
   said means are arranged preceding the lens (1) in the imaging direction as part of a lens attachment (3) in the beam path of the imaging ray bundle.
4. The assembly according to claim 2 or 3, characterised in that
   said means are a pair of plane plates (15) enclosing an angle (α) between them such that, by physical beam splitting, the radiation component which is guided along the surfaces of the plane plates by reflection forms the first partial ray bundle and the radiation component which passes through forms the second partial ray bundle, and the first partial ray bundle is deflected relative to the optical axis with an angular displacement equal to the mirror angle deflection σ₂=2α.
5. The assembly according to claim 3 or 4, characterised in that
   the means used is a wedge (8) with a refractive index (n) and an angle (α) is used, which wedge (8) extends into the imaging beam path and which, by means of geometrical beam splitting, deflects that radiation component which is incident on the wedge surface (10) that extends into the imaging beam path, said radiation component being deflected as the second partial ray bundle with an angular displacement equal to the wedge deflection angle σ_{1 =} α (n-1), and which wedge (8) leaves the radiation component not passing through the wedge surface (10) uninfluenced as the first partial ray bundle.
6. The assembly according to claim 5, characterised in that
   wedge surface (10) is movable in and out of the imaging beam path, thereby varying the optically active surface of the wedge surface (10), which results in a change in the intensity, in particular of the second partial ray bundle.
7. The assembly according to claim 3 or 4, characterised in that
   the means used is a wedge (8) with the refractive index (n) and an angle (α), which wedge (8), by physical beam splitting, deflects the first partial ray bundle with an angular displacement equal to the wedge deflection angle σ₁₌ α (n-1) relative to the optical axis by means of diffraction and deflects the second partial ray bundle with an angular displacement equal to the mirror angle deflection σ₂= 2α relative to the optical axis by means of reflection.
8. The assembly according to claim 2, characterised in that
   an external thread is present on the side of the lens attachment (3) facing towards the lens (1), by which external thread the lens attachment (3) is connected to a lens filter thread (5) present on the lens (1), and in that an internal thread identical with the lens filter thread (5) is present on the side facing away from the lens (1), said internal thread enabling additional mounting of a filter.

Images