Prism system for image reversal in a visual observation path

The invention relates to a prism system for image reversal in a visual Observation beam path, which to a roof prism Base surface inclined roofline and a detected angle to the base surface Gable surface consists, on the one reflection prism is attached, said Reflection prism parallel to the base surface of the roof prism having radiation passage area.

Such a prism system is known from DE-PS 518 143, where it is as parallelsichtiges reversing prism system referred. It has only two air verging, parallel beam passage areas and six Mirror surfaces which are arranged so that all reflections in carried out a plane and are all totally reflective. The Figure beams enter the base surface of the roof prism. Of the Angle between the base surface of the roof prism and the angekitteten next reflection surface should be smaller than 110 °. Such prism systems are usually carried out at in afocal optical imaging systems, such as Telescopes used.

In recent years, are increasingly long-range optical instruments, especially Binoculars, came onto the market, the additional functions, such as Laser distance measurement or tilt and direction measurement (Compass) exhibit. The measurement results are preferably displayed so that they can be read when looking into the eyepiece. There are two possibilities, namely the display of measurement results on edge of the field outside the actual visual field or the insertion into the image field, by placing them by means of an inserted into the beam path the beam splitter superimposed on the image. This variant is known as the more ergonomically preferable as fade in at the edge of the field while reading a Twisting of the eye leads, in which the pupil of the eye from the Exit pupil of the binoculars first moved out because of Ocular pivot point is typically more than one centimeter behind the pupil lies. must therefore by parallel displacement of the binoculars the exit pupil respectively refind.

The use of a beam splitter for image overlay provides the contrast, additional option, such as application as a combined binoculars Laser Rangefinders the observation beam path for sending or Receiving the laser radiation mitzubenutzen. For the beam splitter are In addition to metallic or dielectric neutral dividers especially dichroic Divider, since the display wavelength of a display mostly the red edge of the the visible spectrum, one possible but preferably in the diode laser near infrared emitted.

There have been known various solutions, such as fade-in the Frame can be made by means of a beam splitter. DE 41 35 615 A1 it is known, either between the lens and reversing system or insert a beam splitter between inverting system and eyepiece. Uses to a simple plane plate with a corresponding mirror layer Beam splitter, as is to be expected aberrations (astigmatism). Splitter cube Mirror surface in a diagonal surface, however, are expensive and increase the Glass path. In addition, the mostly under 45 ° lead to the optical axis arranged divider layers to tint history over the image field.

Another solution is known from DE 37 04 848 C2. Here, the Expanding built right on one of three half cube prisms made erect prism, in which the radiation entry Sachse against the beam exit axis is offset in height. For insertion into the Observation beam path is at a 45 ° to the beam direction standing reflective surface of the prism reversal a beamsplitter coating applied and then cemented a semi-cube. The reflection surface is it used to pose for the picture in reflection, while the overlay carried out the display or a laser radiation in transmission. these Solution has drawbacks. On one hand, the reflecting surface is not only from the Angle of 45 ° claimed, but because of the finite aperture and the expanded image field, for example at an angle of 45 ± 5 °. this leads to especially at dichroic beam splitters to a color cast progression, over the image field and over the pupil. Also taking the reflection the beam splitter at the edge of the angular range because of the Brewster effect especially for higher-index lenses as BaK4 that today for reversing prisms Binoculars are mainly used, sharply, leading to a Brightness drop results.

The invention was therefore based on the object, a way of to provide input reflection additional beam paths, the does not affect image quality of the observation beam path and the can be realized with a low outlay on components.

This object is achieved with a prism system of the type mentioned inventively achieved in that the gable face as a beam splitter is formed and the base surface of the roof prism and the Radiation passage area of ​​the reflection prism geometrically apart separate areas for the passage of the observation beam, and for a further beam path for reflecting a measuring value in the output-side observation path and / or a Entfernungsmeßstrahlenganges in the input-side having observation beam path.

The beam splitter is preferably for the spectral range of Observation beam transmissive and for the spectral range of Measured value and the distance measurement be reflective. It is but also possible as a beam splitter metallic, dielectric or provide neutral splitter with a reflectance percentage between 10 and 40%. Optimization can also consist in the beam splitter as dichroic splitter with good transmission in the visible spectral range and good reflection in the infrared spectral form.

The inclined gable face of the roof prism to the base surface form an angle of 22.5 ° to 30 °. As reflection prism is preferably a rectangular prism is selected. In one embodiment, a can right angle forming reflecting surfaces while the gable face opposite lie. However, it is also possible for one of the reflecting surfaces at an pointing angle of 90 ° on the base surface of the roof prism Area of ​​the gable surface align. As radiation entry surface for the Observation beam is expediently the selected radiation passage area of ​​the reflection prism.

lying basis An essential step towards solving the invention Task is to select the built-up of only two pieces of glass Reversing system, which leads to a considerable cost saving. On Another important feature is that the input reflection on inversion system could be maintained, so that a separate beam splitter element deleted. However, an area is now for the input reflection used the the actual telescope beam path in transmission and not in reflection is claimed. The selected slope of the gable face of Roof prism gives a much steeper angle of incidence at the this area is traversed by the beam path, typically in a range of 60 to 67.5 degrees (corresponding to 22.5 to 30 ° to the perpendicular to these Area). This enables the design of dichroic beam splitter with much lesser tint history and uniformly high transmission in an angular range of ± 5 °. Instead of a dichroic beam splitter may also, for example, metallic neutral splitter are used. Since in most Applications, the beam splitter ratio in favor of the binocular image is selected, there is inevitably a little absorbent Splitter layer, at the same time the remaining reflection nor a appropriate input reflection of the measured value and an eye-safe Decoupling of the laser radiation is sufficient.

Embodiments of the prism system according to the invention are in the are drawing schematically illustrated below with reference to described figures. show case<dl tsize="7" compact="compact"><dt>1a</dt><dd>a first prism system with the observation beam path,</dd><dt>1b</dt><dd>the same prism system with beam path for Anzeigeneinspiegelung,</dd><dt>Fig.1c</dt><dd>the same prism system with optical path for distance measurement,</dd><dt>2a</dt><dd>a second prism system with the observation beam path,</dd><dt>2b</dt><dd>the same prism system with beam path for Anzeigeneinspiegelung,</dd><dt>2c</dt><dd>the same prism system with optical path for distance measurement, </dd><dt>Fig.3</dt><dd>the second prism system with combined Anzeigeneinspiegelung and laser beam-outcoupling.</dd></dl>

FIG. 1a shows an afocal optical system with addition to a telescope Objektiv1, Prism System 2 and 3 eyepiece a einzuspiegelnde display 4, as well as a bright object on the observed light source 5, for example, a Laserdieode, contains a transmission element of a rangefinder. The core element is the prism system 2, consisting of a roof prism 6 and a reflecting prism 7 is.

The roof edge 8 of the roof prism 6 is opposite the base surface 9 inclined. The gable face 10 is slanted. At the gable face 10 is the Reflection prism 7 is added, with its right angles to each other bumping reflecting surfaces 7 ', 7' 'of the gable area are 10 against. On the gable face 10 is a beam splitting coating 10 'applied. The two prisms are preferably cemented together. The angle between beam splitter 10 'and the optical axis 11 is 60 ° and here is chosen so that the rays entering the observation beam path perpendicular done for air / glass surface 7 'on reflection prism. 7 Of the Beam splitter 10 'is used in transmission. The arrangement shows a very low axial offset between the entering into the prism system Beam path and the eyepiece 3 exiting beam path.

Fig. 1b shows the input reflection of the display 4 in the leading to the eyepiece 3 Beam path. About a deflection mirror 12 and a display in a Intermediate image plane imaging lens 13, the imaging beam also perpendicular to the air / glass surface 9 of the roof prism 6 in the Roof prism 6 initiated. After reflection at the beam splitter 10 are ' the imaging beam to the observation beam path superimposed. The Input reflection takes place at the same base surface 9, as for the exit of Observation beam to the eyepiece 3, but in one of them geometrically separate area.

Fig. Figure 1c shows the coupling of the light source 5 into the lens-side Beam path. The beam entrance is likewise perpendicular to the air / glass surface 7 'on the reflecting prism 7, again in a range which is geometrically separated from the inlet region of the observation beam. The beam splitter 10 'is also working here in reflection. If, on the Coupling efficiency on the light source, it is the reflection for the Select question (usually located in the near infrared) wavelength high, generally leads to dichroic splitters. Nevertheless, it is conceivable also to work in this case with a (metallic) neutral splitter and a Reflection of, for example 20 to 30% sufficient find Einkoppelintensität because modern highly efficient laser diodes are to be sent out and the radiation output by the Eye safety regulations is limited anyway.

The in Fig. 2a embodiment shown to c differs from the in Fig.1 shown embodiment only in the design of Reflection prism 14, which at the gable face 10 in the area of Base surface 9 adjacent first reflection surface 14 'for the incoming Observation beam is perpendicular to the gable face 10th This results Although a larger axial offset between the lens-side and eyepiece beam paths, but this is the number of deflections in Prism system low. The choice between the two Embodiments will be governed by the available space in the long-range optical device to be set up directed.

Fig. 3 shows a variant of the FIG. 2 embodiment illustrated, are crucial for also the available space. The Display 4 is in a submitted before the light source 5 splitter mirror 15 the laser beam path is coupled. The beam splitter allows the Laser wavelength through, but reflects the display wavelength. To the Beam splitter 10 'is transmitted to the display portion wavelength and an additional concave mirror 16 again on the beam splitter 10 ' directed and time after partial reflection of the emerging Observation path superimposed. By the transmission of Beam splitter 10 'in the display wavelength (ia red) with around 50% and in the central region of the visible observation beam having about 70 to 80% is selected, can be also a useful compromise for sufficient display representation found in the image field.

Additionally shown is a recording beam path for the observed Object measuring radiation reflected from which a Distanzmeßsignal recovered and placed on the display 4 for displaying. Of the Recording beam path consists of a lens 17 and a Receiving diode 18 and is generally parallel to the Observation beam path aligned.

Of course, in addition to the recording beam path for the Distance measurement, a separate transmission beam path be provided. In this case is omitted in Fig. 3, the light source 5 and the display 4 can also without going through the beam splitter 15 in the prism system and further in the observation beam path are introduced.