GB2024558A

GB2024558A - Laser Range Finder

Info

Publication number: GB2024558A
Application number: GB7920802A
Authority: GB
Original assignee: Bofors AB
Current assignee: Saab Bofors AB
Priority date: 1978-06-22
Filing date: 1979-06-14
Publication date: 1980-01-09
Also published as: SE7807159L; DE2924478A1; NO792082L

Abstract

The invention provides a laser range finder comprising an aiming telescope and laser transmitter and receiver parts, complete with electronics and optical systems, for measuring the range of an object observed through the aiming telescope, characterized in that the aiming telescope 1 is housed in a unit 16 which is releasably connected to a separate laser unit 10 housing a laser transmitter and detector, and the electronic system therefor, whereby the two units are separable for exchange of the laser unit, there being means 9 for passing laser radiation reflected from the object and incident on the aiming telescope to the detector in the laser unit when the aiming telescope and laser unit are connected together. <IMAGE>

Description

SPECIFICATION Laser Range Finder The present invention relates to a laser range finder comprising an aiming telescope and laser transmitter and receiver parts, complete with electonics and optical systems, for measuring the range of an object observed through the aiming telescope.

For determining the range of an object, it is previously known to use laser range finders in which the time for a laser beam to be transmitted from the range finder and reflected back by the object is measured.

Laser range finders are primarily used for military purposes, when the range of a target is to be determined. In order to facilitate the aiming of the range finder at a distant target it is previously known to furnish the range finder with a sighting device, for instance an aiming telescope, with the aid of which an operator can aim the range finder at the target. As a rule, the aiming telescope and the receiver part of the range finder have previously been built together into one unit, so that a common objective and prisms, if any, are utilized for both aiming and receiving of laser pulses. A dichroic (selective) mirror is then used to reflect the radiation within the visible wavelength range to the ocular of the aiming telescope, while the laser radiation is transmitted to the detector of the receiver part.An example of such a laser range finder is shown in the Swedish Patent Specification No. 362,146.

However, these previously known instruments have a number of disadvantages: 1. The range finders are, at present at least, very expensive.

2. Certain military instruments contain complicated telescopes, and for tactical reasons it is desirable to provide only part of these with range finders.

3. Failures occur in the eiectronic and very complicated part of the laser range finder considerably more often than in the strictly optical part. It is therefore desirable that a faulty unit can he exchanged without the entire equipment being rendered inoperative.

4. As the dimensions, weight and powder requirements of future lasers can be expected to be reduced considerably, it would be an advantage if the instrument could subsequently be complemented with a new laser unit without altogether too extensive changes being involved.

This is not possible with present laser range finders.

The present invention has been made from a consideration of the above noted disadvantages of prior laser range finders.

In accordance with this invention there is provided a laser range finder comprising an aiming telescope and laser transmitter and receiver parts, complete with electronics and optical systems, for measuring the range of an object observed through the aiming telescope, characterized in that the aiming telescope is housed in a unit which is releasably connected to a separate laser unit housing a laser transmitter and detector, and the electronic system therefor, whereby the two units are separable for exchange of the laser unit. Usually, there are also means, such as registering windows, for passing laser radiation reflected from the object and incident on the aiming telescope to the detector in the laser unit when the aiming telescope and laser unit are connected together.

The invention will now be described in more detail, with reference to the accompanying drawings in which: Figures 1 and 2 show schematically an embodiment of the invention.

The laser range finder shown in Figure 1 comprises a telescope 1 which, for instance, can be of the kind which otherwise is intended for a prismatic compass or a military theodolite. The telescope comprises an objective part 2, which guides the incident radiation, both radiation within the visible wavelength range and laser radiation, towards a prism arrangement in the rear part of the telescope. Further, the telescope comprises an ocular 4 provided with an aiming mark 5 to facilitate aiming of the instrument by the operator at the object, for example a target which is to be attacked in the case of military equipment.

The prism arrangement comprises a reversing prism 3 and a reflecting surface on which is glued a prism 6 to which a dichroic (selective) mirror coating 7 is applied. The dichroic mirror coating has such properties that it reflects all visible beams into the ocular 4 of the telescope, while laser beams are let through the coating into a receiver diaphragm aperture 8, after which they pass out of the telescope through a window 9 in the wall of the telescope.

In addition to the telescope 1, the laser range finder comprises a laser unit 10 with a trasmitter part, which in a conventional way contains flash lamp, laser rod 11, transmitter optics 12, etc.

which are required for transmission of a laser beam. Further, the laser unit comprises the electronics required for he range finder and a display 1 3 (presentation means) to present the measured range to the operator. However, these parts are of conventional design, and will therefore not be described in detail.

best seen in Figure 2, the transmitter part is enclosed in a casing 14 which comprises a lower, tubular part 15, arranged to be mounted on the tube 1 6 of the telescope objective, and secured so that the optical axis of the laser transmitter will be parallel to the optical axis of the telescope. The alignment will thereby be practically maintained if the laser unit is exchanged. Further, the bottom of the casing of the laser transmitter is provided with a window 1 7 towards the rear, which in the secured position is located directly over the window,9 in the wall of the telescope.

In addition to the transmitter part, the laser unit also comprises a detector 18 which receives the laser radiation reflected from the target through the windows 9 and 17, and in a known way converts this into an electrical signal.

For the connection of the telescope part together with the laser part, it can be an advantage to reproduce the receiver diaphragm aperture 8 at an infinite distance by means of a lens placed in the telescope part and thereafter to reproduce the aperture on the detector with a lens in the laser unit.

The advantages of the device described will be obvious. In particular, it permits ready replacement of the laser unit, either because there is a defect in this unit, or even to fit the range finder with a cheaper, smaller and lighter laser unit which has become available. All that has to be done is to open the lock securing the laser unit to the telescope and the laser unit can then be replaced by another one.

In the example of an ambodiment according to Figures 1 and 2, the telescope belonging to a prismatic compass was used. If such an instrument is provided with a range finder, it can be used as an observation and measuring telescope.

In cases when the telescope, when firing, is used without a laser range finder, it can be provided with an aiming scale. A device which converts range into tangent elevation and possibly also into aim-off should then be used.

In Figures 1 and 2, the laser unit is shown provided with a display (presentation means) 1 3.

However, it is also possible to instead have the aiming telescope provided with a presentation unit, and the instrument is then provided with a contact device for transmitting signals to the presentation unit from the electronics of the laser unit.

Claims

1. A laser range finder comprising an aiming telescope and laser transmitter and receiver parts, compiete with electronics and optical systems, for measuring the range of an object observed through the aiming telescope, characterized in that the aiming telescope is housed in a unit which is releasably connected to a separate laser unit housing a laser transmitter and detector, and the electronic system therefor, whereby the two units are separable for exchange of the laser unit.

2. A laser range finder according to Claim 1, wherein the aiming telescope contains a selective mirror to separate the laser radiation from the radiation incident through the objective of the telescope, and a receiver diaphragm for the laser radiation.

3. A laser range finder according to Claim 2, wherein the selective mirror consists of a selective mirror coating on a prism comprised in a prism arrangement in the rear part of the aiming telescope.

4. A laser range finder according to any preceding claim, wherein the laser unit comprises a tubular part adapted to be mounted on the tube of the telescope objective and secured in the mounted position.

5. A laser range finder according to Claim 4, wherein the casing of the laser unit is provided with a window which, when the laser unit is secured to the telescope, is placed directly above a corresponding window in the casing of the telescope, so that the laser radiation received through the objective of the aiming telescope can pass from the aiming telescope into a detector positioned in the rear part of the laser unit.

6. A laser range finder according to any preceding claim, wherein the laser unit comprises a presentation unit for presenting the measured range to an operator.

7. A laser range finder according to any one of Claims 1 to 5, wherein the aiming telescope has a presentation unit to present the measured range to an operator and contact devices for transmitting signals to the presentation unit from the laser unit.

8. A laser range finder according to Claim 1 and substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.