WO2006041386A1

WO2006041386A1 - The device offers a means for automatic calibration of an optical sight for firearms, by firing one round only

Info

Publication number: WO2006041386A1
Application number: PCT/SE2005/001488
Authority: WO
Inventors: Gert I. Johansson; Göran M. BACKLUND
Original assignee: Johansson Gert I; Backlund Goeran M
Priority date: 2004-10-13
Filing date: 2005-10-10
Publication date: 2006-04-20
Also published as: EP1856471A1; US20100251593A1; SE526742C2; SE0402472L; SE0402472D0; ES2431612T3; EP1856471A4; EP1856471B1

Abstract

This patent defines a device for automatic calibration of optical sights for firearms . Only one shot has to be fired to achieve this. The device can be integrated with an optical sight or fitted as a separate unit mounted on the sight. The device consists of a digital camera (e.g. CCD), some kind of beam splitter, a microprocessor including a memory for camera images and computer software, servo motors including a gear mechanism, an electrical switch, light emitting diodes and a shot detecting sensor. In the digital sight application, the device also includes a display unit while servo motors, gear mechanism, light emitting diodes and beam splitter are excluded. The calibration procedure: involves firing a round at a target consisting of a rectangular white surfaceon a dark background at the chosen range. The camera saves the last image immediately before the firing moment and compares the cross-hairs position with that of a following image from which the projectile point of impact can be found. After calculations, the position of the cross-hairs is adjusted by servomotors to align with the detected projectile impact point position. In the digital sight application, the cross-hairs is simply 'drawn' at the new correct location on the display. The weapon and the optical sight is now calibrated at the chosen range.

Description

Technical domain

The device offers a means for automatic calibration of an optical sight for firearms, by firing one round only.

Technical standpoint

To zero-in, or calibrate, a firearm equipped with an optical sight, typically a riflescope, is usually a tedious and to some extent error prone procedure. Several rounds are usually needed for a successful calibration. Hunters then usually fire a couple of high priced soft point rounds to confirm the calibration.

The device described in this application offers shooters the possibility of getting the optical sight (riflescope) automatically calibrated, by firing one round only, at a defined target.

Description of the invention

To achieve an automatic calibration of an optical sight for firearms, a traditional optical sight needs the following additional items, se Figure 1. A beam-splitter (1) lets the shooter and the image processing system view the same scene. The image is fed into a camera (2) (e.g. a CCD camera) for registration. A micro-processor with sufficient memory and software (3) analyzes the image and determines the error (i.e. calculates the need for calibration). Servo motors (4) with gears (5) can be used to operate the adjustment screws and the traditional mechanical cross-hair element (9). A switch is used to initiate the automatic calibration sequence (6). Lamps (8) (e.g. diodes) indicate the calibration result. The device is powered by a built-in or external electrical power source (7).

By cross-hairs is meant all existing variants of optical sights.

The calibration sequence is described by the following instruction to the shooter:

- Arrange a target (typically: a white square surface against a dark background) and assume firing position at the range for which the firearm is to be calibrated.

- Initiate the calibrating function by pressing the switch.

- Aim & fire a round at the target.

- After firing the round, aim again at the target and identify the bullet hole visually.

- Hold the cross-hairs steady at the target, when the green lamp lights up - the calibration is successful. If the red lamp lights up, repeat the sequence.

- The calibrating function is shut off by pressing the switch again.

Function: When the calibration procedure is initiated by the switch, the microprocessor and camera start up. The camera immediately starts taking frames (with a typical interval between frames of 40 ms) and stores them in a FIFO queue (First hi , First Out).

The microprocessor detects that a round has been fired when the target suddenly disappears from the view (it happens very fast; i.e. from one frame to the other). Alternatively an embedded sensor can be used to register this event.

The last exposure before the shot is stored for later analysis; the edges of the white target area are identified by contrast with the darker background. After firing the round, the shooter resumes the aiming position while the camera continues to take frames and to store them in the FIFO queue. The best frame after firing is identified and is then compared with the best frame before firing. The bullet hole position on the target is identified by variation in contrast (black dot on the white surface).

While the shooter holds the cross-hairs on the target, the microprocessor calculates the needed adjustment. This means both horizontal and vertical adjustments in "clicks", to align the bullet hole with the cross-hairs . Since the cross-hairs position is determined relative to the target in the entire field of view- both before and after firing the round - the needed adjustment can be calculated independent of range and riflescope magnification. (However, the target must not be moved and that the shooter must not change position during the calibration procedure).

The servo motors are then activated so that the adjustment screws are turned the needed number of "clicks" in both horizontal and vertical directions. A green lamp lights up as an indication of a successful calibration. If the identification of the bullet hole fails, a red lamp lights up, and the procedure needs to be repeated (a possible cause for failure might be that the bullet has missed the target).

When the shooter finally presses the switch again, the calibration system is shut down (power off).

Alternative arrangements: The implementation of the device can be adjusted to the desired level of technology and automization as follows:

1. Traditional optical sight using a semi transparent mirror with no moving parts (1). This can be implemented using an electrically controlled electro-chromic film (EC film) placed in the line of sight. When powered, the EC film works as an semi-transparent mirror.

2. Traditional optical sight, splitting the beam using a moving semi-transparent mirror (1).

This can be implemented by a mechanically operated semi-transparent mirror. The mirror is moved between bi-stable positions by a lever on the outside of the sight, locked by form and/or friction.

3. Fully digital optical sight with traditional fixed or zoom lens for riflescopes, and a display in the viewfinder. Mechanical cross-hairs are not needed.

This can be implemented by a camera (2) placed directly in the line of sight, a microprocessor with memory and software (3), and a display (10) (typically a LCD - Liquid Crystal Display) in the viewfinder instead of a conventional lens. In this case the need for indicator lamps is eliminated since the calibration result can be displayed directly on the display. The switch (6) and power source (7) are still needed. In this variant the camera view is presented together with the cross¬ hairs as an all digital picture on the display. This fully eliminates the need for a mechanical adjustment of the cross-hairs, see sketch in figure 2. The calibration procedure is carried out as described above.

4. A separate device attached to a traditional optical sight. The separate device contains a camera and microprocessor and includes servo motors to be mounted onto the existing adjustment screws. This variant can be used together with traditional sights without any modification, whenever a calibration is needed. The variants can also be implemented as semi-automatic devices for adjustment of mechanical cross-hairs. The device then presents the shooter with information about the needed number of clicks, both in horizontal and vertical directions, to achieve alignment between the bullet hole and the cross-hairs. The shooter then carries out the adjustment manually according to the information. (The information can be projected via the semi- transparent mirror onto the viewfinder).

Claims

What we claim is:

1. Device for optical sight for firearms, for automatic calibration of mechanical cross-hairs (9) when shooting at a well defined target, assembled together with the sight, or as an attached separate device, characterized by a digital camera (2) for registration of the sight's orientation relative to the target at the firing moment and for registration of the projectile point of impact, and for folly automatic calibration also including electronically controlled servo motors (4) for adjustment of the mechanical cross-hairs.

2. Device according to claim 1 , characterized by the electronics (3) managing image sampling and storing of the samples in a buffer memory at a rate of 25 - 30 frames per second (fps) according to the principle of first in, first out (fifo).

3. Device according to claim 1 , characterized by the electronics (3) being designed for image processing operations for finding the target position, cross-hairs position and the projectile point of impact

4. Device according to claim 1, characterized by the electronics (3) being designed for calculation of calibration/adjustment of the mechanichal (alternatively digital, see claim n:o 12) cross-hairs (9) relative to the projectile point of impact and the orientation of the sight.

5. Device according to claim 1, characterized by the electronics (3) being designed to power and control servo motors (4).

6. Device according to claim 1 , characterized by the electronics (3) being designed for image analysis alternatively a separate sensor for detection of the firing moment and thereby, from the fifo-queue, selecting the image obtained immediately before the firing moment.

7. Device according to claim 1 , characterized by the electronics (3) being designed to indicate system status and calibration result.

8. Device according to claim 2, characterized by the electronics (3) being set up for saving the best image from the film sequence of the detection of the projectile impact point after firing.

9. Device according to claim 1, characterized by a semitransparent optical component (1), for example a mirror, splitting off a fraction of the light beam to the camera (2). An alternative would be if the camera chip could be made semi- transparent.

10. Device according to previous claim, characterized by that the semi transparent optical component (1) can be turned away from the line of sight at regular weapon use.

11. Device according to claim 1, characterized by the servo motors being equipped with suitable reduction gearing (5) provide great torque and precision as well as being irreversible in order to maintain the calibrated position without the need for active control.

12. Device at optical sight for bullet/projectile weapon for automatic adjustment/calibration of cross-hairs by test shooting at a well defined target, characterized by a digital camera (2) for registration of the viewfinder image including direct presentation of it on the display (10), and a non mechanical cross-hairs which is presented by software on the display(lθ) The camera is hereby also used for registration of the sight orientation relative to projectile impact point at the firing moment and for registration of the projectile point of impact and adjustment of the cross-hairs by software algorithms.

13. Device according to previous claim, characterized by inclusion of claims 2 to 8, but not claim 5.