GB2191305A - Optical apparatus - Google Patents

Abstract

A device for allowing the recordal of a cyclically moving object-e.g. a rotating propeller-includes a shutter assembly 16 mounted in front of the lens 11 of a video camera 10. The shutter assembly includes a rotary shutter 22 whose rotational speed is continuously variable to synchronise with the rate of movement of the object. <IMAGE>

Description

SPECIFICATION Optical apparatus This invention relates to optical apparatus for use in providing a visual record of a cyclically moving object, and in particular, but not exclusively to such apparatus for providing a visual record of a rotating propeller.

One of the many tests which any aircraft must undergo before it receives certification from the appropriate aviation authority is an icing test in which the manufacturer of the aircraft must prove to the authority that the aircraft is capable of removing ice from regions of the aircraft where it tends to form.

One of the specific omponents of the aircraft which need to have adequate deicing capability is the aircraft propeller, and the aviation authority requires evidence that the aircraft has flown through conditions under which ice has built up on the leading edge of the propeller, and that the propeller deicing device managed to break up or otherwise remove this ice.

In conventional certiciation routines, the aircraft is flown on a specific sortie, the sole reason of which is to find icing conditions and then subject the aircraft to the various tests, with a professional photographer on the aircraft to record evidence of this. During this specific test, the aircraft is flown through icing conditions and the relevant propeller is then brought to a standstill to allow it to be photographed with ice on it and then restarted. The deicing equipment is then activated to cause removal of the ice and the propeller brought to a standstill again to allow the propeller to be photographed after operation of the deicing equipment.

It will be appreciated that this routine has several drawbacks; the requirement for a professional photographer to take photographs of the propeller at rest means that this routine is expensive in terms of aircraft time, and it does not allow deicing tests to be carried out in conjunction with other tests when the aircraft is found to be flying through the right atmospheric conditions for icing to occur. In addition, it is not possible to observe the actual mechanisms of ice accretion and ice removal as they develop.

According to one aspect of this invention, there is provided apparatus for providing a visual record of a cyclically moving object said apparatus comprising: image sensor means for receiving the image of a viewed scene and for outputting a signal representative of said viewed scene; signal recording means for recording said signal; shutter means disposed in front of said image sensor means and arranged to open and close to respectively allow and prevent passage of light from said viewed scene to said image sensor means; shutter drive means for opening and closing said shutter means, and shutter drive control means operable for varying the rate at which said shutter opens, thereby to enable said opening rate to be varied in synchronism with the rate of movement of said object.

By this arrangement, the cyclically moving object-eg a rotating propeller-may be recorded and viewed via the image sensor means as a stationary object even though it is rotating at high speed. This feature allows the accretion and subsequent destruction of an ice layer to be observed without the need to alter the running conditions of the propeller. In addition, it is possible instantly to assess the quality of the recording by means of observing the recorded scene through a view finder of associated with the sensor the camera.

This obviates the need for the presence of a professional photographer to take photographs of the propeller at rest.

Preferably said shutter means includes a rotary shutter member and said rotary shutter inember may conveniently comprise a slotted disc.

Preferably said shutter drive means includes an electric motor, and said shutter drive control means comprises an electrical circuit for continuously varying the rotational speed of said motor.

Advantageously said image sensor means comprises a part of a portable television camera which further includes image-forming lens means, and said shutter means is rotatably mounted within a housing which includes an inlet aperture for receiving radiation from the viewed scene, and an outlet aperture for being fitted around the image-forming lens means.

In another aspect of this invention, there is provided a shutter assembly for being attached in front of the lens of a television camera, comprising a generally light-tight housing having in opposed walls thereof an inlet and an outlet aperture for light said outlet aperture being adapted for engaging the lens of said camera in substantially light tight engagement, means for securing said housing to said television camera, rotary shutter means mounted within said housing and adapted to interrupt the passage of light between said inlet aperture and said outlet aperture, rotary drive means for rotating said shutter and control means for varying the rotational speed of said drive means.

Further aspects of the invention will become apparent from the following description which is by way of example only in which reference will be made to the accompanying drawings, in which, Figure 1 is a schematic side view of the visual recording apparatus of this invention, and Figure 2 is a schematic view of a propeller driven aircraft including visual recording appa ratus of this invention.

Referring initially to Fig. 1, the apparatus illustrated comprises a video camera 10 having a lens 11, an eyepiece 12, a trigger 13 an image sensor 9, and an output lead 14 for connection to a video recorder 15. Such combinations of video camera and video recorder are commerically availabe from many outlets, and details of their operation are well known to those skilled in the arts.

A secondary shutter unit 16 is secured to the handle 17 of the video camera 10 by means of a bracket 18. The shutter unit comprises a generally light-tight flat cylindrical housing 19 having a generally circular inlet aperture 20 and a tubular outlet portion 21 for engaging the lens of the camera in light-tight manner whilst still allowing focussing movement of the lens. A slotted disc member 22 is supported within the housing for rotation about axis A by means of a drive shaft 23 of a electric motor 24. Power is supplied to the motor 24 from a battery 25 by means of a control device 26. The control device includes an on/off switch 27 and an adjustment potentiometer 28 arranged to control in known fashion the output speed of the electric motor 24.

Referring now to Fig. 2, there is shown the device of Fig. 1 when set up in the cabin of an aircraft to provide visual evidence of the accretion and removal of an layer of ice on the propeller leading edge. A high intensity light 30 is located rearwardly of the video camera 10 to illuminate the propeller 31 transversely through a porthole in the side of the fuselage. Rearwardly of the light 30 in a further porthole there are located a liquid water content probe 32 and an ice accretion rate head 33 which are of known design.

When it is wished to observe the growth or removal of ice from the propeller, tlhe propeller is illuminated by high intensity light 30 viewed through the eyepiece 12 of the camera. Potentiometer 28 is adjusted to bring the speed of the slotted disc 22 into sychronisation with the rotational speed of the propeller to "freeze" the motion of the propeller. The video recorder is actuated by means of the trigger 13 on video camera 10 to record the accretion, or as the case may be, the removal of ice from the propeller. In this particular embodiment, the disc 21 comprises a sheet of opaque material provided with a signle radial slot roughly 1/16th of an inch wide. The visual recording apparatus described above makes use of the momentary imge retention of the image sensor used in conventional video cameras, and thus potential problems caused by asychronism of the rotational speed of the disc and the speed of the camera are obviated. The image sensor may be a solid state sensor such as a frame transfer charge coupled device.

Instead of providing manual control of the speed of rotation of the slotted disc, data representing the rotational speed of the relevant propeller may be taken from the aircraft data stream and used to synchronise the rotational speed of the slotted disc and the propeller.

Claims (8)

1. Apparatus for providing a visual record of a cyclically moving object said apparatus comprising: image sensor means for receiving the image of a viewed scene and for outputting a signal representative of said viewed scene; signal recording means for recording said signal; shutter means disposed in front of said image sensor means and arranged to open and close to respectively allow and prevent passage of light from said viewed scene to said image sensor means; shutter drive means for opening and closing said shutter means, and shutter drive control means operable for varying the rate at which said shutter opens, thereby to enable said opening rate to be varied in synchronism with the rate of movement of said object.

2. Apparatus according to claim 1, wherein said shutter means includes a rotary shutter member.

3. Apparatus according to claim 2, wherein said rotary shutter member comprises a slotted disc.

4. Apparatus according to claim 1, wherein said shutter drive means includes an electric motor, and said shutter drive control means comprises an electrical circuit for continuously varying the rotational speed of said motor.

5. Apparatus according to claim 1, wherein said image sensor means comprises a part of a portable television camera which further includes image-forming lens means, and said shutter means is rotatably mounted within a housing which includes an inlet aperture for receiving radiation from the viewed scene, and an outlet aperture for being fitted around the image-forming lens means.

6. A shutter assembly for being attached in front of the lens of a television camera, comprising a generally light-tight housing having in opposed walls thereof an inlet and an outlet aperture for light said outlet aperture being adapted for engaging the lens of said camera in substantially light tight engagement, means for securing said housing to said television camera, rotary shutter means mounted within said housing and adapted to interrupt the passage of light between said inlet aperture and said outlet aperture, rotary drive means for rotating said shutter and control means for varying the rotational speed of said drive means.

7. Apparatus substantially as hereinbefore described with reference to and as illustrated in, any of the accompanying drawings.

8. A shutter assembly substantially as hereinbefore described with reference to and as illustrated in, any of the accompanying drawings.