WO2003030633A1

WO2003030633A1 - Surveillance systems

Info

Publication number: WO2003030633A1
Application number: PCT/GB2002/004456
Authority: WO
Inventors: Luke Sanger
Original assignee: Ecowatch Limited
Priority date: 2001-10-06
Filing date: 2002-10-02
Publication date: 2003-04-17
Also published as: GB0124107D0

Abstract

A surveillance system for use with a wildlife box 10 includes a camera 1 mounted within the box and illumination means 2 for lighting an area of shade within the box. A control system 4 has a light sensor 5 which is arranged to control the illumination means to progressively increase the light output at a steady rate when the ambient light level increases outside the box and progressively reduce the light output when the ambient light level falls. The system therefore avoids sudden changes in light level within the box which would might otherwise cause disturbance to wildlife using the box.

Description

SURVEILLANCE SYSTEMS

TECHNICAL FIELD OF THE INVENTION

This invention relates to surveillance systems, particularly, but not exclusively, for watching wildlife.

BACKGROUND

It is becoming increasingly popular to install surveillance systems which permit the activities of various creatures to be monitored remotely with minimum disturbance to the creatures themselves. Modern cameras have solid state image sensors which are capable of operating under low ambient light conditions, but in order to provide a good image over a range of lighting conditions, from very low light to bright sunlight, complex and costly control devices are required, which also increase the size of the camera system.

A more uniform lighting level has been achieved by using an inexpensive solid state camera which incorporates a light source to illuminate the area under surveillance. Such an arrangement has been used successfully, and achieves reasonable quality at relatively low cost. However, this is not ideal as it involves an increased risk of disturbing certain kinds of wildlife and may be environmentally unacceptable in situations where the lights would be visible at night, for example.

The present invention seeks to provide a new and inventive form of surveillance system which is capable of providing high quality images under a wide range of ambient light conditions whilst keeping the cost and size of the equipment to a minimum and which also minimises the amount of disturbance caused in the area under surveillance.

SUMMARY OF THE INVENTION

The present invention proposes a surveillance system which includes a camera, illumination means for lighting an area of shade within the field of vision of the camera, and a control system including a light sensor which is arranged to control the illumination means such as to progressively increase the light output at a steady rate when the ambient light level outside the shaded area increases.

Thus, for example, in a wildlife shelter during good external ambient light conditions (e.g. in the morning) the light level will gently increase inside the shelter with minimum disturbance to the occupants, so that good quality colour recording is possible. As the ambient light level fades towards dusk the control means preferably progressively reduces the light output from the illumination means. In this way the normal diurnal patterns of light are mimicked inside the shelter, but the intensity and speed of changes in illumination are carefully controlled to avoid disturbance.

The light sensor can be located locally or remote from the camera depending on the circumstances under which the system is used, but it is generally preferable to locate the light sensor remote from the camera so that the operation of the light sensor is unaffected by the light emitted by the illumination means.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description and the accompanying drawings referred to therein are included byway of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings:

Figure 1 is a general view of a wildlife surveillance system in accordance with the invention; and

Figure 2 is a circuit diagram of a light control unit which is included in the system.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to Fig. 1, a solid state CCD camera 1 is installed in a wildlife box 10 such as a bat box or bird box. The camera may contain an integral microphone and includes a number of white light sources 2 (in this case six) which are preferably in the form of light-emitting diodes (LEDs). A thin flexible cable 3 leads from the camera to the outside of the box 10, including d.c. power supply lines (+ and -) for the CCD image sensor, video and audio outputs, and a separate line for supplying power to the LEDs.

Outside the box 10 the cable 3 is connected to a control unit 4 which may be mounted in any suitable position, preferably adjacent to the box 10. The control unit includes an opto-electronic light sensor 5, with brightness and sensitivity controls 6 and 7. A further cable 8 leads from the control unit 4 to a remote monitoring position 9, which includes a monitor screen 12 power supply 13, etc.

Fig. 2 shows the circuit diagram of the electronics contained within the control unit 4. The incoming supply voltage passes through a reverse- protection diode D1 , and a voltage regulator IC3 provides a steady supply voltage Vcc with decoupling capacitors C3 and C4. A microcontroller IC2 is programmed to provide an output voltage which is dependant on an input level which is determined by a potential divider formed by the light sensor LDR and sensitivity control potentiometer RV2 which together determine the ambient light level at which the microcontroller starts to produce the output voltage.

The microcontroller is programmed such that an increase in input level will only produce a controlled and progressive increase in the output voltage over a period of time (e.g. one minute).

The output from IC2 is amplified by IC1 to control a MOSFET switch Q1 , the maximum output being adjustable by the brightness control RV3. The brightness of the six light sources LED1-6 within the camera 1 is controlled by the power applied by Q1 via the cable 3. It should however be emphasised that Q1 only affects the brightness of the LEDs. It does not control the voltage supplied to the CCD image sensor or electronics inside the camera.

The brightness of the LEDs is thus controlled to mimic and track temporal changes in the natural ambient light levels inside the wildlife box, avoiding sudden changes which could cause disturbance to wildlife inside and outside the box such as birds, bats etc. The maximum illumination level is determined by the brightness control 6/RV3. The LEDs effectively exaggerate the natural light levels which would vary inside any wildlife box due to light entering through an entrance hole, gaps or fissures in the walls. The wildlife is completely unaware that the light levels in the box are being controlled, but since the light levels can be increased during daylight conditions the clarity of images obtained by the camera can be considerably improved. Under low ambient light levels the LEDs slowly decrease in brightness to mimic the decrease in light levels outside. Under low light conditions or total darkness the LEDs are completely dark, the threshold level being determined by the sensitivity control 7/RV2.

It will be appreciated that the features disclosed herein may be present in any feasible combination. Whilst the above description lays emphasis on those areas which, in combination, are believed to be new, protection is claimed for any inventive combination of the features disclosed herein.

Claims

1. A surveillance system which includes a camera (1), illumination means (2) for lighting an area of shade within the field of vision of the camera, and a control system (4) including a light sensor (5) which is arranged to control the illumination means such as to progressively increase the light output at a steady and controlled rate when the ambient light level increases outside said area of shade.

2. A surveillance system according to Claim 1 , in which the control means (4) is arranged to progressively reduce the light output from the illumination means (2) at a controlled rate when the ambient light level falls outside said area of shade.

3. A surveillance system according to Claim 1 , in which the light output from the illumination means is controlled by a semiconductor switching device (Q1 ).

4. A surveillance system according to Claim 1 , in which the camera (1 ) and the illumination means (2) are installed in a box (10) for use by wildlife.

5. A surveillance system according to Claim 1 , in which the light sensor (5) is located remote from the camera (1 ) and the illumination means (2).