TITLE OF INVENTION: AUTOMATIC SHADING MECHANISM FOR A CAMERA TECHNICAL FIELD

[0001] The invention relates generally to a shading mechanism for cameras, and more particularly to a device for shading the lens of a camera from intense light; and a method for automatically adjusting the shading device.

BACKGROUND ART

[0002] Digital cameras are widely used in surveillance and detection of objects or persons in day and night time. Modem Charged Coupled Device (CCD) and Complementary Metal Oxide Semiconductor (CMOS) cameras have become an effective tool in surveillance and detection. A wide variety of cameras are employed in photographing celestial objects to moving vehicles. Particularly in astronomical cameras and wide-field cameras, the quality of the images and continuous monitoring without interruptions is critical.

[0003] A video or photographic camera obtains data depending on the light level of the frame. If the frame contains an intense light source such as the sun, background objects of the video/photograph will not appear clearly. Intense light sources such as artificial lighting, full moon and sun have an adverse effect on the images captured from these cameras by saturating the sensor. In these saturated images most of the data is lost. Therefore, managing light conditions, particularly intense light, becomes critical in cameras.

[0004] Conventional camera sun shades generally consisted of a fixed hood with a supporting frame and an awning or fabric mounted on the supporting frame to cover a predefined area such as outdoor umbrellas and outdoor awning. However, a common problem with conventional sun shades like umbrellas and hoods is lack of wind resistance when situated in a high location such as roof tops. More specifically, such fixed shades are not suitable for astronomical cameras or sky cameras and wide-field cameras as the shade would block the view.

[0005] Most of the cameras contain an iris and a shutter to counteract with bright light. Modem digital cameras are now equipped with Auto Exposure (AE) feature where Red, Green and Blue colour intensities are measured to determine the exposure time. However, this AE feature is inadequate when light variation of the frame is significant. For example, this is very much visible in phone cameras when the light source directly falls on the screen. Thus the auto exposure feature does not work as well as manually changing the exposure time. An experienced photographer or a cinematographer may be able to determine the optimum exposure time by measuring light level using instruments and changing the position of the camera and light sources. However, automatic adjustment fails in such situations. As manual adjustment of the lens or exposure in astronomical cameras or sky cameras is impractical, photographing the sky has become an extreme challenge.

[0006] Thus mechanical shutters, irises and static shading mechanisms are some of the hardware methods utilized against this problem whilst real-time software solutions such as autonomous gain controls, International Organization of Standardization (ISO) sensitivity rating and fdters are used with the hardware for optimized photographing of scenes comprised of bright light sources.

[0007] Zhejiang Dahua Technology Co.’s Patent Application No. CN 106998429 (A) for ‘Camera capable of automatically adjusting sun shading cover and adjusting method’ discloses a sun shading cover for a camera wherein the sun shading cover switches an execution module for controlling the sun shading cover to be switched between a stretching state and a retracting state. The problem with this type of sun shades is that it can only block light that enter from above the shade. Further, this shade cannot be used in sky cameras or astronomical cameras or wide-field cameras as it would block the view of the lens.

[0008] Huayun Sounding Beijing Meteorol Technology Corp. & others’ Patent Application No. CN204177990 (U) for ‘Whole sky cloud cover automatic observation instrument with lens protection ball cover’ discloses a dynamic shading mechanism for protection of a camera from solar radiation. However the shading mechanism obstructs a large amount of field of view.

[0009] Shadecraft Inc.’s U.S. Patent Publication No. 20190014875 for ‘Intelligent Shading Objects Including a Rotational Hub Assembly, A Pivot Assembly, And a Single Shading Element’ discloses an automatic large shading mechanism used for roofs. However, due to mechanical complexity of the design, implicating a small-scale version in front of a camera is impractical. Their U.S Patent Publication No. US20170332750A1 for ‘Intelligent Shading System with Movable Base Assembly’ discloses another shading mechanism with arms connected to a base assembly movable using a motor. However, both these inventions do not relate to cameras and would also not be suitable for wide-field cameras as the base assembly would block the view.

[0010] Tianjin World Digital Video Co.’s Chinese Patent publication No. CN104678677A for ‘Novel monitoring camera shading cover’ discloses a shading cover for a monitoring device, consisting of a shading cap and the rotary cover as an integrated structure. The rotary cover is provided with teeth for rotation. However, the camera on which the visor is fixed is a surveillance camera and thus the visor only rotates along a horizontal axis.

[0011] Shenzhen Hua Antai Intelligent & Technology Co Ltd.’s Chinese Utility Model No. CN204031296 (U) for ‘Automatic shading mechanism for hemispherical camera’ discloses a shading mechanism using a hemispherical light blocking circle support, and a shading sponge. Light beams can be automatically shielded after the lens adjusts the direction and the angle and the focusing gate enables the lens to adjust the focus and the focal length. However, any direct light beams that enter perpendicular to the lens cannot be effectively blocked by this shading mechanism.

SUMMARY OF INVENTION Technical problem

[0012] Presence of a light source which is significantly brighter than the background of the object tends to saturate some or many of the pixels of the array. This saturation may cause the pixels to read less light signals from background objects and prolonged exposure to such a light source may even damage the sensor. Whilst a cameraman may manually adjust the exposure times at the time of capturing an image, this is not possible in cameras which are not directly operated by a cameraman. In other words, in cameras such as surveillance cameras or cameras fixed in places which are not easily accessible or cameras which operate continuously and thus require automatic adjustment of exposure times, require a reliable means to manage the effects of intense light conditions.

[0013] An iris of the camera which controls aperture of the incident light beam to limit the saturation of the sensor; and a shutter which completely blocks the incident light and open for a preconfigured time period to limit the exposure time of the sensor; both use a technique to limit the entire incident light, which makes it unsuitable or inadequate for certain types of cameras. For instance, in a narrow field camera, exposure time in the limited area/ frame may not have a considerable effect during a given time. However, a wide-field or 180-degree camera should adjust the exposure time to match the entire visible area/frame. Moreover, when sky is the subject, imaging the sky in a constant exposure time may result in images being dark or too bright and thus irises and shutters fall short.

[0014] Another generally used approach to take good photos under changing light conditions is artificial intelligence (AI) assisted post processing of images. These AI assistances can change Gamma, contrast, brightness or put overlays to artificially enhance a photo. However, these enhancements significantly alter the original data making it inappropriate for scientific photography.

[0015] Shading mechanisms which are fixed in the form of a roof or an overhead cover or a visor or utilize a stand or arms for support have the disadvantage of obstructing the view of the camera in certain circumstances. For instance, such covers would not succeed in cameras like sky cameras or wide-field/ 180-degree cameras which require a wide unobstructed view.

Technical Solution

[0016] The present invention, by contrast, relates to a shading mechanism which will only block the intense light rays by forming a physical barrier between the lens of the camera and the intense light rays of an identified light source, thereby controlling the exposure and allowing the imaging process to continue and further allow capturing and imaging of objects close to the intense light.

[0017] The problem is solved by a device consisting of an arcuate solid arm pivotally connected from one end, to the open end of a shaft connected to a motor, so that the arm when positioned near the lens of the camera is movable directly over the lens along a convex path. The arm is caused to rotate around the shaft axis by rotating the motor, such that when the arm is moved to a position over the lens, the arm obstructs intense light from directly entering through the lens. As the arm blocks predominantly the intense light, the rest of the lens is unobstructed allowing a wide unobstructed view. The effect may be further enhanced by an additional azimuth rotation of the arm around the lens using a trolley mounted on a rail encircling the base of the lens. The arm and the motor are mounted on the trolley and the trolley is caused to orbit the base of the lens by rotating a second motor attached to the wheels of the trolley. A sensor and a processor is used to detect intense light sources using real-time image processing and control the motor-arm ensemble and the motor-trolley ensemble, whereby the saturated region in the lens is obstructed by the arm. If the light source is moving the arm will be automatically moved with the light source continuously while maintaining the obstruction. The arm when not actively blocking a light source, will be in a resting position beside the lens without obstructing its view.

Advantageous effects

[0018] There are many advantages in using a shade as disclosed in the present invention. It is an intelligent shading mechanism with a degree of freedom around a single axis, around the lens, covering the whole lens. Thus, the mechanism can follow a moving object to obstruct incident light from the source.

[0019] Hardware design of the mechanism may be compact small-scale design wherein the mechanism can be placed under a protective dome/glass 1cm - 6cms away from the lens. This allows the mechanism to be placed inside the main enclosure of the camera rather than placing outside the camera assembly. Therefore, the mechanism is safe from weathering and external factors, and ensures consistent functioning.

[0020] In the event of a software or hardware failure the mechanism will come to a halt in a resting position whereby the arm lies beside the lens avoiding the obstruction to the camera.

[0021] Unlike in prior art, the shading mechanism in the disclosed invention does not block the view of the camera lens and is capable of clearly imaging objects appearing near the intense light whilst blocking only the intense light rays.

[0022] This is particularly beneficial for use in a day and night camera used for imaging the sky during both day time and night time using a single camera. Usually, due to the differences in exposure time ranges, a single camera is not preferred and thus two different cameras are used for day time imaging and night time imaging. However, two wide-field cameras cannot be kept at the same location as one would block the view of the other. Therefore, the shading mechanism allows a camera more sensitive for night photography to be used during the day time by managing light conditions.

[0023] Such advantages are not found in other shading mechanisms disclosed or currently available.

BRIEF DESCRIPTION OF DRAWINGS

[0024] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any manner. The Detailed Description will make reference to a number of drawings as follows:

Fig. 1 illustrates a side perspective view of a shading apparatus according to an embodiment with a strip arm.

Fig. 2 illustrates a side perspective view of the strip-motor component of Fig. 1. Fig. 3 illustrates a side view of Fig. 1 with a protective cover over the lens.

Fig. 4 illustrates atop perspective view of Fig. 1 in a resting position.

Fig. 5 illustrates a side view of a shading apparatus according to a second embodiment with a wire arm.

Fig. 6 illustrates a side view of Fig. 5 with a protective cover over the lens.

Fig. 7 illustrates a bottom perspective view of a rail-trolley component of a shading apparatus according to a third embodiment.

Fig. 8 illustrates a side perspective view of a shading apparatus according to Fig. 7 with a strip arm.

Fig. 9 illustrates a side view of Fig 8.

Fig. 10 illustrates a side perspective view of a shading apparatus according to Fig. 7 with a wire arm.

Fig. 11 illustrates atop view of Fig. 10.

DESCRIPTION OF EMBODIMENTS

[0025] This shading mechanism discusses hardware and a system made for digital cameras to record data without a loss under intense light sources.

[0026] In the shading device, it is possible to block the intense light rays by making a physical barrier between the lens of the camera and the intense light rays of an identified light source, thereby controlling the exposure and allowing the imaging process to continue and further allow capturing/ imaging of objects close to the intense light. The shading device when not actively blocking a light source, may be in a resting position where the arm rests beside the lens without obstructing its view, which is convenient.

[0027] Preferred embodiments of the invention are described below by way of example only.

[0028] In an embodiment, the shading apparatus consists of a solid arm having an arc shape and a motor. A shaft is connected to the motor for causing rotation. The arcuate arm is pivotally connected from one end, to the open end of the shaft connected to the motor. The arm is positioned near the lens of the camera in a manner that allows the arcuate arm to move directly over the lens along a convex path. Furthermore, a sensor is positioned near the lens of the camera to receive information on the lighting conditions which is then processed using a processor to detect intense light sources and its direction. The processor then sends signals to the motor to cause it to rotate. The rotation of the motor causes the arm to move over the lens of the camera. The saturated region in the lens is thus obstructed by the arm. If the light source is moving the arm will be automatically moved with the light source continuously to maintain the obstruction. The chord value of the arc in the arm is designed to be greater than the diameter of the lens so that the arm may be rotated freely around the lens of the camera. A protective cover or a protective dome may be easily placed over the shading apparatus, covering the lens and the shading apparatus.

[0029] In an embodiment, the arm of the shading apparatus may be a strip having a width which functions as the obstructing surface.

[0030] For the purpose of illustrating a clear example of the above embodiment having a strip for an arm, Fig. 1 through Fig. 4 are described together.

[0031] Fig. 1 illustrates a side perspective view of a shading apparatus according to an embodiment. The shading apparatus includes an arcuate strip 1, a motor 2, and a shaft 5. A sensor 4 is used to receive and detect light rays and communicate information to a processing device. As illustrated, the apparatus is positioned near the lens 3 of a camera which is elevated relative to the motor 2 and the shaft 5 whilst the arcuate strip 1 is positioned to be rotatable over the lens 3 of the camera.

[0032] Fig. 2 illustrates a side perspective view of the strip-motor component of Fig. 1. The arcuate strip 1, the motor 2, and the shaft 5 are illustrated therein.

[0033] Fig. 3 illustrates a side view of Fig. 1 with a protective cover over the lens. Referring to Fig. 3, the shading apparatus may be positioned for use inside a protective dome or cover 6.

[0034] Fig. 4 illustrates a top perspective view of Fig. 1 in a resting position. In an illustrative embodiment, the arcuate strip 1 may be positioned beside the lens 3, in a resting position. As illustrated in Fig. 4, the resting position allows the lens 3 to achieve an unobstructed view as the arcuate strip 1 lies beneath the field of view of the lens 3 of the camera when not in use. [0035] Furthermore, the strip 1 may be made from Polyamide and polished to mitigate the heat radiation. Long exposure to the sun rays during the day may affect the function of the arm by warping and/or heating up. This may thus be minimized by using material which mitigate heat radiation. The upper surface of the strip 1 may be polished to reflect the heat radiation and simulation of the heat under direct exposure to sun or other light rays that radiate heat. Thus the thermal expansion can be mitigated by the arcuate shape. The strip 1 may also be designed to inherit a low centre of gravity. The strip 1 may have a gradually sloping thickness or a decreasing thickness wherein the tip of the strip 1 has the lowest thickness. The strip 1 may thus taper towards the open end. This thickness variation is capable of bringing the centre of gravity of the strip 1 to a lower position, such that the weight of the strip 1 is exerted upon the rotational axis of the motor 2.

[0036] In another embodiment, the arm may be a rod or a wire having a narrower surface than a strip 1. A disk mounted on the rod or the wire may act as the obstructing surface, whereby the disk will be positioned directly between the intense light and the lens 3, by moving the rod or the wire it is mounted on.

[0037] For the purpose of illustrating a clear example of the above embodiment having a wire for an arm, Fig. 5 and Fig. 6 are described together.

[0038] Fig. 5 illustrates a side view of an embodiment of the shading apparatus as described above comprising an arcuate wire 7 for an arm. A disk 8 is mounted on the arcuate wire 7.

[0039] Fig. 6 illustrates a side view of Fig. 5 with a protective cover 6 over the lens 3. The ability to position the arcuate wire 7 and the disk 8 inside the protective dome/ cover 6 is illustrated in this drawing.

[0040] Accordingly, more surface of the lens 3 will be unobstructed by the narrow rod or wire 7 whilst only the intense light will be blocked by the disk 8. The size or shape of the disk 8 may be varied based on the area of the lens 3. Further, the position of the disk 8 in the wire may be adjusted depending on the preferences and the disk 8 may be replaced with different diameter disks to match the size of the image projected by the intense light source over the lens 3. Particularly, when the path of an intense light such as the sun or moon is known, the disk 8 may be positioned to block direct sun rays or moon rays based on the position of the sun and/or the moon in the sky relative to the lens 3.

[0041] In another embodiment of the shading apparatus, the arm and the motor 2 connected to the arm may be moved with the arm, around the base of the lens 3 in an azimuth rotation, using a rail -trolley ensemble, instead of being positioned stationary.

[0042] Fig. 7 illustrates a bottom perspective view of a rail-trolley component of a shading apparatus according to a third embodiment described above. The trolley 10 is mounted on the rail 9 and the second motor 11 is rotatably connected to the wheels 12 of the trolley 10 for causing the rotation of the wheels 12 in order to move the trolley 10 on the rail 9. The arm and the motor 2 connected to the arm are mounted on the trolley 10.

[0043] As illustrated above in Fig. 7, an embodiment may further comprise a trolley 10 upon which the arm and the motor 2 connected to the arm may be mounted on; and a rail 9 arranged around the lens 3 for enabling movement of the trolley 10 on its track. The trolley 10 may be caused to move along the rail track 9 by a second motor 11 attached to the trolley 10. The shaft of the second motor 11 may be rotatably connected to the wheels 12 of the trolley 10 for causing the wheels 12 to rotate when the shaft of the second motor 11 is rotated.

[0044] Accordingly, the trolley 10, with the arm and the motor 2 connected to the arm mounted on it, may orbit the lens 3 allowing better positioning of the arm against intense light. In a preferred embodiment, the rail 9 may be generally circular shaped, which is convenient. The rail 9 may be supported on one or more pillars in a manner that does not obstruct the movement of the trolley 10. The second motor 11 which moves on the rail 9 may be powered by cables which do not obstruct movement of the second motor 11.

[0045] Similar to other embodiments discussed above, the arm may be positioned near the lens 3 of the camera in a manner that allows the arcuate arm to move directly over the lens 3 along a convex path. A sensor 4 may be positioned near the lens 3 of the camera to receive information on the lighting conditions which is then processed using a processor to detect intense light sources and its direction. According to the above embodiment having a rail-trolley ensemble, the processor may then send signals to the motor 2 connected to the arm and the second motor 11 connected to the trolley 10 to cause their rotation. The rotation of the motor 2 and the second motor 11 causes the arm to move around and over the lens 3 of the camera simultaneously. The saturated region in the lens 3 may thereby be obstructed by the arm. If the light source is moving the arm will be automatically moved in altitude -azimuth directions with the light source to continuously maintain the obstruction.

[0046] For purposes of illustrating a clear example of an embodiment where a strip arm is moved in an azimuth rotation, Fig. 8 and Fig. 9 are described together.

[0047] Fig. 8 illustrates a side perspective view of a shading apparatus according to Fig. 7 with a strip arm 1. Fig. 9 illustrates a side view of Fig 8. According to the embodiment, an arcuate solid strip 1 is connected to a motor 2 and are mounted on a trolley 10. The trolley 10 is mounted on a rail 9 which encircles the base of the lens 3 allowing movement around the base of the lens 3 in an azimuth rotation. Upon locating the direction of the intense light through a sensor 4, and a processor, the strip 1 is caused to move in order to block the intense light from a direction which enables obstruction of the intense light, whilst maintaining minimum obstruction of the rest of the view of the lens 3.

[0048] A distinct advantage of the ability to move the arm around the base of the lens 3 in an azimuth rotation, in addition to rotating over the lens 3, is that it overcomes the requirement to be oriented towards a particular direction in order to match the motion or path of the sun or moon in the sky. The orbit around the base of the lens 3 enables the arm to block intense light rays from any direction, which is convenient. The advantage is more evident where the arm is an arcuate wire 7 with a disk 8 mounted on it. Therein, the position of the disk 8 may be controlled by the combination of azimuth and altitude rotation of the wire 7. In other words, it enables the disk 8 to move physically to any point over the lens 3. The trolley 10 may perform a 360 degree azimuth rotation around the base of the lens 3 both clockwise and anti -clockwise. This may prevent any power supplying cord to the second motor 11 from getting tangled by an otherwise one-way orbit.

[0049] For purposes of illustrating a clear example of an embodiment where a wire arm with a disk is moved in an azimuth rotation, Fig. 10 and Fig. 11 are described together.

[0050] Fig. 10 illustrates a side perspective view of a shading apparatus according to Fig. 7 with a wire arm 7 and Fig. 11 illustrates a top view of Fig. 10. According to these embodiments, an arcuate solid wire 7 with a disk 8 mounted on it, is connected to a motor 2 which are then mounted on a trolley 10. The trolley 10 is mounted on a rail 9 which encircles the base of the lens 3 allowing movement around the base of the lens 3 in an azimuth rotation. Upon locating the direction of the intense light through a sensor 4 and a processor, the processor sends signals to both motors (the motor 2 connected to the wire arm 7 and the second motor 11) and the wire 7 is caused to move to block the intense light. The azimuth rotation around the lens 3 and the rotation of the wire 7 over the lens 3 coupled together enables the disk 8 to be positioned above any spot over the lens 3. This enables obstruction of the intense light by the disk 8 whilst maintaining minimum obstruction of the rest of the view of the lens 3 by the narrow wire 7.

[0051] In an alternative embodiment, the arm may be connected from both ends. Whilst one end is pivotally connected to a motor 2, the other end may be pivotally connected to a base using a nut and bolt. In such embodiment, the strip 1 need not necessarily have a gradually sloping thickness or a tapered end, whilst having such gradually sloping thickness would be advantageous. When the motor 2 causes the arm to rotate from one end, the other end rotates around the bolt.

[0052] In the embodiments, the motor 2 connected to the arm, may be a servo motor or a stepper motor. However, as the arm only moves or rotates around the shaft axis 180 degrees, a servo motor would suffice.

[0053] As the rail 9, the wire 7 and the disk 8 will be exposed to solar radiation the most suitable material to construct them would be Teflon. However white painted aluminium is also a suitable alternative.

[0054] In an embodiment, the processor is capable of detecting any intense light source present in the frame and the location of the source. For identifying intense light sources, each pixel value (digital values 0-255) of the sensor may be analysed to identify pixels with 200-250 saturation. Subsequently sensor array may be projected to an X-Y coordinate system where each pixel is denoted in X, Y. The location and area of the saturated region may be identified from the projected coordinate system and the rate of change of the location with time may be monitored to detect any motion of the light source. The resting position where the arm lies beside the lens may be taken as the initial position. If pixel values of the sensor is less than 200 the arm may be positioned in the resting position.

[0055] In an embodiment, each step size of the motor 2 and the second motor 11 may be counted in degrees and the X-Y coordinate system converted to a spherical coordinate system. Henceforth the motor 2 and second motor 11 may be given the coordinates of the location of a saturated region in order to rotate. In the event of an error the arm may be brought to the resting position.

[0056] In an embodiment, the processing of the information communicated from the sensor 4 and the lens 3 of the camera may be done using real-time image processing. For this, the motor-arm ensemble and the motor-trolley ensemble may be controlled from a single board computer where three consecutive images may be processed to identify and predict the location of the intense light source. The exposure time range of the sensor may be 64us to 2000s where longer exposure is used for night time photography.

[0057] In day time photography if the Sun is present in the frame, the optimum exposure time will be around 20us. However where a camera’s minimum exposure time is 64us, the problem can be fixed using the shading mechanism. When the shading mechanism continuously blocks the sun from saturating the lens 3, the camera can take images in 64us-100us exposure time range. The sensor camera 4 may have a narrow field of view whereby the obstruction from the main camera lens 3 is prevented. The main camera or the lens 3 used for actual imaging is placed on a higher level than the sensor 4, hiding the sensor 4 from the wide field of view of the main camera lens 3.

[0058] The Hardware design of the mechanism may be a compact small-scale design so that the device can be placed under a protective dome/glass, ideally 1cm - 6cms away from the lens 3. This allows the device to be placed inside the main enclosure of the camera rather than placing outside the camera assembly, protecting it from weathering and external factors, ensures consistent functioning.

Industrial Applicability

[0059] The shading mechanism has direct application in All-Sky cameras used to monitor the sky for enhancing the imaging capability of day time photos. The invention has a wide application in cloud and stellar objects monitoring wide-field cameras, for obstructing intense light sources such as sun and moon. This will enhance the capabilities of cameras in photographing objects in the background of intense light sources.

[0060] The mechanism can also be used against infrared light attacks used to blind security cameras by blocking a rapidly moving or stationary light sources. For instance, in security cameras to block light beams used by burglars to saturate the camera.

[0061] Additionally, it can be used in all types of cameras to obstruct intense light sources from view. For instance, this technique has a potential industrial application in mobile phone cameras. As most of the phones are already equipped with two cameras this technique can be integrate to take better pictures in varying light conditions.

[0062] Thus, the invention denotes implications in the fields of Astronomy, Atmospheric Physics and Security.