GB2416036A

GB2416036A - Electronic device with motion sensor to determine likely impact and protect against damage or to enable the device.

Info

Publication number: GB2416036A
Application number: GB0415057A
Authority: GB
Inventors: Richard George Vivian Doble
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-07-05
Filing date: 2004-07-05
Publication date: 2006-01-11
Also published as: GB0415057D0

Abstract

A camera is provided with accelerometer sensors (S1, S2) which are arranged to detect either movement indicative of the camera being dropped or knocked out of a user's hands, in which case the motor control unit (2) is instructed to automatically retract the camera's lens unit (B1, B2) in the few tenths of a second before the camera hits the ground, or to detect substantial upward movement indicative of intended use when the camera is in a standby state with the lens unit retracted. In the latter case the retracted lens unit is automatically extended and the camera circuitry is switched on to enable the camera to be used as soon as it reaches eg eye level. In the former case potential damage to the camera lens unit is prevented and in the latter case the startup time of the camera is effectively eliminated, increasing the picture-taking opportunities. The principle may be applied to other electronic devices such as portable computers, disc drives and mobile phones where some form of protective action may be taken.

Description

Motion-seg,singystem for Portable Electronic Eugmet The present invention

relates to motion-sensing systems for portable (particularly hand-held) electronic equipment and to electronic equipment incorporating such systems. The invention relates particularly but not exclusively to cameras (including both digital and film cameras and both still and video cameras). The invention is especially applicable to cameras having extendable/retractable lenses.

According to one major camera repairer, approximately 40% of camera repairs arise lo from accidental impacts to the camera body, of which a significant proportion involve impacts to the lens system. In a typical compact camera the lens extends in use and is retracted automatically on switching off the camera. If such a camera is dropped during use there is a significant risk of the camera landing on its extended lens and telescoping the lens back into the camera body, which will inevitably damage the lens drive and focussing systems. In many cases the lens unit is not serviceable and must be replaced if damaged, resulting in a very costly repair.

An object of the present invention in one aspect is to provide a protective system which can be utilised in a camera or other portable (particularly hand-held) electronic equipment to provide a degree of protection against impact damage eg to a retractable camera lens.

An object of the present invention in another aspect is to alleviate the problem of time lag between switching on a camera or other portable (particularly hand-held) electronic equipment and the lens or other circuitry of the equipment becoming ready for use. This time lag, or startup time, can result in the loss of a picture-taking opportunity for a camera user.

It is known eg from US 5,881,321 to incorporate inertial sensors in cameras. In this known system inertial sensors are mounted on the camera to detect its movement along three orthogonal axes, as well as angular rotation about the three axes. Linear and angular acceleration detected by the sensors is transmitted from their location on the camera to a remote site, preferably by means of wireless communication. A time code is coupled with the data from the sensors, so that the instantaneous position of the camera can be determined for any point in time during the recording of live action. In addition, other information which may be relevant to the scene being recorded, such as the camera's operating parameters, can also be transmitted.

The above information is not used to control the camera however.

s US 5568211 and US 5596382 disclose inertial sensors used to trigger vehicle mounted cameras to record a collision of a vehicle and are similarly irrelevant - it is implicit that the camera is activated throughout the collision.

It is also known to mount inertial sensors in stereogrammetric cameras in order to lo record the postion and orientation of the camera.

In one aspect the invention provides a protective system for portable electronic equipment comprising motion-sensing means arranged to generate an output signal indicative of a potential impact, and protective means responsive to said output signal to configure the portable electronic equipment to a protected state in advance of such an impact.

In the case of a compact camera having a retractable lens, the protective system can be used to retract the lens within the camera body, for example. Modern compact cameras have very fast-acting lens motors in order to reduce startup time to a minimum and therefore it is practicable for a camera lens to be retracted in the few tenths of a second available between dropping the camera and the camera reaching ground level.

2s Preferably said motion-sensing means is arranged to detect unconstrained motion of the portable electronic equipment and generate said output signal in dependence thereon.

In normal use a camera or other portable electronic equipment (such as a mobile phone for example) is hand-held and to that extent its motion is constrained. It is virtually impossible for a user to move the equipment with a constant velocity or even a constant acceleration without releasing it from his or her grasp and unconstrained motion is therefore a very good indication that the equipment has in fact been dropped or thrown and is liable to be damaged by the impact on landing. as

In one embodiment said motion-sensing means is arranged to detect free fall of the portable electronic equipment. By free fall is meant any condition (including having been thrown upwardly) in which the equipment experiences a substantially constant acceleration g due to gravity. Depending on the size, shape and weight of the equipment it may be necessary to make some allowance for slightly erratic deceleration due to air resistance. The degree of latitude can be determined empirically.

In one embodiment said motion-sensing means is arranged to detect transient motion of the portable electronic equipment and to generate said output signal in lo dependence thereon.

Normally a hand-held item of electronic equipment is dropped only in response to a knock which is sustained either by the user or by the equipment directly. Such a knock will result in a transient motion such as a sudden acceleration and/or deceleration which is highly uncharacteristic of normal use and which is therefore an excellent predictor of a potential impact.

In particular said motion-sensing means is preferably arranged to detect a change in acceleration to a substantially constant acceleration of the portable electronic equipment and to generate said output signal in dependence thereon. A change in acceleration indicates a knock and a change to a substantially constant acceleration (due to gravity - although the change in acceleration may be measured in a horizontal direction only in which case the horizontal acceleration will fall to zero) indicates that the item of equipment has left the user's hands.

Preferably said motion-sensing means is arranged to measure the speed of the portable electronic equipment after said transient motion and to generate said output signal in dependence upon said measured speed.

A slow speed (indicative of low-frequency and/or low-amplitude vibration for example) is unlikely to result in impact damage or even in release of the equipment from the user's hands whereas a high speed is likely to be associated with both release of the equipment from the user's hands and considerable impact damage on landing.

In one embodiment said motion-sensing means is arranged to generate said output signal in dependence upon the acceleration and time differential of acceleration of the portable electronic equipment.

Further preferred features are defined in the dependent claims. s

Although, as noted above, modern electronic compact cameras have very short start- up times, even a very short start-up time is unsatisfactory to a degree and in any case it is hardly possible to avoid the delay associated with pressing a button to turn on the camera. Great efforts have been made by camera manufacturers to reduce this to lo a minimum. However it is still necessary for the user to press a button to switch on the camera before moving the same finger to the shutter release button and these actions alone take an appreciable time and distract the user.

In another aspect the invention provides an activating system for portable electronic IS equipment comprising acceleration-sensing means arranged to generate an output signal indicative of an intended use, and activating means responsive to said output signal when the portable electronic equipment is in a standby state to activate the portable electronic equipment in advance of use.

Normally a camera user lifts the camera to eye level from about waist level when taking a picture and a large movement of this sort can be detected while the camera is in a standby state and used eg to extend the camera lens and/or switch on circuitry of the camera while it is still being raised or oriented to its position of intended use.

In one embodiment said acceleration-sensing means is arranged to detect predetermined motion of the portable electronic equipment and generate said output signal in dependence thereon. For example the predetermined motion could be upward movement associated with bringing the camera to eye level.

Preferably said acceleration-sensing means is coupled to processing means arranged to integrate an acceleration signal to detect the velocity and/or translation of the portable electronic equipment and said activating means is responsive to detected velocity and/or translation of predetermined direction and/or amplitude ranges to activate the portable electronic equipment. This feature enables improved as discrimination between movement indicative of intended use and random movement while the camera is being carried. s

In general, there will be a tradeoff between speed of activation (which implies an early decision as to whether a given camera movement is leading to use) and accurate discrimination between such movement and random movement (which will normally require the movement to be nearly completed in order to gain maximum information on which to base a decision).

In a preferred embodiment however, said activating means is arranged, in response to successive output signals generated by or derived from said acceleration-sensing lo means satisfying criteria indicative of intended use, to generate at least one activating signal which in use activates the electronic equipment progressively.

In this manner the speed/accuracy dilemma noted above can be resolved at least to a degree.

Preferably said criteria are different. For example they may be acceleration, speed and translationcriteria respectively. This feature improves discrimination.

In preferred embodiments said acceleration-sensing means comprises at least one inertial sensor. For example the inertial sensor could be a vibratory accelerometer.

Miniature vibratory accelerometers are commercially available at low cost, eg from Analog Devices (eg the Analog Devices ADXL202E dual-axis integrated MEMS accelerometer which is available in a leadless chipcarrier (LCC) package).

2s Preferably said acceleration-sensing means is responsive to acceleration along two or three mutually orthogonal axes.

Preferably said acceleration-sensing means is arranged to generate a vector output signal.

Further preferred features are defined in the dependent claims.

Particularly in its preferred embodiments the present invention enables full advantage to be taken of the quick-acting mechanisms of electronic cameras and as other portable (particularly hand-held) electronic equipment to reconfigure the equipment very rapidly according to circumstances.

Preferred embodiments of the invention are described below by way of example only with reference to Figures 1 to 10 of the accompanying drawings, wherein: s Figure 1 is a schematic block diagram of a camera (shown in side elevation partially in section) in accordance with both aspects of the invention; Figure 2 is a sketch perspective view of the camera of Figure 1 in sequential positions during free fall showing the retraction of its lens unit after being dropped; Figure 3 is a plot of the downward acceleration experienced by and detected within the camera of Figures 1 and 2 during free fall; Figure 4 is a schematic side elevation showing the camera of Figure 1 in sequential 1S positions after being knocked forwardly towards an object and showing the retraction of its lens unit in response; Figures 5A and SB are plots of horizontal acceleration fz and its time differential dfz!dt as experienced by the camera during the sequence of Figure 4; Figure 6 is a flow diagram showing the operation of the microprocessor in the camera of Figure 1 during the free fall condition of Figure 2; Figure 7 is a flow diagram showing the operation of the microprocessor in the 2s camera of Figure 1 to retract the camera lens during the forward knock condition of Figure 3; Figure 8 is a flow diagram showing the further operation of the microprocessor in the camera of Figure 1 to retract the camera lens during a variant of the condition shown in Figure 3 in which the camera is knocked from the user's grasp; Figure 9 is a schematic side elevation showing the movement of the camera of Figure 1 from waist level to eye level immediately prior to use, and as Figure 10 is a flow diagram showing the operation of the microprocessor in the camera of Figure 1 to extend the lens during the movement of Figure 9.

Referring to Figure 1, the digital camera C has a retractable zoom lens unit shown in its fully extended configuration and comprising a first barrel portion B1 which can be telescopically retracted by a first drive motor Ml into a second barrel portion B2.

Second barrel portion B2 is in turn coupled to a second drive motor M2 which can retract both barrel portions into the camera body 1. During the above retraction process, a lens cover P operated by a third drive motor M3 is closed to cover the front lens element. The lens unit (ie barrel portions B1 and B2) can then be extended by a reversal of the retraction process noted above.

The above drive motors are powered by respective motor drive circuits under the control of control signals from a dedicated motor control unit 2, which receives a lens position signal LP in order to provide feedback. Motor control unit 2 also controls focussing of the lens unit under the control of an output signal from a dedicated image processor (ApplicationSpecific Integrated Circuit) 4 which receives an image signal from a conventional CCD detector referenced CCD aligned with the lens unit. Digital images thus obtained are stored in a removable FLASH RAM card.

As descrubed thus far, camera C is entirely conventional, although it is desirable for the drive motors M1 and M2 to be as fast-acting as possible.

In accordance with the invention, a z-axis accelerometer S 1 and an x an y dual axis accelerometer S2 are arranged to sense acceleration along the x, and y and z axes respectively and have outputs coupled to a programmed microprocessor 3 which is provided with a stored program in ROM as well as conventional RAM as shown.

The accelerometers S1 and S2 are suitably monolithic devices similar to the Analog Devices ADXL202E device noted above.

As described below in more detail, the programmed ROM enables detection of and response to i) free fall, ii) a forward shock close to an external surface in which the camera remains in the user's hands and iii) a forward shock in which the camera is knocked hard so that it leaves the user's hands or reaches a high speed (each of cases i) to iii) being indicative of a potential impact) and also iv) a movement indicative of imminent use.

i) free fall Referring to Figures 2 and 6, since the camera C could in principle be dropped in any orientation and this orientation could change during its fall, the x, y and z components of acceleration fx, fy and fz are determined (step 10, Figure 6) squared, summed and the square rooted (step 11, Figure 6) to obtain the acceleration vector f whose magnitude, as shown in Figure 3, will initially approximate to g, approximately 9.8 ms2 and will then tail off slightly due to the effects of air resistance. Accordingly the program sets thresholds of eg O.9g and 1.05g (see Figure lo 3) in order to accommodate the effect of air resistance and also slight local variations in g and if the magnitude of f remains within these thresholds for a short predetermined period eg 0.1 second then f is considered to be approximately equal to g (Figure 6, step 12) and hence the camera to be in free fall. Accordingly the microprocessor 3 (Figure 1) sends signals to the motor control unit 2 to retract the Is lens unit and close the cover P (Figure 6, step 13) as quickly as possible eg in 0. 1 to 0.2 seconds. As shown at C' in Figure 2 this will be sufficiently quick to achieve complete retraction before the camera lands on ground surface S. assuming that the distance is greater than 0.5gt2 where t is the total time taken for sensing of free fall and retraction, eg about 0.2 metres if t is 0.2 seconds or 0.44 metres if t is 0.3 seconds.

ii) forward shock close to external surface Referring to Figure 3, it is assumed that the camera C is a distance z (measured from 2s the front of the lens unit as shown) from an external surface B eg the back of a competing photographer. It is assumed that the user's hand experiences a forward transient impact A 1 (eg as a result of a jolt from another competing photographer) but that the camera remains in the user's grip throughout, as indicated at C'.

As shown in Figure 1, this distance z is made available to microprocessor 3 (eg by the camera's autofocus system, not shown) and as indicated in step 100 of Figure 7, this is differentiated to determine the initial horizontal velocity dz/dt of the camera.

Additionally, as indicated in step loo, the initial horizontal acceleration fz is determined. as

As indicated at step 120 the time t of impact against surface B can then be determined (from the formula z = t.dz/dt + 0.5fz t2) and if (step 140) this is not later than a threshold period (corresponding to the time taken for the drive motors to retract the lens unit plus a margin for error) the microprocessor 3 (Figure 1) instructs the motor control unit 2 to retract the lens unit (step 13, Figure 7).

As indicated at C' in Figure 3, the lens unit is retracted before impact.

It should be noted that the above procedure is somewhat conservative because the simple calculation of impact time t assumes that the acceleration is constant whereas lo in practice it is likely to decrease.

Furthermore in a variant the distance signal z could be obtained by integration of the acceleration signal fz rather than from the autofocus system. In a further, much less preferred variant the acceleration sensors S 1 and S2 could be dispensed with and the calculation of impact time in step 120 could be based on the z signal from the autofcus system, and dz/dt and d2z/dt2 as derived from z. iiiN forward shock leading to release from user's hands or laugh aped This situation corresponds to a variant of the Figure 3 situation in which the camera at C'is not necessarily close to an external surface but is either in free flight (having left the user's hands) or is moving at high forward velocity such that it is likely to be out of the control of the user. The procedure shown in Figure 8 detects the free flight or loss of control and does not rely on the proximity or otherwise of surface B since the mere fact of loss of control or even release from the user's hands will probably result in an impact for which protection is required.

Initially (step 100, Figure 8) the acceleration signal fz is acquired and it is then determined (step 200) whether this exceeds a predetermined threshold. This step eliminates from consideration small movements that would be normally experienced by the camera when it is carried from eg the user's neck. If the threshold is not exceeded, then an impact is assumed to be unlikely and the procedure returns to step 100. If fz exceeds the threshold (indicative of a significant acceleration potentially resulting in a damaging impact) then the rate of change dfz/dt of fz is calculated (step 300). If this horizontal acceleration fz declines to zero then it is concluded (step 400) that the camera is not acted upon by either a forward or a rearward force and has therefore left the user's hands. Hence the lens unit is retracted (step 16).

If the forward acceleration has not reached zero but nevertheless has started to decrease, as indicated by dfz/dt decreasing through zero (step 450) it is concluded s that the camera is still in the user's hands which are applying a restraining (rearward) force. In order to determine whether this restraining force is sufficient to control the forward motion of the camera, in step 500 at time t500 the acceleration fz is integrated since the time t300 of step 300, to obtain a forward velocity signal.

0 If this forward velocity exceeds a safe threshold within a given timeout period (step 550) the lens unit is retracted (step 16).

It will be appreciated that since each of the processes of Figures 6, 7 and 8 are run essentially simultaneously, most of the camera movements likely to result in an impact will be detected and will result in rapid retraction of the lens unit B1, B2 within the camera body 1. Preferably the camera body is provided with internal or external shock-absorbers in order to enable the camera to survive moderate impacts with the lens unit retracted.

Other protective measures besides retraction of the lens unit (and associated closing of the lens cover) can be envisaged, including electromechanical disengagement of the drive motors from the lens unit to allow it to move freely back into the camera body on impact, but these will require re-design of the lens drive system and may not be so costeffective.

In a further variant of the embodiment of Figure 1, the accleration sensors S1 and S2 could be supplemented or even replaced by orientation sensors which would detect eg tumbling motion of the camera indicative of free fall, or sudden rotation indicative of a knock and hence a likely imminent impact. This varant is however less preferred.

The final embodiment relates to the second aspect of the invention.

iv) mveme indicative of imminese Referring to Figure 9, it is assumed that at time tlloo the camera C is initially in standby mode (with only the accelerometer sensors S1 and S2 and their associated microprocessor 3 switched on) and hence with minimal power drain on the camera's battery. It is assumed that the camera is supported (eg by a neckstrap) at slightly above waist height in front of the user's midriff U. In this mode the lens unit is s retracted as shown. The acceleration components fy and fz are measured continually. This condition is indicated by step 1000 of Figure 10.

The user then sees a suitable subject for a photograph and raises the camera with an initial acceleration fAcT which is calculated in step 1100. In step 1200 it is lo determined whether this acceleration is in defined amplitude and direction ranges in the yz plane. For example a forward jog from the user's midriff would be excluded from these defined ranges.

If these criteria are satisfied the camera circuits are powered up and the motor IS control circuit is prepared to extend the lens unit (step 1300). The camera is then moved with a changing velocity L to a position C' (Figure 9) at about eye level at which the user wishes to take a photograph. Accordingly the acceleration fAcT is integrated over a period corresponding to about half this movement, up to time tl400 (step 1400, Figure 10). A timeout step 1500 is included to limit the integration period.

If the resulting velocity vector v has an amplitude within a defined range and a direction within a defined range (step 1600) then this velocity is integrated and checked to see if the resulting movement is in a defined amplitude and direction range (eg as indicated by angle in Figure 9) in which case the lens unit is extended (step 1700).

The direction ranges specified in steps 1100, 1400 and 1600 for defining camera motion indicative of likely intended use need not be identical but indeed should preferably be siiccessively narrower, since the direction of initial acceleration fAcT is less critical than the direction of the velocity vector v which in turn is less critical than the final position of the camera C' relative to its initial position C. In a simplified embodiment the acceleration and velocity criteria utilised in steps 1200 and 1600 could be dispensed with. as

In a further variant the camera could include rotation sensors instead of or in addition to acceleration sensors in order to detect changes in orientation indicative of intended use. s

Claims

Clai,ms 1. A protective system for portable electronic equipment

comprising motion-sensing means arranged to generate an output signal indicative of a potential impact, and protective means responsive to said output signal to configure the portable electronic equipment to a protected state in advance of such an impact.
2. A protective system according to claim 1 wherein said motion-sensing means is arranged to detect unconstrained motion of the portable electronic equipment and lo generate said output signal in dependence thereon.
3. A protective system according to claim 2 wherein said motion-sensing means is arranged to detect free fall of the portable electronic equipment.

IS
4. A protective system according to any preceding claim wherein said motion- sensing means is arranged to detect transient motion of the portable electronic equipment and to generate said output signal in dependence thereon.
5. A protective system according to claim 4 wherein said motion-sensing means is arranged to detect a change in acceleration to a substantially constant acceleration of the portable electronic equipment and to generate said output signal in dependence thereon.
6. A protective systen according to claim 4 or claim 5 wherein said motion-sensing 2s means is arranged to measure the speed of the portable electronic equipment after said transient motion and to generate said output signal in dependence upon said measured speed.
7. A protective system according to any of claims 4, 5 and 6 wherein said motion sensing means is arranged to generate said output signal in dependence upon the acceleration and time differential of acceleration of the portable electronic equipment.
8. A protective system according to any preceding claim comprising distance 3s sensing means arranged to detect proximity of the portable electronic equipment to an external surface, said protective means being responsive to a combination of the output signal from said motion-sensing means and a further output signal from said distance-sensing means to configure the portable electronic equipment to said protected state.

s
9. A protective system according to claim 8, which is arranged to calculate the time period before impact against said surface in dependence upon the speed and acceleration of the portable electronic equipment towards said surface and to configure the portable electronic equipment to said protected state if said time period is below a threshold value.
10. A protective system according to any preceding claim wherein said motion sensing means comprises at least one inertial sensor.
11. A protective system according to claim 10 wherein said at least one inertial IS sensor is a vibratory accelerometer.
12. A protective system according to any preceding claim wherein said motion sensing means is responsive to acceleration along two or three mutually orthogonal axes.
13. A protective system according to claim 12 wherein said motion-sensing means is arranged to generate a vector output signal.
14. Portable electronic equipment incorporating a protective system according to 2s any preceding claim.
15. Portable electronic equipment according to claim 14 which is a camera having a retractable lens and wherein said protective means includes means for retracting said lens in advance of said potential impact.
16. Portable electronic equipment according to claim 14 or claim 15 which is a camera having a powered lens cover and wherein said protective means includes means for covering the camera lens with said lens cover in advance of said potential impact. as
17. Portable electronic equipment according to claim 14 which is a mobile communications device or a portable computing device.
18. An activating system for portable electronic equipment comprising acceleration- sensing means arranged to generate an output signal indicative of an intended use, and activating means responsive to said output signal when the portable electronic equipment is in a standby state to activate the portable electronic equipment in advance of use.
19. An activating system according to claim 18 wherein said accelerationsensing lo means is arranged to detect predetermined motion of the portable electronic equipment and generate said output signal in dependence thereon.
20. An activating system according to claim 18 or claim 19 wherein said acceleration-sensing means is coupled to processing means arranged to integrate an acceleration signal to detect the velocity and/or translation of the portable electronic equipment and said activating means is responsive to detected velocity and/or translation of predetermined direction and/or amplitude ranges to activate the portable electronic equipment.
21. An activating system according to any of claims 18 to 20 wherein said activating means is arranged, in response to successive output signals generated by or derived from said acceleration-sensing means satisfying criteria indicative of intended use, to generate at least one activating signal which in use activates the electronic equipment progressively. 2s
22. An activating system according to claim 21 wherein said criteria are different.
23. An activating system according to claim 22 wherein said different criteria are two or more of accleration, speed and translation criteria respectively.
24. An activating system according to any of claims 18 to 23 wherein said acceleration-sensing means comprises at least one inertial sensor.
25. An activating system according to claim 24 wherein said at least one inertial sensor is a vibratory accelerometer. t
26. An activating system according to any of claims 18 to 25 wherein said acceleration-sensing means is responsive to acceleration along two or three mutually orthogonal axes.
27. A protective system according to claim 26 wherein said accelerationsensing means is arranged to generate a vector output signal.
28. Portable electronic equipment incorporating an activating system according to any of claims 18 to 27.
29. Portable electronic equipment according to claim 28 which is a camera having a retractable lens and wherein said activating means includes means for extending said lens in advance of said intended use.
30. Portable electronic equipment according to claim 28 which is a mobile communications device or a portable computing device.

3 l. A camera substantially as described hereinabove with reference to Figures I, 2, 3 and 7 or Figures 1, 3 and 6 or Figures 1, 3, SA, SB and 8 or Figures 1,9 amd 10 of the accompanying drawings. as