EP0332169A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Image shake detecting device
Assignee: Canon Inc
•
Filing: 1989-03-08
•
Granted: —
•
Expires: 2009-03-08
Abstract
Abstract An image shake detecting device for detecting a shake of an image on an image sensing plane on the basis of a video signal output from an image sensor (2) includes detection circuits (9) arranged to detect image displacement in a plurality of areas set on the image sensing plane, and a control microcomputer which makes a discrimination, on the basis of information output from these detection circuits, between a movement of a camera and a solo movement of a photographed object. The device thus accurately makes compensation for an image shake by judging the state of the image on the basis of information output from these detection circuits. The image shake detecting device further includes a computing circuit arranged to compute a quantity of an image shake on the basis of a difference in detecting timing of a feature point of the image and a sensitivity control circuit arranged to change the detection sensitivity of the shake detection circuits. Further disclosed is an object tracing device to which the invented image shake detecting device is applied.
Inventors
- 👤 Masayoshi Sekine
- 👤 Toshiyuki Nakajima
- 👤 Takashi Kai
- 👤 Katsuji Yoshimura
- 👤 Masamichi Toyama
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 17:38
CPC Classifications
G; G01; G01S; G01S3/00; G01S3/78; G01S3/782; G01S3/785; G01S3/786; G01S3/7864; G06; G06T; G06T7/00; G06T7/20; G06T7/223; H; H04; H04N; H04N23/00; H04N23/60; H04N23/61; H04N23/67; H04N23/673; H04N23/68; H04N23/681; H04N23/6811; H04N23/6815; H04N23/682; H04N23/685; H04N23/686; H04N23/687; H04N5/00; H04N5/14; H04N5/144; H04N5/145; G03; G03B; G03B2217/00; G03B2217/005; G06T2207/00; G06T2207/10; G06T2207/10016
Claims Analysis
Total Claims: 84
Claim 1
Independent Claim
140 words
An image shake detecting device for detecting a shake of an image on an image sensing plane on the basis of an image signal output from image sensing means, comprising: a) first detection means for detecting the displacement of the image on the basis of an image signal corresponding to a first detection area set on said image sensing plane; b) second detection means for detecting the displacement of the image on the basis of an image signal corresponding to a second detection area set on said image sensing plane; c) switching means for selecting one of said first detection means and said second detection means; and d) image shake detecting means for computing the shake of the image on the basis of an output of said first detection means or said second detection means selected by said switching means.
Claim 2
Dependent Claim
140 words
An image shake detecting device for detecting a shake of an image on an image sensing plane on the basis of an image signal output from image sensing means, comprising: a) first detection means for detecting the displacement of the image on the basis of an image signal corresponding to a first detection area set on said image sensing plane; b) second detection means for detecting the displacement of the image on the basis of an image signal corresponding to a second detection area set on said image sensing plane; c) switching means for selecting one of said first detection means and said second detection means; and d) image shake detecting means for computing the shake of the image on the basis of an output of said first detection means or said second detection means selected by said switching means.
Claim 3
Dependent Claim
60 words
A device according to claim 1, further comprising: a) compensating means for displacing an optical axis of a photo-taking optical system which forms an image from an incident light on an imaging plane of said image sensing means; and b) driving control means for driving said compensating means on the basis of an output of said image shake detecting means.
Claim 4
Dependent Claim
70 words
A device according to claim 2, wherein said compensating means is a variable apex-angle prism inserted in said photo-taking optical system, and wherein said driving control means is arranged to vary an apex angle of said variable apex-angle prism in the direction of decreasing a quantity of the shake of the image on the basis of information on the shake of the image output from said image shake detecting means.
Claim 5
Dependent Claim
40 words
A device according to claim 3, wherein said first detection area is an area set approximately in a central part of said image sensing plane, and wherein said second detection area is an area located around said first detection area.
Claim 6
Dependent Claim
46 words
A device according to claim 4, wherein an image located within said first detection area corresponds to a main object image in said image sensing plane, and wherein said second detection area corresponds to a background of said main object image in said image sensing plane.
Claim 7
Dependent Claim
98 words
A device according to claim 5, wherein each of said first and second detection means is arranged to obtain the center of gravity of an image from a histogram formed by converting a luminance level of the image signal into a binary value and to compute a movement vector of an image on the basis of a movement quantity of said center of gravity in a plurality of images obtained at intervals of a predetermined period of time, and wherein said driving control means is arranged to control said compensating means on the basis of said movement vector.
Claim 8
Dependent Claim
62 words
A device according to claim 4, wherein said image shake detecting means has a first mode in which a shake of an image is detected on the basis of detection information obtained from said first detection area and a second mode in which a shake of an image is detected on the basis of detection information obtained from said second detection area.
Claim 9
Dependent Claim
24 words
A device according to claim 7, wherein said switching means includes means for manually selecting one of said first mode and said second mode.
Claim 10
Dependent Claim
24 words
A device according to claim 7, wherein said switching means includes means for automatically selecting one of said first mode and said second mode.
Claim 11
Dependent Claim
68 words
A device according to claim 9, wherein said image shake detecting means includes means for detecting a predetermined signal component corresponding to a sharpness in the image signal obtained from each of said first and second detection areas, and wherein said switching means is arranged to select one of said first and second detection areas which is greater in a quantity of detection of said predetermined signal component.
Claim 12
Dependent Claim
46 words
A device according to claim 10, wherein said image shake detecting means is arranged to stop performing an image shake detecting action thereof when the quantity of detection of said predetermined signal component in said first or second detection area is less than a predetermined level.
Claim 13
Dependent Claim
20 words
A device according to claim 11, wherein said predetermined signal component is a high-frequency component included in the image signal.
Claim 14
Dependent Claim
20 words
A device according to claim 12, wherein said predetermined signal component is an edge component included in said image signal.
Claim 15
Dependent Claim
163 words
An image shake detecting device for detecting a shake of an image on an image sensing plane on the basis of an image signal output from image sensing means, comprising: a) movement detecting means for detecting the displacement of the image on the basis of an image signal corresponding to a predetermined detection area set on said image sensing plane; b) compensating means for compensating for a movement of the image, by displacing an optical axis of a photo-taking optical system which images an incident light on an imaging plane of said image sensing means, on the basis of information on the displacement of the image output from said movement detecting means; c) sharpness detecting means for detecting a signal component indicative of a sharpness of the image on the basis of an image signal corresponding to said detection area; and d) control means for controlling an action of said compensating means on the basis of an output of said sharpness detecting means.
Claim 16
Dependent Claim
163 words
An image shake detecting device for detecting a shake of an image on an image sensing plane on the basis of an image signal output from image sensing means, comprising: a) movement detecting means for detecting the displacement of the image on the basis of an image signal corresponding to a predetermined detection area set on said image sensing plane; b) compensating means for compensating for a movement of the image, by displacing an optical axis of a photo-taking optical system which images an incident light on an imaging plane of said image sensing means, on the basis of information on the displacement of the image output from said movement detecting means; c) sharpness detecting means for detecting a signal component indicative of a sharpness of the image on the basis of an image signal corresponding to said detection area; and d) control means for controlling an action of said compensating means on the basis of an output of said sharpness detecting means.
Claim 17
Dependent Claim
54 words
A device according to claim 14, wherein said compensating means is a variable apex-angle prism inserted in a photo-taking optical system, which is arranged to vary an apex angle thereof in the direction of decreasing a quantity of the shake of the image in accordance with said information on the displacement of the image.
Claim 18
Dependent Claim
44 words
A device according to claim 14, wherein said movement detecting means is arranged to detect the displacement of the image in a first area set approximately in a central part of said image sensing plane and a second area located around said first area.
Claim 19
Dependent Claim
38 words
A device according to claim 16, wherein an image located within said first area corresponds to a main object image in said image sensing plane, and wherein said second area corresponds to a background of said main object.
Claim 20
Dependent Claim
93 words
A device according to claim 17, wherein said movement detecting means is arranged to obtain the center of gravity of an image from a histogram formed by converting into a binary value a luminance level of the image signal and to compute a movement vectors of an image on the basis of a movement quantity of said center of gravity in a plurality of images obtained at intervals of a predetermined period of time, and wherein said control means is arranged to control said compensating means on the basis of said movement vector.
Claim 21
Dependent Claim
59 words
A device according to claim 17, wherein said movement detecting means has a first mode in which a shake of an image is detected on the basis of detection information obtained from said first area and a second mode in which a shake of an image is detected on the basis of detection information obtained from said second area.
Claim 22
Dependent Claim
24 words
A device according to claim 19, wherein said control means includes switching means for selecting one of said first mode and said second mode.
Claim 23
Dependent Claim
24 words
A device according to claim 20, wherein said switching means includes means for manually selecting one of said first mode and said second mode.
Claim 24
Dependent Claim
24 words
A device according to claim 20, wherein said switching means includes means for automatically selecting one of said first mode and said second mode.
Claim 25
Dependent Claim
32 words
A device according to claim 22, wherein said control means is arranged to select one of said first and second areas which is greater in an output of said sharpness detecting means.
Claim 26
Dependent Claim
36 words
A device according to claim 14 or 20, wherein said control means is arranged to stop an action of said compensating means when the output of said sharpness detecting means is less than a predetermined value.
Claim 27
Dependent Claim
31 words
A device according to claim 14, wherein said sharpness detecting means is arranged to detect a sharpness on the basis of a quantity of a high-frequency component of the image signal.
Claim 28
Dependent Claim
17 words
A device according to claim 25, wherein said sharpness is an edge component of the image signal.
Claim 29
Dependent Claim
101 words
An image shake detecting device for detecting a shake of an image on an image sensing plane on the basis of an image signal output from image sensing means, comprising: a) extracting means for extracting a feature point from within said image sensing plane; b) detection means for detecting a difference in generation timing of said feature point between a plurality of temporally different images; c) computing means for computing a quantity of the shake of the image on the basis of an output of said detection means; and d) sensitivity control means for varying a sensitivity of said detection means.
Claim 30
Dependent Claim
101 words
An image shake detecting device for detecting a shake of an image on an image sensing plane on the basis of an image signal output from image sensing means, comprising: a) extracting means for extracting a feature point from within said image sensing plane; b) detection means for detecting a difference in generation timing of said feature point between a plurality of temporally different images; c) computing means for computing a quantity of the shake of the image on the basis of an output of said detection means; and d) sensitivity control means for varying a sensitivity of said detection means.
Claim 31
Dependent Claim
32 words
A device according to claim 27, further comprising compensating means for compensating for the shake of the image on the basis of a result of a computing operation of said computing means.
Claim 32
Dependent Claim
35 words
A device according to claim 28, wherein said compensating means is a variable apex-angle prism for compensating an optical axis of a photo-taking optical system which forms an object image on said image sensing means.
Claim 33
Dependent Claim
45 words
A device according to claim 27, wherein said extracting means is arranged to extract a feature point from a signal pattern obtained by converting into a binary value an edge component of a luminance component of the image signal output from said image sensing means.
Claim 34
Dependent Claim
45 words
A device according to claim 27, wherein said detection means includes clock pulse generating means and is arranged to detect the difference in generation timing of said feature point between temporally different field images by counting clock pulses generated by said clock pulse generating means.
Claim 35
Dependent Claim
33 words
A device according to claim 31, wherein said computing means is arranged to compute the quantity of the shake of the image on the basis of a counted number of said clock pulses.
Claim 36
Dependent Claim
30 words
A device according to claim 32, further comprising area setting means for extracting an area having a movement on said image sensing plane to designate an image shake detection area.
Claim 37
Dependent Claim
78 words
A device according to claim 33, wherein said area setting means is arranged to divide said image sensing plane into an m X n number of blocks, to detect a movement part of said image sensing plane having a local image movement by comparing binary signals of a luminance level in each of said blocks between a plurality of temporally different images, and to designate an area other than said movement part as said image shake detection area.
Claim 38
Dependent Claim
27 words
A device according to claim 34, wherein said sensitivity control means is arranged to control a sensitivity of said detection means by varying a clock signal frequency.
Claim 39
Dependent Claim
33 words
A device according to claim 35, wherein said sensitivity control means is arranged to lower the sensitivity at said movement part and to raise the sensitivity at a part having not much movement.
Claim 40
Dependent Claim
32 words
A device according to claim 36, wherein said sensitivity control means is arranged to vary stepwise the sensitivity of said detection means in each of said m X n number of blocks.
Claim 41
Dependent Claim
109 words
An image shake detecting device comprising: a) scanning means for scanning at the same speed a plurality of images obtained at intervals of a predetermined period of time; b) detection means for detecting a time difference between said plurality of images in timing at which corresponding points of feature are generated during a scanning process of said scanning means, by counting the number of clock pulses; c) computing means for detecting a quantity of a shake of an image by computing an output of said detection means; and d) sensitivity control means for varying a detection sensitivity of said detection means by changing a period of said clock pulses.
Claim 42
Dependent Claim
109 words
An image shake detecting device comprising: a) scanning means for scanning at the same speed a plurality of images obtained at intervals of a predetermined period of time; b) detection means for detecting a time difference between said plurality of images in timing at which corresponding points of feature are generated during a scanning process of said scanning means, by counting the number of clock pulses; c) computing means for detecting a quantity of a shake of an image by computing an output of said detection means; and d) sensitivity control means for varying a detection sensitivity of said detection means by changing a period of said clock pulses.
Claim 43
Dependent Claim
32 words
A device according to claim 38, further comprising compensating means for compensating for the quantity of the shake on the basis of a result of a computing operation of said computing means.
Claim 44
Dependent Claim
34 words
A device according to claim 39, wherein said compensating means is a variable apex-angle prism for compensating an optical axis of a photo-taking optical system which forms an object image on image sensing means.
Claim 45
Dependent Claim
30 words
A device according to claim 39, wherein said computing means is arranged to compute the quantity of the shake on the basis of a counted number of said clock pulses.
Claim 46
Dependent Claim
30 words
A device according to claim 41, further comprising area setting means for extracting an area having a movement on an image sensing plane to designate an image shake detection area.
Claim 47
Dependent Claim
77 words
A device according to claim 42, wherein said area setting means is arranged to divide said image sensing plane into an m X n number of blocks, to detect a movement part of said image sensing plane having a local movement by comparing, between a plurality of temporally different images, binary signals of a luminance level in each of said blocks, and to designate an area other than said movement part as said image shake detection area.
Claim 48
Dependent Claim
28 words
A device according to claim 43, wherein said sensitivity control means is arranged to control a detection sensitivity of said detection means by varying a clock signal frequency.
Claim 49
Dependent Claim
33 words
A device according to claim 44, wherein said sensitivity control means is arranged to lower the sensitivity at said movement part and to raise the sensitivity at a part having not much movement.
Claim 50
Dependent Claim
32 words
A device according to claim 45, wherein said sensitivity control means is arranged to vary stepwise the sensitivity of said detection means in each of said m X n number of blocks.
Claim 51
Dependent Claim
102 words
A control device for an image sensing optical system, comprising: a) first control means for feedback-controlling said image sensing optical system on the basis of detection information obtained by timewise dispersively detecting a state of said image sensing optical system; b) memory means for storing control information obtained on the basis of a quantity of control performed over said image sensing optical system when said detection information is sampled; and c) second control means for controlling said image sensing optical system on the basis of a result obtained by computing said control information stored in said memory means and said detection information.
Claim 52
Dependent Claim
102 words
A control device for an image sensing optical system, comprising: a) first control means for feedback-controlling said image sensing optical system on the basis of detection information obtained by timewise dispersively detecting a state of said image sensing optical system; b) memory means for storing control information obtained on the basis of a quantity of control performed over said image sensing optical system when said detection information is sampled; and c) second control means for controlling said image sensing optical system on the basis of a result obtained by computing said control information stored in said memory means and said detection information.
Claim 53
Dependent Claim
23 words
A device according to claim 47, further comprising a compensating optical system for varying an optical axis of said image sensing optical system.
Claim 54
Dependent Claim
53 words
A device according to claim 48, wherein said detection information represents a quantity of a shake of said image sensing optical system, and wherein said first control means is arranged to compensate for a state of said compensating optical system to decrease the quantity of the shake in accordance with said detection information.
Claim 55
Dependent Claim
27 words
A device according to claim 49, wherein said compensating optical system is a variable apex-angle prism for varying the optical axis of said image sensing optical system.
Claim 56
Dependent Claim
29 words
A device according to claim 50, wherein said memory means is arranged to store a quantity of a control over said compensating optical system for compensation of the shake.
Claim 57
Dependent Claim
35 words
A device according to claim 51, wherein said second control means is arranged to supply a previous quantity of a control stored in said memory means to a control loop of said first control means.
Claim 58
Dependent Claim
44 words
A device according to claim 52, wherein said first control means is arranged to control said compensating optical system on the basis of a value obtained by adding current detection information to the previous quantity of the control supplied from said second control means.
Claim 59
Dependent Claim
25 words
A device according to claim 53, wherein said second control means includes means for multiplying information stored in said memory means by a predetermined coefficient.
Claim 60
Dependent Claim
36 words
A device according to claim 54, wherein a detecting period of said detection information and a period of said control are set at a value which is an integer times as much as one field period.
Claim 61
Dependent Claim
28 words
A device according to claim 54, wherein the quantity of the control stored in said memory means is a quantity of an actual operation of a controlled system.
Claim 62
Dependent Claim
93 words
A feedback control device comprising: a) a first control system for feedback-controlling a controlled system on the basis of detection information obtained by timewise dispersively detecting a state of said controlled system; b) memory means for storing control information based on a quantity of a control over said controlled system when said detection information is sampled; and c) a second control system for performing a compensating action on said first control system on the basis of a result obtained by computing said detection information and said control information stored in said memory means.
Claim 63
Dependent Claim
93 words
A feedback control device comprising: a) a first control system for feedback-controlling a controlled system on the basis of detection information obtained by timewise dispersively detecting a state of said controlled system; b) memory means for storing control information based on a quantity of a control over said controlled system when said detection information is sampled; and c) a second control system for performing a compensating action on said first control system on the basis of a result obtained by computing said detection information and said control information stored in said memory means.
Claim 64
Dependent Claim
35 words
A device according to claim 57, wherein said second control system is arranged to supply a previous quantity of a control stored in said storing means to a control loop of said first control system.
Claim 65
Dependent Claim
51 words
A device according to claim 58, wherein said first control system is arranged to control said controlled system on the basis of a value obtained by adding a quantity of a control based on a current detection information to the previous quantity of the control supplied from said second control system.
Claim 66
Dependent Claim
25 words
A device according to claim 59, wherein said second control system includes means for multiplying information stored in said memory means by a predetermined coefficient.
Claim 67
Dependent Claim
102 words
An image processing device comprising: a) movement vector detecting means for detecting a movement vector of an image in each of detection blocks formed by dividing an image sensing plane; b) computing means for detecting a distributed state of an image movement within said image sensing plane by statistically processing the movement vector obtained from each of said detection blocks; and c) area discriminating means for detecting an area in which a main object to be photographed is located or an area in which a background of said main object is located, on the basis of an output of said computing means.
Claim 68
Dependent Claim
102 words
An image processing device comprising: a) movement vector detecting means for detecting a movement vector of an image in each of detection blocks formed by dividing an image sensing plane; b) computing means for detecting a distributed state of an image movement within said image sensing plane by statistically processing the movement vector obtained from each of said detection blocks; and c) area discriminating means for detecting an area in which a main object to be photographed is located or an area in which a background of said main object is located, on the basis of an output of said computing means.
Claim 69
Dependent Claim
47 words
A device according to claim 61, wherein said movement vector detecting means is arranged to obtain said movement vector in each of said detection blocks on the basis of a luminance variation in each of said detection blocks on said image sensing plane between temporally different fields.
Claim 70
Dependent Claim
67 words
A device according to claim 62, wherein said computing means is arranged to obtain a distribution of movement vectors by preparing a histogram of movement vectors in said detection blocks in reference to a coordinate axis set on said image sensing plane, and to detect an area having an image movement above a predetermined threshold value and an area having an image movement below said threshold value.
Claim 71
Dependent Claim
51 words
A device according to claim 63, wherein said area discriminating means is arranged to determine said area having an image movement above said predetermined threshold value to by a position of an object to be photographed and said area having an image movement below said threshold value to be a background.
Claim 72
Dependent Claim
90 words
A device according to claim 64, further comprising: d) image shake detecting means for detecting a shake of an image on said image sensing plane on the basis of movement vectors in an area determined by said area discriminating means; e) compensating means for displacing an optical axis of an optical system which images an incident light on said image sensing plane; and f) control means for compensating for a shake of an image by controlling said compensating means in accordance with an output of said image shake detecting means.
Claim 73
Dependent Claim
15 words
A device according to claim 65, wherein said compensating means is a variable apex-angle prism.
Claim 74
Dependent Claim
53 words
A device according to claim 65, wherein said control means is arranged to determine said area having an image movement below said predetermined threshold value and corresponding to a background to be an image shake detection area, and to control said compensating means on the basis of the movement vectors in said area.
Claim 75
Dependent Claim
25 words
A device according to claim 64, wherein said area having an image movement above said predetermined threshold value is used as an object tracing area.
Claim 76
Dependent Claim
132 words
An automatic focusing device comprising: a) focus detecting means for detecting a degree of focusing on an object in an image sensing plane to make focus adjustment; b) movement vector detecting means for detecting a movement vector of an image obtained within each of detection blocks formed by dividing said image sensing plane; c) area detecting means for detecting an area having an image of the object by computing the movement vectors in said detection blocks to determine said area as a focus detection area; and d) control means for detecting a movement quantity of the image of the object on the basis of said movement vectors in said focus detection area detected by said area detecting means and for controlling said focus detecting means on the basis of said movement quantity.
Claim 77
Dependent Claim
132 words
An automatic focusing device comprising: a) focus detecting means for detecting a degree of focusing on an object in an image sensing plane to make focus adjustment; b) movement vector detecting means for detecting a movement vector of an image obtained within each of detection blocks formed by dividing said image sensing plane; c) area detecting means for detecting an area having an image of the object by computing the movement vectors in said detection blocks to determine said area as a focus detection area; and d) control means for detecting a movement quantity of the image of the object on the basis of said movement vectors in said focus detection area detected by said area detecting means and for controlling said focus detecting means on the basis of said movement quantity.
Claim 78
Dependent Claim
47 words
A device according to claim 69, wherein said movement vector detecting means is arranged to obtain the movement vectors in each of said detection blocks on the basis of a luminance variation in each of said detection blocks on said image sensing plane between temporally different fields.
Claim 79
Dependent Claim
68 words
A device according to claim 70, wherein said area detecting means is arranged to obtain a distribution of movement vectors by preparing a histogram of movement vectors in said detection blocks in reference to a coordinate axis set on said image sensing plane, and to detect an area having an image movement above a predetermined threshold value and an area having an image movement below said threshold value.
Claim 80
Dependent Claim
51 words
A device according to claim 71, wherein said area detecting means is arranged to determine said area having an image movement above said predetermined threshold value to be an object position or a focus detection area and said area having an image movement below said threshold value to be a background.
Claim 81
Dependent Claim
39 words
A device according to claim 70 or 72, wherein said control means is arranged to operate said focus detecting means when the movement quantity of the image of the object in said focus detection area exceeds a predetermined value.
Claim 82
Dependent Claim
38 words
A device according to claim 73, wherein said control means is arranged to detect a change in a distance to an object on the basis of the magnitude of divergence of movement vectors in said focus detection area.
Claim 83
Dependent Claim
160 words
An automatic focusing device comprising: a) focus detecting means for detecting a degree of focusing on an object in an image sensing plane on the basis of a high-frequency component of an image signal output from image sensing means to make focus adjustment; b) movement vector detecting means for detecting a movement vector of an image in each of detection blocks formed by dividing said image sensing plane; c) area detecting means for detecting an area having an image of the object on the basis of the magnitude of the movement vector in each of said detection blocks to determine said area to be a focus detection area; and d) control means for detecting a movement quantity of the image of the object by computing a divergence of the movement vector in said focus detection area detected by said area detecting means and for starting to operate said focus detecting means when said movement quantity exceeds a predetermined threshold value.
Claim 84
Dependent Claim
160 words
An automatic focusing device comprising: a) focus detecting means for detecting a degree of focusing on an object in an image sensing plane on the basis of a high-frequency component of an image signal output from image sensing means to make focus adjustment; b) movement vector detecting means for detecting a movement vector of an image in each of detection blocks formed by dividing said image sensing plane; c) area detecting means for detecting an area having an image of the object on the basis of the magnitude of the movement vector in each of said detection blocks to determine said area to be a focus detection area; and d) control means for detecting a movement quantity of the image of the object by computing a divergence of the movement vector in said focus detection area detected by said area detecting means and for starting to operate said focus detecting means when said movement quantity exceeds a predetermined threshold value.
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