GB2253067A

GB2253067A - Blur preventing camera

Info

Publication number: GB2253067A
Application number: GB9203630A
Authority: GB
Inventors: Shigeo Enomoto
Original assignee: Asahi Kogaku Kogyo Co Ltd
Current assignee: Pentax Corp
Priority date: 1991-02-20
Filing date: 1992-02-19
Publication date: 1992-08-26
Also published as: JPH05107622A; GB9203630D0; FR2673021A1; DE4205221A1

Abstract

A blur preventing camera is disclosed which includes a shutter drive mechanism (25, 26) which drives a shutter in response to a signal which is issued when a shutter release switch is turned ON, a camera-shake detector (17, 19, 20) for detecting the angular velocity or angular acceleration of the optical axis of a taking lens as a result of the optical axis displacement caused by camera-shake, a maximum value detecting circuit (21) for detecting an occurrence of a maximum value of the angular velocity or angular acceleration detected by the camera-shake detector (17, 19, 20) and a controller (22) for outputting a release signal to the shutter drive mechanism (25, 26) to release the shutter after the lapse of a predetermined amount of time from the occurrence of the maximum value. <IMAGE>

Description

- Z - L, 2 5 -, -',1 1 BLUR PREVENTING CAMERA The present invention

relates to a camera having a blur preventing means.

This application is related to the commonly assigned application U.S.S.N.577,554, the disclosure of which is expressly incorporated by reference herein.

Upon taking a picture with a camera carried by a photographer, the image of the picture on an image plane tends to blur as a result of camerashake, particularly when a photographer's posture is not stable, an object to be taken is dark so that the shutter speed is low, or a photographer takes a picture while moving. Under such conditions, the image will be streaked and the picture unclear.

Camera-shake can be prevented to some extent by using optical correcting means, for example, by making a lens brighter. or increasing the sensitivity of the film so that the shutter speed may be increased, or by increasing the photographer's skill. However, these are not satisfactory solutions.

In conventional solutions to the prevention of image - 2 blur, the photographer is warned when an image blur might possibly occur by an indicating LED (Light Emitting Diode) or the like, an indication light recommending the.. use of a strobe at slow shutter speeds might be used, the shutter may be locked thereby making it impossible to take a picture, or the shutter speed may be restricted in the slow shutter speed range.

An object of the present invention isto provide a solution to the prevention of image blur without resorting to the conventional solutions mentioned above.

Namely, an object of the present invention is to provide camera in which substantially no image blur takes place even when a deviation or fluctuation of the optical axis due to the camera-shake occurs.

According to the present invention, there is provided a blur preventing camera comprising a shutter drive mechanism which drives a shutter in response to a signal which is issued when a shutter release switch is turned ON, a camera-shake detecting means for detecting a displacement of the optical axis of a taking lens as an angular velocity or an a maximum value detecting means for of a maximum value of the angular acceleration, detecting an occurrence - 3 displacement detected by the camera-shake detecting means when the shutter release switch is turned ON, and a control means for outputting a release signal to the shutter drive mechanism to release the shutter after the lapse of a predetermined amount of time from the occurrence of the maximum value.

With this structure, the film can be exposed without a substantial occurrence of image blur which would otherwise occur due to the camerashake, particularly when the camera is hand-carried by a photographer.

Furthermore, since the present invention does not rely upon an optical correcting solution to prevent image blur, a camera of the present invention can be simply and inexpensively realized.

The camera preferably further comprises a photometering circuit which calculates brightness data of an object to be taken, and an effective shutter exposure time calculating means for calculating an effective shutter exposure time in accordance with the object brightness data.

Preferably, the control means comprises a delay circuit which includes a delay time setting circuit for setting a delay time which varies in accordance with the effective shutter exposure time output from the effective shutter exposure time calculating means.

A maximum value level detecting means is advantageously - 4 additionally provided to detect the maximum value of the displacement of the optical axis.

The control means preferably emits a release prohibition signal to prohibit the releasing of the shutter when the maximum value of the displacement detected by the maximum value level detecting means is above a predetermining upper limit.

The control means preferably further comprises a delay circuit which includes a release lock circuit which sets said predetermined upper limit which is to be compared with the maximum value of the displacement detected by the maximum value level detecting means.

There is advantageously further provided a delay time setting circuit which varies said predetermined lapse time between the occurrence of the maximum value and the output of the release signal in accordance with the maximum value detected by the maximum value level detecting means.

In a preferred embodiment, the camera-shake detecting means detects components of the displacement in two orthogonal directions. In this embodiment, the camera-shake detecting means comprises horizontal and vertical angular velocity sensors which detect the angular velocity applied to the camera in two orthogonal directions.

Preferably, the provision is made of a composite operation circuit for adding the components of the angular velocity in any two orthogonal directions as detected by the camera-shake detecting means.

According to another aspect of the invention, there is provided a blur preventing camera comprising; a shutter drive mechanism which drives a shutter in response to a release signal which is issued when a shutter release switch is turned ON; a camera-shake detecting means for detecting the angular velocity or angular acceleration of the optical axis of a taking lens as a result of the optical axis displacement caused by said camera-shake; a maximum value detecting means for detecting the occurrence of a maximum value of said angular velocity or angular acceleration detected by said camera-shake detecting means when said shutter release switch is turned ON; and, a photometering means for detecting brightness data of an object to be taken; an effective shutter exposure time calculating means for calculating an effective shutter exposure time in accordance with said object brightness data; and, a control means for setting a delay time in accordance with said effective shutter exposure time data output from said effective shutter exposure time calculating means to delay said release signal, said release signal being issued to said shutter drive mechanism for releasing said shutter in accordance with said delay time.

According to a further aspect of the invention, there is provided a blur preventing camera comprising; a shutter drive mechanism which drives a shutter in response to a release signal which is issued when a shutter release switch is turned ON; a camera-shake detecting means for detecting the angular velocity or angular acceleration of the optical axis of a taking lens resulting from the optical axis displacement caused by said camera-shake; a maximum value detecting means for detecting the occurrence of a maximum value of said angular velocity or angular acceleration detected by said camera-shake detecting means when said shutter release switch is turned ON; and, a maximum value level detecting means for detecting said maximum value of said camera-shake; and, a control means for outputting a release prohibition signal to prohibit the releasing of the shutter when said maximum value detected by said maximum value level detecting means is above a predetermined value.

According to a further aspect of the invention, there is provided a blur preventing camera comprising; a shutter drive mechanism which drives a shutter in response to a release signal which is issued when a shutter release switch is turned ON; 7 - a camera-shake detecting means for detecting the angular velocity or angular acceleration of the optical axis of a taking lens as a result of said optical axis displacement caused by said camera-shake; a maximum value detecting means for detecting the occurrence of a maximum value of said angular velocity or angular acceleration detected by said camera-shake detecting means when said shutter release switch is turned ON; and, a maximum value level detecting means for detecting said maximum value of said angular velocity or angular acceleration; and, a delay time setting circuit for setting a delay time which determines the time between the occurrence of said maximum value and the output of said release signal, in accordance with said maximum value detected by said maximum value level detecting means.

Examples of the invention will be described below in detail with reference to the accompanying drawings, in which:- Figure 1 is a perspective view of a blur preventing camera embodying the present invention; Figure 2 is a f irst embodiment of a block diagram of a control system in the blur preventing camera shown in fig. 1; Figures 3 and 4 are time charts showing output waves of a control circuit in the blur preventing camera shown in Fig.

- a - Figure 5 is a block diagram of a control system of a blur preventing camera of a second embodiment of the present invention; Figure 6 is a block diagram of a control system in a blur preventing camera of a third embodiment of the present invention; Figure 7 is a block diagram of a control system in a blur preventing camera of a fourth embodiment of the present invention; and Figure 8 is a diagram showing a relationship between maximum values of an absolute value wave 11 1 AI 11 and the times at which subsequent minimum values appear, using the time - 9 chart of the absolute value wave "JAI" in Fig. 3.

In Figure 1, which embodying the present taking lens barrel 13, a When the shutter button (half step) and a second photometering switch (not shows a blur preventing camera 11 invention, a camera body 12 has a shutter button 15 and a strobe 16. 15 is depressed by a first step step (full step) respectively, a shown) is turned ON and a shutter release switch (not shown) is turned ON to release the shutter. The camera body 12 has therein respective horizontal and vertical angular velocity sensors 17 and 19 which detect the angular velocity of the optical axis oscillation of the taking lens in the horizontal and vertical directions, respectively.

The wave shapes of the outputs of the horizontal and vertical angular velocity sensors 17 and 19 are detected, for example, as shown in Fig. 3. In Fig. 3, "A, " and "A," represent the angular velocities in the horizontal and vertical directions detected by the horizontal and vertical angular velocity sensors 17 and 19, respectively. "JAI" represents an absolute value (magnitude) of the horizontal and vertical angular velocities. Namely, "JAI" is given by the following formula; I A I A X 2 + A 2) I / 2 This value is proportional to the speed of the actual movement of the image on the film plane due to camera-shake. The wave of "JAI" includes many frequency components higher than the angular velocities A, and A,.

The wave troughs of " I A I " represent the minimum values of the speed of the image moving on the film plane, and accordingly, when the shutter is released at a time corresponding to a wavetrouqh of "JAI", after the release switch 15 is depressed, the film can be exposed with minimum displacement of the image on the film plane during exposure.

The inventors of the present invention tested many subjects and found that, although the amplitude of the waveform generated by a subjectfs shaking varied from individual to individual, the time at which the minimum values of the angular velocity magnitude occurred subsequently to the occurrence of maximum values (half-cycle) was predominantly constant from individual to individual. The average frequency of an absolute value wave (full-cycle) as generated by a subject's shaking was determined to be about 20 Hz as can be seen in the probability distribution curve of Fig. 3(d), where Af is the number of subjects. This tendency is effectively utilized in the blur preventing camera of the present invention.

Figure 2 schematically shows a control circuit of the - 11 camera of the present embodiment including the horizontal angular velocity sensor 17, the vertical angular velocity sensor 19, a composite operation circuit 20, a maximum value detecting circuit 21, a delay circuit 22, a photometering circuit 23 for detecting an object distance and an object brightness, an AF drive circuit 24, a shutter drive circuit 25, and a shutter mechanism 26. The shutter drive circuit 25 and the shutter mechanism 26 constitute a shutter driving means.

The horizontal angular velocity sensor 17 and the vertical angular velocity sensor 19 can be any type of device for detecting degree of blur. For example, an angular speed sensor "EYK-G02C" by Matsushita Electronic Components Co., Ltd. (Japan) can be used. This angular speed sensor includes a gyro signal detecting portion having two bimorph cells which are arranged in the shape of a "T", a tuning fork drive circuit, and a signal processing circuit. It detects the angular speed based on the Coriolis force which is produced by the oscillating tuning fork.

The composite operation circuit 20 calculates a resultant vector from the outputs of the angular velocity sensors 17 and 19 to obtain the absolute value "JAI" (see Fig. 3(c)) upon receipt of a release ON signal which is output when the shutter release switch (not shown) is turned ON.

The maximum value detecting circuit 21 detects the occurence of maximum values of the absolute value "]AI" (the wavecrests of JAI 1% in accordance with the angular velocity output from the composite operation circuit 20, and outputs the detection signal.

Upon receipt of the output signal of the maximum value detecting circuit 21, the delay circuit 22 outputs a release signal to the shutter drive circuit 25 at a time at which the minimum value ("G" in Fig. 4) subsequent to the occurrence of the maximum value ("F" in Fig. 4) occurs within the effective exposure time ("H" in Fig. 4).

Upon receipt of a photometering ON signal, which is output when a photometering switch (not shown) is turned ON, the photometering circuit 23 calculates the distance and brightness of an object to be taken. The AF drive circuit 24 then outputs an operation signal to an automatic focus driving mechanism (not shown) and outputs an AF completion signal to the shutter drive circuit 25 after the completion of the focusing operation.

The shutter drive circuit 25 outputs an operation signal to the shutter mechanisra 26 when the release signal from the delay circuit 22 is received.

The shutter mechanism 26 releases the shutter (not shown) upon receipt of the operation signal from the shutter drive circuit 25.

When the shutter button of the blur preventing camera as constructed above is depressed by a first step (half-step) the photometering circuit 23 calculates the object distance and the object brightness. The AF drive circuit 24 then outputs an operation signal to the automatic focusing driving mechanism (not shown) to effect the focusing operation. If camera-shake occurs when the photographer depresses the shutter button by a full step, the horizontal and vertical angular velocity sensors 17 and 19 detect the angular velocity applied to the camera as angular velocity components in orthogonal directions (i.e., the horizontal and vertical directions). The detected signal is input to the composite operation circuit 20 which adds the components which are output from the horizontal and vertical angular velocity sensors 17 and 19 and calculates the absolute value "JAI" thereof.

Contrary to a conventional camera in which the shutter is released immediately after focusing is completed and the shutter button is depressed by a full step, the e'xposure in the camera of the present embodiment is commenced after a predetermined lapse of time following the peak of the angular velocity absolute value (i.e., the point at which the magnitude of the angular velocity is at a maximum, resulting in the greatest degree of blur). The shutter in the camera of the present embodiment is therefore - 14 not immediately released when the shutter button is fully depressed.

The maximum value of the wave "all in Fig. 4, representing the absolute values of the angular velocity output from the composite operation circuit 20, is detected by the maximum value detecting circuit 21, as shown at "b" in Fig. 4. As a result, the release signal is delayed by the delay circuit 22 for a predetermined appropriate amount of time before it is output to the shutter drive circuit 25, as shown at "c" in Fig. 4. The output ("d" in Fig. 4) of the shutter drive circuit 25 is supplied to the shutter mechanism 26, so that the shutter operates, as shown at "e" in Fig. 4, representing the wave of the shutter aperture.

Generally speaking, when the release signal is input, the shutter can not be instantly opened due to the inertia or the overlap arrangement of the sector blades of the shutter, as can be seen at I'&I in Fig. 4. Also, the speed of the opening movement of the shutter is restricted. Consequently, the time I from the input of the release signal to the front end of the effective shutter exposure time H depends on the construction of the shutter drive mechanism, but is at least 5 ms. As can be seen at "A," in Fig. 3(d), a large number of subjects generated an absolute value wave having a frequency in the vicinity of 20 Hz. Therefore, we have 40 half cycles per second corresponding - 15 to the time between the occurrence of the maximum value F of the absolute value wave of the angular velocity and the occurrence of the minimum value G. Accordingly, the probability distribution has a peak value at around 25 ms.

In the illustrated embodiment, since the delay time J of the delay circuit 22 is set so that the above-mentioned ms corresponds to the intermediate time of the effective shutter exposure time after the occurrence of the maximum value of the absolute value wave of the angular velocity, there is a high probability that the minimum value G of the absolute value wave of the angular velocity occurs at the intermediate time of the effective exposure time.

Consequently, the minimum value G occurs within the effective shutter exposure time after the shutter button 15 is fully depressed, so that exposure is effected during minimum of camera motion. This minimizes the occurrence of image blur.

The following discussion will be directed to a second embodiment of the present invention.

In o an ordinary automatic exposure camera, the appropriate effective exposure time varies in accordance with the object brightness, and consequently, the time between the issuance of the release signal ("cl' in Fig. 4) and the intermediate time of the effective shutter exposure time ("ell in Fig. 4) changes. Therefore, to make the - 16 intermediate time of the effective shutter exposure time coincidental with the minimum value ("G" in Fig. 4) of the absolute values of the angular velocity, it is necessary to change the delay time (I1J11 in Fig. 4) of the delay circuit 22 in accordance with the effective shutter exposure time.

The second embodiment is realized by the control circuit shown in Fig. 5, in which an effective shutter exposure time calculation circuit 52 and a delay time setting circuit 50a provided in a delay circuit 50 are provided in addition to the components of the first embodiment shown in Fig. 2.

( b 1 a n k) W The effective shutter exposure time calculation circuit 52 calculates the effective shutter exposure time in accordance with the object brightness (luminance) data calculated by the photometering circuit 23. The delay time setting circuit 50a sets the delay time J in accordance with the effective shutter exposure time data input thereto from the effective shutter exposure time calculating circuit 52.

In the camera of the second embodiment, when the shutter button is depressed by a half step, the photometering circuit 23 calculates the object distance and the object brightness, so that the effective shutter exposure time calculating circuit 52 calculates the effective shutter exposure time in accordance with the object brightness.

Furthermore, the delay time setting circuit 50a of the delay circuit 50 calculates the necessary delay time in accordance with the effective shutter exposure time data.

The operations subsequent to the depressing of the shutter button by a full step are the. same as those in the first embodiment.,. Therefore, in the second embodiment, the undesirable effects of camera-shake upon exposure can be minimized for a wide range of object brightness conditions.

If the maximum absolute value of the angular velocity is extremely high, for example in the case of extreme - 18 camera-shake, the time at which the minimum absolute value of angular velocity occurs subsequent to the occurrence of the maximum absolute value varies widely. Consequently, it is very difficult to definitively determine the delay time which ensures a high probability of the occurrence of the minimum value during the shutter exposure.

To this end, an upper limit of the maximum value can be preset, so that if the maximum value is above the predetermined upper limit the shutter release signal is not issued. The third embodiment, discussed below and illustrated in Fig. 6 is focused on this feature.

The control circuit shown in Fig. 6 has a maximum value level detecting circuit 60 and a release lock circuit 50b provided in the delay circuit 50, in addition to the components of the first embodiment shown in Fig. 2.

The maximum value level detecting circuit 60 detects the level of the maximum absolute value "JAI" from the composite operation circuit 20 and outputs the detected level to the delay circuit 50.

Thelrelease lock circuit 50b generates a release prohibition signal to the shutter drive circuit 25 when the level of the maximum value "JAI" output from the maximum value level detecting circuit 60 is larger than the predetermined upper limit set in the release lock circuit 50b. Consequently, in a camera of to the third embodiment, if the photographer fears that an image blur might occur due to extreme camera-shake during the operation of the shutter button, the release lock may be carried out.

As described above, the probability distribution of the time at which the minimum value occurssubsequently to the occurrence of the maximum value occurs has a peak value at around 25 ms. However, there is a tendency that the time increases as the maximum value increases and decreases as the maximum value decreases. This tendency is shown in Fig.

8, in which the waveshape is identical to that of "JAI" shown in Fig. 3. The level L shown at a dotted line corresponds to the predetermined upper limit above. Even if the maximum value of "JAI" is above the predetermined upper limit L, the maximum value is neglected for the calculation of the delay time, since it is difficult to set a delay time which ensures that the minimum value occurs during the shutter exposure with a high probability, as mentioned above.

mentioned Pl- 114 in Fig. 8 represent the peak values of the maximum values, and tl- t4 the spaces of time between the occurrence of the maximum values and the occurrence of the subsequent minimum values. As can be seen in Fig. 8, P2 > Pl> P3> P4 and t2 > tl> Uk. t4. This proves that the above-mentioned tendency exists.

Consequently, it is possible to set the delay time (i in Fig. 4) of the delay circuit 50, in accordance with the absolute values of the angular velocity in view of this tendency, based on the maximum values of the wave "JAI" input from the maximum value level detecting circuit 60 in order to effectively absorb the camera-shake.

Figure 7 shows a fourth embodiment of the present invention. In Fig. 7, the delay circuit 50 shown in Fig. 6 includes therein a delay time setting circuit 50a. The delay time setting circuit 50a sets the delay time based on the maximum value of the wave "JAI" input from the maximum value level detecting circuit 60. Consequently, with the camera of the fourth embodiment, the probability that the minimum value G of the absolute value wave of the angular velocity appears around at the intermediate time of the shutter exposure period, in accordance with the maximum value thereof, can be increased.

In the illustrated embodiments mentioned above, it is possible to incorporate the composite operation circuit 20, the maximum value detecting circuit 21, the delay circuit 22 or 50, the delay time setting circuit 50a, the release lock circuit 50b, the shutter drive circuit 25, and the maximum value level detecting circuit 60, etc., into an existing CPU of the blur preventing camera 11. The operations of these components are performed in accordance 21 with a predetermined program of the CPU to realize inexpensive camera.

Although the camera-shake is detected by horizontal and vertical angular velocity sensors 17 and in the illustrated embodiments, it is possible to use angular acceleration sensors instead, which detect the angular acceleration of the camera. Furthermore, the detecting sensor which detects camera-shake is not limited to those in the illustrated embodiments, and can be of any type which detects displacement of the camera in either two orthogonal or non-orthogonal directions.

In the illustrated embodiments, an the 19 as mentioned above, the vector values A. and A, of of the angular velocity in the horizontal and vertical directions are added and used to calculate the release time as follows; (A X 2 + A Y 2) 1 / 2 This value can be replaced with (A X2 + A Y2), since the release time is obtained by determining the time between the maximum and minimum values of the absolute value waVe and not the maximum themselves and further since positive magnitude values. As can be understood and minimum values these values are always from the above discussion, with the present invention, upon taking a picture, particularly with a hand-carried camera, an image blur due to camera-shake can be substantially eliminated. Furthermore, since an optical correcting means for optically correcting the image blur is not used in the present invention, a simple and inexpensive camera can be realized.

Although the invention has been described with reference to particular means, materials and embodiments, it is to be understood that the invention is not limited to the particulars disclosed and extends to all equivalents within the scope of the claims.

4 AS

Claims

CLAIMS:

1. A blur preventing camera comprising; a shutter drive mechanism which drives a shutter in response to a signal which is issued when a shutter release switch is turned ON; a camera-shake detecting means for detecting the angular velocity or an oscillation angular acceleration of the optical axis of a taking lens as a result of the optical axis displacement caused by a maximum value detecting occurrence of a maximum angular acceleration value of detected detecting means when said shutter ON; and, a control means for outputting a release signal to said shutter drive mechanism to release said shutter after the lapse of a predetermined amount of time from said occurrence of said maximum value.

2. 1 A blur preventing camera according to claim 1, further comprising a photometering means which calculates brightness data of an object to be taken, and an effective shutter exposure time calculating means for calculating an effective shutter exposure time in accordance with said object brightness data.

camera-shake; means for detecting the said angular velocity or by said camera-shake release switch is turned

3. A blur preventing camera according to claim 2, wherein said control means comprises a delay means which -includes a delay time setting means for setting a delay time which varies said predetermined lapse time in accordance with said effective shutter exposure time output from said effective shutter exposure time calculating means.

4. A blur preventing camera according to claim 1 or 2, further comprising a maximum value level detecting means for detecting said maximum value of said angular velocity or angular acceleration.

5. A blur preventing camera according to claim 4, wherein said control means outputs a release prohibition -signal to prohibit the releasing of said shutter when said maximum value of said angular velocity. or angular acceleration detected by said maximum value level detecting means is above a predetermined upper limit.

6. A blur preventing camera according to claim 4 or 5, wherein said control means comprises a delay means which includes a release lock means which sets said piedetermihed upper limit which is to be compared with said maximum value of said angular velocity or angular acceleration detected by said maximum value level detecting -means.

7. A blur preventing camera according to any one of claims 4 to 6, further comprising a delay time setting means which - 25 varies said predetermined lapse time between the occurrence of said maximum value and the output of said release signal, in accordance with the level of said maximum value detected by said maximum value level detecting means.

8. A blur preventing camera according to any one of the preceding claims, wherein said camera-shake detecting means detects components of said angular velocity or angular acceleration in two orthogonal directions.

9. A blur preventing camera according to claim 8, wherein said camerashake detecting means comprises horizontal and vertical angular velocity sensors which detect said angular velocity or angular acceleration applied to said camera in two orthogonal directions.

10. A blur preventing camera according to claim 8 or 9, further comprising a composite operation means for adding two orthogonal components of said angular velocity detected by said camera-shake detecting means to determine a single angular velocity magnitude.

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11. A blur preventing camera comprising:- a shutter drive mechanism which drives a shutter in response to a signal which is issued when a shutter release switch is turned ON; a camera-shake detecting means for detecting the angular velocity or an oscillation angular acceleration of the optical axis of a taking lens as a result of the optical axis displacement caused by camera-shake; means for detecting the periodicity of oscillations of said angular velocity or angular acceleration detected by said camera-shake detecting means; and a control means for outputting a release signal to said shutter drive mechanism after said shutter release switch is turned ON to release the shutter after the lapse of a predetermined amount of time from a selected occurrence in said oscillation period.

12. A blur preventing camera substantially as hereinbefore described with reference to the accompanying drawings.

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