JPH0282112A - Vibration detecting device using optical fiber gyro - Google Patents

Abstract

PURPOSE:To enable high-accuracy vibration detection by providing optical fiber loops in planes which surround a vibration center line and slant to the vibration center line. CONSTITUTION:Sensitivity axes 12a and 12b of the optical fiber loops 11a and 11b have specific angles to the center axes of the longitudinal shake 13a and lateral shake 13b of a camera to be detected. Therefore, the detection output of a loop 11a is separated into a longitudinal shake angular velocity component 13' and a component 14 of rotation around an optical axis of photography and a component regarding the sensitivity axis 12a can be considered while decomposed into vectors. Similarly, the output of the loop 11b is considered to be an output generated by superposing the lateral shake angular velocity component 13b' and component 14 one over the other. Here, the component 14 is much smaller than the components 13a' and 13b', so the component 14 can be ignored. Then light beams propagated in the loops 11a and 11b are inputted to detectors 45a and 45b respectively to detect variation in the intensity of interference light and the variation is integrated and amplified by an analog integrator and outputted to driving parts 47a and 47b of a correction optical system 46.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vibration detection device for equipment that receives relatively low frequency vibrations, and specifically relates to a vibration detection device that is mounted on, for example, a camera and detects vibrations at a low frequency of about 1 to 12 Hz. This invention relates to an angular velocity sensor using an optical fiber that is used in a system that prevents image distortion by detecting frequency vibration information.

(Background of the Invention) The present invention will be described below using a camera as an example, which is a typical device in which the present invention is suitably utilized.

In modern cameras, important operations for photography, such as exposure determination and focus adjustment, include detection of exposure and focus information that determines these operations, as well as operation control of the photographing mechanism based on the detected information, such as the detected exposure. Many devices have been provided that automate the control of the diaphragm mechanism based on information or the control of the lens focusing mechanism based on focus information.

However, research and development on camera shake caused by camera shake (so-called image blur) has lagged behind due to the difficulty of automating it compared to the other mechanisms mentioned above. It was largely abandoned as it depended on technical knowledge. For this reason, cases of failure in photographing due to so-called camera shake often occur.

Considering the issue of automatic control to prevent image blur during shooting, firstly, image blur is caused by the hand movement of the photographer who supports the camera, so the vibration that is the subject of control is usually It is related to low-frequency vibrations of about 1 to 12 Hz, and based on the premise that it is difficult to artificially suppress these vibrations during shooting, it is possible to take pictures without image blur even if such vibrations occur at the time of release. It is necessary to be able to take pictures, and to do this, the second step is to detect the vibrations that are occurring in the camera at that time, and to set the camera lens in the opposite direction to the vibrations to eliminate the effects of this vibration. A possible solution is to vibrate in the correct direction.

Therefore, in order to mechanically deal with this problem, one is required to have a vibration detection device that accurately detects the vibration actually occurring in the camera, and the other is to correct the photographic lens system. It is necessary to have a structure that can vibrate and a drive device that can vibrate the structure in a corrective manner.

(Prior Art) In principle, the device configuration for detecting camera shake (vibration) information, which is essential when configuring the camera image blur prevention system as described above, is based on information such as angular velocity, angular acceleration, etc. It requires a vibration sensor that detects the angular displacement, and an integration device that electrically or mechanically integrates the signal from this sensor and outputs it as an angular displacement signal. A fiber optic gyro could be considered.

The principle of this optical fiber gyro will be explained with reference to FIG. 7. Light emitted from a light source 51 is split into two by a half mirror 52, and each of the split lights enters optical fibers at both ends of an optical fiber loop 53. These incident lights propagate counterclockwise and clockwise within the optical fiber loop 53, and then exit from opposite ends, are combined by the half mirror 52, and guided to the photodetector 54. When the optical fiber loop 53 is rotating at this time, a so-called Sagnac phase difference Δθ proportional to the rotational angular velocity and expressed by the following equation (1) occurs between the light propagating clockwise and counterclockwise.

Δ　θ　= (Here Δθ λ 4"8L Ω Cλ : Phase difference due to Sagnac effect : radius of optical fiber loop : Optical fiber length :Speed of light in vacuum :wavelength of light (wavelength in optical fiber) Ω: rotational angular velocity) Further, the output I of the interference light is expressed by the following equation (2).

I = A (1 + cos Δθ) (2) (where A: constant) Therefore, by detecting the intensity change of this interference light with the photodetector 54, it becomes possible to detect the rotational angular velocity Ω.

This fiber-optic gyro is capable of configuring the entire light propagation path from the output end of the light source to the detection end of the interference light using optical fibers, and is expected to offer higher precision, longer life, and lower cost. This is one of the technologies that is currently attracting attention.

Next, problems when this optical fiber gyro is mounted on a camera as a vibration detection device will be explained based on FIGS. 6 to 8.

The example shown in FIG. 6 is for detecting vibrations in the vertical direction 41a and the horizontal direction 41b on the distal end side of the camera with respect to the photographing optical axis 41 of the camera. In this figure, 4
Reference numeral 2 denotes a lens barrel, and reference numeral 46 constitutes a part of the optical system, and a correction device is provided so as to be movable in two orthogonal axes perpendicular to the photographing optical axis in order to correct for vibrations. Optical systems 47a and 47b indicate drive units for moving and driving the correction optical system 46 in the two orthogonal axes directions. The correction optical system 46 is
The image plane 48 due to camera vibration is corrected by vibrating the image plane 48.
It becomes possible to ensure the stabilization of the image by correcting the image pretension at .

FIG. 6 shows an example in which an optical fiber gyro having the following configuration is used to perform vibration detection in order to perform correction vibration of the correction optical system 46 by the driving units 47a and 47b. That is, the configuration of this vibration detection device includes an optical fiber loop 43a in a substantially vertical position on the side of the lens barrel 42 for detecting vibration in the vertical direction 41a.
In addition, an optical fiber loop 43b having a generally horizontal attitude is provided at the upper part of the lens barrel 42, and a photodetector (not shown) detects the phase difference based on the Sagnac effect within these loops, and detects the phase difference in the directions 44a and 44b ( In other words, the angular velocity information regarding the direction of rotation around the vertical axis and the horizontal axis) is further converted into an angular displacement signal by detectors 45a and 45b including, for example, an analog integrator. .

47b.

(Problem to be Solved by the Invention) When we look at the phase difference Δθ due to the Sagnac effect detected by the optical fiber gyro as described above in relation to the above equation (1), we find that its sensitivity is proportional to the length of the optical fiber gyro. In order to improve measurement accuracy, it is preferable to increase the length of this optical fiber gyro.

By the way, in order to fit the optical fiber loop into the camera lens barrel in the format shown in Figure 6 above,
There are restrictions on increasing the outer diameter 63 of the loop.

In other words, since the lens barrel 42 has a curvature determined by its diameter, even if an optical fiber loop is to be housed between the inner wall 61 and the outer wall 62 of the lens barrel, it is necessary to place a large diameter planar loop in this range as shown in FIG. This is because it cannot be contained. On the other hand, if the number of turns of the optical fiber loop is increased to make the inner diameter smaller in order to increase the length of the optical fiber loop without changing the outer diameter of the optical fiber loop, the curvature of the optical fiber loop on the inner diameter side becomes extremely large, causing the optical fiber to break. This may lead to problems such as distortion or distortion.
In the configuration shown in FIG. 6, there is a limit to increasing the length of the optical fiber loop, and as a result, it is difficult to improve the measurement accuracy of angular velocity detection.

(Means for Solving the Problems) The present invention improves the configuration of a vibration detection device using an optical fiber gyro that includes the above-described optical fiber loop as a component, and its assembly can be done in parts like a camera lens barrel. An object of the present invention is to provide a vibration detection device with a novel configuration that can detect vibration information with excellent measurement accuracy even when the structure of the device is limited in volume or shape.

Therefore, the characteristics of the vibration detection device using an optical fiber gyro according to the present invention, which has been made to achieve this purpose, is that an optical fiber gyro is mounted on the vibrating body, and the vibration is propagated in the opposite direction within the optical fiber loop of the optical fiber gyro. In a vibration detection device that detects the vibration angular velocity of the vibrating body by detecting the Sagnac phase difference caused by the vibration of the vibrating body, the vibration in two directions is detected at a minute angle about one axis. Therefore, the optical fiber loop is arranged in a plane inclined with respect to the axis, surrounding the center line of the vibration.

The vibration detection device of the present invention is particularly suitably applied to a camera shake prevention system where the structure of the mounting part is restricted.In this case, when the camera is held in a normal shooting posture, It is preferable to detect vibrations about each axis in the vertical direction and horizontal direction within a plane perpendicular to the axis, and to configure each axis independently.

When the present invention is applied to a camera, the optical fiber loop as a component of the optical fiber gyro may be mounted on either the lens barrel of the camera or the camera body. In addition, the so-called hand vibration in a camera is generally in the vertical and horizontal directions as mentioned above in the normal shooting posture, so it is difficult to arrange the optical fiber loop so as to surround the shooting optical axis in a plane tilted to these axes. For example, since the loop wound around a cylindrical lens barrel is generally elliptical, the above formula (1)
In a strict sense, a (radius of the optical fiber loop) must be modified to a formula determined by the given ellipse.

Furthermore, since there is no substantial problem even if it is understood that the camera shake vibration that is a problem in cameras is limited to those around the two orthogonal axes, the vertical and horizontal directions, the optical fiber loop that is tilted with respect to the axes is Even if the sensitivity axis of vibration detection by It is also preferable to separately detect the vibration angular velocity around the optical axis, and to calculate the difference between this and the output of the vibration angular velocity detected by the inclined optical fiber loop.

(Function) According to the present invention, an optical fiber gyro can be used to easily and conveniently mount a target vibration detection device on a structurally restricted object such as a lens barrel. Moreover, since the length of the optical fiber can be increased, it is effective in improving measurement accuracy.

(Example) The present invention will be described below based on an example shown in the drawings, which is an example of the case where the present invention is applied as a system for detecting vibration for preventing image blurring of a camera.

Embodiment 1 Figure 1 shows an example of a general configuration of a vibration detection device using an optical fiber gyro according to the present invention. Similarly, llb indicates an optical fiber loop provided for detecting lateral camera shake (shake around the vertical axis in the drawing).

The sensitivity axes of these optical fiber loops lla, llb (
In other words, perpendiculars to the center point of each loop plane) 12a and 12b are the center axis of the camera's vertical shake 13a (rotation around the horizontal axis perpendicular to the photographing optical axis, centered on the camera body) to be actually detected, and the horizontal axis. It has a predetermined angle with respect to the central axis of the pre-13b (rotation around the vertical axis around the camera body), and therefore, for example, the optical fiber loop 11a
The output detected by
The component related to a can be considered by vector decomposition. Similarly, the output of the optical fiber gyro llb is composed of the horizontal pre-angular velocity component 13b' and the rotational component 1 about the photographing optical axis.
4 can be considered as a superimposed output.

By the way, when considering the above detection components by decomposing them, the rotational component 14 around the photographing optical axis of each component is compared to the other components, the vertical angular velocity component 138' or the horizontal angular velocity component 13b' of the camera. It can be considered that these components are extremely small enough to handle the actual camera, so each detected component can be regarded as the vertical angular velocity component or horizontal angular velocity component of the camera without correction (that is, the rotational component 14).
In many cases, there is no problem in using this as detection information in an image prevention system (ignoring the above). For example, if the rotational component 14 around the photographing optical axis is ignored as described above, the error is about 1% when the tilt angle of the optical fiber gyro with respect to the photographing optical axis is 45 degrees, so if the tilt angle is 25 degrees or more, then the error is about 1%. Even if the rotational component 14 is ignored, it is actually possible to perform photographing with suitable prevention of image blur.

The light propagated through the optical fiber loop lla is input to a detector 45a including, for example, a photodetector and an analog integrator, and a known photodetector such as an St photodiode (not shown) is used to detect changes in the intensity of the interference light. This is detected, integrated and amplified by an analog integrator (not shown), and outputted to the drive section 47a of the correction optical system 46. The driving section of the correction optical system can be constructed using the mechanism described in, for example, Japanese Patent Laid-Open No. 62-47011.

In this example, since the optical fiber loop 11a is not a perfect circle but an ellipse, in a strict sense the above formula (
1) cannot be directly applied, but as can be seen from equation (1), the phase difference Δ due to the Sagnac effect detected
In short, it can be said that θ and the rotational angular velocity Ω are in a proportional relationship, so that the magnitude of the phase difference of the propagating light due to the change in intensity can be detected, making it possible to apply it to the system for preventing image distortion in this example.

According to the configuration in which the optical fiber loop is arranged so as to surround the photographing optical axis in a plane inclined with respect to the photographing optical axis of the lens barrel as in this example, the conventional lens barrel shown in FIG. Compared to a type in which the optical fiber loop is located in a plane containing the generatrix, the loop can be formed with a gentler curvature, and a device can be formed without putting an undue burden on the optical fiber that forms the loop. There is an advantage. Furthermore, in view of the functionality of the device, the optical fiber loop can be formed with a large radius, so the loop length expressed by the above equation (1) can be set to a large value, thereby improving measurement precision and measurement sensitivity. Furthermore, especially when applied to a camera in this example, it is possible to wrap an optical fiber loop around the lens barrel surrounding the photographing optical axis.
Another feature is that it is easy to manufacture.

Example 2 The optical fiber gyro installed in the camera of this example shown in Fig. 2 has the same principle of vibration detection and the same device configuration except for the difference in direction. I have only written about the play.

The optical fiber loop llb in this figure is Example 1
The optical fiber loop ttb is the same as the optical fiber loop ttb described above, and in addition to this, this example is characterized by providing an optical fiber loop 21 located in a plane perpendicular to the imaging optical axis used for vibration measurement. This optical fiber loop 21
is arranged in a plane perpendicular to the photographing optical axis, so the angular velocity output detected thereby is a component around the photographing optical axis 14. Therefore, by detecting the difference between the output from the optical fiber loop 21 and the output from the optical fiber loop Ilb with the detector 22b including a differential amplifier, the component in the direction of the sensitivity axis 14 included in the output from the optical fiber loop Ilb is removed. The signal output from the detector 22b including this differential amplifier has higher accuracy as detection information of the lateral play angular velocity than in the first embodiment.

It goes without saying that similarly highly accurate detection information can be obtained regarding vertical shake by calculating the difference between the output detected by the optical fiber gyro of the optical fiber lube 21 and the output detected by the optical fiber gyro.

Example 3 The optical fiber gyro mounted on the camera of this example shown in FIG.
The optical fiber loop 24a corresponding to the camera body 2
5, and this and the optical fiber loop 21 of Example 2
This embodiment is functionally similar to the second embodiment, except for the difference in the arrangement that an optical fiber loop 23 corresponding to the above is mounted on the lens mount portion of the camera body.

Although FIG. 3 only describes vertical shake to simplify the explanation, it goes without saying that a similar configuration can be applied to horizontal shake.

According to this example, in addition to being able to detect vibrations caused by camera shake with high accuracy similar to that in the second embodiment, since the optical fiber loops 23 and 24a are mounted inside the camera body 25, the camera body 25 In addition to being able to use the wall surface to wind a long loop with a large diameter, the lens barrel itself does not need to have a structure for detecting hand vibration, making the interchangeable lens itself cheaper. This has the advantage that for camera models that require the use of a large number of interchangeable lenses, it is possible to provide an efficient product group as a whole, including interchangeable lenses.

Embodiment 4 In the present embodiment shown in FIG.
The optical fiber loop portion 31 is set to be inclined in the same manner as
2f continuous b at the connecting part 33b! An optical fiber loop 34b having a composite structure is assembled. In the optical fiber loop 34b of this example, the optical fiber loop portion 31b and the optical fiber loop portion 32b are wound in opposite directions (inverse phase) with respect to the photographing optical axis, and have the same number of windings, as shown in the figure. It has characteristics. In other words, due to the anti-phase winding of the optical fiber loop portion 31b and the optical fiber loop portion 32b, the phase difference due to the angular velocity in the direction of the sensitivity axis 14 of the light beam propagating in the clockwise direction in the figure propagating through the loop portion 31b is caused by Therefore, the output of the phase difference detected by the optical fiber loop 34b of this example does not include the component of the rotational angular velocity 14 around the imaging optical axis, and moreover, In comparison, whereas an optical fiber gyro requires two half-mirror-1 photodetectors in connection with two optical fiber loops, this example can be configured as one optical fiber gyro, so there are fewer components. It has the characteristic of being able to have an inexpensive device configuration.

Embodiment 5 The present embodiment shown in FIG. 5 is a further development of the above-mentioned embodiment 4, in which the optical fiber loop section 31b is arranged at an angle with respect to the photographing optical axis 41 in the same way as in embodiment 4. Further, the optical fiber loop portion 35b is arranged with an angle of inclination opposite to this, and the loop portion 31b and the loop portion 35
As shown in the figure, the winding directions of windings b and b are opposite to each other (reverse phase) with respect to the photographing optical axis, and the number of windings is the same.

According to such a configuration, the angular velocity components other than the rotational angular velocity around the vertical axis cancel each other out, and moreover, in the fourth embodiment
Compared to this, since the component of the rotational angular velocity around the vertical axis to be detected is amplified by superimposing the detection outputs of both, it is possible to detect vibrations with higher accuracy.

(Effects of the Invention) As explained above, the vibration detection device using the optical fiber gyro according to the present invention has a configuration in which the optical fiber loop is arranged in a plane surrounding the vibration center line and inclined with respect to the vibration center line. As a result, it is possible to provide a high-precision vibration detection device that is easy to manufacture and has a space-saving structure, and is particularly effective when applied to systems to prevent image blur caused by camera shake. .

In addition, the vibration detection device of the present invention uses two optical fiber loops with different inclination angles (including right angles) to the center line of the vibration to be detected, or an optical fiber loop with two continuous parts. Another advantage is that it is possible to realize a device that can detect vibrations with higher precision by removing components other than the target vibration with a simple configuration. When an optical fiber loop is used, only one half-mirror 1 photodetector or the like that constitutes the optical fiber gyro is required, so an excellent effect can be obtained in that the number of constituent members is small.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a configuration overview of a first embodiment of a vibration detection device using an optical fiber gyro according to the present invention, and FIG. 2 is a partial configuration overview of a second embodiment of a vibration detection device using an optical fiber gyro. Figures 3 to 5 are diagrams showing a part of the configuration outline of Examples 3 to 5 of vibration detection devices using optical fiber gyros, respectively, and Figure 6 is a diagram showing a comparative example of a vibration detection device using an optical fiber gyro. FIG. 7 is a diagram for explaining the principle of an optical fiber gyro, and FIG. 8 is a diagram for explaining problems with the configuration of FIG. 6. 11a, llb = optical fiber loop 12a, 12
b - Sensitivity axes 13a, 13b, 14 - Direction of vibration 21.23, 24a...Optical fiber loop 25...
・Camera body 31b, 32b, :15b...Loop part 34b...
Optical fiber loop 41...Photographing optical axis 42...Lens barrel 43
a, 43b...optical fiber loops 22a, 22b
---Pressure detector 45a, 45b ----Detector 46-
...Correction optical system 47a, 47b...Drive section 48
... Image plane Fig. 7 Fig. 8

Claims (1)

[Claims] 1. An optical fiber gyro is mounted on a vibrating body, and light in two directions propagating in opposite directions in an optical fiber loop constituting the optical fiber gyro has a position due to the Sagnac effect caused by the vibration of the vibrating body. A vibration detection device that detects the vibration angular velocity of the vibrating body by detecting a phase difference,
In order to detect the vibration at a minute angle about one axis, the optical fiber loop is characterized in that it has a loop wound around the center line of the vibration in a plane inclined with respect to the one axis. A vibration detection device using an optical fiber gyro. 2. The vibration detection device using an optical fiber gyro according to claim 1, wherein the vibrating body is a camera, and the vibration center line substantially coincides with the photographing optical axis. 3. The vibration detection device using an optical fiber gyro according to claim 2, wherein the optical fiber gyro is provided independently around two orthogonal axes, a vertical direction perpendicular to the imaging optical axis and a horizontal direction. 4. A first optical fiber loop located in a plane inclined to the photographing optical axis, and a second optical fiber capable of detecting a vibration component equal to the vibration component around the photographing optical axis contained in the output from the first optical fiber loop. Claim 1, further comprising means for detecting the vibration angular velocity around the one axis based on the output difference between the two loops.
A vibration detection device using the optical fiber gyro described in any one of 3 to 3. 5. A first optical fiber loop portion located in a plane inclined to the photographing optical axis, and a second optical fiber loop portion that detects a vibration component equal to the vibration component around the photographing optical axis contained in the output from the first optical fiber loop. The first and second optical fiber loop portions are continuous to form a single optical fiber loop, and the first and second optical fiber loop portions are arranged around the photographing optical axis. 4. A vibration detection device using an optical fiber gyro according to claim 1, characterized in that the fiber optic gyro is provided in a reverse winding relationship so that vibration components cancel each other out.