Imaging apparatus with mechanism for enhancing resolution

Abstract: A refracting plate (1) is installed in the center of an actuator provided with a gimbaling mechanism element (2), which includes rotation supporting portions (2cx), (2cy). A pair of voice coil motors (5x), (5y) are provided for each of the X- and the Y-axis in order to incline the refracting plate (1) about the respective rotation supporting portions (2cx), (2cy), and their own bobbins press the middle parts of the respective sides of the gimbaling mechanism element (2).

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging apparatus using a solid state imaging element and particularly to an improvement in the mechanism for enhancing resolutions by shifting the imaging position of the light from the subject which enters the solid state imaging element, in a pixel arrangement direction in a light receiving plane nearly vertical to the axis of the incident light. 2. Description of the Related Art Generally, the solid state imaging element such as a charge coupled device has a plurality of pixels arranged so as to form a two-dimensional matrix, and the resolution of an image is substantially determined by the number of pixels in the light receiving plane. Accordingly, all that is needed to achieve higher resolutions is to increase the number of pixels of the solid state imaging element, but from aspects of present techniques and costs the increase in number of pixels has its limit. Fig. 25 illustrates the principle of the prior art disclosed in Japanese Unexamined Patent Publication JPA 60-54576 (1985) and Japanese Unexamined Patent Publication JPA 61-251380 (1986). A flat refracting plate 100a is interposed in the middle of the optical axis 100 of the light incident from a subject to a light receiving plane. When the refracting plate 100a is inclined by an angle from the state shown by a two-dot chain line vertical to the optical axis 100, the incident light 101 is displaced from the optical axis 100 by a shift Δ which is obtained by the following formula (1): Δ=t · sin [1- { 1 - sin 2  / n 2 - sin 2  }] wherein "t" and "n" are the thickness of the refracting plate, and the index of refraction of the glass which is a material of the refracting plate, respectively. If the inclination angle  of the refracting plate 100a is changed, it is possible to shift the imaging position of the incident light 101 from the subject in relation to the light receiving surface of the solid state imaging element in the horizontal and perpendicular directions of the pixel arrangement by an infinitesimal distance less than the pixel arrangement pitch. When a plurality of images obtained by shifting the incident light 101 are composed on an image memory, then the number of the pixels of the solid state imaging element apparently increases, and images with higher resolutions can be obtained. Figs. 26, 27 are views showing the constitution of the prior art disclosed in Japanese Unexamined Patent Publication JPA 61-251380 (1987), that is, a sectional side view and a front view, respectively. The transparent flat refracting plate 100a made of a material such as glass is disposed between a lens 100b and a solid state imaging element 100c so as to traverse the optical axis 100 of the lens 100b. The refracting plate 100a is rectangular, in the center of each side of which is mounted a supporting member 100d having a L-shaped section, and a coil 100e is fixed on the longer side of each supporting member. A movement limiter 100f is provided on the shorter side of each supporting member so as to hold each supporting member 100d. A magnet 100m and a yoke 100y are arranged in the vicinity of each coil 100e. The movement limiter 100f, magnet 100m and yoke 100y are fixed on the cabinet side of the imaging apparatus main body. An electromagnetic driving force is generated to the magnetic flux of the magnetic circuit which is formed between the magnet 100m and the yoke 100y, by the current in the coil 100e, acting as driving force to advance and retreat each coil 100e in a direction along the optical axis 100. Now, it is assumed that one pair of adjacent coils 100e containing a corner are driven rightward along the optical axis and the other pair of coils 100e containing a corner are driven leftward along the optical axis. One of two corners confronting each other of the refracting plate 100a advances along the optical axis 100 and the other of the two corners retreats along the optical axis 100. The shorter sides of the supporting member 100d mounted on each side of the refracting plate 100a are respectively contacted to the move limiter 100f, and as a result the refracting plate 100a inclines to the optical axis 100 by a certain angle. In Japanese Unexamined Patent Publication JPA 60-54576 (1985), as an actuator is used as an actuator a piezoelectric element instead of an electromagnetic actuator disclosed in Japanese Unexamined Patent Publication JPA 60-251380 (1985), and their fundamental constitutions are the same. Fig. 28 is a view showing the constitution of a gimbaling mechanism as disclosed in Japanese Unexamined Patent Publication JPA 4-211217 (1992). In this prior art, two dimensional optical scanning is conducted using a gimbaling mechanism element. A first oscillator 200 comprises a frame 201 which comprises a pair of rotation supporting portions 202, 203, in the center of which a reflection mirror 204 is installed. A second oscillator 205 comprises a frame 206, and a pair of rotation supporting portions 207, 208, in the center of which the first oscillator 200 is installed. The rotation axis of the rotation supporting portions 202, 203 is at right angles to the rotation axis of the rotation supporting portions 207, 208. The first and second oscillators 200, 205 are independently rotated and oscillated about respective rotation axes by electrostatic force. When the reflection mirror 204 is exposed to the incident light from a subject in a state that the first and second oscillators 200, 205 are rotated and oscillated about the two orthogonal axes, the angle of the reflected light is altered and as a result the optical path can be changed. By applying this constitution, the resolution of the solid state imaging element can be enhanced like the case as shown in Fig. 25 where refraction of light is taken advantage of. Fig. 29 is a view showing a simplified electrical constitution for screen composition aiming at enhancing the resolution. Memories 301-304 which have a storage capacity corresponding to the number of the pixels of the solid state imaging element are provided, and input signals representing an image formed by shifting the imaging position each period of four division frame periods T1-T4 are changed over to store the image data in the respective memories 301-304. When the image data from the respective memories 301-304 are composed in a memory 305, an image for one frame whose resolutions in the length and width directions are doubled can be obtained as a whole. In the prior art as shown in Figs. 26, 27, since the inclination angle  of the refracting plate 100a depends on the traveling distance of the supporting member 100d until the shorter side of the supporting member 100d contacts with the movement limiter 100f, the inclination angle  is determined by only one variable and thus it is difficult to select the desired resolution. In addition, there are some cases where the refracting plate 100a is required to be inclined a plurality of times within a short period, in which cases, if driven at high speeds, repeated contact between the movement limiter 100f and supporting member 100d may cause their wear, thus resulting in lowered precision of the inclination angle  and further impairment of their durability. In addition, the noise which occurs at the time of contact grows to levels which are no longer negligible as the driving speed increases. Furthermore, in the prior art as shown in Fig. 28, the use of the two uniaxial oscillator results in an increased parts count, a complicated configuration and consequently poor assembling efficiency. Moreover, since the first oscillator 200 is secured to the second oscillator 205, the weight of the second oscillator increases, thus resulting in greater driving force due to the increased inertia moment. As still another constitution may be feasible such a constitution that the refracting plate is inclined by the couple of forces generated by a pair of voice coil motors facing across the axis of rotation. In such constitution, the difference in thrust between the pair of voice coil motors causes oscillation in the vertical direction to the refracting plate. When the oscillation gain is increased, the oscillation acts as disturbance to the circumference of the rotation axis in a control direction and the servo controllable range is thus limited. DE 4031753 discloses an image recording device in which an image formed on a semiconductor image sensor is shifted cyclically in a horizontal direction using a tiltable filter disc disposed in the beam path. A filter disc carrier has a thinned part forming a hinge about which a filter disc mounting portion is tilted using an electromagnetic driver. Patent Abstracts of Japan, vol. 16 no. 75 (p-1316) and JP 3264911 A disclose an optical tracking device in which a beam-deflecting mirror is mounted for biaxial controlled rotation about orthogonal axes by means of a gimbal arrangement. DE 4034488 discloses an imaging apparatus in which a refracting plate is arranged in front of an electro-optical mosaic detector and means is provided for inclining the refracting plate so as to shift the image relative to the detector and thereby effect a so-called microscan. SUMMARY OF THE INVENTION The present invention has been accomplished to overcome at least some of the aforementioned problems. The invention provides an imaging apparatus in which a refracting plate is arranged to transmit light from a subject toward a solid state imaging element for imaging the subject and means is providing for inclining the refracting plate so as to laterally shift the optical axis of light incident upon the solid state imaging element in the arrangement direction of the solid state imaging element, the inclining means including: a gimbaling mechanism element in which the refracting plate is mounted and in which there is provided rotation supporting means for supporting the refracting plate rotatably about two rotational axes extending in two directions at right angles to each other, and a plurality of drive devices, each having a displaceable portion capable of advancing and retreating, said displaceable portions being arranged to act so as to effect controlled rotation of the refracting plate about said respective rotational axes, characterised in that the refracting plate is arranged between a lens for condensing the light from the subject and the solid state imaging element, and in that said gimbaling mechanism element comprises a first support member on which said refracting plate is mounted and a second support member, the rotation support means comprising first and second rotational support portions provided in the areas of respective edges of the refracting plate, the first support member being rotatably connected to the second support member about a first of said rotational axes by first said rotational supporting portions, and the second support member being rotatably supported about a second of said rotational axes by second said rotational supporting portions, and the displaceable portions being connected to the midpoints of said edge areas of the refracting plate so as to confront each other about the respective rotational axes. In the described embodiments, the first support member is an inner rectangular frame part and said second support member is an outer rectangular frame part. In one embodiment, the inner and outer frame parts and said first and second rotational supporting portions are integrally formed from a metal thin plate, and the gimbaling mechanism element further includes inner and outer rectangular reinforcing plates respectively fixed to said inner and outer frame parts. The drive devices, which are preferably voice coil motors, are preferably arranged in pairs, the devices of each respective pair being disposed on opposite sides of the respective rotational axis about which those devices effect controlled rotation of the refracting plate. In the embodiments, the displaceable portions of each respective pair of drive devices are attached to opposite sides of the inner rectangular frame part. In accordance with a preferred feature of the invention, the rotation supporting portions of the gimbaling mechanism element are respectively bobbin-shaped, in that the width thereof gradually reduces from the end portions toward the centre portion as hereinafter defined. In a preferred form, the imaging apparatus of the invention comprises target value generating means for generating signals wherein target values for the inclination angle of the refracting plate are made different according to a preset resolution; angle detecting means for detecting the inclination angle of the refracting plate; and control means for comparing the target value represented by a signal outputted from the target value generating means and the inclination angle of the refracting plate detected by the angle detecting means and for controlling thrusts to advance and retreat the voice coil motors according to the difference therebetween. Preferably, the angle detecting means comprises a light emitting element, and is set so that the light from the light emitting element which has been passed through or reflected on the refracting plate is applied to an invalid region beyond the subject imaging region of the solid state imaging element and that the inclination angle of the refracting plate is detected from the position of the light applied to the invalid region. The imaging apparatus preferably comprises movement vector detecting means for comparing the image data obtained at the current inclination angle of the refracting plate with the image data obtained at its immediately preceding inclination angle to arithmetically operate the movement vector between images and for outputting a signal for correcting the target value outputted from the target value generating means on the basis of the arithmetical operation result. In the imaging apparatus of the invention, a frequency f m preferably satisfies the following expressions: 2 ≦ x/(10f m ) 2 /z 3 ≦ 11 (m -2 Hz -2 ) and 3 ≦ a/(10f m ) 2 /z 3 ≦ 15 (m -2 Hz -2 ) wherein "z" and "x" are respectively the length and width of the rotation supporting portions of the gimbaling mechanism element in one of the two directions at right angles to each other, namely the X-axis direction, and f x is the resonance frequency of the rotational oscillation about the X-axis; "L" and "a" are respectively the length and width of the rotation supporting portions in the other of the two directions, namely the Y-axis direction, and f y is the resonance frequency of the rotational oscillation about the Y-axis; and f m is the larger frequency of the resonance frequencies f x , f y . Preferably, there is provided regulating means for making variable the thrust of at least one of the voice coil motors confronting each other through the respective rotation axes. Preferably, the voice coil motors are of a moving coil type and the shapes of the sections thereof vertical to the movement directions of the coils are semicircular. In the invention, since the displaceable portions of the drive devices, preferably composed of two pairs of portions opposed to each other about the rotation axes, effect controlled rotation of the refracting plate about said rotation axes in two directions at right angles to each other, the inclination angle of the refracting plate is determined depending on the forward and backward movement of the displaceable portions in the optical axis direction. The resolution may be freely selected as desired, because the imaging position on the light receiving surface of the imaging element can be displaced by adjusting the forward/backward movement of the movable parts. In addition, since the refracting plate and gimbaling mechanism element do not undergo contact with other members even when the refracting plate is driven at high speed, the durability of the apparatus is excellent, and the accuracy of the inclination angle is stable over a long period. In addition, no noise is generated. Furthermore, since the imaging apparatus constructed as mentioned above comprises a single gimbaling mechanism element, the parts count may be reduced and the constitution may be simplified. Further, if the rotation supporting portions are formed into a bobbin shape, the spring constant of the gimbaling mechanism element is increased in the optical axis direction without depreciating the rotatability of the rotation supporting portions. Thereby the occurrence of disturbance is restrained with the result that controlling with high accuracy can be realized. Further, since the inclination angle of the refracting plate may be controlled depending on the set resolution, the resolution may be variable, which affords convenience to users. Further, there may be included an angle detecting means comprising a light emitting element from which light for detecting an angle is emitted. The light transmitted through or reflected on the refracting plate is received using an invalid region which is formed by arranging, at a position beyond the imaging region of a subject of the solid state imaging element, a light receiving element which is not used as a picture element for imaging. Since it is not necessary to provide the angle detecting means with a dedicated light receiving element for receiving the light from the light emitting element separately, the imaging element can be reduced in size, resulting in lowering costs. According to the preferred embodiment, the image data obtained under the condition of the current inclination angle of the refracting plate and the image data obtained under the condition of the preceding inclination angle of the refracting plate are compared by the movement vector detecting means to arithmetically operate the movement vector between images, and the target value is corrected on the basis of the operation results. Thereby the change of the actuator depending on time is compensated with the result that stable operation can be realized over a long period. Further, according to the preferred embodiment, since the shape of the rotation supporting portions is selected so that the resonance frequency of rotational oscillation exists within an appropriate range, satisfactory servo characteristics can be established without interfering with rotation of the rotation supporting portions. Further, according to the preferred embodiment, since the refracting plate is inclined by the couple of forces generated by the voice coil motors facing across the axis of rotation, oscillation is caused in the direction vertical to the refracting plate when there is a difference in thrust between the two voice coil motors. However, since the resonance gain of oscillation can be decreased by controlling the thrust of at least one of the two voice coil motors, servo characteristics over a wide range can be established, resulting in stable control of the apparatus. Further, according to the preferred embodiment, since the voice coil motors are of a moving coil type and the shapes of the sections vertical to the moving directions of the coils thereof are semicircular, a sufficient space is ensured between the voice coil motors by arranging the circular arc sides of the voice coil motors on the outer side. The solid state imaging element is arranged in the space to make the imaging apparatus small in size as a whole. BRIEF DESCRIPTION OF THE DRAWINGS Other and further objects, features, and advantages of the invention will be more explicit from the following detailed description taken with reference to the drawings wherein: Fig. 1 is a perspective view of an actuator part of an imaging apparatus of an embodiment of the invention; Fig. 2 is an exploded perspective view of the actuator part of the embodiment of Fig. 1; Fig. 3 is a longitudinal sectional view of a voice coil motor of the embodiment of Fig. 1; Fig. 4 is a block diagram showing the schematic electrical configuration of a control circuit part for controlling the actuator part in the embodiment of Fig. 1; Fig. 5 is a timing chart showing output waveforms of a signal generator for rotation angles about an X- and a Y-axis, respectively, which constitutes the control circuit part of Fig. 4; Fig. 6 is a side view showing an arrangement of an angle detector of the embodiment of Fig. 1; Fig. 7 is a front view of the light receiving portion of the angle detector of Fig. 6 when viewed from a light incidence end; Fig. 8 is a side view showing another arrangement of an angle detector of another embodiment of the invention; Fig. 9 is an enlarged plan view of a solid state imaging element of the embodiment of Fig. 1; Fig. 10 is a plan view showing the form of a gimbaling mechanism element of another embodiment of the invention; Fig. 11 is a Bode diagram showing servo characteristics of the actuator part of the embodiment of Fig. 1; Fig. 12 is a perspective view schematically showing the shape of a rotation supporting portion; Fig. 13 is a view schematically showing an example of deflection of a post having a rectangular; Fig. 14 is a view schematically showing a model of oscillation in Z-direction of a gimbaling mechanism element of the embodiment of Fig. 1; Figs. 15A-15C are a plan view and partially enlarged perspective views of the gimbaling mechanism element of the embodiment of Fig. 1; Figs. 16A, 16B are diagrams showing regions where preferable servo characteristics are obtained in the embodiment of Fig. 1, indicated by oblique lines; Figs. 17A, 17B are diagrams showing regions where preferable servo characteristics are obtained in the embodiment of Fig. 1, indicated by oblique lines; Figs. 18A, 18B are diagrams showing regions where preferable servo characteristics are obtained in the embodiment of Fig. 1, indicated by oblique lines; Figs. 19A, 19B are diagrams showing regions where preferable servo characteristics are obtained in the embodiment of Fig. 1, indicated by oblique lines; Fig. 20 is a diagram in which satisfactory examination results regarding servo characteristics are plotted; Fig. 21 is a block diagram showing a schematic electrical configuration for adjusting thrust of voice coil motors; Fig. 22 is a perspective view showing a constitution of a gimbaling mechanism element of another embodiment of the invention; Fig. 23 is a plan view of the gimbaling mechanism element of Fig. 22; Fig. 24 is a block diagram showing an electrical constitution of a control circuit part for controlling an actuator part of still another embodiment of the invention; Fig. 25 is a view for explaining a principle that an image of a high resolution can be obtained by changing the inclination angle of a refracting plate; Fig. 26 is a sectional side view showing a constitution of the prior art; Fig. 27 is a front view showing the prior art of Fig. 26; Fig. 28 is a perspective view showing a constitution of another prior art; and Fig. 29 is a block diagram showing an electrical constitution in which high resolution can be achieved. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now referring to the drawings, preferred embodiments of the invention are described below. Fig. 1 is a perspective view showing an actuator part for inclining a refracting plate of an imaging apparatus of an embodiment of the invention, and Fig. 2 is an exploded perspective view of the actuator part. The refracting plate 1 is made into a plate form of a transparent material such as glass, acrylic resin or the like, having a rectangular section. In order to minimize inertia such as inertia moment, it is preferable that the refracting plate 1 is as light as possible. The gimbaling mechanism element 2 is integratedly formed in such a manner that etching or the like is applied to a metal thin plate having a high elastic modulus, and comprises an inner frame part 2a and an outer frame part 2b. Two virtual axes which are at right angles to each other and which pass through the midpoints of the respective opposite sides of the inner frame part 2a and outer frame part 2b defined as the X-axis and Y-axis. Rotation supporting portions 2cx are provided at the positions of both ends of the X-axis between the inner frame part 2a and outer frame part 2b, namely right and left positions of the X-axis, and rotation supporting portions 2cy are provided at the positions of both ends of the Y-axis in the outer frame part. The respective rotation supporting portions 2cx, 2cy are formed to have much smaller widths than the respective widths of the inner frame part 2a and outer frame part 2b. Thereby the gimbaling mechanism element 2 is allowed to biaxially rotate about the X-axis and Y-axis passing through the centers of the cross sections of the respective rotation supporting portions 2cx, 2cy. Inner and outer reinforcing plates 3, 4 are bonded and fixed to the inner and outer frame parts 2a, 2b, respectively. The respective reinforcing plates 3, 4 are made of a synthetic resin or light metal and shaped to be correspond the shapes of the inner and outer frame parts 2a, 2b. The respective reinforcing plates 3,4 are set to be much thicker than the gimbaling mechanism element 2. A refracting plate 1 is inserted and fixed inside the inner frame part 2a of the gimbaling mechanism element 2 and the inner reinforcing plate 3. By fixing the respective reinforcing plates 3, 4 to the gimbaling mechanism element 2 in this manner, the gimbaling mechanism element 2 is reinforced and as well the freedom of the gimbaling mechanism element 2 regarding movement other than rotation about the X- and the Y-axis is restricted. Accordingly the spring characteristics of the gimbaling mechanism element 2 depend on solely the shape and rigidity of the rotation supporting portions 2cx, 2cy. The method of designing the rotation supporting portions 2cx, 2cy will be detailed below. In this connection, defining as Z-axis an axis passing through the intersection of the X- and the Y-axis and being at right angles to the respective axes, a lens which condenses reflected light from a subject is arranged at an upper position of the refracting plate 1 so that its optical axis corresponds to the Z-axis. A voice coil motor 5 is arranged on the lower side of the Z-axis, and further at a lower position thereof a solid state imaging element is arranged so that its light receiving surface intersects the Z-axis and is at right angles to the Z-axis. If the reinforcing plates 3,4 are made as light as possible, the inertia around the X- and the Y-axis become small, and conveniently the thrust of the voice coil motor 5 may be small. Both ends of each rotation supporting portion 2cy formed on the Y-axis are connected to a cabinet 6 of the imaging apparatus. The voice coil motors 5 consist of two pairs positioned around the Z-axis, one of which arranged in the X-axis direction and the other of which is arranged in the Y-axis direction. The voice coil motors between which the X-axis is placed are designated with 5x, and those between which the Y-axis is placed are designated with 5y. Additionally all the voice coil motors are generally designated with a reference numeral 5. According to the embodiment, each voice coil motor 5 is of a moving coil type (MC type) with the configuration as shown in Fig. 3. Movable parts of the voice coil motor 5 is composed of a bobbin 7 and a coil 8 wound around the outer circumferential surface of the base end of the bobbin 7. The bobbin 7 and coil 8 are formed into a semicircular shape in its plan view so as not to prevent incidence of the light reflected from the subject onto the solid state imaging element via the refracting plate 1. The coil 8 is suspended in a magnetic cap in a magnetic circuit composed of a magnet 9 and yokes 10, 11. The magnet 9 and yoke 10 are semiarc-shaped corresponding to the bobbin 7 and coil 8 and the yoke 11 has a semi-cicular column portion in its center area. The semi-circular column portion in the center of the yoke 11 is inserted into the base end of the bobbin 7. A magnetic path as indicated by arrows in Fig. 3 by the magnetic circuit. The four voice coil motors 5 are arranged so that the respective arc sides of the semicirculars are positioned on the outer side and have spaces inside. The bobbins 7 of the respective voice coil motors 5 are bonded securely to the midpoints of the respective sides of the inner reinforcing plate 3. Accordingly one pair of voice coil motors 5y and the other pair of voice coil motors 5x are positioned along the X-axis and Y-axis, respectively. Now, such a case is supposed that currents in the opposite directions to each other are fed through the respective coils 8 confronting to each other of any one of the pairs of voice coil motors 5x, 5y to drive the motor. One bobbin 7 moves upward along the yoke 11, while the other bobbin 7 moves downward along the yoke 11. As a result a couple of forces are exerted on the inner reinforcing plate 3 to rotate the gimbaling mechanism element 2 about the respective rotation supporting portions 2cx, 2cy, and thus incline the refracting plate 1 about the X-axis or Y-axis by the rotation. Additionally the voice coil motor 5 is preferred to be of MC type for the purpose of reducing the whole apparatus in weight and other type such as moving magnet type (MM type) may be applied. Fig. 4 is a block diagram showing the configuration of a control circuit part for driving an actuator part as shown in Figs. 1-3. A mode control signal is fed from a controller 19 to a target value generator 20. The target value generator 20 generates target values for rotation angles about the X- and the Y-axis of the refracting plate 1, respectively, on the basis of inputted mode control signals. Signal generators 21X, 21Y for rotation angles about the X-axis respectively generate signals for rotation angles about the X- and the Y-axis, having periodic waveforms, as shown in Fig. 5 on the basis of the target values for the rotation angles about the X- and the Y-axis from the target value generator 20. Comparison circuits 22x, 22y compare the rotation angle signals as control targets from the signal generators 21x, 21y for rotation angles about the X- and the Y-axis, with detection signals of the rotation angles about the X- and the Y-axis of the refracting plate 1, and output signals representing the differences therebetween. Amplifiers 23x, 23y amplify outputted signals from the comparison circuits 22x, 22y, respectively. Phase compensation circuits 24x, 24y compensate the phases of the signals outputted from the amplifiers 23x, 23y, respectively to prevent oscillation. X- and Y-axis drivers 25x, 25y drive the respective voice coil motors 5x, 5y for the rotation about the X- and the Y-axis, respectively. An angle detector 26 detects rotation angles about the X- and the Y-axis of the refracting plate 1 to feed detection signals to the comparison circuits 22x, 22y. Now, such a case is supposed that a mode control signal for setting a twice as high resolution is inputted from the controller 19. From the target value generator 20 are generated respective target values x1, x2, y1, y2 for the respective rotation angles about the X- and the Y-axis of the refracting plate 1 as shown in Fig. 5. Hereupon the horizontal and vertical pitches of the respective pixels of the solid state imaging element are designated with Px and Py. In order to obtain an image of the twice as high resolution, it is required to shift the imaging position of the subject by Px/2 in the horizontal direction and by Py/2 in the vertical direction. When one set of target values x1, y1 are assumed as, for example, 0, from the above equation (1) the other set of target values x2, y2 are given on the basis of an angle  satisfying the following equation (2): Px/2, Py/2=t · sin [1-{ 1-sin 2  / n 2 -sin 2  }) The target values x1, x2 with respect to the X-axis and the target values y1, y2 with respect to the Y-axis are then fed to the signal generator 21x for the rotation angle about the X-axis and the signal generator 21y for the rotation angle about the Y-axis, respectively. The signal generator 21x for the rotation angle about the X-axis generates signals for the rotation angle about the X-axis, having periodic waveforms with respect to the X-axis as shown in Fig. 5, on the basis of the target values x1, x2 from the target value generator 20. Likewise, the signal generator 21y for the rotation angle about the Y-axis generates signals for the rotation angle about the Y-axis, having periodic waveforms with respect to the Y-axis as shown in Fig. 5, on the basis of the target values y1, y2 from the target value generator 20. Incidentally, the waveform of the signal for the angle of rotation about the X-axis and that of the signal for the angle of rotation about the Y-axis have a 90° phase shift. The phase shift allows to minimize the driving frequencies about each axis to move to four positions in a repeated manner, and consequently to reduce in power consumption. When the respective signal generators 21x, 21y for the rotation angles about the X- and the Y-axis generate signals for the rotation angles as shown in Fig. 5, the comparison circuits 21x, 21y compare these signals for the rotation angles as the control values with detection signals for the rotation angles about the X- and the Y-axis which are outputted from the angle detector 26, and output signals which reflect the differences between the two associated signals. These difference signals are amplified through the amplifiers 23x, 23y, pass through the phase compensation circuits 24x, 24y and are then inputted to the respective drivers 25x, 25y for the X- and the Y-axis. The drivers 25x, 25y feed driving currents in opposing directions to coils 8 of the pair of opposite voice coil motors 5x, 5y. Thereby the refracting plate 1 is inclined about the X- and the Y-axis, and these inclination angles are detected by the respective angle detectors 26. Then, the detection outputs are inputted to the comparison circuits 22x, 22y, and thus rotation angles of the refracting plate 1 are fed back to be controlled so as to correspond to the target angles x1, x2, y1, y2. Here, in Fig. 5 one cycle period is an interval of time required to set the refracting plate 1 to the positions of a total of four angles, namely, which are determined by combination of two rotation angles of the refracting plate 1 about the X-axis and two rotation angles of the refracting plate 1 of the Y-axis. Specifically, the angles are set to become (x1, y1), (x2, y1), (x2, y2) and (x1, y2) in periods T1, T2, T3 and T4 within one cycle period, respectively. The image outputs of the subject picked up by the solid state imaging element in the respective periods T1-T4 are written into memories as shown in Fig. 29, and the data for four frames outputted from each memory are composed to obtain an image with a resolution which is roughly doubled both horizontally and vertically. Likewise, in the case where a mode control signal for setting a quadruple resolution is inputted, it is required to shift the image on a Px/4 basis horizontally and on a Py/4 basis vertically wherein Px and Py are horizontal and vertical pitches of the respective pixels of the solid state imaging element. For one cycle period, the refracting plate 1 is set to be at a total of sixteen combination positions of rotation angles, namely four angular positions about the X-axis and four angular positions about the Y-axis. Composing the data for sixteen frames of the subject which are picked up by the solid state imaging element, an image with a resolution which is roughly quadruple both horizontally and vertically. In the case where a normal mode control signal is inputted from a controller 19, target values x, y for a given rotation angle are outputted from the target value generator 20. Therefore, the inclination angle of the refracting plate 1 is held at a given angle without being changed. For example, in the case where the target values x = 0, y = 0, the refracting plate 1 is maintained in a state that it is at right angles to the optical axis (Z-axis). Accordingly, the composition of frames is not executed, and the image picked up by the solid state imaging element is directly outputted. An explanation will now be given regarding the concrete configuration of the angle detector 26 used in the control circuit part as shown in Fig. 4 which drives the actuator part. Fig. 6 is a side view of the angle detector which shows its configuration, and Fig. 7 is a front view of the light receiving portion of the angle detector when viewed from the light incidence end. In Fig. 6, the vertical direction, the lateral direction and the direction orthogonal to the plane of the paper correspond to the Z-axis direction, the Y-axis direction and the X-axis direction, respectively. This angle detector 26 comprises a light emitting portion 27 and a light receiving portion 28, wherein the light emitting portion 27 is composed of a light emitting device such as an LED, while the light receiving portion 28 is composed of four light receiving elements such as phototransistor, as a so-called four-part split photodetector. The light emitting portion 27 is positioned so that the light emitted therefrom enters the center position where the refracting plate 1 intersects the z-axis of the refracting plate 1, at an angle of . The light receiving portion 28 is positioned on the path of the light reflected by the refracting plate 1, which has been emitted from the light emitting portion 27, and both the light emitting portion 27 and the light receiving portion 28 are fixed to a part of a cabinet of the solid state imaging element. In order to guide the light from the light emitting portion 27 to the light receiving portion 28 with high efficiency, it is preferred to additionally provide a condensing lens, a collimator lens or the like. Assuming that the refracting plate 1 is positioned at an angle where the refracting plate 1 is at right angles to the optical axis (Z-axis), without being inclined, the light from the light emitting portion 27 is equally applied to the four light receiving elements 29a-29d of the light receiving portion, as indicated by the alternate long and short dash line in Fig. 7. When the additive signal of the detection outputs of a pair of right and left light receiving elements 29a, 29b is designated with X 1 , the additive signal of the detection outputs of the other pair of right and left light receiving elements 29c, 29d with X 2 , the additive signal of the detection outputs of a pair of upper and lower light receiving devices 29a, 29d with Y 1 and the additive signal of the detection outputs of the other pair of upper and lower light receiving elements 29b, 29c with Y 2 , all the difference signals (X 1 - X 2 ) and (Y 1 - Y 2 ) are 0. In the case where the refracting plate 1 is rotated about the X-axis initially in the aforementioned state, the light from the light emitting portion 27 cannot be equally applied to the respective light receiving devices 29a-29d of the light receiving portion 28, and the additive signal X 1 of the detection outputs of the pair of right and left light receiving devices 29a and 29b and the additive signal of the detection outputs of the other pair of right and left light receiving devices 29c and 29d have different values. Therefore, the difference signal (X 1 - X 2 ) which reflects the difference between the two values cannot be 0, and a detection output which depends on the rotation angle is produced. Additionally, the aforementioned angle detector 26 is designed so that the light receiving portion 28 receives the light from the light emitting portion 27 after being reflected by the refracting plate 1; nevertheless, as shown in Fig. 8, the light emitting portion 27 and light receiving portion 28 may be located across the refracting plate 1 so that the light receiving portion 28 receives the light which has been emitted from the light emitting portion 27 and has passed through the refracting plate 1. In this case, however, the angle detector 26 must be adjusted for the geometric configurational relationship between the light emitting portion 27 and light receiving portion 28 in order not to obstruct the incidence of the light from the subject onto the solid state imaging element. Although the angle detector 26 has the light receiving portion 28 provided separatedly from the solid state imaging element, the solid state imaging element itself may also be made to work as the light receiving portion. Fig. 9 shows the constitution of a solid state imaging element, wherein no special-purpose light receiving portion is provided, and the solid state imaging element is also designed to work as a light receiving portion instead. The solid state imaging element 30 comprises a matrix of light receiving elements 31-38, 39a-39d arranged horizontally and vertically, which form pixels, wherein the light from the subject enters only the imaging region 41 boxed by the broken line of the figure; the outer region of a boundary line is an inoperative region 42 which does not directly take part in imaging. The inoperative region 42 is generally called as an optical block. The light receiving elements of the optical block region are shielded from light by applying aluminum or the like thereto and environmental effects of temperature, humidity, and the like on the solid state imaging element 30 can be corrected by obtaining the difference between the output of the pixels of the imaging region 41 and the average output of the pixels of the inoperative region 42. Additionally, regarding the optical block, there are 20-40 pixels per horizontal line. Since practically the average of the whole light receiving elements of the optical block may be obtained as mentioned above, no problematic bad influence is not caused even when about two elements are used as sensors. However, since the light receiving elements of the optical block are shielded from light in the general solid state imaging element, it is necessary to provide a not-shielded region by masking or the like in advance. Accordingly, the optical system is adjusted so that light receiving elements 39a-39d constituting a part of the inoperative region 42 formed in such manner are constructed as the light receiving portion and so that light from the light emitting portion 27 passes through the refracting plate 1 and enters the light receiving devices 39a-39d. Also in this case, the detection of the respective amounts of light received by the light receiving devices 39a-39d serves to detect the inclination angles of the refracting plate 1 in the same manner as that of the above-mentioned light receiving portion 28. Furthermore, since there is no need to provide a dedicated separate light receiving portion 28 for receiving light from the light emitting portion 27, the cost may be lowered by its omission. Here, it is to be noted that the angle detector 26 may be a reflection type photointerrupter or non-contact displacement sensor, or it is possible to measure the displacement of the refracting plate 1 to convert to an angle by providing the refracting plate 1 with a lightshielding flag and using a transmitting type photointerrupter. Fig. 10 shows the shape of a gimbaling mechanism element of another embodiment of the invention. In the embodiment, since the parts of the embodiment corresponding to those of the embodiment as shown in Fig. 1, 2 are designated with the same reference numerals, the description will be eliminated. In the gimbaling mechanism element as shown in Figs. 1, 2, all the rotation supporting portions 2cx, 2cy of the gimbaling mechanism element 2 are rectangular-shaped in cross section, but more preferably are bobbin shaped. Here, the term "bobbin shaped" means that the width of the center portion is gradually reduced in comparison with that of both ends. The reason why such shape is preferred is that while the oscillation in the Z-axis direction only constitutes unwanted disturbance to the components of rotation about the X-axis and Y-axis, the unwanted oscillation around the Z-axis may be undoubtedly suppressed by employing the bobbin shape. Simply speaking, while the lengths L of the respective rotation supporting portions 2cx, 2cy of the rectangle as shown in Figs. 1, 2 may be shortened to increase their spring constants, the torsional rigidity increases adversely in the case where the lengths L of the rotation supporting portions are excessively short, and as a result increased driving force is required for rotation of the refracting plate 1 about the X- and the Y-axis. On the other hand, in the case where the rotation supporting portions are bobbin shaped, their lengths L may be shortened to equivalently increase their spring constants without increasing their torsional rigidity, and therefore the refracting plate 1 may be rotated about the X- and the Y-axis by a relatively small driving force while suppressing the unwanted oscillation in the Z-axis direction. Such bobbin shaped gimbaling mechanism element 2 is easily formed by etching in the case where it is made of a material such as a metal, and thus the cost increase caused by employing such shape is extremely small. Next, an explanation will be given regarding the details of designing the rotation supporting portions 2cx, 2cy. Servo characteristics preferable as to controllability of the embodiment shown in Figs. 1, 2 or Fig. 10 are shown as a Bode diagram in Fig. 11. In Fig. 11, the axis of ordinate indicates gains (dB) and the axis of abscissa indicates frequencies (Hz). The peak designated with 50a indicates the resonance of rotational oscillation in the rotation supporting portions 2cx, 2cy of the gimbaling mechanism element 2 and the frequency is 43 Hz. The peak designated with 50b indicates the resonance of oscillation in the Z-axis direction and the frequency is 430 Hz. In other words, ten times the resonance frequency at the peak 50a is the resonance frequency at the peak 50b. This means that in the case where the resonance frequency of oscillation in the Z-axis direction is ten times or less the resonance frequency of rotational oscillation of the rotation supporting portions, the gain margin becomes 10 dB or less which causes unstable control. Accordingly, the entire structure must be constructed in such a manner that the resonance frequency of oscillation in the Z-axis direction is ten times or more the resonance frequency of the rotational oscillation. When in consideration of the resonance frequency of each oscillation and the above-mentioned matters, the shapes of the rotation supporting portions are ones within a certain scope, it becomes possible to satisfy the abovementioned requirements and establish stability of servo controlling. Now, fundamental view points regarding the relationship between the shape of the rotation supporting portions and the resonance frequency will be described, giving an example of tortion of a rectangular section for obtaining the resonance frequency and a maximum of generated shear stress. An explanation for the case where x ≧ y will be given with reference to the rectangle shown in Fig. 12, wherein "x", "y", "z", "E ", "ν" and " α" are the width, thicknes, length, Young's modulus, the Poisson's ratio, and tortion angle, respectively. An approximate equation based on the theory of elasticity for the torsional-moment "T" which is required when torsion is exerted about an axis vertical to the section of the rectangle is expressed as an equation (3). When the spring constant at the time of the rotational oscillation is expressed as "K", T = αK, and the resonance frequency "f" of the rotational oscillation is expressed as an equation (4) considering the moment of inertia "I" and the spring constant "K" at the time of the rotational oscillation. An approximate equation based on the theory of elasticity for a maximum shear-stress when the torsion angle is α, is given as an equation (5). A change in "x" and "y" in the equations (3)-(5) holds for those equations in the case of x < y. T = a z { 1 3 · E 2(1 + ν) xy 3 - 64 π 5 · Ey 4 2(1 + ν) · tanh ( π 2 · x y )} = αK f = 1 2π E 2(1+ν) · y 3 I z { x 3 - 64y π 5 · tanh( πx 2y ) } σ = 4 x E α tanh ( πy 2x ) π 2 1 + ν z In order to obtain the resonance frequency of the oscillation in the Z-axis direction, an example of torsion of a rectangle-section rod will be described below. Fig. 13 shows the case where two rectangles 51 shown in Fig. 11 support a mass body 52 having a mass m. The amount of deflection when a force "F" is exerted on the mass body 52 is expressed as "d". The force "F" is given by an equation (6) on the basis of the theory of elasticity. Then F = Ld wherein "L" is the spring constant in the deflection direction. Accordingly, the spring constant "L" is given by an equation (7). F = 2 Exy 3 d z 3 L = 2 Exy 3 z 3 Next, the resonance frequency is given by an equation (8) when the model with the above mentioned configuration for the oscillation of the gimbaling mechanism element in the Z-axis direction is replaced by mass bodies 53, 54 having masses m 1 , m 2 , respectively and coupled springs 55, 56 having spring constants L 1 , L 2 , respectively. f = 1 2π 1 2m 1 m 2 {m 1 L 2 +m 2 (L 1 + 2 )- {m 1 L 2 +m 2 (L 1 +L 2 )} 2 -4m 1 m 2 L 1 L 2 } Considering the above, the resonance frequency of the rotation supporting portions of the gimbaling mechanism element may be expressed on the basis of the relational expressions regarding torsion and deflection of a rectangle-section rod. Since the relational expressions are different between the cases of a ≧ y and a ≦ y and between the cases of x ≧ y and x ≦ y, now the cases of a ≧ y and a ≦ y will be described, and the description of the cases of x ≧ y and x ≦ y will be aa further explanation will be given separately thereafter. Figs. 15A-15C shows the constitution of the gimbaling mechanism element 2 of Fig. 2. Fig. 15A is a plan view and Figs. 15B, 15C are enlarged perspective views of the rotation supporting portions 2cx, 2cy of the X- and the Y-axis, respectively. In the rotation supporting portion 2cx of the X-axis are designated the width, thickness, length, inertia moment of rotation about the rotation supporting portion 2cx with "x", "y", "z", and I x , respectively. On the other hand, in the rotation supporting portion 2cy of the Y-axis are designated the width, thickness, length, inertia moment of rotation about the rotation supporting portion 2cy with "a", "y", "L", and I y , respectively. Additionally the mass of the outer frame part 2b, the mass of the inner frame part 2a, the Young's modulus of the supporting portion of the gimbaling mechanism element 2, the Poisson's ratio of the supporting portion of the gimbaling mechanism element 2, and the inclination angle of the refracting plate 1 at the time of rotation about a given axis are designated with "M 1 ", "M 2 ", "E", "ν", and "α". The relational expression between the resonance frequency of the rotation supporting portion and the shape of the cross section of the rotation supporting portion is given by the equation (4). Accordingly, the resonance frequency f x of the rotational oscillation about the X-axis is given by an equation (9), while the resonance frequency f y of the rotational oscillation about the Y-axis is given by an equation (10). f x = 1 2π Ey 3 I x (1 + ν) { x 3z - 64 y π 5 z tanh( πx 2y ) } f y = 1 2π Ey 3 I y (1 + ν) { a 3L - 64 y π 5 L tanh( πa 2y ) } Additionally, the resonance frequency f z of the oscillation in the Z-axis direction is given by an equation (11) derived from the equation (8). f z = 1 2π × Ey 3 2m 1 m 2 {m 1 x z 3 + m 2 ( x z 3 ) + a L 3 - m 1 2 ( x z 3 ) 2 + m 2 2 ( x z 3 + a L 3 ) 2 - 4m 1 m 2 ( ax Z 3 L 3 ) } The resonance frequencies f x , f y are desired to have an identical value for the purpose of simplification of designing a servo range. In the case where the values of the two are different, in view of the above-mentioned servo stability, larger one of the two values, designated with " f m ", is selected to satisfy the following relationship: 10f m < f z In the following the case of f m = 10 f x < f y will be described. Assuming that 10f x = 10f m < f z from the equation (11) and that the thickness "y" has a given value, from the relationship between {a/(10f m ) 2 /L 3 } and {x/(10f m ) 2 /z 3 } is established the diagonally shaded area in Fig. 16A. The relationship between the shape of the rotation supporting portion section and the shearing stress "σ" to be exerted on the rotation supporting portion when the refracting plate is inclined is given by the equation (5). Accordingly, in the case where the refracting plate is inclined by an angle of α about the X-axis, a maximum shearing stress σ x is given by the equation (12), while a maximum shearing stress σ x when the refracting plate is inclined by an angle of α about the Y-axis is given by an equation (13). σ x = 4 x E α tanh ( πy 2x ) π 2 (1 + ν)z σ y = 4 a E α tanh ( πy 2a ) π 2 (1 + ν) L It is necessary that the stress to be exerted on the rotation supporting sections is set to satisfy the relationship: σ max ≧ σ x , σ y wherein σ max is the fatigue limit which is a material characteristic of the rotation supporting portions. Accordingly, from the equation (12) and σ max ≧ σ x , the length z exists within the range defined by an equation (14). z ≧ 4 x E α tanh πy 2x π 2 (1 + ν) σ max Likewise, from the equation (13) and σ max ≧ σ y the length L exists within the range defined by an equation (15). Additionally, from the equation (9), {a/(10f x ) 2 /L 3 } and {x/(10f x ) 2 /z 3 } are expressed as an equation (16) and an equation (17), respectively. L ≧ 4 a E α tanh πy 2a π 2 (1 + ν) σ max A minimum width which is determined by the limits of workable width of the rotation supporting portions is expressed as a min or x min . A minimum length which is determined by the limits of workable length is expressed as L min or z min . From the equation (14) and the relationships: x ≧ x min and z ≧ z min , for example, the diagonally shaded area in Fig. 17A is established. From the equation (15) and the relationships: f x ≧ f y , a ≧ a min and L ≧ L min , the diagonally shaded area in Fig. 18A is established. The (x, z) wherein the value of the equation (17) arrives at the maximum within the diagonally shaded area in Fig. 17A is expressed by (x 1 , z 1 ). When the (x 1 , z 1 ) is substituted for (x, z) in the equation (16), the following equation (18) is obtained: The (a, L) wherein the value of the equation (18) arrives at the maximum within the diagonally shaded area in Fig. 18A is expressed by (a 1 , L 1 ). From (x, z) = (x 1 , x 1 ), (a, L)=(a 1 , L 1 ), the equation 16 and equation 17, maximum values of {a/(10f m ) 2 /L 3 } and {x/10f m ) 2 /z 3 } are obtained as {a/(10f m ) 2 /L 3 } maxa and {x/(10f m ) 2 /z 3 } maxa , respectively, and the diagonally shaded area in Fig. 19A restricted by the maximum values and the diagonally shaded area in Fig. 15A is obtained. Also in the case where f x ≦ f y = f m , {a/(10f m ) 2 /L 3 } and {x/(10f m ) 2 /z 3 } are restricted in the same manner as the above. Accordingly, as long as given values for the thickness of the rotation supporting sections and the angle of inclination of the refracting plate are within the diagonally shaded area in Fig. 19A which determines the shape of the gimbaling mechanism element, a servo range for shifting of pixels may be established as desired, and driving may be performed with a high degree of reliability for a long period of time. An explanation will now be given regarding the case where a ≦ y and x ≦ y. Regarding the relational expression for the resonance frequency of the rotation supporting portions and the shape of the cross section of the rotation supporting portions, the resonance frequency f x of the rotational oscillation about the X-axis is represented by an equation (19), while the resonance frequency f y of the rotational oscillation about the Y-axis is represented by an equation (20). fx = 1 2π Ex 3 I x (1 + ν) { y 3 z - 64x π 5 z tanh ( πy 2x ) } fy = 1 2π Ea 3 I y (1 + ν) { y 3 L - 64a π 5 L tanh ( πy 2a ) } In the same manner as in the above case where a ≧ y and x > y, f x and f y are desired to have an identical value for the purpose of simplification of designing a servo range. In the case where the values of the two are different, in view of the above-mentioned servo stability, larger one of the two values, designated with " f m ", is selected to satisfy the following relationship: 10f m ≦ f z In the following the case of f m = 10 f x ≧ f y will be described. Assuming that 10f x = 10f m ≦ f z from the equation (11) and that the thickness "y" has a given value, from the relationship between {a/(10f m ) 2 /L 3 } and {x/(10f m ) 2 /z 3 } is established the diagonally shaded area in Fig. 16B. In the case where the refracting plate is inclined by an angle of α about the X-axis, a maximum shearing stress σ x is given by an equation (21), while a maximum shearing stress σ x when the refracting plate is inclined by an angle of α about the Y-axis is given by an equation (22). σ x = 4 y E α tanh ( πx 2y ) π 2 (1 + ν) z σ y = 4 y E α tanh ( πa 2y ) π 2 (1 + ν) L It is necessary that the stress to be exerted on the rotation supporting sections is set to satisfy the relationship: σ max ≧ σ x , σ y wherein σ max is the fatigue limit which is a material characteristic of the rotation supporting portions. Accordingly, from the equation (21) and σ max ≧ σ x , the length z exists within the range defined by an equation (23). The length L likewise exists within the range defined by an equation (24). z ≧ 4 y E α tanh ( πx 2y ) π 2 (1 + ν) σ max L ≧ 4 y E α tanh ( πa 2y ) π 2 (1 + ν) σ max Additionally, from the following equation (25), {a/(10f x ) 2 /L 3 } and {x/(10f x ) 2 /z 3 } are expressed as an equation (26) and an equation (27), respectively. f x = 1 2π Ex 3 I x (1 + ν) { y 3z - 64x π 5 z tanh ( πy 2x ) } A minimum width which is determined by the limits of workable width of the rotation supporting portions is expressed as a min or x min . A minimum length which is determined by the limits of workable length is expressed as L min or z min . From the equation (23) and the relationships: x ≧ x min and z ≧ z min , for example, the diagonally shaded area in Fig. 17B is established. From the equation (24) and the relationships: f x ≧ f y , a ≧ a min and L ≧ L min , the diagonally shaded area in Fig. 18B is established. The (x, z) wherein the value of the equation (27) arrives at the maximum within the diagonally shaded area in Fig. 18B is expressed by (x 2 , z 2 ). When the (x 2 , z 2 ) is substituted for (x, z) in the equation (26), the following equation (28) is obtained. The (a, L) wherein the value of the equation (20) arrives at the maximum within the diagonally shaded area in Fig. 19B is expressed by (a 2 , L 2 ). From (x, z) = (x 2 , z 2 ), (a, L)=(a 2 , L 2 ), the equation (26) and the equation (27), maximum values of {a/(10f m ) 2 /L 3 } and {x/(10f m ) 2 /z 3 } are obtained as {a/(10f m ) 2 /L 3 } maxb and {x/(10f m ) 2 /z 3 } maxb , respectively, and the diagonally shaded area in Fig. 19B restricted by the maximum values and the diagonally shaded area in Fig. 16B is obtained. Also in the case where f x ≦ f y = f m , {a/(10f m ) 2 /L 3 } and {x/(10f m ) 2 /z 3 } are restricted in the same manner as the above. Accordingly, as long as given values for the thickness of the rotation supporting portions and the inclination angle of the refracting plate are within the diagonally shaded area in Fig. 19B which determines the shape of the gimbaling mechanism element, a servo range for shifting of pixels may be established as desired, and driving may be performed with a high degree of reliability for a long period of time. The aforementioned relationships hold also for the combination of a ≧ y and x ≦ y and the combination of a ≦ y and x ≧ y, in order to establish ranges for optimum shapes of the rotation supporting sections. Although the shapes defined by a ≧ y and x ≧ y are preferred since they allow reduction in the thickness of the gimbal mechanism element and produce effects including easy workability, lower power consumption due to lower thrust attributable to decrease in the rotation-axial moment of inertia, etc., a servo stability may be established also for the case where a ≦ y and x ≦ y as mentioned above. Considering the aforementioned points of view, with rotation supporting sections of a gimbaling mechanism element for use in 1/3-inch or 1/4-inch CCD-based consumer-oriented moving or still picture camera, experiments were carried out to observe the relationship between the {a/(10f m ) 2 /L 3 } and {x/(10f m ) 2 /z 3 } for satisfactory servo characteristics, with results plotted in Fig. 20. Reference to Fig. 20 establishes both 2 < x/(10f m ) 2 /z 3 < 11 (m -2 HZ -2 ) and 3 < a/(10f m ) 2 /z 3 < 15 (m -2 HZ -2 ). As above-mentioned, Fig. 11 illustrates the servo characteristics of the embodiment of Fig. 1. If a resonance gain of oscillation in the direction of the Z-axis becomes lower, a wider range of servo characteristics is obtained. The resonance gain may be lowered by controlling the thrust of at least one of the two voice coil motors facing across a given axis of rotation. The following is an explanation of a method of controlling the thrust of the voice coil motors. Fig. 21 illustrates the details of the drivers 25x, 25y shown in Fig. 4 for driving the voice coil motors. Thrust controlling means 60, 61 of the voice coil motors 5x, 5y drive drivers 62, 63 for driving the voice coil motors, respectively. The same as the thrust controlling means 60, 61, thrust controlling means 64, 65 drive drivers 66, 67, respectively. Adjustment is made by driving either of the X- and the Y-axis of the voice coil motors. The thrust controlling means 60, 61, 64, 65 are realized by using general operational amplifiers, and the voltages inputted to the drivers 62, 63, 66, 67 may be controlled by adjusting their gain. The drivers 62, 63, 66, 67 are general current amplification circuits, which provide the voice coil motors with current proportional to the inputted voltages. An explanation will be first given regarding the rotation about the X-axis. Transfer characteristics of an open loop are measured to determine the peak height of the resonance gain 50b of oscillation in the Z-axis direction, as shown in Fig. 11. Then, a signal at whose frequency resonance occurs is inputted and the thrust controlling means 60 or 61 is adjusted so as to minimize the resonance gain. The adjustment made in this way allows lowering in the resonance gain 50b of oscillation in the Z-axis direction to provide a wider servo range, thus improving the control characteristics. Next, also for oscillation about the Y-axis, the thrust adjusting means 64 or 65 is adjusted so as to minimize the resonance gain 50b of oscillation in the Z-axis direction. In this way servo characteristics are established over a wide range the same as in the case of the X-axis. The configuration discussed above is that for driving two axes intersecting at right angles. With this configuration, when rotation is attempted, for example, about the X-axis, there may be caused a so-called interaction, that is, rotation about the Y-axis, in the case where the points of application of the voice coil motors are not on the Y-axis crossing the X-axis at right angles. The amount of the interaction, however, is so small that the picture quality is not adversely affected in shifting pixels, and therefore no trouble is caused. The gimbaling mechanism element 2 of Fig. 22 and Fig. 23 show the constitution of a gimbaling mechanism element of another embodiment of the invention. The gimbaling mechanism element as shown in Figs. 1, 2 is integratedly formed of a metal film by etching or the like, while a gimbaling mechanism element of the embodiment is constituted by combining various members. Fig. 22 is a perspective view of the gimbaling mechanism element of the embodiment, and Fig. 23 is a plan view of the gimbaling mechanism element. In the gimbaling mechanism element of the embodiment, a rectangular outer frame 71 is disposed outside a rectangular inner frame 70. Bent portions 70x are formed in the inner frame 70 by bending the perimeters of two inner-frame sides opposite to each other. In turn, the outer frame 71 is formed with bent portions 71x, 71y, of which 71x are formed by bending the inner perimeters of two outer-frame sides opposite to the two inner-frame sides, respectively, and of which 71y are formed by bending the outer perimeters of the other two outer-frame sides at right angles to the two inner-frame sides. The inner frame 70 is reinforced with its respective bent portions 70x, while the outer frame 71 is reinforced with its respective bent portions 71x, 71y. In addition, rotation shafts 72x are attached bridging the midpoints of the bent portions 70x, 71x of the inner frame 70 and outer frame 71, and the inner frame 70 is pivotably supported with the outer frame 71 via the rotation shafts 72x. On the other hand, one end of each rotation shaft 72y is attached to the midpoint of each of the other bent sections 71y of the outer frame 71, while the other end of each rotation shaft 72y is rotatably attached to each cabinets 73. The outer frame 71 is pivotably supported with the cabinets 73 via the rotation shafts 72y. Accordingly, the gimbaling mechanism element shown in Figs. 22, 23 also has a freedom of biaxial rotation about the X- and the Y-axis, regarding the rotation about the respective rotation shafts 72x, 72y. Coil springs 74 are wound around the respective rotation shafts 72x, 72y. Both ends of each coil spring 74 are fixed to the respective bent portions 70x, 71x of the inner and outer frames 70, 71 or to the bent portions 71y of the outer frame 71 and the cabinet 73. Thereby, when the pressure of the voice coil motors to the inner frame 70 is released, the inner and outer frames 70, 71 are braced so as to return to their home positions. Also in the embodiment of Figs. 22, 23 the refracting plate 1 is fixed to the inner circumference of the inner frame 70, and the respective bobbins 7 of the four voice coil motors 5 are bonded to be fixed to the midpoints of the respective sides of the inner frame 70. As a control circuit part for driving the actuator part, it is preferable that the configuration as shown in Fig. 24 is employed for more stable operation of the actuator. Regarding the configuration as shown in Fig. 24, the image data obtained by imaging the subject with the solid state imaging apparatus 30 is digitized via an A/D converter 81, and is stored in a memory 82 after being subjected to a variety of image processings. A movement vector detector 83 then makes a comparison between the image data obtained at the current angle position and the image data obtained at the immediately preceding angle position in response to the mode control signals from the controller 19 to arithmetically operate the movement vector therebetween. This calculation may be performed by, for example, any well-known technique including the representative points matching approach. The target value generator 20 compares the vector provided by the movement vector detector 83 with the vector of the movement target value to correct the target value successively by correcting the difference. Since such correction makes possible the correction on the basis of the image data directly obtained with the solid state imaging element 62, sequential correction is carried in response to possible changes of the actuator with time and changes in a variety of constants, thus ensuring stable operation. Here, it is to be noted that the correction is not required to be continuously conducted. The correction may be conducted each time a given time elapses or only when inputting is manually performed. Since the other components shown in Fig. 24 are the same as those shown in Fig. 4, they are designated with the same reference numerals to omit their explanation. The invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and the range of equivalency of the claims are therefore intended to be embraced therein.

Claims: An imaging apparatus in which a refracting plate (1) is arranged to transmit light from a subject toward a solid state imaging element (30) for imaging the subject and means (2, 5) is providing for inclining the refracting plate (1) so as to shift the optical axis of light incident upon the solid state imaging element (30) in the arrangement direction of the solid state imaging element, the inclining means including: a gimbaling mechanism element (2) in which the refracting plate (1) is mounted and in which there is provided rotation supporting means (2cx, 2cy; 72x, 72y) for supporting the refracting plate (1) rotatably about two rotational axes extending in two directions at right angles to each other, and a plurality of drive devices (5), each having a displaceable portion capable of advancing and retreating, said displaceable portions being arranged to act so as to effect controlled rotation of the refracting plate about said respective rotational axes, characterised in that the refracting plate (1) is arranged between a lens for condensing the light from the subject and the solid state imaging element, and in that said gimbaling mechanism element comprises a first support member (2a; 70) on which said refracting plate is mounted and a second support member (2b; 71), the rotation support means comprising first and second rotational support portions provided in the areas of respective edges of the refracting plate, the first support member being rotatably connected to the second support member about a first of said rotational axes (X) by first said rotational supporting portions (2cx; 72x), and the second support member being rotatably supported about a second of said rotational axes (Y) by second said rotational supporting portions (2cy; 72y), and the displaceable portions being connected to the midpoints of said edge areas of the refracting plate so as to confront each other about the respective rotational axes. An imaging apparatus according to claim 1, wherein said first support member is an inner rectangular frame part and said second support member is an outer rectangular frame part. An imaging apparatus according to claim 2, wherein said inner and outer frame parts and said first and second rotational supporting portions are integrally formed from a metal thin plate. An imaging apparatus according to claim 3, wherein said gimbaling mechanism element further includes inner and outer rectangular reinforcing plates (3, 4) respectively fixed to said inner and outer frame parts. An imaging apparatus according to any of claims 1 to 4, wherein said drive devices are arranged in pairs, the devices of each respective pair being disposed on opposite sides of the respective rotational axis about which those devices effect controlled rotation of the refracting plate. An image apparatus according to claim 5 when dependent directly or indirectly on claim 2, wherein the displaceable portions (7) of each respective pair of drive devices (5) are attached to opposite sides of the inner rectangular frame part (2a, 70). The imaging apparatus of any preceding claim, wherein said drive devices (5) are voice coil motors. An imaging apparatus according to any preceding claim, wherein each of said rotation supporting portions is bobbin-shaped in that its width gradually reduces from its end portions towards its centre portion. An imaging apparatus according to claim 7, wherein the imaging apparatus comprises: target value generating means (20) for generating signals wherein target values for the inclination angle of the refracting plate (1) are made different according to a preset resolution; angle detecting means (26) for detecting the inclination angle of the refracting plate (1); and control means (19) for comparing the target value represented by a signal outputted from the target value generating means (20) and the inclination angle of the refracting plate (11) detected by the angle detecting means (26) and for controlling thrusts to advance and retreat the displaceable portions of the voice coil motors (5) according to the difference therebetween. An imaging apparatus according to claim 9, wherein the angle detecting means (26) comprises a light emitting element (27), and is set so that the light from the light emitting element (27) which has been passed through or reflected on the refracting plate (1) is applied to an invalid region beyond the subject imaging region of the solid state imaging element (30), and the inclination angle of the refracting plate is detected from the position of the light applied to the invalid region. An imaging apparatus according to claim 9, wherein the imaging apparatus comprises movement vector detecting means (83) for comparing the image data obtained at the current inclination angle of the refracting plate (1) with the image data obtained at its immediately preceding inclination angle to arithmetically operate the movement vector between images and for outputting a signal for correcting the target value outputted from the target value generating means (20) on the basis of the arithmetical operation result. An imaging apparatus according to claim 1, wherein a frequency f m s satisfies the following expressions: 2 ≦ x/(10f m ) 2 /z 3 ≦ 11 (m -2 Hz -2 ) and 3 ≦ a/(10f m ) 2 /z 3 ≦ 15 (m -2 Hz -2 ) wherein "z" and "x" are respectively the length and width of the rotation supporting portions of the gimbaling mechanism element (2) in one of the two directions at right angles to each other, namely the X-axis direction, and f x is the resonance frequency of the rotational oscillation about the X-axis: L and a are respectively the length and width of the rotation supporting portions in the other of the two directions, namely the Y-axis direction, and f y is the resonance frequency of the rotational oscillation about the Y-axis; and f m is the larger frequency of the resonance frequencies f x , f y . An imaging apparatus according to claim 7, wherein regulating means for making variable the thrust of at least one of the voice coil motors (5) confronting each other through the respective rotation axes is provided. An imaging apparatus according to claim 7, wherein the voice coil motors (5) are of a moving coil type and the shapes of the sections thereof vertical to the movement directions of the coils are semicircular.

Inventors: NISHIKAWA MASAYUKI, OKADA HIDEO, OKUDA TOHRU, NISHIKAWA, MASAYUKI, OKADA, HIDEO, OKUDA, TOHRU
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1995
Main classification: H04N5
IPC codes: H04N5, H04N3