JP2533876Y2 - Differential transformer type position and speed detection circuit for auto focus of video camera and linear motor with differential transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position and speed detection circuit using a differential transformer suitable for autofocus such as a video camera as a sensor, and a linear motor having a differential transformer.

2. Description of the Related Art Conventionally, a video camera employs a double lens barrel of an autofocus method for automatically focusing, and a movable lens barrel is housed in a fixed lens barrel. This movable lens barrel is driven by a linear motor included in a servo system. At the time of driving, the linear motor receives a composite signal including an autofocus signal indicating an amount of deviation from a correct focal length, a position detection signal of the lens held by the movable lens barrel, and a speed detection signal thereof.

A capacitance sensor is used for detecting the position of such a lens, and a damping coil is used for detecting the speed of the lens. Incidentally, as shown in FIG. 8, the capacitance type sensor is composed of one copper plate 10 and two copper plates 12 and 14 arranged in parallel with and spaced from each other. And the copper plates 12 and 14 are mounted on a movable lens barrel. Then, a capacitor having a large capacitance (not shown) is connected between the copper plate 10 and the common potential, and different frequencies, for example, 100 KHz and 200 KHz AC voltage are applied to the terminals 16 and 18 of the copper plates 12 and 14, respectively. An AC voltage having a frequency obtained by combining the two AC voltages with the terminal 20 of the copper plate 10 is obtained. The amount of displacement of the copper plates 12, 14 with respect to the copper plate 10 is detected from the output voltage, and the lens position of the movable lens barrel can be known.

However, in order to detect the position and speed of the lens as described above, two components, a capacitive sensor and a damping coil, which have completely different properties, are required for handling and adjustment. There are various disadvantages. In addition, it is difficult to reduce the size and cost of the video camera in terms of space and cost.

The present invention has been made in view of such conventional problems, and has a differential transformer type position and speed detection circuit for auto-focusing of a video camera suitable for improving the performance of the product, miniaturizing the product, and reducing the cost. It is an object to provide a linear motor with a differential transformer.

Means for Solving the Problems Means for achieving the above object will be described below with reference to FIGS. 1, 2, 5, and 7 corresponding to the embodiment.

A differential transformer type position and speed detection circuit 60 for auto focus of the video camera is connected to secondary coils 50 and 52 differentially connected to the primary coil 48 and the movable core 54 to the auto focus type double lens barrel of the video camera. The differential transformer 24 having the following is installed. A sine wave generator 62 for generating a sine wave AC voltage for excitation is provided on the side of the primary coil 48 of the differential transformer 24, and the amount of displacement of the movable core 54 is A rectifier 64 for rectifying a proportional secondary coil differential output voltage is provided. The rectified output is input, and a DC voltage corresponding to the lower frequency band is connected to the movable core 54. A lens position detection signal of a movable lens barrel. And a differentiator 72 that similarly receives a rectified output and outputs a voltage proportional to the differential value as a lens speed detection signal of the movable lens barrel.

The linear motor with a differential transformer for auto focus of the video camera is located near or inside the yoke 28 (80) of the linear motor 22 (74) for driving the movable lens barrel of the auto focus double lens barrel of the video camera. Next coil 48 (10
0) and the secondary coil 50 differentially connected to the movable core 54 (106),
A differential transformer 24 (76) having 52 (102, 104) is provided. When the differential transformer 24 is installed near the outside of the yoke 28 of the linear motor 22, the linear motor 22 includes an axial cylindrical permanent magnet 26, Cylindrical coil housed movably between such permanent magnet 26 and yoke 28
38, a movable arm 40 coupled to the bobbin and coupled to a movable lens barrel to be driven, and a shaft 42 coupled to the movable arm 40 and supported by bearings 44 and 46 so as to coincide with the axis of the permanent magnet 26. The movable arm 40 and the movable core 54 of the differential transformer 24 are connected by a connecting rod 56.

A differential transformer is provided inside the yoke 80 of the linear motor 74.
When the 76 is installed, the linear motor 74 is connected to a radial cylindrical permanent magnet 78, a double cylindrical yoke 80 disposed inside and outside thereof, and between the permanent magnet 78 and the outer cylinder 84 of the yoke 80. A movable coil 88 coupled to a movable lens barrel to be coupled to the bobbin and driven,
A shaft 94 is connected to the movable arm 88 and supported by bearings 96 and 98 so as to coincide with the axis of the permanent magnet 78.The differential transformer 76 is housed inside the inner cylinder 90 of the yoke 80. The movable core 106 is connected to the shaft 94.

In addition, the linear motor with a differential transformer for video camera
The primary coil 120 and the movable core 1 are mounted outside the yoke of the linear motor that drives the movable barrel 112 housed inside the fixed barrel 110 of FIG.
A differential transformer 118 having secondary coils 122 and 124 differentially connected to the differential transformer 118 is provided. And the fixed barrel 110
The primary coil 120 and the secondary coils 122, 1 of the differential transformer 118
24, and the movable core 126 is fixed to the movable lens barrel 112.

Operation The primary coil 48 of the differential transformer 24 is configured as described above.
Is provided with a sine wave generator 62, and when a sine wave AC voltage is applied to the primary coil 48, the differentially connected secondary coils 50, 52
Then, a differential output voltage proportional to the amount of displacement of the movable core 54 is generated. Therefore, a rectifier 64 is provided on the side of the secondary coils 50 and 52,
The rectified output is supplied to a low-pass filter 70 and a differentiator 72. Then, a DC voltage corresponding to the input low frequency band is output from the low-pass filter 70, so that the lens position of the movable lens barrel connected to the movable core 54 can be detected. Further, since a voltage proportional to the differential value of the input is output from the differentiator 72, the speed of the same lens can be detected.

A differential transformer is provided near the outside of the yoke 28 of the linear motor 22.
The movable lens barrel that receives the driving force from the coil 38 of the linear motor 22 is a permanent magnet in the center of the linear motor 22
The movable arm 40 is connected to a movable arm 40 supported by a slidable shaft 42 that coincides with the axis of 26, and the movable core 54 of the differential transformer 24 is coupled to the movable arm 40 via a connecting rod 56. It becomes compact, and the amount of displacement of the lens of the movable lens barrel and the amount of displacement of the movable core 54 match.

The differential transformer 76 is installed inside the yoke 80 of the linear motor 74, and the movable lens barrel receiving the driving force from the coil 86 of the linear motor 74 can slide along the axis of the permanent magnet 78 at the center of the linear motor 74. Connected to a movable arm 88 supported by a shaft 94, and a differential transformer
Since the 76 movable cores 106 are directly connected, the whole becomes more compact, and the displacement amount of the lens of the movable barrel and the displacement amount of the movable core 106 further match.

When the differential transformer 118 is mounted on the autofocus type double lens barrel 108, the linear motor can be made compact irrespective of the differential transformer 118. Moreover, since the movable core 126 is directly fixed to the movable barrel 112 that holds the lens 116,
The displacement amount of the lens 116 and the displacement amount of the movable core 126 exactly match.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing the structure of a linear motor with a differential transformer for a video camera to which the present invention is applied. In FIG. 2, 22 is a linear motor, and 24 is a differential transformer. The linear motor 22 is provided with a cylindrical permanent magnet 26 at the center, and a cylindrical yoke 28 serving as a case is superposed on the outside of the permanent magnet 26 so that their axes are aligned. As shown in FIG. 3, the permanent magnet 26 is of an axial type with one end having an N pole and the other end having an S pole. Moreover, at the N extreme portion, a cylindrical magnetic pole piece 32 having the diameter of the central hole 30 enlarged outward.
Concatenate. The S extreme surface of the permanent magnet 26 is connected to the inner surface of the side plate 34 on one side of the yoke 28. However, a hole is provided at the center of the side plate 34 and communicates with the center hole 36 of the permanent magnet 26 and the center hole 30 of the pole piece 32.

A cylindrical coil is inserted between the permanent magnet 26 and the body of the yoke 28.
38 is stored movably. Further, a columnar movable arm 40 is provided outside the opening side of the yoke 28, and is connected to a bobbin around which the coil 38 is wound. The axis of the coil 38 also coincides with the axis of the permanent magnet 26. The shaft 42 is arranged so as to coincide with this axis and penetrate the holes 30, 36 and the like. The left end of the shaft 42 is connected to the movable arm 40, and a portion near the center thereof is slidably supported by a bearing 44 provided inside the central hole 36 of the permanent magnet 26,
A portion near the right end is slidably supported by a bearing 46 provided in a central hole of the side plate 34. The movable arm 40 is connected to a movable lens barrel (not shown) of an autofocus type double lens barrel.

The differential transformer 24 is arranged near the outside of the linear motor 22. This differential transformer 24 has three coils wound on a bobbin as shown in FIG. 4, a primary coil 48 is disposed at the center, and secondary coils 50 and 52 are arranged on both sides thereof, and a movable core 54 is provided in the bobbin. Store movably. Then, the phases of the secondary coils 50 and 52 are shifted by 180 ° to make a differential connection, and the movable core 54 is connected to the movable arm 40 of the linear motor 22 using the connecting rod 56. The differential transformer 24 is housed in a shield case 58. When the differential transformer 24 is installed near the outside of the yoke 28 of the linear motor 22 as described above, the whole becomes compact.

A lens position / speed detection circuit 60 is connected to the differential transformer 24 as shown in FIG. In the figure, reference numeral 62 denotes a sine wave generator for generating a sine wave AC voltage for exciting the primary coil 48 of the differential transformer 24. The sine wave generator 62 produces a sine wave AC voltage of 3 to 5 KHz. When the sine wave AC voltage enters the primary coil 48, the differentially connected secondary coil
A differential output voltage proportional to the amount of displacement of the movable core 54 is generated at 50 and 52. At this time, if a control signal is given to the coil 38 of the linear motor 22, the coil 38 moves by receiving a thrust according to Fleming's left-hand rule, and is coupled to the coil 38.
The movable arm 40 supported by 42 also moves. As the movable arm 40 moves, the lens barrel and movable core 54 connected to it move
Moves in the same way, and the lens held by the lens barrel and the movable core 54
Are the same. For this reason, if the movable core 40 is at the center, the output on the secondary coil side is 0, and if it moves to either one, a voltage value proportional to the displacement amount is output.

A rectifier 64 is connected to the side of the secondary coils 50 and 52 of the differential transformer 24. After the rectifier 64, a low-pass filter 70 and a differentiator 72 are connected in parallel via amplifiers 66 and 68, respectively. Then, the amplified rectified output enters the low-pass filter 70 and the differentiator 72. And low pass filter 70
A DC voltage corresponding to the low frequency band of the input is output. This DC voltage becomes a position detection signal of the lens connected to the movable core 54. Further, a voltage proportional to the differential value of the input is output from the differentiator 72. This voltage becomes a speed detection signal of the lens connected to the movable core 54. Therefore, the lens position detection signal and the lens speed detection signal are fed back to the coil 38 of the linear motor 22 as the above-described control signal, in accordance with the autofocus signal indicating the amount of deviation from the correct focal length, and input thereto. I do.

FIG. 5 is a sectional view showing the structure of a linear motor with a differential transformer for autofocus of a video camera to which the present invention is applied. In the figure, 74 is a linear motor, and 76 is a differential transformer. The linear motor 74 has a cylindrical permanent magnet 78 at the center, and a double cylindrical yoke 80 as a case is superposed and arranged inside and outside of the permanent magnet 78 so that their axes coincide with each other. As shown in FIG. 6, the permanent magnet 78 has an S pole on the inner side and an N pole on the outer side.
Make it polar and radial. One side of the yoke 80 is closed by a side plate 82 having a central hole.

A cylindrical coil 86 is movably housed between the permanent magnet 78 and the outer cylinder 84 of the yoke 80. Further, a columnar movable arm 88 is provided outside the opening side of the yoke 80, and is connected to a bobbin around which a coil 86 is wound. The axis of the coil 86 is also a permanent magnet 78
Axis. The shaft 94 is arranged so as to be aligned with this axis and pass through the central hole 92 of the inner cylinder 90 of the yoke 80 and the central hole of the side plate 82 thereof. A portion near the center left side of the shaft 94 is connected to the movable arm 88, and its left end is slidably supported by an external bearing 96, and the vicinity of its right end is slidably supported by a bearing 98 provided in a central hole of the side plate 82. The movable arm
88 is connected to a movable lens barrel (not shown) of an autofocus type double lens barrel.

The differential transformer 76 is inside the yoke 80 of the linear motor 74,
That is, it is stored in the central hole 92 of the cylinder 90. Also in this differential transformer 76, a primary coil 100 is arranged at the center on the bobbin, and secondary coils 102 and 104 differentially connected to both sides thereof are arranged, and a movable core 106 is movably housed in the bobbin. However, the movable core 106 is connected to the center of the shaft 94. When the differential transformer 76 is housed inside the yoke 80 of the linear motor 74,
The whole becomes even more compact. Moreover, since the movable core 106 is directly connected to the shaft 94 that coincides with the axis of the linear motor 74, the lens held by the lens barrel and the movable core 106
Are more consistent with each other.

The above-described lens position / speed detection circuit 60 is also connected to the differential transformer 76. Then, similarly, a lens position detection signal can be obtained from the low-pass filter 70, and a lens speed detection signal can be obtained from the differentiator 72.

FIG. 7 is a sectional view showing a state in which a differential transformer is mounted on a double lens barrel for autofocus of a video camera to which the present invention is applied. In the figure, 108 is a double lens barrel for auto focus, 110 is its fixed lens barrel, and 112 is the movable lens barrel. Reference numerals 114 and 116 denote lenses held in the lens barrels 110 and 112, respectively. This double lens barrel 108 has a differential transformer 1
The primary coil 1 is mounted on the outer peripheral surface of the fixed lens barrel 110.
20 and the secondary coils 122 and 124 are wound and fixed, and a movable lens barrel
A cylindrical movable core 126 is fitted and fixed to the outer peripheral surface of 112.
Then, the movable lens barrel 112 is connected to a movable arm connected to a bobbin of a linear motor (not shown).

When the differential transformer 118 is attached to the double lens barrel 108 in this way, the linear motor can be compactly constructed regardless of the differential transformer 118. Moreover, since the movable core 126 is fixed to the movable barrel 112 that holds the lens 116, the displacement of the lens 116 and the displacement of the movable core 126 exactly match.

The above-described lens position / speed detection circuit 60 is also connected to the differential transformer 118. Then, similarly, a position detection signal of the lens 116 is obtained from the low-pass filter 70, and the differentiator 72
The speed detection signal of the lens 116 can be obtained from.

According to the present invention described above, since the differential transformer can detect the lens position of the movable lens barrel and detect the speed thereof, the number of parts is reduced, and the performance of the product is improved, and the size and cost are reduced. Can be achieved.

In addition, a differential transformer is installed near the outside of the yoke of the linear motor, and the movable lens barrel is connected to a movable arm supported by a slidable shaft that passes through the center of the linear motor. When the movable core of the moving transformer is connected, the whole can be made compact. In addition, since the displacement of the lens of the movable barrel and the displacement of the movable core match, the detection accuracy of the lens is improved.

The differential transformer is housed in the yoke of the linear motor, and the movable lens barrel is connected to a movable arm supported by a slidable shaft that passes through the center of the linear motor, and the movable core of the differential transformer is directly connected to the shaft. When combined, the whole can be made more compact. In addition, since the displacement amount of the lens of the movable lens barrel and the displacement amount of the movable core are more easily matched, the detection accuracy of the lens is further improved.

In addition, when the differential transformer is mounted on the autofocus type double lens barrel, it is easy to configure the linear motor compactly irrespective of the differential transformer. In addition, since the movable core is directly fixed to the movable barrel that holds the lens, the displacement amount of the lens and the displacement amount of the movable core accurately match, and the detection accuracy of the lens is significantly improved.

[Brief description of the drawings]

FIG. 1 shows a position and speed detection circuit of a differential transformer type lens for auto focus of a video camera to which the present invention is applied. FIG. 2 is a sectional view showing the structure of the linear motor with a differential transformer, FIG. 3 is a perspective view showing the permanent magnet, and FIG. 4 is an enlarged sectional view showing the differential transformer. FIG. 5 is a sectional view showing the structure of a linear motor with a differential transformer for autofocus of a video camera to which the present invention is applied, and FIG. 6 is a perspective view showing the permanent magnet. FIG. 7 is a sectional view showing a state in which a differential transformer is mounted on a double lens barrel for autofocus of a video camera to which the present invention is applied. FIG. 8 is a state diagram showing an arrangement relationship of a copper plate in a conventional capacitive sensor for autofocus of a video camera. 22, 74 ... linear motor, 24, 76, 118 ... differential transformer, 26, 78 ... permanent magnet, 28, 80 ... yoke, 38, 86 ...
... Coil, 40, 88 ... Movable arm, 42, 94 ... Shaft, 44, 46, 96, 98 ... Bearing, 48, 100, 120 ... Primary coil, 50, 52, 102, 104 ... 2 Next coil, 54, 106, 126
... movable core, 56 ... connecting rod, 60 ... lens position and speed detection circuit, 62 ... sine wave generator, 64 ... rectifier, 70 ...
… Low-pass filter, 72… Differentiator, 108… Double barrel, 110… Fixed barrel, 112… Movable barrel, 116… Lens

Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location G03B 13/34 G02B 7/04 A H02K 33/18 E H04N 5/232

Claims (4)

(57) [Scope of request for utility model registration] 1. A differential transformer type position / speed detecting circuit in which a differential transformer having a primary coil and a secondary coil differentially connected to a movable core is installed in an autofocus type double lens barrel of a video camera. A sine wave generator for generating a sine wave AC voltage for exciting the primary coil of the differential transformer, a rectifier for rectifying a secondary coil differential output voltage of the differential transformer proportional to the displacement of the movable core, and A low-pass filter that inputs a rectified output and outputs a DC voltage corresponding to the low frequency band of the input as a lens position detection signal of a movable lens barrel connected to a movable core, and similarly inputs a rectified output and calculates a differential value of the input. And a differentiator that outputs a proportional voltage as a lens speed detection signal of the movable lens barrel. A differential transformer type position and speed detection circuit for auto-focusing of a video camera. 2. A differential transformer having a primary coil and a secondary coil differentially connected to a movable core near an outside of a yoke of a linear motor for driving a movable barrel of an autofocus type double barrel of a video camera. In the linear motor with a differential transformer, the linear motor is housed so as to be movable between an axial cylindrical permanent magnet, a cylindrical yoke arranged to be superposed on the outside thereof, and the permanent magnet and the yoke. A cylindrical coil, a movable arm coupled to the bobbin and coupled to a movable lens barrel to be driven, and a shaft coupled to the movable arm and supported by bearings so as to match the axis of the permanent magnet, A linear motor with a differential transformer for autofocus of a video camera, wherein the movable arm and the movable core of the differential transformer are connected by a connecting rod. 3. A linear motor yoke for driving a movable barrel of an autofocus type double barrel of a video camera.
In a linear motor with a differential transformer containing a differential transformer having a secondary coil and a secondary coil differentially connected to a movable core, the linear motor has a radial cylindrical permanent magnet and a double A cylindrical yoke, a cylindrical coil movably housed between the permanent magnets thereof and the outer cylinder of the yoke, a movable arm coupled to the bobbin, and coupled to a movable lens barrel to be driven, and coupled to the movable arm And
A video camera comprising: a shaft supported by bearings so as to coincide with the axis of a permanent magnet; a differential transformer housed in an inner cylinder of the yoke; and a movable core coupled to the shaft. Linear motor with differential transformer for auto focus. 4. A secondary coil having a primary coil and a movable core differentially connected outside a yoke of a linear motor for driving a movable lens barrel housed in a fixed lens barrel of an autofocus type double lens barrel of a video camera. In a linear motor with a differential transformer having a differential transformer having the following features, the primary coil and the secondary coil of the differential transformer are fixed to the fixed lens barrel, and the movable core is fixed to the movable lens barrel. Linear motor with differential transformer for autofocus of video cameras.