JPH0820581B2 - Focus adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a focus adjusting device, and more specifically, in an optical device such as a camera, a focus adjusting operation of a focus lens which is a rear lens group in accordance with a zooming operation. The present invention relates to a focus adjustment device for automatically performing.

[Conventional technology]

As a focus adjusting means of a still camera, a video camera, or the like, there are a method of driving a front group lens and a method of driving a rear group lens. In the latter, the rear lens group is smaller and lighter than the front lens group, so less power is consumed to move the lens.Because the rear lens group has less movement than the front lens group, focusing is achieved in a short time. There are many excellent advantages such as the fact that a helicoid for driving the front lens group is not required and the lens operating cost is low. Although the latter has many advantages as described above, the former drive method is adopted in a camera having a zoom lens (Japanese Utility Model Application Publication No. 54-14496,
(See Japanese Patent Publication No. 51-17045).

[Problems to be solved by the invention]

The reason is that in the method of driving the rear lens group,
This is because the focus position changes as the zoom lens moves during manual focusing. That is, in auto focus, there is no problem as long as the zoom lens moves at a speed that the rear lens group can follow, but in the case of manual focus, if the zoom lens is moved while the rear lens group is stationary, the focus position will change. Will be shifted.

Therefore, in order to solve this, the cams that determine the movement amount of the zoom lens and the rear group lens are correlated, and the rear group lens moves following the movement of the zoom lens. However, it is difficult to actually provide such a cam mechanism in the lens barrel because the configuration becomes very complicated. Even if the cam mechanism as described above can be provided, sufficient working accuracy cannot be obtained, and high focusing accuracy cannot be obtained over the entire zooming area. Therefore, if the rear lens group can be moved in correspondence with zooming even during manual focusing without providing such a complicated cam mechanism, even in a camera having a zoom lens, the advantages described above can be obtained. Many rear group drive systems can be realized.

The present invention has been made in view of the above-described circumstances, and has a simple configuration without using a complicated mechanism or the like, and automatically sets a focusing lens including a rear group lens to a focusing corresponding position according to a set distance. It is an object of the present invention to provide a focus adjustment device that can maintain a focused state by moving it regardless of a zooming operation.

Another object of the present invention is to enable switching between these operation modes without specially providing a means for switching between the manual focus mode and the auto focus mode, and in the auto focus mode in which the display of the set distance becomes meaningless. It is an object of the present invention to provide a focus adjusting device of this kind in which an operator does not feel a sense of incongruity or feel uncomfortable by making no display.

[Means for solving problems]

The focus adjusting device of the present invention includes a lens system including at least a zoom lens and a rear group lens movably provided for focus adjustment, and the lens system is displaced based on a distance setting operation arbitrarily performed by an operator. And an operation display member for displaying a set distance related to the lens system within a predetermined section of the range in which the displacement is allowed, and a setting corresponding to the set distance when the operation display member is displaced within the predetermined section. Setting signal generating means for generating a distance signal and generating an autofocus mode setting signal when the operation display member reaches a predetermined position outside the predetermined section, and a zoom sensor for detecting the current position of the zoom lens, An autofocus processing circuit that outputs a signal for performing an autofocus operation based on a signal obtained from a sensor or the like, For various set distances, when the data of the positional relationship between the zoom lens and the rear lens group in the focused state at the distances is internally set, and the set distance signal is given from the set signal generating means, Tracing the rear lens group position in the in-focus state corresponding to the zoom lens position detected by the zoom sensor and the set distance by the set distance signal of the set signal generation means based on the data set inside, A manual control signal for moving the rear lens group to that position is output, and when the autofocus mode setting signal is given from the setting signal generating means, based on the output signal of the autofocus processing circuit. A control that outputs an autofocus signal to displace the rear lens group position And a driving means for driving the rear group lens in response to the manual control signal or the autofocus signal of the control circuit.

[Work]

In the device of the present invention having the above-described configuration, for example, when the in-focus state is obtained for the set distance formed by the operation of the operation display member (operation ring) having a shape similar to that of the distance ring, etc. When the zoom lens is operated, the signal corresponding to the zoom lens position detected by the zoom sensor and the signal representing the set distance by the set distance signal generating means are input to the control circuit.

The control circuit is configured to set the zoom lens position and the setting based on the data regarding the positional relationship between the zoom lens and the rear group lens in the in-focus state at various distances set in the circuit. The rear lens group position in the in-focus state corresponding to the distance and the distance is traced, and the manual control signal is output according to the result to operate the driving means, and the rear lens group is automatically moved regardless of the zooming operation. It is driven to the focusing position.
Therefore, even if the zoom lens is moved, the focused state according to the set distance at that time is maintained.

Further, when the operation display member is rotated to a predetermined position outside the predetermined section (for example, a position beyond the display ∞ of infinity), the apparatus is switched to the auto focus mode operation.
The control circuit outputs an autofocus signal based on the signal given from the autofocus processing circuit to the control circuit, and the driving means, that is, the rear lens group is driven in response to the signal, and the autofocusing operation is performed.

〔Example〕

 Hereinafter, the present invention will be described based on the illustrated embodiments.

FIG. 1 is a block diagram of a focus adjusting device showing an embodiment of the present invention. The focus adjusting device shown in FIG. 1 is applied to a video camera, and the image pickup lens barrel 1 of the camera has a front lens group 2, a zoom lens 3, a diaphragm 4, a rear lens group 5, and the like. While the front lens group 2 is fixed to the fixed portion of the lens barrel 1, the rear lens group 5 is movable in the optical axis direction for focus adjustment.
That is, in the rear lens group 5, as shown in FIG. 2, the pin 7a provided integrally with the lens holding frame 7 has the stepping motor 8
Since it is engaged with the feed screw 9 connected to the output shaft 8a of
When the stepping motor 8 is driven, the lens holding frame 7 moves the guide member 10 provided along the optical axis direction in the arrow A or arrow B direction by the pitch of the feed screw 9. The stepping motor 8 is driven by a control signal from the control circuit 11. Further, when the rear lens group 5 reaches the infinity position, as shown in FIG. 2, the light shielding portion 7b provided integrally with the lens holding frame 7 is moved by the zero point sensor 12 formed of a photo interrupter to the rear lens group 5. The reference position (zero point) of is detected. The output of the zero point sensor 12 is input to the control circuit 11.

As shown in FIG. 3, on the outer periphery of the lens barrel 1, an operation ring 6 as an operation display member is engraved with a distance scale within a predetermined section of the range in which the rotational displacement is allowed, and serves as a fixed frame. It is rotatably provided with an appropriate frictional force between. This operation ring 6 is not mechanically connected to any optical element or the like in the lens barrel 1, and due to its own rotation,
The distance scale supported by the index 1a is the distance scale sensor 13
It is electrically read by and the read electrical signal is input to the control circuit 11.
The electric signal in the above is a set distance signal corresponding to the distance set on the basis of the distance scale.

The distance scale sensor 13 is constructed, for example, as shown in FIG. That is, in FIG. 4, a conductive contact 14 is fixedly provided inside the operation ring 6, and the conductive contact 14 is a thin film formed along the rotation direction on the outer periphery of the fixed frame of the lens barrel 1. The conductor 15 and the thin-film resistor 16 formed in the same manner in parallel with the conductor 15 are in sliding contact with each other. Conductor 15
Is grounded, and the resistor 16 is connected to the input terminal of the control circuit 11. And this operation ring 6 is "auto" which exceeds the "closest" scale position or the "infinite" scale position.
It is possible to rotate to a position (not shown), and when the resistance value changes according to the rotating position of the operation ring 6,
Depending on this change in resistance value, the A / D of control circuit 11
The electric signal input to the converter 17 changes. The A / D converter 17 converts the electrical signal from the distance scale sensor 13 into an A / D signal.
The converted digital signal corresponding to the distance scale is sent to the microcomputer 18. When the operating ring 6 is set to the "auto" rotating position beyond the section where the distance scale is provided, the conductive contact 14 does not contact the resistor 16 but only the conductor 15, so The area between 15 and the resistor 16 is opened. The output signal of the distance scale sensor 13 at this time is an autofocus mode setting signal for setting the operation mode of this apparatus to the autofocus mode. Upon receiving the auto focus mode setting signal, the control circuit 11 switches the control of the stepping motor 8 that drives the rear lens group 5 from manual focus by the operation ring 6 to auto focus.

In summary of the distance scale sensor 13, when the operation ring 6 as the operation display member is rotationally displaced in the section provided with the scale, a distance signal corresponding to the set distance represented by the scale is generated. At the same time, it constitutes a setting signal generating means for issuing an autofocus mode setting signal when the operation ring 6 rotates to reach a position outside the section (for example, a position beyond "infinity").

When operating the zoom switch 32, the zoom lens 3
A motor 20 driven by a control signal from the lens control unit 19 can move in the optical axis direction,
The focal length is read by 21 and the read electrical signal is input to the lens control section 19. The zoom sensor 21 is a position sensor including, for example, a potentiometer and a photo sensor.

The diaphragm 4 may be operated manually or automatically, but the diaphragm value is read by the diaphragm sensor 22 and the read electrical signal is input to the lens control section 19. ing.

The subject light transmitted through the optical system of the lens barrel 1 is imaged on the image pickup surface of the image pickup device 23 and photoelectrically converted by the image pickup device 23 into a video signal, which is processed by the camera circuit 24. Are taken out as a video signal. The luminance signal of the video signal is input from the camera circuit 24 to the auto focus processing circuit 25. This autofocus processing circuit
Reference numeral 25 denotes signal processing such as differentiation from the luminance signal to extract a harmonic component, and compares the phase of the output of the harmonic component and the phase of the vibration of the rear lens group 5 at the time of autofocus, A circuit known per se (for example, Japanese Patent Laid-Open No. 56-116007) which sends a signal for autofocusing to the control circuit 11 by judging either the rear focus or the in-focus state.
Is. Further, the control circuit 11 is supplied with a clock signal of, for example, an integral multiple of 15 Hz from the reference frequency generation circuit 26. This clock signal is the control circuit 11
The control circuit 11 sends a necessary pulse to the stepping motor 8 based on the frequency of 15 Hz, and the stepping motor 8 drives the autofocusing or the manual focusing by the pulse. As described above, in this example, the image pickup device 23 itself also serves as a focus state detection sensor (distance measuring sensor) for obtaining a signal for autofocusing. However, as the distance measuring sensor, various known sensors such as a so-called active type sensor having a light emitting element and a light receiving element can be applied in addition to the so-called passive type sensor of the above embodiment.

As shown in FIG. 5, the control circuit 11 has a storage unit 30, a calculation unit 28, and a step number calculation unit 29 in the microcomputer 18. The storage unit 30 stores a characteristic curve representing the proper position of the rear lens group 5 determined by the focal length and the shooting distance (ROM) (read only memory).
Is. The calculation unit 28 includes an output of the distance scale sensor 13 input from the A / D converter 17, an output of the zoom sensor 21 input from the lens control unit 19, and an aperture sensor 22.
Is read and the proper position of the rear lens group 5 is calculated from the characteristic curve stored in the storage unit 30.
Further, at the time of autofocus, the output of the autofocus processing circuit 25 is guided and calculated. The output of the arithmetic unit 28 is guided to the motor drive circuit 30 and the number of steps calculator 29 calculates the output of the rear group lens 5.
The number of steps is always counted where the position of is. Further, a distance display device 27 for displaying a distance during autofocus is connected to the calculation unit 28.

The characteristic curve stored in the storage unit 30 in the microcomputer 18 is, for example, as shown in FIG. In FIG. 6, the horizontal axis represents the rear lens group 5
Of the moving amount with respect to the image pickup surface of the image pickup device 23, and the vertical axis shows the moving amount of the zoom lens 3. As is apparent from FIG. 6, when the zoom lens 3 is at the "T (telephoto)" position, the rear lens group 5 is "infinity", "1 m", "0.
The focal points at the distance of 5 m are a ₁ , a ₂ , a _{3 respectively.}
Is. Further, when the zoom lens 3 is at the “S (standard)” position, the rear lens group 5 is focused on the above distance positions at the positions b ₁ , b ₂ and b ₃ , respectively. When the rear lens group 5 is in the "W (wide angle)" position, the rear lens group 5 is focused on the respective distance positions at the positions c ₁ , c ₂ and c ₃ , respectively. That is, when the rear lens group 5 is focused on “infinity”, a change in the focal length due to the movement of the zoom lens 3 from “W” to “T” is substantially “く”. As shown by the characteristic curve l ₁ in the shape of “
It is necessary to change the feeding amount of. Also, the rear lens group 5
In order to focus on “1 m” and “0.5 m” respectively, in response to the change in the focal length due to the movement of the entire area of the zoom lens 3, a characteristic curve l _{2 having} a substantially V shape is formed. It is necessary to change the amount of extension of the rear lens group 5 as indicated by l ₃ . The characteristic curves l ₁ , l ₂ and l ₃ all have different shapes. At the distance positions between these three distance positions other than "infinity", "1 m", and "0.5 m", the extension amount of the rear lens group 5 is the above characteristic curve.
It goes without saying that, between l ₁ , l ₂ and l ₃ , the characteristic curve has a shape different from these, which is not shown.

Although it is difficult for the cam mechanism to extend the rear group lens 5 that differs depending on the focal length and the photographing distance, as represented by the characteristic curves l ₁ , l ₂ , and l ₃ , the characteristic curves In the area between l ₁ , l ₂ , and l ₃ and between these curves, characteristic curves (not shown) corresponding to the focal length and the photographing distance are stored in the storage unit 30, so that the amount of feed-out by the stepping motor 8 can be reduced. Complex control becomes possible. The rear lens group 5 is not controlled except in the region between the "infinite" characteristic curve l ₁ and the "closest" characteristic curve l ₃ .

Next, the operation of the focus adjusting device configured as described above will be described.

In the case of manual focus, when the operating ring 6 is rotated and the index 1a is adjusted to the desired distance scale, an electric signal corresponding to the set distance scale, that is, a set distance signal, is sent from the distance scale sensor 13 to the control circuit 11. Is entered. At this time, the focal length is set by operating the zoom switch 32, and the motor 20 is driven by a control signal (that is, a manual control signal) from the lens control unit 19 to set the zoom lens 3 to a desired one. It is controlled by the focal length position. Then, the position of the zoom lens 3, that is, the focal length information is detected by the zoom sensor 21 and read by the lens control unit 19. The information on the aperture 4 is also converted into an electric signal by the aperture sensor 22 and read by the lens control unit 19.

The electrical signal from the distance scale sensor 13 is A / D converter 17
Is input to the arithmetic unit 28 of the microcomputer 18 of the control circuit 11 as the photographing distance information set by the A / D conversion at that time, and the focal length information and the aperture information from the lens control unit 19 to the arithmetic unit 28. When is input, the arithmetic unit 28 reads each of these pieces of information and refers them to the respective characteristic curves which are the contents of the storage unit 30. Then, when the proper extension position of the rear lens group 5 is traced from the characteristic curve suitable for the input information, the arithmetic unit 28 sends a signal corresponding to this to the motor drive circuit 31 to rotate the stepping motor 8 to the proper position. . As a result, when a zooming operation is performed at a certain shooting distance, the rear lens group 5 responds to this operation and moves to follow the focus state so as to always maintain the in-focus state. Therefore, even after the zooming operation is performed, the in-focus state is automatically established.

When the focus adjusting device is set to the auto focus state, as shown in FIGS. 3 and 4, the operation ring 6 is rotated in the direction of the arrow C, and the "auto" (shown in the figure) exceeding the "infinite" position is displayed. Set it to the position. Then, as described above, the distance scale sensor 13 outputs the autofocus mode setting signal, and the signal is input to the control circuit 11.
At this time, the control circuit 11 is switched to perform a control operation for autofocusing, and the stepping motor 8 causes the rear lens group 5 to move to the arrows A and B by a pulse from the control circuit 11 having a frequency of 15 Hz as a reference. Alternately vibrate along the optical axis (see FIG. 2). Since the rear lens group 5 vibrates in the optical axis direction, the optical path length slightly changes, so that the level of the high-frequency component included in the luminance signal input to the autofocus processing circuit 25 slightly changes. The fluctuation waveform (modulation signal) of this high-frequency component is minimized in the focus state, and the phase of the modulation signal at the front and rear pins is 18
Since it is inverted by 0 °, when the focus signal is input from the autofocus processing circuit 25 to the arithmetic unit 28 of the control circuit 11, the arithmetic unit 28 causes the motor drive circuit 31 to center the stepping motor 8 on the focal point. Gives a signal for vibrating back and forth with the same amplitude. Since this amplitude is performed in consideration of the aperture information, that is, the depth of field, the rear group lens 5 is in a state where it is not different from the fact that it is actually stationary at the focal point. In this in-focus state, a display signal is sent from the arithmetic unit 28 to the distance display device 27, and the in-focus distance is displayed by a light emitting diode or liquid crystal.

The signal from the autofocus processing circuit 25 that is out of focus and the signal from the front pin or the rear pin is output from the arithmetic unit of the control circuit 11.
When being guided to 28, the arithmetic unit 28 gives a signal to the motor drive circuit 31 to cause the stepping motor 8 to vibrate while advancing toward the focal point. That is, the rear group lens 5 moves toward the in-focus point by giving a signal to the stepping motor 8 which has a large amplitude toward the in-focus point and a small vibration in the opposite direction. The speed at which the boom lens 3 is moved by the motor 20 during autofocus is slower than the speed at which the rear lens group 5 moves toward the in-focus point so that the autofocus operation can follow.

As described above, in the apparatus of the present invention, these operation modes can be switched by operating only the operation ring 6 for distance setting, without separately providing a means for switching between the manual focus mode and the auto focus mode. In the autofocus mode where the display of the set distance is meaningless, the operating ring 6 is fully rotated to a position where there is no distance display, so that the operator may recognize an error or feel uncomfortable. There is no such problem.

The distance scale sensor 13 in the above embodiment converts the distance scale into an electric signal by utilizing the change of the resistance value. In addition to this, for example, the distance scale sensor 3 shown in FIG.
Alternatively, the distance scale sensor 43 shown in FIG. 8 or the like may be used. As shown in FIG. 7, the distance graduation sensor 33 has a 3-bit photo sensor 34 integrally attached to the operation ring 6 and the outer periphery of the fixed frame of the lens barrel 1 along the rotation direction for each bit. Partially attached reflector
35, 36, 37, and the lead wire of the photosensor 34 is the microcomputer 18 of the control circuit 11.
It is connected to the. Therefore, in the distance scale sensor 33, the photo sensor 34 is placed at a position corresponding to the rotation amount of the operation ring 6.
Reads the presence / absence of the reflectors 35, 36, 37 according to the presence / absence of reflected light, converts this into an electric signal, and the microcomputer 18
The distance scale is read into the microcomputer 18 as a digital signal.

Further, as shown in FIG. 8, the distance graduation sensor 43 as the setting signal generating means has a 3-bit conductive contact 44 integrally attached to the operating ring 6 and an outer circumference of the fixed frame of the lens barrel 1. It is composed of thin film conductors 45 to 48 formed for each bit / along the rotation direction, of which the conductor 45 is grounded and the other conductors 46 to 48 are resistors 51 to 53.
The voltage Vcc is applied by and is connected to the input terminal of the microcomputer 18. Therefore, in the distance scale sensor 43, the conductive contacts 44 short-circuit or open between the conductors 46 to 48 and the conductor 45 in accordance with the rotational position of the operation ring 6, and thus the conductors 46 to 48. Are low level “L” (ground) or high level “H” (voltage Vc
In step c), the distance scale is input to the microcomputer 18 as a 3-pit digital signal. In addition,
The distance scale sensors 33 and 43 shown in FIGS. 7 and 8 have a 3-bit configuration, but actually, in the telephoto (T) state, 0.5 m
It is desirable to have a structure of about 7 bits so that the distance of ∞ (see FIG. 6) can be divided into about 80 to 100. In this case, it goes without saying that the above-mentioned autofocus mode setting signal also takes the form of a predetermined digital signal. Still further, in the present invention, the operation display member and the setting signal generating means are replaced with the above-described distance ring-shaped operation ring and a distance scale sensor corresponding thereto, instead of a direct-acting potentiometer,
Alternatively, it may be constituted by means of a potentiometer driven by a motor or an encoder mode.

〔The invention's effect〕

As described above, according to the present invention, it is possible to maintain the in-focus state according to the set distance regardless of the zooming operation with a simple electric circuit configuration without using a cam mechanism or the like.

Furthermore, according to the present invention, these operation modes can be switched without specially providing a means for switching between the manual focus mode and the auto focus mode, and the display of the set distance becomes meaningless in the auto focus mode. Since the display is no longer visible, the operator does not recognize mistakes or feel uncomfortable.

[Brief description of drawings]

FIG. 1 is a block diagram of an electric circuit of a focus adjusting device showing one embodiment of the present invention, FIG. 2 is a cross-sectional view showing a driving portion of a rear group lens in FIG. 1, and FIG. FIG. 4 is a perspective view showing an appearance of the operation ring in FIG. 1, FIG. 4 is a schematic configuration diagram showing an example of a distance scale sensor in FIG. 1, and FIG. 5 is a control circuit in FIG. FIG. 6 is a characteristic curve diagram for lens control stored in the storage unit in FIG. 5, and FIGS. 7 and 8 are other examples of the distance scale sensor. FIG. 3 ... Zoom lens 5 ... Rear group lens (focus lens) 6 ... Operation ring (operation display member) 8 ... Stepping motor (driving means) 11 ... Control circuit 13 ... Distance scale sensor (setting signal generating means) ) 21 …… Zoom sensor 25 …… Autofocus processing circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03B 13/34

Claims (1)

[Claims] 1. A lens system including at least a zoom lens and a rear group lens movably provided for focus adjustment, and the displacement is performed based on a distance setting operation arbitrarily performed by an operator. An operation display member for displaying a predetermined distance related to the lens system within a predetermined section of the allowable range, and a set distance signal corresponding to the set distance when the operation display member is displaced within the predetermined section. A setting signal generating unit that generates an autofocus mode setting signal when the operation display member reaches a predetermined position within the predetermined section, a zoom sensor that detects the current position of the zoom lens, and a sensor or the like. Autofocus processing circuit that outputs a signal for performing autofocus operation based on the obtained signal, and various settings Regarding the separation, when the data of the positional relationship between the zoom lens and the rear lens group in the in-focus state at that distance is internally set and the set distance signal is given from the set signal generating means, the zoom sensor The position of the rear lens group in the in-focus state corresponding to the zoom lens position detected by and the set distance by the set distance signal of the set signal generating means is traced based on the data set inside, and the position is set to that position. When a manual control signal for moving the rear lens group is output and the autofocus mode setting signal is given from the setting signal generating means, the rear group is output based on the output signal of the autofocus processing circuit. A control circuit that outputs an autofocus signal to displace the lens position, and Focusing device, characterized in that in response to the manual control signal or the autofocus signal control circuit equipped with a driving means for driving the lens groups after the above.