JPS62180338A - Focus adjusting device - Google Patents

Abstract

PURPOSE:To move a focusing lens to a position corresponding to the operation of an operating member for distance setting through a simple constitution by providing an operating member, a distance setting signal generating means, a focus setting signal generating means, a focus adjustment signal generating means, and a lens driving means. CONSTITUTION:An operating ring 6 is rotated to align an index 1a to a desired distance graduation in manual focusing mode, and then an electric signal corresponding to the set distance graduation is inputted from a distance scale sensor 13 to a control circuit 11. At this time, the focal length is set through the operation of a zoom switch 32 and a motor 20 is driven with a control signal from a lens control part 19 to control a zoom lens 3 to the position of the desired focal length. Then, the position of this zoom lens 3, i.e., focal length information is read by the lens control part 19. Information on a stop 4 is also converted by a stop sensor 22 into an electric signal, which is read by the lens control part 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a focus adjustment device, more specifically, in an optical device such as a camera, the focus of a focus lens is adjusted according to the operation of an operation member for setting a distance. The present invention relates to a focus adjustment device that performs adjustment operations.

[Prior Art] As a focus adjustment means for still cameras, video cameras, etc.
There are two methods: one for driving the front group lens and the other for driving the rear group lens. The latter has two advantages: ■ The rear group lens is smaller and lighter than the front group lens, so it requires less power to move the lens number, and ■ The rear group lens moves less than the front group lens, so it can be moved in a shorter time. can be focused,
■There are many excellent advantages, such as the fact that the helicoid for driving the front group lens is not required, so the manufacturing cost of the lens is low. Although the latter has many advantages, the former drive method is still used in cameras with zoom lenses (Utility Model Publication No. 54-14496, Japanese Patent Publication No. 51-17045). (see official bulletin).

[Problems to be Solved by the Invention] The reason for this is that in the method of driving the rear J:' lens, the focal position changes as the zoom lens moves during manual focusing. In other words, during autofocus, there is no problem if the zoom lens moves at a speed that the rear group lens can follow, but in the case of manual focus, if the zoom lens is moved while the rear group lens remains stationary, the focus position will change. This will result in misalignment.

Therefore, in order to solve this problem, we created a correlation between the respective cams that determine the movement of the zoom lens and the rear group lens, so that when the zoom lens moves, the rear group lens moves accordingly. However, it is difficult to actually provide such a cam mechanism in the lens barrel because the configuration becomes extremely complicated. Further, even if the cam mechanism as described above could be provided, sufficient machining accuracy could not be achieved, and high focusing accuracy could not be obtained over the entire zooming range. Therefore, if it were possible to move the rear lens group in response to zooming even during manual focus without providing such a complicated cam mechanism, cameras with any zoom lens would have the advantages mentioned above. This means that many rear group drive systems can be realized.

Furthermore, even if the front group lens is driven, if it is possible to perform macro photography (see the above-mentioned publications, ie, Japanese Utility Model Publication No. 54-14496 and Japanese Patent Publication No. 51-17045), the The lens group is moved largely from the normal photographing area to the macro area, and the cam mechanism for this purpose is also complex. Therefore, even with the method of driving the front 7tT lens, if the front group lens can be moved without providing a cam mechanism for distance adjustment, the above-mentioned structural and accuracy problems can be solved.

The present invention was made in view of the above-mentioned circumstances, and
It is an object of the present invention to provide a focus adjustment device that can adjust the focus by moving a focusing lens to a position according to the operation of a distance setting operation member with a simple configuration without using a complicated mechanism. do.

[Means and effects for solving the problem] The focus adjustment device of the present invention, when a distance setting signal is generated from the distance setting signal generation means by operating the distance setting operation member, adjusts the distance setting signal according to the distance setting signal. A focus adjustment signal is generated from the focus adjustment signal generating means, and based on this focus adjustment signal, the focus lens is driven by the lens driving means to a focal position according to the distance setting.

[Example] Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a block diagram of a focus adjustment device showing one embodiment of the present invention. The focus adjustment device shown in FIG. 1 is applied to a video camera, in which an imaging lens m barrel 1 has a front group lens 2. Zoom lens 3. It has a built-in aperture 4, a rear group lens 5, etc., and while the front group lens 2 is fixed to a fixed part of the lens barrel 1, the rear group lens 5 moves in the optical axis direction for focus adjustment. It is now possible to do so.

That is, as shown in FIG. 2, in the rear group lens 5, the pin 7a provided integrally with the lens holding frame 7 engages with the feed screw 9 connected to the output shaft 8a of the stepping motor 8. When the stepping motor 8 is driven, the feed screw 9
According to the pitch, the lens holding frame 7 moves the guide member 10 provided along the optical axis direction in the direction of arrow A or arrow B. The stepping motor 8 is driven by a control signal from a control circuit 11. Furthermore, when the rear group lens 5 reaches the infinity position, as shown in FIG.
A light shielding portion 7b provided integrally with the lens holding frame 7 allows a reference position (zero point) of the rear group lens 5 to be detected by a zero point sensor 12 made of a photo ink club. The output of this zero point sensor 12 is the control circuit 11
This will be done manually.

As shown in FIG. 3, on the outer periphery of the lens barrel 1, an operating ring 6 having a distance scale engraved thereon is rotatably provided with an appropriate frictional force between it and the fixed frame.

This operation ring 6 is not mechanically connected to any optical element in the lens barrel 1, and by its own rotation, the distance scale supported by the index 1a is electrically connected to the distance sensor 13. The electric signal thus read is input to the control circuit 11.

The distance scale sensor 13 is configured as shown in FIG. 4, for example. That is, in FIG. 4, a conductive contact 14 is fixedly installed inside the operating ring 6.
is in sliding contact with a thin film-like conductor 15 formed along the rotational direction on the outer periphery of the fixed frame of the lens barrel 1, and a thin film-like resistor 16 similarly formed substantially parallel to this conductor 15. ing. The conductor 15 is grounded, and the resistor 16 is connected to the input terminal of the control circuit 11. The operating ring 6 can be rotated from the "close" scale position to the "auto" position (not shown), which exceeds the "infinite" scale position. When the resistance value changes accordingly, the electrical signal input to the A/D converter 17 of the control circuit 11 changes in accordance with this change in resistance value.

The A/D converter 17 A/D converts the electric signal from the distance scale sensor 13 and sends a digital signal corresponding to the distance scale to the microcomputer 18. When the operating ring 6° is set to the "auto" rotation position, the conductive contact 14 does not contact the resistor 16 but only the conductor 15, so that the conductor 15 and the resistor 16 are in an open state. Then,
At this time, the manual input information to the control circuit 11 becomes "auto". That is, the control circuit 11 is "auto"
When it reads, the control circuit 11 controls the rear lens group 5.
The control of the stepping motor 8 that drives the is switched from manual focus using the operation ring 6 to autofocus.

When the zoom lens 3 operates the zoom switch 32,
It can be moved in the optical axis direction by a motor 20 driven by a control signal from the lens control section 19, the focal length is read by a zoom sensor 21, and this read electric signal is input to the lens control section 19. ing. The zoom sensor 21 is a position sensor configured by, for example, a potentiometer, a photo sensor, or the like.

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

The subject light that passes through the optical system of the lens barrel 1 is imaged on the imaging surface of the image sensor 23, and is photoelectrically converted into a video signal by the image sensor 23. This video signal is sent to the camera circuit 2.
4 and extracted as a video signal. A brightness signal of the video signal is input from the camera circuit 24 to the autofocus processing circuit 25. The autofocus processing circuit 25 performs signal processing such as differentiation on the luminance signal to extract harmonic components, and compares the output phase of the harmonic components with the phase of the vibration of the rear group lens 5 during autofocus. Then, a focus state signal is sent to the control circuit 11 by determining whether the camera is in front focus, back focus, or in focus.

The control circuit 11 also includes a reference frequency generation circuit 2.
6, for example, a clock signal of an integral multiple of 15 tlz is manually generated.

Since this clock signal is input to the control circuit 11, a necessary pulse is sent from the control circuit 11 to the stepping motor 8 based on the frequency of 1511Z, and the stepping motor 8 is driven for autofocus or manual focus by this pulse. Let's do it.

As shown in FIG. 5, the control circuit 11 includes a storage section 30.0 for manual focus in the microcomputer 18. It has a calculation section 28 and a step number calculation section 29. The storage unit 30 is a ROM (read only memory) that stores a characteristic curve representing the appropriate position of the rear group lens 5 determined by the focal length and photographing distance.

The calculation unit 28 receives the output of the distance scale sensor 13 inputted from the A/D converter 17 and the lens control unit 19.
The output of the zoom sensor 21 and the output of the diaphragm sensor 22 are read in, and the appropriate position of the rear group lens 5 is calculated from the characteristic curve stored in the storage section 27. Further, during autofocus, the output of the autofocus processing circuit 25 is guided and calculated. The output of this calculation section 28 is the motor drive circuit 3
0, and the step number calculation unit 29 always counts the number of steps to determine where the rear group lens 5 is located. In addition, the calculation unit 28
A distance display device 27 is connected to the vehicle for displaying distance during autofocus and -cast mode.

The characteristic curve stored in the storage section 27 in the microcomputer 18 is, for example, as shown in FIG. In FIG. 6, the horizontal axis shows the outlet of the rear group lens 5 with reference to the imaging surface of the image sensor 23, and the vertical axis shows the amount of movement of the zoom lens 3. As is clear from FIG. 6, the zoom lens 3 is rT (telephoto).
”, the rear lens group 5 is at “infinity J, r1m
J.

The positions at and a2+ aa are focused at a distance of rO and 5 mJ, respectively. Also, zoom lens 3
is at the position b1. b
2. b3, and when the zoom lens 3 is in the "W (wide angle)" position, the rear group lens 5 focuses on each of the above distance positions at the positions c1. c2. It is c3. That is, when trying to keep the rear group lens 5 in a focused state at "infinity", the change in focal length caused by the movement of the zoom lens 3 from rWJ to rTJ will result in an approximately "<" shape. It is necessary to change the amount of extension of the rear group lens 5 as shown by the characteristic curve g1. In addition, the rear lens group 5 is
, rO, and 5 mJ, the characteristic curve II2., which is approximately in the shape of the character "<", is created in response to changes in focal length due to movement of the entire area of the zoom lens 3. As shown by I3, it is necessary to change the amount of extension of the rear group lens 5.

This characteristic curve g1. fI2. The shapes of R3 are all different.

These three distance positions “infinite J, rlmJ, rO,5
Regarding distance positions other than mJ, the rear group lens 5
The feeding amount is shown in characteristic curve 11 above. N2. It goes without saying that between ff3, the characteristics follow a characteristic curve (not shown) having a shape different from these.

Above characteristic curve 1. , N12. A rear group lens 5 that varies depending on the focal length and shooting distance, as represented by II3.
Although it is difficult to use a cam mechanism to advance the lens, in the above characteristic curves fl, , 112°g3 and the area between these curves, each characteristic curve (not shown) corresponding to the focal length and shooting distance is as described above. By storing it in the storage unit 30, the stepping motor 8 can perform complicated control of the feeding amount. The above “infinite” characteristic curve f11
The rear lens group 5 is not controlled in areas other than the region between the "close" characteristic curve fI3 and the "close" characteristic curve fI3.

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

In the case of manual focus, when the operating ring 6 is rotated to align the index 1a with a desired distance scale, an electric signal corresponding to the set distance scale is manually inputted from the distance scale sensor 13 to the control circuit 11. At this time, the focal length is set by operating the zoom switch 32, and the motor 20 is driven by a control signal from the lens control section 19 to control the zoom lens 3 to the desired focal length position. be done. Then, the position of the zoom lens 3, that is, the focal length information is read by the lens control unit 19.

Information on the aperture 4 is also converted into an electrical signal by the aperture sensor 22 and read by the lens control section 19.

The electrical signal from the distance scale sensor 13 is A/D converted by the A/D converter 17 and inputted to the calculation section 28 of the microcomputer 18 as photographing distance information. When the information and aperture information are entered manually, the calculation section 28 reads each of these pieces of information and refers to each characteristic curve that is the content of the storage section 30 . After calculating the appropriate extension position of the rear group lens 5 from the characteristic curve suitable for the human power information, the calculation section 28 sends a signal corresponding to this to the motor drive circuit 31.
to rotate the stepping motor 8 to an appropriate position. As a result, the rear lens 5 receives focal length information,
The camera stops with the aperture information (i.e., depth of field) taken into consideration and the camera focused on the desired shooting distance.

To put the focus adjustment device into the autofocus state, as shown in Figure 3.4, rotate the operation ring 6 in the direction of arrow C, and go beyond the "infinity" position to the "auto" position (not shown). ).

At this time, the control circuit 11 is switched to perform a control operation for autofocus, and the stepping motor 8 moves the rear lens group 5 in the direction of the arrow A, using a pulse based on a frequency of 15 Hz from the control circuit 11. It is vibrated alternately in the optical axis direction along B (see Figure 2). Since the rear group lens 5 vibrates in the optical axis direction, the optical path length changes slightly, so the level of the high frequency component included in the luminance signal inputted to the autofocus processing circuit 25 changes slightly. The fluctuation waveform of this high frequency component (
The modulation signal) is at its minimum in the focused state, and the phase of the modulation signal is reversed by 180' between the front and rear focus, so
When the goldfish signal is input from the autofocus processing circuit 25 to the calculation unit 28 of the control circuit 11, the calculation unit 2
8 gives a signal to the motor drive circuit 31 for vibrating the stepping motor 8 back and forth with the same amplitude around the focal point. Since this amplitude is determined in consideration of the aperture information, that is, the depth of field, the rear lens group 5 is actually in the same state as if it were stationary at the in-focus point. In this in-focus state, a display signal is sent from the calculation section 28 to the distance display device 27, and the distance of the in-focus point is displayed using a light emitting diode, liquid crystal, or the like.

When the focal point deviates from the focused point and a front focus or rear focus signal is guided from the autofocus processing circuit 25 to the calculation unit 28 of the control circuit 11, the calculation unit 28
A signal is given to the stepping motor 1 to cause the stepping motor 8 to vibrate and step toward the focal point. That is, by applying a signal to the stepping motor 8 that vibrates with a large amplitude toward the in-focus point and with a small amplitude in the opposite direction, the rear group lens 5 moves toward the in-focus point.

Note that during autofocus, the zoom lens 3 is connected to the motor 2.
The speed at which the rear lens group 5 moves toward the in-focus point 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 this.

The distance scale sensor 13 in the above embodiment converts the distance scale into an electrical signal using a change in resistance value, but in addition to this, for example, the distance scale sensor 33 shown in FIG.
．． Alternatively, a distance scale sensor 43 shown in FIG. 8 or the like may be used. As shown in FIG. 7, the distance scale sensor 33 includes a 3-bit photosensor 34 integrally attached to the operating ring 6, and a 3-bit photo sensor 34 attached to the outer periphery of the fixed frame of the lens barrel 1 for each bit along the rotational direction. The lead wire of the photosensor 34 is connected to the microcomputer 18 of the control circuit 11. Therefore, in this distance scale sensor 33, the photo sensor 34 reads the presence or absence of the reflector 35, 36, 37 based on the presence or absence of reflected light at a position corresponding to the amount of rotation of the operating ring 6, converts this into an electrical signal, and converts it into an electric signal. Since the distance scale is sent to the computer 18, the distance scale is read into the microcomputer 18 as a digital signal.

Further, as shown in FIG. 8, the distance scale sensor 43 has a 3-bit conductive contact 44 integrally attached to the operating ring 6, and a rotation direction for each bit on the outer periphery of the fixed frame of the lens barrel 1. The conductor 45 is grounded, and the other conductors 46 to 48 are connected to a voltage V by resistors 51 to 53. C is applied thereto, and is connected to the input terminal of the microcomputer 18. Therefore, in this distance scale sensor 43, the conductive contact 44 short-circuits or opens the conductors 46 to 48 and the conductor 45 depending on the rotational position of the operation ring 6. Each of these is a low level “L” (ground) or a high level “
becomes Ho (voltage vcc), microcomputer 1
The distance scale will be manually set using a 3-bit digital signal.

Note that the distance scale sensor 33°43 shown in Fig. 7.8 is 3
Although it is assumed to have a bit configuration, it is actually a telephoto (T)
condition, the distance of 0.5m-oo (see Figure 6) is approximately 80
It is desirable to have a configuration of about 7 bits so that it can be divided into 100 bits.

Furthermore, although the embodiments described above apply the present invention to a method of driving the rear group lens 5, the present invention can also be applied to a method of driving the front group lens 2. For example, in a lens barrel that allows macro photography, the front group lens must be moved significantly from the normal photography area to the macro area, but in such cases, the microcomputer 18
By storing a characteristic curve representing the movement characteristics of the front group lens in the storage section 30 of the camera, complicated movement of the front group lens can be smoothly performed without using a cam mechanism.

[Effects of the Invention] As described above, according to the present invention, the focusing lens can be moved to a position according to the distance setting operation of the operating member using a simple electrical circuit configuration without using a cam mechanism or the like. This allows for highly accurate focus adjustment.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electric circuit of a focus adjustment device showing an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the driving portion of the rear group lens in FIG. 1, and FIG. FIG. 4 is a schematic configuration diagram showing an example of the distance scale sensor shown in FIG. 1, and FIG. 5 is a control circuit shown in FIG. 1 above. 6 is a characteristic curve diagram for lens control stored in the storage section in FIG. 5, and FIG. 7.8 is a block diagram showing some of the functions of the sensor. FIG. 5... Rear group lens (focus lens) 6...
...Operation ring (operation member) 8...Stepping motor (lens drive means)
11... Control circuit (focus adjustment signal generation means) 13... Distance scale sensor (distance setting signal generation means) Bird 22 Stone 30

Claims (1)

[Scope of Claims] An operating member that performs a distance setting display for setting a distance by external operation; a distance setting signal generating means that outputs a distance setting signal in response to a distance setting display operation of the display operating member; A focus adjustment signal generating means for receiving a distance setting signal and generating a focus adjustment signal having a predetermined correspondence with the setting signal; and a lens driving means for driving a focus lens based on the focus adjustment signal. A focusing device characterized by: