JPH01304415A - Lens driving mechanism - Google Patents

Abstract

PURPOSE:To improve control at the time of fine driving by providing a lens driving device with a driving characteristic switching means which switches its driving characteristics and an arithmetic control means with a control means which controls the operation of the driving characteristic switching means according to lens information. CONSTITUTION:This is the lens driving mechanism equipped with the lens driving device 4 which drives the photographic lens 1 of an interchangeable lens 10 mounted detachably on a camera main body 1 and the arithmetic control means 2 which controls the driving of the driving device 4 according to focus detection information. The lens 10 is equipped with a storage means 6 stored with lens information corresponding to the kind of the lens 10, the lens driving device 4 is equipped with the driving characteristic switching means 4c which switches the driving characteristics, and the arithmetic control means 2 is equipped with the control means which controls the operation of the driving characteristic switching means 4c according to the lens information.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a lens drive mechanism that drives an interchangeable lens in an autofocus camera, and more particularly to a lens drive mechanism that can switch drive characteristics in response to drive load torque of the interchangeable lens.

[Conventional technology]

In conventional interchangeable lens type autofocus cameras, the mechanism that drives the photographic lens generally has a drive groove reduction system determined to match the interchangeable lens with a large load torque, so it is difficult to use an interchangeable lens with a small load torque. Even if there is one, it takes a relatively long time because it is driven at the same reduction ratio, and this is a problem in promoting faster automatic focusing (hereinafter referred to as AP). For faster AF, AP
On the sensor side, it is required to increase the allowable image surface speed of 7 to F, in other words, to shorten the accumulation time, or on the lens drive system side, it is required to increase the lens drive speed to the limit of the above-mentioned allowable image surface speed. Ru. To increase the driving speed of the lens, ■Reduce the deceleration within the lens (reduce the number of rotations of the autofocus coupler required to move the image plane of the subject by a certain amount), and reduce the number of rotations of the autofocus (AF) coupler by one rotation. There are two ways to deal with this: 1) increasing the image plane speed of the shot, and 2) increasing the rotational speed of the AF coupler on the camera body. However, with ■, when an interchangeable lens is attached to a body with a slow allowable image surface speed of the AF sensor, it may not be compatible. Furthermore, play (backlash) in a part of the coupler has a large effect on control accuracy. Regarding the above-mentioned item (2), there is an example disclosed in Japanese Patent Application Laid-Open No. 62-50736. In this disclosed example, the torque corresponding value is determined depending on the type of lens and the position of delivery. ”?, OM
This information is used to change the drive power and perform optimal control. Therefore, the disclosed example is not intended to increase the driving speed, but to improve control during minute driving by changing the driving pulse.

[Problem to be solved by the invention]

Conventional interchangeable lens autofocus cameras, including the example shown here, do not have technology to increase the lens drive speed, and therefore even a lens with a light load torque can be compared to a lens with a heavy load torque. The disadvantage is that they can only be driven at the same driving speed. SUMMARY OF THE INVENTION An object of the present invention is to provide a lens drive mechanism that enables an interchangeable lens with a light load torque to be driven at a high speed and an interchangeable lens with a heavy load torque to be driven at a low speed. There is.

[Means for solving the problem, and actions/effects] (Structure
In order to achieve the above object, the present invention was constructed as follows. That is, the lens drive mechanism of the present invention includes a camera body that includes:
comprising a lens driving device for driving a photographing lens of an interchangeable lens detachably attached to the camera body, and an arithmetic control means for driving and controlling the driving device based on focus detection information,
Further, the interchangeable lens is provided with a storage means in which lens information corresponding to the type of the lens is stored, the lens drive device is provided with a drive characteristic switching device capable of switching the drive characteristics of the device, and the arithmetic control means and a control means for controlling the operation of the drive characteristic switching means based on the lens information. Furthermore, the lens driving device compares the allowable image surface speed (or value related to it) of the AP sensor of the device with the maximum image surface speed (or value related to it) under the set drive characteristics. A comparison means for determining the magnitude is provided in the arithmetic control means, and the drive characteristic switching means is operated based on the comparison result of the comparison means to correct the driving of the lens driving device so as not to drive at a speed exceeding the allowable image surface speed. The lens drive mechanism may be configured as follows. Furthermore, a temperature sensor that measures the ambient temperature and outputs a predetermined signal is provided in the interchangeable lens, and if the temperature sensor detects that the interchangeable lens is being used in a low temperature range, the drive characteristics described above are detected. The lens drive mechanism may be configured to operate a switching means to correct lens drive to appropriate drive characteristics. In one aspect, the lens information may be a torque value or a torque-corresponding value determined depending on the type of the interchangeable lens. Alternatively, it may be used as the focal length and F number of the lens. (Function) According to the above configuration, it becomes possible to perform lens driving for focus adjustment of the photographing lens with appropriate drive characteristics based on the above lens information in correspondence with an interchangeable lens. In other words, even when driven by a drive motor with a predetermined driving force, the lens can be driven with a light load (i.e., an interchangeable lens that can be driven with light torque).
Therefore, based on the lens information of the attached interchangeable lens, the drive characteristic switching device is switched to perform high-speed rotation drive for a light-load lens, and for a heavy-load lens, high-speed rotation drive is possible. Can perform low-speed rotational drive. Furthermore, by comparing the allowable image plane speed of the AF sensor with the maximum image plane speed in the set drive characteristics, it is also possible to perform control so that the allowable image plane speed is not exceeded. Furthermore, temperature information from the temperature sensor can be used as a reference value for switching drive characteristics. In addition, when the above-mentioned lens information is the focal length and F number of the lens, even if it is an interchangeable lens that does not have torque information, it becomes possible to realize lens drive that matches the lens drive characteristics. This is because, in general, the longer the focal length of the lens or the smaller the diameter, the greater the torque required to drive the lens, so the required driving torque can be predicted based on the focal length and F-number. (Effects) In this way, the drive characteristics when driving the lens can be changed according to the type of interchangeable lens, so the output of the drive device, which was limited by the heavy torque lens of the interchangeable lens stem, can be changed. A lens with a light rotational torque allows high-speed rotation. Therefore, the time required for automatic focus adjustment is also shortened. Further, the lens drive mechanism according to the second aspect is further preferable because it has the effect of driving an interchangeable lens with poor lens drive characteristics in a low temperature range with appropriate drive characteristics. In the lens drive mechanism according to the third aspect, since the drive characteristics are directly switched based on the torque information, it is possible to simplify the configuration of the arithmetic control means. On the other hand, the lens drive mechanism according to the fourth aspect can also be used for interchangeable lenses that do not have torque information.

【Example】

Below is part 1~! Embodiments of the present invention will be specifically described according to FIG. First, a first embodiment will be described based on FIGS. 1 to 8. Figure 1 is an overall configuration diagram showing the camera of this embodiment;
Figures A and 2B are configuration diagrams of the drive unit of the above camera;
4 is a diagram showing the output characteristics of the drive unit, FIG. 4 is a drive unit configuration diagram showing a modification of the drive unit), FIG. 5 is a drive control circuit diagram of the drive motor used in the modification, and FIG. Figure 6 is a diagram explaining the limit between the coupler drive speed and the value (hereinafter, the K value refers to the number of revolutions of the AF coupler required to move the subject image by a predetermined amount), and Figure 7 is a diagram showing the above FIG. 8 is a flowchart explaining the operation of the camera, and is a conceptual diagram of a control circuit built into the lens of the camera. In Figure 1,! 0 is an exchangeable lens, 11 is a camera body, and the lens 10 can be detachably attached to the camera body 2. This lens 10 includes a photographing lens I for focusing on a subject,
A focusing mechanism 8 that performs a focusing operation of the lens l.
and storage means for storing lens information such as the K value and the lens driving torque value for lens focusing, specifically the lens r' (OM), and storing this lens information on the interchangeable lens 10 side. A calculation unit 6 configured to transmit information from the calculation unit 6 to the camera body 11 side is provided.On the other hand, the camera body Il side includes a calculation control unit 6 that executes a predetermined operation based on the information from the calculation unit 6. unit 2
A drive unit 4 drives the focusing mechanism 8 via an AP coupler 5 based on instructions from the arithmetic and control unit 2, and an AP element 3 detects focus information corresponding to a subject. In addition, 7a is the main mirror,
7b is a mirror that guides light to the AP element 3. Further, the lens ROM of the arithmetic unit 6 stores the above values, torque values, and other predetermined information. The coupler torque of the interchangeable lens 10, that is, the input torque, is divided into two by the divided torque value: Td, and those with a torque value larger than Td are divided into two, and those with a torque value larger than Td are divided into two, and those with a smaller torque value are "0".
As shown in FIGS. 2A and 2B, the drive unit 4 includes a drive motor 4a, a plunger 4C, and a torque limiter.
4b, a photointerlurator 9, and a gear train 4d. The above-mentioned folio interlator 9 is designed to detect the rotation speed of the coupler 5 connected to the output gear 4e by the number of pulses, and is used for AF control. At this time, the arithmetic control unit 2 determines the amount of defocus (focal shift) detected by the AF element 3 and the drive amount of the coupler necessary to move the image plane by a predetermined amount. The coupler driving amount is calculated, and autofocus is controlled based on the driving amount and information indicating the driving amount outputted from the photo interlator 9. That is, when it is detected based on the output from the photointerlurator 9 that the coupler has been driven by the required amount, the drive is stopped. Torque limiter-4b above
is limited by removing the drive force transmission path in the middle of the gear train 4d so that excessive torque is not applied to the drive system mechanism. That is, this torque limiter 4b is caused by the gear 4g, which is attached to the output gear 4e and is pressed by a spring 4f and is integrated with the output gear 4e, slipping with respect to the output gear 4e at a constant torque value: TL. Output torque is limited. The plunger 4c is for switching the drive characteristics of the drive unit 4, specifically the reduction ratio of the reduction system,
The gear ratio is switched so that a light torque lens is in a high speed mode (Hi), and a heavy torque lens is in a low speed mode (Lo). In other words, two-stage switching is performed: driving with the reduction system shown in FIG. 2A and driving with the reduction system shown in FIG. 2B. As described above, the output characteristics of the drive unit 4 in the two modes are shown in FIG. In the figure, N indicates the rotational speed of the AP coupler 5, T indicates the torque value of the coupler 5, and η indicates the efficiency of the drive unit 4, respectively. According to the figure, the high speed mode (Hi) can drive faster with a lighter lens than the torque value TC, and the low speed mode (L
It can be seen that since the lens O) can generate a high torque, it is possible to efficiently operate a lens heavier than the torque value 2TC. What is shown in FIG. 4 is one modification of the drive unit described above. In this drive unit, instead of switching the reduction ratio, the output characteristics of the drive motor are switched. Therefore, the plunger 4C provided in the drive unit 4 is not required. Note that the other components are the same as the drive unit 4 described above. That is, the drive motor 4a' shown in FIG. 4 is provided with two types of coils wound around the rotor, and is controlled by the circuit configuration shown in FIG. In FIG. 5, L3. Lt indicates a coil wound around the rotor of the motor, and such a coil L1. The drive motor 4a' equipped with L t can be switched between high torque drive and low torque drive by switching the switch SWI. The switching of this switch SWI is
According to the torque information of the torque acting on the coupler 5, it is controlled by the arithmetic and control unit 2 of the camera body 2, and the drive circuit 12 of the drive motor 4-a' is controlled by the arithmetic and control unit 2. Above switch SWl
When switching and connecting to one A contact SWa side, coil L
. and coil L are connected in series, making it possible to generate high torque, and the drive unit enters a low speed mode. On the other hand, when the switch SWI is reversely switched, it is connected to the B contact SWb side, so only the other coil L1 becomes conductive and enters the high speed mode. In this way, a high speed mode and a low speed mode can also be obtained. By the way, the limit of the AP coupler driving speed, here the number of rotations (K) of the coupler 5 required to move the image plane of a certain subject by 1 mm, will be explained using FIG. The K value varies depending on the lens 10.
Even if it is 0, it changes when zooming. When the rotation speed of the coupler 5 is N (rev. /5ec), the speed of the image plane: ■ is v=N+K (
mm/5ee) - (1). On the other hand, in the figure, 1Dfl is the maximum amount of defocus that the AP element 3 can detect, and if the insect is defocused more than this, both the defocused insect and the direction cannot be detected. Also, A
The F element 3 performs focus detection at a period of Tsmpl. This period +Tsmpl depends on the ccD accumulation time, and becomes shorter if the subject is brighter and longer if it is darker. Now, while driving the lens IO at a certain speed, the time when focus detection was performed: to, the defocus happened to be +Df'',
Assume that it is undetectable at this time. Next focus detection is T
Timetable after smp 1 hour: tl, and at this time, if the image surface velocity is Vl, it is a defocus amount that can be detected (Dr
(smaller) can be focused. However, when the speed is V3, the defocus exceeds "-Dr" and cannot be detected. In other words, the in-focus point is moved too far. Velocity 2 V2 is the boundary velocity for such a decrease, and in order to be able to focus, it is necessary to keep the velocity below V. In Fig. 3, N Hmay is the maximum drive speed in high-speed mode, N L
max is the maximum drive speed in low-speed mode, and the value limit for each mode is formula (1)% formula (2) shows the value limit. When it is bright, the period/Tsmpl becomes shorter, so V2 becomes faster, so the value; K11iS
For both KLo, a smaller value is sufficient. Table 1 The operation of the camera with the configuration described above will be explained with reference to FIG. In the figure, at step #10, a start switch S (not shown) is activated. (This switch is turned on when the shutter release button is touched) is determined to be on. If it is on, the control calculation unit 2 reads the lens data in step #11. This data includes values, lens torque data, and other data necessary for AP in addition to the F-number etc. necessary for photometry. Note that if it is not turned on, that is, if the shutter release button is not touched, there is no consent to take a picture, and the camera will not operate at all. Next, in step #12 photometry is carried out, and in step #13 it is determined whether the torque signal taken in from the arithmetic unit 6 indicates "0" or "bi", that is, the lens torque data indicates "light". If the torque signal indicates "0", that is, "light", the process proceeds to step #14, where it is determined whether the value is greater than the previous value. If judged,
Proceeding to step #15, the mode is set to high speed mode and the drive unit 4 is driven in the high speed mode. That is, the plunger 4c is operated to switch to a high speed gear. Alternatively, in Figure 4.5, switch SW
Switch I and connect it to the B contact SWb side to switch the motor drive circuit to the high speed circuit. On the other hand, if it is determined in step #13 that the torque signal is "the same", that is, "heavy", and if the value is smaller than K11i in step #14, the process proceeds to step #16, and the value is set to the minimum value in the low speed mode. : Compare with KLo and if I(≧Kl, o, proceed to step #17 and set low speed mode. In step #16, K<KL
. If so, since AP is not possible, the process advances to step #18 and autofocus is prohibited. Regardless of whether the high speed mode or the low speed mode is set, when the shutter release button is pressed one step, the release switch S1 is turned on. Therefore, if AF is not prohibited in step #18, it is determined in step #19 whether the switch Sl is on. If it is turned on, it will go to switch 20 and start AF operation.
The lens is focused in step #21. Here, if the shutter release button is pressed further, the release switch S2 is turned on, so in step #22 it is determined whether the release switch S is on or not, and if it is on, the process goes to step #23. Advance release is executed. Note that if the switch S1 is off in step #19, the process waits until it is turned on. Further, if the release switch S is off in step #22, the process waits until it is turned on. When the release is completed and the shooting frame ends, the program returns to its original state and waits for the next shooting operation. Although the above explanation applies to a camera body that has a drive mechanism that includes a motor, it can also be applied to a camera that has a drive mechanism that includes a motor on the lens side. (which may vary depending on the type of body) can be output toward the lens side, and the drive mechanism on the lens side can be switched to a drive mode that allows AF and is driven the fastest. FIG. 8 shows the structural concept of the control unit built into the interchangeable lens 10. The control unit 6 receives signals from the zoom encoder ZE and the temperature sensor TS, and also performs calculation control on the camera body side 11. Information is exchanged with Unit 2. The zoom encoder ZE switches the information transmitted to the camera body 11 side when the lens is a zoom lens, and the temperature sensor TS changes the torque of the AF coupler 5 depending on the temperature after normal temperature and at low temperature. It is now used for lenses that are As shown in Table 2, various data stored in the lens ROM of the arithmetic circuit in the control unit 6 are switched and transmitted to the camera body side using the zoom encoder ZE output and temperature sensor TS output. . (Left below) As is clear from the explanations in Table 2 and above, the lens drive mechanism of this embodiment is capable of driving each interchangeable lens by selecting appropriate drive characteristics for that lens. Compared to a camera that uses one fixed drive mode, it is possible to switch between driving a light-load lens in a high-speed rotation mode and driving a heavy-load lens in a low-speed rotation mode. As a result, in a light-load lens, a faster AP can be achieved. By the way, in the first embodiment described above, the drive mode of the drive unit is switched based on the drive torque information of each lens, but in the second embodiment disclosed in FIGS. 9 to 11, the above-mentioned Instead of torque information, the required torque for each lens is predicted using the focal length (r) and F number of the lens to execute drive mode switching. FIG. 9 is a flowchart explaining the operation of the camera;
This figure shows the motor current at the time of motor startup, and FIG. 11 is a flowchart that captures torque as a motor current value and explains the drive mode switching operation based on this value. That is, in general, the longer the focal length of the lens or the longer the diameter of the lens, the heavier the torque of the AF coupler 5 of the lens. As shown in Table 3, the coupler torque is predicted using the focal length/f and the F number, and the drive mode of the drive unit 4 is temporarily set. Table 3 In this case, the temporarily set mode may be inappropriate, so the torque is measured when lens drive is started and the mode is corrected. Below, the operation of the camera of this embodiment will be briefly explained based on FIG. 9. In the figure, similarly to the first embodiment, when the shutter release button is touched, the start switch S is released. turns on. Therefore, in step #30, this switch S is changed. It is determined whether or not is on, and if it is on, the process advances to step #31 and the lens data is read. Next, a photometry operation is performed in step #32. Everything up to this point is the same as the first embodiment. Next, the drive mode of the drive unit 4 is temporarily set based on the data read in step #31. This completes the correspondence of coupler torque between the camera body 11 and the interchangeable lens 10 attached to the camera body 11. Then, when the shutter release button is pressed one step, the shooting preparation switch SI is turned on, so it is determined in step #34 whether or not the switch SI is on, and if it is on, the process advances to step #35; The program will wait until it is turned on. A distance measuring operation is performed in step #35, and a focusing operation is performed by driving the lens in step #36. During this lens drive, coupler torque is measured to determine whether the current drive mode is appropriate for the attached lens 10 (step #37). If it is determined in step #37 that the drive mode is not appropriate, the process proceeds to step #39, where the mode is corrected and lens drive is continued. In this case the drive unit 4 is controlled to operate in a modified mode. If the temporarily set mode is appropriate or after the mode has been corrected, the torque value is determined to be appropriate in step #37, and the lens is focused in step #38. Thereafter, as in the first embodiment, if the release switch S is pressed further, the release switch S is turned on, so if it is determined in step #40 that it is on, the process proceeds to step #41, and in step #41 the camera is released. and shooting is completed. Incidentally, the torque value can be determined by measuring the motor current I when the lens is started, as shown in FIG. 1O. That is, the current torque value can be determined based on the current value ls after a certain period of time t1 after starting the motor. That is, as shown in FIG. 1+, if the temporarily set drive mode is the low speed mode, the drive mode is determined in step #50, and since it is the low speed mode, the process proceeds to step #51. Step #5
After starting the motor in step 1, a comparison is made to see if the motor current value Is after t4 time is larger than the lower limit reference value 2u. If Is<lu, the process proceeds to step #53, where the drive mode is switched to the high speed mode, that is, the mode is corrected, and then the process proceeds to a predetermined operation. If it is determined in step #51 that Is<Iu, the process proceeds to step #52, where it is determined that the torque value is appropriate, and the process proceeds to the next predetermined operation in that mode. If the temporary setting mode is the high speed mode, the process proceeds from step #50 to step #54, and in step #54, the flow value Is of mode 711 after t1 time is compared with the upper limit reference value IO. Is
>ro, proceed to step #56;
Switch to low speed mode and proceed to predetermined operation. If Is>Io is not found in step #54, the torque value is determined to be appropriate in step #55, and the process proceeds to the next predetermined operation in that mode. In this way, it is also possible to select an appropriate lens drive mode and execute lens drive using the focal length and F-number of the lens as lens information.

[Brief explanation of the drawing]

1 to 11 show a lens drive mechanism according to an embodiment of the present invention, and FIGS. 1 to 8 are diagrams showing a first embodiment,
Figure 1 is an overall configuration diagram of the camera, Figures 2A and 2'U3 are configuration diagrams of the drive unit of the camera, Figure 2A is in low speed mode, Figure 2B is in high speed mode, and Figure 3 is in high speed mode. 4 is a diagram showing the output characteristics of the drive unit, FIG. 4 is a drive unit configuration diagram showing one modification of the drive unit, FIG. 5 is a drive control circuit diagram of the drive motor used in this modification, and FIG. 6 is a diagram showing the output characteristics of the drive unit. The figure is a diagram explaining the limits of the AP coupler drive speed and value, Figure 7 is a flowchart explaining the operation of the camera, Figure 8 is a conceptual diagram of the control circuit of the camera, and Figures 9 to 1. ! The figures show the second embodiment. Fig. 9 is a flowchart explaining the operation of the camera, Fig. 1O is a diagram showing the motor current when the drive motor is started, and Fig. 11 is a diagram showing the drive mode based on the measured current value. It is a flowchart explaining switching operation. l... Photographic lens, 2... Arithmetic control means (arithmetic control unit), 3... AP element 1.4... Drive device (drive unit), 4 a, 4 a'... Drive motor, 4b...L Lucrimisoter, 4c... Drive characteristic switching means (plunger), 4d... Gear train, 4e...
・Output gear, 4f...spring, 4g...gear, 5...
・AF coupler, 6... storage means (computation unit),
7a, 7b...Mirror, 8...Focusing'd
9 h'? , 9... Photointerlabter, IO・
・Interchangeable lens, 11...Camera body, 12...Drive circuit, SWI...Drive characteristic switching means (switch), I-+
, Lt...coil, TS...temperature sensor,
ZE...Zoom encoder.

Claims (1)

[Claims] 1. A photographing lens (1) of an interchangeable lens (10) detachably attached to the camera body (11).
); and an arithmetic control means (2) that controls the drive of the drive device (4) based on focus detection information. The interchangeable lens (10) is equipped with a storage means (6) that stores lens information corresponding to the type of the lens (10), and the lens drive device (4) is equipped with a storage means (6) that stores lens information corresponding to the type of the lens (10). The calculation control means (2) is equipped with a control means for controlling the operation of the drive characteristic switching means (4c: SW1) based on the lens information. A lens drive mechanism characterized by: 2. The interchangeable lens (10) is equipped with a temperature sensor (TS) that senses the ambient temperature and outputs a predetermined signal, and the lens driving device (4) is driven by the output signal of the temperature sensor. Based on the drive characteristic switching means (4c: S
2. The lens drive mechanism according to claim 1, wherein the correction is made by operating W1). 3. The lens drive mechanism according to claim 1 or 2, wherein the lens information is a torque value or a torque corresponding value determined depending on the type of the interchangeable lens. 4. The lens drive mechanism according to claim 1 or 2, wherein the lens information is a focal length and an F-number of the lens.