JP3506103B2 - Zoom lens barrel and focusing control method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens barrel. More specifically, the present invention relates to a focus reference switch that provides a reference position for focusing control at each zoom position in a zoom lens barrel that employs a zoom focus integrated drive mechanism (step zoom) that performs zooming and focusing with a single drive mechanism. .

[Prior art]

In a zoom focus integrated drive mechanism,
At the time of focusing control at each zoom position, a specific amount of movement of the focusing lens has been performed by using a switch provided between two appropriate cylindrical members that constitute the lens barrel and relatively move. However, in the case of a segment type switch, the switch piece that constitutes the switch is deformed during long-term use, and other types of switches, such as switches using photoelectric elements such as photo reflectors, are also affected by posture differences and external forces. The position at which the switch is turned on often shifts due to the displacement of the relative positions between the tubular members. If this happens, the rotational position of the lens barrel, which is the reference for focusing control, will also be displaced, and this will cause deterioration of focusing accuracy.

[0003]

SUMMARY OF THE INVENTION Therefore, the technical problem to be solved by the present invention is to use a zoom lens barrel in which the lens barrel rotation position as a focusing reference is difficult to be displaced even after long-term use, and to use the same. It is to provide a focusing control method.

[0004]

SUMMARY OF THE INVENTION The present invention has been devised in order to effectively solve the above problems, and provides a zoom lens barrel having the following features.

The zoom lens barrel of the present invention is a zoom focus integral drive type (step zoom) zoom lens barrel, wherein each lens group includes a plurality of focusing sections and a plurality of zooming sections alternately. Focusing control at a plurality of divided zoom positions by moving on one zoom line is performed by a single mechanism. The zoom lens barrel of the present invention is "a zoom reference switch which is composed of a switch provided between relatively moving cylinders and which gives one zoom reference pulse to each zoom position" and "always connected to the outer cylinder portion". A coarse pulse generator that is interlocked with the outer cylinder through the first gear train, and the wavelength (λ) of the coarse pulse generated from the coarse pulse generator allows the zoom reference pulse to continue to be used.
The amount of deviation that has been set in anticipation of further occurrence
A coarse pulse generator that is longer than the length corresponding to the lens barrel rotation amount that is twice the lens barrel rotation amount corresponding to the placement error and shorter than the length corresponding to the total lens barrel rotation amount at each zoom position. While interlocking with the outer cylinder through the second gear train,
And a fine pulse generator for generating a fine pulse having a wavelength shorter than the half wavelength (λ / 2) of the coarse pulse.

In the zoom lens barrel having the above structure, the coarse pulse generator is interlocked with the outer cylinder through the first gear train that is always connected to the outer cylinder. That is, the coincidence and reproducibility between the coarse pulse and the lens barrel rotation position are high. Regarding the reproducibility, unlike the switch on the lens barrel exposed to the outside of the camera, it is inside the camera and is not affected by external force.Because the gear is attached directly to the fixed part shaft, the structure is simple and accurate. It is easy to put out and is not easily affected by the difference in posture. Also,
Since the coarse pulse generator can be installed in the gear that is accelerating from the rotation of the lens barrel, even if the pulse detection error is about the same as the switch error on the lens barrel, The coarse pulse generator has less influence on the error of the focusing movement amount. Therefore, by making the focusing start position on the lens barrel at each zoom position of the step zoom correspond to one specific coarse pulse (focus reference pulse) and counting the pulses with this as a reference, only the rotation amount necessary for focusing is obtained. If you drive the lens barrel,
Accurate focusing can always be achieved. The coarse pulse generator can be placed in the middle of the reduction gear train that transmits the driving force from the motor, but considering that the driving force influences the distortion and deformation of the gear train, the precision pulse generator Configure a gear train that does not apply driving force to the body rotation,
It is advantageous to arrange the coarse pulse generator there. In view of this point, the present invention also includes a coarse pulse generator that interlocks with the outer cylinder portion via a first gear train that does not apply a lens barrel driving force, and a second gear train that transmits the lens barrel driving force to the outer cylinder portion. It is arranged.

Since this coarse pulse occurs a plurality of times at each zoom position of the step zoom, it is necessary to determine and select which of them is actually used as the focus reference pulse. To find this focus reference pulse, an intercept switch as a zoom reference switch and a fine pulse generator are used. The zoom reference switch is
The zoom reference pulse is provided to determine which zoom position the lens barrel is at, and is configured to be generated once at each zoom position of the step zoom. The correspondence between the zoom reference pulse obtained by the switch between the lens barrels and the actual lens barrel rotation position depends on the play between the barrel members, the attitude difference,
In the case of an external force or a segment type switch, it is not strictly maintained constant due to its deformation or the like. However, the fluctuation cannot be tolerated as the deterioration of focusing accuracy, but can be kept within a certain range. In the present invention,
The roughness of the rough pulse is set so that only one peak of the rough pulse exists in the lens barrel rotation range corresponding to this fixed range.

That is, the wavelength (λ) of the coarse pulse is longer than the length corresponding to the lens barrel rotation amount that is twice the “lens barrel rotation amount corresponding to the position error of the zoom reference pulse”, and the wavelength at each zoom position is different. Shorter than the length corresponding to the total amount of lens barrel rotation. Therefore, the position error of the zoom reference pulse can be absorbed, and one focusing start position can be set for each zoom position. Therefore, by performing the following control, it is possible to perform accurate focusing control with the focusing start position kept constant regardless of the position error of the zoom reference pulse.

First, the lens barrel rotation amount from the zoom reference pulse to the focus reference pulse given by the intercept switch is counted by the fine pulse number, and the fine pulse number n is stored. This is stored in the control unit of the camera or other optical device including the lens barrel. Then, in the subsequent focusing control, the number of fine pulses is counted from the zoom reference pulse by the intercept switch, and n ±±
The number of pulses required for focusing is counted from the coarse pulse existing in the range of λ / 2 or less (there is only one). Strictly speaking, there is a boundary point within ± λ / 2 when there are two coarse pulses ± λ /
Although it should be 2-1 pulse, it is described here as ± λ / 2. That is, this coarse pulse that is always present within the range of n ± λ / 2 is used as the focus reference switch. It should be noted that the specific number of pulses required for focusing should be tabulated in correspondence with the distance to the subject, or
Alternatively, it is described as a predetermined mathematical expression and the table or mathematical expression is stored in the control unit. The distance to the subject is measured by a normal distance measuring means.

[0010]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. 1 to 3 are sectional views showing an embodiment of the zoom lens barrel of the present invention. 1 shows a telephoto state, FIG. 2 shows a wide state, and FIG. 3 shows a retracted state.

The illustrated zoom lens barrel 1 includes a zoom driving barrel 200, a rotary barrel 300, and a cam barrel which are extended in multiple stages from a fixed barrel 100 fixedly fixed to a camera body (not shown).
Including 400. The zoom drive barrel 200, the rotary barrel 300, and the cam barrel 400 each include an outer barrel portion and an inner barrel portion that are coupled to each other using a bayonet structure and are relatively rotatable and immovable in the optical axis direction. That is, the zoom drive cylinder 200 is composed of an outer cylinder part 210 and a straight advance lead cylinder 220 inside thereof, the rotary cylinder 300 is composed of an outer cylinder part 310 and a straight advance guide cylinder 320 inside thereof, and the cam cylinder 400 is outside. Tube part 410 and lens holding tube inside it
It consists of 420 and.

When the driving force is transmitted from the drive gear 262 shown in FIG. 3 to the gear portion 211 formed on the outer cylinder portion 210 of the zoom drive cylinder 200, the helicoid portion 101 on the inner surface of the fixed cylinder and the helicoid on the outer surface of the outer cylinder portion. The portion 212 cooperates to drive the zoom drive barrel 200 forward and backward in the optical axis direction. In conjunction with this, the rotary barrel 300 and the cam barrel 400 also move forward and backward in the optical axis direction.

The zoom lens barrel 1 is provided with three lens groups 10, 20 and 30 of first to third, and all of these lens groups are unitized in a cam barrel 400 located at the most distal end side. Is held. That is, the first lens group 10 is fixed to the tip end side of the lens holding barrel 420, and the third lens group 30 is fixed to the base end side of the lens holding barrel 420. Second lens group 2
0 is held by the lens holding barrel 420, and moves in the optical axis direction when the outer barrel 410 and the lens holding barrel 420 rotate relative to each other. That is, a follower pin (not shown) fixed to the lens frame 21 of the second lens group 20 is formed between the linear guide slot 421 formed on the lens holding cylinder and the cam groove 411 formed on the inner peripheral surface of the outer cylinder. When the outer cylinder portion 410 and the lens holding cylinder 420 are rotated relative to each other, the second lens group 20 moves in the optical axis direction along a predetermined zoom line described later with reference to FIG.

In the zoom lens barrel 1, the first lens group 10
The third lens group 30 is immovable with respect to the cam barrel 400, but the second lens group 20 moves relative to the cam barrel 400. The element indicated by 450 in FIG. 1 is a bellows as a light shielding element. Bellows 450 is the first lens group 10
This is a cylindrical member fixed to the lens frame 11 and the frame portion 350 of the shutter unit, and expands and contracts as the first lens group 10 and the second lens group 20 move relative to each other. Figure 4 shows the mechanism.
Will be described with reference to.

4 (a) to 4 (c) are cross-sectional views of essential parts showing the process of expansion and contraction of the bellows 450. As shown in FIG. As can be seen from FIGS. 1 to 3, since the second lens group 20 moves together with the shutter unit, the relative movement of the frame portion 350 in FIG. 4 with respect to the first lens group 10 is the first lens of the second lens group 20. This corresponds to the relative movement with respect to group 10. The bellows 450 is fixed at its both ends to the lens frame 11 and the frame portion 350 by using the fittings 15 and 351 respectively. Metal fittings 15
Is a ring-shaped member slidably arranged around the lens frame 11 and can slide in the optical axis direction with respect to the lens frame 11. As can be seen from FIGS. 4A to 4C, as the bellows 450 expands and contracts, the relative position of the metal fitting 15 with respect to the ball frame 11 changes. By the relative movement of the metal fitting 15 in this manner, it is possible to prevent an unreasonable force from acting on the bellows and prevent deterioration of the bellows made of rubber or the like.

FIG. 4A shows the bellows 450 in the most expanded state. From this state, the frame part 350 is the first
When the lens group 10 is approached and the state shown in FIG. 4B is reached, the tip end 350a of the frame portion gives a turning force in the direction of arrow A to the bellows 450, and the tip end portion 11a of the lens frame points to the bellows 450. Gives turning power in the B direction. Furthermore, the frame part 35
When 0 approaches the first lens group 10, the state of FIG. 4C is reached, and the bellows 450 is in a completely folded state.

With such a folded structure of the bellows 450, the bellows 450 can be accommodated with a small number of folds in the donut-shaped accommodation space 370 having a small expansion in the radial direction of the lens barrel. As the number of folds of the bellows 450 decreases, the lateral bending (bending in the lens barrel radial direction) during expansion and contraction decreases. Therefore, by adopting such a configuration and reducing the deflection of the bellows 450, it is possible to prevent the bellows 450 from interfering with the elements inside the lens barrel to prevent smooth expansion and contraction of the lens barrel, or the bellows 450 itself may be damaged. It can be prevented.

The zoom lens barrel 1 employs a zoom focus integrated drive mechanism (step zoom) for performing zooming and focusing with a single drive mechanism. This is because each lens group moves on one zoom line that alternately includes a zooming section and a focusing section, and is conventionally known as a configuration for reducing the size and cost of the zoom lens barrel. ing.

FIG. 5 shows the "lens barrel rotation angle", "first lens group 10 (first component), second lens group 20 (second component), and third lens" in the zoom lens barrel of FIG. Group 30 (3rd
FIG. 6 is a zoom diagram showing a relationship with “amount of movement of component) in the optical axis direction”. The zoom line 12 shows the total movement amount of the first component with respect to the camera body, the zoom line 13 shows the total movement amount of the second component with respect to the camera body, and the zoom line 14 shows the total movement amount of the third component with respect to the camera body. ing.

As can be seen from FIG. 5, in this zoom lens barrel, tele, wide, and 3 between them are used.
One step, that is, a step zoom for performing a total of five steps of zooming is adopted. Focusing is performed in the focusing section of the stepped line 13, and zooming is performed in the other sections (zooming section). FIG. 6 is a development view showing the inner peripheral surface of the outer cylinder portion 410 of the cam cylinder 400, and illustrates the shape of the cam groove 411 formed on the inner peripheral surface of the outer cylinder portion 410. The left side in the figure is the subject side,
The right side is the photographer side. As described above, the follower pin (not shown) provided on the lens frame 21 holding the second component engages with the cam groove 411. Three cam grooves 411 are provided at equal intervals along the circumferential direction of the inner peripheral surface. Each cam groove 411 partially includes a portion 411a that returns to the photographer side, and this portion corresponds to the focusing section on the zoom line 13.

In this camera, one zoom position
When focusing is performed (for example, the zoom position of the middle 3), control is performed to move a predetermined optical system in the optical axis direction by a movement amount corresponding to the distance to the subject measured by the distance measuring unit. The specific amount of rotation of the lens barrel corresponding to this amount of movement is controlled by the number of pulses. That is, the lens barrel rotation position (focusing start position) that is the reference for starting the focusing control is set in advance, and the lens barrel rotation amount from the start position is controlled according to the number of pulses.

FIG. 7 is a sectional view schematically showing a conventional example for giving the reference position. This is an example in which the intercept switch is adopted. Switch segment 41 on the inner surface of the outer tube 40
While the film-shaped terminal 51 is fixed, the film-shaped terminal 51 is fixed to the outer peripheral surface of the inner cylindrical portion 50. Therefore, the switch is turned on when the rotation position of the lens barrel coincides with the predetermined reference position, and the number of pulses from the switch is counted according to the object distance, thereby focusing to a desired position. Focusing control is performed by moving the lens.

However, in such a conventional sliding contact switch, the actual focusing start position differs from the actual focusing start position due to the mounting error, the play between the cylindrical members which occurs during long-term use, the bending of the segment 31, and the like. The pulse counting will start from the lens barrel rotation position. Even for other types of switches, for example, switches using photoelectric elements such as photo reflectors, the positions at which the switches are turned on may shift due to displacement of the relative positions between the tubular members due to posture differences, external forces, etc. Many. If this happens, the starting criteria for focusing will deviate, making it impossible to perform accurate focusing. In the present invention, the structure shown in FIG. 8 is adopted so that such a deviation does not occur.

The zoom lens barrel 1 is rotated by a drive gear 262 (see FIG. 3), and the drive gear 262 constitutes a gear train 260 (first gear train) together with the driven gear 261.
The coarse pulse generator 250 is connected to the outer peripheral surface of the outer cylinder portion 210 of 00 through a gear train 260 (first gear train). Coarse pulse generator 250
Is composed of a slit plate 251 and a photo interrupter 252. The slit plate 251 has a gear train for the outer cylinder 210.
It is connected via 260 and rotates following the outer cylinder part 210. The gear train 260 is always connected to the outer cylinder part 210.
(In other words, the planetary gear mechanism etc. are not provided in the middle and the connection is not broken.)
Can generate a pulse that is highly consistent and reproducible with respect to the rotational position of the lens barrel. Also, the coarse pulse generator 25
Since 0 is outside the lens barrel, there is no adverse effect such as rattling between the tubular members. The correspondence between the pulse generated by the coarse pulse generator 250 and the lens barrel rotation position is indicated by the focus pulse (FP) in FIG.

Therefore, if a specific one pulse of the focus pulse is adopted as the focus reference switch, there is a problem of "deviation of focusing start reference" caused by the conventional switch (FIG. 7) provided between the barrels of the lens barrel. Will not occur. In the example of FIG. 9, the pulse 251a is adopted as the focus reference pulse. That is, the rotational position of the lens barrel corresponding to this pulse is the starting position of focusing control. Since the zoom lens barrel according to the present invention employs step zoom, one such focus reference pulse is set for each photographing focal length.

Focusing with high accuracy can be performed by counting the number of pulses with the pulse 251a as a reference, but in actual focusing control, it is necessary to find out which pulse is the reference pulse 251a.

In order to find the focus reference pulse 251a, the present invention adopts the configuration schematically shown in FIG. This structure also includes a switch provided between the barrels of the conventional lens barrel as described in FIG. As shown in FIG. 8, the switch piece 213 is fixed to the inner peripheral surface of the outer tube portion 210, while the film-shaped terminal 221 is fixed to the outer peripheral surface of the straight lead tube 220. This intercept switch functions as a zoom reference switch for the step zoom set in 6 stages. The relationship between the pulse generated by this switch and the lens barrel rotation position is indicated by the zoom reference SW in FIG. One reference pulse similar to the zoom reference pulse 213a is given to each zoom position.

As described above, in the segment type switch, the switch piece constituting the switch is deformed during long-term use, or the switch type other than the switch piece, for example, a switch using a photoelectric element such as a photo reflector is used. In many cases, the position at which the switch is turned on is displaced due to the displacement of the relative position between the tubular members due to the influence of the difference or the external force. However, this deviation amount can be suppressed within a certain range centered on the original position. In the present invention, the wavelength of the coarse pulse generated by the coarse pulse generator 250 is set to a length that can absorb this shift amount. It will be described below with reference to FIG. In Figure 9, "λ"
Indicates the wavelength of the coarse pulse, that is, the interval between the rising portions of two adjacent pulse peaks, and "e" indicates the range in which the deviation can occur around the position of the zoom reference pulse at the time of storage. Shows. Half wavelength of coarse pulse "λ / 2"
Is set to be larger than "e". Therefore, there is always one coarse pulse within the range of ± λ / 2 centering on the position of the zoom reference pulse 213a including the actual error, and the coarse pulse is always the focus reference pulse 251a.

In order to search for a coarse pulse existing within the range of "± λ / 2" around the position of the pulse (zoom reference pulse 213a) by the actual zoom reference SW, the fine pulse generator 230 in FIG. Used. The fine pulse generator 230 is
It is composed of a slit plate 231 and a photo interrupter 232. The slit plate 231 is connected to the shaft of the motor 150 and rotates in conjunction with the shaft of the motor 150. Motor 1
The gear 50 is connected to the outer cylinder part 210 via a gear train 240.
The correspondence between the pulse generated by the fine pulse generator 230 and the lens barrel rotation position is shown in FIG. 9 as a drive motor pulse (DMP).
Indicated by. At the downstream end of the gear train 240, a planetary gear 241
By this, the driving force from the driving gear 150 is selectively transmitted to a film feeding system or a film winding system (not shown) by planet gear locking means (not shown). The pulse generated by the fine pulse generator 230, that is, the drive motor pulse (DMP) is also used for controlling the film feeding or film winding system. Therefore, the fine pulse generator 230 needs to be arranged on the motor side of the planetary gear 241, and the resolution, that is, the number of pulses generated with respect to the amount of rotation needs to be relatively large. Therefore, the fine pulse generator 230 is arranged in the vicinity of the motor 150, which is rotated at a high speed with respect to the lens barrel rotation, that is, at a position accelerated with respect to the lens barrel rotation. Since the gear train 240 is not always connected to the outer cylinder part 210, it is not possible to generate a pulse having a high degree of agreement and reproducibility with respect to the rotational position of the lens barrel, as compared with the coarse pulse generator. However, the relative position interval between the zoom reference pulse 213a and the focus reference pulse 251a in FIG. 9 can be counted by the number of fine pulses.

The fine pulse generator 230 is also used for finely setting the position where the focusing lens should be stopped during focusing control. The focusing stop control method of this embodiment is as follows. First determined by converting the focus lens feeding pulses corresponding thereto when the distance of the object is determined by the number of fine pulses by the distance measuring means (not shown). The specific number of pulses required for focusing is made into a table corresponding to the distance to the subject, or described as a predetermined mathematical expression, and the table or mathematical expression is stored in the control unit. Then it is replaced by coarse pulse + fine pulse. In this embodiment, 32 coarse pulses are set to be generated for one coarse pulse. Therefore, for example, when the target pulse is 70 in terms of fine pulses, coarse pulse: 2 + fine pulse: 6 Become. The control first determines the focus reference pulse 251a by the above-mentioned means. Secondly, coarse pulses are counted, and finally fine pulses are counted and stopped. In this way, in addition to the above-mentioned high-precision focusing start criterion using the coarse pulse, most of the focus extension amount can be performed with the coarse pulse having high consistency and reproducibility with respect to the rotation position of the lens barrel. Focusing with higher accuracy becomes possible as compared with the case where the amount of feed is counted only by a fine pulse. Further, when all the focus extension amounts are counted by only the coarse pulses, the focus extension resolution becomes low and the focus extension accuracy also becomes low. In order to increase the focus extension resolution while counting the focus extension amount only with coarse pulses, it is necessary to set the gear train 260 (first gear train) to the same reduction ratio or speed increase ratio as the gear train 240.
Increases the number of gears and space. In the present embodiment, highly accurate focusing can be performed without increasing the number of gears and the space. Here, the movement amount counted by the fine pulse has low coincidence and reproducibility with respect to the rotational position of the lens barrel, but since it is a movement amount that is sufficiently small with respect to the total delivery amount, the delivery accuracy is not so high. It has no effect. In this embodiment, as shown in FIG. 8, the fine pulse generator 230 is connected to the outer cylinder portion 210 via a larger number of reduction gears than the coarse pulse generator 250. As a result of providing such a reduction ratio, 32 fine pulses are generated for one coarse pulse. The focus extension amount is about 5 μm for one fine pulse, and
About 5 × 32 = 160 μm is set for one coarse pulse, and the total feeding amount at each zoom position is set to about 3 mm. In this case, the number of pulses during focusing is around 600 when converted to fine pulses, and when converted to coarse pulses
It becomes around 19 pulses. If the matching and reproducibility errors due to the interposition of the planetary gears are 100 μm when the total feed amount is controlled by fine pulses, it is 1 in 600 pulses.
Since it is 00 μm, the error in this embodiment is caused by only the last fine pulse, so 100 × 32/600 =
It is around 5.3 μm. Since this error is about the fine pulse resolution, it has little effect as an error, and is sufficiently smaller than the resolution of 160 μm only for the coarse pulse, so that the accuracy is higher than the control for only the coarse pulse. Therefore, if this control method is used, even if the planetary gear is interposed between the drive source and the driven part and the consistency and reproducibility of the drive source and the driven part are deteriorated, the number of gears and the space are increased. Without
The amount of movement of the driven part can be controlled with high accuracy.

As shown in FIG. 8, the fine pulse generator 230
Are connected to the outer cylinder part 210 via a larger number of reduction gears than the coarse pulse generator 250. As a result of providing such a reduction ratio, 32 fine pulses are generated for one coarse pulse. Then, as described above, the mounting error "e" of the zoom reference switch composed of the intercept switch is set to be smaller than "λ / 2". Therefore, the zoom reference pulse 213 by the zoom reference SW, which is considered to include the actual error.
A coarse pulse existing within the range of ± 16 pulses with the fine pulse number centered on the position of a is searched for. In this way, the coarse pulse found is always the focus reference pulse 251a.
It can be ensured that Moreover, since the focus reference pulse 251a has high coincidence and reproducibility with the focus start position, if the pulse counting is started with this as a reference, accurate focusing can be performed.

In the camera configured as described above, the number of rotations of the lens barrel from the position of the zoom reference pulse 213a to the position of the focus reference pulse 251a before manufacturing and shipment corresponds to how many pulses when counted in fine pulses. It is preferable to actually measure whether or not each zoom position of the step zoom is stored in the camera itself.

Suppose that the actually measured data at this time is 5 fine pulses.
It is assumed that (n = 5). It is assumed that the segment switch 213 is deformed or the relative position between the tubular members is displaced as the user uses the camera after shipping as a product. This causes an error in the relative relationship between the position of the zoom reference pulse 213a and the position of the focus reference pulse 251a (here, the position of the zoom reference pulse 213a includes an error, but the position of the focus reference pulse 251a Is absolutely correct). However, even in this case, the error is considered to be within the range of "e", and therefore the range of ± 16 fine pulses (n ± λ / 2) centered on the 5 fine pulses which is the above-mentioned measured data. There is always only one coarse pulse inside, and that coarse pulse is always the focus reference pulse 251a. In other words, with the zoom reference pulse 213a including the actual error as the reference, −1
If the coarse pulse existing within the range of 32 fine pulses in total from 1 fine pulse to 21 fine pulse is used as the focus reference switch, the coarse pulse is consequently the focus reference pulse 251.
Since it coincides with a, the starting reference position of focusing control can be accurately maintained at a fixed position.

As described above, according to the above configuration, an accurate focusing start reference position can be secured irrespective of deformation of the section switch due to long-term use by the user after shipment as a product. Further, according to the above configuration, since the focus extension amount is determined by the coarse pulse + fine pulse during focusing control, it is possible to perform highly accurate focusing without increasing the number of gears and the space. As can be seen from FIG. 9, the amount of movement of the focusing lens during focusing control
(That is, the optical axis direction moving distance from the count start position to the stop position) is determined by using both the number of focus pulses FP (coarse pulses) and the number of drive motor pulses DMP (fine pulses). That is, the moving amount of the focusing lens, which is determined by X coarse pulses and Y fine pulses, is represented by X · FPI + Y · DMPI.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a multi-stage zoom lens barrel of the present invention in a telephoto state.

FIG. 2 is a cross-sectional view showing a wide state of the zoom lens barrel of FIG.

FIG. 3 is a cross-sectional view showing a retracted state of the zoom lens barrel of FIG.

FIG. 4 is a cross-sectional view of main parts for explaining expansion and contraction of bellows in the zoom lens barrel of FIG.

5 is a zoom diagram of a first lens group and a second lens group in the zoom lens barrel of FIG.

6 is a development view showing an inner peripheral surface of a cam cylinder outer cylinder part of the zoom lens barrel of FIG. 1. FIG.

FIG. 7 is a schematic cross-sectional view showing a conventional configuration in which a focus reference position is given by using a section switch.

FIG. 8 is a schematic diagram showing a configuration for providing a focus reference position in the present invention.

FIG. 9 is a schematic diagram illustrating a focus reference position in the present invention.

[Explanation of symbols]

1 Zoom lens barrel 10 First lens group 11 ball frame 12 Zoom line of the 1st lens group 13 Zoom line of the 2nd lens group 14 Zoom line of the 3rd lens group 15 metal fittings 20 Second lens group 21 ball frame 30 Third lens group 40 Outer cylinder 41 switch intercept 50 Inner cylinder 51 Film terminal 100 fixed tube 101 helicoid part 150 motor 151 drive shaft 200 zoom drive tube 210 Outer cylinder part 211 Gear part 212 Helicoid part 213 switch segment 213a Zoom reference pulse 220 Straight lead tube 221 Film terminal 230 Fine pulse generator 230 231 slit plate 232 Photointerrupter 240 gear train 241 Planetary gear 250 coarse pulse generator 251 slit plate 251a Focus reference pulse 252 Photointerrupter 260 gear train 262 drive gear 300 rotating cylinder 310 Outer cylinder 311 Helicoid part 320 Straight guide tube 350 Focus unit frame 351 metal fittings 370 Bellows accommodation space 400 cam barrel 410 Outer cylinder 411 cam groove 420 lens holder 421 Straight guide slot 450 bellows

Claims (3)

(57) [Claims] 1. Each lens group moves on one zoom line including a plurality of focusing sections and a plurality of zooming sections alternately, and focusing control at a plurality of divided zoom positions is performed by a single mechanism. , In the zoom focus integrated drive type zoom lens barrel, it is composed of a switch provided between the cylinders that move relative to each other, and a zoom reference switch that gives one zoom reference pulse to each zoom position and is always connected to the outer cylinder part. A coarse pulse generator that is interlocked with the outer cylinder via the first gear train, and the wavelength (λ) of the coarse pulse generated from the coarse pulse generator is generated by continuing to use the zoom reference pulse. The lens barrel rotation at each zoom position is longer than the length corresponding to the lens barrel rotation amount that is twice the lens barrel rotation amount corresponding to the position error that is the deviation amount set in consideration of Coarse pulse generator shorter than the length corresponding to the rotation amount, linked to the outer cylinder through the second gear train to the outer cylinder, and shorter than the half wavelength (λ / 2) of the rough pulse. An optical device including a zoom lens barrel , comprising: a fine pulse generator that generates a fine pulse of a wavelength.
On the lens barrel from the zoom reference pulse at each zoom position.
Lens barrel up to coarse pulse corresponding to focusing start position
The amount of rotation is counted by the number of fine pulses, and the number of fine pulses
(n) is stored in the device, and in the subsequent focusing control, the switch is used.
The number of fine pulses is counted from the zoom reference pulse
With reference to the coarse pulse existing in the range of n ± λ / 2
And count the number of pulses needed for focusing from there.
Focusing control for focusing
An optical device, comprising: a section . 2. Each lens group has a plurality of focal points.
One that includes a single section and multiple zooming sections alternately
Move on the zoom line of to move to multiple divided zoom positions.
Zoom with a single mechanism for focusing control
In the focus-integrated drive type zoom lens barrel, it is composed of switches provided between the barrels that move relative to each other.
Zoom that gives one zoom reference pulse for each zoom position
The outer cylinder part is connected via the reference switch and the first gear train which is always connected to the outer cylinder part.
Is a coarse pulse generator that works with
The coarse pulse wavelength (λ)
Settings that are set in anticipation of what happens when you continue
Lens barrel that is twice the amount of lens barrel rotation that corresponds to the position error
The total length at each zoom position is longer than the length corresponding to the rotation amount.
Coarse pulse generator shorter than the length corresponding to the amount of lens barrel rotation
And when the outer cylinder portion is interlocked with the outer cylinder portion via the second gear train,
Also, for wavelengths shorter than the half wavelength (λ / 2) of the above coarse pulse,
A fine pulse generator for generating a fine pulse,
In an optical device including a zoom lens barrel , characterized in that at each zoom position, the amount of lens barrel rotation from the zoom reference pulse to the coarse pulse corresponding to the focusing start position on the lens barrel is counted by the number of fine pulses, The fine pulse number
(n) is stored in the device, and in subsequent focusing control, counting is performed by the fine pulse number from the zoom reference pulse by the switch, and the coarse pulse existing in the range of n ± λ / 2 is used as a reference, A focusing control method in which focusing is performed by counting the number of pulses required for focusing. 3. The focusing control method according to claim 2, wherein the fine pulse number n is measured in manufacturing the lens barrel and then stored in the apparatus.