JP2565337B2 - Subject distance display device for cameras with varifocal lens - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a subject distance display device for a camera provided with a varifocal lens, and more specifically, to a variable power lens group and a lens unit arranged on the same optical axis. A variable-magnification optical system consisting of a focusing lens group, in which the relationship between the subject distance and the amount of extension of the focusing lens group in the optical axis direction differs depending on the magnification position within the variable magnification range, the subject distance of a camera equipped with a varifocal lens. The present invention relates to a display device.

(B) Prior Art Since the zoom lens has no image-forming position shift (so-called focus movement or focus shift) even when zooming operation is performed, it is easy to operate without any troublesome focus adjustment for each zooming operation. Further, the zoom lens has an advantage that the moving amount of the focusing lens group is substantially the same for the same object distance in the entire zoom range (hereinafter, this is referred to as “equal amount movement”). The object distance display device can be configured by simply attaching the distance scale to the operation member (distance ring) of the focusing lens group and attaching the index to the fixed ring disposed adjacent to the operation member. There is an advantage that it is not necessary to change the subject distance scale.

However, although it varies depending on the lens configuration of the variable power optical system, particularly in the case of the inner focusing type and rear focusing type zoom lenses, when the optical design is performed under the condition that the above-mentioned equal movement is realized, the lens configuration is There was a problem of complication. Further, there is a problem that the moving amount (extending amount) of the focusing lens unit on the wide angle side becomes unnecessarily large. In other words, when it corresponds to a single focus lens, for example, 140m
When the amount of movement of the focusing lens unit in the telephoto lens of m is 16 mm, the amount of movement in the wide-angle (short focus) lens of 35 mm is about 1 mm, whereas in the case of a zoom lens having a zoom ratio of 4 Because of the condition of equal movement, a stroke of 16mm is still required on the wide angle side. This also causes a problem that the outer diameter of the lens increases and the weight of the lens and the lens barrel increases.

In other words, since the zoom lens cannot escape from the above-mentioned condition of the equal movement of the zoom lens, the problem that it is difficult to realize compactness and cost reduction still remains.

Therefore, the present applicant previously filed a patent application as Japanese Patent Application No. 62-013345 for an invention relating to a varifocal lens control device capable of solving the above-mentioned problems (hereinafter referred to as "prior invention").

That is, the varifocal lens control device according to the invention of the prior application, a focal length detecting means for detecting the focal length of the entire system, a focusing lens group position detecting means for detecting the position of the focusing lens group on the optical axis, A maximum extension amount calculation means for receiving the output of the focal length detection means and calculating the extension amount from the infinity position to the closest position of the focusing lens group at the focal length, the maximum extension amount calculation means, and the focusing lens. Proportional constant calculation means for receiving the outputs of the group position detection means and calculating the ratio of these outputs, and the outputs of the proportional constant calculation means, the maximum feed amount calculation means, and the focusing lens group position detection means, respectively. Focusing correction calculation means for calculating, as a correction value, an amount of image forming position deviation from the in-focus position caused by updating the focal length of the entire system, and a focusing lens group driving device. The drive means, the movement amount monitoring means for generating a signal corresponding to the movement amount of the focusing lens group, and the outputs of the movement amount monitoring means and the focus correction calculation means respectively receive the focusing lens group. A focusing control means for controlling to drive to a focusing position, a scaling driving means for driving the scaling lens group, and a startup signal from a separately provided startup means to control the scaling drive means. The zoom control unit is configured to automatically correct the image forming position shift due to the update of the focal length of the entire zoom optical system.

According to the invention of the prior application thus configured, the lens optical system itself has a very simple configuration, and is small, lightweight, and inexpensive, and the entire lens control device is similarly small, lightweight, and inexpensive, Even if the zoom lens group is moved from the arbitrary first focal length to the second focal length to update the focal length of the entire system, the image shift peculiar to the varifocal lens is instantly corrected and the in-focus state is maintained. Therefore, it is possible to obtain the same thing as a zoom lens in terms of usability.

However, as will be described later in detail, in the varifocal lens, the movement amount of the focusing lens group is different between the long focus side and the short focus side (that is, depending on the focal length of the entire system) because the condition of the equal amount movement is removed, In other words,
Even though the focusing lens group is not moved, the image forming position is displaced, and accordingly, the display of the object distance that has been displayed until then must be changed accordingly. For this reason, as described above, it is impossible to display the subject distance as easily as with a zoom lens, which makes the display device extremely complicated and makes it difficult to recognize the display.

(C) Object The present invention has been made in view of the above circumstances, and an object of the present invention is to use a varifocal lens, which is an inexpensive, small-sized, and simple optical system, and to combine it with variable power operation. An object of the present invention is to provide a subject distance display device for a camera equipped with a varifocal lens that can automatically perform the extension correction of the focusing lens group and can display the subject distance that is easy to see with a simple configuration.

(D) Configuration In order to achieve the above-mentioned object, the present invention is a variable power optical system including a variable power lens group and a focusing lens group arranged on the same optical axis. In a camera provided with a varifocal lens whose relationship with the amount of extension of the focusing lens group in the optical axis direction differs depending on the magnification position within the zooming range, a focusing drive means for driving the focusing lens group, and the scaling lens group Zooming drive means for driving the zooming lens group, and zooming lens group position detecting means for detecting the position of the zooming lens group on the optical axis,
Focusing lens group position detecting means for detecting the position of the focusing lens group on the optical axis, and outputs from the focusing lens group position detecting means and the magnification varying lens group position detecting means, to perform a magnification varying operation. Focusing correction calculation means for calculating the extension correction amount of the associated focusing lens group, focusing control means for receiving the output of the focusing correction calculation means and controlling the focusing lens group through the focusing drive means, Subject distance display means for receiving the outputs of the focusing lens group position detecting means and the variable magnification lens position detecting means, updating the display contents of the subject distance at predetermined time intervals, and holding the display contents during the predetermined time intervals. It consists of and.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to that, the theory serving as the basis of the present invention will be described.

The zoom lens is defined as a lens that does not move due to a zooming operation (updating the focal length f of the entire system). As a starting point of the theory of the present invention, the focus movement is allowed first. (Finally, this focus movement is corrected to bring it into a focused state). Note that the present theory will be described on the premise of the front focusing method.

It is natural that the rotation of the motor and the change of the angle of view are linear when the change of the angle of view due to the zooming operation is visually recognized, especially when using a so-called power zoom in which the zooming operation is driven by a motor or the like. is there. This change in the angle of view is the reciprocal of the focal length f of the entire system, that is, 1 / f
Is substantially proportional to the rotation of the motor and the focal length f of the entire system.
If and are proportional, the change in the angle of view looks natural. Further, assuming a means for detecting the focal length f of the entire system, and assuming that the focal length information Zp output from the detecting means is proportional to the rotation of the motor, Cp _{0 and} Cp ₁ are As a setting constant determined at the time of designing, the relationship between the focal length f of the entire system and the focal length information Zp for the change in the angle of view to appear natural can be expressed as in equation (1).

Now, in this theory, since the change of the focal length f _F of the focusing lens unit F as the focusing lens unit is allowed, the focusing lens unit F on the wide angle side caused by the equal amount movement which the conventional zoom lens has is caused. of allowed reducing unwanted movement amount, also determine the relationship between the focal length f _F of the focal length f and the focusing lens unit F that may caused to reduce the lens diameter with this.

 Therefore, consider the relationship shown in the following equation.

f _F ² = C _F0 · f (2) where C _F0 is a setting constant similar to the above.

Multiply both sides of equation (2) by 1 / f ² and then add (1) to the right side.
By substituting the equation, the equation (3) is obtained.

Here, if the film surface defocus amount as the AF calculation result is δ and new setting constants C ₁₀ and C ₁₁ are introduced, the movement amount Δ of the focusing lens group F to the focus position is Δ = ( C ₁₀ · Zp + C ₁₁ ) · δ (4) It can be calculated from the following formula.

 Now, consider how to find the subject distance.

Assuming that the focus position information Sx is output in proportion to the position (movement amount) of the focusing lens unit F in the optical axis direction, and the setting constant is C ₃₀ , the following formula (5) is obtained.

Sx = C ₃₀ · Δ (5) Therefore, if C ₄₀ , C ₄₁ , and C ₄₂ are new setting constants, d ₁ = (C ₄₀ · Zp + C ₄₁ ) · Sx + C ₄₂ (6) You can ask for _one .

Here, in order not to make the code complicated, the equation (6) is changed to the equation (7).
Rewrite like a formula.

D = (C ₀ · Zp + C ₁ ) · Sx + C ₂ (7) Here, D is the subject distance, D = d ₁ , C ₀ , C ₁ , C ₂ are setting constants determined at the time of design, and C ₀ = C ₄₀ , C ₁ =
C ₄₁ and C ₂ = C ₄₂ . That is, if the means for controlling Zp and Sx so that the subject distance D does not change in the formula (7) is realized, the focus movement due to the zooming operation is eliminated (correction).
It will be possible. However, the focusing lens unit F
The amount of movement is not equal to the above movement. In other words, the present theory can be said to be a theory that actively removes the condition of equal displacement.

Now, description will be made of an embodiment of a subject distance display device of a camera provided with a varifocal lens according to the present invention.

FIG. 1 is a block diagram showing the overall configuration. First
In the figure, reference numeral 1 is an optical axis of a variable power optical system, 2 is a variable power lens group which is arranged on the optical axis 1 so as to be movable along the optical axis 1 and constitutes the variable power optical system, and 2a , 2b, 2c, 2d and 2e are a first lens group, a second lens group, a third lens group, a fourth lens group and a fifth lens group, each of which is composed of a single lens or a plurality of lenses. Then, the first lens group 2a and the second lens group 2b constitute the focusing lens group F as the focusing lens group described in the explanation of theory, and are therefore formed from the first lens group 2a and the second lens group 2b. Focal length is
f _F , which includes the first group lens 2a and the second group lens 2b, and the third lens group 2c to the fifth lens group 2e constitute the variable power lens group 2 which is also described in the explanation of the theory. The focal length is fz. Of course, the focal length of the entire variable power optical system including the variable power lens group 2 is f. 3 is the film surface, 4 is the focal length f of the entire system from the telephoto side focal length as the best focal length (hereinafter abbreviated as "tele side") to the wide angle side focal length as the shortest focal length (hereinafter simply referred to as "wide side"). The variable-magnification drive unit 5 including a variable-magnification motor Mz as a variable-magnification driving unit that drives the variable-magnification lens group 2 to set an arbitrary focal length up to The first lens group 2a and the second lens group 2b are driven to a focusing position between the infinity position (∞ position) and the closest position on the optical axis 1 corresponding to the subject distance from infinity to the closest distance (in detail). the focus drive unit consisting of the focus motor M _F and a mechanism (not shown) of the optical axis direction allowed to move) focusing drive means while maintaining the distance between the first lens 2a and the second group lens 2b constant, 6 and 7 are the above It is driven by the focus driving unit 5 together with the first group lens 2a and the second group lens 2b, and among these, 6 generates a pulse proportional to the number of rotations from the photo interrupter 6b when the slit disk 6a is driven to rotate. A focus counter for detecting the amount of movement of the first lens group 2a and the second lens group 2b on the optical axis 1, and 7 is a voltage proportional to the positions of the first lens group 2a and the second lens group 2b on the optical axis. ,
A focusing lens group position detector (hereinafter abbreviated as "FPM") as focusing lens group position detecting means for outputting as the focus position information Sx described in the explanation of the theory, 8 is a variable magnification lens group 2 and variable magnification drive The whole system focal length f is driven by the unit 4
To the focal length information Zp described in the explanation of theory.
A variable power lens group position detector (hereinafter abbreviated as "ZPM") as a variable power lens group position detecting means for outputting as the Zp, after receiving the focal length information Zp and performing A / D conversion.
A maximum payout amount calculation unit as a maximum payout amount calculation means for calculating the movement amount (that is, the payout amount) Fpx of the first group lens 2a and the second group lens 2b from the ∞ position to the close position in
Reference numeral 10 receives the output Fpx of the maximum feed amount calculation unit 9 and the output Sx of the FPM 7 as focus position information, and A / D
After conversion, these ratios are calculated, and a proportional constant calculating unit as a proportional constant calculating means for outputting a proportional constant Cfp, 11 is a correction amount Dfp for receiving and focusing on the three outputs Fpx, Cfp, Sx. And a focus correction calculation unit as a focus correction calculation unit that calculates the display output DS, and 12 receives the output Dfc of the focus counter 6 and the output Dfp corresponding to the correction amount of the focus correction calculation unit 11 and receives the focus drive unit. A focus control unit as a focus control unit for controlling 5; 13 constitutes a starting unit, and 13a and 13b are variable power switches each of which is an externally operable push button switch for activating a variable power operation.
a is a magnification up switch (hereinafter simply “up switch”)
13b is a magnification down switch (hereinafter simply referred to as "down switch"), 13c is these switches 13a, 13b.
The drive direction determination unit that outputs the start signal (STR) after determining the rotation direction of the variable power motor Mz in response to the output of the above, and 14 receives the display output (DS) and determines the subject distance by an internal timer (not shown). The subject distance display section to be displayed on the subject distance display described later at the time interval of, for example, the focusing lens group 2a, which includes an AF section for measuring the subject distance and an externally operable focus switch for activating this distance measuring operation. , 2b in the moving direction MDR = 1, MDR = 1, and the moving amount (correction amount Daf) to the focus control unit 12. The maximum feed amount calculation unit 9 and the subject distance display unit 14 constitute subject distance display means. Further, the proportional constant calculation unit 10, the focus correction calculation unit 11, and the focus control unit 12 constitute a focus control means. Further, while the subject distance display unit 14 is operating, the other units are configured to rest. This is hereinafter referred to as "interrupt operation".

In addition, the correction amount Daf output from the focus instruction unit 15
Indicates the amount of movement to the in-focus position. The movement direction MDR = 1 indicates movement from the infinity position to the close position, and the movement direction MDR = -1 indicates movement on the contrary from the close position to the infinity position. .
Reference numeral 16 denotes a variable power control unit serving as variable power control means for controlling the variable power drive unit 4 in response to the start signal STR and the output Fpx.
Incidentally, + V indicates a power source. The input / output relation of each part shows only the main signal.

FIG. 2 is a graph showing the characteristics of the apparatus of the present invention shown in FIG. 1, and shows the total system focal length f to be set and the object distance D of the focusing lens groups (first group lens 2a and second group lens 2b). Is shown for each representative subject distance D, and the vertical axis represents the change in the total system focal length f.
The horizontal axis shows the amount of extension of the focusing lens unit with reference to the in-focus position with respect to the infinity position. In this example, the tele position is f = 135 mm, and the wide position is f = 35 mm. In FIG. 2, 17 to 22 are focusing curves, which are focal length information when the subject distance D on the left side is set to ∞, 6.0m, 3.0m, 2.0m, 1.5m, 1.2m in equation (7). 9 shows changes in the amount of extension of the focusing lens groups 2a and 2b from the infinity position to the in-focus position with respect to changes in Zp. Therefore, the focusing curve 22 is the closest focusing curve that provides the maximum amount of extension, and in particular, the closest focusing curve 22 is set to Fpx. That is, assuming that the closest subject distance D is D ₀ and Sx = Fpx, the equation (7) becomes By separating the constants, the following equation is obtained.

Furthermore, in the equation (9), C ₁₁ = C ₁ , C ₂₂ (D ₀ ) = C ₂ , C
_{33 If} (D ₀ ) = C ₃ , Is obtained.

FIG. 3 is a graph for omitting a part of FIG. 2 for explaining the operation of FIG. 1, particularly the operation of each arithmetic unit.

In FIG. 3, Zp (i), S (i) and Ep (i)
Are the focal length information (first
Focal length information) Zp, focus position information Sx and above
Focusing curve 17 of ∞ in Zp (i) to the closest focusing curve 22
Is the transfer amount (maximum feed amount) to Zp (e), F
p (e) and Dfp are the focal length information (second
Focal length information), the movement amount from the focusing curve 17 to the focusing curve 22 in Zp (e), and the correction amount for correcting the focus movement. That is, the proportional constant Cfp immediately before the scaling operation
Let (11) be the closest focus curve at this time.
It becomes the formula (12).

In the above equation (13), Cfp ′ is a proportional constant after a predetermined time has elapsed.

If Cfp = Cfp ′ holds, no focus movement occurs. To do so, equation (13) must hold. The focusing curve 22 at this time is given by equation (14). Therefore,
Replace the left side of equation (13) with Cfp and use it as the denominator on the right side (14)
Substituting the equations and rearranging gives equation (15). In addition, (1
As for the formula (5), the formula (14) is transformed into the formula (8) → the formula (9) →
The following equation is obtained by modifying the equation (10).

Sx ( _T ) is the focus position information Sx when the focal length information Zp is at the position on the tele side, and S ₀ ( _T ) is the focus position information Sx when the above Sx ( _T ) is on the closest focusing curve 22.
(That is, the intersection of Sx ( _T ) and Fpx). Incidentally, reference numeral 23 is a focusing curve at an arbitrary subject distance drawn as described above.

FIG. 4 is a diagram conceptually showing a configuration of a display for displaying a subject distance. For example, reference numeral 24 denotes a numeral indicating the distance of the subject, which is engraved or printed on the outer periphery of a lens barrel (not shown). Reference numeral 25 denotes a display dot such as a liquid crystal which serves as an index when turned on, and reference numeral 26 denotes a dot address corresponding to each display dot 25 on a one-to-one basis. If the precision when the focal length information Zp is A / D converted is 8 bits,
Focus position information S
Similarly, if x is also 8 bits, 0 corresponds to the ∞ position and 255 corresponds to the closest position. Display dot 25
There are 16 of them. Therefore, from the above equation (8), the following (17)
Expressions (18) and (19) are obtained.

By transforming (17) and assigning it to the denominator on the right side of (18),
By transforming (19) and assigning it to the numerator on the right side of (18), and rearranging using (8), we obtain (20).

Is What is meant by this formula, the ratio of the Sx the ratio of the Sx and Fpx in the third view of any Zp in the same manner as described in the description has been standardized on the telephoto position _(T) and S _{0 (T)} When equal to
Sx _(T) is true it means that correspond to the (actual) subject distance, because the S _{0 (T)} as described above is was made to correspond to 255 (20) to S _{0 (T)} Substituting = 255 ((2
1) Obtain the formula. On the other hand, the display function D indicating the dot address 26
Since S1 ( _T ) has 16 display dots 25, the following equation (22) is obtained, and equation (21) is substituted into equation (22) to obtain equation (23).

FIG. 5 is a diagram for explaining the operation of the embodiment shown in FIG. 1, and the same parts as those in FIGS. 2 and 3 are designated by the same reference numerals. In FIG. 5, 27, 28, 29 and 30 are the intersections with the respective focusing curves 17, 18, 19 and 22 on Zp = Zp ( ₁ ), respectively, and the output S∞ = 0, S _{2 of the} FPM 7 respectively. , S ₁ , S ₀ are supported. Similarly, 31 is the intersection with the focusing curve 19 on Zp = Zp ( ₂ ) and corresponds to the output S ₁ ′ of the FPM 7, respectively. Z
p ( _T ) is the value of Zp on the tele side already described, and Zp ( _T ) = 2
55. Reference numerals 32 to 35 are arrows indicating the focusing drive direction, and 36 is an arrow indicating the magnification drive direction.

6 and 7 are both a flow chart showing the operation sequence of the embodiment shown in FIG. 1, FIG. 6 shows the focusing operation, and FIG. 7 shows the interruption operation of the object distance display. There is. As described above, the operation shown in FIG. 6 is activated at any time according to the intention of the camera user, while the operation shown in FIG.
Since the interruption operation shown in the figure is activated at a constant cycle by the timer provided in the subject distance display unit 14, there is a time-series (timing) relationship between both the operations shown in FIGS. 6 and 7. nothing. The configurations of both of the above flowcharts will be described together in the following description of the operation, and will be omitted here.

Now, the operation of this embodiment configured as described above will be described. First, the focusing operation will be described with reference to the flowchart of FIG.

When a focus switch (not shown) provided in the focus instructing section 15 in FIG. 1 is turned on by the camera user, the focus instructing section 15 measures the distance to the subject and calculates the correction amount Daf, Further, the MDR indicating the driving direction of the focusing lens groups 2a and 2b is determined and the focus control unit 12 is notified of the end of the operation. This time point is the "AF calculation end" in FIG. In this case, the subject distance is
It is assumed to be 1.2 m. The current positions of the focusing lens groups 2a and 2b are the intersection points 27 in FIG. In the "reading correction amount" and the next "reading driving direction", the focus control unit 12 sets MDR = 1 as the driving direction from the focus instruction unit 15 as shown in FIG.
As af, the difference between S ₀ and S ∞ = 0 in FIG. 5, that is, Sx = S ₀
Read the data corresponding to. In the next "To the near side?",
Since MDR = 1, the flow branches to YES, the maximum feed amount calculation unit 9 reads Zp = Zp ( ₁ ) at “Zp read”, and the maximum feed amount Fpx is calculated by the formula (10) or (at “Max feed amount calculation”). It is calculated by the formula 8). According to FIG. 5, in this case Fpx = S ₀ . In the next "Dfc clear", the output Dfc of the focus counter 6 used in the previous operation is cleared to zero. Then, the focus correction calculation unit 11 reads "Sx = S∞ = 0" by "Read Sx", and knows that the focusing lens groups 2a and 2b are now at the ∞ position. Then, in “in movable range?”, 0 <Sx <Fp is set as a movable range, and a check of Sx <Fpx or Sx = 0 is performed on the condition of the driving direction MDR. That is, in the present case, Sx = 0
Therefore, it is out of the movable range, but YES because the driving direction is MDR = 1, which indicates driving toward the closest position.
Branch to. In the next "focusing lens driving", MDR = 1 in the direction by one step focusing lens unit 2a, the focus control unit 12 the focus motor M _F to drive 2b is controlled. In the next "Read Dfc", the output Dfc of the focus counter 6 is read, and in "Drive end?", It is checked whether Dfc = Daf. In this case, the process branches to NO and returns to "Sx read" again. . In FIG. 5, it means that only one step has moved from the intersection 27 in the direction of the arrow 32. "Sx read" The above operation
Repeat until Dfc = Daf (this repeating loop is called "lens drive loop"). Therefore,
In FIG. 5, the intersection 27 is the starting point, and the arrows 32, 33, and 34 move in this order.
Reach That is, Dfc = Daf. At this time, it is not possible to specify which operation in the lens drive loop is being executed, but after a very short time (several tens of microseconds), "driving end?" Is reached, the flow branches to YES and the focusing operation is ended at END. .
In the case of this example, since the end point (intersection point 30) is the same as the limit position on the close side of the movable range, Sx = Fpx may occur, and there may be a case where “NO within the movable range?” Branches to NO and reaches END.

Next, the interruption operation of the subject distance display shown in FIG. 7 will be described. First, when "Zp read", the maximum feed amount calculation unit 9 sets Zp =
The Zp ( ₁ ) is read, and the Zp ( ₁ ) is substituted into the formula (10) or the formula (8) in the “Fpx calculation” to output the maximum feed amount Fpx. Then, the "Sx read" causes the focus correction calculation unit 11 to Sx = S ₀
Read and receive the above Fpx in “Display Address Calculation” (2
The value of the display function DS1 ( _T ) is calculated by the formula 3) and the display address (dot address 26) is output as the display output (DS). Upon receiving this display output (DS), the subject distance display unit 14 asks the above-mentioned display function DS1 ( _T ) in the next "in display range?"
Check if is within the range of dot address 26, and branch to YES. Note that this check operation is for responding to an unexpected situation, and cannot be out of the above display range in design. Then, if the flow branches to NO, "display address correction" is performed. If the distance is out of the above range on the closest position side, set DS1 ( _T ) = 15, and if it is off on the ∞ position side, set DS1 ( _T ) = 0. . That is, dot address 26
Address [15] and address [0].

Proceed to the next "2 dot display?"
Controls the subject distance display of FIG. 4, and the meaning of "2-dot display" will be described here. As can be seen from FIG. 2, the distance between the focus curves 17 to 22 is wide on the tele side and narrow on the wide side.

That is, the change range of Sx on the tele side is 0 to 255, and if this is divided into, for example, 32 sections (hereinafter, this is referred to as "divided section"
The change of Sx on the wide side is limited to about 5 sections at most. Further, in f = 50 mm in FIG. 2, the range is about 10 sections. On the other hand, display dot 25 in Fig. 4
And since there are 16 dot addresses 26, the resolution of the above divided section (32 sections) on the telephoto side is the dot address.
There is twice the resolution of 26, and the divided section (5
The resolution of (section) is only about 0.3 times the resolution of dot address 26. In this way, a range close to the wide side to compensate for the decrease in resolution of the divided section on the wide side,
For example, in the range of f = 35 to 49 mm, "two-dot display" is an attempt to light two adjacent dots of the display dot 25 at the same time as the subject distance display.

Now, returning to the flowchart of FIG. 7, assuming that the focal length f is 50 mm or more now, the conditional branch of “2 dot display?” Branches to NO, and the next “display dot lighting” already lights up and holds. The existing dot is extinguished, the display dot 25a in FIG. 4 is kept lit, and the subject distance display is updated.

By the way, if you branch YES to "Display 2 dots?",
Execute "Multiple display addresses". That is, the display function
Since DS1 ( _T ) is an integer in the range of 0 to 15, for example DS1 (
_{If T} ) = 0, the dot address 26 to be turned on is [0],
If [1] and DS1 ( _T ) = 4, the dot address 26 is set to [4] and [5], and the dot address indicated by the display function and the address obtained by adding 1 to this are calculated and pluralized. The above is the interrupt operation for displaying the subject distance.

Now, the relationship between the focusing operation and the interrupting operation described above will be described. In Fig. 5, the tele side, that is, Zp = Z
The driving time required to drive the focusing lens groups 2a and 2b from the infinity position to the closest position on p ( _T ) is, for example, 1
In seconds, the drive time on Zp = Zp ( ₁ ) is about 0.3 seconds. If Zp ( ₁ ) corresponds to f = 50 mm as described above, the number of divided sections on Zp ( ₁ ) is about 10. 16/10 = 1.6 sections, and 1 section has 8 steps, so 1.6 x 8 = 12.8 steps, and the change in Sx is 1
The dot address 26 of the display dot 25 is switched every 2 to 13 steps. On the other hand, the driving time on Zp ( ₁ ) was about 0.3 seconds, and since there are 80 steps in 10 sections, the time required for one step is 0.3 / 80≈3.
If the number of steps for which the dot address 26 is switched is 8 ms and 13 steps are set, the switching cycle for switching the dot address 26
3.8ms x 13 = 49.4ms, which is about 50ms. Therefore, by setting the starting period of the timer in the subject distance display section 14 for activating the interruption operation of the subject distance display shown in FIG. 7 to be smaller (shorter) than 50 ms, the focusing lens groups 2a and 2b can be set to the ones shown in FIG. In the process from the start point 27 to the end point 30, the display dot 25 in FIG. 4 changes its display from 25f so that the lighting state moves continuously to the 25a side, and finally the display dot 25a.
The focusing operation ends when is turned on and is held. On the contrary, if the startup cycle is longer than 50 ms (long), the lighting state of the display dot 25f moves to the 25a side intermittently (discontinuously) in the above process, and the display dot 25a is the same as above.
The focusing operation ends with the button lit and held. But,
Since the timer is always operating, even after the focusing operation is completed, the display dot 25a is updated such that the old display is once erased and the new display is turned on again at each activation cycle. Therefore, in this embodiment, the update time from when the old display is erased to when the new display is lit is set to be shorter than 0.05 to 0.1 seconds which is generally regarded as the afterimage time of the human eye. The flickering of the display does not practically occur regardless of the length of the startup cycle of. Therefore, since no flicker occurs, the activation cycle can be set long. On the other hand, as described above, during the interruption operation, the other units are not in operation. Therefore, for example, in the focusing operation described above, the smaller the number of interruption operations, the higher the efficiency of the focusing operation. In other words, in the present embodiment, the change in display is set to a sufficiently long activation period that the user does not feel unnatural, so that the focusing operation described above and the zooming operation described later can be speeded up. .

Now, suppose the subject changes and the distance changes to 1.5m.
Then, when the above-described focusing operation is again activated by the focus switch in the focus instruction section 15, the process from START to "to the near side?" Is the same as above in Fig. 6, and this condition branch branches to NO and "Dfc The above-mentioned lens drive loop is executed via “clear”. Focusing lens group 2
In FIG. 5, a and 2b are driven step by step in the direction of arrow 35 starting from the intersection point 30 and ending the focusing operation with the intersection point 29 as the end point. Therefore, as the object distance display, the display dot 25a which was the old display disappears and the display dot 25b is turned on as the new display, and this state is maintained (strictly, it is continuously updated as described above).

Next, the operation when the scaling operation is activated from this state will be described.

First, the magnification increasing operation of shifting from the wide side to the tele side will be described. When the up switch 13a in FIG. 1 is pressed, the drive direction determination unit 13c outputs a start signal (STR) including information on the magnification changing direction. . Maximum feeding amount calculation unit 9 is Z
Receives PM8 output (Zp), performs A / D conversion, and calculates proportional constant calculation unit 10
Receives the output (Sx) of FPM7 and A / D converts it,
For example, it is assumed that Zp ( ₁ ) and S ₁ are shown in the figure. The scaling control unit 16 rotates the scaling motor Mz in the direction of increasing the magnification. Then, the zoom lens group 2 moves, and the output of ZPM8 (Z
p) also changes as shown by arrow 36a. However, the first group lens 2a so FPM7 focus motor M _F is not operating
The distance between the second lens group 2b and the second lens group 2b changes according to a predetermined cam operation, but the focusing lens group is held at a fixed position and does not change due to the zooming operation.

Each time the variable power lens group 2 moves by a predetermined amount (for example, 8 steps), the focusing lens groups 2a and 2b move in the direction of the arrow 36b.
Are driven by the focus control unit 12. That is (1
0) equation (11) and (16) the focus correction operation unit 11 by the formula calculates the correction amount Dfp, the focus control unit 12 rotates the focusing motor M _F. The scaling motor Mz continues to rotate even during the correction operation by the focus motor M _F. Further, the focus control unit 12 successively compares the output Dfc of the focus counter 6 with the correction amount Dfp and when Dfc = Dfp, that is, when the arrow 36b reaches the focusing curve 19 in FIG. It stops the focus motor M _F terminates one cycle of magnification up operation. Thereafter, the same operation is repeated, and when viewed macroscopically, the movement moves along the focusing curve 21 as shown by the arrow 36. If the up switch 13a is turned off at the time when Zp = Zp ( ₂ ) is reached, the zooming operation ends at the intersection 31. Therefore, in the interrupt operation of the subject distance display which is activated for the first time after this scaling operation is completed, the dot address 26 is changed from Zp = Zp ( ₂ ) and Sx = S ₁ ′ by the display function DS1 ( _T ). Calculate the address [14]. As described above, the subject distance display is updated for the purpose of explaining the operation. However, not only Zp ( _T ) in FIG. 5 but also Zp ( ₁ ), Zp ( ₂ ) ... Focusing lens group 2 even at the position corresponding to the distance
As long as a, 2b (value of Sx) is on the focus curve 19 of 1,5 m, the display dot 25b is lit and the focal length display does not change.

Also, paying attention to the movements of the focusing lens groups 2a and 2b during the zooming operation, the out-of-focus state and the in-focus state are repeated every eight steps of the zooming drive, and this is displayed. Since it is meaningless to the person, it is more preferable not to update the subject distance display during the scaling operation.
However, the above update may be performed if there is any need.

As described above, in this embodiment, since the activation cycle for activating the interrupt operation of the subject distance display can be set long,
There is an advantage that the number of interruptions to operations other than the object distance display, such as focusing operation and zooming operation, is small, and the operations described above can be speeded up accordingly.

Further, the update time required to update the display dots 25 is set shorter than the afterimage time of the human eye, so that there is no flicker on the subject distance indicator with the movement of the focusing lenses 2a, 2b. There is also.

The lighting of the display dots 25 is divided into cases according to the range of the focal length, and in a certain range on the wide side, 2 dots are displayed (simultaneous lighting of 2 dots), so that the roughness of resolution (lowness) and the roughness of the display are small. Can be associated with.

Further, the condition of equal movement in the conventional zoom lens is removed, and the change of the focus position at each subject distance is configured to be the expression (7), that is, the focus curve 17 to FIG. Since it is configured to be 22, there is an advantage that the moving amount of the focusing lens groups 2a and 2b on the wide side does not become unnecessarily large. Therefore, there is an advantage that the lens outer diameter can be made as small as possible. In addition, apparently (in terms of use), there is an advantage that no focus shift (blurring) occurs even if a zoom operation is performed after focusing once, similarly to a conventional zoom lens.

In addition, since the change in the object distance scale due to the magnification change operation that occurs when the conditions for equal amount movement are removed is corrected by the proportional calculation of equation (23), the magnification is changed once the focus is adjusted with a simple configuration. It is possible to prevent the subject distance display from changing even if the operation is performed, and in this respect, there is no difference from the usability of the conventional zoom lens.

Further, in the correction calculation for correcting the object distance display and the focusing in the flowchart of FIG. 7, (10)
Formulas can be shared, and proportional constants of each can be calculated (11)
The equations and the equations (23) are also similar calculation equations with different coefficients, that is, there is an advantage that both the focusing correction and the subject distance display can be performed by the same calculation content.

It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

For example, the object distance display interrupt operation may be applied to the focal length display.

Further, the focus switch in the focus instruction section 15 may be a shutter button (release switch).

Further, the subject distance display is not limited to the dot display shown in FIG. 4, but may be configured to display the number of the subject distance.

Further, the equation (10) and the like are not limited to calculations, and data may be stored in the CPU or ROM.

Further, Dfc may be a software counter using a RAM memory instead of the focus counter 6.

(E) Effects As described above in detail, according to the present invention, the structure is simple and the manufacturing cost can be reduced, and the size and weight can be reduced. On the other hand, the imaging position shift and the subject caused by the zooming operation can be achieved. In a camera equipped with a varifocal lens that has the drawback of complicating the distance display, it is possible to correct the imaging position deviation as quickly and automatically as possible.
It is possible to provide a subject distance display device of a camera including a varifocal lens that can display a subject distance that is easy to visually recognize with a simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of a subject distance display device of a camera equipped with a varifocal lens according to the present invention, and FIG. 2 shows characteristics of the device of the present invention shown in FIG. In the graph shown, the amount Sx of extension of the focusing lens group corresponding to the focal length f and the subject distance D to be set
FIG. 3 is a diagram showing the relationship with respect to each subject distance, and FIG. 3 omits a part of FIG. 2 for explaining the calculation principle of the focus correction calculation unit in the embodiment shown in FIG. The diagram, Fig. 4,
FIG. 5 is a diagram conceptually showing the configuration of the object distance display,
6 is a diagram for explaining the operation of the embodiment shown in FIG.
FIG. 7 and FIG. 7 are flowcharts showing the operation sequence of the embodiment shown in FIG. 1, respectively. FIG. 6 shows the focusing operation, and FIG. 7 shows the interruption operation of the object distance display. 1 ... Optical axis, 2 ... Variable magnification lens group, 2a to 2e ... 1st group to 5th group, 3 ... Film surface, 4 ... Variable magnification drive section, 5 ... Focus drive section, 6 ... Focus counter 7 ... Focusing group lens position detector (FPM), 8 ... Variable lens group position detector (ZPM), 9 ... Maximum extension amount calculation unit, 10 ... Proportional constant calculation unit 11 ... Focusing Correction calculation section, 12 ... Focus control section, 13 ... Starting means, 13a ... Magnification up switch (up switch), 13b ... Magnification down switch (down switch), 13c ... Driving direction determination section, 14 ... object distance display unit, 15 ...... focus instruction unit, 16 ...... magnification change control unit, Mz ...... zooming motor, M _F ...... focus motor, + V ...... supply, 24 ...... numerals and symbols, 25 ...... display Dots, 25a to 25f …… Display dots, 26 …… Dot address.

Claims (4)

(57) [Claims] 1. A variable power optical system comprising a variable power lens group and a focusing lens group arranged on the same optical axis, wherein the object distance and the amount of extension of the focusing lens group in the optical axis direction. In a camera provided with a varifocal lens having a relationship that varies depending on a magnification position within a variable power range, a focusing drive unit that drives the focusing lens unit, and a variable power drive unit that drives the variable lens unit,
A zoom lens group position detecting means for detecting a position of the zoom lens group on the optical axis, a focus lens group position detecting means for detecting a position of the focusing lens group on the optical axis, and Focusing correction calculating means for receiving the outputs of the focusing lens group position detecting means and the zooming lens group position detecting means, and calculating the extension correction amount of the focusing lens group associated with the zooming operation, and the focusing correction calculating means. A focus control means for receiving the output and controlling the focus lens group through the focus drive means, an output of the focus lens group position detection means and the variable magnification lens position detection means, and a subject at predetermined time intervals. An object distance display device for a camera provided with a varifocal lens, comprising: object distance display means for updating the distance display content and holding the display content during the predetermined time interval. 2. The subject distance display means has an output corresponding to the amount of extension from infinity to the closest position as Fpx, an output of the variable power lens group position detection means as Zp, and a constant peculiar to the lens of the variable power optical system as Cp. _{When 1} , C ₂ , C ₃ , A subject distance display device for a camera provided with a varifocal lens according to claim 1, further comprising a maximum feed amount calculation means for executing a calculation by the following formula. 3. The focusing control means has a proportional constant computing means, and the proportional constant computing means outputs the output thereof as Cfp, and the output of the focusing lens group position detecting means immediately before the start of the operation of the magnification driving means. S (i), when the output of the maximum payout amount calculation means based on the output of the variable power lens group position detection means immediately before the start of the operation of the variable power drive means is Fp (i), A subject distance display device for a camera equipped with the varifocal lens according to claim 1, wherein the subject distance display device executes a calculation according to the following formula. 4. The focus correction calculation means is adapted to perform the focusing operation at a predetermined time interval after the operation of the variable power drive means or when a change in the output from the variable power lens group position detection means reaches a predetermined amount. The output of the focus correction calculation means is Dfp, the output of the proportional constant calculation means is Cfp, the output of the zoom lens group position detection means at the time of correction is Zp (e), and the focus is obtained just before the start of the above operation. When the output of the lens position detecting means is S (i) and the constants peculiar to the variable power optical system lens are C ₁ , C ₂ and C ₃ , respectively, A subject distance display device for a camera equipped with the varifocal lens according to claim 1, wherein the subject distance display device executes a calculation according to the following formula.