JPH0545179A - Zoom encoder - Google Patents

Abstract

PURPOSE:To obtain a non-touch type zoom encoder capable of high resolution, low cost, saving space and outputting absolute values. CONSTITUTION:A pattern 1 consisting of a convex part 1a fitted with a high reflection material and a concave part 1b formed of a light shield material is provided on the outer surface of cum ring in a zoom optical system. By projecting the light from a photoreflector 30 to this and detecting the intensity of the reflecting light, the zoom position is obtained. Since a means to memorize the position of sinking body of the zoom and wide end position, the zoom position is obtained based on the memorized values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom encoder, and more particularly to a zoom encoder for detecting the rotational position of a cam frame which performs a zooming operation by rotation.

[0002]

2. Description of the Related Art A conventional zoom value detecting device is provided with a code plate of several bits in order to detect the rotational position of a cam ring which is a cam frame which performs a zooming operation by rotation, and a brush is brought into contact with the code plate to make a cam ring. The rotation position of is detected.

The rotational position detecting device using this code plate is
Although there is an advantage that the rotational position of the cam ring can be detected as bit information from the code plate, it also has the following drawbacks.

(1) The manufacturing cost of the code plate is high.

(2) Since the bit information is obtained by the contact between the code plate and the brush, conduction failure occurs over time due to oxidation of the surface of the code plate and the brush surface.

(3) Insufficient contact pressure and continuity defects due to surface abrasion etc. occur over time.

[0007] Of the above-mentioned defects, the defects that occur over time are very serious problems because they are almost always shipped from the factory and used by the user.

[0008]

Therefore, it is conceivable to replace the conventional contact-type zoom encoder with a non-contact-type zoom encoder to drastically solve the problems (2) and (3).

As a first proposal, an optical non-contact type switch element using a photo reflector or an electromagnetic non-contact type switch element using a MR element is used for each bit of the contact type zoom encoder contact piece, and a non-contact type is used. It is conceivable to use a type absolute encoder. However, such a method has another problem that the space is larger and the cost is higher than that of the conventional contact encoder. This other problem becomes more remarkable as the number of divisions of the zoom encoder increases, and the practical use limit is a few bits at most.

On the other hand, with current zoom cameras,
32 divisions (5 bits) for 70mm 2x zoom,
64 divisions (6 with 6x zoom from 35mm to 105mm)
Bit) is needed, and if the number of divisions is reduced below this,
There is also a problem that the zoom correction accuracy of exposure and focus is affected, and the smoothness of zoom driving is lost.

As described above, it is difficult to make the conventional zoom encoder as it is as a non-contact type in view of the space for the number of divisions and the cost.

Therefore, as a second proposal, the pulse output from an optical pulse generator which generates pulses in response to the rotation of the zoom cam ring is counted up or down depending on the rotation direction of the zoom cam ring. Therefore, a means for obtaining the zoom value can be considered. According to this means, it is possible to provide a high-resolution zoom encoder with only one photo interrupter.

However, since the above-mentioned rotational position detecting device is a so-called relative value encoder and not an absolute value encoder using a digital code as in the prior art, there are the following problems in principle.

[1] The output state of the pulse generator is H, L
If noise occurs due to motor startup or the like near the switching point, the erroneous pulse may be output. Therefore, while driving the zoom several times, the miscount due to the above false pulse is accumulated,
As a result, exposure and focus accuracy may be seriously adversely affected.

[2] Since the output of the pulse generator is normally monitored only during zoom driving, for example, when the user pushes or pulls the lens barrel while not monitoring, a change in zoom value is detected. Cannot be performed, and as a result, exposure and focus accuracy may be seriously adversely affected.

Therefore, the present invention has been made in view of the above-mentioned various problems, and a large number of divisions can be taken, and the cost is low.
It is an object of the present invention to provide an optical non-contact type zoom encoder that is space-saving and can obtain an absolute value output.

[0017]

A zoom encoder according to the present invention is a zoom encoder for detecting the amount of rotation of a cam frame for changing the focal length of a photographing lens by rotating about the optical axis. A pattern in which the amount of reflection or transmission of light changes according to the rotation of the cam frame, a light projection member that projects light toward this pattern, and the light reflected or transmitted from the pattern. The light receiving means for receiving light and the storage means for storing the output of the light receiving means in the focal length state which is the reference of the photographing lens are provided, and the focal length is based on the output of the light receiving means and the storage means. It is characterized by determining.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. FIG. 2 is a perspective view showing the outer appearance of a zoom lens barrel having the zoom encoder according to the first embodiment of the present invention. The zoom lens 11 has a zoom cam ring 12 on the outer periphery thereof. Helical cam grooves 13 and 14 for moving the zoom lens 11 in the optical axis direction are formed on the outer peripheral surface. And this cam groove 1
Guide pins 16 and 17 which are planted in the front lens group frame and the rear lens group frame (not shown) are fitted to the lenses 3 and 14, respectively.

Since the sector gear 19 provided on the outer peripheral surface of the cam ring 12 near the end surface on the mount side meshes with the motor gear 18 through a reduction gear mechanism that reduces and transmits the rotation of the motor 15, the zoom motor 15 is When driven in the normal and reverse directions, the cam ring 12 rotates in the normal and reverse directions. As a result, the front lens group frame and the rear lens group frame are guided by the zoom cam grooves 13 and 14 to move in the optical axis direction, and the relative distance between them is changed, so that the zooming operation of the zoom optical system is performed.

Further, patterns 1 and 2 to be described later are provided near the mount-side end surface of the cam ring 12. Further, second and first photo reflectors 30 and 31 for reading the pattern surfaces of the patterns 1 and 2 are provided.

FIG. 1 is a development view of the pattern 1 in which the amount of light reflected changes in accordance with the rotation of the cam ring 12, and is a convex portion 1a to which a highly reflective member is attached and a concave portion 1b made of a light shielding member.
And the area ratio between the convex portion 1a and the concave portion 1b is changed in accordance with the movement or rotation of the cam ring 12 in the outer peripheral direction.

On the outside of the outer peripheral surface of the cam rig 12, the second photo reflector 3 fixed to a fixing member (not shown) is provided.
0 is provided. This second photo reflector 30
By projecting a slit-shaped light pattern on the pattern 1 formed on the outer peripheral surface of the cam ring 12 and receiving the reflected light, as shown in FIG. 3, linearly corresponding to the change in zoom position. It is designed to generate a photoreflector output that changes to.

FIG. 4 is a specific block configuration diagram of an electric component portion including a peripheral portion of the zoom encoder according to the present embodiment.
This electric component section includes a zoom motor 15 for driving the cam ring 12 and a motor drive circuit 2 for driving the motor 15.
1 and a CPU 22 for controlling the motor drive circuit 21
The second photoreflector 30 that detects the zoom position from the pattern on the cam ring 12 and the first photoreflector 31 that detects and outputs the collapsed position of the cam ring 12 form a main part. ..

The first and second photo reflectors 31,
The output of the CPU 30 is the input port P.P. R. 1 and
A / D input port P. R. 2 to the cam ring 1 based on the above output.
Two rotational positions can be obtained. The CPU 2
2, a power switch 23, which is a main switch of the camera, a zoom up switch 24 for transmitting a zoom up operation, a zoom down switch 25 for transmitting a zoom down operation, and the like, and a ratio calculation table described later as an external storage device. E ² PROMs 26 storing the above information are connected respectively. The operation of the first embodiment thus constructed will be described with reference to FIGS.

FIG. 5 shows a first photo-reflector 31 and a second photo-reflector 3 obtained corresponding to the zoom position.
In the figure showing the output waveform with 0, the second photo reflector 3
The output of 0 changes linearly according to the change of the zoom position as described in FIG. On the other hand, the output of the first reflector 31 maintains the L level when the zoom lens is extended from the retracted position, and changes from L to H when retracted to the retracted position.

When the power switch 23 of the camera is turned off or the camera is left without any operation for a predetermined time from the start of photographing, the CPU 22 detects this and inevitably causes the zoom lens to retract. Set to to stop the camera operation. In this case, the retracted state is detected by the first photo reflector 31.

FIG. 6 is a flow chart of the operation of setting the retracted position, in which the CPU 22 uses the motor drive circuit 2
1 while giving a command to the reverse rotation of the zoom motor 15 to rotate the motor 15 backward (step S1), the CPU 22
Input port P. R. It waits for 1 to change from L to H (step S2). The input port P. R. When 1 becomes H, the CPU 22 gives a motor stop command to the motor drive circuit 21 to stop the rotation of the motor (step S
3) Return.

Next, when the power switch 23 is turned on, C
The PU 22 sets the taking lens from the retracted state to the wide end of 35 mm (here, it is assumed that the zoom lens is 35 mm to 80 mm). This operation will be described with reference to the flowchart of FIG. R. 2, the output of the second photo-reflector 30 corresponding to the retracted position (hereinafter referred to as P.R.2 output) is A / D converted (step S11), and the value is stored in the CPU 22. Stored in RAM.

Next, the A / D conversion value corresponding to the retracted position is multiplied by the ratio of "35 mm wide end output / retracted position output" previously written in the E ² PROM to obtain A corresponding to the 35 mm wide end. Calculate the / D conversion value (step S1
2).

Next, the CPU 22 gives a normal rotation command of the zoom motor 15 to the motor drive circuit 21 to cause the motor 1 to rotate.
5 is rotated in the normal direction (step S13), the A / D converted P.P. R. The two outputs are continuously monitored (steps S14 and S15). P. R. When the 2-output A / D converted value matches the wide end A / D converted value, the zoom motor 15 is stopped (step S1).
6) Return. As a result, the photographing lens is set to the position corresponding to the wide end of 35 mm from the retracted state.

Next, the photographer operates the zoom-up switch 24.
Alternatively, the zoom down switch 25 (see FIG. 4 for both)
Consider a case of operating to drive the zoom lens. Figure 8
Is a flowchart of the zoom-up operation. First, when the zoom-up switch 24 is turned on, the CPU 22 detects it and first calculates the A / D conversion value corresponding to the tele end position according to the flow shown in FIG. Yes (step S2
1).

Next, as in the case of the wide end in FIG. 7, the "80" previously written in the E ² PROM is written.
mm tele end output / collapse position output ”is multiplied by the collapse position output to calculate an A / D conversion value corresponding to the 80 mm tele end position. And P. R. The two outputs are A / D converted (step S22), and if the A / D converted value is larger than the tele end A / D converted value (step S23), the zoom motor 15
If the rotation is normal (step S24) or less, the zoom motor 15 is stopped (step S26).

After the normal rotation of the zoom motor, it is detected whether or not the zoom-up switch 24 is continuously turned on (step S25). R. 2 Continue to monitor the output. On the other hand, if it is off, the zoom motor 15 is immediately stopped (step S26), and the P.P.
R. The two outputs are A / D-converted (step S27), the currently set zoom value information is obtained from the value (step S28), and the process returns. In this case, the above step S2
The zoom value information obtained in 8 is as in the following formula.

[0034]

[Equation 1]

Similarly, when the zoom down switch 25 is turned on, the zoom value information is obtained in the flow of FIG. In FIG. 9, the same steps as those in FIG. 8 are shown by the same step numbers, and different flows are shown by adding A after the same step numbers. In this case, the tele end is set to the wide end and the forward rotation is set. Since the reverse rotation and the zoom up are replaced with the zoom down, respectively, the description thereof will be omitted. In this way, the photographer can set the zoom lens to any focal length.

FIG. 10 is a development view of a pattern in the modified example of the first embodiment, which is formed by a seal which gradually changes the gradation of the light reflectance in place of the pattern 1 shown in FIG. The pattern 1A is attached to the outer peripheral surface of the cam ring 12. The photoreflector output waveform at this time is as shown in FIG.

FIG. 12 is an external view of a zoom lens barrel according to another modification of the first embodiment, in which the cam ring 12 is replaced by the second photo reflector 30 and the pattern 1 shown in FIG. 2 as the light amount detecting means. The difference lies in that a light shielding member 32 that makes one rotation in synchronization with one rotation and a photo interrupter 33 in which a light emitting portion and a light receiving portion are arranged to face each other with a passage of the light shielding member 32 interposed therebetween. Except for this point, the first
Since there is no difference from the embodiment, the same members are designated by the same reference numerals and the description thereof is omitted.

FIG. 13 is a view for explaining the positional relationship between the light shielding member 32 and the photo interrupter 33. The light shielding member 3 is shown in FIG.
By detecting the ratio of the cam-circular light-shielding portion 32b whose length in the radial direction gradually increases on 2 and the remaining light-transmitting portion 32b by the light emitting / receiving portion 33a of the photo interrupter 33,
A photo interrupter output that linearly changes with respect to the zoom position as shown in FIG. 14 is obtained.

The output of photoreflectors, photointerrupters, etc. usually changes by 10% by temperature, and also deteriorates by 10% by aging. Furthermore, the output changes about 20 to 30% depending on the consumption of the battery and the temperature characteristics of the battery.

However, according to the means shown in the first embodiment and each modification, the output at each zoom value is determined with reference to the output near the retracted position of the zoom, and the principle against the above fluctuation It is possible to configure a highly reliable zoom encoder that is not affected by physical influences.

Therefore, it is possible to provide a non-contact type zoom encoder which is not affected by the temperature change peculiar to the non-contact type, particularly the optical type, and the fluctuation of the power supply voltage.

In the above-described first embodiment and each modification, the A / D conversion value of the output of the second photoreflector 30 or the photointerrupter 33 is used as it is for controlling the zoom motor 15, but it serves as a reference for the taking lens. The A / D converted value at the lens position, that is, the retracted position is stored, and every time the photoreflector output at the arbitrary zoom position is A / D converted, the A / D converted value corresponding to the retracted position is stored. Calculate the ratio. Then, zoom value detection and zoom lens control may be performed based on this ratio, which will be described below as a second embodiment of the present invention.

In this case, in the first embodiment and its modification, the first photo reflector 3 is used to detect the retracted position.
Although the switch element of No. 1 was used, it can be abolished also in this second embodiment.

FIG. 15 is a perspective view showing the appearance of a zoom lens barrel equipped with a zoom encoder according to the second embodiment of the present invention. The difference from FIG. 2 is the structure of the reflection pattern surface of pattern 1. At the retracted position, the output of the photoreflector 30 suddenly changes from the maximum to the minimum as shown in FIG. 16, and this is called pattern 1B. In addition, the pattern 2 and the first photo reflector 3
1 and are abolished. Except for these points, there is no difference from FIG. 2 described above, so that the same constituent members are given the same reference numerals and the description thereof is omitted.

The operation will be described below in the same manner as in the first embodiment. The power switch 23 of the camera is turned off, or left unattended for a predetermined time from the start of photographing. In this case, the CPU detects this, inevitably sets the zoom lens in the retracted state, and stops the camera operation, as in the first embodiment.

The setting to the retracted state will be described with reference to the flow chart of FIG. 17. The CPU 22 gives a reverse rotation command of the zoom motor 15 to the motor drive circuit 21 and reverses the motor 15 (step S1) while the photo reflector 30 is rotated. It continues to determine whether the A / D conversion output change exceeds a predetermined value (steps S31 to S34), and when it exceeds, a stop command is given to the motor drive circuit to stop the rotation of the motor (step S3).

Next, when the power switch 23 is turned on, C
PU22 sets the taking lens from the retracted state to the wide end of 35 mm. The lens driving from the retracted position to the position corresponding to the wide end will be described with reference to the flowchart shown in FIG. 18. First, the zoom motor is normally rotated (step S1).
3), L → of the photoreflector output in FIG.
Detect H. Since this operation is the reverse of the set state H → L to the retracted state in FIG. 17, the same step number S3
1 to S34.

In this way, when escape from the collapsed state,
The CPU 22 performs A / D conversion on the output of the photo reflector 30, and stores the value as AD0 in the RAM of the CPU 22 (step S35). All subsequent A / D converted values are divided by the contents AD0 of the RAM, and the zoom value is determined based on that value. The value at the 35mm wide end is E ² PR in advance.
Since it is written in the OM 26, the normal rotation of the zoom motor 15 is performed until the value is reached (steps S36 to S36).
38), and at the same time, the motor 15 is stopped (step S16) and the process returns.

That is, every time the zoom motor 15 is driven, the A / D conversion value is converted into the A / D conversion value (AD) near the retracted position.
Zoom value information can be obtained by obtaining the calculated value R divided by 0). Incidentally, the E ² PROM 26 stores R values of 0.95 and 0.25 at the wide end and the tele end, respectively. Therefore, zoom up switch 2
4. If R at the zoom position set by turning on / off the zoom down switch 25 is R ', the currently set zoom value is given by the following equation.

[0050]

[Equation 2]

The second embodiment is the same as the first embodiment in that it is not affected by the temperature change and power supply voltage change peculiar to the optical encoder, but the pattern and the photoreflector form one set. Since this is sufficient, cost reduction can be expected compared to the first embodiment.

[0052]

As described above, according to the present invention, the cam frame is provided with a pattern whose light reflection amount or light transmission amount changes in accordance with the rotation of the cam frame, and the pattern is received by the light projection member and the light receiving member. Means for storing the output of the light receiving means in the focal length state that is the reference of the photographing lens in the storage means, and determining the focal length based on the output of the storage means and the output of the light receiving means. As a result, a large number of divisions can be taken,
In addition, the remarkable effects of low cost, space saving, that is, small size and absolute value output can be obtained.

[Brief description of drawings]

FIG. 1 is a development view of a pattern in which the amount of light reflection changes according to the rotation of a cam frame.

FIG. 2 is a perspective view of a zoom lens barrel equipped with a zoom encoder according to the first embodiment of the present invention.

FIG. 3 is a diagram in which a photoreflector output is plotted with respect to a zoom position in FIG.

FIG. 4 is a specific block configuration diagram of an electric component section in the first embodiment.

FIG. 5 is a diagram showing a photo reflector output waveform in the first embodiment.

FIG. 6 is a flowchart of a setting operation to a retracted position in the first embodiment.

FIG. 7 is a flowchart of movement to the wide end position in the first embodiment.

FIG. 8 is a flowchart of a zoom-up operation according to the first embodiment.

FIG. 9 is a flowchart of a zoom-down operation according to the first embodiment.

FIG. 10 is a pattern development view of a modified example of the first embodiment.

11 is a diagram in which the photoreflector output is plotted with respect to the zoom position in FIG.

FIG. 12 is a perspective view of a zoom lens barrel according to another modification of the first embodiment.

FIG. 13 is a diagram for explaining the positional relationship between the light blocking member and the photo interrupter in FIG.

14 is a diagram in which the photo interrupter output is plotted with respect to the zoom position in FIG.

FIG. 15 is a perspective view of a zoom lens barrel equipped with a zoom encoder according to a second embodiment of the present invention.

FIG. 16 is a diagram in which a photoreflector output is plotted with respect to a zoom position in the second embodiment.

FIG. 17 is a flowchart of a setting operation to a retracted position in the second embodiment.

FIG. 18 is a flowchart of movement to the wide end in the second embodiment.

[Explanation of symbols]

1, 1A, 1B, 2 ... Pattern 12 …………………… Cam ring (cam frame) 22 ……………… CPU (storage means) 30, 31 ……… Photoreflector (light projection) Member and light receiving means) 33 Photo interrupter (light projection member and light receiving means)

Claims (1)

[Claims] 1. A zoom encoder for detecting the amount of rotation of a cam frame for changing the focal length of a photographing lens by rotating about an optical axis, wherein the zoom encoder is provided on the cam frame and responds to the rotation of the cam frame. A pattern in which the amount of reflection or transmission of light changes, a light projection member that projects light toward this pattern, a light receiving unit that receives reflected light or transmitted light from the pattern, and serves as a reference for the taking lens. A zoom encoder, comprising: a storage unit that stores the output of the light receiving unit in a focal length state, wherein the focal length is determined based on the outputs of the light receiving unit and the storage unit.