JP2763200B2 - Zoom lens - 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, and more particularly to a zoom lens for correcting and moving a lens group having a focusing function with respect to a temperature at the time of photographing.

[0002]

2. Description of the Related Art Recently, zoom lenses are often used in compact cameras of the lens shutter type. For this reason, zoom lenses are also required to be compact and lightweight, and glass lenses have become more prevalent than glass lenses. The advantages of the plastic lens are that the aspherical surface can be molded in the same manner as the spherical surface, is suitable for mass production, and is lightweight. On the other hand, as a disadvantage, the change in the refractive index with temperature is about 100 times that of a glass lens, which is very large. Therefore,
It is becoming important to take measures against focal length movement in plastic lenses due to temperature changes. As a countermeasure for this, conventionally, a specific lens interval is changed according to a temperature change by using a material having a different expansion coefficient from the material of the plastic lens for a spacer holding the lens interval, so that the focus of the lens group in the temperature change is changed. Measures to prevent the movement of the distance and the material of the lens group consisting of the positive lens and the negative lens, for example, using a material such as methyl methacrylate for the positive lens,
Using materials such as acrylonitrile for the negative lens, offset the fluctuation of the focal length due to the temperature change of these lenses,
Attempts have been made to prevent the focal length of the lens group from moving due to temperature changes.

[0003]

However, when the above-described measures are taken, it is necessary to form the spacer and the lens material for maintaining the lens interval with a special material, and such a special material is difficult to form. However, there is a disadvantage that the cost is high. In addition, there is a countermeasure to configure a lens group by combining a plastic lens with a glass lens using a glass lens as a lens that has a large influence of focal length movement due to temperature change. This contradicts the tendency for compact cameras to occupy a large weight.

The present invention has been made to solve the above problems .
The focus of the zoom lens caused by temperature changes
Miniaturization and low cost
The compact, built-in distance measuring device
It is an object of the present invention to provide a suitable zoom lens incorporated in a camera or the like .

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and has a built-in distance measuring device.
Camera can be made smaller and lighter
In order not to hinder quantification and cost reduction,
The basic configuration of the zoom lens can be adjusted by zooming.
Obtained from a first lens group moving in the optical axis direction and a distance measuring device
Combination of subject distance data and position of first lens group
Positioning in the optical axis direction based on the result calculated
And a second lens group composed of
You.

Further, according to the present invention, a reference temperature set in advance is set.
A temperature sensor for detecting a temperature change with respect to
Storing the focal lengths of the first and second lens groups at the temperature;
Storage means for storing the second lens group at the time of photographing.
When performing positioning in the optical axis direction, from the storage means
The read focal lengths of the first and second lens groups are
Each lens after correction obtained by correcting each according to the degree change
The focal length of the group, the position of the first lens group in the optical axis direction,
The second lens is calculated based on the data of the subject distance.
Position of the lens group, or the first lens group and the second lens
The optimal position of the group is determined.

[0007] In addition to the temperature sensor,
Use a humidity sensor to detect humidity changes,
The storage means includes first and second levels for the reference temperature and the reference humidity.
If you store the focal length of the lens group,
It is also possible to add correction corresponding to humidity changes without
Temperature and humidity change, the zoom lens
This makes it possible to maintain good precision of the printing.

[0008]

FIG. 1 shows a lens barrel of a zoom lens according to an embodiment of the present invention. The zoom lens according to this embodiment is of a rear focus type in which a lens group following the variator lens group has a focusing function.
The zoom lens has a two-group configuration including a front lens group 20 composed of five plastic lenses and a rear lens group 21 composed of three plastic lenses. It is a zoom lens that we have planned. The front lens group 20, which is a variator lens, is fixed to the movable barrel 25 by a well-known bayonet connection or the like. A rear lens group 21, which is a compensator lens having a focusing function, has a movable barrel 25 behind the front lens group 20.
And is incorporated in a rear lens group frame 29 via a rear lens group frame 28 fixed to the lens group.

The structure of the zoom lens barrel includes a fixed barrel 23 integrally formed with the camera body, an intermediate barrel 24 which is helicoidally coupled inside the fixed barrel 23, and a helicoidally coupled inside the intermediate barrel 24. And a movable cylinder 25. The camera body integrally formed with the fixed cylinder 23 has a wall 2 forming a film patrone chamber.
In this embodiment, the size of the camera is reduced compared to a conventional camera having a structure in which the camera body and the fixed cylinder are separate members because the 3c and the film feeding gear are integrally provided. I have. Reference numeral 22 denotes a front cover that covers the front surface of the camera body, and reference numeral 26 denotes a movable cylinder 2.
5 is a shutter device incorporated in the shutter device 5.

The forward / backward movement of the frame of the rear lens group 29 is based on the female helicoid 28a formed on the inner peripheral surface of the rear lens frame base 28 and the male helicoid 2 formed on the outer peripheral surface of the rear lens group frame 29.
9a is screwed, and the operation is performed according to the leads of these heicoids. At the valley of the male helicoid 29a, a gear portion 29d projecting from the valley is formed. The driving of a rear lens driving motor 26a built in the shutter device 26 is
b, 26c, 26d, and 26e. Therefore, the rear group lens frame 29 is rotated by the driving of the rear group lens driving motor 26a, and advances and retreats in the direction of the optical axis P according to the lead of the male helicoid 29a. Note that reference numeral 26f
Reference numeral denotes a motor rotation amount detecting device such as a rotary encoder arranged concentrically with the rotor of the focusing lens motor 26a. Reference numeral 26g denotes a reflective photo-interrupter fixed to the fixed cylinder 25, and the like.
With 6g, the origin position at the retracted position of the rear lens group frame 29 is detected.

A male helicoid 25a is provided on the outer peripheral surface of the movable cylinder 25, and a female helicoid 24a provided in the intermediate cylinder 24 is screwed to the male helicoid 25a. The movable cylinder 25 linearly advances and retreats along a straight guide member 35 fitted in a groove 25b provided on the inner peripheral surface of the movable cylinder 25 according to the lead of the male helicoid 25a.
Reference numeral 25e denotes a cover frame attached to the front end side of the movable barrel 25, and reference numeral 25d denotes a lens window provided on the cover frame 25e. A window 25f is provided in the cover frame 25e, and a temperature sensor 30 is disposed behind the window 25f. The temperature sensor 30 uses a known thermistor type temperature sensor. Reference numeral 31 denotes a humidity sensor. The humidity sensor 31 is a known bulk ceramic humidity sensor. This bulk type ceramic humidity sensor detects humidity by utilizing a change in electric resistance value due to moisture attached to pores of a metal oxide ceramic.

The intermediate cylinder 24 has a fixed cylinder 23
A male helicoid 24b screwed with a female helicoid 23a formed on the inner periphery of the cylinder is provided, and the intermediate cylinder 24 itself rotates to advance and retreat according to the lead of the male helicoid 24b. Further, a gear portion 24c is formed at a rear end side of the male helicoid 24b with a constant width in the optical axis P direction. The drive by the intermediate cylinder rotating mechanism is transmitted to the gear portion 24c. The intermediate cylinder rotating mechanism includes a lead screw 51, a two-stage gear 50, and a front lens drive motor 34, which are arranged outside the fixed cylinder 23 in parallel with the optical axis P. A bush 52 which advances and retreats in accordance with the lead is screwed into the lead screw 51, and a gear 51a is integrally formed on the front end side of the bush 52. The gear portion 24c is connected to the bush 52 through the opening 23b of the fixed cylinder 25.
An intermediate cylinder rotating gear 54 meshing with the gear portion 50b of the two-stage gear 50 is rotatably provided. The gear unit 50a of the two-stage gear 50 has a front group lens driving motor 34
The gear 50b has a length in the optical axis direction that allows the movement of the intermediate cylinder rotating gear 54. The leads of the lead screw 51 are formed so that the movement of the bush 52 is in the same phase as the advance and retreat of the intermediate cylinder 24.

When the front group lens driving motor 34 is driven, the driving of the motor 34 is transmitted to the intermediate cylinder rotating gear 54 via the gear portions 50a and 50b to rotate the intermediate cylinder 24. Also,
The driving of the front group lens driving motor 34 is performed by a gear unit 50.
a to the gear 51a. Accordingly, the lead screw 51 rotates, and the bush 52 moves according to the lead. Similarly to the movement of the bush 52, the intermediate cylinder rotating gear 54 rotates and moves, and the meshing portion between the intermediate cylinder rotating gear 54 and the gear portion 24c also moves in the same phase as the intermediate cylinder 24 advances and retreats. Further, since one end of the linear guide member 35 is fixed to the bush 52 at the rear end side of the intermediate cylinder rotating gear 54, the linear guide member 35 also moves in the same phase as the intermediate cylinder 24 advances and retreats. Note that reference numeral 33 is
It is a position detector such as a potentiometer, and the slider provided on the bush 52 detects the amount of movement of the front group lens 20 in response to the movement of the bush 52.

A flexible board 36 is inserted between the straight guide member 35 and the movable barrel 25. The flexible board 36 electrically connects the shutter device 26 and the like to a control circuit and the like in the camera body.
The flexible substrate 36 is provided with the linear guide member 35.
In response to the movement of the body, it is highly flexible and easily bends.

Such a zoom lens barrel is incorporated in a compact camera as shown in FIG. In addition,
Reference numeral 10 denotes a shutter button, reference numeral 11 denotes a main switch, reference numeral 12 denotes a zoom operation member, and reference numeral 13a denotes a photometry window. A photometric device 13 described below is built in the depth of the photometric window 13a. Reference numerals 14a and 14b denote distance measuring windows incorporating an IR filter that cuts visible light and transmits only infrared light, and a well-known infrared light emitting diode (IRED) and position detecting diode (PS) are located behind these windows.
D) is built in. Further, reference numeral 15 denotes a liquid crystal display unit.

FIG. 3 is a schematic diagram showing an electrical configuration of the camera shown in FIG. A switch 10a is turned on when the shutter button is half-pressed. Reference numeral 11 denotes the main switch described above. When the main switch 11 shown in FIG. 2 is operated to the ON side, the main switch 11 shown in FIG. 3 is turned on, and the above-described zoom lens barrel is extended from the retracted position to the wide position. It is. Code 12
Is a zoom operation member described above.
When the zoom operation member 12 shown in FIG. 3 is operated to the W side, that is, the wide side, the zoom operation member 12 shown in FIG.
Connected to the zoom operation member 12
Is operated to the T side, that is, the tele side, and is connected to the contact b. When the camera user finishes operating the zoom operation member 12, the zoom operation member 12 automatically becomes the neutral position. Reference numeral 13b denotes a photometric circuit built in the photometric device 13, reference numeral 14c denotes a distance measuring circuit built in the distance measuring device 14, and a comparison circuit that compares a signal obtained from the temperature sensor 30 and the humidity sensor 31 with a reference voltage. An analog signal output from these circuits and the above-described reflection type photointerrupter 26g, rotary echoer 26f, and potentiometer 33 is taken into a CPU 63 via an interface 62 including an A / D converter.

The CPU 63 performs processing in accordance with a sequence program stored in the ROM 70 in advance based on the fetched signal, and stores the obtained result in the RAM 64.
Then, the stored data is read out as necessary, and a control signal corresponding to the data is read out via the interface 62 through a driver IC 66 for controlling the rear group lens driving motor 26a or a driver for controlling the front group lens driving motor 34. The IC 67, a flash circuit 60 including a well-known booster circuit and the like, a shutter control circuit 26h built in the shutter device 26, a film feeding control circuit 61 for controlling film feeding, and the like are sent to the camera to control the camera as a whole. .

FIG. 4 is a flowchart showing a sequence program used for focusing among the sequence programs stored in the ROM 70. The feature of this sequence program is that when calculating the optimum position of the rear lens group frame 29 based on the detection values obtained from the distance measuring device 14 and the potentiometer 33, the temperature sensor 30 via the comparison circuit 32, The point is that the calculation is performed in consideration of the temperature detected from the humidity sensor 31 and the humidity data.

In the ROM 65, focal length data of the front lens group 20 at the reference temperature and humidity and focal length data of the rear lens group 21 at the reference temperature and humidity are stored as predetermined data. The optimum position of the rear lens group frame 29 is calculated in accordance with the difference between the reference temperature, the reference humidity, the temperature detected during photographing, and the humidity data.

Next, the operation of the above configuration will be briefly described with reference to FIG. When the main switch 11 is turned on in the retracted position, the zoom lens barrel is extended to the wide position. Thereafter, when the zoom operation member 12 is operated, the front group lens 20 moves accordingly, and the rear group lens frame 29 advances and retreats according to the movement of the front group lens 20.
The movement of the rear lens group frame 29 prevents the focus of the zoom lens from moving along with the movement of the front lens group 20, and constantly moves to a standby position at an intermediate position within the focus adjustment range. Note that the CPU 63 controls the zoom operation member 12.
Is detected from the potentiometer 33 according to the operation, and the obtained data is temporarily stored in the R.
It is stored in AM64.

Thereafter, when the release button 10 is half-pressed as shown in FIG. 4, the switch 10a is turned on. As a result, the CPU 63 starts detection of photometry, distance measurement, temperature, and humidity, and captures data of temperature, humidity, subject luminance, and subject distance from the comparison circuit 32, the photometry circuit 13b, and the distance measurement device 14. These data are temporarily stored in RAM
64.

Next, the CPU 63 calculates the optimum position of the rear lens group frame 29 based on the data stored in the RAM 64. The equations used at this time are described below using the symbols shown in FIG. The symbols shown in FIG. 6 will be described. f ₁ : Focal length of the front group lens 20 taking into account temperature and humidity at the time of photographing f ₂ : Focal length of the rear group lens 21 taking into account temperature and humidity at the time of photographing f ₃ : Focal length of the zoom lens L: Subject distance a: Distance between the front principal point of the front group lens 20 and the object A: Distance between the rear principal point of the front group lens 20 and the imaging point of the front group lens 20 b: Front side of the rear group lens 21 Distance between the principal point and the imaging point of the front group lens 20 B: Distance between the rear principal point of the rear group lens 21 and the film surface (back focus) H ₁ : Front principal point of the front group lens 20 and rear principal Distance between points H ₂ : Distance between front principal point and rear principal point of rear lens group 21 D: Distance between rear principal point of front lens group 20 and front principal point of rear lens group 21 D ₃ : Photographing Distance between the rear principal point of front lens group 20 and the front principal point of rear lens group 21 when the distance is infinity In _{this, f 1, f 2, H} 1, H 2 are constants, f _3, L is an input variable.

[0023]

(Equation 1)

Here, the equations are used to determine the focal length of the front group lens 20 taking into account the temperature and humidity during photography and the focal length of the rear group lens 21 taking into account the temperature and humidity during photography. The symbols that were used are explained. X: front group lens 20 at reference temperature and reference humidity
Focal length Y: rear group lens 21 at reference temperature and reference humidity
C ₁ : Temperature characteristic coefficient of front group lens 20 c ₂ : Temperature characteristic coefficient of rear group lens 21 e ₁ : Humidity characteristic coefficient of front group lens 20 e ₂ : Humidity characteristic coefficient of rear group lens 21 T: Reference Difference between temperature and temperature detected at the time of imaging W: Difference between reference humidity and humidity detected at the time of imaging Here, X, Y, c ₁ , c ₂ , e ₁ , and e ₂ are constants. The expression (3) in the expression (1) holds when L is at infinity.

By the way, the reference temperature and the reference humidity are, for example, based on the temperature and the humidity at the time of adjusting the focal position of the zoom lens at the time of manufacturing, the focal length of the zoom lens is fixed, and as shown in FIG. When the object is placed on the surface and adjusted so that the object is in focus on the film surface, the focal lengths of the front and rear lenses 20 and 21, that is, the front group at the reference temperature and the reference humidity The focal length of the lens 20 and the focal length of the rear group lens 21 at the reference temperature and the reference humidity are obtained by actual measurement. As is well known, the focal length of the lens due to changes in temperature and humidity is, for example, the refractive index of the lens when the detected temperature is low relative to the reference temperature and when the detected humidity is high relative to the reference humidity. Tends to increase the focal length.

By deriving an equation for calculating the distance between the rear principal point of the front lens group 20 and the front principal point of the rear lens group 21 from these equations, the following equation is obtained.

[0027]

(Equation 2)

The expression (2) in the expression (2) indicates the distance between the rear principal point of the rear lens group 21 and the film surface, which are satisfied when L is at infinity.

As described above, when calculated by the above-described equation, the front group is based on both the difference between the humidity detected at the time of photographing and the reference humidity and the difference between the temperature detected at the time of photographing and the reference temperature. The optimum position of the rear lens group frame 29 corresponding to the movement amount of the lens 20 is calculated. Then switch 1
When 0b is turned on, the CPU 63 moves the rear lens group frame 29 to the optimum position, and opens and closes the shutter after the movement is completed. After the shutter is opened and closed, the rear lens group frame 29 is moved to the standby position, and the next operation is awaited.

In this embodiment, the amount of movement of the front lens group 20 is determined based on both the difference between the humidity detected at the time of photographing and the reference humidity and the difference between the temperature detected at the time of photographing and the reference temperature. This is an example in which the optimum position of the corresponding rear group lens frame 29 is calculated. However, the present invention is not limited to this, and corresponds to the movement amount of the front group lens 20 based on the difference between the temperature detected during shooting and the reference temperature. Calculating the optimum position of the rear group lens frame 29, and further, the optimum position of the rear group lens frame 29 corresponding to the moving amount of the front group lens 20 based on the difference between the humidity detected at the time of photographing and the reference humidity. It is needless to say that it is possible to use an example of calculating.

[0031]

As described above, according to the present invention ,
Is the first lens that moves in the optical axis direction by the zooming operation.
Lens group, subject distance data obtained from the distance measuring device and the first
The result calculated by the combination with the position of the lens group
A second lens group for positioning in the optical axis direction based on
Temperature change of a two-unit zoom lens
The second lens group or the first and second lens groups
And positioning of the second lens group during shooting.
Therefore, without adding a special lens group for correction,
Good focus accuracy of the zoom lens is maintained with the two-unit configuration.
Will be able to carry it. In addition, changes in temperature and humidity
Correction corresponding to the shift
The operability is good because it is performed automatically, especially in a distance measuring device.
Is very effective when applied to compact cameras with built-in
is there.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of the structure of a zoom lens according to the present invention.

FIG. 2 is a perspective view showing a camera using a zoom lens.

FIG. 3 is a block diagram showing an electrical outline of the camera.

FIG. 4 is a flowchart illustrating a focus method of a zoom lens.

FIG. 5 is an optical path diagram schematically showing a zoom lens.

[Explanation of symbols]

 Reference Signs List 14 distance measuring device 20 front group lens 21 rear group lens 25 movable barrel 26a rear group lens driving motor 28 rear group lens frame 29 rear group lens frame 30 temperature sensor 31 humidity sensor 32 comparison circuit 33 potentiometer 34 front group lens driving Motor 63 CPU 64 RAM 65 ROM 70 ROM

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-61-133912 (JP, A) JP-A-63-92314 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 7/08 G02B 7/02

Claims (2)

(57) [Claims] A distance measuring device for measuring a subject distance;
This is a zoom lens that is used in a built-in camera.
The first laser beam moves in the optical axis direction by the zooming operation.
Lens group and the optical axis direction according to the amount of movement of the first lens group.
The shutter button, and respond to the pressing operation of the shutter button.
In response, the subject distance data obtained from the distance measuring device
And the position of the first lens group
Position in the optical axis direction during shooting based on the
The second lens group consisting of the second lens group where the positioning is performed
In Murenzu temperature for detecting a temperature change with respect to a reference temperature set in advance
Sensor and first and second lenses at the reference temperature
Storage means for storing the focal length of the group
When positioning the second lens group in the optical axis direction,
Of the first and second lens groups read from the storage means
The focal length was obtained by correcting each according to the temperature change.
The corrected focal length of each lens group and the optical axis of the first lens group
Calculation based on the position in the direction and the data of the subject distance
The optimal position of the second lens group or the first lens
A zoom lens , wherein optimal positions of the group and the second lens group are determined . 2. A built-in distance measuring device for measuring a subject distance.
This is a zoom lens that is used in a built-in camera.
The first laser beam moves in the optical axis direction by the zooming operation.
Lens group and the optical axis direction according to the amount of movement of the first lens group.
The shutter button, and respond to the pressing operation of the shutter button.
In response, the subject distance data obtained from the distance measuring device
And the position of the first lens group
Position in the optical axis direction during shooting based on the
The second lens group consisting of the second lens group where the positioning is performed
In Murenzu temperature for detecting a temperature change with respect to a reference temperature set in advance
Sensor and humidity change with respect to a preset reference humidity
Humidity sensor to detect, and the reference temperature and reference humidity
Storing the focal lengths of the first and second lens groups in the camera
Means is provided so that the second lens group can be positioned in the optical axis direction during photographing.
When performing the positioning, read from the storage means.
The focal lengths of the first and second lens groups are changed by the temperature change and
Each corrected lens obtained by correcting according to the humidity change
Of the lens group and the position of the first lens group in the optical axis direction
And a second calculation based on the data of the subject distance.
Optimal position of the lens group or the first lens group and the second lens
The optimum position of the lens group is determined.
The zoom lens according to 1 .