JPH11108694A - Optical encoder and lens barrel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical encoder capable of maintaining a fixed detection precision regardless of an attaching error and secular change. SOLUTION: This optical encoder is provided with a light-emitting means 1, a first scale 2 for forming measurement light irradiated by the light-emitting means 1 to bright and dark stripe light? by a refracting action, a second scale 3 for partially transmitting the bright and dark stripe light, a light receiving means 4 for photoelectrically converting the bright and dark stripe light transmitted through the second scale 3, a first cylinder 5 arranged while being provided with the light-emitting means 1 or the light receiving means 4 inside and a second cylinder 6 arranged while being provided with the first cylinder 5 inside. In this case, at least one of the two cylinders 5 and 6 is turnable with the cylindrical axis as a center, the first scale 2 is formed on the cylindrical surface of the cylinder closer to the light-emitting means 1 of the two cylinders 5 and 6 and the second scale 3 is formed on the cylindrical surface of the cylinder closer to the light receiving means 4 of the two cylinders 5 and 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical encoder, and more particularly to an optical encoder having a scale formed in a cylindrical surface and a lens barrel having the encoder.

[0002]

2. Description of the Related Art In general, a linear encoder and a rotary encoder are known as optical encoders for length measurement and angle measurement. Normally, the optical encoder has a configuration in which two scales, and a light source and a light receiving element are arranged with the scales interposed therebetween.

[0003] Of the two scales, a scale attached to a moving or rotating body as an object to be measured and moving integrally with the object to be measured is called a main scale. The fixed scale is called an index scale.

On the main scale and the index scale, gratings (slits) are engraved at regular intervals. When the main scale moves relative to the index scale, the amount of measurement light passing through both scales changes. I do. The amount of movement of the main scale, that is, the amount of displacement of the measured object is detected from the change in the amount of light. As one example using an optical encoder, an optical encoder used for autofocus control of a camera will be described with reference to FIG. The hatching in the figure is given to identify a fixed cylinder 60 and an encoder holding member 72 described later.

In FIG. 11, a camera body 51 and a lens barrel 52 are connected to a camera body side bayonet mount 5.
3a, detachably coupled by a lens barrel side bayonet mount 53b. A plurality of camera body side electrical contacts 54a and a plurality of lens barrel side electrical contacts 54b are provided near the bayonet mount 53a.
When the lens barrel 52 and the lens barrel 52 are coupled, the electrical contacts 54a and 54b come into contact with each other, and an electrical signal such as lens information is transmitted between the camera body 51 and the lens barrel 52.

A CPU 55 for controlling the operation of the camera body 51 and the lens barrel 52 is provided inside the camera body 51.
And a control circuit 56 for performing lens operation control such as AF control and zoom control in accordance with an instruction from the CPU 55.
The control circuit 56 is connected to the lens barrel 52 via electrical contacts 54a and 54b. Further, a power supply 57 is mounted inside the camera body 51, and power is supplied to the lens barrel 52 via a control circuit 56. The power supply and signal transmission are performed by, for example, a flexible printed circuit board.

On the other hand, a photographing lens 58 is arranged in the lens barrel 52. Normally, the photographing lens 58 is composed of a plurality of lenses and a plurality of groups, but for simplification of description, only one lens is shown here.

The photographing lens 58 is fixedly held by a moving frame 59, and the moving frame 59 is slidably fitted on the inner periphery of a fixed cylinder 60. A rotating cylinder 61 is rotatably fitted on the outer periphery of the fixed cylinder 60, and a gear portion 62 is disposed on a part of the outer periphery of the rotating cylinder 61. A motor 63 is provided inside the lens barrel 52, and a gear 64 fixed to a rotating shaft of the motor 63 meshes with the gear portion 62 to transmit a driving force to rotate the rotating barrel 61.

On the other hand, a pin 65 is erected on the moving frame 59, and a rectilinear groove 66 provided in the fixed cylinder 60 is
Are arranged so as to be engaged with the cam groove 67 provided in the first groove. Thus, when the rotating cylinder 61 is rotated by the motor 63, the photographing lens 58 moves in the lens optical axis direction together with the moving frame 59. An encoder for detecting the amount of movement of the photographing lens 58 in the optical axis direction is provided inside the lens barrel 52. This encoder is
Light emitting element 68 (for example, an LED that emits infrared light)
A main scale 69 provided perpendicular to the side surface (cylindrical surface) of the rotary cylinder 61; an index scale 70 provided perpendicular to the cylindrical surface of the fixed cylinder 60; A silicon photodiode that outputs a photocurrent according to the amount of light.

[0010] As shown in FIG.
Is an annular or circular arc, and the lattice of the main scale 69 and the index scale 70 is a radial lattice such that the extension of the lattice passes through the center of the circular ring or arc and the distance between the lattices increases toward the outside of the diameter. It has a shape.
The plane of the grating is configured to be included in a plane perpendicular to the rotation axis (the optical axis of the imaging lens 58).

The light emitting element 68 and the light receiving element 71 are fixed to an encoder holding member 72, and the encoder holding member 72 is an L-shaped plate 73 attached to the fixed cylinder 60.
Are fixed by screws 74. In such a configuration, the gear 63 and the rotating cylinder 6 are driven by the motor 63.
When 1 rotates, the moving frame 59 and the imaging lens 58 move in the optical axis direction along the rectilinear groove 66 cut by the fixed cylinder 60. The encoder detects the amount of movement of the photographing lens 58 by detecting the amount of rotation of the rotating cylinder 61 (the amount of rotation of the main scale 69).

By the way, in such an optical encoder, when a displacement occurs between the main scale 69 and the index scale 70, the output signal fluctuates, and an error occurs in the detection of the movement amount. Therefore, the main scale 69
It is necessary to keep the interval between the index scale 70 and the index scale 70 (hereinafter, referred to as “gap”) at a constant interval. The movement of the main scale 69 in the optical axis direction is restricted by an engaging portion between a pin 80 set on the fixed cylinder 60 and a circumferential groove 81 cut in the circumferential direction of the rotary cylinder 61. Usually, this portion is used to maintain the moving amount of the photographing lens 58 with high accuracy.
Although the pin 80 is movable, the backlash in the optical axis direction of the main scale 69 is suppressed to a necessary minimum. However, in practice, slight fluctuations in the gap occur because there is some backlash.
Further, the components interposed between the main scale 69 and the index scale 70 are the rotating cylinder 6
1, the pin 80, the fixed cylinder 60, the plate 73, and the encoder holding member 72. There are five points. When all the dimensional tolerances and mounting accuracy of each component are added together, the accuracy of the gap when assembled without adjustment is equal to the encoder. Exceeds the allowable range required to function. For this reason, the plate 73
And the encoder holding member 72 can be moved in the direction of the optical axis.
Thus, an adjustment step of fixing the two and adjusting the gap is required.

[0013] As another conventional example, an encoder in which the step of adjusting the gap is omitted is disclosed in Japanese Patent Application Laid-Open No. HEI 3-19782.
No. 0 proposes this. In this encoder,
The main scale and the index scale are molded integrally with the engraved part of the lattice and the protrusion protruding from this lattice part using an acrylic material, and the protrusion of the index scale is formed on the protrusion of the main scale with a spring. When the main scale is moved, the protrusions slide against each other when the main scale is moved. Thereby, the gap can be always maintained at a constant interval.

[0014]

However, in the two encoders described above, the main scale has a radial grid shape in which the grid interval becomes wider toward the outside of the diameter. If the rotation axis is displaced from the center of the radial grating of the main scale, the amplitude of the output signal from the light receiving element decreases, and the detection accuracy decreases. Hereinafter, such a shift is referred to as a “shift”. This shift is caused by the eccentricity at the time of mounting the main scale and the mounting error of the index scale.

This shift will be described with reference to the drawings. FIG. 13A shows a state without a shift, and FIG.
Indicates that there is a shift. A hatched portion indicates a portion through which light does not pass, and a portion without hatching indicates a portion through which light passes. FIGS. 13A and 13B show a state where the amount of light transmitted through the main scale 69 and the index scale 70 is the largest (that is, the area of a portion through which the light passes is the largest). FIG. 13 (2) in comparison with FIG. 13 (1)
In the state (1), the area of a portion through which light passes becomes small. Since the index scale 70 is shifted upward,
There is no change in the amount of light at the center of the grating, but at the periphery the grating is tilted, which limits the transmission part,
The amount of transmitted light decreases. As a result, the amplitude of the output signal from the light receiving element may be reduced, and the detection accuracy of the movement amount by the encoder may be reduced, and the measurement may not be possible.

In the encoder disclosed in Japanese Patent Application Laid-Open No. 3-197820, the gap can be accurately maintained at a constant interval. However, since the main scale and the index scale are slid, the wear caused by the abrasion of the sliding surface is caused. Changes over time occurred, and the detection accuracy deteriorated. Further, since the load on the drive source due to the frictional force increases, a larger drive force is required.

In order to solve the above-mentioned problems, the inventions according to the first and second aspects of the present invention provide an optical encoder capable of maintaining a constant detection accuracy irrespective of a mounting error or a change with time. The purpose is to do. Also,
It is an object of the present invention to provide an optical encoder that can eliminate the influence of a decrease in detection accuracy due to warpage or undulation of a scale.

Another object of the present invention is to provide an optical encoder which can be realized with a simple configuration. Another object of the present invention is to provide a lens barrel equipped with the above-described optical encoder.

[0019]

FIG. 1 is a block diagram showing the principle of the first aspect of the present invention.

According to the first aspect of the present invention, the light emitting means 1 for irradiating the measuring light, and the measuring light irradiated by the light emitting means 1 is partially transmitted to form a light-dark stripe light or a refraction action. A second scale 3 arranged at a position where the light and dark fringe light is incident and partially transmitting the light and dark fringe light; A light receiving means 4 for photoelectrically converting light and dark fringe light transmitted through the scale 3 of the first embodiment, a first cylinder 5 having the light emitting means 1 or the light receiving means 4 disposed therein, A second cylinder 6 that includes the cylinder 5 therein, at least one of the two cylinders is rotatable about its cylinder axis, and the first scale 2 is formed of the two cylinders. Light emitting means 1
The second scale 3 is formed in a cylindrical shape in a cylinder close to
Are characterized by being formed in a cylindrical shape in a cylinder close to the light receiving means 4 among the two cylinders.

According to a second aspect of the present invention, in the optical encoder according to the first aspect, the scale formed in the rotatable cylinder is curved in a cylindrical shape concentric with the cylinder. Features.

According to a third aspect of the present invention, in the optical encoder according to the first or second aspect, the first scale 2 main body is arranged in contact with a cylindrical surface of the cylinder close to the light emitting means 1. And an elastic member 7 for pressing the first scale 2 main body against the cylindrical surface. According to a fourth aspect of the present invention, in the optical encoder according to the first or second aspect, the second scale 3 main body is disposed in contact with a cylindrical surface of the cylinder close to the light receiving means 4, And an elastic member 7 for pressing the main body of the scale 3 to a cylindrical surface.

According to a fifth aspect of the present invention, in the optical encoder according to any one of the first to fourth aspects, the light emitting means 1 is an incoherent light source. According to a sixth aspect of the present invention, there is provided a lens barrel having the optical encoder according to any one of the first to fifth aspects, wherein the first cylinder and the second cylinder are provided.
Of the first cylinder 5 is disposed inside the lens barrel.
The taking lens 8 housed inside, the first cylinder 5 and the second
And a lens driving mechanism 9 for driving the photographing lens 8 in conjunction with the relative rotational movement of the lens 6 with respect to the cylinder 6.

(Operation) In the optical encoder according to the first aspect, the first cylinder 5 is disposed inside the second cylinder 6, and the light emitting means 1 or the light receiving means is provided inside the first cylinder 5. 4 are arranged. At least one of the first cylinder 5 and the second cylinder 6 is rotatable about its rotation axis. Further, the scale is formed on each of the two cylindrical surfaces so as to be curved in a cylindrical shape. Thereby, the relative rotation amount between the first cylinder 5 and the second cylinder 6 can be detected. Note that the first cylinder 5 and the second cylinder 6 do not need to be complete cylinders, and may function as an encoder without any part of the cylinder surface.

In the optical encoder according to the second aspect,
The scale formed in the rotatable cylinder is curved in a cylindrical surface concentric with the cylinder. Thus, even if the cylinder rotates, the light and dark stripe light always enters the light receiving means 4 properly. At this time, the scale does not need to be curved with the same curvature as the cylinder. In the optical encoder according to the third aspect, the first scale 2 main body is disposed in contact with the cylindrical surface of the cylinder close to the light emitting means 1, and in this state, the elastic member 7 is connected to the first scale. The two main bodies are crimped along a cylindrical surface.

In the optical encoder according to the fourth aspect,
The second scale 3 main body is arranged in contact with the cylindrical surface of the cylinder close to the light receiving means 4, and in this state, the elastic member 7
Presses the second scale 3 main body along the cylindrical surface. In the optical encoder according to the fifth aspect, the light emitting means 1 is an incoherent light source.

In the lens barrel according to the sixth aspect, since the relative rotational movement of the first cylinder 5 and the second cylinder 6 and the driving of the photographing lens 8 are interlocked, the relative rotation of the cylinders is reduced. The amount of movement of the taking lens 8 can be detected from the amount of rotation.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

As an embodiment of the optical encoder of the present invention, an example in which the optical encoder is used for a single-lens reflex camera with an autofocus function will be described. FIG.
FIG. 3 is a configuration diagram of the present embodiment, and FIG. 3 is a perspective view of the present embodiment. 2, a camera body 21 and a lens barrel 22 are connected to a camera body-side bayonet mount 23.
a, It is detachably connected by the lens barrel side bayonet mount 23b. Also, bayonet mount 23a
Are provided with a plurality of camera body-side electrical contacts 24a and a plurality of lens barrel-side electrical contacts 24b. When the camera body 21 and the lens barrel 22 are coupled to each other,
a and the electrical contact 24b come into contact with each other, and an electrical signal such as lens information is transmitted between the camera body 21 and the lens barrel 22.

A CPU 25 for controlling the operation of the camera body 21 and the lens barrel 22 is provided inside the camera body 21.
And a control circuit 26 that performs lens operation control such as AF control and zoom control in accordance with an instruction from the CPU 25. This control circuit 26 includes electrical contacts 24a and 24b
Through the lens barrel 22. A power supply 27 is mounted inside the camera body 21, and power is supplied to the lens barrel 22 via a control circuit 26.
The power supply and signal transmission are performed by, for example, a flexible printed circuit board.

On the other hand, a photographing lens 28 is arranged in the lens barrel 22. The photographing lens 28 is fixedly held by a moving frame 29, and the moving frame 29 is slidably fitted to the inner periphery of a fixed cylinder 30 (corresponding to the “first cylinder” in claim 1). I have. A rotating cylinder 31 (corresponding to the “second cylinder” according to claim 1) is rotatably fitted on the outer periphery of the fixed cylinder 30, and a gear portion is provided on a part of the outer periphery of the rotating cylinder 31. 32 are arranged. A motor 33 is provided inside the lens barrel 22, and a gear 34 fixed to a rotating shaft of the motor 33 meshes with a gear 32, and transmits a driving force to rotate the rotating barrel 31.

The movement of the rotary cylinder 31 in the optical axis direction is
The pin 45 set to 0 is restrained by engagement with a circumferential groove 46 cut in the circumferential direction of the rotary cylinder 31. On the other hand, a pin 35 is erected on the moving frame 29, and is arranged so as to engage with a rectilinear groove 36 provided on the fixed cylinder 30 and a cam groove 37 provided on the rotating cylinder 31. Thus, when the rotating barrel 31 is rotated by the motor 33, the photographing lens 28 moves along with the moving frame 29 along the straight groove 36 cut into the fixed barrel 30 in the lens optical axis direction.

The lens barrel 22 is provided with an encoder for detecting the amount of movement of the photographing lens 28 in the optical axis direction. The encoder includes a light emitting element 38 (for example, an LED that emits infrared light), a main scale 39 provided on the cylindrical surface of the rotary cylinder 31 (corresponding to the “first scale” according to claim 1), An index scale 40 (corresponding to the “second scale” according to claim 1) provided on the cylindrical surface of the fixed cylinder 30 and a light receiving element 41
(For example, a silicon photodiode).

The light-emitting element 38 has an optical axis
8 are arranged in a direction intersecting with the optical axis. The main scale 39 is curved at the curvature of the rotating cylinder 31 and has a cylindrical shape. Fixed cylinder 30 of main scale 39
A lattice portion 39a is formed on the side surface. This lattice part 3
9a is on a cylindrical surface whose axis is the optical axis of the taking lens 28, and lattices are engraved at equal intervals in the circumferential direction.

The index scale 40 is fixed to the fixed cylinder 30.
And has a cylindrical shape. A lattice portion 40a is formed on the surface of the index scale 40 on the rotating cylinder side. The grating portion 40a is on a cylindrical surface having the optical axis of the photographing lens 28 as a cylindrical axis, and is equally spaced from the main scale 39 in the circumferential direction.

Further, as shown in FIG.
1 has a contact surface 42 formed thereon, and the main scale 3
9 has a projection 43 formed thereon. Main scale 3
Reference numeral 9 is arranged such that the protrusion 43 is fitted to the contact surface 42. Further, the two leaf springs 44 (corresponding to the “elastic member” of claim 3) are provided with the light emitting element 3 of the rotating cylinder 31.
The leaf spring 44 presses both sides of the main scale 39 and presses against the contact surface 42.

There are various types of grid shapes engraved on the main scale 39 and the index scale 40 depending on the detection principle of the encoder. However, the present invention does not particularly limit the types of the grid shapes. However, here, the micro prism type encoder proposed in Japanese Patent Laid-Open No. 59-63517 is applied.

The configuration and detection principle of this microprism encoder will be described with reference to FIGS.
As shown in FIG. 5, the lattice portion 39a of the main scale 39
On the surface of the main scale 39 on the light receiving element 41 side, a microprism having a mountain-shaped cross section is formed.
As a method for forming the microprism, for example, a plastic material used for an optical component such as acrylic is molded and manufactured.

As a grid portion 40a of the index scale 40, a light transmitting portion and a light blocking portion (hatched portion in the figure) for transmitting light and the like are provided on the surface of the index scale 40 on the main scale 39 side. The pitch is formed at the same pitch as the pitch of the microprisms.
As a forming method, chromium is vapor-deposited on the surface of a glass or plastic scale material, or a film on which a pattern is printed is attached.
Further, in order to improve the resolution of the encoder more than the pitch of the scale, the upper and lower sides of the index scale 40 are formed by shifting the phase of the transmission section by 90 °.

As the light receiving element 41, 41a and 41b
Three light receiving elements are arranged, the light receiving element 41a receives light transmitted through the transmission part on the upper side of the index scale 40, and the light reception element 41b receives light transmitted through the transmission part on the lower side of the index scale 40, The light receiving signal is input to the waveform shaping circuit via each preamplifier. Next, the detection principle will be described. Light emitted from the light emitting element 38 enters the main scale 39 in a state close to a parallel light beam. As shown in FIG.
The light is refracted by the micro prism 9 and proceeds as indicated by hatching in the figure. Light is superimposed at a distance D from the main scale, and when the pitch of the scale is P, almost P /
Light portions and dark portions are alternately formed with a width of 2. Transmissive portions and light-shielding portions are formed alternately on the index scale 40 with a width of P / 2, and light entering the transmissive portion of the index scale 40 passes through the transmissive portion as it is and receives the light receiving element 41.
, And does not reach the light receiving element 41 due to reflection, scattering, or the like.

The light transmitted through the main scale 39 and the index scale 40 is received by the light receiving element 41, and the light receiving element 41 generates a photocurrent almost proportional to the light amount.
At this time, if the main scale 39 moves, the amount of light entering the transmitting portion of the index scale 40, that is, the amount of light reaching the light receiving element 41 changes in a triangular waveform, and the light receiving element 41 outputs a photocurrent proportional thereto. I do. However, in practice, the photocurrent signal output from the light receiving element 41 has a sine wave shape as shown in FIG. 6B because the light beam is not a perfect parallel light beam.

Two signals (FIGS. 7 (1) and (2)) from the light receiving elements 41a and 41b are amplified by preamplifiers, respectively.
In the waveform shaping circuit, it is converted into a pulse wave (see FIG. 7).
(3) (4)). The amount of rotation of the main scale 39 (that is, the amount of rotation of the rotary cylinder 31) is detected by the CPU 25 counting the number of generated pulse waves, and the amount of movement of the photographing lens 28 is measured.

Incidentally, the main scale 39 and the index scale 40 are actually provided with the rotary cylinder 3 as described above.
1. The fixed cylinder 30 is curved at the curvature of the cylindrical surface. However, the curvature for the scale pitch is small,
If it is enlarged, it can be regarded as a plane. by the way,
In general, the fixed barrel 30 of the lens barrel and the rotary barrel 31 with the cam groove 37 cut are fitted with strict precision by a method such as actual processing to secure the precision of the lens drive amount. In many cases, the fitting play in the plane perpendicular to the optical axis of the lens is originally reduced. Further, as shown in FIG. 2, in the encoder of the present embodiment, two parts interposed between the main scale 39 and the index scale 40 are the rotary cylinder 31 and the fixed cylinder 30, and the conventional cylinder shown in FIG. The number of parts can be reduced as compared with the encoder. Therefore, a gap generated due to mounting accuracy or the like can be reduced to a level that does not require adjustment.

When the main scale 39 is made of a plastic material, the main scale 39 is
It is desirable that the contact surface 42 be provided with the same diameter as that of the contact surface 42 provided in 1. However, in actuality, warpage or undulation occurs,
The diameter may not be the same as the contact surface 42. in this case,
The gap fluctuates during the rotation of the rotary cylinder 31 and causes a disturbance in the encoder output waveform. Therefore, as described above, the main scale 39 is urged to be pressed against the contact surface 42 by the leaf spring 44, and the scale is leveled by the elastic deformation of the main scale 39, thereby suppressing warpage and undulation. Thereby, the gap can be secured with a certain accuracy.

In this embodiment, the main scale 3
Ninth gratings (mountain-shaped microprisms) are parallel to the rotation axis of the rotating cylinder 31 and, like the grating of the conventional rotary encoder shown in FIG. There is no. This will be specifically described with reference to FIGS. 8A shows a pattern of a light and dark part by the index scale 40, and FIG. 8B shows a pattern of a light and dark part by the main scale 39. Note that hatched portions indicate portions through which light does not pass, and portions without hatching indicate portions through which light passes. Also, here, to simplify the explanation,
The pattern of the light and dark parts by the index scale 40 is a simple light and dark fringe pattern, and does not consider the 90 ° phase shift of the transmission part.

As shown in FIG. 8, the width of the light passing through the main scale 39 and the index scale 40 is kept at a constant interval. At this time, the main scale 39 and the index scale 40 relatively move in the optical axis direction due to the backlash in the thrust direction (the optical axis direction of the photographing lens 28) and the mounting accuracy of the rotary cylinder 31, as shown in FIG. May shift. However, even in this case, since the area of the portion transmitting the light of both scales does not change, the amplitude of the photocurrent does not decrease due to the shift, and the detection accuracy of the encoder can be prevented from decreasing. In other words, the required mounting accuracy in the shift direction can be reduced.

As described above, in the optical encoder of this embodiment, the main scale 39 is attached to the cylindrical surface of the rotary cylinder 31 in a cylindrical shape, and the index scale 40
Is fixed to the cylindrical surface of the fixed cylinder 30 in a cylindrical shape, so that it is possible to minimize deterioration in detection accuracy due to a mounting error of the scale or the like. The light emitting element 38,
The arrangement relation of the main scale 39, the index scale 40, and the light receiving element 41 is not limited to the arrangement relation of the present embodiment, but the main scale 39 is attached to the fixed cylinder 30, the index scale 40 is attached to the rotating cylinder 31, The light emitting element 38 may be arranged inside the fixed cylinder 30 and the light receiving element 41 may be arranged outside the rotating cylinder 31.

The leaf spring 44 used in the present embodiment is
The shape, material, arrangement position and quantity of the main scale 39 are not limited as long as the main scale 39 can be press-bonded to suppress warpage and undulation of the scale. Further, in the present embodiment, the main cylinder 39 is fitted by providing the contact surface 42 on the rotary cylinder 31, but the method of forming the scale is not limited thereto. For example, if the rotating cylinder 31 is made of a material that transmits light, the rotating cylinder 31 is
The main scale 39 may be directly attached to the surface of the rotary cylinder 31 and crimped without providing the main scale 39. If the rotary cylinder 31 is made of the same material as the main scale 39, the scale may be formed directly on the cylindrical surface.

The index scale 40 is not limited to the main scale 39, and may be pressure-bonded using a leaf spring 44. For example, as shown in FIG. 4B, a contact surface may be formed on the fixed cylinder 30, the index scale 40 may be fitted, and both sides may be pressed by the leaf springs 44. Also,
In the present embodiment, the main scale 39 is curved with the same curvature as the rotary cylinder 31, but is not limited thereto. As shown in FIG. 10A, the main scale 39 of the present embodiment is curved into a cylindrical surface having the same curvature as the rotating cylinder 31. However, for example, as shown in FIG. 10B, the main scale 39 may be provided along the outer periphery of the rotary cylinder 31. At this time, the main scale 39 has a cylindrical surface concentric with the rotary cylinder 31 and has a smaller curvature than the rotary cylinder 31. As a specific configuration, as shown in FIG. 10C, a projection is provided on the outside of the rotary cylinder 31, the main scale 39 is fitted thereto, pressed by a leaf spring 44, and the main scale 39 is provided outside the rotary cylinder 31. 39 are provided. In addition,
It is of course possible to provide the main scale 39 inside the rotary cylinder 31.

Further, similarly to the main scale 39, the pattern surface (lattice portion) of the index scale 40 may be arranged not on the outer peripheral surface of the fixed cylinder 30 but inside or outside the outer peripheral surface. By providing the main scale 39 outside or inside the cylindrical surface of the rotary cylinder 31, the degree of freedom in design is improved. That is, the optimal amount of the interval between the main scale 39 and the index scale 40 is determined by conditions such as the characteristics of the light source and the scale pitch, and it is important to maintain the interval. At this time, the main scale 39
Are arranged in a cylindrical surface concentric with the rotating cylinder 31, it is possible to realize an optimal scale interval in design.

[0051]

In the optical encoder according to the first and second aspects, the first scale and the second scale are formed in a cylindrical shape on the first cylinder and the second cylinder. In the conventional encoder, since the lattice shape was radial, there was a concern that the amplitude of the output signal would decrease due to a so-called shift.
In the present invention, it is possible to avoid a decrease in detection accuracy due to this shift.

Further, since the first scale and the second scale are not slid, there is no change with time due to wear of the sliding surface, and the detection accuracy can be maintained at a constant level even when used for a long time. . Furthermore, since there is no load due to sliding,
The driving source for the scale can be reduced in size. In the optical encoder according to the third and fourth aspects, the scale is pressed against the cylindrical surface by the elastic member, thereby suppressing and suppressing warpage or undulation generated in the scale. As a result, detection errors due to warpage and undulation can be avoided. In addition, even if there is some warpage or undulation, it can be used as an encoder, so that the yield of scale production can be improved.

In the optical encoder according to the fifth aspect,
The measurement light is partially transmitted or superimposed or condensed to create bright and dark fringe light, and the amount of movement is detected based on a change in the amount of light. Therefore, it is not necessary to use a coherent light source such as a laser diode having a laser resonator, and the encoder can be realized with a light source having a simple configuration such as a light emitting diode. Since the lens barrel according to the sixth aspect includes the optical encoder of the present invention, it is possible to avoid a decrease in detection accuracy due to a shift when detecting the moving amount of the photographing lens.

[Brief description of the drawings]

FIG. 1 is a principle block diagram of the invention according to claim 1;

FIG. 2 is a configuration diagram of the present embodiment.

FIG. 3 is a perspective view of the embodiment.

FIG. 4 is a diagram illustrating pressure bonding of a scale.

FIG. 5 is a configuration diagram of a microprism encoder.

FIG. 6 is a diagram illustrating the operation principle of a microprism encoder.

FIG. 7 is a diagram illustrating an output of a light receiving element.

FIG. 8 is a diagram (1) for explaining an influence of a shift according to the embodiment;

FIG. 9 is a diagram (2) for explaining the influence of the shift according to the embodiment;

FIG. 10 is a diagram illustrating another encoder.

FIG. 11 is a configuration diagram of a camera using a conventional encoder.

FIG. 12 is a configuration diagram of a conventional encoder.

FIG. 13 is a diagram illustrating the effect of a shift of a conventional encoder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light-emitting means 2 1st scale 3 2nd scale 4 Light-receiving means 5 1st cylinder 6 2nd cylinder 7 Elastic member 8 Photographing lens 9 Lens drive mechanism 21, 51 Camera body 22, 52 Lens barrel 22 23a, 23b, 53a, 53b Bayonet mount 24a, 24b, 54a, 54b Electrical contacts 25, 55 CPU 26, 56 Control circuit 27, 57 Power supply 28, 58 Shooting lens 29, 59 Moving frame 30, 60 Fixed cylinder 31, 61 Rotating cylinder 32, 62 Gear part 33, 63 Motor 34, 64 Gear 35, 65, 45, 80 Pin 36, 66 Straight groove 37, 67 Cam groove 38, 68 Light emitting element 39, 69 Main scale 39a, 40a Lattice part 40, 70 Index Scale 41, 71 Light receiving element 42 Contact surface 43 Projection 44 Leaf spring 46, 81 Circumference 72 encoder retaining member 73 plate 74 bis

Claims (6)

[Claims] 1. A light emitting means for irradiating a measuring light, and a measuring light irradiated by the light emitting means is partially transmitted to form bright and dark fringe light, or a bright and dark fringe by superposition or condensing by refraction. A first scale formed into light, a second scale disposed at a position where the light and dark fringe light is incident, and partially transmitting the light and dark fringe light, and a light and dark fringe light transmitted through the second scale An optical encoder comprising: a light receiving unit that performs photoelectric conversion of: a first cylinder arranged to include the light emitting unit or the light receiving unit therein; and a second cylinder arranged to include the first cylinder inside. And at least one of the two cylinders is rotatable about its axis. The first scale has a cylindrical surface shape near the light emitting unit of the two cylinders. Formed into Is, the second scale, optical encoder, characterized in that it is formed in a cylindrical surface shape in a cylindrical closer to the light receiving means of said two cylinders. 2. The optical encoder according to claim 1, wherein the scale formed on the rotatable cylinder is curved in a cylindrical surface concentric with the cylinder. . 3. The optical encoder according to claim 1, wherein the first scale main body is arranged in contact with a cylindrical surface of a cylinder close to the light-emitting means, and the first scale main body is provided. An optical encoder, comprising: an elastic member that presses the elastic member onto the cylindrical surface. 4. The optical encoder according to claim 1, wherein the second scale main body is disposed in contact with a cylindrical surface of a cylinder close to the light receiving unit, and wherein the second scale main body is provided. An optical encoder, comprising: an elastic member that presses the elastic member onto the cylindrical surface. 5. The optical encoder according to claim 1, wherein the light emitting unit is an incoherent light source. 6. A lens barrel having the optical encoder according to claim 1, wherein the first cylinder and the second cylinder are disposed inside the lens barrel. A photographing lens housed inside the first cylinder, and a lens driving mechanism that drives the photographing lens in conjunction with a relative rotational movement between the first cylinder and the second cylinder. A lens barrel comprising: