JPS5948616A - Optical type rotary encoder - Google Patents

Abstract

PURPOSE:To make a light receiving apparatus compact by admitting transmission lights through a main signal slit section and those through a sub slit section into a single lens with a light receiving element composed of a refractive index distribution type lens whose refractive index decreases parabolically to the periphery from the maximum on the center axis. CONSTITUTION:In a light projection element 11, one end of an optical transmission fiber 14 is connected to one end face of a refractive index distribution type lens 12 whose lens length is set at 1/4 pitch to match optical axes thereof, a similar refractive index distribution type lens 13 is connected to the other end thereof 14 and a light source 15 such as light emitting diode is arranged opposite to the lens 13. Light from the light source 15 enters the refractive index distribution type lens 13 to be focused, is transmitted through the optical fiber 14 and made parallel light with the lens 13. The diameter of the lens 13 is so selected that the parallel light 16 emitted from the lens 13 passes through both of a main signal slit section 5 and a zero signal slit section 6 on a rotary disc 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention allows both signal lights transmitted through a main signal slit and a zero signal slit provided on a rotating disk to be incident on a single photodetector for separate detection, thereby making the light receiving device more compact. This invention relates to an optical rotary encoder.

Measuring the number of revolutions An optical rotary encoder, which is widely used for measuring the angular displacement of one rotation, positioning a workpiece, etc., is generally constructed as shown in Figure O1.

In other words, a disk 2 is provided on a rotating shaft connected to a mechanism to be measured such as a motor whose rotational speed is measured, and a main signal consisting of light-shielding parts 3 and transparent parts 2 are arranged at equal intervals along the circumference of this disc 2. A slit S is provided.

In addition, on the inner circumferential side of this main signal slit s, there is a single small-area light-shielding part (if the disc is made of a transparent material) or a light-transmitting part (
When the disc 2 is made of a light-shielding material), a zero signal slit 6 is provided.

A small opening A is formed corresponding to the passing position of the main signal slit S and the passing position of the zero signal slit B.

An index scale 7 provided with a gap B is fixedly arranged near the periphery of a rotating disk.

Then, on both sides of the rotating disk, there are emitters 9A, 9B and receivers 10A, 1 corresponding to both signal slits 3°, respectively.
Place 0B facing each other.

As a result, each time the rotating disk rotates, the light beam from the emitter 9B to the photoreceiver 10H is blocked or transmitted by the zero signal slit B, and the rotation is detected.

Further, the light beam from the emitter qA toward the photoreceiver 10A is interrupted by the main signal slit j, and a minute rotational angular displacement is detected.

In the optical rotary encoder as described above, a pair of light emitters 9 are provided in correspondence with each signal line (5.4).
Since the light emitters A, 9B and the photoreceivers IOA, 10B are arranged, a large space is required to install these light emitters and photoreceivers, and there is a problem in that the overall size of the rotary encoder apparatus cannot be made very small.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical row (3) tally encoder which can solve the above-mentioned conventional problems and can greatly save space for arranging components, particularly on the photoreceptor side, and make the entire device compact.

In order to achieve the above object, the present invention provides a main signal slit consisting of a light-shielding part and a light-transmitting part spaced apart in the circumferential direction of a rotating disk, and also has a main signal slit for transmitting a zero signal on the inner circumference side of the main signal slit. In an optical rotary encoder, a light emitter and a light receiver are arranged on both sides of the rotary disk, sandwiching these slits, and the light receiver has a maximum refractive index on the central axis. The lens is composed of a gradient index lens having a distribution that decreases parabolically toward the periphery, and the light transmitted through the main signal slit and the light transmitted through the sub-slit are made incident on a single lens. Optical transmission fibers are connected to the output surface in correspondence with the output positions of the light transmitted through each of the slits to form a single tally encoder, and the other end of the fiber is connected to a photoelectric conversion element such as a run sister. do.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments shown in the drawings.

Fig. 2 is a perspective view showing an embodiment of the present invention (1) The same parts as in Fig. 1 are given the same numbers as in Fig. 1.

In FIG. 2, // is a light emitter, and 7.2 is a photoreceiver.

The projector is constructed by connecting one end of an optical transmission fiber to one end surface of a gradient index lens with a pitch length of 1 minute and an optical axis of the optical transmission fiber. A similar gradient index lens /3 is connected to the other end of /l, and a light IMi such as a light emitting diode is connected to this lens /3.
s are placed facing each other.

As a result, the light beam emitted from the light source 15 enters the gradient index lens /3, is focused on the other end face, is transmitted through the optical fiber /ge, and is converted into a parallel light beam by the lens /3.

The diameter of the lens 13 is selected so that the parallel ray /B emitted from this lens /3 passes through both the main signal slit section S and the zero signal slit section O of the rotating disk-10.

Here, as is well known, a gradient index lens is made of a transparent cylindrical body made of glass or plastic, and the refractive index N (r) at a distance r from the central axis is the maximum refractive index No on the center (j) axis. N (r) =NO(/-//2 Ar2)...-
...-(/) However, A has a distribution expressed by a positive constant.

A ray of light incident parallel to the optical axis into such a gradient index lens forms a sine curve whose length P of 7 periods (pitch) is P - π/V'A (2) Draw and proceed.

The photoreceptor /2 is formed by obliquely polishing one end face of the gradient index lens /3 as described above by tilting it by a certain angle θ from a plane perpendicular to the central axis /, thereby forming a pair of inclined incidence surfaces /3. 7A and /7B are provided. This results in
Light ray / Otsu A that came out from the projector // and passed through main signal slit part j enters the entrance surface / 7A of lens / 3, and light ray / Otsu B that passed through zero signal slit part O is incident on lens / 3 Make it incident on surface /7B.

(≦) Lens length 2 should be approximately o, 2s P (pitch) 0. If the entrance plane /7A, /7B is a plane perpendicular to the central axis /za, set lens length 2 to 0. ．． 2! ; When P, the rays A and B incident parallel to the central axis will be focused at the center on the other end surface of lens 3, but as shown above, if the angle formed by both sides of the incident surface is Slanted surface so that it is less than 0 degrees/7
A, /7B, the light rays incident on these incident surfaces /7A, /7B are refracted toward the center axis, converged slightly inside the other end surface of lens /3, and then intersect to reach the other end surface of the lens. Then, the light is emitted at a position offset by a distance r2 from the central axis.

Then, one end side of a pair of optical transmission fibers /llA and /4'B is connected to the output positions of these two beams /OtsuA and /OtsuB, respectively.

In addition, a graded index lens of o, 2sp length is connected to the other ends of both optical transmission fibers /4'A and /4'B to convert the diffused emitted light from the fibers into parallel light and convert it into a phototransistor. The light is incident on a light-receiving element such as

Here, the relationship between the angle of inclination θ of the incident surface of the lens 130 and the amount of deviation r2 of the output light beam from the central axis is r2= (No-/) Xθ/NOV'A ・-
--...<3).

As described above, both signal lights /Ah and /B are put into a single gradient index lens /3 and are split within the lens, so the main signal slit S on the rotating disk
The distance between the zero signal slit B and the zero signal slit B can be narrowed to the limit where the two contact each other, and the outer diameter of the photoreceptor/3 can be reduced accordingly to the distance between the outer edges of both slits. .

Furthermore, by appropriately selecting the incident surface inclination angle θ, the rain detection optical fiber/lA of the main signal and zero signal can be obtained.

/47B It is also possible to set the minimum side spacing to zero, that is, the outer diameter of the fiber is d, and 2r2 = a,
Optical fiber wiring also requires an extremely small space.

Further, the light receiving element/9 can be installed at a position away from the rotating part where a sufficient space can be secured.

As the photoreceptor /2 used in the present invention, one end surface of the gradient index lens /3 has a plurality of axially symmetrical oblique cross sections /7A such that the angle between the surfaces is less than 1 gO degree.

/7B In addition, both end faces were made parallel planes perpendicular to the central axis as shown in the diagram. ,, A prism 20 is provided on one end face of a gradient index lens /3 with a pitch length of 2s, and is made of ordinary glass or plastic with a uniform refractive index and has image sections /7A and /7B at a predetermined angle. The photodetector/2 may be configured by bonding them together.

Another embodiment of the present invention is shown in the diagram.

This example shows an example of the structure of a rotary encoder in which a main signal slit J and a zero signal slit 6B are provided in addition to the sub slit 6B on a rotating disk, and approximately 0.0. ．． 2! ; Pitch length gradient index lens/3 One end surface has different angles θ1 to the plane perpendicular to the optical axis. θ2.
Incident surfaces /7A, /7B, and 17G that are inclined at θ3 are provided, and these three types of inclined incidence surfaces (9) /7A, /7B, and /70 are provided with a main signal slittor, a zero signal slit A, and additional functions, respectively. The light beam transmitted through the sub-slit 6B is made incident.

Then, each light beam is refracted at each of the incident surfaces and enters the lens /3, and is branched at the other end face of the lens. Optical fibers /llA, /
4/B, /llC.

In the above example, one end of the gradient index lens /3 was formed into a multifaceted surface forming an angle to form the photoreceptor 7.2, but as shown in the diagram, both end faces are parallel planes perpendicular to the central axis. Using a rate distribution type lens /3, the lens length Z may be selected to be more than a pinch of O, 2 and less than an O1j pitch.

In such lens /3, a ray of light incident parallel to the central axis at a distance of r3 from the central axis exits at the other end surface of the lens with a distance of r4 from the central axis, and r3 and r4
Between r4 = r3 cos V'I Z ・------
・-(11)(10) The relationship holds true.

Therefore, if the lens length Z is selected so that the above r4 is approximately equal to the radius of the connecting optical fiber /4'B, which is bare or coated with a resin coat, etc., the main signal and zero signal of the index scale 7 can be Regardless of the spacing between the openings, the minimum wiring space is required.

Further, as shown in the off-line diagram, two or more prisms and 2OA are included in the gradient index lens 13 whose end surfaces are parallel planes.

, 20B, etc., the various signal lights transmitted through the rotary disk 2 and the index scale 7 are received by a single lens/3, branched within the lens, and connected to separate light receiving elements. Optical fiber/l...
It is also possible to configure the beam to be incident on...

[Brief explanation of drawings]

The OFF view is a perspective view showing a conventional optical rotary encoder, the OFF view is a perspective view showing an embodiment of the present invention, FIG. FIG. 7 is a side sectional view of a main part showing another embodiment. The S diagram is a side sectional view of a main part showing still another embodiment of the present invention, the O diagram is a side sectional view of a main part showing another embodiment of the invention, and the off diagram is a side sectional view of a main part showing another embodiment of the invention. FIG. −・・・・・・Rotating disk S・・・・・・Main signal slit name・・・・・・Zero signal slit (
Subslit) 7... Index scales 9A, 9B, //... Emitter 7.
2...Photoreceptor/3...Gradient index lens/, 4(, /IIA, /4'B...
......Optical transmission fiber/S...Light source /6......Light beam/9......Light receiving element -0,20A,,20B... ... Prism patent applicant Nippon Sheet Glass Co., Ltd. agent Patent attorney Seiichi Ohno

Claims (1)

[Claims] A main signal slit consisting of a light-shielding part and a light-transmitting part is provided at intervals in the circumferential direction of the rotating disk, and a sub-slit for transmitting a zero signal, etc. is provided on the inner circumference side of this, and these slit parts are sandwiched. In the optical rotary encoder in which a light emitter and a light receiver are arranged on both sides of the rotating disk, the refractive index of the light receiver is maximum on the central axis and decreases parabolically toward the periphery. The lens is configured with a gradient index lens having a refractive index distribution, and the light transmitted through the main signal slit portion and the light transmitted through the sub-slit portion are incident on a single lens,
An optical rotary encoder characterized in that an optical transmission fiber is connected to the output surface of the lens in correspondence with the output position of the light transmitted through each of the slits.