JPH0285716A - Rotary encoder - Google Patents

Abstract

PURPOSE:To miniaturize the size and to reduce the thickness of a rotary encoder by utilizing diffracted rays of light of a specific number of order from a cylindrical diffraction grating coupled with a rotating object to be detected. CONSTITUTION:Luminous fluxes emitted from both end faces of a laser 1 are respectively changed to parallel rays of light 81 and 82 by means of collimator lenses 21 and 22. One luminous flux 81 is changed to clockwise circularly polarized rays of light and made incident on one point M1 of a diffraction grating 4. The other luminous flux 82 is changed to counterclockwise circularly polarized rays of light and made incident on another point M2 of the grating 4. Then the positive and negative m-th order diffracted rays of light of the diffracted rays of light respectively produced at the points M1 and M2 are superimposed upon each other through a non-polarization beam splitter 5. Since the superimposed diffracted rays of light become linearly polarized rays of light with the polarizing direction rotated following the rotation of the grating 4, bright-and-dark changes are produced by polarizing plates 61 and 62. When the grating 4 is turned by one grating pitch, the + or -m-th order diffracted rays of light change in phase by + or -2mpi and the rays of light passed through the plates 61 and 62 produce bright-and-dark changes 2m times and, as a result, 2m pieces of sine signals can be obtained from photodetectors 71 and 72.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rotary encoder, and in particular, to a rotary encoder, in particular, a cylindrical object having a plurality of lattice patterns of transparent parts and reflective parts on the outer circumferential surface or inner circumferential surface of a cylindrical object in a periodic manner. Attach a diffraction grating to a rotating object, irradiate the diffraction grating with a beam of light from, for example, a laser, and use the diffracted light from the diffraction grating to change the rotational speed or rotational speed of the diffraction grating or the rotating object. This invention relates to a rotary encoder that electrically detects rotational conditions such as rotational speed.

(Prior art) Conventionally, it has been used to measure the rotational speed and the amount of variation in rotational speed of computer equipment such as the drive of a floppy desk, office equipment such as a printer, or NC machine tools, as well as rotational mechanisms such as the carburetor stainless steel motor and rotating drum of a VTR. A photoelectric rotary encoder has been used as a means for detection.

For example, as shown in FIG. 10, a rechargeable rotary encoder has a so-called main scale 31 in which light-transmitting parts and light-shielding parts are provided at equal intervals around a disc 35 connected to a rotating shaft 30, and a corresponding main scale. A so-called fixed index scale 32 that has a light-transmitting part and a light-blocking part at equal intervals to the scale.
A so-called index scale system configuration is adopted in which both scales are placed facing each other with the light projecting means 33 and the light receiving means 34 sandwiching them. In this method, as the main scale rotates, a signal synchronized with the interval between the light-transmitting part and the light-blocking part of both scales is obtained, and this signal is frequency-analyzed to detect fluctuations in the rotational speed of the rotating shaft. For this reason, the finer the scale interval between the light-transmitting part and the light-blocking part of both scales, the more
Detection accuracy can be improved. However, when the scale interval is made smaller, the S/N ratio of the output signal from the light receiving means decreases due to the influence of the diffracted light, resulting in a decrease in detection accuracy. Therefore, if you fix the total number of gratings in the light-transmitting part and the light-blocking part of the main scale, and try to increase the distance between the light-transmitting part and the light-blocking part to the extent that they are not influenced by diffracted light, the diameter of the disc of the main scale This increases the thickness and increases the overall size of the device, resulting in disadvantages such as a heavy load on the rotating object to be tested.

(Problems to be Solved by the Invention) The present invention provides a rotary encoder that has a small load on a rotating object to be inspected, can easily reduce the size and thickness of the entire device, and can detect the rotational state with high precision. With the goal.

(Means for solving the problem) Light beams from a coherent light source are made incident on different positions on a diffraction grating provided on the inner circumferential surface or outer circumferential surface of a cylindrical object connected to a rotating object, and Diffracted lights of specific orders generated from different positions of the diffraction grating are superimposed and interfered with each other, the interference light flux is received by a light receiving means, and the rotational state of the rotating object is determined using an output signal from the light receiving means. That's true.

In addition, in the present invention, the first and second light beams from a coherent light source are made incident on the position M1 of a diffraction grating provided on the inner circumferential surface or outer circumferential surface of a cylindrical object connected to a rotating object. Among the diffracted lights generated by the first and second light beams from the position M1, the first and second diffracted lights of specific orders are placed at a position WM2 that is approximately point symmetrical to the position M1 with respect to the rotation center of the diffraction grating. Proceeding the optical path to make the light incident, the diffracted lights of a specific order generated by the first and second diffracted lights interfere with each other at the position M2, the interference light flux is received by the light receiving means, and the output from the light receiving means The rotation state of the rotating object is determined using the signal.

(Embodiment) FIG. 1 is a schematic diagram of a main part of a first embodiment of the present invention. Reference numeral 1 on the right side of the figure is a coherent light source such as a semiconductor laser, which oscillates a coherent light beam from both ends. 22,
2□ is a collimator lens, and 31.3□ is a quarter-wave plate, the polarization axis of which is placed at an orientation of ±45° with respect to the polarization direction of the light source l. 4 is a cylindrical diffraction grating, and a plurality of gratings are carved at equal intervals on the inner surface of a cylindrical object made of glass or metal. This cylindrical diffraction grating 4 is connected to a rotating object to be detected (not shown) and rotates. Reference numeral 5 denotes a non-polarizing beam splitter, and reference numerals 16 and 62 denote polarizing plates, which are arranged so that their polarization directions are tilted relative to each other by 45 degrees. 7. ．． 72 is a light receiving element.

Next, a method for detecting the rotational state of the rotating object to be tested according to this embodiment will be explained. The light beams emitted from both end faces of the semiconductor laser 1 are transformed into substantially parallel light beams 8. by the collimator lens 21.2□. ．． It becomes 82.

Of these, the light beam 81 is rotated clockwise (
(or counterclockwise) becomes circularly polarized light and enters one point M of the cylindrical diffraction grating 4. Also, the other luminous flux 8. is turned into counterclockwise (or clockwise) circularly polarized light by the quarter-wave plate 32, and is incident on one point M2 of the cylindrical diffraction grating 4. Here, the points M1 and M2 are in a substantially symmetrical positional relationship with respect to the rotation center of the cylindrical diffraction grating 4. and point M, and point M2
+ (or -) m at point M1 of the diffracted light generated at
The next-time forward light, the - (or +) mth-th forward light at point M2, is superimposed via the non-polarizing beam splitter 5.

Here m is a positive integer. The overlapping of right-handed and left-handed circularly polarized light results in linearly polarized light, but as the polarization direction rotates with the rotation of the diffraction grating 4, the polarizing plate 6.
．． 62 results in a change in brightness and darkness. The phase of ±m-order diffracted light changes by ±2mπ when the diffraction grating 4 is rotated by one grating pitch, so the polarizing plate 6. ．． The light transmitted through the diffraction grating 62 changes brightness and darkness 2m times due to one grating pitch rotation of the diffraction grating 4, and 2m sine wave signals are obtained from the light receiving elements 72, 7□.

If the number of gratings marked on the cylindrical diffraction grating 4 is N, then the light receiving elements 70, 7
2 mN sine waves are obtained from □. For example, inner diameter 2
If 32,400 gratings are scored at a pitch of 2 μm on a 1 mm cylindrical surface and ±1st order diffracted light is used, 64,
800 sinusoidal signals are obtained. This is a sine wave signal,
One cycle corresponds to 20 angular seconds. Also, a polarizing plate 6.
．． Since the polarization direction of 62 is relatively shifted by 45 degrees, the light receiving elements 7I and 7□ receive 90
A sine wave signal with a phase difference of 0 is obtained, which makes it possible to determine the direction of rotation.

In this embodiment, the rotation center of the rotating object and the cylindrical diffraction grating 4 are determined by using diffracted light from two points M r and M 2 that are approximately symmetrical with respect to the rotation center of the cylindrical diffraction grating 4. This reduces measurement errors caused by eccentricity with respect to the center.

In addition, the semiconductor laser 1 is configured so that the intensity of the light beams emitted from both ends of the semiconductor laser 1 is almost the same, or the light beam with the stronger intensity emitted from one end of the semiconductor laser 1 is placed in the optical path. It is preferable to increase the brightness ratio of the interference fringes by providing an ND filter or the like so that the intensities of the diffracted lights that interfere with each other become equal.

FIG. 2 is a schematic diagram of main parts of a second embodiment of the present invention. In this figure, elements having the same functions as in FIG. 1 are given the same numbers. In Fig. 2, a cylindrical diffraction grating 4 is shown.
Among the diffracted lights at points M and M2, the light receiving elements 7I and 7
The non-polarizing beam splitter 52 superimposes the diffracted light of the opposite sign to the ±m-order diffracted light detected by □, that is, the non-m-order diffracted light.

The light beams superimposed by the non-polarizing beam splitter 52 are detected by the light receiving element 73. Since the light-receiving element 73 does not receive light through a polarizing plate, its output does not become an interference signal, and only the change in the amount of light of the m-th forward light occurring at point MI1 and point M2 is output. Therefore, if the difference between the output of the light-receiving element 7J and the output of the light-receiving element 71.7□ is taken, the DC fluctuation portion of the output of the light-receiving element 71.72 can be removed.

In other words, the reflectance of the grating of the diffraction grating 4 is not uniform,
When using an amplitude type diffraction grating, the line width of the reflective part is not uniform, and when using a phase type diffraction grating, the groove shape (height or width) of the grooves is not constant. If the diffraction efficiency of the diffracted light becomes uneven, the light receiving element 71
The interference signal of the output signal from , 7□ becomes unstable No. 43 modulated by DC fluctuation. This DC fluctuation also occurs when the output of the coherent light source l fluctuates due to environmental changes such as temperature changes.

In this embodiment, the DC fluctuation at this time is detected by the non-polarizing beam splitter 52 and the light receiving element 73, and the
．． ．． 72 output signal is stabilized. This makes it possible to perform measurements with higher accuracy.

FIG. 3 is a schematic diagram of main parts of a third embodiment of the present invention. In this figure, elements having the same functions as those in FIG. 1 are given the same reference numerals. In Fig. 3, 2 is a collimator lens, and 5 is a collimator lens.
3.54 is a reflecting mirror.

Next, a method for detecting the rotational state of the rotating object to be tested in this embodiment will be explained.

A coherent light beam emitted from the laser 1 is turned into a substantially parallel light beam by a collimator lens, and is incident on one point M1 of the cylindrical diffraction grating 4 almost perpendicularly to the arrangement direction of the diffraction grating 4. At point M1, depending on the grating pitch of the diffraction grating 4 and the wavelength λ of the laser 1, θea = 5in-'(mλ/P) -----
----------Angle θm (m
is a positive integer), and ±m-order diffracted light is generated. For convenience of displaying the ±m-order diffracted light generated at point M, the diffracted light generated on the left side of the paper in FIG. 3 is designated as 210, and the diffracted light generated on the right side is designated as 220. When the cylindrical diffraction grating 4 rotates by one grating pitch in the direction of the arrow in FIG. only changes. The diffracted light 210.220 is reflected by the reflecting mirror 53.54 and is 1/
The 4-wavelength plate 38.3□ converts the light into clockwise (or counterclockwise) circularly polarized light and counterclockwise (or clockwise) circularly polarized light, which is reflected again by the reflecting mirror 53.54 to one point on the cylindrical diffraction grating 4. It enters M2. Here, the points M1 and M2 are in a nearly symmetrical positional relationship with respect to the rotation center of the cylindrical diffraction grating 4. The diffracted light 210 enters the point M2 from the right side on the paper of Figure 3 at an incident angle θ. The diffracted light 220 enters from the left side on the paper surface of FIG. 3 at an incident angle θ1. Then, the m-th order diffracted light generated at point M2 is emitted in a direction substantially perpendicular to the incident lights 210 and 220, and overlaps with each other. When the cylindrical diffraction grating 4 rotates by one grating pitch in the direction of the arrow in FIG. It changes by 2mπ. In other words, laser 1
As a result of being emitted and undergoing m-th order diffraction at point M31 and point M2,
The phase of the light beam 210 changes by 4 mπ with respect to rotation of one grating pitch of the cylindrical diffraction grating 4. Similarly, luminous flux 2
20, the phase changes by 4mπ in the opposite direction to the phase change of the light beam 210 as a result of the m-th order diffraction at the point M39 and the point M2.

In this way, the diffracted light beam at point M2 becomes linearly polarized light as a result of the overlapping of clockwise and counterclockwise circularly polarized light, but its polarization direction rotates as the diffraction grating 4 rotates. Polarizing plate 6I.

62 results in a change in brightness and darkness. As described above, when the diffraction grating 4 rotates by one grating pitch, the phase of the overlapping light beams changes by ±4 mπ, so the light transmitted through the polarizing plate 69.6□ repeats brightness and darkness 4 m times, and the light receiving element 7. ．． 72, 4m sine wave signals are obtained.

If the number of gratings marked on the cylindrical diffraction grating 4 is N tree, the number of light receiving elements 71.7□ will increase with one rotation of the diffraction grating 4.
From this, 4 mN sine waves are obtained. For example, if 32,400 gratings are scored at a pitch of 2 μm on a cylindrical surface with an inner diameter of 21 mm, and using ±1st-order diffracted light, one rotation will result in 1 rotation.
29,600 sinusoidal signals are obtained. This corresponds to 10 angular seconds per period of the sine wave signal. Also, since the polarization direction of the polarizing plate 61.6° is relatively shifted by 450 degrees, the light receiving element 7. ．． As the diffraction grating 4 rotates, a sine wave signal having a phase difference of 90° is obtained from the grating 72, and the direction of rotation can also be determined.

In this embodiment, by using diffracted light from two positions M, , M2 that are approximately point symmetrical with respect to the rotation center of the cylindrical diffraction grating 4, the rotation center of the rotating object and the cylindrical diffraction grating 4 are This reduces measurement errors caused by eccentricity with respect to the center.

Furthermore, in this embodiment, two optical paths 21 are made to interfere with each other.
The cylindrical diffraction grating 4 is arranged at the positions M, .

In other words, it has the advantage that the diffraction grating 4 is easy to manufacture.

FIG. 4 is a schematic diagram of the main parts of a fourth embodiment of the present invention. In this figure, elements having the same functions as those in FIG. 1 are given the same reference numerals.

In FIG. 4, reference numerals 9I and 9□ are polarizing beam splitters, which split the light beam emitted from the laser 1 into two light beams 41° and 42 which are linearly polarized lights orthogonal to each other. That is,
The light beam 41 is a linearly polarized light oriented parallel to the plane of the paper, and the light flux 42 is a linearly polarized light oriented perpendicular to the plane of the paper, which is transmitted to the point M1 of the diffraction grating 4 via a reflecting mirror 53, 54 at a diffraction angle of ±01 as shown by equation (1). It is incident. The ±m-order diffracted lights generated at point M are emitted from point M1 in an overlapping manner in a perpendicular direction, and enter a position M2 that is approximately symmetrical about the rotation center of the diffraction grating 4. Then, the ±m-order diffracted light generated again at point M2 is reflected by the reflecting mirror 5. ．． 56 and a polarizing beam splitter 92. A quarter-wave plate 31 superimposes left and right circularly polarized light into rotating linearly polarized light, and a polarizing plate 6. ．．
Detecting the change in brightness caused by 62 using the light receiving element 71.7□ is similar to the embodiment shown in FIG.

In Fig. 3, the diffracted light is detected by making the light incident perpendicularly to the point M and emitting in the vertical direction at the point M2, but as shown in Fig. 4, the diffracted light is made incident to the point M at a diffraction angle and is perpendicular to the point M2. The same effect can be obtained even if it is incident on .

In Fig. 3, the reflected diffracted light of the diffraction grating 4 is detected, and in Fig. 4, the transmitted diffracted light of the diffraction grating 4 is detected, but exactly the same effect can be obtained by detecting the transmitted diffracted light and the reflected diffracted light respectively. .

5, 6, and 7 are the 5th and 6th sections of the present invention. FIG. 7 is a schematic diagram of main parts of a seventh embodiment. In each of these embodiments, the rotation state of the rotating object to be tested is detected using the diffracted light from one point M of the diffraction grating 4.

In addition, 5th. 6th. In FIG. 7, elements having the same functions as those in FIG. 3 are given the same reference numerals.

In the fifth embodiment shown in FIG. 5, the light beam emitted from the end face of the laser 1 is turned into a substantially parallel light beam by the collimator lens 2, and is incident on one point M of the cylindrical diffraction grating 4. The ±m-order diffracted light (m is a positive integer) generated at point M is 1
/4 wavelength plate 3I.

3□, the light becomes clockwise (or counterclockwise) and counterclockwise (or clockwise) circularly polarized light, which is reflected by the reflecting mirrors 53 and 54, and overlaps via the non-polarizing beam splitter 5. The overlapping of right-handed and left-handed circularly polarized light results in linearly polarized light, but its polarization direction rotates as the diffraction grating 4 rotates, and the polarizing plate 6. .

62 results in a change in brightness and darkness. The phase of ±m-order diffracted light changes by ±2mπ when the diffraction grating 4 rotates by one grating pitch, so the light that passes through the polarizing plates 61 and 62 changes brightness and darkness 2m times by rotating one grating pitch of the diffraction grating 4. Thus, the light receiving element 7.

2m sine wave signals can be obtained from 7□. If the number of marked gratings of the cylindrical diffraction grating 4 is N, then as the diffraction grating 401 rotates, the light receiving elements 7, . 72 to 2
mN sine waves are obtained.

For example, 32.4 mm at a pitch of 2 μm on a cylindrical surface with an inner diameter of 21 mm.
If 00 gratings are scored and ±1st order (m=1) diffracted light is used, 64,800 sine wave signals can be obtained in one rotation. This corresponds to 20 angular seconds per period of the sine wave signal. Also, a polarizing plate 6. ．． Since the polarization direction of light receiving element 7.62 is relatively shifted by 45 degrees, the polarization direction of light receiving element 7. ．． 72, a sine wave signal having a phase difference of 90° is obtained as the diffraction grating 4 rotates, and the direction of rotation can also be determined.

The sixth embodiment shown in FIG. 6 is the same as the fifth embodiment shown in FIG. ．． The arrangement relationship with 72 has been exchanged. That is, the coherent light beam from the laser 1 is made into a substantially parallel light beam by the collimator lens 2,
The light beam is split into two by a non-polarizing beam splitter 57, reflected by reflecting mirrors 53 and 54, and then passed through a 174-wave plate 3. ．． 32
The light is incident on the cylindrical diffraction grating 4 as right-handed (or counter-clockwise) circularly polarized light and left-handed (or right-handed) circularly polarized light. At this time, the ±m-order reflected diffraction light generated by the diffraction grating 4 is made incident so as to be reflected from the diffraction grating 4 almost perpendicularly.

That is, the grating pitch of the diffraction grating 4 is P, the wavelength of the coherent light beam is λ, m is an integer, and the angle of incidence on the diffraction grating 4 is θ,
When θIIl valve is 5 in-' (mλ/P), the light is incident on the valve.

The ±m-order diffracted lights reflected almost perpendicularly from the diffraction grating 4 overlap each other. Here, the right-handed and left-handed circularly polarized light overlap, resulting in linearly polarized light, but the polarization direction rotates with the rotation of the diffraction grating 4, and the polarizing plate 6. ．． 62 results in a change in brightness and darkness.

In the seventh embodiment shown in FIG. 7, reference numeral 109 is an end-face imaging type refractive index distribution type optical member, and a reflective film 10 is provided on one end. Condensing system 2 from optical member 109 and reflective film 10
It constitutes 0. 9. is a polarizing beam splitter. In this embodiment, two light beams are applied to the cylindrical diffraction grating 4 at a diffraction angle of ±mm as in the embodiment shown in FIG.
The beams are made incident at an angle of θ, and the beams are made to be incident on the optical member 109 of the condensing system 20 with ±mm beams superimposed perpendicularly on each other. Since a reflective film 10 is provided near the focal plane of the optical member 109, the incident light beam is reflected by the reflective film 10 as shown in FIG.
After being reflected, the light returns along the original optical path, exits from the optical member 109, and enters the diffraction grating 4 again.

Then, the m-th order reflected diffracted light that is diffracted again by the diffraction grating 4 returns to the original optical path, is reflected by the reflection g53,5<, and is reflected by the quarter-wave plate 3. ．． 32 and enters the polarizing beam splitter 9 again. At this time, the re-diffracted light is 1/4 wavelength plate 31.3
Since the light beam goes back and forth between the polarizing beam splitter 9 and the polarizing beam splitter 9, when it re-enters the polarizing beam splitter 91, the polarization direction is 90 degrees different from that of the polarizing beam splitter 91, so that it is transmitted. Conversely, polarizing beam splitter-91
The light beam that first passes through the beam will be reflected when it re-enters the beam. In this way, the two diffracted lights are superimposed by the polarizing beam splitter 91, passed through the 1/4 wavelength plate 33, and then made into circularly polarized light. ．． After passing through 6□, the light is converted into linearly polarized light and incident on light receiving elements 70 and 7□, respectively.

In this example, the phase of the ±m-order diffracted light is determined by the diffraction grating or 1
When the lattice pitch is moved, it changes by 2mπ. Therefore, the light receiving element 7. ．． 72 receives interference of light beams that have undergone positive and negative m-order diffraction twice, so when the diffraction grating moves by one pitch of the grating, 4m sine wave signals are obtained.

In other words, in this embodiment, a resolution twice as high as that in the embodiments shown in FIGS. 5 and 6 can be obtained.

Since the condensing system 20 in this embodiment has a reflective surface disposed near the focal plane, the angle of diffraction changes slightly due to a change in the oscillation wavelength of the laser beam, for example, and the angle of incidence on the condensing lens changes somewhat. However, even if the optical path is the same, it is possible to return the optical path in exactly the same way. This causes the two positive and negative diffracted lights to overlap and pass through the light receiving element 7.
．． ．． This prevents the S/N ratio of the output signal of 72 from decreasing.

In this embodiment, a gradient index lens is used as the optical member 109 for downsizing, but a combination of a condenser lens 12 and a reflector 'm13 as shown in FIG. 9 may be used.

(Effects of the Invention) According to the present invention, by utilizing diffracted light of a specific order from a cylindrical diffraction grating connected to a rotating object to be inspected, a highly turbulent device is used which reduces the size and thickness of the entire device. Rotary encoder can be achieved. Furthermore, by interfering diffracted lights from two points that are approximately symmetrical about the center of rotation and detecting the interference light flux, it is possible to reduce the eccentricity error when attaching a cylindrical diffraction grating to a rotating object. An obscene rotary encoder can be achieved. Furthermore, by arranging the diffraction grating at a position where the two optical paths that are caused to interfere with each other match, it is possible to eliminate the influence of the surface roughness of the diffraction grating, making it easier to manufacture the diffraction grating. There is.

[Brief explanation of the drawing]

1 to 7 are schematic diagrams of main parts of the first to seventh embodiments of the present invention, and FIG. Figure 9 is an explanatory diagram of a part of Figure 7,
FIG. 0 is a schematic diagram of a conventional rechargeable rotary encoder. In the figure, 1 is a laser, 2, 2. ．． 22 is a collimator lens, 38, 3□, 33 is a quarter wavelength plate, 4 is a cylindrical diffraction grating, 5.52 is a non-polarizing beam splitter 153
, 54 is a reflecting mirror, 61°6□ is a polarizing plate, 7. ．． 72.7
3 is a light receiving element; 9, . 92 is a polarizing beam splitter. Patent applicant: Canon Co., Ltd. Figure 1 Ml Figure 2 Figure 4 Figure 5 Figure M Figure 6 Figure 7

Claims (2)

[Claims] (1) Light beams from a coherent light source are incident on different positions on a diffraction grating provided on the inner or outer peripheral surface of a cylindrical object connected to a rotating object, and the light beams are generated from different positions on the diffraction grating. A rotary encoder characterized in that diffraction lights of a specific order are superimposed and interfered with each other, the interference light beam is received by a light receiving means, and the rotational state of the rotating object is determined using an output signal from the light receiving means. . (2) The first and second light beams from a coherent light source are made incident on a position M1 of a diffraction grating provided on the inner or outer circumferential surface of a cylindrical object connected to a rotating object. Among the diffracted lights generated by the first and second beams, the first and second diffracted lights of specific orders are placed at the position M with respect to the rotation center of the diffraction grating.
The same optical path is advanced to a position M2 which is approximately point symmetrical to 1, and the diffracted lights of a specific order generated by the first and second diffracted lights are made to interfere with each other at the position M2, and the interference light beam is received by a light receiving means. A rotary encoder, characterized in that the rotation state of the rotating object is determined using an output signal from the light receiving means.