JPS5828653B2 - Interval detection device for optical recorder/player - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an optical recording/reproducing device (optical recording/reproducing device) capable of stably detecting the distance between a recording medium and a condensing lens for converging a recording or reproducing light beam. The present invention relates to an interval detection device for a recording or reproducing device.

Generally, an optical recording/reproducing device is configured to perform recording or reproduction while focusing a light beam such as a laser beam onto a recording medium.

However, it is not only impossible to form a recording medium (for example, a disk) into a completely flat plate, but also vertical movement occurs due to movement (for example, rotational movement) of the recording medium, making it difficult to focus the beam on the recording medium. It is difficult to maintain this condition.

Therefore, in general, changes in the distance between the recording medium and the optical device (for example, an objective lens) that are involved in focusing the light beam are detected by changes in the optical path of the reflected light of the light beam, and this detection signal indicates that the distance is always constant. The optical device or recording medium is controlled so that the

In such a device, if the information is a video image,
The spot size of the reading light beam must be focused to 1 μm at 8 degrees, and in order to achieve such light focusing, the distance between the condenser lens and the recording medium must be controlled with high precision of about ±1 μm based on diffraction theory. Must.

FIG. 1 is a diagram showing the principle of a conventional optical reproducing device.

In FIG. 1, 1 and 1' indicate a reading light beam and a reflected reading light beam, and the beam between the line 1 and 1' is the light beam.

2 is a condensing lens that cuts out from the convex lens, and its optical axis 3
are arranged perpendicular to the recording medium 4.

Po indicates a point light source of the reading light beam and is located on the optical axis 3.

The center of the light beam and the optical axis 3 of the condenser lens 2 are indicated by 1 and 1'.
coincide, so when the recording medium 4 is at the position shown by A with respect to the condenser lens 2, the light beam is focused on the recording medium surface, the beam spot becomes the minimum, and the position shown by When this happens, the beam spot becomes more dog-like than that at position A.

Therefore, the distance between the recording medium 4 and the lens 2 must be controlled so as to obtain the position A.

The distance between the two can be determined by directing the distance detection light beam 5 parallel to the optical axis 3 to the recording medium 4 through the lens 2.
This is known by detecting the reflected light beam 6, 7, or 8 for detection, which is the reflected light thereof, with the photodetector 9.

The photodetector 9 is a two-part photodetector consisting of photodetectors 9a and 9b, and the recording medium 4 is at the position A (focused position).
, the reflected detection light beam 6, which is the reflected light of the incident light beam 5, is incident on the dividing line between the photodetectors 9a and 9b, and the output of the photodetector 9a and the output of the photodetector 9b become equal. , the output of the error (differential) amplifier 10 is zero.

On the other hand, when the recording medium is at the position of the sum of the four recording media (position away from the focal point), the reflected detection light beam 7, which is the reflected light of the light beam 5, is incident above the dividing line between the photodetectors 9a and 9b. However, a larger output can be obtained from the photodetector 9a than from the photodetector 9b.

Furthermore, when the recording medium 4 is at position C (position approaching the lens), the reflected light beam 8 for detection, which is the reflected light of the light beam 5, enters below the dividing line between the photodetectors 9a and 9b, and the light A thicker output is obtained from the detector 9b than from the detector 9a.

Thereby, a signal corresponding to the position of the recording medium 4 can be obtained from the error amplifier 10.

The output of the error amplifier 10 is applied to the spacing controller 11, and the condensing lens 2 is displaced by, for example, a moving coil coupled to the lens 2, so that the spacing between the recording medium 4 and the lens 2 is constant, that is, the light beam is 1 is controlled to focus on the recording medium.

However, in this conventional method, when the recording medium 4 is displaced toward the lens 2, the reflected light beam for detection moves to the imaging position P of the light beams 1 and 1' for reading.

, and in the state of the reflected detection light beam 8, it overlaps with the reading light beam and cannot be separated.

In order to increase the width of the displacement (interval) that can be detected, that is, the dynamic range, the length of the photodetectors 9a and 9b can be adjusted to the same length, but since the photodetector 9b picks up the reading light beam, , and the dynamic range is limited to a certain value, and the dynamic range is only 100 to 200 μm at most in terms of displacement of the recording medium 4.

If the distance between the optical axis 3 and the detection light beam 5 is set to the same length, the photodetector 9b can be set to the same length, but if the conversion sensitivity (deflection angle of the reflected light beam with respect to a certain displacement) is kept at the same ratio. Since it becomes a dog, the dynamic range does not increase.

Furthermore, even if a beam splitter, semi-transparent mirror, etc. is inserted between the lens 2 and the point P1 to separate the light beam, the reading light beam will also be picked up, resulting in no improvement.

Furthermore, since the reflected light beam for reading is mainly incident on the photodetector 9b, an unbalance unrelated to displacement occurs in the output of the error amplifier 10, and furthermore, when the intensity of the reading light beam changes, the amount of unbalance changes. There were drawbacks.

An object of the present invention is to provide an optical recording or reproducing device capable of increasing the dynamic range (detectable distance range) when detecting the distance between a recording medium and a condensing lens using a distance detection light beam. An object of the present invention is to provide an interval detection device.

To achieve the above object, the present invention is arranged such that an optical axis is arranged perpendicular to a recording medium and a recording or reproducing light beam having an optical path coinciding with the optical axis is focused and projected onto the recording medium. a condensing lens disposed in the recording medium; a distance detection light beam projected non-orthogonally onto the recording medium through the condensing lens in order to detect the distance between the condensing lens and the recording medium; arranged so as to detect a reflected light beam obtained by reflection of a detection light beat on the recording medium after passing through the condensing lens, and a position of the reflected light beam for interval detection corresponding to a change in the interval; In an interval detecting device for an optical recording or reproducing machine, the optical path of the interval detecting light beam is changed to the condensing light beam. The front focal point of the lens is set to non-orthogonally cross a region of a plane perpendicular to the optical axis excluding the optical axis, and the position of the reflected light beam for distance detection is changed in accordance with the change in the distance. It is characterized in that the direction is set so as not to intersect the optical path of the recording or reproducing light beam, and the split-type photodetector is arranged at a position away from the optical path of the recording or reproducing light beam. This invention relates to an interval detection device for an optical recording or reproducing machine.

According to the above invention, since the optical path of the distance detection light beam is set to non-orthogonally cross the area excluding the optical axis of the plane (focal plane) perpendicular to the optical axis at the front focal point, The direction of change in the optical path of the reflected light beam for distance detection based on the change in the distance between the optical lens and the recording medium becomes a direction that does not intersect the optical path of the recording or reproducing light beam (optical axis of the condensing lens), and recording Alternatively, it becomes possible to detect the reflected light beam for interval detection without being obstructed by the optical path of the reproduction light beam.

Therefore, it is possible to set a large change range (detectable distance range) of the reflected light beam for distance detection, that is, a dynamic range, and it is possible to improve the accuracy of distance detection.

Next, an interval detecting device according to a practical example of the present invention will be described with reference to FIGS. 2 and 4 to 11.

FIG. 2 is a three-dimensional optical path diagram showing the principle of an interval detecting device according to an actual case of the present invention.

In FIG. 2, the reading light beams 1 and 1' are directed to a lens 2 having an optical axis 3 and a point light source P.

is incident as the light source position, and the same lens uses 10
Image a light spot at a point.

When the recording medium 4 is in focus, it is on the X4-74 plane, when it is out of focus toward the lens, it is on the X5 Yq plane, and when it is out of focus on the side away from the lens, it is on the Xo:! I'6
It's on the surface.

The reflected light from the recording medium surface travels backward along the same optical path as the incident optical path.

Reimage to a point.

In an actual information reproducing device, since information is read using reflected light, it is necessary to separate the incident and reflected optical paths using a beam splitter, but in this figure they are drawn on the same trajectory.

The displacement or interval detection light beam 5 is on the x1 axis P.

It starts from 11 points that are an appropriate distance away from the point, passes through 13 points on the y2 axis in the plane ,
This results in 17 points on the plane X4 31'4 including the focused point P9.

When the recording medium is on the X4'l'4 plane, a detection reflected light beam 6 is obtained from the light beam 5, and this is incident on the center of the two-split string ball of the two-split photodetector 9.

When the recording medium comes to the X5-75 plane, which is closer to the lens than the in-focus position, the detection light beam 5 is reflected at 16 points on the The light enters the vessel 9b.

On the other hand, the recording medium is further away from the focus position
'When it comes to the 6th plane, the detection light beam 5 is X6 y6f
The reflected light beam 7 is generated by reflection at 28 points of fi, and is incident on the photodetector 9a.

Therefore, by obtaining the difference between the photodetectors 9a and 9b from the error amplifier 10, a displacement output proportional to the displacement of the recording medium can be obtained, and this displacement output is sent to the interval controller 11 that drives the lens 2 in the optical axis direction. By applying this voltage, the reading light beam 1 can be focused on the recording medium while keeping the distance between the lens 2 and the recording medium constant.

In FIG. 2, optical path 12 is an optical path in which displacement cannot be detected.

Now, if the detection light beam is emitted in the optical path 12, it passes through the front focus P2 of the lens 2, and then passes through 14 points on the lens to become a beam parallel to the optical axis 3, which is X4Y4
Even if the light is reflected by the recording medium at any position on the plane, X5-75, or X6-y6, the incident optical path and the reflected optical path will be the same, and it will return to the starting point P1, making it impossible to detect displacement. .

If the detection light beam 5 is projected as shown in Fig. 2, the recording medium will be in the X4-74 plane,
No matter where the detection light beam 5 is displaced, the detection light beam 5
The reflected light beam in FIG. 2 only swings in the vertical direction, but does not swing in the horizontal direction in FIG.

Therefore, in any state, P is between the reading light beam and the reflected detection light beams 6.7 and 8.

There is an interval from to Pl, and they do not overlap.

For this reason, it is possible to make the detector 9 longer in the vertical direction as shown in Fig. 2 to obtain a sufficiently large dynamic range.
In Fig. 1, it was 0.1 to 0.2 mm at most, but compared to this, it can be significantly increased to 1 to 21n1rt.

In addition, in FIG. 2, even if the spot of the reflected beam of the reading light beams 1 and 1' is expanded due to defocusing and the light reaches the vicinity of the displacement detection photodetector 9, the photodetector 9 Since the light intensity distribution is symmetrical about the dividing line between one photodetector 9a and the other photodetector 9b, the error amplifier 1
0, the reflected light beam for reading does not affect the output of the error amplifier 10.

Next, another embodiment of the present invention will be described with reference to FIGS. 4 to 11.

FIG. 4 is a block diagram showing an optical recording and reproducing apparatus for optically reading information from a video disc.

In this drawing, 21 is a disk recording medium,
A pit (groove) corresponding to a signal is formed in a predetermined track shape, and a reflection direction is formed.

A morph 22 rotates the disk recording medium 21 during recording and reproduction.

A laser light source 23 projects a recording or reading light beam and an interval detection light beam onto the recording medium 21.

The path of the light beam between the laser light source 23 and the recording medium 21 includes a first half mirror 24, a concave lens 42, a diffraction grating 43, a second half mirror 25 (λ polarizing plate 44 and a first
mirror 26, rotating mirror 27, and condensing objective lens 2
8 are arranged.

Further, a second mirror 29, a detection beam auxiliary convex lens 30, a third mirror 31, a fourth mirror 32, and a fifth mirror 33 are arranged to create a path for the distance detection light beam.

In the optical system as described above, the first half mirror 24 splits the focusing light beam by passing the main light beam and reflecting the focusing (distance detection) light beam, and includes a concave lens. 42 widens the main light beam, and a diffraction grating 43 spreads the main light beam into a reading light beam and a tracking light beam (not shown).
In order to obtain is the wavelength of light) The polarizing plate 44 polarizes the reflected light (
The rotary mirror 27 controls the position of the light beam on the recording medium by controlling the rotation of the mirror 27.

Reference numeral 50 denotes a reading reflected light beam detector consisting of a photoelectric conversion element, which detects the presence or absence of recording based on the presence or absence of reflected light.

Reference numeral 34 denotes a detection reflected light beam detector composed of a photoelectric conversion element, which is composed of a first photodetector 35 and a second photodetector 36, and is arranged so that the objective lens 28 and the recording medium 21 are at a desired distance. It is arranged so that the reflected light beam for detection is incident on the boundary area, ie, the dividing line, between the first photodetector 35 and the second photodetector 36 when the detection light is maintained.

37 and 38 are first and second amplifiers, which amplify the outputs of the first and second photodetectors 35 and 36.

Differential amplifier 39, summing amplifier 40, and analog divider 41
is a circuit that obtains a differential output independent of the reflectance R of the recording medium 21, and inputs the outputs R(X) and R(Y) of the amplifiers 37 and 38 to the differential amplifier 39. to obtain the differential output A1Ft(X-Y), and input it to the summing amplifier 40 to obtain the addition output A2R(X+Y),
These are input to the analog divider 41, and the differential output A
, [((X-Y) is divided by the addition output A2R(X+Y), thereby causing the divider 41 to output $÷. Since I A2(X+Y)=K (constant), the reflectance R is This provides an unrelated differential output.

45 is a driving amplifier that amplifies the differential output and applies it to the moving coil 46.

FIG. 5 is an explanatory view of the movement mechanism of the objective lens 28.

As is clear from this drawing, the moving coil 46 to which the objective lens 28 is coupled is placed in the magnetic field of the permanent magnet 47, and when a current flows through the moving coil 46, the current value of the coil 46 and the objective lens 28 increases. It is configured to be displaced in accordance with.

FIG. 6 is an enlarged view of the optical system.

As is clear from this drawing, the reading light beam 48 projected from the laser light source 23 includes the first half mirror 24, the concave lens 42, the grating 43, the second half mirror 25, the λ polarizing plate 44, and the first mirror 26. is projected onto the disk recording medium 21 via the rotating mirror 27 and the objective lens 28,
The reflected light passes through the objective lens 28, rotating mirror 27, first mirror 26, upper λ polarizing plate 44, and second half mirror 25.
The light is detected by the photodetector 50 via.

On the other hand, the distance detection light beam 49 is transmitted to the first half mirror 2.
4, second mirror 29, auxiliary lens 30, third mirror 31, fourth mirror 32, second half mirror 25 and 1
The reflected light is projected onto the disk recording medium 21 via the λ polarizing plate 44, the first mirror 26, the rotary mirror 27, and the objective lens 28, and the reflected light is transmitted to the objective lens 28, the rotary mirror 27, and the first mirror 26. 4λ polarizing plate 44 and second half mirror
25 and the fifth mirror 33, the light is detected by the photodetector 34.

In this optical system, the reading light beam 48 has a focal length F
The light beam 48 passes through the optical axis (center axis) of the objective lens 28 and is projected onto the disk recording medium 21 in a focused state.

Further, the optical axis of the auxiliary lens 30 is the distance detection light beam 4.
9 is shifted by Xl in the X-axis direction and y in the Y-axis direction.
They are arranged so that they are shifted by l.

Therefore, the light beam 49 is incident on the objective lens 28 through point F' in FIG. 6, and is projected onto the disk recording medium 21 at a non-vertical incident angle.

The fact that the detection light beam 49 passes through point F' without passing through the focal point (F) and is incident on the recording medium 21 non-perpendicularly means that the detection light beam 49 is directed to a plane parallel to the lens 28 that includes the focal point F.
This means that the is incident in a non-orthogonal state.

The rotating mirror 27 is a mirror for tracking and interlaced scanning, and rotates around a pivot 27a to displace the light beam in the radial direction of the recording medium 21.

In this optical system, when the distance between the recording medium 21 and the objective lens 28 is at an optimum value, a reflected light beam 51 is obtained as shown in FIG.
It is irradiated on the dividing line between the two.

Further, when the recording medium 21 reaches the height Ha and approaches the objective lens 28, a reflected light beam 51a is obtained, and the beam irradiation area on the first photodetector 35 becomes larger than that on the second photodetector 3.
The beam irradiation area is larger than that in 6.

Further, when the recording medium 21 reaches a height Hb and is separated from the objective lens 28, a reflected light beam 51b is obtained, and the beam irradiation area on the second photodetector 36 is equal to that on the first photodetector 35. The area of the beam irradiated by

As a result, an electric signal having a signal component corresponding to the height of the recording medium 21, that is, the distance from the objective lens is transmitted to the photodetector 3.
It can be obtained from 4.

At this time, the reflected light beam 51 t 51 a t 5 l
b is displaced in the vertical direction in FIG. 6, but not in the horizontal direction.

Therefore, regardless of the main beam photodetector 50, the photodetector 34
can widen the dynamic range of

Furthermore, since the axis corresponding to the dividing line between the photodetectors 35 and 36 and the optical path of the reading light beam 48 are at the same height, the light beam 48 affects the photodetectors 35 and 36 under the same conditions, and the differential It becomes unrelated to the output.

In order to facilitate understanding of the optical system shown in FIG. 6, it will be described in more detail with reference to FIGS. 8, 9, and 10.

FIG. 8 shows the optical path when the lenses 28 and 30 are not arranged in the optical system.

In this case, the main light beam 48 is directed to the first half mirror 2
4, concave lens 42, grating 43, and second half mirror 25
and reaches the recording medium 21 via the first mirror 26 and the rotating mirror 27.

On the other hand, the detection light beam 49 is refracted by the first half mirror 24 and then passes through the second mirror 29, the third mirror 31, and the fourth mirror 32 to the second half mirror 25.
leading to.

This detection light beam 49 is incident on the second half mirror 25 in a state in which it is moved parallel to the optical path of the main light beam 48, and is projected onto the disk recording medium 21 at a predetermined distance from the main light beam 48. .

As shown in FIG. 8, if the lenses 28 and 30 are not provided, the detection light beam 49 would be perpendicularly incident on the disk recording medium 21, making it impossible to obtain reflected light corresponding to the distance between the objects. It is impossible to detect the distance between the lens 28 and the recording medium 21.

FIG. 9 shows the beam path when only the detection beam auxiliary lens 30, which is a convex lens having a focal position F, is arranged in addition to the objective lens 28.

However, the lens 30 is not placed in the final position shown in FIG.
The light path is aligned with the optical path of the

Therefore, in this state, the detection light beam 49 is
It passes through a position shifted by Xl in the X-axis direction from the optical axis of.

FIG. 10 shows a state in which an objective lens 28 is arranged in the optical system of FIG.

The objective lens 28 has its front focus at the focal point F of the lens 30.
, and the rear focal point is located approximately on the disk recording medium 21.

That is, the objective lens 28 is arranged so that the light beam 48 is focused on the recording medium 21 by the concave lens 42 and the objective lens 28 .

In this FIG. 10, the objective lens 28 is placed in the final position shown in FIG. 6, but the auxiliary lens 30 is not placed in the final position as in FIG.

In FIG. 10, the detection light beam 49 passes through the focal point F of the objective lens 28, so the light beam 49 that has passed through the focal point F passes through the objective lens 28 and then enters the main field, as shown in an enlarged view in FIG. The optical path of the light beam 4B, that is, the objective lens 28
parallel to the optical axis of

Therefore, the detection light beam 49 is vertically incident on the recording medium 21, and its reflected light also passes through the same optical path.

In the final optical system shown in FIG. 6, the auxiliary lens 30 in FIG. 10 is moved by yl in the Y-axis direction.

As a result, the focal position of the lens 30 becomes F', and the detection light beam 49 passing through this focal point F' is directed to the objective lens 28.
is refracted at a predetermined angle of incidence to the disk recording medium 21.
is incident on the

Therefore, when the height of the recording medium 21 changes, the optical path of the reflected light of the detection light beam 49 changes as shown in FIGS. 6 and 7, and the change in the distance between the objective lens 28 and the recording medium 21 causes the light This appears as a change in beam position on the detector 34, which is detected electrically.

According to the optical system shown in FIG. 6 described above, the lens 2 including the focal point F
Since the detection light beam 49 is incident non-orthogonally on a plane parallel to the recording medium 21, the reflected light beam is directed upwardly (vertically) in the vertical direction in FIG. The dynamic range of the photodetector 34 can be increased regardless of the deflection and the reading light beam 48.

In addition, since the height of the optical path corresponding to the dividing line between the photodetectors 35 and 36 and the optical path of the reading light beam 48 are the same, even if the reading light beam 48 influences the photodetectors 35 and 36, the height will be the same. It affects the conditions and becomes unrelated to the differential output.

In addition, since the focal point F' of the auxiliary lens 30 coincides with the plane (focal plane) containing the focal point F of the objective lens 28, the detection light beam 49 is focused at the focal point F', and the detection light beam 49 becomes a point light source. After the optical beam 49 passes through the objective lens 28, it becomes a parallel beam with a constant width, and a spot with a constant area can be projected regardless of the displacement of the recording medium 21.

Further, as is clear from FIG. 6, the detection reflected beam 51
．． 51 a and 5 l b on the rotating mirror 27 are set to occur on a line that is approximately parallel to the rotating wheel determined by the pivot axis 27 a of the rotating mirror, so that the rotation of the rotating mirror 27 This eliminates errors in displacement (interval) detection.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be further modified.

For example, the distance detection light beam 5 may be
13 or 14.

A in this figure 3, figure 12 - figure 14 is Y-Z of figure 2
This is a diagram in which the detection light beam 5 and its reflected light beams 6, 7, 8 are projected onto the same plane (corresponding to the front view of the device in FIG. 2), and B is the X-X in FIG. A detection light beam 5 and its reflected light beam 6.7 are placed on the same plane as the Z plane.
8 (corresponding to the plan view of the device in Figure 2)
It is.

Also in FIGS. 3 and 12 to 14, since the detection light beam 5 non-orthogonally traverses a position away from the optical axis in the focal plane, the reflected light corresponding to the change in the distance (focus) The changing direction of the beams 6, 7, 8 is a direction that does not intersect the optical axis (Z-axis).

Therefore, the dynamic range of interval (focus) detection can be expanded.

Further, the optical systems of the main light beam 48 and the detection light beam 49 may be modified.

Further, in the actual example, the objective lens 28 is configured to move, but the entire optical system may be moved, or the recording medium 28 may be moved.
1 may be moved.

In addition, in the actual case, the photodetector 34 is composed of two photodetectors 35 and 3.
6, but it may be configured by arranging more conversion elements.

It is also applicable to a device that reads information from a recording medium 21 in which signals other than bits are recorded.

Further, the distance may be largely adjusted by moving the entire optical device including the permanent magnet 47 and the like, and only fine adjustments may be made by moving the objective lens 28.

Moreover, it is applicable not only to playback devices but also to recording devices.

Further, the laser light source 23 may be shared by the reading light beam 48 and the detection light beam 49, or may be provided independently for each.

[Brief explanation of drawings]

FIG. 1 is an optical path diagram showing the principle of a conventional distance detection device, FIG. 2 is an optical path diagram showing the principle of an example of an optical recording/reproducing device having the distance detection device according to the present invention, and FIG. isy-
3B is a projection view on the X-Z plane, FIG. 4 is a block diagram showing an optical reproducing device according to one practical example of the present invention, and FIG. 5 is a schematic diagram of the objective lens moving mechanism. 6 is an explanatory diagram showing the relationship between each part of the optical system device, and FIG. 7 is a sectional view shown in FIG.
The figure is an explanatory diagram showing the reflection of the detection light beam; FIGS. FIG. 14 is a projection view showing a modified example. In addition, in the symbols used in the drawings, 1°1' is a reading light beam, 2 is a condenser lens, 3 is an optical axis, 4 is a recording medium, 5 is an interval detection light beam, 6, 7 8 is a reflection detection light beam, 9 is a photodetector, 10 is an error amplifier, 11 is an interval controller, 21 is a recording medium, 23 is a laser light source, 28
30 is a convex lens, 30 is an auxiliary convex lens, 34 is a reflection detection light beam detector, 35 is a first photodetector, 36 is a second photodetector, 46 is a moving coil, 48 is a reading light beam,
49 is a detection light beam, 50 is a photodetector, and 51 is a reflected detection light beam.

Claims (1)

[Claims] 1. A recording or reproducing light beam whose optical axis is arranged perpendicular to the recording medium and whose optical path coincides with the optical axis is arranged so as to be focused and projected onto the recording medium. a condenser lens; an interval detection light beam projected non-orthogonally onto the recording medium through the condenser lens in order to detect the interval between the condenser lens and the recording medium; and the interval detection light beam. arranged to detect a reflected light beam obtained by reflection on the recording medium after passing through the condenser lens, and based on a change in the position of the reflected light beam for distance detection corresponding to a change in the distance. A split-type photodetector configured to detect the interval; and an interval detection device for an optical recording or reproducing machine, wherein the optical path of the interval detection light beam is directed to the front focal point of the condensing lens. is set to cross a region of a plane perpendicular to the optical axis other than the optical axis in a non-orthogonal state, and the direction of change in the position of the reflected light beam for distance detection corresponding to the change in the distance is recorded as described above. Or optical recording, characterized in that the direction is set so as not to intersect the optical path of the reproducing light beam, and the split-type photodetector is arranged at a position away from the optical path of the recording or reproducing light beam. Or an interval detection device for a regenerator. 2. The distance detection light beam is a beam that crosses a straight line perpendicular to the optical axis on the plane non-orthogonally in an area other than the optical axis, and the photodetector is directed in the same direction as the straight line. Distance detection for an optical recording or reproducing machine according to claim 1, which is a split-type photodetector arranged parallel to the straight line so as to detect a change in the reflected light beam for interval detection. Device.