JPH02173937A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent a drop in the detecting performance of a focus error signal owing to a change in an ambient temperature by providing a reflecting optical element which spatially bisects a converging luminous flux and reflects them in the same direction and a multi-division photodetector with quadripartite light receiving areas. CONSTITUTION:When an objective lens 2 focuses an information recording medium 3, out of reflecting light and transmissive light generated by a convex lens 5a and a detecting element 6, a converting luminous flux passing through a reflecting optical element 7 forms two semi-circular light spots of the same size and the same direction in the quadripartite light receiving areas M of the multi-division photodetector 14. When the dividing line of the quadripartite light receiving areas is position-adjusted so that the incident luminous flux can be received in the uniform light quantity in the four light receiving areas M1 to M4, the quantity of light received in the quadripartite light receiving areas does not change when electrical signals arising in the light receiving areas in diagonal positions are summed, even if the quadripartite light receiving areas change in any directions of the dividing line owing to the change in ambient temperature, etc. Consequently, the output of a differential amplifier obtained by taking the difference between the sums, that is, the focus error signal 15 maintains always the stable detection ability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording/reproducing apparatus that records and reproduces information by irradiating a recording medium with a light beam such as a laser beam.

Conventional Technology The modern era is said to be the information age, and the development of high-density, large-capacity memory, which forms the core of this era, is actively underway. The capabilities required of memory include high density, large capacity, high reliability, high speed access, etc., and optical disk memory is attracting attention as a memory that satisfies these requirements.

Optical disk memory has the major feature of not damaging the recording medium because it uses a non-contact recording/playback method. A tracking servo system is required to follow the track.

The optical head requires a function to detect focus errors and tracking errors between the information recording medium and the objective lens, and an objective lens actuator for driving the objective lens to perform focus servo 7 tracking servo. This relates to an optical recording/reproducing device that achieves the former focus and tracking error detection function.

Traditionally, technology related to error detection, especially focus
There have been many reports regarding error detection, but -
For example, there is Japanese Patent Application Laid-Open No. 59-60739.

Hereinafter, the conventional focus error detection device as described above will be explained as part of error detection with reference to the drawings.

FIG. 8 is a schematic configuration diagram of a conventional focus error detection device and a diagram illustrating its operating principle. In Figure 8, 1
is a light source, 2 is an objective lens, 3 is an information recording medium, 4 is a half mirror, 15 is a convex lens, 8 is a differential amplifier, 9 is a knife, 10 is a two-split photodetector, 11 is a dividing line, and 12 is a light spot. be.

The operation of the conventional example configured as described above will be explained below.

After the light emitted from the light at is reflected by the half mirror 4,
The objective lens 2 focuses the light onto the information recording medium 3.

FIG. 8(A) shows a case where the objective lens 2 is focused on the information recording medium 3. At this time, the reflected light from the information recording medium 3 follows the opposite path, passes through the half mirror 4, and is converged by the convex lens 4, but half of the converged light beam is blocked by the knife 9, and the remaining light beam is
A light spot 12 is formed on the dividing line 11 of the two-split photodetector 10. By taking the difference between the electrical signals generated in each light receiving area of the two-split photodetector 10 using the differential amplifier 8,
Although it is possible to obtain a focus error signal, the focus error signal shown in Fig. 8 (A
), the focus error signal is zero.

FIG. 8 CB) shows a case where the information recording medium 3 is displaced in a direction away from the objective lens 2. At this time, after the reflected light from the information recording medium 3 passes through the objective lens 2, it becomes a convergent light compared to the case of FIG. A semicircular light spot 12 is formed, and the focus error signal obtained by the differential amplifier 8 is negative.

FIG. 8(C) shows a case where the information recording medium 3 is displaced in a direction approaching the objective lens 2. At this time, information recording medium 3
After the reflected light passes through the objective lens 2, it becomes a light beam 11 that is different from the case shown in FIG. A light spot 12 is formed, and a positive focus error signal is obtained by the differential amplifier 8.

Problems to be Solved by the Invention However, in the above configuration, 50% of the light amount is lost due to the knife 9.

Furthermore, it is susceptible to relative displacement between the optical head components due to temperature changes, etc., and has the problem of not being able to obtain a stable focus error signal. This will be explained using FIG. 9. FIG. 9(A) shows only the photodetector portion of FIG. 8(A), and the numbers and names correspond to those in FIG. 8. FIG. 9(A) shows the case when focusing, and the focus error signal obtained by the differential amplifier 8 is zero. FIG. 9(B) shows that due to changes in environmental temperature, etc., the two-split photodetector 1
0 indicates a slight displacement in the direction of the arrow.

13 is the position of the dividing line before displacement, and it is assumed that the position of the light spot 12 remains unchanged. In this case, since light is incident only on the light receiving area, the focus error signal, which should originally be zero, becomes negative. In other words, if the position of the two-split photodetector 10 is slightly displaced due to factors such as temperature changes, it is impossible to obtain a positive focus error signal, making it impossible to record and reproduce stable information. .

Moreover, the two-split photodetector 10 detects only the focus error signal, and in order to detect the tracking error signal, a different photodetector for detecting the trunking error signal must be newly arranged. It had a drawback.

The present invention has been made in view of the above-mentioned prior art, and is capable of suppressing a decrease in detection ability of focus error signals caused by minute displacement of the photodetector due to changes in environmental temperature, etc., using a single multi-segment photodetector. Along with providing focus error detection,
It is an object of the present invention to provide an optical recording/reproducing device that can also detect tracking errors.

Means for Solving the Problems To achieve this object, the optical recording and reproducing apparatus of the present invention comprises:
A light source and the light from the light source are focused onto an information recording medium,
an objective lens that forms an optical band; a separation means that is located between the objective lens and the light source and separates light that has been reflected by the information recording medium and transmitted through the objective lens; and a convex lens that converges the light separated by the separation means. A detection means is located in the convergent light beam produced by the convex lens and separates the convergent light beam into substantially perpendicular reflected light and transmitted light; a reflective optical element that is located in a convergent light beam, spatially divides the separated convergent light beam into two and reflects the separated convergent light beam in approximately the same direction; and an information recording medium. A single multi-segment photodetector into which reflected light from the object enters, and when the objective lens is focused on the information recording medium, the separated convergent light beam created by the convex lens and the detection element and the The reflective optical element is located at an intermediate position in the optical axis direction of the two focal points formed by the reflective optical element, one dividing line is in the same plane as the stepped surface of the reflective optical element, and 4
A four-division light-receiving area has a substantially cross-shaped dividing line that receives the light intensity of two light spots almost uniformly in one light-receiving area, and the reflected light and transmitted light separated by the detection element pass through the reflective optical element. a multi-segment photodetector having a light-receiving area for tracking error signal detection that is located at a different position from the four-division light-receiving area, in which the convergent light beam that is not present enters a position different from the two light spots; A first differential sensor which electrically connects diagonally located light receiving areas among the four divided light receiving areas of this multi-segment photodetector to calculate the sum, and calculates the difference between each electric signal obtained by taking the sum. It is characterized by comprising an amplifier and a second amplifier that detects an electrical signal generated from the light receiving area for detecting the trunking error signal of the multi-division photodetector as a tracking error signal.

Effect of the present invention With the above-described configuration, when the objective lens is focused on the information recording medium, out of the reflected light and transmitted light generated by the convex lens and the detection element, a convergent light flux passing through the reflective optical element is used to Two semicircular light spots of the same size and in the same direction are formed on the four-division light-receiving area of the multi-division photodetector. Furthermore, if you adjust the position of the dividing line of the four light-receiving areas so that the scene of the incident light beam is almost uniformly received in the four light-receiving areas. Even if the amount of light received by the four light-receiving areas changes in the direction of 〇The output of the differential amplifier, that is, the focus error signal, always maintains stable detection ability.

On the other hand, of the reflected light and transmitted light separated by the detection element, the convergent light flux that does not pass through the reflective optical element enters the light receiving area of the multi-segment photodetector for tracking error signal detection, and is generated from this light receiving area. A tracking error signal can be obtained as the output of the second amplifier.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of an optical recording/reproducing apparatus according to an embodiment of the present invention.

In FIG. 1, 1 is a light source, 2 is an objective lens, 3 is an information recording medium, and 4 is a half mirror, which are the same as those of the conventional example. 5a is a convex lens, 6 is a polarizing beam splitter which is a detection element, 7 is a reflective optical element, 14 is 6
This is a split photodetector, and for convenience, a view in the direction of arrow G is also shown. Further, 15°16 is a differential amplifier.

The reflective optical element 7 is located in the reflected light beam of the polarization beam splitter 6 with convergent light from the convex lens 5a, and is configured to spatially split the convergent light beam into two and reflect the same in approximately the same direction. It consists of a reflective plane with a constant ratio.

In this embodiment, two reflective planes of the reflective optical element 7 having a step and having the same reflectance have at least a predetermined angle α that is not parallel. The predetermined angle α is determined by the two light spots (T) formed by the reflective optical element 7 in the 6-split photodetector 14.

The sum of the areas of two diagonally located light receiving regions (M l +M3.M2+M
4) and the area of each light-receiving region (Nl, N
2) are set to be approximately equal.

FIG. 2 shows a convex lens 5a, a detection element 6, and a reflective optical element 7.
．． A perspective view of a six-divided photodetector 14 is shown. As shown in FIG. 2, the reflective optical element consists of two reflective surfaces, a reflective surface E and a reflective surface F.

FIG. 1 shows a case where the objective lens 2 is focused on the information recording medium 3, and the light beam converged by the convex lens 5a is separated into reflected light and transmitted light by the polarizing beam splitter 6. The light is reflected by the reflective surface E of the reflective optical element 7.
And after being divided into two by the reflecting surface F, it is reflected with an optical path difference,
Connect the focal point P and the non-focal point, respectively.

The light-receiving surface of the 6-split photodetector 14 is installed approximately perpendicular to the incident optical axis at an intermediate position between the focal point P and the non-focal point. As a result, two semicircular optical slots T and S of the same size and in the same direction are formed on the four-division light receiving area M of the six-division photodetector 14. Furthermore, the dividing line of the four-divided light-receiving area M is aligned in the X direction within the light-receiving surface so that the four light-receiving areas of the four-divided light-receiving area M of the six-divided photodetector 14 receive the amount of incident light almost uniformly. Adjust the position. here 6
Of the electrical signals generated in the four light receiving regions of the four-divided light receiving region M of the divided light detection 2S14, the sum of the electrical signals generated from the diagonally located light receiving regions (Ml+M3.M2+M4) is calculated, and the difference between the sums is calculated. The configuration is such that a focus error signal is obtained by taking the difference in a No. 10 differential amplifier 15. Note that the light receiving surface of the 6-split light detection 814 is a congruent 2
If two semicircular light beams (T and S) are formed, they do not have to be substantially perpendicular to the incident optical axis, and there is a degree of freedom in design.

Furthermore, among the light beams converged by the convex lens 5a,
The transmitted light of the polarizing beam splitter 6 is transmitted through a 6-split photodetector 14, which is an example of trunking error signal detection, and focuses R when the objective lens 2 is focused on the trunk of the information recording medium 3. The light-receiving surface of the two-divided light-receiving region N is installed so that it is substantially perpendicular to the incident optical axis and the dividing line is parallel to the track direction. As a result, one circular optical sub-bont U is formed on the two-divided light-receiving area N of the six-divided photodetector 14. Furthermore, the position of the dividing line of the two light-receiving regions N is adjusted in the Y direction so that the two light-receiving regions receive an almost uniform amount of incident light flux (.Here, each of the two light-receiving regions N ( By taking the difference between the electrical signals generated by N1 and N2) in the second differential amplifier 15, a tracking error signal is obtained by a so-called push-pull method. The light receiving surface does not have to be perpendicular to the incident optical axis as long as the light spot U is formed, and has a degree of freedom in design.

The operation of an embodiment of the optical recording/reproducing apparatus configured as described above will be explained below.

This embodiment achieves focus error detection and tracking error detection, but for convenience, each is separated and
The operation will be explained.

First, we will explain the operation of focus error detection, as shown in Figure 3 (
A5 indicates the positional relationship between the convex lens 5a and the polarizing beam splitter 6.6-divided photodetector 14 when the objective lens is focused, as in the case of FIG. FIG. 3(B) is a view taken along arrow G in FIG. 3(A), and the same applies to FIGS. 4 and 5 below.

At this time, two light spots S and T with the same amount of light are formed in the four-divided light receiving area M on the six-divided photodetector 14 in a semicircular shape, congruently, in the same direction, and four light receiving areas M. The focus error signal output obtained by the differential amplifier A 1-5 is zero because it is adjusted and set in the X direction so that the amount of light incident on the area is equal.

FIG. 4 shows a case where the information recording medium 3 in FIG. 1 is displaced in a direction away from the objective lens 2, and converged light is incident on the convex lens 5'a compared to the case in FIG. do. As a result, the two convergence points formed by the convex lens 5a both approach the polarizing beam splitter 6 (shift in the direction), and on the 6-split photodetector 14, as shown in the direction of arrow G in FIG. 4(B), Light spots S and T are formed.

At this time, the output of the differential amplifier A15 is unbalanced,
A positive focus error signal can be detected.

FIG. 5 shows a case where the information recording medium 3 in FIG. 1 is displaced in a direction closer to the objective lens 2, and light that is more divergent than in the case of FIG. 3 enters the convex lens 5a. As a result, the two convergence points due to the convex lens 5a are
Both are shifted away from the polarization beam brick 6, and light spots S and T are formed on the six-split photodetector 14 as shown in FIG. 5(B). At this time, a negative focus error signal can be detected from the output of the differential amplifier A15.

Figure 6 shows the information recording medium 3 as in Figures 1 and 3.
2 shows a case where the 6-split photodetector 14 is slightly displaced in the direction of the arrow H while the objective lens 2 is in focus. In addition, in FIG. 6, for convenience, 4 of the 6-divided photodetector 14
Only the divided light-receiving areas M are illustrated. Reference numeral 17 indicates a dividing line in one direction of the four-divided light-receiving region M, and reference numeral 18, indicated by a broken line, indicates a dividing line before the dividing line 17 is displaced. Before displacement, the light receiving areas Ml, M2 . M3. The amount of light received by M4 was the same, but after displacement, the light receiving area Ml.

M3 decreases, light receiving area M2. It increases in M4.

However, since the light spots S and T have the same shape, the same direction, and the same light amount, the light amount decreased in the light receiving area M1, that is, the light amount increased in the light receiving area M2, and the light amount increased in the light receiving area M3.
The amount of light decreased in the light receiving area M4, that is, the amount of light increased in the light receiving area M4 is equal. Therefore, the sum of the electrical signals detected in the light-receiving regions Ml and M4 and the sum of the electrical signals detected in the light-receiving regions M2 and M4 are both unchanged compared to before the slight displacement of the four-divided light-receiving region M, and the differential amplifier The focus error signal obtained by A15 is zero, and the 6-divided photodetector 14
is not affected by the displacement of

Next, the operation of tracking error signal detection will be explained.

In FIG. 3, among the light beams converged by the convex lens 5a, the light transmitted through the polarizing beam splitter 6 focuses at a focus R when the objective lens 2 is focused on the track of the information recording medium 3. As a result, one circular optical slot (U) is formed on the two-divided light-receiving area N of the six-divided photodetector 14. The dividing line of the two-divided light-receiving area N is set so as to be parallel to the track direction of the information recording medium 3, and the two-divided light-receiving area N is divided so that the two light-receiving areas receive a substantially uniform amount of incident light beam. Adjust the position of the line in the Y direction. Here, each of the two divided light receiving areas N (Nl,
A tracking error signal can be obtained by the so-called push-pull method by taking the difference between the electrical signals generated by the intensity of light incident on the second differential amplifier B16.

As described above, according to this embodiment, when the objective lens 2 is focused on the information recording medium 3, the convex lens 5a
The convergent beam of reflected light that has passed through the polarizing beam splitter 6 is reflected by the reflective optical element 77, forming two semicircular light spots T of the same size and in the same direction on the four-divided light receiving area M of the six-divided photodetector 14. .

form S. Furthermore, four light-receiving areas (Ml to M4)
so that the amount of incident light is received almost uniformly at
The position of the dividing line of the four-divided light-receiving area M is adjusted. Furthermore, the sum of electrical signals (Ml
+M3. By taking M2+M4) and calculating the difference between the sums using the first differential amplifier A15, there is no light loss (
Even if the four-division light receiving area M changes in either direction of the dividing line due to environmental temperature changes, it is possible to detect a focus error signal that maintains stable detection ability and is not affected by this change. It is possible.

And, due to the transmitted light convergence flux of the polarized beam splinterf, on the 2-divided light receiving area N of the 6-divided photodetector 14,
One circular optical slot 7)U is formed. moreover,
The dividing line of the two-divided light-receiving area N is installed so as to be parallel to the trunk direction of the information recording medium 3, and the two-divided light-receiving area N is divided so that the light intensity of the incident light beam is almost uniformly received in the two light-receiving areas. The lines are aligned in the Y direction, and therefore, the second differential amplifier B16 calculates the difference in electrical signals generated by the intensity of light incident on each of the two divided light-receiving areas N (Nl, N2). As a result, a tracking error signal can be obtained by a so-called push-pull method.

That is, focus error signal detection and tracking error signal detection are realized by one 6-split photodetector.

Note that in this embodiment, a polarizing beam splitter is used as the detection element 6. Therefore, when the information recording medium 3 is a magneto-optical disk, there is an effect unique to this embodiment in that a magneto-optical information signal can be obtained from the electrical signal of the six-divided photodetector 14.

Furthermore, in this embodiment, the two reflective planes of the reflective optical element 7 having a step and having the same reflectance have at least a predetermined angle α that is not parallel. The predetermined angle α is made up of four light-receiving regions of approximately the same area in the 6-split photodetector 14, into which the two light spots (T, S) formed by the reflective optical element 7 enter with approximately uniform light intensity. The sum of the areas of the two diagonally located light receiving areas (M1+M3.M2+M4) out of the four-divided light receiving area M, and the two areas having approximately the same area where the convergent light flux that is the transmitted light from the polarizing beam splitter 6 is incident. The area (N1, N2) of each of the two divided light receiving regions N consisting of light receiving regions is set to be approximately equal.

Therefore, the area of the light receiving area that generates the focus error signal and the tracking error signal becomes equal ((M1
+M3)=(M2+M4)=(Nl)-(N2)),
Therefore, the light receiving sensitivity characteristics and response characteristics of the focus error signal and tracking error signal.

All frequency characteristics are equal, stable and good error signal detection,
This embodiment has an advantage that information signal detection can be realized.

Next, other embodiments of the present invention will be described with reference to the drawings. FIG. 7 is a schematic configuration diagram of main parts in another embodiment of the present invention, showing a convex lens 5a.

The polarizing beam splinter 6 and the reflective optical element 7 are the same as those in the embodiment shown in FIG.

FIG. 7(A) shows a configuration in which a polarizing beam splinter 6 and a reflective optical element 7 are integrated, and the two reflective surfaces of the reflective optical element 7 are both total reflection surfaces.

FIG. 7(B) shows the polarizing beam splitter 6 and the convex lens 5.
A is optically bonded or integrated with a.

In FIG. 7(C), the polarizing beam splitter 6 and the reflective optical element 7 are integrated, and the polarizing beam splitter 6 and the convex lens 5a are optically bonded or integrated.
The two reflective surfaces of the reflective optical element 7 are both total reflection surfaces.

7(A), 7(B), and 7(C) are all composites of the respective elements shown in FIG. Operation of the embodiment,
The effect is the same.

Furthermore, in the case of the embodiments shown in Figures 7 (A), (B), and (C), each element is composited, so it is possible to centralize the adjustment points and make the optical head smaller and lighter. This embodiment has effects specific to the embodiment.

In the above embodiments, the push-pull method was used as the tracking error signal detection means, but even if other tracking error signal detection means are used, a single multi-segment photodetector can detect the focus error signal and trunking. It goes without saying that the same effects as the present invention can be obtained if the error signal is also detected.

Effects of the Invention The present invention is an optical recording/reproducing device, in which when an objective lens is focused on an information recording medium, out of reflected light and transmitted light generated by a convex lens and a detection element, the light that passes through the reflective optical element is Two semicircular light spots of the same size and in the same direction are formed on the four-division light receiving area of the multi-division photodetector by the convergent light beam.

Furthermore, if you adjust the position of the dividing line of the four light receiving areas so that the amount of incident light flux is almost uniformly received in the four light receiving areas, the light! There is no loss, and even if the four-divided light-receiving area changes in either direction of the dividing line due to environmental temperature changes, the amount of light received by the four light-receiving areas will be equal to the electrical signal generated from the diagonally located light-receiving areas. If the sum is taken, there is no change, and the output of the first differential amplifier obtained by taking the difference between the phases, that is, the focus error signal, always maintains a stable detection ability.

On the other hand, of the reflected light and transmitted light separated by the detection element, the convergent light flux that does not pass through the reflective optical element enters the light receiving area of the multi-segment photodetector for tracking error signal detection, and is generated from this light receiving area. A tracking error signal can be obtained as the output of the second amplifier.

In addition, a multi-division photodetector is used to detect focus error signals.
The convergent light flux that does not pass through the reflective optical element among the reflected light and transmitted light separated by the detection element and the 4-split light receiving area is incident on a position different from the two light spots on the 4-split light receiving area, A light-receiving area that exists in a different position from this four-division light-receiving area, and has one dividing line that allows the two light-receiving areas to almost uniformly receive the amount of incident light flux, and is used as a light-receiving area for tracking error signal detection. In the case of a 6-divided photodetector having a 2-divided light receiving area,
Tracking error signal detection can be achieved by push-pull method.

Next, when a polarizing beam splitter is used as a detection element, a magneto-optical information signal can be obtained from an electric signal of a multi-division photodetector when the information recording medium is a magneto-optical disk.

Further, the two reflective planes having the same reflectance and having a step in the reflective optical element have at least a predetermined angle α that is not parallel, and the angle α is determined by the 6-segment photodetector that detects the tracking error signal using the push-pull method. , two light spots are incident, and the sum of the areas of two light receiving areas at diagonal positions among the four-division light receiving areas where focus error signal detection is performed, and one light spot is incident, and tracking is calculated. When the area of each of the two divided light receiving areas for error signal detection is set to be approximately equal, the light receiving sensitivity characteristics and response characteristics of the focus error signal and the tracking error signal.

All frequency characteristics are equal, stable and good error signal detection,
Information signal detection can be achieved.

Moreover, a device that integrates a detection element and a reflective optical element,
When a detection element and a convex lens are optically bonded or integrated, or a detection element and a reflective optical element are integrated, and a detection element and a convex lens 5a are optically bonded or integrated, each element is combined. As a result, it is possible to realize an excellent optical recording/reproducing device in which adjustment points can be concentrated and the optical head can be made smaller and lighter.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an optical recording and reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a perspective view of main parts of an optical recording and reproducing apparatus according to an embodiment of the present invention, and FIGS. 5 and 6 are configuration diagrams for explaining the operation of the main parts of an optical recording and reproducing apparatus according to one embodiment of the present invention, and FIG. 7 is a schematic diagram of an optical recording and reproducing apparatus according to another embodiment of the present invention. Part configuration diagram, Figure 8,
FIG. 9 is a schematic diagram for explaining the configuration and operation of a conventional focus error detection device. 1...Light source, 2...Objective lens, 3.
... Information recording medium, 4 ... Half mirror
15, 5a... Convex lens, 6... Polarizing beam splitter, 7... Reflective optical element, 8,
15.16... Differential amplifier, 9... Naifetsuji, 10.14... Photodetector, 1113.
17°18...Dividing line, 12...Hikari bonto. Name of agent: Patent attorney Shigetaka Awano (1 person)

Claims (7)

[Claims] (1) a light source; an objective lens that focuses light from the light source onto an information recording medium to form a light spot; , a separating means for separating the light transmitted through the objective lens; a convex lens for converging the separated light by the separating means; and a convex lens located in the convergent light beam by the convex lens, and converting the convergent light beam into substantially perpendicular reflected light and transmitted light. a detection means for separating the reflected light and the transmitted light by the detection means, and a detection means located in the separated convergent light beam of either one of the reflected light and the transmitted light separated by the detection means, and spatially splits the separated convergent light beam into two.
a reflective optical element consisting of two reflective planes having the same reflectance and having a step, which are divided and reflected in approximately the same direction; and one multi-division photodetector into which reflected light from the information recording medium is incident. , when the objective lens is focused on the information recording medium, two focal points are formed by the separated convergent light beam created by the convex lens and the detection element and the reflective optical element. It is located at an intermediate position in the optical axis direction, one dividing line is in the same plane as the stepped surface of the reflective optical element, and has a substantially cross shape that receives almost uniform amounts of light from the two light spots in the four light receiving areas. A four-division light-receiving area having a dividing line, and a convergent light beam of the reflected light and transmitted light separated by the detection element that does not pass through the reflective optical element enters a position different from the two light spots. , a multi-segment photodetector having a light-receiving area for tracking error signal detection located at a different position from the four-segment light-receiving area; and the four-segment light-receiving area of the multi-segment photodetector.
A first differential amplifier that electrically connects diagonally located light receiving areas among the divided light receiving areas, calculates the sum, and calculates the difference between the summed electric signals; and the multi-split light detection. and a second amplifier for detecting an electric signal generated from the light receiving area for detecting the tracking error signal of the device as a tracking error signal. (2) When the objective lens is focused on the information recording medium, a multi-segment photodetector is configured to form a convergent light beam created by a convex lens and a detection element and separated by a reflective optical element. It is located at the middle position in the optical axis direction of the two focal points, and
A four-division light-receiving area having a substantially cross-shaped dividing line in which the dividing line of the book is in the same plane as the step surface of the reflective optical element, and the four light-receiving areas receive almost uniform amounts of light from the two light spots; , and of the reflected light and transmitted light separated by the detection element, the convergent light flux that does not pass through the reflective optical element enters a position different from the two light spots, and is different from the four-division light receiving area. and a two-divided light-receiving area as a light-receiving area for tracking error signal detection, the light-receiving area existing at the position having one dividing line that allows the two light-receiving areas to almost uniformly receive the light intensity of the incident light beam. It is characterized in that it is a 6-divided photodetector, and the light-receiving areas at diagonal positions among the 4-divided light-receiving areas of the 6-divided photodetector are electrically connected and the sum is calculated. A first differential amplifier and a second amplifier calculate the difference between the electric signals of the two divided light receiving areas for detecting the tracking error signal of the six divided photodetector. 2. The optical recording/reproducing apparatus according to claim 1, wherein the optical recording/reproducing apparatus is a second differential amplifier. (3) The two reflective planes of the reflective optical element having a step and having the same reflectance have at least a predetermined angle that is not parallel;
The predetermined angle is defined by four light-receiving areas of approximately the same area in which the two light spots formed by the reflective optical element are incident with a substantially uniform amount of light in the 6-split photodetector.
The sum of the areas of two diagonally located light receiving regions among the divided light receiving regions, and the sum of the areas of the two light receiving regions located at diagonal positions, and the two light receiving regions consisting of two light receiving regions of approximately the same area into which the convergent light flux that does not pass through the reflective optical element is incident. 3. The optical recording/reproducing apparatus according to claim 2, wherein the areas of the respective light-receiving areas are set to be approximately equal. (4) The optical recording/reproducing apparatus according to claim (1), wherein the detection element is a polarizing beam splitter. (5) Claim in which the detection element and the reflective optical element are integrated (
1) The optical recording/reproducing device described above. (6) The optical recording/reproducing device according to claim (1), wherein the convex lens and the detection element are optically bonded or integrated. (7) The optical recording/reproducing device according to claim (1), wherein the detection element and the reflective optical element are integrated, and the detection element and the convex lens are optically bonded or integrated.