JPH08161761A - Detection device of focus error - Google Patents

Abstract

PURPOSE: To enhance the safety and the detection sensitivity with reference to a change in a wavelength of a light-emitting means, to miniaturize a device and to increase the safety of the start of a servo operation in the device by which light from the light-emitting means is image-formed in an image formation means and by which a focus error is detected on the basis of its reflected light. CONSTITUTION: Light which is emitted from a laser diode 101 and which is condensed on an optical disk 106 as an image formation object by a lens 105 is reflected by a polarization beam splitter 103, and it is branched into two luminous fluxes by a transmission reflecting plate 1 while it is being condensed by a lens 107. Spots by the respective luminous fluxes are formed to be fan shapes whose foci have been made to agree, the spots are received and operated in a state that they are stretched between adjacent light-receiving regions in photodiodes 3, 4, and a focus detection error is detected.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a compact disc,
Focus error detection for detecting an error in the focus position of an optical image formed in an optical system used in an optical device such as a recording / reproducing device such as a magneto-optical disc or a phase change optical disc, or an exposure device for a semiconductor wafer. A method and a detection device.

[0002]

2. Description of the Related Art Conventionally, as a focus error detecting technique of this kind, a system in which a circular light beam formed by an optical system, that is, a size of an optical image is detected by a light receiving element or the like to detect a focus error. Is proposed. For example, the focus error detection device shown in FIG. 19 is a device that separates two light beams from a light beam reflected by an imaging target and detects a focus error by providing light receiving means before and after the focus of these lights. is there.

The focus error detecting device of FIG. 19 is disclosed in Japanese Patent Laid-Open No. 61-59630, and linearly polarized light emitted from the laser diode 101 is converted into parallel light by the collimator lens 102. , Is transmitted through the polarization beam splitter 103, and is converted into circularly polarized light by the quarter-wave plate 104. Then, the light focused on the optical disc 106 by the objective lens 105 is reflected by the surface of the optical disc 106, travels in the same optical path in the opposite direction, and is transmitted to the quarter wavelength plate 104.
Is converted into linearly polarized light again. Round-trip quarter wave plate 1
The light that has passed through 04 twice is reflected by the polarization beam splitter 103 and is converted into convergent light by the collimator lens 107 because the direction of the linearly polarized light is rotated by 90 ° in the forward path and the backward path. Therefore, the converged light is reflected by the beam splitter 108.
Is divided into two, and the light is received by the photodiode 109 placed in front of the focus on the optical axis and the photodiode 110 placed behind the focus on the optical axis.

These photodiodes 109,
The focus error signal and the track error signal on the optical disc are obtained from the signal obtained from 110. The focus error signal is an error in the optical axis direction between the light condensed by the objective lens 105 and the optical disk surface, and the track error signal is an error in the direction perpendicular to the optical axis.

As shown in FIG. 20, the photodiode 109 has a light receiving surface as a photoelectric conversion portion divided into three parts. A region 109b is provided at a central position corresponding to the optical axis, and regions 109a and 109c are provided on both sides thereof. Is provided, and an electromotive current proportional to the intensity of light, that is, the area where the light is received is generated in each region. Similarly, the photodiode 110 also includes regions 110a, 110b, and 110c.

Further, FIG. 3 shows the relationship between the spot 111 formed on the photodiode 109 and the signal obtained from the area of each photoelectric conversion portion when the optical disk 106 is out of focus. Here, the electromotive current S10 output from each region 109a to 109c of the photodiode 109 is
The output OUT109 is obtained by calculating 9a to S109c. Here, OUT109 = -S109a + S10
9b-S109c.

Similarly, the output O obtained by calculating the electromotive currents S110a to 110c of the spot 112 formed on the photodiode 110 and the respective regions 110a to 110c thereof.
The relationship of UT110 = -S110a + S110b-S110c is shown.

Therefore, as shown in FIG.
One output, here, the output −OUT109 in which the output OUT110 is a negative value is obtained, and then this negative value is output to the other OUT.
21B, the focus error signal (-S109a + S109b-S109) is added as shown in FIG.
c)-(-S110a + S110b-S110c) can be obtained. The track error signal is obtained from S109a-S109c by the push-pull method.

Further, the conventional focus error detecting device shown in FIG. 22 is disclosed in Japanese Patent Laid-Open No. 63-22964, and the light emitted from the laser diode 101 is
The light is focused on the optical disc 106 by the lens 115, reflected by the optical disc 106, travels in the same optical path in the opposite direction, and is diffracted by the hologram optical element 114. The diffracted light of the hologram optical element 114 focuses on the front side of the photodiode 116 and the rear side of the photodiode 117.

Also in the photodiodes 116 and 117, the photoelectric conversion portion is composed of three regions 116a to 116c and 117a to 117c as in the case shown in FIG. 20, and the electromotive current from each region is calculated. A focus error signal is obtained. That is, in this case, (-S116
a + S116b-S116c)-(-S117a + S1
17b-S117c). The track error signal is (S116a-S116c)-(S117a
-S117c).

[0011]

In the conventional focus error detecting device as described above, the photodiode 10 described above is used.
As shown in FIG. 23A, a photodiode 120 having a wide central region of the photoelectric conversion unit and a narrow width of both side regions is denoted as 9, 110 or 116, 117, and FIG.
As described above, the focus error signal when using the photodiode 121 in which the width of the central region is narrow and the width of the regions on both sides is wide is considered.

In FIG. 1C, a spot 122 formed on the photodiode 120 or 121 and its output OUT120 (= -S120) when the optical disk 106 is out of plane.
a + S120b-S120c), OUT122 (= -S)
121a + S121b-S121c). Here, S120a, S120b, and S120c are the regions 120 of the photoelectric conversion unit of the photodiode 120, respectively.
a, 120b, 120c, and S121a,
S121b and S121c are electromotive currents in the respective regions 121a, 121b and 121c of the photoelectric conversion part of the photodiode 121.

Generally, in a focus error detection device, in order to maximize the focus error detection sensitivity, the output of the photodiode is zero when the light condensed by the lens is focused in the very vicinity of the optical disk surface. Designed to be. That is, in the case of the photodiodes 120 and 121, the respective outputs OUT120 and OUT121 are designed to be zero. Therefore, as shown in FIG.
As can be seen from (b), the size of the spot 122 on the photodiode 120 is
Must be larger than the size of the sbot 122 at.

In the focus error detection device of FIG. 22 described above, in order to enlarge the spot 122, a large lens power is applied to the hologram optical element 114 so that the front focus of the photodiode 116 is moved further forward, and the photodiode is moved forward. The rear focus of 117 needs to be moved further back. On the contrary, in order to reduce the spot 122, it is necessary to give a small lens power to the hologram optical element 114, move the front focus of the photodiode 116 backward, and move the rear focus of the photodiode 117 forward. is there.

However, in this type of focus error detection apparatus, the larger the lens power applied to the hologram optical element 114, the more susceptible it is to the wavelength fluctuation of the laser diode 101, and conversely, the hologram optical element. The smaller the lens power applied to 114, the less likely it is to be affected by the wavelength variation of the laser diode 101. Therefore, the photodiode 1
21 is less affected by the wavelength variation of the laser diode 101 than the photodiode 120 is used.

On the other hand, in the focus error detecting device of FIG. 19, in order to make the spot larger or smaller,
Move the photodiodes 109 and 110 back and forth,
The size of the spot 122 will be adjusted. However, even in this case, the photodiode 121
In the case of using, since the photodiode can be brought close to the focus, the focus error detecting device can be downsized as compared with the case of using the photodiode 120.

On the other hand, in each of the focus error detecting devices,
A pair of photodiodes 109 and 110, or 11
When the difference between the outputs of 6 and 117 is taken, a zero cross occurs even if the light condensed by the lens is not focused on the optical disk surface, and this becomes a pseudo zero cross. When such a pseudo zero cross occurs, the certainty of starting the servo operation is reduced. In this case, if the photodiode 120 of FIG. 23A is used as the above-mentioned photodiode pair, the zero-cross characteristic as shown in FIG. 24A is obtained, and if the photodiode 121 of FIG. It has a zero-cross characteristic as shown in b). As a result, the photodiode 120 becomes the photodiode 1
Since the positive amplitude is longer and the negative amplitude is smaller than that of No. 21, the defocus amount that causes the pseudo zero cross is large,
Moreover, since the reversal width becomes smaller, the trouble is less likely to occur.

As described above, in the conventional focus error detection device, when either one of the photodiodes 120 and 121 is set as the photodiode pair to be used, the stability of the light emitting means with respect to the wavelength variation and the focus error detection device. There is a problem that miniaturization and the reliability of the start of the servo operation cannot be achieved at the same time.

[0019]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a focus error detecting device which enhances the stability of the light emitting means with respect to wavelength fluctuation and enhances the focus error detection sensitivity. Also,
Another object of the present invention is to provide a focus error detection device that is more compact and has improved certainty in starting a servo operation.

[0020]

The first invention of the present invention is as follows:
A light emitting unit, a light collecting unit that collects the light emitted from the light emitting unit on an imaging target, and the light reflected by the imaging target is branched into at least two converged lights α and β. And a first light receiving unit located in front of the converging position of the one branched light, and a second light receiving unit located behind the converging position of the other branched light. The first
And each of the second light receiving means has three light receiving portions divided by a pair of substantially parallel line segments, and the spots of the respective branched light beams are formed into a pair of fan-shaped spots whose main points coincide with each other. Is located in the central light receiving portion and each spot intersects the line segment.

A second aspect of the present invention is directed to at least light emitting means, light condensing means for condensing light emitted from the light emitting means onto an image forming object, and light reflected by the image forming object. The branching means for branching the light into two convergent lights, the light α and the light β, the first light receiving means located in front of the convergent position of the one branched light, and the convergent position of the other branched light. And a second light receiving unit located rearward, each of the first and second light receiving units having three light receiving units divided by a pair of substantially parallel line segments, and each of the branched light beams. Each of the spots is in the form of a pair of fans whose main points face each other at a predetermined interval, the main points are located in the central light receiving section, and each spot intersects the line segment. .

Further, according to a third aspect of the present invention, at least light emitting means, light condensing means for condensing the light emitted from the light emitting means onto an image forming object, and light reflected by the image forming object are at least included. The branching means for branching the light into two convergent lights, the light α and the light β, the first light receiving means located in front of the convergent position of the one branched light, and the convergent position of the other branched light. And a second light receiving unit located rearward, each of the first and second light receiving units has two light receiving units divided by one line segment, and the spot of each branched light is Each is fan-shaped and intersects with the line segment.

[0023]

In the first aspect of the invention, since the spot of the light received by the light receiving means is fan-shaped and has the same essential points, the sensitivity of focus error detection is enhanced as compared with the conventional circular spot. That is, in FIG. 18, the light receiving means 5
Reference numeral 7 denotes a light receiving means according to the focus error detection device of the present invention, and a fan-shaped spot 58 is received here. Further, the light receiving means 123 is the light receiving means 1 according to the conventional focus error detection device, and the circular spot 124 is received there. Then, FIG. 7A shows the case where the image forming object is displaced from the focus of the light collecting means, and FIG. 11B shows the case where the light collecting means is focused on the image forming object. .

Here, the light receiving portions 57a, 5a of the light receiving means 57
7b and 57c electromotive current, and the light receiving portion 12 of the light receiving means 123.
The electromotive currents of 3a, 123b, and 123c are respectively changed to S5.
7a, S57b, S57c, S123a, S123b,
If it is S123c, T57 and T123 defined by T57≡-S57a + S57b-S57c T123≡-S123a + S123b-S123c can be considered as an index indicating the detection sensitivity of the focus error.

Therefore, letting r be the electromotive current generated when the total amount of light is incident on one light receiving portion, T57 = T123 = r in the case of FIG. 9A and approximately T57 in the case of FIG. = -0.3r and T123 = 0.2r.
That is, T57 changes more rapidly than T123. Therefore, it can be said that the focus error detection device of the present invention has higher focus error detection sensitivity than the conventional focus error detection device.

In the second invention, since the spots of light received by the light receiving means are fan-shaped and the main points thereof are separated from each other by a required dimension, the stability of the light emitting means with respect to the wavelength fluctuation and the focus error detecting device are improved. The miniaturization and the certainty of starting the servo operation are compatible with each other. That is, FIG. 19 shows the relationship between the focal point of the condensing means and the object to be imaged, the spots 60a and 60b formed on the light receiving means 59 according to the focus error detecting device of the present invention, and -S59a + S59b-S59c. . Here, S59a, S59b and S59c are
The light receiving portions 59a, 59b, 59 of the light receiving means 59, respectively.
It is the electromotive current of c.

Here, the center of the spot 60a and the dividing line 5
Since the distance of 9d is equal to the distance between the center of the spot 60b and the dividing line 59e, this is set to u, and the distance between the center of the spot 60a and the dividing line 59e is equal to the distance between the center of the spot 60b and the dividing line 59d. If w, u is w
As is clearer from the figure, the focus error detection device of the present invention has the same characteristics as the conventional focus error detection device in which the width of the central light receiving portion in the defocus amount region 61a is twice u. This shows the same characteristics as the conventional focus error detection device in which the width of the central light receiving portion in the defocus amount area 61b is twice w. In other words, it is possible to achieve both stability of the light emitting means with respect to wavelength fluctuations, downsizing of the focus error detection device, and reliability of starting the servo operation.

Here, if the apex angle of the spots 60a and 60b is set to less than 180 °, the focus error detection sensitivity is improved by the same operation as that of the focus error detection device of the first aspect of the present invention.

In the third invention, the shape of the spot received by the light receiving means is a fan shape, and this is received by the photodiode having two regions, whereby the stability of the light emitting means with respect to the wavelength fluctuation and the focus error detection. The miniaturization of the device and the certainty of starting the servo operation are compatible with each other. That is, FIG. 20 shows the shift between the focus of the condensing means and the image formation object, and the relationship between the spot 65 and -S64a + S64b connected to the light receiving means 64 according to the focus error detection device of the present invention.

Here, S64a and S64b are electromotive currents of the light receiving portions 64a and 64b of the light receiving means 64, respectively. Since the focus error detection device of the present invention can independently select the distance from the center of the spot 65 to the dividing line 64c and the distance from the center of the spot 65 to the edge 64d, the characteristics of the focus shift amount in the region 66a and the focus shift amount can be determined. The characteristics in the region 66b can be independently determined, and it is possible to achieve both stability with respect to wavelength variation of the light emitting means and miniaturization of the focus error detection device, and reliability of start of the servo operation.

Here, if the apex angle of the spot 65 is set to less than 180 °, the focus error detection sensitivity is improved by the same operation as that of the focus error detection device of the first aspect of the present invention.

[0032]

Next, an embodiment of the present invention will be described with reference to the drawings. 1st of the focus error detection apparatus of this invention (1st invention)
An embodiment will be described with reference to FIG. As shown in FIG. 4A, the linearly polarized light emitted from the laser diode 101 is converted into parallel light by the collimator lens 102, transmitted through the polarization beam splitter 103, and the quarter wavelength plate 104.
Is converted into circularly polarized light. The light condensed on the optical disk 106 by the objective lens 105 is reflected, travels in the same optical path in the opposite direction, and is converted again into linearly polarized light by the ¼ wavelength plate 104. The light transmitted through the quarter-wave plate 104 twice in this round trip is reflected by the polarization beam splitter 103 and converted into converged light by the collimator lens 107 because the direction of the linearly polarized light is rotated by 90 ° in the forward and backward paths. . Then, a part of the light is transmitted by the transflective plate 1, and another part is reflected.

As shown in FIG. 2B, the transflective plate 1 has a rectangular area divided into four regions by diagonal lines. The regions 1a and 1b facing each other reflect light, and the region 1c. The region 1d transmits light. Of the light divided into two by the transflective plate 1, the transmitted light is received by the photodiode 2 of the same figure (c) placed in front of the focal point,
The reflected light is received by the photodiode 3 shown in FIG.

Therefore, the light, which is formed by the collimator lens 107 into a circular light flux whose surface perpendicular to the optical axis is circular, is divided by the transflective plate 1 into regions 1a to 1d.
The cross-sectional shape of each of the divided luminous fluxes is a sector (1/4 circle), and the photodiodes 2 and 3 respectively receive the light.

Then, the focus error signal is the electromotive current of the photoelectric converters 2a, 2b, 2c of the photodiode 2,
The electromotive currents of the photoelectric conversion units 3a, 3b, 3c of the photodiode 3 are respectively changed to S2a, S2b, S2c, S3a, S
3b and S3c, -S2a + S2b-S2c + S
Obtained from 3a-S3b + S3c. Further, the track error signal is obtained from S2a-S2c.

A second embodiment of the focus error detection device of the present invention (first invention) will be described with reference to FIG. In FIG. 3A, the linearly polarized light emitted from the laser diode 101 is converted into parallel light by the collimator lens 102,
The quarter-wave plate 1 that is transmitted through the polarization beam splitter 103
At 04, it is converted into circularly polarized light. The light condensed on the optical disk 106 by the objective lens 105 is reflected, travels in the same optical path in the opposite direction, and is converted again into linearly polarized light by the ¼ wavelength plate 104. The light that has passed through the quarter-wave plate 104 twice in the forward and backward directions is reflected by the polarization beam splitter 103 and enters the complex curved lens 6 because the direction of the linearly polarized light is rotated by 90 ° in the forward and backward paths.

The compound curved lens 6 has a rectangular plane shape, and the plane portion is divided into six regions 6a to 6f by a diagonal line and one bisector, as shown in FIG. ing. Further, the regions 6a, 6b, 6e are separated by the bisector.
The areas 6c, 6d, and 6f form lenses having different focal lengths. As a result, as shown in FIG. 7C, the objective lens 105 is moved to the optical disc 10
When focusing on 6, areas 6a and 6b are aligned with optical axis 62
Is focused on the point 63a, and the regions 6c and 6d are focused on the point 63b on the optical axis 62.

The light transmitted through the compound curved lens 6 is received by the photodiode 7 provided between the points 63a and 63b. The photodiode 7 has a structure in which the light-receiving surface is largely divided into four as shown in FIG. 7D, and the two regions near the center are further divided into three. Therefore, the lights emitted from the regions 6e and 6f of the complex curved lens 6 are focused on the photoelectric conversion units 7g and 7h of the photodiode 7, respectively. The light emitted from the regions 6a and 6b is received by the photoelectric conversion units 7a, 7b, 7c,
The light emitted from the regions 6c and 6d is converted into the photoelectric conversion units 7d,
The light is received by 7e and 7f.

FIG. 3 shows the shape of the spot 8 formed on the photodiode 7. FIG. 3A shows the optical disc 106.
Is closer to the focus of the objective lens 105 (rear focus), FIG. 7B is when the objective lens 105 is focused on the optical disc 106 (focusing), and FIG.
Reference numeral 6 represents a time (front focus) farther than the focus of the objective lens 105. As is apparent from FIG. 3, the focus error signal is generated by the photoelectric conversion units 7a and 7b of the photodiode 7.
The electromotive currents of 7c, 7d, 7e, and 7f are changed to S7a,
If S7b, S7c, S7d, S7e, and S7f, then-
Obtained from S7a + S7b-S7c + S7d-S7e + S7f. The track error signal is obtained from S7g-S7h, where the electromotive currents of the photoelectric conversion units 7g and 7h of the photodiode 7 are S7g and S7h, respectively.

A third embodiment of the focus error detecting device of the present invention (first invention) will be described with reference to FIG. As shown in FIG. 4A, the light emitted from the laser diode 101 is
The light is transmitted through the hologram optical element 18, condensed by the lens 115 on the optical disk 106, reflected by the optical disk 106, travels in the same optical path in reverse, and is diffracted by the hologram optical element 18. The hologram optical element 18 is diffracted by the diffraction grating provided on the surface of the hologram optical element 18 when the hologram optical element 18 is transmitted from the left side to the right side of the drawing.

The hologram optical element 18 has four regions 18a, 18 formed by diagonal lines having a rectangular area as shown in FIG.
It is divided into areas 18a and 1d.
The + 1st-order diffracted light of 8b is focused on the front side of the photodiode 19, and the -1st-order diffracted light is focused on the rear side of the photodiode 20. The photodiode 19 receives the + 1st-order diffracted light at its photoelectric conversion units 19a, 19b, 19c as shown in FIG. 7C, and the photodiode 20 has its photoelectric conversion units 20a, 20b as shown in FIG. ，
The -1st order diffracted light is received at 20c. Further, the diffracted light of the region 18c of the hologram optical element 18 is condensed on the photoelectric conversion unit 19d of the photodiode 19 and the photoelectric conversion unit 20e of the photodiode 20, and the diffracted light of the region 18d of the hologram optical element 18 is reflected by the photodiode 20. The light is focused on the photoelectric conversion unit 20 d and the photoelectric conversion unit 19 e of the photodiode 19.

Therefore, the electromotive currents of the photoelectric conversion units 19a, 19b, 19c, 19d, and 19e of the photodiode 19 are changed to S19a, S19b, S19c, and S19, respectively.
d, S19e, and the electromotive currents of the photoelectric conversion units 20a, 20b, 20c, 20d, 20e of the photodiode 20 are
S20a, S20b, S20c, S20d, S
If it is 20e, the focus error signal is −19a + S.
19b-S19c + S20a-S20b + S20c, the track error signal is S19d-S19e-S.
Obtained from 20d + S20e.

A fourth embodiment of the focus error detecting apparatus of the present invention (first invention) will be described with reference to FIG. As shown in FIG. 7A, the light emitted from the laser diode 101 is transmitted through the hologram optical element 9, condensed on the optical disc 106 by the lens 115, reflected by the optical disc 106, and reverses the same optical path. The hologram optical element 9 advances and is diffracted. As shown in FIG. 9B, the hologram optical element 9 has regions 9a, 9b, 9 formed by diagonal lines having a rectangular area.
The photodiodes 10 to 13 are divided into four regions c and 9d, and are arranged at four positions around the hologram optical element 9 at different angles of 90 degrees around the respective axes.

Areas 9a and 9 of the hologram optical element 9
The + 1st-order diffracted light of b is focused on the front side of the photodiode 10, and the -1st-order diffracted light is focused on the rear side of the photodiode 11. In addition, the region 9c of the hologram optical element 9
The + 1st-order diffracted light of 9d and 9d is focused on the front side of the photodiode 12, and the -1st-order diffracted light is focused on the rear side of the photodiode 13.

Therefore, the electromotive currents of the photoelectric converters 10a, 10b, 10c of the photodiode 10, the electromotive currents of the photoelectric converters 11a, 11b, 11c of the photodiode 11, and the photoelectric converters 12a, 12 of the photodiode 12 are obtained.
The electromotive currents of b and 12c and the electromotive currents of the photoelectric conversion units 13a, 13b, and 13c of the photodiode 13 are respectively S1.
0a, S10b, S10c, S11a, S11b, S1
1c, S12a, S12b, S12c, S13a, S1
3b and S13c, the focus error signal is -S
10a + S10b-S10c + S11a-S11b + S
11c-S12a + S12b-S12c + S13a-S
13b + S13c, the track error signal is S
10a-S10c-S11a + S11c.

The focus error detecting device of the fourth embodiment is characterized in that a larger amount of light can be used for detecting the focus error than the focus error detecting device of the third embodiment, and the power consumption of the laser diode 101 is suppressed. If you want, optical disc 1
This is advantageous when the reflectance of 06 is low, or when the photoelectric conversion efficiency of the photodiodes 10, 11, 12, 13 is low.

A fifth embodiment of the focus error detecting device of the present invention (second invention) will be described with reference to FIG. As shown in FIG. 6A, the linearly polarized light emitted from the laser diode 101 is converted into parallel light by the collimator lens 102, transmitted through the polarization beam splitter 103, and the quarter wavelength plate 10 is transmitted.
At 4, it is converted into circularly polarized light. The light condensed on the optical disk 106 by the objective lens 105 is reflected, travels in the same optical path in the opposite direction, and is converted again into linearly polarized light by the ¼ wavelength plate 104. The light that has passed through the quarter-wave plate 104 twice in the forward and backward directions is reflected by the polarization beam splitter 103 and is converted into converged light by the collimator lens 107 because the direction of the linearly polarized light rotates 90 ° in the forward and backward paths. The light split into two by the beam splitter 108 is reflected by the half mirror 108.
Part of which is transmitted and part of which is reflected, and the transmitted light is received by the photodiode 27 through the split deflector 25 placed in front of the focal point. The reflected light is received by the photodiode 28 through the split deflector 26 placed behind the focal point.

The divided deflector 25 and the divided deflector 26 are
As shown in FIG. 3B, a pair of refracting surfaces having an inclination angle facing each other is formed in a concave shape, and the optical axis is positioned at the center of the refracting surfaces, whereby the collimator lens 10 is formed.
The light having a circular cross section converged by 7 is divided into two at the center and deflected, converted into two lights having a semicircular cross section, and received by photodiodes 27 and 28, respectively. The photodiodes 27 and 28 are provided with photoelectric conversion units 27a and 2a, as shown in FIGS.
7b, 27c and 28a, 28b, 28c.

Therefore, the focus error signal is the photoelectric conversion units 27a, 27b, 27c of the photodiode 27.
And the photoelectric conversion unit 28 of the photodiode 28
The electromotive currents of a, 28b, and 28c are respectively changed to S27a,
If S27b, S27c, S28a, S28b, and S28c, -S27a + S27b-S27c + S28a-.
Obtained from S28b + S28c. Further, the track error signal is obtained from S27a-S27c.

A sixth embodiment of the focus error detecting apparatus of the present invention (second invention) will be described with reference to FIG. As shown in FIG. 6A, the linearly polarized light emitted from the laser diode 101 is converted into parallel light by the collimator lens 102, transmitted through the polarization beam splitter 103, and the quarter wavelength plate 10 is transmitted.
At 4, it is converted into circularly polarized light. The light condensed on the optical disk 106 by the objective lens 105 is reflected, travels in the same optical path in the opposite direction, and is converted again into linearly polarized light by the ¼ wavelength plate 104. The light that has passed through the quarter-wave plate 104 twice in the reciprocating direction is reflected by the polarization beam splitter 103 because the direction of the linearly polarized light is rotated by 90 ° in the forward path and the backward path, and is reflected by the compound curved surface lens 113 at the center with two rays. Convergent light beams having different focal lengths are converted into contact light beams. This compound curved lens 113
The plane part is divided into two parts with the center line as a boundary, and each is configured as a lens having a different focal length.

The light transmitted through the compound curved surface lens 113 is split into two by the split deflector 31 in a plane perpendicular to the boundary surface of the two convergent lights and is deflected, so that it is between the focal points of the two convergent lights. The light is received by the placed photodiode 32. As shown in FIG. 2B, the split deflector 31 has a plane portion divided into two parts with a center line as a boundary, one of which is a convex wedge-shaped surface and the other is a concave wedge-shaped refractive surface. To be done. Therefore, as shown in FIG. 7C, the light that is about to be imaged at different focal positions by the compound curved surface lens 113 is further divided into two by the division deflector 31,
As a result, the photodiode 32 receives the light as a light flux whose surface perpendicular to the optical axis is semicircular.

As shown in FIG. 6D, the photodiode 32 is divided into two regions by a bisecting line 33. Then, the photoelectric conversion units 32a, 32b, 32c, 32d, 32e, 32f of the photodiode 32.
Of the electromotive force of S32a, S32b, and S32, respectively.
If c, S32d, S32e, and S32f, the focus error signal is -S32a + S32b-S32c + S3.
2d-S32e + S32f, the track error signal is S32a + S32b + S32c-S32d-S3.
2e-S32f.

A seventh embodiment of the focus error detecting device of the present invention (second invention) will be described with reference to FIG. As shown in FIG. 7A, the light emitted from the laser diode 101 is transmitted through the hologram optical element 34 and then focused on the optical disc 106 by the lens 115 and reflected by the optical disc 106 to reverse the same optical path. Proceed to hologram optical element 34
Is diffracted by. The hologram optical element 34 generates + 1st-order diffracted light focused on the front side of the photodiode 35 and −1st-order diffracted light focused on the rear side of the photodiode 36.

The hologram optical element 34 is divided into two regions 34a and 34b by a bisector located on the optical axis as shown in FIG. + 1st order diffracted light and -1
The second-order diffracted light is divided into two and is received by the photodiodes 35 and 36 as a semicircular light flux. As shown in FIG. 7C, the + 1st-order diffracted light forms two semicircular spots 37 arranged in parallel on the photodiode 35, and as shown in FIG. The two semi-circular spots 38 arranged side by side on the photodiode 36
To form.

Therefore, the focus error signal is the photoelectric conversion portions 35a, 35b, 35c of the photodiode 35.
Of the electromotive currents of S35a, S35b, and S35c, respectively.
And the photoelectric conversion units 36a, 36 of the photodiode 36
The electromotive currents of b and 36c are S36a and S36, respectively.
b and S36c, -S35a + S35b-S35
Obtained from c + S36a-S36b + S36c. Further, the track error signal is S35a + S35c-S36.
Obtained from a + S36c.

An eighth embodiment of the focus error detection device of the present invention (second invention) will be described with reference to FIG. As shown in FIG. 7A, the light emitted from the laser diode 101 passes through the hologram optical element 48, is condensed on the optical disc 106 by the lens 115, is reflected by the optical disc 106, and reverses the same optical path. Proceed and hologram optical element 48
Is diffracted by. As shown in FIG. 7B, the hologram optical element 48 has four regions 4 formed by two diagonal lines passing through the optical axis.
8a, 48b, 48c, 48d, and the + 1st order diffracted light in the regions 48a and 48b is the photodiode 4
9 is focused on the front side, and the −1st-order diffracted light is focused on the rear side of the photodiode 50.

Here, since the light flux is divided into four by the four regions of the hologram optical element 48, each light flux has a fan shape (1
/ 4 circle), and the photodiodes 48 and 4 respectively
Light is received at 9. Therefore, two fan-shaped spots 51 are formed in the photoelectric conversion parts 49a, 49b, 49c of the photodiode 49 shown in FIG. 7C, and the photoelectric conversion parts 50a, 50b of the photodiode 50 shown in FIG. 5
Two fan-shaped spots 52 are formed at 0c. The diffracted light of the region 48c of the hologram optical element 48 is condensed on the photoelectric conversion section 49d of the photodiode 49 and the photoelectric conversion section 50e of the photodiode 50, and the hologram optical element 48
The diffracted light of the region 48d of the photoelectric conversion unit 50d of the photodiode 50 and the photoelectric conversion unit 49 of the photodiode 49 are
It is focused on e.

Therefore, the electromotive currents of the photoelectric converters 49a, 49b, 49c, 49d, and 49e of the photodiode 49 are changed to S49a, S49b, S49c, and S4, respectively.
9d and S49e, and the electromotive currents of the photoelectric conversion units 50a, 50b, 50c, 50d and 50e of the photodiode 50 are S50a, S50b, S50c and S50, respectively.
d, S50e, the focus error signal is -S4
9a + S49b-S49c + S50a-S50b + S5
0c, the track error signal is S49d-S4.
9e-S50d + S50e.

A ninth embodiment of the focus error detecting device of the present invention (second invention) will be described with reference to FIG. The light emitted from the laser diode 101 as shown in FIG.
After passing through the hologram optical element 39, the light is condensed on the optical disk 106 by the lens 115, reflected by the optical disk 106, and travels in the opposite optical path in the opposite direction.
Diffracted at 9. The hologram optical element 39 is divided into four regions 39a, 39b, 39c, 39d by two diagonal lines passing through the optical axis, as shown in FIG. Also, four photodiodes 40, 41, 42, 43 are provided around the optical axis with respect to the hologram optical element 39.
Are arranged at right angles.

Area 3 of hologram optical element 39
The + 1st-order diffracted light of 9a and 39b is reflected by the photodiode 40
To form two fan-shaped (1/4 circular) spots 44 on the photodiode 40, and the -1st-order diffracted light is focused on the back of the photodiode 41 to form two fan-shaped spots on the photodiode 41. Spots 45 are formed. Further, the areas 39c and 3 of the hologram optical element 39 are
The + 1st-order diffracted light of 9d is focused in front of the photodiode 42 to form two fan-shaped spots 46 in the photodiode 42, and the -1st-order diffracted light is focused behind the photodiode 43, and the photodiode 43 Forming two fan-shaped spots 47.

Therefore, the electromotive currents of the photoelectric conversion parts 40a, 40b, 40c of the photodiode 40, the electromotive currents of the photoelectric conversion parts 41a, 41b, 41c of the photodiode 41, and the photoelectric conversion parts 42a, 42 of the photodiode 42 are formed.
The electromotive currents of b and 42c and the electromotive currents of the photoelectric conversion units 43a, 43b, and 43c of the photodiode 43 are respectively S
40a, S40b, S40c, S41a, S41b, S
41c, S42a, S42b, S42c, S43a, S
43b and S43c, the focus error signal is −
S40a + S40b-S40c + S41a-S41b +
S41c-S42a + S42b-S42c + S43a-
The track error signal obtained from S43b + S43c is
Obtained from S40a-S40c-S41a + S41c.

The focus error detecting device of the ninth embodiment is characterized in that a larger amount of light can be used for detecting the focus error than the focus error detecting device of the eighth embodiment, and the power consumption of the laser diode 101 is suppressed. If you want, optical disc 1
This is advantageous when the reflectance of 06 is low, or when the photoelectric conversion efficiency of the photodiodes 40, 41, 42, 43 is low.

A tenth embodiment of the focus error detecting device of the present invention (third invention) will be described with reference to FIG. FIG.
As described above, the linearly polarized light emitted from the laser diode 101 is converted into parallel light by the collimator lens 102, transmitted through the polarization beam splitter 103, and converted into circularly polarized light by the ¼ wavelength plate 104. The light condensed on the optical disk 106 by the objective lens 105 is reflected, travels in the same optical path in the opposite direction, and is converted again into linearly polarized light by the ¼ wavelength plate 104. The light that has passed through the quarter-wave plate 104 twice in the forward and backward directions is reflected by the polarization beam splitter 103 because the direction of the linearly polarized light rotates by 90 ° in the forward path and the backward path, is converted into converged light by the collimator lens 107, and is transmitted. Reflector 6
7 is irradiated.

The transflective plate 67 is, as shown in FIG.
It is divided into two regions 67a and 67b by a bisector with respect to the optical axis. The region 67a reflects light and the region 67b
Transmits light. The light divided into two by the transmissive / reflecting plate 67 has a semi-circular light flux, and is shown in FIGS.
The light is received by the photodiode 68 placed in front of the focus and the photodiode 69 placed behind the focus, as shown in FIG.

Therefore, the focus error signal is generated by the electromotive currents of the photoelectric conversion units 68a and 68b of the photodiode 68 and the photoelectric conversion units 69a and 69b of the photodiode 69.
Of the electromotive currents of S68a, S68b, and S69, respectively.
a and S69b are -S68a + S68b + S69
Obtained from a-S69b. Further, the track error signal is obtained from S68a + S68b-S69a-S69b.

An eleventh embodiment of the focus error detection device of the present invention (third invention) will be described with reference to FIG. FIG.
As described above, the linearly polarized light emitted from the laser diode 101 is converted into parallel light by the collimator lens 102, transmitted through the polarization beam splitter 103, and converted into circularly polarized light by the ¼ wavelength plate 104. The light condensed on the optical disk 106 by the objective lens 105 is reflected, travels in the same optical path in the opposite direction, and is converted again into linearly polarized light by the ¼ wavelength plate 104. The light that has passed through the quarter-wave plate 104 twice in the reciprocating direction is reflected by the polarization beam splitter 103 because the direction of the linearly polarized light is rotated by 90 ° in the forward path and the backward path, and is reflected by the compound curved surface lens 113 at the center with two rays. Convergent light beams having different focal lengths are converted into contact light beams.

This light is transmitted through the divisional deflector 72, and the divisional deflector 72 is formed in a V-shape in one region sandwiching the optical axis and the other region as shown in FIG. Is formed flat and is oriented in a direction perpendicular to the compound curved surface lens 113. Therefore, as shown in FIG. 6C, the two incident convergent lights are incident on a plane perpendicular to the boundary surface. It is divided into two and deflected, and the light is received by the photodiode 73 shown in FIG.

Therefore, the photoelectric conversion parts 73a, 73b, 73c, 73d, 73e, 73 of the photodiode 73 are formed.
The electromotive currents of f, 73g, and 73h are S73a,
S73b, S73c, S73d, S73e, S73f,
If S73g and S73h, the focus error signal is
-S73a + S73b-S73c + S73d + S73e
-S73f + S73g-S73h, the track error signal is S73a + S73b-S73c-S73d.
+ S73e + S73f-S73g-S73h.

A twelfth embodiment of the focus error detection device of the present invention (third invention) will be described with reference to FIG. FIG.
As described above, the light emitted from the laser diode 101 passes through the hologram optical element 75 and then the lens 115.
Is condensed on the optical disc 106, reflected by the optical disc 106, travels in the same optical path in the opposite direction, and is diffracted by the hologram optical element 75. Since the hologram optical element 75 is divided into two regions 75a and 75b by a bisector passing through the optical axis as shown in FIG. 7B, the + 1st-order diffracted light focused in front of the photodiode 76 and the photo The -1st-order diffracted light focused on the rear side of the diode 77 is generated.

Therefore, the + 1st order diffracted light of the area 75a of the hologram optical element 75 forms a spot 78a on the photodiode 76 as shown in FIG.
The + 1st order diffracted light of the above forms a spot 79a on the photodiode 76 as shown in FIG. Also, the area 75
The -1st-order diffracted light of a is spotted on the photodiode 77.
8b, and the −first-order diffracted light in the region 75b forms a spot 79b on the photodiode 77.

Therefore, the focus error signal is the photoelectric conversion portions 76a, 76b, 76 of the photodiode 76.
The electromotive currents of c and 76d are changed to S76a and S76, respectively.
b, S76c, S76d, and the electromotive currents of the photoelectric conversion units 77a, 77b, 77c, 77d of the photodiode 77 are S77a, S77b, S77c, S77, respectively.
If it is d, -S76a + S76b + S76c-S76
Obtained from d + S77a-S77b-S77c + S77d. Further, the track error signal is S76a-S76b.
+ S76c-S76d-S77a + S77b-S77c
Obtained from + S77d.

A thirteenth embodiment of the focus error detection device of the present invention (third invention) will be described with reference to FIG. FIG.
As described above, the light emitted from the laser diode 101 passes through the hologram optical element 80 and then the lens 115.
Is condensed on the optical disc 106, reflected by the optical disc 106, travels in the same optical path in the opposite direction, and is diffracted by the hologram optical element 80. The hologram optical element 80 is divided into four regions 80a, 80b, 80c, 80d by two diagonal lines passing through the optical axis, as shown in FIG.

Then, the + 1st-order diffracted light of the region 80a is focused on the front side of the photodiode 81, and as shown in FIG.
A spot 83a is formed on 1c. Further, the -1st-order diffracted light is focused on the rear side of the photodiode 82, and as shown in FIG.
Spots 83b are formed on 2b and 82d.

Further, the + 1st-order diffracted light in the region 80b is focused on the front side of the photodiode 81 as shown in FIG.
A spot 84a is formed on 1d. Further, the −1st-order diffracted light is focused on the rear side of the photodiode 82, as shown in FIG.
Spots 84b are formed on a and 82c.

Further, the area 80 of the hologram optical element 80
The diffracted light of c is the photoelectric conversion unit 81 of the photodiode 81.
e and the diffracted light of the region 80d of the hologram optical element 80, which is condensed on the photoelectric conversion portion 82f of the photodiode 82,
The light is focused on the photoelectric conversion unit 82e of the photodiode 82 and the photoelectric conversion unit 81f of the photodiode 81.

Therefore, the photoelectric conversion portions 81a, 81b, 81c, 81d, 81e, 81 of the photodiode 81 are
The electromotive currents of f are S81a, S81b, and S81, respectively.
c, S81d, S81e, S81f, and the photoelectric conversion units 82a, 82b, 82c, 82 of the photodiode 82.
The electromotive currents of d, 82e, and 82f are S82a,
If S82b, S82c, S82d, S82e, and S82f, the focus error signal is -S81a + S81b.
+ S81c-S81d + S82a-S82b-S82c
The track error signal obtained from + S82d is S81e.
Obtained from -S81f-S82e + S82f.

A fourteenth embodiment of the focus error detection device of the present invention (third invention) will be described with reference to FIG. FIG.
As described above, the light emitted from the laser diode 101 passes through the hologram optical element 87 and then the lens 115.
Is condensed on the optical disc 106, reflected by the optical disc 106, travels in the same optical path in the opposite direction, and is diffracted by the hologram optical element 87. The hologram optical element 87 is divided into four regions 87a, 87b, 87c, 87d by two diagonal lines passing through the optical axis as shown in FIG. In addition, four photodiodes 88, 8 around the optical axis
9, 90, 91 are arranged, and the photodiode 9
0 is the position where the photodiode 88 is rotated 90 ° around the axis 96, and the photodiode 91 is the position where the photodiode 89 is rotated 90 ° around the axis 96.

+ In the area 87a of the hologram optical element 87
The first-order diffracted light is focused on the front side of the photodiode 88 to form a fan-shaped (1/4 circular) spot 92 a on the photodiode 88, and the −1st-order diffracted light is focused on the rear side of the photodiode 89 to generate a photo. A fan-shaped spot 92b is formed on the diode 89. The + 1st-order diffracted light in the region 87b is focused on the front side of the photodiode 88 to form a fan-shaped spot 93a on the photodiode 88,
The −1st-order diffracted light is focused behind the photodiode 89 and forms a fan-shaped spot 93b on the photodiode 89.

Further, the + 1st order diffracted light in the region 87c is focused in front of the photodiode 90 to form a fan-shaped spot 94a in the photodiode 90, and the −1st order diffracted light is focused in the rear of the photodiode 91. , A fan-shaped spot 94b is formed on the photodiode 91.
The + 1st-order diffracted light in the region 87d is focused in front of the photodiode 90 to form a fan-shaped spot 95a in the photodiode 90, and the -1st-order diffracted light is focused in the rear of the photodiode 91 and is focused on the photodiode 91. A fan-shaped spot 95b is formed.

Therefore, the electromotive currents of the photoelectric conversion units 88a, 88b, 88c, 88d of the photodiode 88 and the photoelectric conversion units 89a, 89b, 89 of the photodiode 89 are generated.
c, 89d, the photoelectric conversion units 90a, 90b, 90c, 90d of the photodiode 90, and the photoelectric conversion units 91a, 91b, 91 of the photodiode 91.
The electromotive currents of c and 91d are S88a and S88, respectively.
b, S88c, S88d, S89a, S89b, S89
c, S89d, S90a, S90b, S90c, S90
If d, S91a, S91b, S91c, and S91d, the focus error signal is -S88a + S88b + S.
88c-S88d + S89a-S89b-S89c + S
89d-S90a + S90b + S90c-S90d + S
91a-S91b-S91c + S91d, and the track error signal is S88a-S88b + S88c-S.
88d-S89a + S89b-S89c + S89d.

Here, the focus error detecting device of the fourteenth embodiment is characterized in that a larger amount of light can be used for detecting the focus error than the focus error detecting device of the thirteenth embodiment, and the power consumption of the laser diode 101 is large. This is advantageous when it is desired to suppress the above, when the reflectance of the optical disc 106 is low, or when the photoelectric conversion efficiency of the photodiodes 88, 89, 90, 91 is low.

Among the above-mentioned embodiments, the focus error detecting devices of the first embodiment, the second embodiment, the fifth embodiment, the sixth embodiment, the tenth embodiment and the eleventh embodiment are as follows. Is
If the polarization beam splitter is replaced with a beam splitter, the utilization factor of light will be low, but the quarter wavelength plate can be omitted and the configuration can be simplified.

In each of the above-mentioned embodiments, an optical disk such as a magneto-optical disk is used as an image forming object for detecting the focus error. A pattern is exposed by the photolithography technique as the image forming object. The present invention can be similarly applied to the case of using a semiconductor wafer or other target object at the time of performing, and it is possible to detect the focus error in each case.

[0084]

As described above, according to the first aspect of the present invention, since the shape of the spot received by the light receiving means is fan-shaped and the essential points are common, the focus is greater than that of the conventional circular spot. It is possible to obtain the effect of increasing the error detection sensitivity.

Further, in the second aspect of the present invention, since the spots of light received by the light receiving means are fan-shaped and the main points thereof are separated from each other by a required dimension, stability of the light emitting means with respect to wavelength fluctuation and It is possible to obtain the effect that both the size reduction of the focus error detection device and the certainty of starting the servo operation are compatible with each other.

Further, in the third invention of the present invention, the shape of the spot received by the light receiving means is a fan shape, and this is received by the photodiode having two regions, so that the light emitting means is stable against wavelength fluctuation. It is possible to obtain the effect that both the size and the size of the focus error detection device are compatible with the certainty of starting the servo operation.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

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

FIG. 3 is a diagram showing spots on a photodiode of a second embodiment.

FIG. 4 is a configuration diagram of a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram of a fifth embodiment of the present invention.

FIG. 7 is a configuration diagram of a sixth embodiment of the present invention.

FIG. 8 is a configuration diagram of a seventh embodiment of the present invention.

FIG. 9 is a configuration diagram of an eighth embodiment of the present invention.

FIG. 10 is a configuration diagram of a ninth embodiment of the present invention.

FIG. 11 is a configuration diagram of a tenth embodiment of the present invention.

FIG. 12 is a configuration diagram of an eleventh embodiment of the present invention.

FIG. 13 is a configuration diagram of a twelfth embodiment of the present invention.

FIG. 14 is a configuration diagram of a thirteenth embodiment of the present invention.

FIG. 15 is a configuration diagram of a fourteenth embodiment of the present invention.

FIG. 16 is a diagram for explaining the first operation of the focus error detection device of the present invention.

FIG. 17 is a diagram for explaining the second operation of the focus error detection device of the present invention.

FIG. 18 is a diagram for explaining the third action of the focus error detection device of the present invention.

FIG. 19 is a configuration diagram showing a first example of a conventional focus error detection device.

FIG. 20 is a diagram for explaining the operation of the first example of the conventional focus error detection device.

FIG. 21 is a diagram for explaining signal processing in the first example.

FIG. 22 is a configuration diagram showing a second example of a conventional focus error detection device.

FIG. 23 is a diagram for explaining a problem in the conventional focus error detection device.

FIG. 24 is a diagram for explaining another problem in the conventional focus error detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transflective plate 2,3 Photodiode 4,5 Spot 6 Complex curved lens 7 Photodiode 9 Hologram optical element 10, 11, 12, 13 Photodiode 18 Hologram optical element 19,20 Photodiode 25,26 Divided deflector 27, 28 Photodiode 31 Divided Deflector 32 Photodiode 34 Hologram Optical Element 35, 36 Photodiode 39 Hologram Optical Element 40, 41, 42, 43 Photodiode 48 Hologram Optical Element 49, 50 Photodiode 67 Transmissive Reflector 68, 69 Photodiode 72 Divided deflector 73 Photodiode 75 Holographic optical element 76, 77 Photodiode 80 Holographic optical element 81, 82 Photodiode 87 Holographic optical element 88, 89, 0,91 Photodiode 101 Laser diode (light emitting means) 102 Collimating lens 103 Polarizing beam splitter 104 1/4 wavelength plate 105 Objective lens (imaging lens) 106 Optical disk (imaging target) 107 Collimating lens 108 Beam splitter (deflecting means) 109, 110 Photodiode 113 Complex curved lens 114 Hologram optical element 115 Lens 116, 117, 120, 121 Photodiode

Claims (12)

[Claims] 1. A light emitting means, a light collecting means for collecting the light emitted from the light emitting means onto an image forming object, and at least two light rays reflected by the image forming object, light α and light β. Branching means for branching into converged light, first light receiving means positioned in front of the converged position of one branched light, and second light receiving positioned behind the converged position of the other branched light. Means, each of the first and second light receiving means has three light receiving portions divided by a pair of substantially parallel line segments, and the respective spots of the branched light beams have the same essential points. A focus error detection device comprising a pair of fan-shaped portions, the main points of which are located in the central light receiving portion and each spot intersects with the line segment. 2. A light emitting means, a condensing means for condensing the light emitted from the light emitting means onto an image forming object, and at least two light rays α and β reflected by the image forming object. It has a branching means for branching into a convergent light and three light receiving parts which are located in front of the convergent position of the light α and which are divided by a pair of substantially parallel line segments A and B. The light receiving means γ whose optical axis passes through the light receiving portion sandwiched between the dividing line A and the dividing line B, and the dividing line C which is behind the convergent position of the light β and is a pair of substantially parallel line segments. And three light receiving portions divided by a dividing line D, and an optical axis of the light β is provided with a light receiving means δ that passes through the light receiving portion sandwiched between the dividing line C and the dividing line D.
The light α is composed of light η and light θ whose optical axes pass through the centers of the dividing lines A and B, and the light η forms the spot ι formed on the light receiving means γ and the light θ. All the spots κ formed on the means γ are fan-shaped with an apex angle of less than 180 °, and are substantially point-symmetric with respect to the midpoint between the center of the spot ι and the center of the spot κ, and the spot ι. And the center line of the spot κ are substantially perpendicular to the dividing lines A and B, and the light β is a light whose optical axis passes through the centers of the dividing lines C and D. The spot ν formed by the light λ on the light receiving means δ and the spot ξ formed by the light μ on the light receiving means δ are fan-shaped having an apex angle of less than 180 °. Yes, and moreover, regarding the midpoint between the center of the spot ν and the center of the spot ξ And the center line of the spot ν and the center line of the spot ξ are substantially perpendicular to the dividing line C and the dividing line D. 3. A focus according to claim 1, wherein a half mirror is arranged as a deflecting means between the condensing means and the light emitting means, and the light reflected by the image forming object is deflected out of the optical axis of the emitted light. Error detection device. 4. A diffracting means is disposed between the condensing means and the light emitting means, and diffracts the light reflected by the object to be imaged to output convergent light branched into two. Focus error detector. 5. A light emitting means, a condensing means for condensing the light emitted from the light emitting means onto an image forming object, and at least two light rays reflected by the image forming object, light α and light β. Branching means for branching into converged light, first light receiving means positioned in front of the converged position of one branched light, and second light receiving positioned behind the converged position of the other branched light. Means, each of the first and second light receiving means has three light receiving portions divided by a pair of substantially parallel line segments, and the spots of each of the branched light beams have predetermined points at predetermined intervals. A focus error detection device, which is formed into a pair of fan-shaped members facing each other, the main point of which is located in the central light-receiving portion and each spot intersects with the line segment. 6. A light emitting means, a condensing means for condensing the light emitted from the light emitting means onto an image forming object, and at least two light rays α and light β reflected by the image forming object. It has a branching means for branching into a convergent light and three light receiving parts which are located in front of the convergent position of the light α and which are divided by a pair of substantially parallel line segments A and B. The light receiving means γ whose optical axis passes through the light receiving portion sandwiched between the dividing line A and the dividing line B, and the dividing line C which is behind the convergent position of the light β and is a pair of substantially parallel line segments. And a light receiving means δ having three light receiving portions divided by a dividing line D, and an optical axis of the light β passing through the dividing line C and a light receiving portion sandwiched by the dividing lines D. In the device, the light α is composed of light η and light θ, and the spot ι formed by the η on the light receiving means γ and the light θ are received by the light receiving means γ. Spot to be formed κ
Are all fan-shaped having an apex angle of 180 ° or less, and are substantially point-symmetric with respect to the midpoint between the center ρ of the spot ι and the center σ of the spot κ, and the center line of the spot ι is also the spot κ. Is substantially perpendicular to the dividing line A and the dividing line B, and the distance between the center ρ and the dividing line A is equal to the distance between the center σ and the dividing line B. It is shorter than the distance of the line B, and the spot ι straddles the dividing line A when the light converging unit is focused on the image formation target, and the light β is composed of light λ and light μ. The spot ν formed by the light λ on the light receiving means δ and the spot ξ formed by the light μ on the light receiving means δ are both fan-shaped having an apex angle of 180 ° or less and the center of the spot ν. τ and the center υ of the spot ξ
Are substantially point symmetric with respect to the middle point of the spot, and both the center line of the spot ν and the center line of the spot ξ are the dividing lines C.
Is substantially perpendicular to the dividing line D, the distance between the center τ and the dividing line C is equal to the distance between the center υ and the dividing line D, and is shorter than the distance between the center τ and the dividing line D, The focus error detection device, wherein the spot ν straddles the dividing line C when the condensing unit focuses on the image formation target. 7. A focus according to claim 5, wherein a half mirror is arranged as a deflecting means between the condensing means and the light emitting means, and the light reflected by the object to be imaged is deflected out of the optical axis of the emitted light. Error detection device. 8. A diffracting means is arranged between the condensing means and the light emitting means, and diffracts the light reflected by the object to be imaged to output convergent light branched into two. Focus error detector. 9. A light emitting means, a condensing means for condensing the light emitted from the light emitting means onto an image forming object, and at least two light rays α and light β reflected by the image forming object. Branching means for branching into converged light, first light receiving means positioned in front of the converged position of one branched light, and second light receiving positioned behind the converged position of the other branched light. Means, each of the first and second light receiving means has two light receiving portions divided by one line segment, and the spots of each branched light are fan-shaped to form the line segment. A focus error detection device characterized by being crossed. 10. A light emitting means, a condensing means for condensing the light emitted from the light emitting means onto an image forming object, and at least two light rays α and β reflected by the image forming object. In a focus error detection device comprising a branching unit for branching into convergent light, a light receiving unit γ in front of the convergence position of the light α, and a light receiving unit δ behind the convergence position of β, the light receiving unit γ is divided. A light receiving portion E and a light receiving portion F divided into two by a line A are provided,
The optical axis of the light α passes through the light receiving portion F, and the spot ε formed by the light α on the light receiving means γ is a fan shape having an apex angle of 180 ° or less, and the center line of the spot ε is the dividing line. The spot ε is substantially perpendicular to A, and when the light converging means is focused on the object to be imaged, the spot ε is divided by the dividing line A.
And the light receiving means δ includes a light receiving portion H and a light receiving portion I which are divided into two by a dividing line C, the optical axis of the light β passes through the light receiving portion I, and the light β is received by the light receiving portion H. The spot ζ formed on the means δ is a fan shape having an apex angle of 180 ° or less, the center line of the spot ζ is substantially perpendicular to the dividing line C, and the condensing means focuses the object to be imaged. The focus error detection device is characterized in that the spot ζ crosses the dividing line C when the focus error occurs. 11. A half mirror as a deflecting means is arranged between the condensing means and the light emitting means to deflect the light reflected by the object to be imaged out of the optical axis of the emitted light.
0 focus error detector. 12. A diffracting means is disposed between the condensing means and the light emitting means, and diffracts the light reflected by the object to be imaged.
The focus error detection device according to claim 9 or 10, which outputs a convergent light branched into a book.