JPS6228708A - Optical beam scanner and its manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] The present invention aims to realize an inexpensive and highly accurate light beam linear scanning device by using a semiconductor laser, an aberration correction hologram lens,
By using only a scanning hologram lens, the beam shaping of the semiconductor laser is performed to suppress the influence of jitter on the scanning light due to wavelength hopping of the longitudinal mode of the semiconductor laser, and to improve scanning characteristics (linearity) caused by variations in the oscillation wavelength of the semiconductor laser. an optical beam scanning device that absorbs the deterioration of the scanning diffracted wave and further corrects the aberration of the scanning diffracted wave; The present invention provides a method for manufacturing a light beam device in which a coma aberration wave obtained by similarly entering another auxiliary optical system is created as an object wave by using a wave as a reference wave.

[Industrial application field]

The present invention performs beam shaping of a semiconductor laser.

The present invention relates to a high-precision optical beam linear scanning device that can suppress the influence of jitter on scanning light due to mode hopping of a semiconductor laser and reduce aberrations of scanning light, and a method for manufacturing the same.

[Conventional technology]

In the high-precision linear scanning of laser beams in laser printers, etc., instead of polygons using complicated and expensive rotating polygon mirrors, we have used hologram lenses, which are small, lightweight, and inexpensive, and have a simple structure and are easy to manufacture. Light beam devices are attracting attention.

FIG. 8 shows the principle of a conventional light beam device using a hologram lens. This example is based on the method filed by the present applicants (9).
JP-A-57-2018) is used.

Figure (a) is a perspective view of the hologram scanner 1.
4 (scanning hologram lens) is a disk with multiple interferometric zone plates (IZP) made by interfering coherent plane waves and spherical waves with a wavelength lower than that of a semiconductor laser on a photosensitive plate. be. When this hologram scanner 14 is irradiated with a semiconductor laser beam 16 which is a diverging wave as a reproduced wave, the diffracted light 17 forms an image on the photocondrum 15, and the hologram scanner 14
According to the rotation of the drum 15, a predetermined area on the drum 15 is linearly scanned the same number of times as the number of IZPs per rotation. That is, the hologram scanner 14 has both the function of a scanning device and the function of an imaging lens, in other words, a beam shaping function.

In this case, in order to increase the resolution on the photocondrum 15, it is necessary to make the imaging beam diameter of the diffracted light 17 there as small as possible. For this purpose, it is desirable to increase the diameter DH of the irradiation beam on the hologram scanner 14.

However, when the beam diameter DH is increased, astigmatism occurs.

Also, comatic aberration occurs and the image formation point on the photocondrum 15 is not fixed at one point.
This contradicts the requirement to increase the beam diameter DH (and decrease the diameter of the imaging beam on the photocondrum 15).

On the other hand, apart from the above-mentioned problems, it has become important to use semiconductor lasers as laser light sources in hologram scanners because they are small, lightweight, directly modifiable, and inexpensive.

In this case, a single mode laser is required because the scanning beam will not be focused on a single point unless the semiconductor laser has a single longitudinal mode.

For this purpose, the refractive index guided semiconductor lasers currently on the market meet the requirements. However, even if the oscillation wavelength is in single mode during DC bias, the oscillation wavelength may vary from 0.3 nm to 0.3 nm due to changes in ambient temperature, conduction current, and pulse application.
A distance of several nm causes a phenomenon called mode hopping. When mode hopping occurs, the diffracted light 17 diffracted by the hologram scanner 14 shifts as shown by the broken line 18 in the side view of FIGS. 100~300μ
This is a major problem when used in high-precision linear scanners such as laser printers because it causes deterioration in print quality.

Several conventional examples have been independently provided to solve the problems caused by the aberration of the scanning light and the problems caused by mode hopping.

FIG. 9 shows a 9.
Technology for which an existing patent application has been filed by the applicants
172617), and as shown in the perspective view of FIG. The beams are crossed and irradiated to the hologram scanner 21 (scanning hologram lens),
The diffracted wave 22 scans and forms an image on the photocondrum 23. The principle of this technology is that a photocondrum 23 is used by a hydrogram lens 20 for astigmatism and coma correction.
If an aberration is generated that cancels the astigmatism and coma aberration generated by the hologram scanner 21, it will cancel out the astigmatism and coma aberration generated by the hologram scanner 21, and the image will be focused on a single point on the photocondrum 23. It is something. FIG. 9(b) is a diagram showing a method of creating an aberration-correcting hologram lens 20 for generating the above-mentioned aberrations. First, the plane wave 22 from the laser light source is transmitted to the half mirror 23.
'Imaging lens 24. An image is formed on an imaging point 26 (corresponding to the imaging point on the photocon drum 23) via a mirror 25. The imaged wave 27 is further irradiated to the hologram scanner 21 from the opposite direction as a diverging spherical wave, and the diffracted wave is crossed once at 29 and then forms an object wave 28 on the hologram lens 20.
It is irradiated as

The hologram lens 20 created as described above is
This is because it is created by an object wave 28 that cancels aberrations generated in the hologram scanner 21.

When the hologram lens 20 is irradiated with parallel light, which is a reproduced wave, from the direction 31, a diffracted wave without aberration forms an image on the imaging point 26, following a path opposite to that at the time of creation. The above technique solves the problems of astigmatism and coma.

Next, FIG. 10 (al is a perspective view showing the general principle of a conventional example for solving the influence of mode hopping. Since the diffracted light from the hologram is dispersed, causing aberrations, it has been proposed to compensate by placing another hologram after the hologram that diffracts in the opposite direction to the diffraction direction of the previous hologram. .

(■C, [1, Burckhardt, Be1l 5
yst, Tech, J.

45, 1841 (1966) ■D, J, DeBitetto, Appl, P
Hys, Lett.

9, 417 (1966) ■”0ptical Holography”A
academic press.

N, Y, 1971.1971. P, 502) A similar idea is shown in FIG. 10(a). The feature of FIG. 10 (al) is that it has a hologram lens 33 in front of the hologram scanner 32, and its characteristics are set to diffract in the direction opposite to that of the hologram scanner 32.

As a result, normally, the semiconductor laser beam 35 becomes a diffracted wave 36 by the hologram lens 33, is further diffracted by the hologram scanner 32, and is imaged on the photocondrum 34 as a convergent wave 37. Next, when mode hopping occurs in the semiconductor laser, the hologram lens 33
In the case of the hologram scanner 32, it shifts vertically downward as shown by the broken line 38 in the side view of FIG. The upper imaging point does not shift, which attempts to eliminate the effects of mode hopping.

FIG. 11 shows a technology for which an existing patent application has been filed (Japanese Patent Application Laid-Open No. 1983-70517) as a specific conventional example using the above technology.
). In this conventional example, a semiconductor laser beam 40 is once diffracted by a hologram lens 41 in exactly the same manner as shown in FIG.

FIG. 12 (bl is another conventional example using the technique shown in FIG.
181523). As shown in FIG. 4(a), a plane wave 45 converted from a semiconductor laser beam using an optical system 44 is diffracted and scanned by a hologram scanner 46, and the diffracted plane wave 47 is screened by an imaging lens 48 and a mirror 49. For those that form an image on 50,
As shown in FIG. 5B, a compensating hologram lens 51 is inserted, and the specific arrangement thereof is given.

[Problem that the invention seeks to solve]

In the above conventional examples, first, the conventional example shown in FIG. 9 is for solving astigmatism and coma aberration.

As shown in FIG. 3(b), a method for creating an aberration correcting hologram lens is shown. However, in this conventional example, if the use of semiconductor laser light is stipulated, the same semiconductor laser light must be used as the wave to create the aberration correction hologram lens, but unlike the semiconductor laser light, it is difficult to produce a hologram with a long wavelength. There is generally no high-efficiency light-sensitive material capable of recording images, and there has been a problem in that no technology has been provided to solve this problem. Furthermore, since the light incident on the aberration correction hologram lens is parallel light, it is necessary to convert the light emitted from the laser into parallel light using a collimator made up of a plurality of lens groups.

On the other hand, the eleventh
The conventional example shown in the figure has a problem in that, although it shows the basic concept, it does not provide means for how to apply it to a specific light beam scanning device.

Furthermore, although the conventional example shown in Fig. 12 shows a specific application, it is generally applicable to those using a plane wave as a reproduction wave as shown in Fig. 12 (δ), and the hologram scanner is a single hologram scanner. is a spatial frequency and therefore has no imaging function,
Therefore, the expensive collimating lens 44. Imaging lens 48
was necessary.

In order to solve the above-mentioned problems at the same time, the present invention uses a semiconductor laser without using a lens in order to realize an inexpensive and highly accurate light beam linear scanning device.

The configuration includes only an aberration correction hologram lens and a scanning hologram lens, which eliminates astigmatism and correction of scanning light.

Simultaneously solving the problems caused by coma aberration and mode hopping, and further improving the beam shaping of semiconductor lasers.

It is an object of the present invention to provide a light beam scanning device that can absorb scanning characteristics (linearity) due to lot-to-lot variations in the oscillation wavelength of a semiconductor laser, and a specific manufacturing method thereof.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a light beam scanning device in which an emitted wave from a laser is incident on a scanning hologram lens having a positionally different spatial frequency distribution, and a surface to be scanned is scanned by the diffracted waves. The laser is a semiconductor laser, and converts the wavefront of the emitted wave to produce an astigmatism and an astigmatism of the scanning diffracted wave.

The present invention provides a light beam scanning device and a method for manufacturing the same, characterized by having an aberration-correcting hologram lens that reduces comatic aberration on the surface to be scanned.

[For production]

In the configuration means of the optical beam scanning device, the diverging spherical wave emitted from the semiconductor laser is incident on the aberration correction hologram lens, where the astigmatism and coma on the scanning surface of the scanning light generated by the scanning hologram lens are detected. It is converted into a wavefront with aberrations that cancel out the aberrations. Next, the diffracted wave from the aberration correction hologram lens thus converted is incident on the scanning hologram lens, and the diffracted wave from there is scanned and imaged on the surface to be scanned as a convergent spherical wave. At this time,
Astigmatism that occurs in scanning hologram lenses.

and coma aberration are corrected by the aberrations described above, and astigmatism and coma aberration on the scanned surface are reduced.

Also, the diffraction angle of the hologram lens for aberration correction.

By setting the angle at which the change in the scanning point on the scanned surface due to the diffracted wave from the scanning hologram lens is reduced with respect to the hopping of the glare mode in the semiconductor laser,
The jitter of scanning light can be reduced.

Next, in the method of manufacturing the optical beam scanning device described above, as a method of creating a hologram lens for aberration correction, a spherical aberration is generated by passing light of wavelength λ of a semiconductor laser used as reproduction light and light of a shorter wavelength λ2 through an auxiliary optical system. On the other hand, light with the same wavelength λ2 is passed through the auxiliary optical system to generate coma aberration that cancels astigmatism and coma generated by the scanning hologram lens, and becomes an object wave. An aberration correcting hologram lens having the above-mentioned effect can be created using the reproduction light of λ1.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail.

(Configuration and operation of light beam scanning device (Fig. 1(a)) 1st
FIG. 2(a) is a side view of the configuration of a light beam scanning device according to the present invention. The diverging spherical wave 4 emitted from the semiconductor laser 2 enters the aberration correction hologram lens 1 in the first order, and the diffracted wave 5 from there is transmitted to a disc-shaped hologram scanner that rotates around an axis 3a with a beam diameter DH. 3 (scanning hologram lens). The diffracted wave 6, which is a convergent spherical wave, forms an image at an imaging point 7 on a photocondrum (not specifically shown), and is scanned by rotation of the hologram scanner 3.

In the above configuration, the aberration correction hologram lens 1 is set at an appropriate diffraction angle, which will be described later, and is set so that the imaging point 7 does not shift with respect to the focusing of the wavelength of the longitudinal mode of the semiconductor laser 2. . At the same time, the aberration correction hologram lens 1 takes in the diverging light emitted from the semiconductor laser 2, and after a while.

It is created to generate an aberrated wavefront that cancels the astigmatism and coma generated by the hologram scanner 3, thereby reducing the aberrations at the imaging point 7. In order to reduce the aberration of the scanning light on the scanning surface, consider what type of wavefront should be made incident.

In Figure 1(b), the phase transfer function of the hologram is defined as φ
+−+ (x, y), the phase of the incident 2nd diffracted wave is φ, N(
x, y) and φ (x, y), there is a quadratic relationship.

φoVr (x, y) - φ, N (x, y) + φH (x, y)...
(2) As will be explained later, in a hologram scanner based on a method for which the present applicant has previously applied for a patent (patent application number 59-659), a hologram is created using a wavelength lower than that of reproduction light. At this time, since the hologram creation and reproduction conditions are different, φ:N(x
, y) is aberration-free, then in general, φ0uT(x, y)
, aberrations occur. On the other hand, the patent application number 59-659
In the example implemented by , the hologram creation optical system is designed to minimize aberrations.

However, in order to obtain a beam diameter with even smaller aberrations,
If the phase of the desired diffracted wave is φ (XI)'), then from ■.

φ+N(X)y) =φout(x,y) −φ,,(X,y)・・・・・・
■ ■(x, y) e S, S: If the incident wave that fills the reproduction area is input, φ0LJT(XI>')=
φ. , uy(x+y)+ In other words, there is no aberration. Here, the desired phase of the diffracted wave refers to a convergent spherical wave with no aberration on the scanning plane. Furthermore, since the playback area changes as the disk rotates, the following discussion will be limited to the center of the scan (of course, the same argument holds true for areas other than the center of the scan).

Therefore, in FIG. 1 (bl), if the incident wave satisfies (2) at all points within the reproduction area S while the area S incident on the disk is the scanning center.

It can be seen that at least at the center of the scan, aberrations are completely eliminated. Therefore, with a hologram lens for aberration correction, ■
It is designed so that a diffracted wave 5 having a phase satisfying the following is emitted.

At this time, in FIG. 1(a), the angle of incidence on the aberration correction hologram lens 1 is set to 04. Also, each output is θh
Then, the beam diameter of the diverging light 4 of the semiconductor laser is converted to (cos θb/cos θa) times in the direction parallel to the plane of the paper.

Semiconductor lasers typically have an elliptical beam in the far field pattern.

This is because the exit port is large in the direction parallel to the joint, and small in the direction perpendicular to the joint.

As a diffraction image, the far-field image in the direction perpendicular to the junction is better.

This is because it is larger than that in the direction parallel to the joint.

Usually, a cylindrical lens and a prism pair are used to shape this elliptical beam, but these are expensive. But according to one method.

If the direction perpendicular to the semiconductor laser junction, that is, the direction where the beam divergence angle is large, is set parallel to the plane of the paper.

The beam in the direction with a large divergence angle is (cosθb/
Since the beam is converted by a factor of cos θ4), beam shaping can be easily performed.

The above functions allow a simple configuration of a semiconductor laser, an aberration correction hologram lens, and a hologram scanner (scanning hologram lens).

We can provide an inexpensive and highly reliable all-hologram optical beam scanning device that does not involve any imaging lens, has a beam shaping function, and solves the problems of astigmatism, coma aberration, and mode hopping at the same time. can do.

(Specific design of the light beam device (Fig. 2)) Fig. 2 shows the design of Fig. 1 (a) for preventing the influence of mode hopping.
This is a specific design example of a light beam device of 1. First, as a design parameter of the linear scanning hologram scanner 3, the distance from the scanner 3 to the two diverging spherical wave light sources A1 and A2 at the time of creation is f H+ = f H2 = 125.7
mm, radius R from central axis 3a to hologram incident point P = 40 mm, two light sources A1 from hologram incident point P
And the distance on the y coordinate to A2 is also set to R = 40 + u, hologram incident angle θ + = 47.25°, and a He-Cd laser with a wavelength of 325 nm is used to create the hologram, and a semiconductor laser with a wavelength of 787 nm is used for reproduction. It is designed with this assumption in mind. At this time, the diffraction angle at the center of the scan is also 4
7.25.

becomes. The above-mentioned light beam scanning method is based on a method for which three patents have been filed by the present applicant (patent application number 59-659).

Note that the three patent applications No. 59-659 are due to large scanning position fluctuations due to eccentricity and surface wobbling of the hologram disk in the above-mentioned Japanese Patent Application Laid-Open No. 57-2018 filed by the ninth applicant, and the Bragg angle condition is not satisfied.

This is an improvement over the problem of low light utilization efficiency.

Also, the oscillation wavelength of the semiconductor laser varies by ±10 depending on the loft.
Although it varies by about nm, the average value is 2 usually 782 nm.
Therefore, this was selected as the reproduction wavelength. Shigashi.

It will be shown later that according to this patent, deterioration of scanning characteristics (linearity, etc.) due to variations of ±10 nm in the oscillation wavelength of a semiconductor laser can be prevented.

Next, a method for setting the diffraction angle of the aberration correction hologram lens will be explained. First, the scanning hologram lens incidence angle θ+ = 47.25°.

The incident angle of the diffracted wave 5 is also θ+ = 47.25°. At this time, from Figure 2, tanθ1=(ayR)/a, and since R=40ml, a=IQm,
Set ay = 50.8 mm. Next, in the light beam device set as above, two oscillation wavelengths of 787 nm were set.
In order for the wavelength of the semiconductor laser to return to the imaging point 7 after hopping by 1 mode = 0.3 nm, the deviation angle Δθt of the output angle of the diffracted wave 5 from the aberration correction hologram lens 1 shown in FIG. 2 must be 0. Numerical calculations show that .045 is sufficient. Now, the central diffraction angle of the aberration correction hologram lens 1 is set to θ, and the amount of wavelength shift due to mode hopping is set to Δλ.
,Also. Let f be the center spatial frequency of the hologram lens 1.

There is a relationship between On the other hand, the center oscillation wavelength of the semiconductor laser is λ
If so.

λ tan θ i −−・Δθd ...■Δ λ. Now, λ-787nm = 7.87X 10-'
11m+, Δλ-0,3tm = 0.3 X 1
0 N, Δθi = 0.045° = 0.039×
(π/180) rad, so by substituting these values into equation 0, θ〆=64.28°. Namely.

By setting the central diffraction angle of the hologram lens 1 to 64.28°, the influence of mode hopping can be minimized. From this, in FIG. 2, the aberration correction hologram lens 1 is placed against the hologram scanner 3.

θ=θ to θ+ = 64.28-47.25 = 1
It can be seen that the setting should be made at an angle of 7.03°. Note 1
The above example uses one mode hop, but you can also do more mode hops.

The above settings are fine.

By setting as described above, it is possible to provide a light beam scanning device in which the influence of mode hopping is suppressed.

(Method for creating a hologram lens for aberration correction (Fig. 3)) Next, as a method for manufacturing a light beam scanning device, a method for creating a hologram lens for aberration correction 1 will be explained using the explanatory diagram in Fig. 3(a). I do. First, a method for correcting aberrations of the scanning hologram lens will be described. The difference from Figure 2 is in Figure 3 (C).

First, the light 8 incident on the aberration correction hologram lens 1 is vertical parallel light of a semiconductor laser beam. For other parameters, the previously described design values will continue to be used. Now, the third
When trying to create the aberration correcting hologram lens 1 shown in FIG. 1A, there is generally no photosensitive material that can record the reproduced wave as a hologram with high efficiency when using semiconductor laser light.

Therefore, consider creating the hologram lens 1 using a laser beam having a shorter wavelength than that of a semiconductor laser beam.

In this case, the wavelength of the semiconductor laser light (regenerated wave) is λ21, and the wavelength of the created wave is λ1. Namely.

λ2>λ1.

In Fig. 3fa), when the incident beam diameter DH of the incident wave 5 on the hologram scanner 3 is increased in order to reduce the diameter of the imaging beam at the imaging point 7, the aberrations generated by the hologram scanner 3 cause the imaging Astigmatism and coma aberration occur at point 7.

Therefore, the created wave of the wavelength λ1 of the hologram lens 1 may have an aberration that cancels the astigmatism and coma aberration. In other words, by reproducing at λ2, φrN (x, y) = φo
A wavefront that can generate a phase of ur (X, )') - φs (x, y) may be created at wavelength λ1. Through calculations, it has been found that the aberration at wavelength λ1 for this purpose may be so-called outward coma aberration. This outward comatic aberration can be generated using the so-called prism effect of the lens. In other words, when the convergent spherical wave 12 shown in FIG. 3(b) enters the concave lens 9 tilted by a predetermined angle α at a distance y2 from the optical axis, the output wave becomes an outward convergent comatic aberration wave 13. . This is used as an object wave for creating the hologram lens 1. The coma aberration wave 13 in this case is set so that when reproduced by a semiconductor laser, it has exactly the same relationship as the diffracted wave 5 in FIG. 3(a). However, the direction of the hologram lens should match the direction indicated by ■. At this time, 1 created wavelength λ+ (488mm.

Ar laser), as each parameter of the concave lens 9.

Lens thickness D○+ = 20.99 m, refractive index 1.5
52 (wavelength 488 nm), curvature R2 = 65 m, incident position y2 = 16.71 Tsuru, distance y from the optical axis of the incident focus
3 = 28.06 fins, input focal length f 2 = 1
12.3 m, tilt angle α = 17.7°, distance between concave lens 9 and hologram photosensitive surface 12 = 140 **, horizontal distance from the center of hologram photosensitive surface to concave lens 9 63
= 81 mm, and an optimal outward comatic aberration wave 13 was obtained. As shown in FIG. 3(b), the reference wave is a vertical plane wave.

The light beam scanning device shown in FIG. 3 (11) is constructed using the hologram lens 1 created as described above.

Of course, at this time, when a semiconductor laser (λ2) of vertical parallel light is incident on this hologram lens, the central diffraction angle is 64
．． It becomes 28°. However, the configuration in FIG. 3(a) has the same configuration parameters as in FIG. 2. The difference is that the light incident on the aberration correction hologram lens is vertical parallel light (λ2) from a semiconductor laser.

Next, FIG. 4(a) shows an aberration image of the scanning diffracted wave 6 from the scanning hologram scanner of FIG. 3(a) at this time. Here, considering application to a laser printer, it is assumed that A4 (216 mm) is scanned.

1. The normally required beam diameter is shown in FIG. 1(b).

The aberration image when the scanning hologram incident beam diameter DH is determined in order to make this beam diameter a diffraction image is shown in the same figure (al).The imaging distance is 337 m, and the incident diameter DH is 3.8 m.
It is m. It can be seen from this that the one-line method scans almost completely without aberration. Note that this hologram lens 1 is not used in FIG.

The beam diameter is shown when using an aberration-free imaging lens. It can be seen from this that significant aberration correction has been made.

In addition, in Fig. 6, in order to obtain the beam diameter of Fig. 4 (bl), φ, N (x, y) = φ (x, y) - φ + (x, y)
The ideal aberration correction calculated using the formula is shown below, and from this it can be considered that the present method is a near-ideal aberration correction.

As described above, a method for creating an aberration-correcting wavefront for a scanning hologram lens was obtained. However, the light incident on the aberration correction hologram lens is parallel light (λ2) from the semiconductor laser, and an optical system is required to convert the diverging light from the semiconductor laser into parallel light.

Next, a method for capturing the diverging light of the semiconductor laser will be described.

For this purpose, it is sufficient to find a method to convert the diverging light of the semiconductor laser into parallel light. Regarding this, the present applicants have already applied for a patent (qrAo6o%3+1go*In
) As shown in FIG. 7 (al), a semiconductor laser with an oscillation wavelength of 787 nm passes through a glass cap (here, the thickness is 9.3 mm and the refractive index is 1.5 as general values).

A method for creating a hologram lens that converts aberrated diverging waves into parallel lights will be described. This is the wavelength λ lower than the reproduction wavelength.
To create a waveform with 1, a so-called positive spherical aberration wave is required. But with holograms.

Since the spacing between the aberration generating optical systems is usually narrow, there is noise due to multiple interference and it is difficult for one of the created waves to enter easily.Therefore, in the above-mentioned patent application.

A method was adopted in which the negative spherical aberration waves were once crossed and recorded as positive spherical aberration.

In FIG. 7 (bl as well, the hologram creation wavelength is assumed to be Ar laser (488 nm). When this convergent spherical wave 10 enters the convex lens 8, the output wave therefrom becomes a negative convergent spherical aberration wave. Once the spherical aberration waves intersect at the intersection θ, they can be turned into a positive diverging spherical aberration wave 11. This positive diverging spherical aberration wave is used as a created wave for creating the hologram lens 1. , the other created wave is assumed to be a vertical parallel wave here.

Figure 7+ shows the hologram lens created by this aberration wave.
As shown in a), the parameters that cause the aberration wave are optimized so that the beam becomes parallel. At this time, in Fig. 7(a), if parallel light is incident on the hologram lens and the convergent light is narrowed down to the 2-diffraction limit after passing through the glass window of the semiconductor laser, then the convergence point will be the semiconductor laser. It can be seen that parallel light can be obtained by positioning the laser exit. Therefore, Figure 7 (
In a).

The parameters of the aberrational optical system should be adjusted so that the aperture can be narrowed down to the diffraction limit, that is, so that the wavefront aberration is minimized.

It was optimized using the damped least squares method. As a result.

As each parameter of the convex lens 8, lens thickness d=7.
62mm, curvature R+ = 26.289m, lens refractive index 1.73903 (488nm), entrance focal ratio 1
11t f + = 31m.

The distance 1l between the convex lens 8 and the hologram photosensitive surface is 32.
By setting the distance to 4 m, an optimal positive diverging spherical aberration wave 11 was obtained.

As a result, this hologram lens has a semiconductor laser (λ2778
7 nm), the wavefront aberration after passing through the glass window is NAo 33, the maximum is less than 0.1λ, and R
Since it is below Ayleigh's 1/4 wavelength rule, it can be said to be a hologram lens close to the 3rd diffraction limit. Further, the focal length is 10.75011. Therefore, the hologram lens created with these parameters is f
If E=10.750m, it becomes parallel light.

Therefore, when a hologram is created and reproduced by replacing the vertical parallel light that is the reference wave in Fig. 3 (bl) with the aberration wave in Fig. 7 (b), the diverging light from the semiconductor laser first becomes virtual. This virtual parallel light is converted into parallel light and is an object wave.It can be seen that an aberration wave that corrects the aberration of the scanning hologram lens can be generated.In other words, the diverging light from the semiconductor laser is taken in and the scanning hologram lens The method for creating a hologram lens that generates an aberration correction wave is as shown in Figure 3 (C).The parameters are as described above.The hologram lens created in this way is set as shown in Figure 2.Then, the semiconductor The distance fl between the laser exit aperture and the aberration correction hologram lens may be set to 10.750 m.According to this embodiment.

Using only a semiconductor laser, an aberration correction hologram lens, and a scanning hologram lens, highly accurate linear scanning with almost no aberrations is possible. In addition, B J, 4″L in Fig. 4(b)
In order to obtain N of this aberration correction hologram lens,
Since A only needs to be 0.3, in this example, this N A
= 0.33 aberration correction is sufficient.

Also, regarding mode hopping at this time, since the settings shown in Figure 2 were made, the sub-scanning direction was 7 μm (scanning center) for mode hopping of 0.3 nm.

8μm (scanning edge), and scanning direction maximum 45μm (
It was found that it was possible to significantly reduce the scanning edge).

Also, the beam shaping ratio in this case is (cos (64, 28
°)/cos(0°)) = 0.43 times. Furthermore, it was found that even with a laser having a deviation of ±10 nm from the design wavelength of 787 nm, the scanning characteristics (linearity, etc.) are good according to this method. Note that this aberration correction hologram was created because the necessary transfer function was known.

Needless to say, it is also possible to directly draw this with an electron beam or create it with CGH. or.

Here, the incident angle θα of the semiconductor laser in FIG. 1 is set to Oo, but it goes without saying that the angle of incidence is not limited to this.

Further, the auxiliary optical system for aberration correction is not limited to a single spherical optical element.

Of course, it is also possible to use an aspherical optical element.

〔Effect of the invention〕

According to the present invention, problems caused by astigmatism and coma aberration and mode hopping can be simultaneously solved by a configuration consisting of only a semiconductor laser, an aberration correction hologram lens, and a scanning hologram lens, and an inexpensive and highly accurate light beam scanning device is provided. and,
It becomes possible to provide a specific manufacturing method thereof.

[Brief explanation of drawings]

Figure 1 (al is a side view of the configuration of the optical beam scanning device. Figure 1 (b) is a configuration diagram of the hologram scanner for explaining the relationship between the phase of the incident wave and the phase of the diffracted wave. FIG. 3 is a side view showing a specific design of the light beam scanning device. FIGS. Figure (a) is a diagram showing an aberration image of the scanning diffraction wave by the light beam scanning device of Figure 1. Figure 4 (b) is a diagram showing the beam diameter on the scanned surface. Figure 6 shows an ideal aberration image of the scanning diffracted wave to obtain the beam diameter of Figure 4(b) when an aberration-free converging lens is used. Figure 7 (a) is a diagram showing a method for creating a hologram lens that converts diverging waves from a semiconductor laser into parallel light. Figure 7 (bl is a diagram showing a method for creating a hologram lens). Figures (- are side views. Figure 9 (a) is a perspective view of the configuration of a conventional example for solving the problem of astigmatism. Figure 9 (b) is a side view of Figure 9 (a). An explanatory diagram showing a method of manufacturing a hologram lens for point aberration correction. Fig. 11 is a side view of the configuration of a specific conventional example for solving the mode hopping problem. Fig. 12 (a) is a mode hopping A side view of the basic configuration of another specific conventional example for solving the problem. FIG. 12(b) is a side view of the configuration of another specific conventional example for solving the mode hopping problem. 1... Hologram lens for aberration correction. 2... Semiconductor laser. 3... Hologram scanner. 4... Diverging spherical wave. 5.6... Diffraction wave. 7... Imaging Point. 8... Convex lens. 9... Concave lens. 10.12... Convergent spherical wave. 11... Positive diverging spherical aberration wave. 13... Outward comatic aberration wave. DH... Beam diameter. α ... Inclination is angle. Force - beam angle ξ 1L configuration fork lunar bow plane view Figure 1 (
α) Reproduction (0) Fig. 1 (b) Design β9 Design Fig. 2 Fig. 3 (G) Fig. 3 (b) Water for aberration correction Rob 'Ram Les Lesbian from above Figure 3 (O
) On the surface to be scanned, the target is shown in Figure 4 (b) (Q) A above center X! ○mm -3゜ Thread reading image S, for vf 2 fans % A kita toh 5th
Diagram (A4 shore) 8° IQ' 12°) ε's cutting 5 pieces ξ L's, palm, X-0mm whispering. '2''
4°
6°-angle, scanning diffraction 5I! , the ideal of , r, -J and kumei image Fig. 6 Scanning end 11th view for holophparamresis'S (・1; Memu k's nine-heem principle Figure 8 (0) #+, figure (b) Easy l and solution ζ′1′ufchσ)
-44 Shikami also Ikuri Figure 9 (O) #+ Neko figure (b) Ikairi @ figure mode soi%, 11hi: °ref'me FAI! JΣ solution next T
10th principle of "force that praises the first day" mode 88. ＃-, &ilof second -ne dshi marriage aiku bow (iikuyumi side) 5ri)(
0) Basic configuration (4-rule J side view) → Ri (b) 堝-Tsume (side view) Solving the mode hora and undime problems, drawing (Roninu N death n J coming hard ゛J Fig. 12)

Claims (3)

[Claims] (1) In a light beam scanning device in which a reproduced wave emitted from a laser is incident on a scanning hologram lens having a positionally different spatial frequency distribution and the scanned surface is scanned by the diffracted wave, the laser is a semiconductor laser, and the laser is a semiconductor laser; A light beam scanning device comprising an aberration correction hologram lens that converts a wavefront of a reproduced wave to reduce aberrations of the diffracted wave on the scanned surface. (2) The aberration correction hologram lens is disposed on the optical path of the reproduced wave between the semiconductor laser and the scanning hologram lens, and the diffraction angle on the aberration correction hologram lens is determined by the scanning hologram lens. Claim 1, characterized in that the change in the scanning point on the scanned surface due to the diffracted wave from The light beam device device described in . (3) In a method for manufacturing an optical beam scanning device, a laser beam having a wavelength λ_1 shorter than the wavelength λ_2 of a reproduced wave, which is a laser beam, is used, a spherical aberration wave is used as a reference wave, and a coma aberration wave is used as an object wave to produce an aberration correction hologram. A method for manufacturing a light beam scanning device, comprising the step of creating a lens.