JP2967885B2 - Hologram disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram disk for generating a multi-scan beam capable of simultaneously scanning a plurality of laser beams.

[0003]

2. Description of the Related Art A hologram disk is a core component for scanning a laser beam instead of a polygon mirror, and scans a laser beam on a predetermined scanning line by rotating the disk.

[0004] The structure of the hologram disk will be described with reference to FIG. In the figure, the hologram disk 11 is divided into a plurality of sectors 11-1 to 11-6, diffracts the wavelength lambda ₀ the laser beam 12 incident here on a predetermined scanning line 13, the rotary shaft 14 The scanning line 13 is scanned by the rotation about the center. That is, one laser beam scan is performed in one sector.

Each sector (hologram grating) 11-1 to 11-6
Will be described with reference to FIG. Here, a phase type hologram disk having a relief structure is considered. As the structure of the hologram grating shown, a plurality of grooves 16 of depth d ₀ which was formed with a predetermined pitch, the pitch of the grooves 16, and the wavelength of the laser beam scanned by the hologram, a laser times It is determined by the angle.

In the case of a phase type hologram disk, the diffraction of the laser beam 12 mentioned above depends on the depth d ₀ of the groove 16 of the hologram grating shown in FIG.
Is caused by the phase modulation of the laser beam 12 passing therethrough. The laser beam passing through this groove 16 and the groove
The phase difference from the laser beam passing through a portion other than 16 is obtained from the following equation, assuming that the laser beam 12 is perpendicularly incident on the hologram disk 11.

[0007] phi = In (2π / λ) d (n s -1) ...... (1) where, phi is a phase difference, the wavelength of lambda is the laser beam, d is the groove depth, n _s is a hologram disc Indicates the refractive index of the substrate to be formed.

A general hologram disk shown in FIG.
For 11, in order to diffract the laser beam having a wavelength lambda _theta should satisfy the following equation.

Φ = (2π / λ _θ ) d (n _s -1) (2) where φ ≠ k (2π) k: integer Here, φ = k (2π) is not satisfied. The reason why the phase difference is not an integral multiple of 2π is that if the phase difference is an integral multiple of 2π, the phase difference disappears and diffraction does not occur.

Incidentally, as such a hologram disk, there is a hologram disk for generating a multi-scan beam capable of simultaneously scanning a plurality of laser beams. Conventional multi-scan beam generation hologram discs have a structure in which laser beams from the same direction are diffracted onto different scan lines, and a plurality of independent hologram discs are scanned on each scan line by rotating the disc. Things. FIG. 7 shows the structure of the hologram grating portion of the hologram disk for generating multiple scans.

The hologram disk 21 is configured to have two scanning lines. As shown in FIG. 8, the laser beam (wavelength λ ₀ ) 12 incident on the hologram
The light is diffracted on the two scanning lines 13a and 13b, and is simultaneously scanned on the respective scanning lines 13a and 13b by the rotation of the hologram disk 21. A practical example of such a plurality of scanning lines is a scanner for reading a barcode in a POS.

[0012]

However, in such a conventional hologram disk 21 for generating multiple scans, when the incident laser beam 12 is subjected to intensity modulation, it is diffracted onto different scanning lines 13a and 13b. The same intensity modulation is applied to each laser beam. Therefore, when different intensity modulation is required on each scanning line, for example, in the case of an optical system of a laser color printer, the above-described conventional hologram disk 21 for generating multiple scanning beams cannot be used. Therefore, in the optical system of the laser color printer, as shown in FIG. 11, the hologram disk described in FIG.
The hologram disk 11 is provided with a laser beam 12 from a laser oscillator 24 via a modulator 25.
And the hologram disk 11 is rotated by the motor 26 to scan the corresponding photosensitive drum 23 with the laser beam.

An object of the present invention is to provide a hologram disk which can generate a plurality of scanning beams by using laser beams of a plurality of wavelengths and which can be applied even when it is necessary to independently apply intensity modulation to each of the plurality of scanning beams. To provide.

[Configuration of the Invention]

[0015]

A hologram disk according to the present invention receives a plurality of laser beams having different wavelengths, diffracts these laser beams onto predetermined scanning lines, and adjusts the laser beams by a rotating operation. The scanning is performed on a scanning line, and among the plurality of laser beams, a laser beam of a corresponding wavelength is diffracted onto a desired scanning line and a laser beam of another wavelength is not diffracted. A hologram for each laser beam, which is designed so that a plurality of grooves with a set depth are arranged at a predetermined pitch, has their groove structures overlapped, and the portion where the groove peaks and the groove troughs overlaps from the groove peaks. A groove with a depth obtained by subtracting the depth of the valley, and a groove with a depth that is the sum of the depths of these valleys is formed where multiple valleys overlap. It is intended.

[0016]

According to the present invention, when a plurality of laser beams having different wavelengths are incident on a hologram disk, each laser beam is phase-modulated by the depth of a groove corresponding to its own wavelength, and is diffracted on a corresponding scanning line. Then, scanning is performed on a scanning line by rotation of the disk. Although laser beams of other wavelengths are also incident on each groove, diffraction does not occur with respect to laser beams of other wavelengths because the depth is set so that the phase is not shifted. That is, the laser beam of each wavelength is phase-modulated by the groove of the depth set for itself, causes diffraction, and is scanned on the corresponding scanning line. Therefore, by independently applying intensity modulation to the laser beam incident on the hologram disk, it becomes possible to perform independent intensity modulation on each scanning line.

[0017]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a hologram disk according to the present invention.
31 shows the structure of a hologram grating portion of FIG. The structure shown is for two wavelengths. This hologram grating has a structure in which the hologram grating 31a shown in FIG. 2 and the hologram grating 31b shown in FIG. 3 are overlapped.

Here, the hologram grating 31a shown in FIG.
Is a plurality of grooves 36a2 of the depth d _1, forms at a predetermined pitch, also holographic grating 31b shown in FIG. 3, the depth D
_A plurality of _two grooves 36b2 are formed at a predetermined pitch.

In these hologram gratings 31a and 31b, the phase amount of the incident laser beam is expressed by the following equations (3) and (6).
Is configured to satisfy the following condition.

[0021] _{φ 1 λ 1 = (2π /} λ 1) d 1 (n s -1) = i (2π) + Δφλ 1 i: integer _{Δφλ 1 <2π ...... (3)} φ 1 λ 2 = (2π / λ ₂ ) d ₁ ( _ns −1) = j (2π) j: integer (4) φ ₂ λ ₁ = (2π / λ ₁ ) d ₂ ( _ns −1) = nn: integer (...) _{5) φ 2 λ 2 = (} 2π / λ 2) d 2 (n s -1) = m (2π) + Δφλ 2 m: integer Δφλ ₂ <2π ...... (6) the formula (3) to (6) , Φ ₁ λ ₁ , φ ₁
λ ₂ is the wavelength λ by the hologram grating 31a shown in FIG.
₁ and ₂ show the phase amounts of the laser beams, respectively. φ ₂
λ ₁ and φ ₂ λ ₂ indicate the phase amounts of the laser beams of wavelengths λ ₁ and λ ₂ by the hologram grating 31b shown in FIG. 3, respectively.

In the hologram gratings 31a and 31b, wavelengths (hologram gratings) other than wavelengths designed to diffract a desired scanning line (λ ₁ for the hologram grating 31a and λ ₂ for the hologram grating 31b) are used. In scanning by a laser beam of λ ₂ for the laser beam 31a and λ ₁ ) for the hologram grating 31b, the phase amounts of the laser beams of these wavelengths are calculated as shown in the above equations (4) and (5). , So that diffraction does not occur due to an integral multiple of 2π.
The depths d ₁ and d _{2 of} b are set.

That is, these hologram gratings 31a, 31
b diffracts a laser beam of a corresponding wavelength (λ ₁ for the hologram grating 31a and λ ₂ for the hologram grating 31b) of a plurality of incident laser beams onto a desired scanning line, Other wavelengths (hologram grating 31a
_{2 λ} for, for the hologram lattice 31b λ ₁₎
Grooves 36a and 36b so that no diffraction occurs in the laser beam
The depths d ₁ and d ₂ are set, and these grooves 36a and 36b are arranged at a predetermined pitch.

As described above, the hologram disk 31 shown in FIG. 1 is similar to the hologram grating 31 shown in FIGS.
a and 31b are overlapped and integrally formed. That is, the hologram gratings 31a and 31b for each laser beam designed as described above are superimposed on the structures of the grooves 36a and 36b so that the groove 36a1 or the groove 36b1 and the groove 36b2 or the groove 36a2 overlap. Forms a groove of a depth obtained by subtracting the depth of the groove valley 36b2 or the groove valley 36a2 overlapping from the groove ridge 36a1 or the groove ridge 36b1. A groove having a depth equal to the sum of the depths is formed.

The hologram disk 31 shown in FIG.
As shown in the figure, of the incident laser beams 32a and 32b, the laser beam 32a of the wavelength λ ₁ is the corresponding scanning line 33a.
When the hologram disk 31 rotates, the diffracted laser beam 32a is scanned on a scanning line 33a. Similarly, the laser beam 32b of wavelength λ ₂ is
The laser beam 32b is scanned on a scanning line 33b by the rotation of the hologram disk 31.

That is, the laser beam 32a having the wavelength λ ₁
Is subjected to phase modulation by the depth d ₁ of the groove formed in the hologram disk 31 and causes diffraction to the scanning line 33 a as described above, but the phase amount due to the depth d ₂ is an integer of 2π as described above. Since it is twice, there is no phase shift as a result and it does not participate in diffraction. Similarly, the laser beam 32b of the wavelength λ ₂ is phase-modulated by the depth d ₂ of the groove formed in the hologram disk 31 and causes diffraction to the scanning line 33b, but the phase amount due to the depth d ₁ is 2π. Because it is an integer multiple of, there is no phase shift,
Not involved in diffraction.

As described above, the laser beams 32a and 32b having the wavelengths λ ₁ and λ ₂ are diffracted by the hologram disk 31 onto the corresponding scanning lines 33a and 33b, respectively. Scan simultaneously on 33b.

The laser beams 32a having wavelengths λ ₁ and λ ₂
, 32b can be independently modulated on each of the scanning lines 33a, 33b.

Next, a specific example will be described. Helium neon laser (wavelength 633 nm) and argon laser (wavelength 515)
3 shows the depth of the groove of the hologram disk when a hologram disk that handles two wavelengths (nm) is designed.

Here, the hologram disk is made of glass, and its refractive index is n = 1.6. The depth of the groove is as follows from the above-described equations (3) and (6).

D ₁ = 0.8583 μm d ₂ = 1.055 μm d ₁ + d ₂ = 1.913 μm The hologram disk 31 described with reference to FIG. 4 is applied to a scanning unit of a laser printer to print two lines simultaneously. FIG. 5 shows an example of speeding up. In the figure, laser beams 32a and 32b of wavelengths λ ₁ and λ ₂ emitted from laser oscillators 24a and 24b are modulated by modulators 25a and 25b based on image information of lines to be drawn, respectively, and then reflected by mirror 38. Are converted into a single beam via the beam splitter 39, and are incident on the hologram disk 31. The hologram disk 31 converts this beam into laser beams 32a,
A predetermined scanning line 33 adjacent to the photosensitive drum 23 as 32b
Diffracts onto a and 33b, respectively. The rotation of the hologram disk 31 by the motor 26 causes the scanning line
Scan on 32a and 32b simultaneously.

That is, the hologram disk 31 of this example
Is the next line of a line laser beam 32a of the wavelength lambda ₁ is scanned, the laser beam 32b of the wavelength lambda ₂ is designed to scan. Therefore, as described above, the printing speed is increased by the simultaneous drawing of two lines. It is also designed so that this scanning is performed with almost no distortion of f and θ and no curvature of the scanning line.

In the example shown in FIG. 6, laser beams 32a, 32b, 32
c, 32d are replaced with four photosensitive drums 23a, 23b, 23c, 23
The light is condensed on the scanning line corresponding to d, and the scanning is performed such that the rotation of the hologram disk 31 hardly causes the distortion of f and θ and the curvature of the scanning line. That is, the laser oscillator 24a, 24b, 24c, the wavelength lambda ₁ emitted from _{24d, λ 2, λ 3,} λ 4 of the laser beam 32a, 32b,
After modulating 32c and 32d by the modulators 25a, 25b, 25c and 25d based on the image information of the lines to be drawn, respectively.
Via the reflecting mirror 38 and the beam splitter 39 and one beam, is incident on the hologram disk 31, the hologram disc 31, the wavelengths _{λ 1, λ 2, λ 3} , λ 4 each of the laser beams 32a, 32b, 32c , 32d are diffracted onto the corresponding photosensitive drums 23a, 23b, 23c, and 23d, respectively, and are further scanned simultaneously by rotating the hologram disk 31 by the motor 26.

In each of the above examples, the hologram disc is used as a scanning unit of a laser printer.
The present invention is not limited to this, and can be applied to a scanning unit of any device that requires laser beam scanning.

[0035]

As described above, according to the present invention, it is possible to generate a multi-scan beam by using a multi-wavelength laser. It is possible to do. For this reason, the present invention can be applied to various types of laser scanning that cannot be applied to the conventional hologram for generating multiple scans, and the range of use can be expanded.

[Brief description of the drawings]

FIG. 1 is an enlarged perspective view showing a hologram grating portion in an embodiment of a hologram disk according to the present invention.

FIG. 2 is a perspective view showing a hologram grating which is a basis of the hologram grating shown in FIG.

FIG. 3 is a perspective view showing a hologram grating superimposed on the hologram grating shown in FIG. 2 to form the hologram grating shown in FIG. 1;

FIG. 4 is a perspective view showing a state of diffraction of a laser beam by the hologram disk shown in FIG.

FIG. 5 is a perspective view showing a configuration example in which the hologram disc shown in FIG. 4 is used for a scanning unit of a laser printer.

FIG. 6 is a perspective view showing another configuration example in which the hologram disk shown in FIG. 4 is used for a scanning unit of a laser printer.

FIG. 7 is a perspective view showing a hologram grating portion of a conventional hologram disc for generating multiple scans.

8 is a perspective view showing a diffraction state of a laser beam by the multi-scan generation hologram disk shown in FIG. 7;

FIG. 9 is a perspective view showing a diffraction state of a laser beam by a conventional single-scan hologram disk.

FIG. 10 is a perspective view showing a hologram grating portion of the hologram disk shown in FIG.

FIG. 11 is a perspective view showing a configuration example in which the hologram disk shown in FIG. 9 is used for a scanning unit of a laser printer.

[Explanation of symbols]

 31 Hologram disk 32 Laser beam 33 Scanning line 36a, 36b Groove 36a1, 36b1 Groove 36a2, 36b2 Groove

Claims (1)

(57) [Claims] A hologram configured to receive a plurality of laser beams having different wavelengths, diffract the laser beams onto predetermined scanning lines, and scan the laser beams on the corresponding scanning lines by a rotation operation. A plurality of grooves each having a depth set so that a laser beam having a corresponding wavelength among the plurality of laser beams is diffracted on a desired scanning line and a laser beam having another wavelength is not diffracted. The holograms for each laser beam, which are designed so that they are arranged at a predetermined pitch, have their groove structures superimposed, and in the portion where the groove ridges and valleys overlap, subtract the depth of the overlapping groove valleys from the groove ridges. A groove having a depth that is the same as the depth of the groove, and a groove having a depth that is the sum of the depths of the grooves is formed in a portion where a plurality of grooves are overlapped. Disk.