JPS62113126A - Optical information processor - Google Patents

Abstract

PURPOSE:To permit high-speed information recording of multiple gradations and multiple values with simple constitution and to permit halftone copying and increase in the capacity of an optical disk by providing a semiconductor laser, wavelength changing means and imaging optical system and driving the wavelength changing means by a multiple gradation signal. CONSTITUTION:Laser light emitted from the semiconductor laser 1 is made to parallel luminous fluxes by a collimate lens 2 and the fluxes are deflected by a rotary polygon mirror 4 rotating in the direction of an arrow 3 so as to image a spot 7 on the surface of a photosensitive drum 6 by an imaging lens 5. A power source 8 changes the current to be passed to the semiconductor laser 1 by the multiple-gradation recorded information to change the wavelength of the semiconductor laser 1. The laser light emitted from the semiconductor laser 41 is made to the parallel luminous fluxes by the collimate lens 2 and the spot 45 is imaged on the surface of the disk 44 by a stopping down lens 43 in the case of using this device for an optical disk device. The light reflected from the disk 44 is conducted by a lambda/4 plate 46 and a polarizing beam splitter 47 to a known out of focus detecting system 48.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical information processing device, and in particular to a recording optical system suitable for a laser beam printer using a semiconductor laser, an optical disk device, an optical card device, etc. Regarding.

[Conventional technology]

The recording optical system of conventional laser beam printers.

Institute of Electrical Communication Engineers side “Practical laser technology” (October 1982)
As described on pages 49 to 54 of
It consists of a gas laser such as e-Ne and a light intensity modulator, a rotating polygon mirror, an Fe lens, and a photosensitive drum. While the spot was scanning, the light intensity of the spot was modulated by a light intensity modulator to record a dot of a constant diameter on the surface of the photosensitive drum.

Furthermore, in the recording optical system of a laser beam printer using a semiconductor laser as a light source, dots of a constant diameter are recorded by directly modulating the intensity of the emitted light from the semiconductor laser instead of using a light intensity modulator.

However, conventional laser printers primarily process information such as characters and lines in which black areas and white areas can be clearly distinguished, so they do not take into consideration the recording of so-called halftone information such as photographs.

[Problem that the invention seeks to solve]

In the recording optical system of the conventional laser beam printer mentioned above,
No consideration was given to multi-gradation recording in which the color changes continuously from black to white, and there was a problem in that excessive contrast was produced in copies of photographs and the like.

An object of the present invention is to provide an optical information processing device that realizes multi-gradation recording that continuously changes from black to white with an N-unit configuration.

[Means for solving problems]

The above purpose is to provide a semiconductor laser, a wavelength changing means that changes the driving current of the semiconductor laser to change the laser emission output and also changes the laser wavelength, a collimating lens that converts the emitted light of the semiconductor laser into a parallel beam, and a collimator lens that converts the emitted light of the semiconductor laser into a parallel beam. An imaging lens (F
This is achieved by driving the wavelength changing means with a multi-gradation information signal, and an imaging optical means, such as an optical lens (e-lens), in which these lens systems have chromatic aberration as a whole.

[Effect]

The wavelength changing means changes the wavelength of the semiconductor laser using the multi-gradation information signal. The imaging optical means changes the focal position in the optical axis direction for different wavelengths of the laser due to chromatic aberration. Therefore, according to the multi-gradation information signal, the laser wavelength changes, the focal position of the light beam focused on the photosensitive drum surface changes in the optical axis direction, the diameter of the spot on the photosensitive drum surface changes, and recording is performed on the photosensitive drum surface. The diameter of the dots produced also changes. As a result, the area ratio between the black part and the white part changes, so multi-gradation recording is realized.

In addition, as the spot diameter on the photosensitive drum surface increases due to the multi-tone information signal, the laser output also increases, and the energy surface density of the spot is kept above a certain value required for exposure of the photosensitive drum. A dot of corresponding diameter is recorded.

〔Example〕

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

FIG. 1 shows a configuration IJ showing an embodiment in which the present invention is applied to a laser beam printer. 'The laser beam emitted from the f-conductor laser 1 is made into a parallel beam by the collator 1 to the lens 2, deflected by the rotating polygon fi 4 rotating in the direction of the arrow 3, and the laser beam emitted from the photosensitive drum 6 by the imaging lens 5 called an Fe lens. A spot 7 is imaged onto the surface. The power source 8 changes the current flowing through the semiconductor laser 1 according to the multi-gradation recording information, thereby changing the wavelength of the semiconductor laser 1.

FIG. 2 is an actual diagram showing the relationship between the current flowing through the semiconductor laser 1 and the laser wavelength, and the horizontal! 11112 is the current value I
, the vertical axis 13 indicates the laser wavelength λ. For example, the semiconductor laser 1 starts emitting laser light at a current value Ith = 50 mA shown at a point 111, the laser emission output PI becomes 6 mW at a current value It = 68 mA shown at a point 15, and the wavelength λs = 780 nm shown at a point 16. Become. Current value Iz indicated by point 17
= 152 mA, laser emission output Pz = 34 m
W, and the wavelength λ2 shown at point 18 = 782.8 n
It becomes m. Furthermore, the current value Is shown at point 19 = 194m
At A, the laser emission output Ps = 48 mW, and the point 20
The wavelength is 784.2 nm. A semiconductor laser oscillates at a wavelength λ that satisfies 2 n L=Nλ, where L is the resonator surface spacing at both ends of the laser, n is the refractive index, and N is an integer.

When the current is increased, the temperature of the active layer increases, and the refractive index n and the cavity length change continuously as shown by the solid line portion 21 in FIG. When the current is further increased, N becomes N-
It oscillates in the next mode, which is 1, and shows a discontinuous wavelength change as shown by the solid line portion 22. If this discontinuous wavelength change is λ2/2, as will be described later, a discontinuous wavelength change of about 0.3 nm will not be a problem. , the wavelength change Δλ=(
If the ratio of λ−λl) is expressed as α, then α=Δλ/ΔI
= 0, 0333 nm/mA.

On the other hand, the imaging lens 5 and the collimating lens 2 have chromatic aberration. The focal length of the imaging lens 5 is fo.

If the focal length of the collimating lens is fz, the amounts of chromatic aberration Δfo and Δf1 of these lenses are Δf.

It can be estimated by =fo/ν and Δfs=fs/ν.

Here, ν is the Atsube number determined by the lens material, and is approximately 430 to 60
optical glass is often used. If both lenses are made of materials with a thickness of 45, the amount of chromatic aberration for the wavelength change Δλnm is Δfo=fo ・Δλ/V', Δft=fz
・Δλ/Y', (However' = 45X170).

Assume that when a current Iz = 68 mA is caused by the radio wave 8 in FIG. 1 to flow and the wavelength is λ1 = 780 nm, the best focus of the laser beam is on the photosensitive drum surface and a spot 7 is formed. Change the current using multi-gradation recording information■
, the wavelength changes by Δλ=α(I It),
The focal point 9 where the laser beam is best narrowed down is Δ in the optical axis direction.
Z=Δf.

+Δfl(fo/ft) deviates by 2. Here, the first term on the right side is the deviation due to the chromatic aberration of the imaging lens 5, and the second term is the deviation resulting from the chromatic aberration of the collimating lens 2 being magnified by the vertical multiplication of the J6a lens 5 and the Cori2 lens 2. Therefore, a large spot 10 is imaged on the surface of the photosensitive drum 6. If the diameter of the laser beam that is parallelized by the collimating lens 2 is φ, the diameter S of the spot 10 is
It is expressed as S=φΔZ/fo, and S=(φ/ν′)・(
1+f.

If1)・Δλ. Therefore, for the same Δλ, fo
> fz, S becomes larger and more multi-tone recording becomes possible. Using Δλ=α(I-Ia), S=(
αφ/ν′)・(1+f/f1)・(I Io)
(1 formula)

In FIG. 3, the horizontal axis 12 is the current I, the vertical axis 23 is the spot diameter S, and 1 set is the actual 1iA24! It is shown by a straight line consisting of @25. In formula 1, I = I o and S = O, but the spot diameter near the most narrowed-down focus is S
= 2 fo λ/φ, so it becomes a curved line 27 that is in contact with S = 2 fo λ/φ, which is indicated by a broken line 26. fo = 500wa, ft = 50k, φ
= 20 m, a = 0.0333 nm/mA, the current If = 68 mA, shown at point 15, gives λ = 780 nm, and S = 39 p m, shown at point 28. When the current reaches Iz=152mA shown at point 17, the wavelength becomes Δλ=
5 = 80.4 shown by point 29 with a change of 2.8 nm
μm, and the spot diameter is approximately doubled. At this time, since the laser emission output is Pz = 34 mW as mentioned above, it is approximately 5.7 mW compared to Pz = 6 mW when 11 = 68 mA.
It's double. Therefore, even if the spot diameter is approximately doubled, the spot energy is 5.7 times greater, so it is sufficient to expose a dot with twice the diameter on the drum. Current point 19
If Ia = 194mA, the wavelength is Δλ = 4.2
It changes by nm and becomes 5=120.7 μm, which is indicated by point 30,
The spot diameter becomes approximately three times as large. At this time, since the laser emission output is Pa=48 mW as described above, it is eight times as much as P1=6 mW when Iz=68 mA. Therefore, the spot diameter is approximately tripled and the spot energy is eight times as large, so that a dot approximately three times the diameter can be exposed on the drum.

Here, to discuss the influence of the discontinuous wavelength change explained in Fig. 2, for example, when the current is Iz = 152 mA, the wavelength change is not Δλ = 2.8 nm but 0.3 nm.
If a large amount of 3.1 nm was generated, the spot diameter would be 80 nm.
．． Although it is 89.2 μm instead of 4 μm, the error in the spot diameter is less than 10%, so it is not a problem.
Changes in laser wavelength have a quick response of microseconds, allowing sufficiently high-speed multi-gradation recording.

According to this embodiment, the diameter is 39 μm to 12 μm with a simple configuration.
Dots down to about 0 μm can be exposed on the photosensitive drum surface at high speed, and multi-gradation information recording can be realized.

FIG. 4 is a configuration diagram showing an embodiment in which the present invention is applied to an optical disk device. The laser beam emitted from the semiconductor laser 41 is made into a parallel beam by a collimating lens 42, and a spot 45 is formed on the surface of the disk 44 by a diaphragm lens 4:3.
image. The reflected light from the disk 44 is detected by a λ/4 plate 46 and a polarizing beam splitter 47 using a known focal shift detection system 4.
Guided by 8. The focus shift detection system 48 is not related to the present invention, so its explanation will be omitted, but for example, it is composed of a convex lens, a cylindrical lens, and a 4-split photodetector, and detects focus shift using changes in beam shape due to astigmatism. A detection system or the like may also be used. The focus shift detection signal from the focus shift detection system 48 passes through a sampling circuit 49 and drives the actuator 50 of the first stop lens 43 to cause the spot 45 to follow the backlash of the disk 44 . For example, the semiconductor laser 41 starts to emit laser light at a current of 50 mA, and at 60 mA the emission output becomes 4 mW at a wavelength of 830 nm, and at 88 mA the output reaches 15 mW, a wavelength of 830.9 nm, and a wavelength of 200 mA.
The output is 60 mW and the wavelength is 834.7 nm. on the other hand.

The focal length of the collimating lens 42 is fz = 12 m, the focal length of the diaphragm lens is fo = 4.5 nn, and the Atsube number of both lenses is ν = 45 (ν' =45x170) material. The parallel beam diameter is φ=4.5 mm. When playing,
A current of 60 mA is applied to the semiconductor laser using the power supply 51, and the distance is 4 m.
The focal point of the wavelength λ=830 nm at this time is focused on the surface of the disk 44 using the focal shift detection system 48.
The sampling circuit 49 samples and holds the defocus detection signal when the semiconductor laser current is less than 80 mA, and outputs it to the lens actuator 50, so that the in-focus state is always maintained during playback. It is maintained. A laser power source 51 converts, for example, a laser current into pulses of 88 mA and 200 mA according to a multilevel information recording signal.

As in FIG. 3, the solid line 52 in FIG. 5 shows the current T on the horizontal axis 53 and the spot diameter S on the disk 44 surface on the vertical axis
The relationship is shown below. The laser current during playback is point 5.
At 60 mA, indicated by 5, the spot diameter is 1.66 μm. When the current is pulsed to 88 mA as indicated by point 57, the laser power becomes 15 mW while the spot diameter is maintained at approximately 1.66 μm, so a hole of about 1 μm is created. Next, when the current pulses to 200 mA as indicated by point 58, the wavelength changes by Δλ=4.7 nm. The spot diameter S is
S=(φ/ν')・(1+fo/fL)・Δλ, and φ
=4.5nm, γ' =45X170, fo =4.5
nu, f t = 12 nm, Δλ = 4.7 nm, and S = 3.8 μm, and the spot diameter is approximately doubled. On the other hand, since the laser emission output at this time is 60 mW, the spot energy is 60 mW÷15 mW=4 times, so the energy surface density is kept constant, and a hole of about 2 μm can be made. Further, since the sampling circuit 49 does not pass the focus shift detection signal when the laser current exceeds 80 mA, erroneous detection of focus shift can be prevented.

In the conventional 'l1iff, recording was performed using a spot of the same diameter, for example, a spot diameter of 1.66 μm, so it was difficult to make a hole of 2 μm larger than the spot diameter as in this embodiment.

According to this embodiment, the configuration is for partial use, and a hole of about 1 μm and 2
Holes on the order of micrometers can be made at high speed on the surface of an optical disk, and multilevel recording can be realized in an optical disk device.

It goes without saying that the present invention is not limited to the embodiments described above, and that, for example, a hologram lens or a grating lens can also be used.

〔Effect of the invention〕

According to the present invention, high-speed multi-gradation information recording or multi-value information recording can be performed with a simple configuration, which has the effect of enabling halftone copying and increasing the capacity of optical discs.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to a laser beam printer, FIGS. 2 and 3 are diagrams for explaining the embodiment in FIG. 1, and FIG. FIG. 5 is a block diagram showing one embodiment applied to an optical disk device, and is a diagram for explaining its operation.

Claims (1)

[Scope of Claims] 1. A recording optical system comprising a semiconductor laser and an imaging optical means for forming an image of the light emitted from the semiconductor laser as a spot on the surface of an information recording medium; What is claimed is: 1. An optical information processing device comprising: wavelength changing means for changing the wavelength of a semiconductor laser; and said imaging optical means images spots of different diameters for different laser wavelengths. 2. The optical information processing apparatus according to claim 1, wherein the image forming optical means comprises at least two separate lens groups. 3. Of the two or more lens groups, the focal length of the imaging lens group closest to the information recording medium is longer than at least the focal length of the lens group disposed on the semiconductor laser side of the imaging lens group. An optical information processing device according to claim 2, characterized in that: