JPH03197155A - Variable dot diameter recorder - 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] [Industrial Application Field] The present invention is a technology used in laser printers, etc., which enables multilevel gradation recording by changing the dot diameter for each pixel. Regarding technology.

[Prior Art] In recent years, optical recording devices have been developed that record information on paper or the like by scanning an image forming means such as a photoreceptor with a laser beam modulated by digital information from a computer, a word processor, or the like.

In such optical recording devices, in order to improve the accuracy of recorded information, it is required to realize multi-tone recording (including halftone), and there are various methods for changing the dot size of the laser beam corresponding to one pixel. Proposed.

For example, an optical recording device disclosed in Japanese Patent Application Laid-Open No. 61-113018 has a variable aperture for changing the dot size of the laser beam and a control means for controlling the amount of aperture. It's changing.

In addition, in the optical recording device shown in Japanese Patent Application Laid-Open No. 63-296069, the dot diameter of the light beam is changed by controlling the power of the semiconductor laser, and pixel information of two adjacent points are both non-irradiated. In the case of information, the dot diameter is enlarged to prevent line breakage.

[Problems to be Solved by the Invention] However, in the optical recording device described in JP-A-61-113018, the variable aperture for changing the dot size of the laser beam consists of an iris aperture or a liquid crystal aperture. Therefore, the response speed is slow, and when the write clock frequency is increased for high-speed recording, the response becomes difficult.

Furthermore, in the device of JP-A No. 63-296069,
Since the beam dot diameter is changed by changing the power of the semiconductor laser, there is a problem that the amount of change in the beam diameter is small.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, namely, to provide a variable dot diameter recording device that has a fast response speed and a large change in beam dot diameter.

[Means for Solving the Problems] In order to achieve the above object, a variable dot diameter recording device according to claim 1 of the present invention comprises a beam generating means, an ultrasonic light deflection element, and a light blocking means. , the diameter of the dot formed by the beam is changed by deflecting the beam by the ultrasonic light deflection element and blocking part or all of the beam by the light blocking means according to the deflection angle. shall be.

A variable dot diameter recording device according to claim 2 of the present invention is the variable dot diameter recording device according to claim 1, which comprises: an optical deflector for scanning a beam on an image forming means; It is characterized in that it has a scanning optical system, and the light blocking means and the scanned surface of the image forming means are in a conjugate relationship in image formation with respect to the sub-scanning direction.

[Example] The present invention will be explained in detail below.

FIG. 1 is a schematic diagram of an embodiment of the variable dot diameter recording apparatus of the present invention. FIG. 1 shows the configuration of the recording apparatus with the optical system viewed from the side, and FIG. 2 is a plan view of only the optical system of the apparatus.

In FIGS. 1 and 2, the symbol l indicates a semiconductor laser as a beam generating means. In the examples shown in FIGS. 1 and 2, a CW oscillated semiconductor laser is used as a light source, but the invention is not limited to this. , a gas laser such as a He-Ne laser, or any other laser can be used. Reference numeral 2 indicates a collimating lens, which has the function of collimating the light beam. 3
indicates a condensing lens that condenses light onto a predetermined condensing point.

Reference numeral 4 denotes an ultrasonic light deflection element installed within the condensed light beam of the condenser lens 3. The ultrasonic light deflection element 4 includes an ultrasonic medium 4-1 (PbMoO4 (lead molybdate), Tea,
, heavy flint glass, etc.).
It is constructed by adhering an ultrasonic transducer 4-2 such as Os through an electrode. By applying a high frequency to the ultrasonic transducer 4-2 and propagating the ultrasonic wave into the ultrasonic medium 4-1, a phase grating that advances in the ultrasonic medium 4-1 is formed, and light is incident on this. diffract light. By changing the frequency of the high frequency applied to the transducer 4-2, the diffraction angle of light is changed,
Light can be deflected.

Reference numeral 5 indicates a knife serving as a light shielding means disposed on a plane P including the condensing point of the condenser lens 3. The knife 5 has an end in a direction perpendicular to the minute deflection direction by the ultrasonic light deflection element 4. Reference numeral 6 indicates a collimating lens that converts the light that has been made into a divergent light flux by the knife lens 5 into a parallel light flux again, and 7 indicates a cylindrical lens.

Reference numeral 8 indicates a mirror surface of a rotating polygon mirror serving as an optical deflector for scanning a light beam on an image forming means. Reference numeral 9 indicates an anamorphic fθ lens, which uses the reflected light from the rotating polygon mirror 8 as an image forming means. It has the function of focusing light onto the body 10. The anamorphic fθ lens 9 is an fθ lens with different focal lengths in the main scanning direction and sub-scanning direction, and focuses a parallel beam on the photoreceptor scanning surface 10 in the main scanning direction, and focuses the parallel beam on the mirror surface 8 of the rotating polygon mirror in the sub-scanning direction. The beam focused on the photoreceptor scanning surface 10
It has the function of concentrating light upward. In other words, in the sub-scanning direction, the mirror surface 8 and the photoreceptor scanning surface 10 are in a conjugate relationship for image formation. Note that the anamorphic fθ lens 9 can be replaced by a lens system that combines a spherical fθ lens and a cylindrical lens.

Further, 11 indicates a high frequency power amplifier that applies a high frequency to the ultrasonic transducer 4-2, 12 indicates a voltage controlled oscillator (VCO) whose oscillation frequency can be changed depending on the input voltage, 13 indicates a semiconductor laser drive circuit, 14 shows a control circuit that outputs a control voltage 16 and a drive pulse signal 17 according to an input image signal 15.

Next, the operation of the optical system according to this embodiment will be explained.

, the semiconductor laser l is collimated by the collimator lens 2,
The condensing lens 3 condenses the light onto the P plane. An ultrasonic light deflection element 4 is disposed in the middle of this convergence, and the beam is deflected minutely by diffraction of the light. Some or all of the light is blocked. After converging on the knife face 5, the divergent beam becomes a parallel beam again by the collimator lens 6, and is condensed by the cylindrical lens 7 onto one mirror surface 8 of the rotating polygon mirror. At this time, the focusing direction coincides with the rotation axis direction of the rotating polygon mirror and corresponds to the sub-scanning direction), and in the direction perpendicular to this (main scanning direction), the zero-rotation polygon mirror 8, which remains a parallel beam, reflects and deflects the light. The light is transmitted through the anamorphic fθ lens 9.
The light is focused on the photoreceptor scanning surface 10 and scanned.

Next, a method for varying the dot diameter will be explained.

According to the halftone level of the input image signal 15, the control circuit 1
4, a control voltage 16 is generated in synchronization with the image clock. As a result, a frequency proportional to the control voltage 16 is generated by the VCO 12 and applied to the transducer 4-2 via the power amplifier 11. Ultrasonic light deflection element 4
If the change in the frequency applied to is Δfa, the angle change Δθr of the light emitted from the ultrasonic light deflection element 4 is as follows, assuming that the Bragg condition for diffraction is satisfied, where λ: wavelength of light υa: speed of ultrasonic wave Therefore, according to equation 0, when the frequency applied to the ultrasonic light deflection element 4 is changed, the output angle can be changed in proportion to the frequency applied to the ultrasonic light deflection element 4. This is used to change the dot diameter.

FIG. 3 is a view of the knife 5 disposed on the P plane of FIG. 1, viewed from the optical axis direction of the collimating lens 6. 20 is an edge portion of the knife 5, and 21 is a beam. In the state shown in FIG. 3(a) when frequency f is applied, the beam is completely blocked by the edge portion 20 of the knife. Third
In Figure (b), when a frequency f is applied, only half of the beam passes through the edge portion 20. FIG. 3(C) shows the case when frequency f3 is applied, and the beam completely passes through without being blocked by the edge portion 20. The maximum frequency difference Δf, , = f, -fl, the beam diameter of the beam condensed by the condenser lens 3 at the Naifetsu plane P is Wp, and the distance between the diffraction point of the ultrasonic optical deflection element 4 and the Naifetsu plane P is d, and Δθr□yo is the difference in output angle between FIG. 3(a) and (C), then dΔθr11. , :Wp −■, and from the above relationship, d.

Δf, 3. By setting Wp, all the states shown in FIG. 3(a) to FIG. 3(C) can be created.

In the optical system shown in Figure 1, the knife plane P is 6.7
．． 9 is imaged on the scanning plane 10 (in a conjugate relationship of imaging), the state shown in FIG. 3 is projected onto the scanning plane 10 with a different magnification.

FIGS. 4(a) to 4(g) show the state of the beam at the scanning plane lO. (a) when the beam is slightly emitted from the naifetsuji, (d) when the beam is halved, (g)
shows the state on the scanning plane 10 when the entire beam is emitted. In this way, the applied frequency of the diameter of the ultrasonic optical deflection element is set to 0.
By changing the conditions of the formula, the beam diameter on the scanning plane can be changed continuously, so it is possible to realize variable dot diameter recording.

Also, as shown in Figure 4, the speed at which the beam diameter is changed is
It is determined by the access time ta of the ultrasonic light deflection element 4, where D: is given by the beam diameter of the light in the ultrasonic light deflection element 4, so as the ultrasonic medium 4-1, P b
When using M o Oa (lead molybdate), v
a=3.66xlO” m/sec, and D=150
If μnt, then t a is 441 ns according to the formula 0, and high-speed variation of the dot diameter can be easily realized. Furthermore, since the speed is high, it is possible to change the dot diameter for each pixel.

(Another Example) Although Fig. 4 shows a method of varying the recording dot diameter by changing the beam diameter in the sub-scanning direction, Fig. 6(a) and (b)
2 is a diagram showing a method of making the dot diameter variable not only in the sub-scanning direction but also in the main scanning direction. In this case, the shape of the scanning beam on the scanning plane lO is made into an oval (ellipse, rectangle, etc.) that is short in the main scanning direction and long in the sub-scanning direction, as shown in FIG. 5, and in FIG. The control circuit 14 sends a drive pulse signal 17 in the main scanning direction to the semiconductor laser drive circuit 13 in accordance with the image signal 15.
to pulse width modulate the semiconductor laser l (see Figure 6 (
Waveform b) At the same time, the length of the dot diameter in the sub-scanning direction is also changed by the ultrasonic light deflection element 4. The state of the recorded dots at this time is shown in FIG. 6(a). By this method, the two-dimensional change in the diameter of the recorded dots can be made larger than in the first embodiment described above, and more gradations can be achieved. This makes it possible to record 8-ftones. In this method, the semiconductor laser 1 is caused to oscillate in a CW manner, and the optical deflection time of the ultrasonic optical deflection element 4 (the time during which it is deflected at a certain frequency) is made variable, thereby achieving a somewhat similar effect. It is also possible to issue

Furthermore, it is also possible to combine the first embodiment with multilevel modulation (multilevel power variation at!l) of a semiconductor laser. In addition, a multi-level modulation method combining multi-level modulation with the second embodiment is also available.
So-called recording is also possible.

[Effects of the Invention] As described above, according to the variable dot diameter recording device B according to claim 1, the dot diameter is changed by blocking part or all of the beam by the light blocking means, and Since this is performed by minutely deflecting the beam using an ultrasonic optical deflection element, it is possible to provide a variable dot diameter recording device with a fast response speed and a large change in beam dot diameter.

Further, according to the variable dot diameter recording device according to claim 2,
Laser pulse width modulation or light intensity modulation and Claim 1
By using the methods described in combination, the variable range of the dot diameter can be further expanded and effective multi-tone recording becomes possible.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the variable dot diameter recording device of the present invention, and FIG. 2 is a plan view of only the optical system shown in FIG. 1.
Figure 3 is a diagram showing the light shielding relationship between the beam and the knife, Figures 4 (a) and (b) are diagrams each showing the state of the beam on the scanning surface of the photoreceptor, Figures 5 and 6 fa),
(b) is a diagram for explaining a second embodiment of the variable dot diameter recording device according to the present invention. 1--Beam generating means 4--Ultrasonic light deflection element, 5--Light blocking means (naifetsu) 8--Mirror surface of rotating polygon mirror 9--Anamorphic fθ lens 10... Image forming means (photoreceptor). (1 other person) Black 4 ChiZ Oral procedure amendment (method) % formula % 2, Name of the invention Variable dot diameter recording device 3, Relationship with the person making the amendment Patent applicant name (674) Co., Ltd. 4, Agent

Claims (1)

[Scope of Claims] 1. Consisting of a beam generating means, an ultrasonic light deflection element, and a light blocking means, the beam is deflected by the ultrasonic light deflection element, and the light beam is deflected according to the deflection angle. A dot diameter variable recording device characterized in that the dot diameter formed by the beam is changed by blocking part or all of the beam using a blocking means. 2. The variable dot diameter recording device according to claim 1, comprising an optical deflector for scanning a beam on an image forming means and a scanning optical system therefor, the light blocking means and the image forming means A dot diameter variable recording device characterized in that the scanned surface is in a conjugate relationship of image formation with respect to the sub-scanning direction.