JPH0375716A - Laser recorder - Google Patents

Abstract

PURPOSE:To allow an effective multivalued gradation recording by providing a variable aperture element which has plural aperture elements and variably controls the aperture quantity to an incident laser beam. CONSTITUTION:A substrate 16 formed with an aperture 15 in a light transmission region 7 part is prepd. and the aperture element 1 is packaged and fixed by an adhesive agent onto the position the aperture 15. ICs 17 for driving are packaged and fixed on both sides. The ICs 17 and respective electrodes 10 are connected by bonding wires 18. Namely, the electrode 10 sides are bonded to the bonding wires in groove 4, 5 parts and the IC 17 sides are bonded to the bonding pad parts provided on the substrate 16. A polarizer 11 and an analyzer 12 are disposed before and behind such variable aperture element 14, by which an incident laser beam can be taken out as an exit laser beam in the state of controlling the beam to an arbitrary dot diameter. The multivalued gradation recording is thus effectively executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laser recording apparatus such as a laser printer, a digital copying machine, etc., in which the dot diameter can be varied.

Conventional technology In recent years, laser recording devices capable of high-quality printing have
In order to further improve performance, it has been proposed to enable multilevel gradation recording by varying the dot diameter for each pixel.

For example, Japanese Unexamined Patent Publication No. 113018/1983 discloses an apparatus that includes a variable aperture for changing the dot size of the laser beam and a control means for controlling the amount of the aperture.

Furthermore, according to Japanese Patent Application Laid-Open No. 63-296069, the diameter of the light beam dot is changed by controlling the light intensity of the semiconductor laser, and when the pixel information of two adjacent dots are both non-irradiation information, the dot The diameter is enlarged to prevent the wire from breaking.

However, according to the former method described in the publication, the variable aperture consists of an iris aperture or a liquid crystal aperture, which has a slow response speed and is unsuitable for high-speed laser recording devices.

Also, according to the latter method described in the publication, the beam dot diameter is changed by changing the light intensity of the semiconductor laser.
The amount of change in dot diameter is small, and the effect is small.

Means for Solving the Problems A laser light source, a variable aperture element having a plurality of aperture elements in which the aperture amount for an incident laser beam is variably controlled, and an optical deflector for deflecting and scanning an output laser beam from the variable aperture element. and an imaging optical element that images the deflected laser beam onto the scanned medium.

The diameter of each pixel of the dot imaged onto the scanned medium is varied according to the aperture amount of the variable aperture element. Therefore, the aperture amount can be varied by controlling the opening and closing of the aperture element in the variable aperture element, and the dot diameter can be varied with a fast response speed. Further, the amount of change in aperture amount can be increased by using an aperture element, and the dot diameter can be greatly varied, making it possible to perform effective multilevel gradation recording.

Example An embodiment of the present invention will be described based on the drawings.

This embodiment is characterized in that a variable aperture element is used to vary the dot diameter, and FIG. 2 shows the structure of the aperture element l, which is the main component of this variable aperture element. First, an electro-optic crystal 2 made of PLZT with a thickness of 400 μm and having both upper and lower surfaces optically polished is prepared, and a light transmitting region 3 with a width of about 100 μm is left on the − surface, and grooves with a depth of about 200 μm are formed on both sides of the electro-optic crystal 2. 4 and 5 are formed using a dicing saw. The width of these grooves 4 and 5 is 1++u++ or more, but they may be formed over the entire surface of the electro-optic crystal 2, leaving the light transmitting region 3. In any case, the light transmitting region 3 will have a convex shape and have side walls 6.

Next, an electrode film (for example, NiCr:Au) 7 is formed on the grooves 4 and 5 including the side walls 6 by sputtering. After this, a groove of 250 μm in depth and 20 p in width is applied to the two faces of the electro-optic crystal including the electrode film 7 in the direction perpendicular to the grooves 4 and 5.
A plurality of m(7) grooves 8 are formed at a pitch of loop m.

As a result, as shown in FIG. 2(b), a plurality of (eight examples are shown here) rectangular aperture elements (light on/off A separate electrode IO is formed for each region) 9 and aperture element 9.

The operating principle of such an aperture element 1 will be explained. In principle, as shown in FIG. 3, a polarizer 11 and an analyzer 12 are used in combination on the laser beam entrance and exit sides.

Here, the polarizer 11 and the analyzer 12 are orthogonal to each other, and the direction of the electric field applied to the aperture element l is 4.
It is installed at an angle of 5°. Now, the intensity of the incident light is Ii
, the intensity of the emitted light is Io, and when considering within one aperture element 9, the following relationship holds true. However, the phase difference r is r'=-・t
-n, ・Rc-E" −・---------
−(2) denoted by λ. Here, λ: wavelength, t near aperture element 1
thickness, n: refractive index, E: electric field strength, and Rc: second-order electro-optical constant.

According to equation (1), Io is maximum when the phase difference r is mπ (m is an odd number) (that is, the aperture element 9 is in the open and on state), and the phase difference F is m'π (m' is an odd number). (even number), Io is at its minimum (that is, the aperture element 9 is closed and in the OFF state).

Therefore, by individually controlling voltage application to a plurality of aperture elements 9 via each electrode 10, any aperture element 9 can be opened/closed (on/off).
In other words, the aperture amount can be variably controlled.

In FIG. 3, a portion 13 shows an example of the light intensity distribution of the emitted light when the central four aperture elements 9 are opened and the remaining four aperture elements 9 are closed.

This allows the dot diameter to be varied within one pixel in the laser recording apparatus.

Here, in order to drive such an aperture element 1, a driving IC or the like is required, and the variable aperture element 14 is mounted as shown in FIG. First, a substrate (ceramic substrate) 16 in which an opening 15 is formed in the light transmitting region 7 (aperture element 9) is prepared, and the seven vertices elements 1 are mounted and fixed on the opening 15 using an adhesive. In addition, ICl for driving is installed on both sides.
7 is also fixedly mounted. These ICs 17 and each electrode 10 are connected by bonding wires 18. Specifically, the electrode 10 side is bonded to the grooves 4 and 5, and the ICI 7 side is bonded to the bonding pad portion provided on the substrate 16. By arranging the polarizer 11 and the analyzer 12 before and after the variable aperture element 14, the incident laser beam can be extracted as an output laser beam while controlling the dot diameter to be arbitrary.

A variable dot diameter laser printer is constructed as shown in FIG. First, a semiconductor laser 20 is provided as a laser light source that is modulated and driven according to pixel information. The variable aperture element 14 is disposed on the optical path of the laser beam emitted from the semiconductor laser 20, and between the two is a coupling lens 21 that converts the light emitted from the semiconductor laser 20 into parallel light, and a coupling lens 21 that polarizes the laser beam. λ/2 that makes the direction 456 with respect to the sub-scanning direction
A cylinder lens 23 is interposed to focus the laser beam onto the plate 22 and the variable aperture element 14. Here, the variable aperture element 14 is arranged such that a plurality of aperture elements 9 are lined up in the sub-scanning direction. On the output side of the variable aperture element 14, a polygon mirror 26 serving as a deflector is provided to deflect and scan the laser beam in the main scanning direction via a lens 24 for beam conversion and a cylinder lens 25. A toroidal fθ lens 28 is provided on the output side of the polygon mirror 26 as an imaging optical element that forms an image of the deflected laser beam onto the surface of a scanned medium (for example, a photoreceptor) 27.

Here, in this embodiment, the variable aperture element 14
and the surface of the scanned medium 27 are positioned so that they are in a conjugate relationship for image formation. That is, the surface of the variable aperture element 14 is imaged on the surface of the medium 27 to be scanned, and the aperture amount is accurately reproduced on the surface of the medium 27 to be scanned, so that the dot diameter in the sub-scanning direction can be varied. Become.

FIG. 5 shows an example of how the dot diameter is varied. That is, by driving and controlling the semiconductor laser 20 according to the pixel information and at the same time variably controlling the aperture amount (the state of the aperture element 9 to be opened) in the variable aperture element 14 according to the density of the pixel information, as shown in the figure. Multi-level gradation recording in which the dot diameter is varied in the sub-scanning direction becomes possible.

In this case, in addition to changing the dot diameter in the sub-scanning direction by the variable aperture element 14, if the semiconductor laser 20 is driven by pulse width modulation as shown in FIG. 6, the dot diameter can also be changed in the main scanning direction. This enables more advanced multilevel gradation recording.

In addition, in the driving method shown in FIG. 5 or FIG. 6, the semiconductor laser 20 may be driven by optical intensity modulation according to multilevel information. By combining such light intensity modulation, more sophisticated multilevel gradation recording becomes possible.

Note that the aperture element for the variable aperture element 14 is not limited to the one shown in FIG. 2, but may be one shown in FIG. 7 or FIG. 8, for example.

FIG. 7 shows an electro-optic crystal 32 made of PLZT having a thickness of 600 pm and having both sides optically polished, regarding the aperture element 31.
A light transmitting area 3, grooves 4, 5, 8, an electrode film 7, etc. are formed on both sides, and an aperture element 9 and an electrode 10 are formed on both sides (the back side has a dash r' in the code). ). In this case, the aperture elements 9 and the electrodes 10 are arranged alternately on the front and back so that they do not overlap. According to this, by using both sides, the arrangement interval of the aperture elements 9 on both the front and back sides becomes dense, and light loss is reduced compared to the case of arrangement on only one side.
High density is also possible.

Regarding the aperture element 33, FIG.
．． In this embodiment, the electrodes 35 are directly formed individually without forming the electrode film 7 (by etching, etc. after the electrode film 7 is formed), and the aperture element 36 is formed between the left and right electrodes 35. In this case as well, the aperture element 3
6 may be formed alternately on both sides.

Effects of the Invention As described above, the present invention uses a laser light source, a light deflector, an imaging optical element, and a variable aperture element that has a plurality of aperture elements and whose aperture amount for an incident laser beam is variably controlled. With this configuration, the dot diameter of each pixel that is imaged on the scanned medium can be varied according to the aperture amount of the variable aperture element. It is possible to change the dot diameter with a fast response speed, and it is also possible to increase the amount of change in the aperture amount using an aperture element, making it possible to greatly vary the dot diameter. Value gradation recording is possible.

9... Aperture element, 14... Variable aperture element, 20... Light source, 26... Deflector, 27...
...Scanned medium, 28...Imaging optical element

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1(a) is a schematic front view of the optical system of a laser printer, FIG. 2(b) is a schematic plan view thereof, and FIG. Fig. 3 is a schematic side view showing the operating principle, Fig. 4 (a) is a schematic front view showing the variable aperture element, Fig. 4 (b) is a schematic front view showing the variable aperture element, A schematic plan view thereof, FIG. 5 is an explanatory diagram showing an example of a variable dot diameter, FIG. 6 is an explanatory diagram showing a modification example of the variable dot diameter, and FIG. 7(a) is a schematic front view showing a modification example of the aperture element. 8(b) is a schematic plan view thereof, FIG. 8(a) is a schematic front view showing different modifications of the aperture element, and FIG. 8(b) is a schematic plan view thereof.

Claims (1)

[Claims] A laser light source, a variable aperture element that has a plurality of aperture elements and whose aperture amount for an incident laser beam is variably controlled, an optical deflector that deflects and scans an output laser beam from the variable aperture element, and a deflected laser. A laser recording device comprising: an imaging optical element that images a beam onto a scanned medium.