JPS5878117A - Multibeam recording device - Google Patents

Abstract

PURPOSE:To obtain a multi-beam recording device of samll size, high speed and high resolution, by inserting an optical path transducer consisting of 2 lenses opposed at a distance satisfying a prescribed condition, between the first lens of a laser array and a scanner. CONSTITUTION:Light beams from each light emitting element 1A-1C of a laser array 1 are emitted in the parallel direction with the optical axis, and form an image at a focal position 8 of the first lens 2. Its light becomes a parallel beam by a front lens 9 of an optical path transducer 11, forms an image on a galvano- mirror 3 by a rear lens 10, and is deflected. Its polarized beam forms an image as a very small spot on a recording member by the second lens 4, and executes scanning. By inclining the laser array 1 with respect to the optical axis of an optical system, a necessary scanning pitch can be obtained. In this way, a multibeam recording device of small size, high speed and high resolution is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for scanning and recording multiple light beams.

Conventional recording apparatuses scan a single light beam using a scanning device such as a polygon mirror to record on a recording member. Therefore, when recording at high speed, the data modulation frequency is high and the scanning device also needs to operate at high speed. In order to eliminate such drawbacks, a method is known in which light beams from a plurality of light sources (hereinafter referred to as multi-beams) are simultaneously scanned and recorded. - Figure 1 shows an example of a multi-beam scanning device, in which 1 is a laser array, 2 is a lens, 3 is a galvanometer mirror, 14 is a second lens, and 5 is a recording member. The light beam from the laser array 1 is turned into a parallel light beam by the second lens 4, reflected by the galvanometer mirror 3, and focused onto the recording member by the second lens 4. By deflecting the galvanometer mirror 3, the light beam scans and records a plurality of minute spots on the recording member.

When scanning the recording member with a plurality of light beams in this way, the pitch H of the spots of each beam on the recording member is given by: where m is the optical magnification of the recording device. Ho is the light emitting element pinch of the laser array, and f, , f2 are the focal lengths of the first lens and the second lens, respectively. The optical magnification m is often uniquely determined by the specifications of the recording device.

When the spot diameter a of the light beam is determined from the resolution of the recording device, the second
The diameter of the light beam incident on the lens is obtained.

λ is the optical wavelength of the incident light beam and is 1.

On the other hand, if the light beams emitted from each light emitting element of the laser array at a radiation angle θ are made into parallel light beams by a first lens, the following equation can be easily obtained.

D = 2f, tan θ/2 (31) Therefore, the optical magnification In is determined from the above equation, and once the diameter of the light spot on the recording member is determined, the optical magnification of the recording device is determined by how much light is incident on the first lens. It remains to be determined.

For example, each light emitting element has a circular radiation angle of 2 at a wavelength of 0.8μ.
Efficiency of the laser array with 0° by the first lens (
In a device that uses a first lens with an aperture angle of 10' to form a parallel light beam for transmission, converges the light with a second lens, and scans the recording member with multiple light beams with a spot diameter of 100μ, the optical magnification is variable. It will be about.

Therefore, in order to obtain scanning lines with a pitch of 100 microns on a recording member by multi-beam scanning of the laser array, the pitch of each light emitting element of the laser array must be several microns from the relationship of equation (1). However, it is very difficult to make the pinch of each light emitting element of the laser array as narrow as this. On the other hand, 10
Even if the laser array is arranged with a light emitting element pitch of 0μ, the spot of each imaged light beam will have a required scanning line pitch (for example, 100μ) in the direction perpendicular to the scanning direction.
) can be imaged by tilting the laser array.

FIG. 2 illustrates the state of the spot 6 of each light emitting element of the laser array that is imaged on the recording member.

The required scanning line pitch A can be maintained as follows.

A = m Hocosα α is the inclination angle that the laser array makes with the direction perpendicular to the scanning direction 7. As mentioned above, the optical magnification is given by several tens of times, so if the light emitting element pitch of the laser array is arranged at 100μ, in a recording device that scans the scanning line pinch at 100μ, the tilt angle will be approximately 90'. As a result, the imaged light spot 6 is almost parallel to the scanning direction 7.

In a recording device that performs multi-beam scanning in this way, the optimum optical magnification is determined by determining the spot diameter on the recording member and the radiation angle of each light emitting element of the laser array, so the focal length of the first lens and second lens is determined by the ratio. can be decided according to. This is the same as in the case of a single lens, by converting the focal length of the entire lens group, even if the lens is composed of a plurality of lens groups (hereinafter referred to as cylindrical lens group).

Then, given the optical magnification, the laser array can be tilted to obtain a predetermined scan line pitch. If arranged in this way, one that satisfies the specifications of a multi-beam scanning recording device can be obtained.

However, in the recording device configured in this way, the laser array 1 is tilted so as to obtain a spot that spreads in the scanning direction on the recording member, so that each beam is directed to the mirror of the scanning device as shown in FIG. Since it is reflected at different positions on the surface, a scanning device with a large mirror is required. To explain this in detail, each light emitting element IA of the laser array 1.

Since IB and IC are made to form parallel waveguides on the same substrate, the respective light emitting elements IA, IB,
The ICs emit light beams in the same direction. Also, Runs 2
The light beams of the laser array 1 placed at the front focal position of the laser array 1 are turned into parallel light beams by the first lens, and the direction of the parallel light beams varies depending on the position of each light emitting element of the laser array 1. Therefore, each light emitting element IA, IB.

If the laser array 1 is arranged so that the light beam of the IC is emitted in a direction parallel to the optical axis of the second lun, the second lun
Each of the light beams bent by
3 would require a large mirror to receive each light beam. On the other hand, if the galvano mirror 3 is placed at the back focal position, a small mirror can be used, which has the advantage of allowing high-speed operation. However, as mentioned above, the optical magnification of the recording device is several tens of times, and the focal length of the second lens must be approximately equal to the scanning width to obtain a good image over the entire scanning width. Generally, the focal length of the second lens is approximately 10 to 30 mm from equation (1), so it is difficult to place the galvano mirror at the back focal position of the second lens due to mechanical constraints. There are many cases.

In order to solve this problem, it is necessary to increase the focal length of the first lun; however, by doing this, the diameter of the emitted light beam from the first lun becomes thicker, and the spot on the recording member becomes smaller due to the phenomenon of diffraction. Excessive scanning causes a raster-like striped pattern to appear, degrading the image quality.Therefore, it is better to increase the focal length of the first lens (and at the same time reduce the light emission angle of each light emitting element in the laser array. Since it is very difficult to reduce the light emission angle of the light emission angle, the light emission angle must be limited by slits, etc. This obviously leads to a deterioration of power efficiency. In a recording device that uses a laser array, changing the optical magnification results in a significant deterioration of the performance of the device.

In order to eliminate these drawbacks, the present invention disposes another lens between the first lens and the scanning device, and changes the optical magnification of the device by appropriately selecting the relationship between the focal lengths of the lens and the second lens. (It is a device that can be scanned with a small scanning device, and the first purpose is to improve the efficiency of the device.
The second objective is to obtain a small and inexpensive device, and the third objective is to provide a high-speed, high-resolution device.

FIGS. 4(5) and 4(B) show a first embodiment of the present invention, in which 9 is a front lens, 10 is a rear lens, and 11 is an optical path converter of the present invention. It consists of a laser array l placed at the front focal position of the second lunion 2 and an optical path changer according to the present invention placed between the second lunion 2 and the galvanometer mirror 3. The optical path converter is composed of two lenses, a front lens 9 and a rear lens 10, which are arranged on the same optical axis so that the focal positions of the front lens 9 and the rear lens 10 are the same. Therefore, the parallel light beam incident on the front lens 9 is condensed at the focal point 12 and reconverted into a parallel light beam by the rear lens 10.

In FIG. 4(A), the lens 2 and the optical path converter 11 are arranged on the same optical axis so that the focal positions of the lens 2 and the front lens 9 are the same. In FIG. 4, the second lens 2 and the optical path converter 11 are arranged at narrower intervals than in FIG. 4(A).

The optical magnification m of the lens system arranged in this way is given by the number of lenses, the front lens, the rear lens, and the second lens.

As mentioned above, since the optical magnification m and the second lens f2 are determined by the performance of the recording apparatus, the focal length f of the first lens group. is chosen so that .

Further, a lens with a large focal length fB is used as the rear lens 10 of the ζ optical path converter 11 so that the plurality of emitted light beams from the optical path converter 11 are focused on the galvanometer mirror 3. To explain these operations, each light emitting element IA of the laser array H
, IB, and IC are emitted in a direction parallel to the optical axis, and each becomes a parallel light beam by the second lens 2. Each parallel beam passes through the back focal point 8 of the second lens and is incident on the front lens 9 of the optical path changer 11 of the invention.

The front lens 9 forms an image at the focal position. Since the rear lens 10 of the optical path converter 11 uses a lens with a large focal length, the focal length of the first lens group is f.

In order to keep the value constant, the focal length of the front lens 9 of the optical path converter also needs to be large. Therefore, each light emitting element IA, I of the laser array 1 is imaged by the front lens 9.
For the images of B and IC, a light emitting element image with a small radiation angle is created at the focal position under equal constraints. Therefore, the optical path converter 11
If the parallel light beams are formed by the rear lens 10, the position where each party beam intersects with the optical axis can be freely selected depending on the focal length of the rear lens 10.

The fourth position is for explaining the main points of the present invention in an easy-to-understand manner. It can be seen that since the facing lenses are arranged on the same optical axis so as to have a common focal point position, a light emitting element image 12 is obtained which is emitted in a direction parallel to the optical axis and has a small radiation angle.

Furthermore, the light beam emitted from the rear lens 10 is transmitted to the rear lens 1.
It gathers at the back focal position of 0. Since the rear lens lO is a lens with a long focal length, the rear lens 10 and the scanning device can be placed apart.

In FIG. 4(B), since the optical path changer 11 is placed close to the second lens 2, each light beam travels in the direction of expansion within the optical path changer ll, so if the parallel light beam is tossed by the rear lens 10, , passes on the optical axis behind the rear focal point position of the rear lens 10, which is more effective.

The present invention thus eliminates mechanical constraints on the arrangement of the scanning device, and can provide a recording device using a scanning device that can operate at high speed with a small mirror.

Furthermore, it will be explained that the present invention can provide a more effective device by means of a second embodiment.

FIG. 5 shows a second embodiment of the present invention, in which reference numeral 13 denotes a reflecting mirror;
14 is a beam splitter. The second embodiment shows a 9-beam simultaneous scanning recording apparatus in which three laser arrays each having three light emitting elements are optically coupled.

The light beams emitted from each laser array 1-1.1-2.1-3 are turned into parallel light beams by the respective lenses 2 and optical path converters 11, respectively.

The respective parallel light beams are combined by a reflecting mirror 13 and a beam splitter 14, and then sent to a galvanometer mirror 3.
The configuration is such that the second lens 4 records the images.

The spots of the six light-emitting elements 1 of the laser array 1 on the recording member can be obtained by tilting the laser array 1 to obtain the required scanning line pitch.

On the other hand, in order to obtain the scanning line pitch on the recording member between each laser array, a reflection mirror 13 and a beam splitter 14 are used.
By adjusting , an imaging spot 15 as shown in FIG. 6 can be obtained. 16 indicates the scanning direction.

In the configuration shown in FIG. 5, in order to combine the light beams corresponding to the respective laser arrays, it is necessary to arrange a beam splitter 14 and a reflecting mirror 13, which increases the distance between the galvanometer mirror 3 and the lens group. Therefore, depending on the distance between the galvanometer mirror 3 and the optical path changer 11, the optical path changer 11
By selecting the focal lengths of the front lens 9 and the rear lens 10, light can be focused on the mirror of the galvanometer mirror 3.

Since only a small mirror is required in this way, the scanning device can also operate at high speed.

In the non-example, a galvano mirror was used as the scanning device, but
The same can be said for polygon mirrors.

Further, a no-f mirror may be used as a beam splitter. Furthermore, if each laser array is provided with a different wavelength, it is possible to create a configuration that can efficiently transmit power using dichroic ink mirrors, interference filters, or the like. Since the present invention includes an optical path changer,
It has the advantage that the device can be configured freely, and can be used in the optical system of a recording device using a laser array.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional multi-beam recording device, Fig. 2 is an explanatory diagram of multi-beam scanning, Fig. 3 is an explanatory diagram of a conventional multi-beam scanning device, and Fig. 4 is a multi-beam recording according to the present invention. FIG. 5 is a block diagram of the apparatus, FIG. 5 is a block diagram of a second embodiment of the present invention, and FIG. 6 is a diagram showing scanning in the second embodiment. 1 is a laser array, 2 is a first lens, 3 is a galvanometer mirror 14 is a second lens, 5 is a recording member, 11 is an optical path changer, 13 is a reflection mirror, and 14 is a beam splitter. Patent Applicant Computer Basic Technology Research Association Patent Application Agent Megumi Yamamoto - Mo/[21 Mo2 [21 Figure 3, Figure 5]

Claims (2)

[Claims] (1) A laser array (1) having a plurality of light emitting elements arranged at predetermined intervals, a first lens (2) that converts the light beam from each light emitting element into a parallel light beam, and deflects the parallel light beam. a scanning device (3) that condenses a light beam from the scanning device;
4) In the multi-beam recording device that records on an optical recording member with the light spot focused in step 4), the first lens (2)
and the scanning device (4).
In both cases, an optical path changer Q0 having one lens is provided, and the relationship between the focal length of the first lens and the focal length of the optical path changer is selected such that the optical magnification of the multi-beam recording device remains unchanged. Multi-beam recording device. (2) Multi-beam recording according to claim 1, in which the optical path changer (1υ has two lenses (9 & IO), and the two lenses face each other at a distance equal to the sum of the focal lengths of each lens) Device.