JPS5823606B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an image recording system in which a light beam subjected to intensity modulation is incident on a mirror rotating at a constant speed, and desired characters, figures, etc. are recorded on a sensitive material placed on an image forming surface. This is done in order to provide a forming device that can accurately modulate the intensity of a light beam.

In the fields of facsimiles and various optical printers, a beam of light with intensity modulation is incident on a mirror rotating or reciprocating at a constant speed to scan an image forming plane and obtain various characters, figures, etc. It is diverse.

However, in such a device, if the image forming surface is a flat surface, there is no proportional relationship between the rotation angle of the mirror and the imaging position of the light beam, so if the intensity modulation is applied to the light beam at fixed time intervals, the same image as the original image will be obtained. There will be times when you will not be able to do so.

That is, in FIG. 1, the rotation center of the rotating mirror M is set to 0,
Image formation [If the center of iH is A10A=r, and the angle rotated from the position where mirror M directs the light flux Q toward point A is α,
At that time, the imaging position B of the light beam is AB= r tan 2α ・・・・・・・・・・・・
... becomes ■.

However, most of the text and graphic signals given to such devices are those that are separated into black and white dots divided at equal intervals, and the timing of applying intensity modulation to the light flux is determined by adjusting the timing of the intensity modulation of the light beam to a certain angle of the mirror. If α is small, there will not be much error if α is small, but as α becomes larger, the interval on the image forming surface H becomes larger, resulting in distortion of characters and figures.

In view of these points, the present invention aims to improve image formation IiH by intensity modulation of a light beam reflected by a mirror that rotates or reciprocates at a constant speed.
This was done in order to provide a device for obtaining the same image as the original by giving a timing signal such as that performed at equally spaced locations on the top. When reflecting the image forming light beam with a mirror and scanning the image forming plane, the rotation center of the mirror is set to O, the foot lowered from O to the image forming plane is A, 0A=r, and the light beam is reflected from point A. Points with an interval of a on both sides of the scanning direction are an(n=1.2.3...
), in an image forming apparatus in which the mirror applies intensity modulation to the image forming light flux each time the mirror rotates at an angle to both sides from a position where the light flux is directed to point A, the mirror directs the light flux to point A. When the mirror is in a position to face a point, a slit plate with slits formed at each given angle on both sides starting from an appropriate radial position centered on 0 was installed so that the slits could be detected as the mirror rotated. The image forming apparatus is characterized by comprising a photoelectric conversion element and a mechanism for intensity modulating the image forming light flux in synchronization with the output of the photoelectric conversion element.

First, the present invention will be explained in detail.

That is, here, as shown in FIG. 2, for example, a distance a plotted at a constant interval a from a point A on the image forming surface H
Since it is sufficient that intensity modulation is performed when the light beam reaches n=(n=1.2.3...), the angle of the mirror at that time is determined as follows.

Furthermore, when the mirror M is rotating at a constant angular velocity ω (ω=dα/d t ), the speed of the light spot on the image forming surface H is dan/dt=d/dt(rtan2a)=r・ω・s
Since it is given by ec 2α .

Figure 3 shows a general device constructed in accordance with the above-mentioned concept, which consists of a slit plate with equally spaced slits at positions equivalent to the image forming surface H in Figure 2. A part of the luminous flux reflected by the rotating mirror is guided thereto, and it is detected by a photoelectric conversion element to obtain the intensity modulation timing of the luminous flux.

In the figure, 30 is a light source such as a laser, 31 is a diffraction grating for separating the light flux from the light source 30 into 0th-order light and 1st-order light, 32 is a light modulation element using a KDP crystal, etc., and 33 is a diffraction grating 31
34 is a mirror that rotates or reciprocates at a constant speed, 35 is a lens, and 36 guides the primary light reflected by the rotating mirror 34 upward. Reflector, 37 is a slit plate with equally spaced slits, 3
Reference numeral 8 denotes an image forming surface, on which a photosensitive material or the like is placed.

39 is a photoelectric conversion element that detects the primary light that has passed through the slit plate 37.

Light emitted from a light source 30 such as a laser passes through a diffraction grating 31
The 0th order light is divided into the 0th order light and the 1st order light by the light modulation element 32.
is sent to the rotating mirror 34 through the.

The light is reflected by the rotating mirror 34, passes through the lens 35, and forms an image on the photosensitive material or the like on the image forming plane 38 by drawing a scanning line as shown by the arrow 40 as the rotating mirror 34 rotates. I'm going to go.

At the same time, the first-order light from the diffraction grating 31 passes through the optical path shown by the dotted line, is reflected by the mirror 33, is reflected by the rotating mirror 34 in exactly the same way as the zero-order light, passes through the lens 35, and is reflected by the reflecting mirror 36.
guided by.

In this example, it is directed upward by a reflector 36,
The slits of the slit plate 37 are irradiated.

Then, the photoelectric conversion element 39 detects the light, and an optical modulation timing pulse is created by an amplifier or the like (not shown), which is sent to the optical modulator 32 and zeroed at that timing.
The next light is modulated.

In this case, in order to direct the light flux that has passed through the slit plate 37 toward the photoelectric conversion element 39, a Fresnel lens, optical fiber, condensing hologram, rectangular image sensor, or the like is used.

According to the above-mentioned device, there is a slit plate 37 containing equally spaced slits at positions corresponding to the scanning position of the light, and a timing pulse corresponding to the scanning speed of the light is obtained from the slit plate 37.
Since the image signal is generated by this pulse, a reproduced image without distortion can be obtained.

However, such a device requires a diffraction grating 31 for obtaining O-order light and first-order light, reflecting mirrors 33 and 36, and an image forming surface 3.
A slit plate 37 having a dimension corresponding to the width of 8 is essential.

As a result, the optical path length becomes long, making it impossible to avoid increasing the size and complexity of the device.

The present invention is based on these points, and will be explained below with reference to the embodiments shown in the drawings.

FIGS. 4 and 5 show an embodiment of the present invention, in which a slit plate 43 that rotates together with a rotating mirror 41 and has slits 42 formed at intervals to be described later is attached integrally or coaxially with the rotating mirror 41. , this slit 42 is connected to the light emitting element 44 and the light receiving element 4.
5 is detected.

FIG. 5 is a diagram showing the slit plate 42 in detail, and the slits 42 are formed in the vertical direction of the figure starting from the slit 46 at each angle calculated by the formula 0 above, and the light emitting element 44 and the light receiving element 45 are It is installed on this starting point 46.

Note that this starting point 46 is not limited to the position shown in the figure as long as the above-mentioned conditions are met, and the slit plate 43 and the photoelectric conversion elements 44 and 45 are also fixed, and the slit plate is fixed, and the position of the photoelectric conversion element is (You can also rotate it together with the mirror).

With this configuration, the rotating mirror 41 rotates and a signal from the slit 42 is obtained for each angle at which the light beam is directed to each point an at the interval a on the image forming surface H in FIG. If the optical modulation timing signal of the optical modulator 32 in FIG.
, the slit plate 37, etc. are unnecessary, and the device can be made smaller and simpler.

It should be noted that since the optical modulation signal obtained by this embodiment is based solely on optical slit detection, there is a limit to the subdivision, which may cause problems in terms of accuracy.

Therefore, by inserting an interpolation pulse between the detection signals of the slits, it is possible to obtain even finer optical modulation pulses.

An example of a circuit for this purpose is shown in FIG. 6, and a time chart thereof is shown in FIG.

In the figure, 61 is the photoelectric conversion element shown by 39 in FIG. 3 and 45 in FIG. A circuit that receives a signal and generates a check pulse, 64
65 is a delay circuit, 65 is a digital-analog converter, 66 is a voltage-frequency converter that generates a pulse with a frequency proportional to the input voltage, and 67 is a digitizer that sets the number of interpolation pulses.
6B is a subtraction counter that subtracts the contents every time there is an input pulse, 69 is an adder, 70 is a register that stores the addition result of adder 69, and 71 is an output terminal.

Assuming that the voltage-frequency converter 66 is now generating pulses at an appropriate frequency, and the photoelectric conversion element 61 detects the slit as described above, an output as shown at 61 in FIG. 7 will be obtained. The shaping circuit 62 shapes this into a pulse as shown in FIG. 762.

Then, the check pulse generator 63 performs an AND operation on the pulse from the shaping circuit 62 and the pulse from the voltage-frequency converter 66, and generates the first signal after the pulse from the shaping circuit 62 rises, as shown at time t in FIG. Only one pulse from the input voltage-frequency converter 66 is sent to the delay circuit 64 as shown in FIG. 763.

Then, the delay circuit 64 delays this for an appropriate time as shown in FIG. 7, and then sends it to the subtraction counter 68 and register 70.

Among these pulses, the pulse sent to the subtraction counter 68 functions as a load pulse for setting the numerical value placed in the digitizer 67 into the subtraction counter 68.

Therefore, the contents of the subtraction counter 68 are subtracted from the set value every time a pulse from the voltage-frequency converter 66 is inputted.

The subtraction progresses in this way, and when the content of the subtraction counter 68 reaches a certain appropriate value, the next check pulse is output as shown at time t2 in FIG.
As mentioned above, the value of the register 67 is entered into the subtraction counter 68, but before that, the content of the subtraction counter 68 is entered into the adder 69 by the same check pulse.
It is added to the contents of register 70 and stored in register 70.

That is, for example, if 11 is now set in the register 67, 1 is initially stored in the register, and time t1 is set as shown in FIG.
If a total of 10 pulses are input to the subtraction counter 68 between 2 is registered in register 70
is memorized.

This value is then sent to a digital-to-analog converter 65, where it is converted to an analog voltage and sent to a voltage-to-frequency converter 66, where the frequency is increased since in this case the value in register 70 is positive.

Conversely, when the value in register 70 is negative, the frequency is decreased.

In this way, the pulses shown in FIG. 7 66 of the voltage-frequency converter 66 are output from the output terminal 71, and the number is set in the digitizer 67 between the detection pulses of the slits at irregular intervals as shown in FIG. 5 42. This means that the pulses are inserted.

In the above embodiments, we have explained the case where the rotating mirror is a single plane mirror, but this is not limited to only a plane mirror, and a device that can obtain exactly the same effect as a rotating polyhedral mirror can also be constructed. .

However, in this case, even in the apparatus shown in FIGS. 4 and 5, when the light beam reflected by the rotating mirror 41 is once incident on the lens and focused on the image forming surface, the plane mirror is simply replaced with the rotating polyhedron. A mirror may be used, and a slit 42 or photoelectric conversion elements 44 and 45 may be provided depending on each mirror surface, but correction is required if the reflected light beam is sent as is to the image forming surface.

In other words, in Fig. 8, the center of the rotating polygon mirror is set to 0.0.
Let P be the foot of the perpendicular line drawn down to one of the mirror surfaces, A be the center of the image forming surface H, 0P=R, PA=L, and assume that when the incident light beam Q goes toward point P, it will be reflected at point A. Then, when the polyhedral mirror rotates by an angle θ to the position indicated by the dotted line in the figure, the reflection point of the light beam becomes S, which becomes .

Therefore, AB becomes.

Therefore, from this equation 0, the rotation angle θ when directing the light beam to the point an plotted on the image forming surface H at intervals of a as shown in FIG. 2 is calculated, and the slit plate shown in FIG. All you have to do is create it.

Also, if we calculate the speed of the light spot on the image forming surface H from the formula 0 in the same way as the formula 0, we get: Therefore, if we apply optical modulation with a pulse with a frequency proportional to the formula 0, we can get exactly the same effect as described above. can get.

As described above, according to the present invention, the modulation timing of the light beam reflected by the rotating mirror and projected onto the flat image forming surface becomes shorter as it moves away from the center of the image forming surface, thereby eliminating distortion. Get accurate images.

Further, the device for this purpose can be relatively small and simple, and the effects obtained can be very large.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the relationship between the position where the light beam reflected by the rotating mirror reaches the flat image forming surface and the rotation angle of the mirror. FIG. 3 is an explanatory diagram of the conventional example; FIGS. 4 and 5 are detailed explanatory diagrams of the present invention; FIG. An example of a circuit for generating interpolation pulses for further subdividing the optical modulation timing pulses obtained by the embodiments shown in FIGS. 3 and 4, FIG. 7 is a time chart thereof, and FIG. FIG. 3 is an explanatory diagram in the case of implementation using a rotating polyhedral mirror. 30... Laser first class light source, 31...
・Diffraction grating, 32... Light modulator, 33...
...Reflector, 34...Rotating mirror, 35...
・Lens, 36...Reflector, 37...
Slit plate, 38... Image forming surface, 39...
...Photoelectric conversion element, 40...Scanning direction of light flux,
41... Rotating mirror, 42--... Slit, 43
...Slit plate, 44...Light emitting element,
45... Light receiving element.

Claims (1)

[Scope of Claims] 1. When scanning an image forming plane by reflecting an image forming light beam with a mirror rotating or reciprocating at a constant speed, a foot that lowers the center of rotation of the mirror from 010 to the image forming plane A,
When 0A=r and a point with an interval of a on both sides of the scanning direction of the light beam from point A is an (n=1, 2, 3...), the mirror directs the light beam toward point A. In an image forming apparatus that applies intensity modulation to the image forming light beam each time the mirror rotates at an angle to both sides from the position, when the mirror is in a position to direct the light beam toward point A, an appropriate intensity modulation centering on 0 is provided. A slit plate with slits formed at each angle given on both sides with a radial position as a starting point, a photoelectric conversion element installed to detect the slit as the mirror rotates, and a photoelectric conversion element installed to detect the slit as the mirror rotates. An image forming apparatus comprising a mechanism for intensity modulating an image forming light beam.