JPH06109986A - Optical writing element - Google Patents

Abstract

PURPOSE:To make image quality high, size small, cost low and yield high by providing an optical waveguide part, plural light absorbers, a light attenuating part having light absorber driving mechanisms and a signal processing circuit. CONSTITUTION:This optical writing element has a substrate 21, the optical waveguide part which is formed on this substrate 21 and consists of a core layer 22 for guiding luminous fluxes and clad layers 23, 24 enclosing this clad layer 22, plural (n) pieces of the light absorbers 251 to 25n and the light attenuating part consisting of the light absorber driving mechanisms 261 to 26n which mechanically hold the light absorbers 251 to 25n and apply a mechanical displacement respectively to the light absorbers 251 to 25n or apply an electrical effect, an magnetic effect or both effects thereof respectively to the light absorbers 251 to 25n from the outside. Further, the element has the signal processing circuit 27 which takes in plural bits of digital image signals indicating the light attenuation quantity set in the outside, stores the signals for a specified period of time and transmits the signals to the light absorber driving mechanisms 261 to 26n.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographic light-sensitive material for use in devices such as video printers, digital copying machines, facsimiles, laser printers, etc., for obtaining hard copies by image signals.
The present invention relates to an optical writing element that writes an image on an electrophotographic photoreceptor or the like.

[0002]

2. Description of the Related Art Conventionally, as an optical writing means for writing an image on a photographic photosensitive material, an electrophotographic photosensitive member or the like in a device such as a video printer, a digital copying machine, a facsimile, a laser printer, etc., a plurality of writing points respond to an image signal. LCD shutter that allows light from the light source to pass through,
There is an LED (light emitting diode) printer head, a writing system using a laser beam and a polygon mirror, and the like.

In the LED printer head, as shown in FIGS. 6 and 7, an image signal is input to the shift register 11 serially or in parallel for each scanning line, and the LED array 12 is driven by the output signal of the shift register 11. It
The LED array 12 is composed of a plurality of LEDs 121, 122, 123, ... For one scanning line arranged in the main scanning direction, and each LED is driven by an output signal of each stage of the shift register 11 to emit light. The LED array 12 is arranged in the width direction of the photoconductor drum 13, and each LED 121, 12 is arranged.
The light from 2, 123 ... Is imaged on the photoconductor drum 13 via the imaging lens 14.

The photosensitive drum 13 is driven to rotate by a motor and uniformly charged by a charger, and then the LED 12 is charged.
The image is written by being exposed to the light from 1, 122, 123, ..., And an electrostatic latent image is formed. In this case, the LED
The exposure of the photosensitive drum 13 by the array 12, that is, the writing of light is performed by the LEDs 121, 122, 123 ... 1
Each luminous dot D1, D2, D3 ...
One pixel is formed as a dot image formation pattern. When the scanning time of one scanning line is long, it is possible to divide all pixels into a plurality of groups and perform the scanning in time series for each group. Conversely, it is also possible to scan one scanning line at the same time.

In the writing system using laser light and a polygon mirror, as shown in FIG. 8, the laser light from the gas laser 15 is modulated by the image signal by the AD modulator 16, deflected by the polygon mirror 17 and then the fθ lens 1
The photoconductor drum 19 is irradiated with the light through the laser beam 8. The photoconductor drum 19 is rotated by a motor, uniformly charged by a charger, and then exposed by being irradiated with laser light from the fθ lens 18 while being repeatedly scanned in the main scanning direction by the polygon mirror 17. The image is written and an electrostatic latent image is formed. A semiconductor laser may be used instead of the gas laser 15 and the AD modulator 16, and the semiconductor laser may be driven by an image signal.

[0006]

In the optical writing means such as the liquid crystal shutter, the LED printer head, and the writing system using the laser beam and the polygon mirror, the light from the light source is adjusted in an analog manner, or the light source of the light source is adjusted. The amount of light emission is continuously controlled to change the amount of light exposure of the photosensitive member that is the target of optical writing.Currently, however, image signals can be stored and processed as digital signals in the image processing unit. It is the mainstream because it is advantageous in performing various processes in the image processing unit. Therefore, an extra device for converting a digital signal into an analog signal is required between the image processing section and the optical writing means. For this reason, the circuit configuration becomes complicated and the production cost rises, and the quality of the written image deteriorates due to an error in converting the digital signal into the analog signal, which causes an obstacle in downsizing and cost reduction. There are drawbacks.

Further, in the optical writing means using a large number of light sources such as an LED printer head, the light amount of each light source and the rate of change with respect to the input signal have to be the same, which requires a considerably high technique in production. However, this leads to an increase in production cost and a decrease in yield.

Further, in an optical writing means such as a liquid crystal shutter for adjusting the amount of transmitted light at a large number of writing points, it is necessary to make the individual transmittances of the respective writing points and the rate of change with respect to the input signal the same. A problem arises.

Further, in both of the optical writing means, a change in characteristics occurs in order to maintain the initial image quality in long-term use, because the light-emission amount decreases, the transmittance changes, and the like over time due to long-term use. Must be corrected by some means. However, since the characteristic change is different at each writing point, if it is attempted to correct it, a correction amount detecting means and a correcting means are required for each writing point, for example, image writing of A3 size, 600 dpi is performed. In this case, the number of writing points becomes a huge number of about 6000. Therefore, it is practically impossible to realize an LED printer head or a liquid crystal shutter that corrects a characteristic change.

Therefore, these optical writing means inevitably suffer from the drawback of deterioration of written image quality due to aging. The reason why these optical writing means are used is that these optical writing means have an advantage that they are small in size.

On the other hand, in a writing system or the like in which light from one light source is deflected by a deflection optical system such as a polygon mirror, since there is only one light source, it is easy to correct changes in the amount of emitted light. However, since the deflection optical system is large, there is a drawback in that it cannot be downsized.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical writing element which is capable of improving the above-mentioned drawbacks, improving the image quality, reducing the size, reducing the cost and improving the yield at the same time.

[0013]

In order to achieve the above object, the invention according to claim 1 has an optical waveguide having a core layer having an exposed region for guiding light and a cladding layer surrounding the core layer. A plurality of waveguides, a plurality of light absorbers arranged corresponding to the exposed regions of the core layer and sequentially absorbing a part of the light guided by the core layer by a light absorption amount that is two times different; By mechanically holding the light absorber of, and applying mechanical displacement or at least one of an electrical effect and a magnetic effect to the plurality of light absorbers according to a signal from the outside. A light attenuator having a plurality of light absorber driving mechanisms for selectively taking a state of absorbing a part of the light guided by the core layer and a state of not absorbing the light, Capture the signal that shows the optical attenuation, In which a signal processing circuit for transmitting a predetermined time period stored in the light-absorbing member driving mechanism No..

[0014]

The light is guided by the core layer, and the plurality of light absorber driving mechanisms give mechanical displacements to the plurality of light absorbers in response to signals from the outside, or electrical and magnetic effects. By providing at least one of the above, the plurality of light absorbers selectively take a state of absorbing a part of the light guided by the core layer and a state of not absorbing the light.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the present invention. The writing element of this embodiment includes a substrate 21, a core layer 22 formed on the substrate 21 for guiding a light flux, and a core layer 22.
An optical waveguide portion composed of cladding layers 23 and 24 surrounding the
The plurality (n) of the light absorbers 251 to 25n and the light absorbers 251 to 25n are mechanically held and mechanically displaced from the outside to the light absorbers 251 to 25n, or the light absorbers 251 to 25n. An optical attenuator composed of optical absorber driving mechanisms 261 to 26n for applying an electrical effect and / or a magnetic effect to 25n, and a multi-bit digital image signal indicating an externally set optical attenuation amount are taken in. , And a signal processing circuit 27 that stores this for a certain period of time and transmits it to the light absorber driving mechanisms 261 to 26n.

The optical waveguide portion has a region where the core layer 22 is exposed without the cladding layer 24, and the light attenuating portion is arranged in the exposed region of the core layer 22 so that the light absorbers 251 to 25n are provided in the core layer 22. They are placed in contact with or close to each other. The n light absorbers 251 to 25n have different light absorption amounts with respect to the light flux propagating through the core layer 22, and when the smallest light absorption amount among these light absorption amounts is 1, As the absorption amount increases, the light absorption amount is sequentially increased to the power of (n-1) times 2; that is, the light absorption amount is 1, 2, 4, 8 ...
In this way, a relationship that is twice different is established in sequence.

The operation of this embodiment will be described. In the light attenuator, the light absorber driving mechanisms 261 to 26n are used as the signal processing circuit 27.
N light absorbers 251 according to the digital image signals from
25n are driven to drive the light absorbers 251 to 25n by applying mechanical displacement or at least one of an electrical effect and a magnetic effect to the light absorbers 251 to 251n.
25n selectively absorbs a part of the light beam guided by the core layer 22 and a state of not absorbing the light beam. A certain amount of light flux emitted from an external light source enters the core layer 22 from the right end portion of FIG. 1, is guided by the core layer 22, and is attenuated by the light attenuating portion by the amount set by the signal processing circuit 27. And is ejected from the left end of the core layer 22. If a photosensitive member such as a photographic photosensitive material or an electrophotographic photosensitive member is placed in the immediate vicinity of the left end portion of the core layer 22, the photosensitive member can be exposed according to an image signal.

The operation of the light attenuator will be described in detail. Each of the n light absorbers 251 to 25n operates independently, and the core layers 22 are driven by the light absorber driving mechanisms 261 to 26n.
The light beam propagating through the core layer 22 is attenuated and the light beam propagating through the core layer 22 is not attenuated at all. One light absorber is driven by one light absorber driving mechanism so that the light attenuation amount is constant when the light flux is attenuated.

The n light absorbers 251 to 25n are the core layers 2
In the state of absorbing light from 2, the light fluxes propagating through the core layer 22 have different light attenuation amounts, and the light absorption amount between these light absorption amounts is 1 when the smallest light absorption amount is 1. As the amount of absorption increases, 2 (n-
1) Since the light absorption amount is multiplied,
The light absorber 25 having the smallest light absorption amount in the LSB of the digital image signal (luminance signal) output from the signal processing circuit 27.
1 and assign each other bit of the digital image signal to the MS
By assigning the light absorbers 252 to 25n whose light attenuation amount increases gradually as the position approaches B, the light amount of the light flux emitted from the core layer 22 becomes an inversion of the digital image signal and the negative type photosensitive member. You can write an image to. For the positive type photosensitive member, the digital image signal may be inverted in the signal processing circuit 27, which can be easily performed.

There are various types of light absorbers 251 to 25n and light absorber drive mechanisms 261 to 26n. For example, as the light absorbers 251 to 25n, silicon blocks supported by cantilevers formed by anisotropic etching of crystalline silicon are used, and the light absorber driving mechanisms 261 to 26n are used.
Is a voltage applied between the transparent electrode provided on the core layer 22 and the cantilever, and the light absorbers 251 to 251 to
When 25n is brought into close contact with the transparent electrode, a part of the light propagating in the core layer 22 is absorbed by the light absorbers 251 to 25n, and when the light absorption by the light absorbers 251 to 25n is stopped, the voltage is zero. Then, a mechanism for separating the light absorbers 251 to 25n by the restoring force of the cantilever is used.

The light absorbers 251 to 25n are the core layers 2
It is also possible to use a light absorber including an electro-optic crystal in contact with 2 and a light absorbing member that absorbs the light flux when the light flux is guided to the electro-optic crystal. Light absorber drive mechanism 2
61 to 26n are composed of a plurality of electrodes for applying an electric field to the electro-optic crystal and a switch for controlling the potentials of these electrodes, and the refractive index of the core layer 22 is nc, and the electric field of the electro-optic crystal is applied. Where n is the refractive index of the electro-optic crystal and nb is the refractive index of the electro-optic crystal when an electric field is not applied, na>
It is also possible to use a mechanism for changing the refractive index of the electro-optic crystal by controlling the potential of the electrode so that nc> nb.

The light absorbers 251 to 25n can be made of almost all metals, and when absorbing light in the near infrared to visible region, Si, Cr, Ge, Ta,
W is suitable.

In this embodiment, a plurality of bits of digital image signals are directly input to the signal processing circuit 27 to input the core layer 22.
Since it is possible to control the amount of light emitted from the device, there is a device that converts a digital signal to an analog signal, which is always necessary when configuring a device that outputs an image from a dedacil-processed image signal using an optical writing element. It is not necessary, and it is possible to achieve size reduction, cost reduction, and yield improvement by simplifying the device configuration. Further, since the delay time that occurs in the process of converting a digital signal into an analog signal in a conventional image output device is eliminated, the time required for image output can be shortened and a higher speed image output device can be realized.

Further, in the optical writing element of this embodiment, the light beam propagating through the core layer 22 of the optical waveguide portion is absorbed by the light absorber 251.
Since the light absorption amount of the substance is very stable as the substance value, the light absorption amount set by the light absorbers 251 to 25n does not change over a long period of time. Further, the light absorber driving mechanism 261 to
26n are the light absorbers 251 to 25n connected to each.
However, since it operates so as to set only two states of absorbing a part of the light beam propagating through the core layer 22 or not absorbing it at all, the light absorption amount by the light absorbers 251 to 25n is made continuous. It is possible to realize an optical writing element that has a very small change over time as a whole without causing fluctuations in the amount of light absorption that tends to occur when it is changed.

When a plurality of optical writing elements of this embodiment are arranged in an array and an image is written on the photosensitive member, the optical writing element of this embodiment attenuates the light propagating through the optical waveguide portion. The light incident on the optical writing element of the embodiment can be easily circulated freely by using the optical waveguide portion, and even if there are many writing points, one light source is enough, and the light emission amount of the light source varies. Even if it does, only one correction amount detection means and one correction means are required to correct it. As described above, in the present embodiment, a simple correction of the variation in the emitted light amount, which was possible only in the conventional optical writing means for writing the light from one light source on the photosensitive member by using the deflection optical system, is also possible. In this embodiment, a large-sized deflection optical system, which was a defect in the conventional optical writing means for writing the light from one light source on the photosensitive member by using the deflection optical system, is required because of its shape. It can be equal to or less than the conventional LED array or liquid crystal shutter that can be installed close to the member, and the characteristic change with time which is a problem in a small optical writing element cannot be avoided. It is possible to solve the drawback that the image quality is deteriorated without increasing the size.

2 to 4 show an optical writing element in which n = 2 in the above embodiment. A plurality of these elements are arranged in parallel on the common substrate 21 as one element at a density of 600 dpi over 250 mm to form an optical writing element array. Light absorbers 251 and 252
Is made of Si and both ends thereof are supported by holding springs 281, 282, 283 which are formed by anisotropic etching, and the holding springs 281, 282, 283 form the cladding layer 2.
It is fixed on 4. In the optical waveguide portion, the core layer 22 and the cladding layers 23 and 24 are made of SiON film and plasma CVD. As the optical waveguide part, a glass waveguide formed by sputtering can be used.

The substrate 21 is made of borosilicate glass. The substrate 21 may be made of metal as long as the clad layer 23 is sufficiently thick so that the substrate 21 does not absorb light. The light absorber driving mechanisms 261 and 262 are provided on the upper surface of the core layer 22.
The semiconductor switch 30 is provided between the transparent electrodes 291 and 292 and the light absorbers 251 and 252 which are provided so as to face the 252.
1, 302 is applied with an electric potential to attract the light absorbers 251 and 252 to the transparent electrodes 291 and 292 by electrostatic attraction. If the surfaces of the light absorbers 251 and 252 that contact the transparent electrodes 291 and 292 are thinly oxidized to form a very thin film of SiO ₂ , the light absorbers 251 and 252
Even when the light-absorbing material comes into close contact with the transparent electrodes 291, 292 on the core layer 22 to absorb a part of the light flux, the light absorber 251,
252 and the transparent electrodes 291, 292 are closely attached to each other so that the light absorber driving mechanism
It is possible to prevent the electric current from flowing through 2. Moreover, SiO ₂
Since this layer is thin, there is almost no optical confinement effect due to this SiO ₂ layer, and Si of the light absorbers 251 and 252 absorbs light well.

In such an optical writing element, the portion excluding the optical attenuating portion is produced by the following steps (1) to (3),
As a light source, a rod-shaped cold cathode discharge tube is placed parallel to the incident side. (1) The cladding layer 23, the core layer 22, and the cladding layer 24 are provided in this order on the substrate 21 to form the optical waveguide film. (2) This is patterned into a waveguide stripe. (3) A predetermined portion of the clad layer 24 in the waveguide stripe is removed by etching to expose the core layer 24 to form a waveguide.

These steps can be performed by general photolithography and dry etching. Apart from this, Si
Of the Si blocks and the holding springs 281, 282, 283 to be the light absorbers 251 and 252 by anisotropic etching of S
The transparent electrode 2 is formed by shaving from the i-wafer and attaching transparent electrodes 291 and 292 to the positions where the core layer 22 of the waveguide is exposed.
91, 292 via terminals B and C to the semiconductor switch 30.
The optical absorbers 251 and 252 having the terminals A wired thereto are aligned and overlapped with each other after wiring to the wirings 1, 302, and fixed by low melting point glass or anodic bonding to complete the optical writing element.

This optical writing element comprises light absorbers 251 and 251.
52 is grounded via the terminal A, and the semiconductor switch 30
1, 302 are turned on / off by a digital image signal from the signal processing circuit 27. As a result of measuring the optical output with respect to the input signal of this optical writing element, the light quantity could be controlled between 100% and 35% of the incident light quantity as shown in FIG. In this case, there is no variation in the amount of light that causes a problem, and by changing the amount of light of a single cold cathode discharge tube, the amount of light changes in all the elements (optical writing elements) of the optical writing element array by the same amount. It could be confirmed.

[0031]

As described above, according to the invention described in claim 1, an optical waveguide portion having a core layer having an exposed region for guiding light and a cladding layer surrounding the core layer, A plurality of light absorbers arranged corresponding to the exposed regions of the core layer and sequentially absorbing a part of the light guided by the core layer by a light absorption amount different by a factor of two; By mechanically holding and applying mechanical displacement or at least one of an electrical effect and a magnetic effect to the plurality of light absorbers in accordance with a signal from the outside, the core layer is provided. An optical attenuator having a plurality of light absorber driving mechanisms for selectively taking a state of absorbing a part of guided light and a state of not absorbing the light, and showing an optical attenuation amount set externally Capture the signal and store this signal for a predetermined time Since a signal processing circuit for transmitting to said light-absorbing member driving mechanism, it is possible to measure the image quality and miniaturization, cost reduction, improvement in yield at the same time.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a sectional view showing an embodiment of the present invention.

FIG. 3 is a perspective view showing the same embodiment.

FIG. 4 is a block diagram showing a part of the embodiment.

FIG. 5 is a diagram showing an experimental result of the same example.

FIG. 6 is a side view showing a conventional LED printer head and a photoconductor.

FIG. 7 is a diagram showing a circuit configuration and a light emitting dot row of the LED printer head.

FIG. 8 is a diagram showing a conventional writing system using laser light and a polygon mirror.

[Explanation of symbols]

 22 core layer 23, 24 clad layer 251 to 25n light absorber 261 to 26n light absorber driving mechanism 27 signal processing circuit

Claims (1)

[Claims] 1. An optical waveguide portion having a core layer having an exposed region for guiding light and a clad layer surrounding the core layer, and the core disposed corresponding to the exposed region of the core layer. A plurality of light absorbers that sequentially absorb a portion of the light guided by the layers by a different amount of light absorption, and a plurality of the light absorbers that are mechanically held and that respond to a signal from the outside. By applying a mechanical displacement or at least one of an electrical effect and a magnetic effect to the plurality of light absorbers, a state of absorbing a part of the light guided by the core layer and the light The light attenuator having a plurality of light absorber driving mechanisms for selectively taking the state of not absorbing light and a signal indicating the amount of light attenuation set externally are fetched, and this signal is stored for a predetermined time to store the light. Signal processing transmitted to absorber drive mechanism Optical writing device is characterized in that a road.