JPH09314898A - Method for driving optical writing apparatus and imaging apparatus of light emitting element array printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a printing speed without shortening a light emitting time by printing printed data in a first field and changing over an image forming position displacing means to other state before printing other data in a second field. SOLUTION: Since a ferroelectric liquid crystal element being a polarizing rotary element 13-2 is changed over from a shift state to a through state after the emission of light to the even-numbered data of a first field, a reversed polarity drive waveform or a step waveform is applied. During the time from the completion of the emission of light to the even-numbered data of the first field to the start of the emission of light to odd-numbered data of a second field, an image forming position displacing means 13 is changed over from the shift state to the through state. Continuously, the light emitting operation to the odd-numbered data of the second field is performed. At this time, the image forming position displacing means 13 is in the through state. An exposed dot is formed into an image on an exposure drum 14 at the position opposed to the light emitting element 11-1 on the drum 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting element array printer and an image pickup apparatus, and more particularly, in an optical writing unit and an image pickup apparatus of the light emitting element array printer, image forming position displacement according to an external electric signal. The present invention relates to an optical writing device of a light emitting element array printer including a means and a driving method of an imaging device.

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
There were the following. The light-emitting element array printer disclosed in Japanese Patent Application No. 06-260431 already proposed by the applicant of the present invention is, in an optical writing section of the light-emitting element array printer, according to an electric signal from the outside,
It is provided with image forming position displacing means for switching the path of the writing light and displacing the image forming position so as to expose the position where the exposing position is opposed to the light emitting element and the intermediate position therebetween.

FIG. 15 is a view showing a light emitting element array printer provided with such image forming position displacing means. As shown in this figure, the light emitting element array printhead 1 includes a light emitting element 1-1 and a plurality of light emitting elements 1-1 (for example, 128).
1) Light emitting element array chip 1 monolithically integrated
-2, the light emitting element array chip 1-2 and a driver IC (not shown) for driving the same are electrically connected to each other, and a plurality of (for example, 40) mounted substrates 1- It consists of three.

Further, a focusing rod lens array 2,
The image forming position displacing means 3 and the photosensitive drum 4 as a photosensitive medium are driven by the image forming position displacing means 3 by an electric signal from the outside to change the path of the writing light emitted according to the print data from the outside. It is possible to change the image forming position on the photosensitive drum 4 where an image is formed by the condensing rod lens array 2.

FIG. 16 is an enlarged view of the image forming position displacement means of the light emitting element array printer. Here, the image forming position displacing means 3 includes a polarizer 3-1, a polarization rotating element 3-2 made of a ferroelectric liquid crystal element, and a birefringent element 3-3 such as calcite.
It is composed of The polarizer 3-1 converts the writing light into, for example, linearly polarized light having a vibrating surface on the xz plane. The polarization rotator 3-2 is an element that rotates linearly polarized light by 90 ° and transmits it, or transmits it without rotating it in accordance with an electric signal from the driving device 3-4. Here, a ferroelectric liquid crystal element is used as the polarization rotation element 3-2.

The birefringent element 3-3 is an optical system in which a light incident surface is set perpendicularly to the light transmission direction (Z-axis direction) and its crystal axis is set to a predetermined angle φ in the yz plane, for example. It is a uniaxial crystal. When the incident linearly polarized light vibrates in the yz plane, it is transmitted (shifted) while being displaced by a predetermined distance, and when the linearly polarized light vibrates in the xz plane, it is transmitted (through) without displacement.

Therefore, by an electric signal from the outside,
The polarization rotation element 3-2 controls the polarization direction of the writing light incident on the birefringence element 3-3 to shift the transmitted light,
It is transmitted through. FIG. 17 is a diagram showing a principle operation of a light emitting element array printer having an image forming position displacing means.

Here, as an example, the odd number data is not shifted (through), and the even number data is shifted. The image forming position displacement means 3 converts the writing light from the light emitting element 1-1 into linearly polarized light having a vibrating plane in the xz plane by the polarizer 3-1. When printing odd-numbered data, an electric field having a polarity that does not rotate the polarized light is applied to the ferroelectric liquid crystal element that is the polarization rotating element 3-2.

In this case, the light incident on the birefringent element 3-3 oscillates in the xz plane, and therefore is transmitted (through) without being displaced. Next, when printing even-numbered data, the polarized light is applied to the ferroelectric liquid crystal element, which is the polarization rotation element 3-2, by 90 °.
A rotating electric field is applied. Birefringent element 3-
In this case, the light incident on 3 vibrates in the yz plane, and therefore is transmitted (shifted) while being displaced by a predetermined distance.

The displacement distance of the image forming position is defined as the distance between the light emitting elements (=
The exposure density can be doubled as the light emitting element density by setting the half of N) (= N / 2). FIG. 18 is a time chart for driving the image-forming position displacement means in the conventional example. Half the line period T is a field period, and the light emitting element 1-1 performs a light emitting operation for odd data and even data according to the switching of fields.

As described above, when printing odd number data,
The image forming position displacing means 3 is in the through state, and the image forming position displacing means 3 is in the shifted state when printing even data. When printing the nth line, a line cycle pulse is applied, and first, the light emitting operation is performed for each odd data. At this time, the image forming position displacing means 3 is in a through state. The exposure dot is imaged on the photosensitive drum 4 at a position facing the light emitting element 1-1.

The imaging position displacing means 3 switches from the through state to the shift state in the time until the light emission for the odd data is completed and the field is switched. A drive pulse waveform or a step waveform is applied to the ferroelectric liquid crystal element, which is the polarization rotation element 3-2, in order to switch from the through state to the shift state after the emission of odd data is completed.

Then, a light emitting operation is performed on even-numbered data. At this time, the image forming position displacing means 3 is in a shifted state. The exposure dot is imaged at a position displaced by a half pitch from the position facing the light emitting element 1-1 on the photosensitive drum 4. The imaging position displacement means 3 switches from the shift state to the through state in the time until the emission of even-numbered data is completed, the field is switched, and the next line (n + 1th line) starts.

To the ferroelectric liquid crystal element which is the polarization rotator 3-2, a drive pulse waveform or a step waveform of reverse polarity is applied to switch from the shift state to the through state after the emission of even data is completed. It Subsequently, the n + 1-th line is also operated in the same order.

[0015]

However, in order to support higher speed printing, it is necessary to shorten the time per line, and it is necessary to increase the response speed of the ferroelectric liquid crystal and the light emission power of the light emitting element. It was necessary to shorten the light emission time. For example, according to the driving method in the conventional example, odd data writing, ferroelectric liquid crystal element switching, even data writing, ferroelectric liquid crystal element switching (or even data writing, ferroelectric liquid crystal element switching, odd data writing, Although operations such as ferroelectric liquid crystal element switching) are performed in writing one line, the light emission time of the light emitting element is 125 μs.
ec, when the response speed of the ferroelectric liquid crystal is set to 80 μsec, it takes 4 times to complete a series of operations in one line.
A time of 05 μsec is required.

In this case, when printing is performed at a printing density of 1200 dpi (dots per inch) on A4 size vertically placed paper (the main scanning direction is the short side of the paper), 8 ppm (papers per minute: 8 per minute). The printing speed of (sheet) will be obtained. Therefore, for example, in order to achieve 10 ppm, the response speed of the ferroelectric liquid crystal needs to be 40 μsec or less, which may limit the selection of the material of the ferroelectric liquid crystal.

The present invention has been made in order to correspond to a higher speed printing than the conventional example, and makes the response time of the ferroelectric liquid crystal faster and the emission power of the light emitting element is increased to make the emission time. It is an object of the present invention to provide an optical writing device for a light emitting element array printer and a method for driving an imaging device, which can improve the printing speed without shortening the length.

[0018]

In order to achieve the above object, the present invention [1] switches a path of writing light in accordance with an electric signal from the outside, and exposes a position facing a light emitting element. And an image writing position displacing means for displacing the image forming position so as to expose an intermediate position between them, wherein the image forming position displacing means is a ferroelectric liquid crystal. , A polarization rotation element using at least one kind of liquid crystal selected from smectic liquid crystal exhibiting an electroclinic effect and an antiferroelectric liquid crystal, or a polarization rotation element using another electro-optical effect, and optically transparent It is composed of a polarization separation element made of a birefringent medium and a polarizer for giving polarized light. The image forming position displacement means is driven by an electric signal from the outside, and light is emitted according to print data from the outside. In the driving method in which the path of the writing light is changed to change the image forming position or to form an image without displacing the image, the print data for one line is divided into odd data and even data, and one line is temporally A method of dividing into a field and a second field and printing odd data and even data in each field, wherein when the nth line is printed, the image forming position displacement means is set to the n-1th second field. In the (n-1) th second field, the printed data is printed in the first field while the field state is maintained, and the imaging position displacement means is switched to the other state, and then the second field. In this case, the other data is printed.

[2] An image pickup apparatus having an incident image displacement means for relatively displacing an incident image in accordance with an electric signal from the outside to form an image on an image pickup element, wherein the incident image displacement means Is a polarization rotation element using at least one kind of liquid crystal selected from a ferroelectric liquid crystal, a smectic liquid crystal exhibiting an electroclinic effect, and an antiferroelectric liquid crystal, or a polarization using another electro-optical effect. A rotating element, a polarization separating element made of an optically transparent birefringent medium, and a polarizer that gives polarized light. The incident image displacing means is driven by an electric signal from the outside, and an imaging optical system is used. In the driving method of displacing the incident image incident on the image sensor to change the image forming position or forming the image without displacing the image, one frame of image data is converted into the first field data and the second field data. Is a driving method in which the incident image is displaced and the incident image is not displaced in each field to be imaged, and then electrically combined as one frame of image data. , While the incident image displacement means holds the state of the (n-1) th second field, the data of the first field of the nth frame is fetched, and the incident image displacement means is switched to the other state. The data of two fields is taken in.

[3] An image pickup apparatus comprising incident image displacement means for relatively displacing an incident image in accordance with an electric signal from the outside to form an image on an image pickup element, wherein the incident image displacement means Is composed of first incident image displacing means for displacing the incident image in the vertical direction with respect to the image pickup element and second incident image displacing means for displacing the incident image in the horizontal direction. Depending on the combination of displacement and non-displacement by the displacement means, vertical displacement, horizontal displacement, vertical horizontal displacement,
The first incident image displacing means comprises a ferroelectric liquid crystal, a smectic liquid crystal exhibiting an electroclinic effect, and an antiferroelectric liquid crystal. A first polarization rotator element using at least one selected liquid crystal or a first polarization rotator element using other electro-optical effect, and a first polarization separation element composed of an optically transparent birefringent medium. And a second polarization changing element having the same function as that of the first polarization rotating element, and the same function as that of the first polarization separating element. A second polarization splitting element, which gives polarized light in the traveling direction of light, the first polarization rotation element, the first polarization splitting element, the second polarization rotation element, and the second polarization rotation element. The polarization splitting elements of the Drive the incident image displacing means to displace the incident image incident on the image pickup element by the image forming optical system to change the image forming position or to form an image without displacing the image as much as one frame image. After the data is composed of four data of the first, second, third, and fourth field data, and the image is taken by performing vertical displacement, horizontal displacement, vertical horizontal displacement, and non-displacement of the incident image in each field. A driving method of electrically synthesizing as image data for one frame, when the first incident image displacement means is switched from the first field to the second field in the nth frame, and the third field. From the fourth field to the fourth field, the second incident image displacement means is switched from the second field to the third field. When switching from the field to the first field of the frame n + 1, or when switching the second incident image displacement means from the first field to the second field and when switching from the third field to the fourth field. And the first incident image displacement means is switched when switching from the second field to the third field and when switching from the fourth field to the first field of the (n + 1) th frame, and an image is captured in each field. It was done like this.

As described above, according to the driving method of the optical writing device of the light emitting element array printer of the present invention, when writing in the order of odd data to even data in the nth line, even data is written in the writing of the (n + 1) th line. It is characterized in that the data is written by reversing the order from odd data to odd data.

That is, since the (n-1) th line is written in the order of even data → odd data, the nth line is written in odd data → even data, and the (n + 1) th line is written in even data → odd data, the data is changed by switching lines.・ Odd numbers do not switch.

Therefore, it is not necessary to switch the polarization rotation element of the image-forming position displacement means by switching the line. Therefore, in writing for one line, the polarization rotator can be switched once. Further, according to the driving method of the image pickup apparatus of the present invention, (1) when the image pickup apparatus including the incident image displacement means captures the nth frame, the displacement image of the incident image and the non-displacement image are captured in this order. In this case, in the (n + 1) th frame, the non-displacement image and the displacement image are reversed in this order and imaged.

Therefore, in the imaging of the (n-1) th frame, the non-displacement image → the displacement image, in the nth frame, the displacement image → the non-displacement image, and in the (n + 1) th frame, the non-displacement image → the displacement image. Since the writing is performed, it is not necessary to switch the polarization rotation element of the incident image displacement means when the frame is switched.

Therefore, in the image pickup of one frame, the polarization rotator can be switched once. (2) First incident image displacement means for displacing the incident image in the vertical direction with respect to the image sensor, and second incident image displacement means for displacing the incident image in the horizontal direction with respect to the image sensor. In the image pickup device provided, when the nth frame is imaged, the first incident displacement means is changed from the first field to the second field.
When switching to the field and switching from the third field to the fourth field, switching is performed, and the second incident image displacement means is switched from the second field to the third field, and from the fourth field to n + 1.
It is characterized in that switching is performed when switching to the first field of the second frame.

Therefore, the polarization rotating elements of the first and second incident image displacing means need only perform switching once for every two fields.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of an optical writing unit of a light emitting element array printer to which the present invention is applied. As shown in this figure, in the light emitting element array printer, in the optical writing section of the light emitting element array printer, the writing light path is switched according to an electric signal from the outside, and the exposure position is set to a position facing the light emitting element. ,
Image forming position displacing means for displacing the image forming position so as to expose those intermediate positions is provided.

In the light emitting element array printer provided with the image forming position displacing means, the light emitting element array print head 11 has a light emitting element 11-1 and a plurality of (for example, 128) light emitting elements 11-1 are monolithically integrated. The light emitting element array chip 11-2, the light emitting element array chip 11-2, and a driver IC (not shown) for driving the light emitting element array chip 11-2 are electrically connected to each other, and a plurality (for example, 40) are mounted. It is composed of the substrate 11-3.

Further, the focusing rod lens array 1
2. The image forming position displacing unit 13 and the photosensitive drum 14 as a photosensitive medium are provided. The image forming position unit 13 is driven by an electric signal from the outside, and the path of the writing light emitted according to the print data from the outside is generated. It is possible to change and change the image forming position on the photosensitive drum 14 where the rod lens array 12 forms an image.

FIG. 2 shows an enlarged view of an example of the image forming position displacement means in the optical writing section shown in FIG. Here, the image forming position displacing means 13 is composed of a polarizer 13-1, a polarization rotating element 13-2 made of a ferroelectric liquid crystal element, and a birefringent element 13-3 such as calcite.

The polarizer 13-1 outputs writing light, for example, x
Converts to linearly polarized light having a vibrating surface on the z-plane. The polarization rotation element 13-2 responds to the electric signal from the driving device 13-4,
It is an element that transmits linearly polarized light by rotating it by 90 °, or transmits it without rotating it. here,
A ferroelectric liquid crystal element is used as the polarization rotation element 13-2.

The birefringent element 13-3 is an optical element in which a light incident surface is set perpendicularly to the light transmission direction (Z-axis direction) and its crystal axis is set to a predetermined angle φ in the yz plane, for example. It is a uniaxial crystal. Therefore, when the incident linearly polarized light vibrates in the yz plane, it is transmitted (shifted) while being polarized by a predetermined distance, and when the linearly polarized light vibrates in the xz plane, it is transmitted (through) without displacement.

Therefore, the polarization rotation element 13-2 is changed to the birefringence element 13- by the electric signal from the driving device 13-4.
The polarization direction of the writing light incident on the light source 3 is controlled, the transmitted light is shifted, and the through light is transmitted. As another example, when a liquid crystal element is used as the polarization rotation element 13-2, linear polarization of 90 ° is controlled electrically by an antiferroelectric liquid crystal element, a smectic phase ferroelectric liquid crystal element that gives an electroclinic effect, or the like. It is possible to use an element that can be rotated or can be transmitted as it is. A polarization rotation element using another electro-optical effect may be used.

Further, in the example of the structure of the image-forming position displacement means 13, the polarizer 13-1, the polarization rotation element 13-2, and the birefringence element 13-3 are laminated in the order in which the writing light is transmitted. The birefringence element 13-3 and the polarization rotation element 1
3-2 and the polarizer 13-1 may be rearranged. Also, regarding the positional relationship between the rod lens array 12 and the image-forming position displacing means 13, it is sufficient that the writing light from the light-emitting element array print head 11 can form an image on the photosensitive drum 14,
Its position is not specified. Further, the imaging position displacement means 13
The rod lens array 12 may be inserted between the respective constituent members, and an appropriate one may be selected in the limited space around the printer head.

S = [D (b ² −a ² ) / 2c ² ] sin2φ (1) where a = 1 / n _e , b = 1 / n ₀ c ² = a ² sin ² φ + b ² cos ² φ The above formula (1) is a formula for deriving the displacement amount S from the crystal axis direction φ and the crystal thickness D in the birefringent element. Where n ₀
And n _e are the refractive index anisotropies of the birefringent element at the incident light wavelength, and when calcite is used, they are expressed by the following equation (2).

N _e = 1.652 n ₀ = 1.484 (2) FIG. 3 shows the case where calcite is used as the birefringent element and 21.15 μm.
Is a diagram showing a relationship between the crystal axis direction φ and the crystal thickness D for obtaining the displacement amount of the optical axis angle φ [°] on the horizontal axis and the crystal thickness D [μm] on the vertical axis. .

As shown in this figure, the displacement amount of 21.15 μm corresponds to the displacement amount when the light emitting element array arranged in 600 dpi (dots per inch) is used to print at double the resolution of 1200 dpi. . From this, 21.
In order to obtain the displacement amount of 15 μm, various elements can be selected depending on the crystal axis direction φ and the crystal thickness D, and it can be selected from the viewpoints of ease of handling and workability. Here, for example, calcite having an angle φ = 16.5 ° and a thickness D = 396 μm is used.

The principle of operation of the light emitting element array printer of the present invention will be described below. FIG. 4 is a diagram showing a principle operation of a light emitting element array printer to which the present invention is applied. Here, it is assumed that the odd-numbered data is not shifted (through) and the even-numbered data is shifted.

The image forming position displacing means 13 is a polarizer 13-1.
Thus, the writing light from the light emitting element 11-1 is converted into linearly polarized light having a vibrating surface on the xz plane. When printing odd-numbered data, an electric field having a polarity that does not rotate the polarized light is applied to the ferroelectric liquid crystal element that is the polarization rotating element 13-2. In this case, the light incident on the birefringent element 13-3 is
Since it vibrates in the xz plane, it passes through without displacement.

Next, when printing even-numbered data, an electric field having a polarity that rotates the polarized light by 90 ° is applied to the ferroelectric liquid crystal element that is the polarization rotating element 13-2. In this case, the light incident on the birefringent element 13-3 vibrates in the yz plane, and therefore is transmitted (shifted) while being displaced by a predetermined distance.
I do. By setting the displacement distance of the imaging position to be half (= N / 2) of the distance (= N) between the light emitting elements, the exposure density can be double the light emitting element density.

[0041]

[Embodiment 1] FIG. 5 is a drive time chart of a light emitting element array print head having an image forming position displacing means according to a first embodiment of the present invention. Line cycle T shown in FIG.
Half of the time is the field period F shown in FIG. 5B, and the light emitting element 11-1 performs the light emitting operation for odd data and even data for each field. That is, FIG.
Odd data emission as shown in FIG. 5C and even data emission as shown in FIG. Then, a ferroelectric liquid crystal element drive pulse waveform as shown in FIG. 5E, FIG.
The ferroelectric liquid crystal element is in a switching state as shown in.

As described above, when printing odd number data,
As shown in FIG. 5G, the image-forming position displacing means 13 is in a through state, and the image-forming position displacing means 13 is in a shift state when printing even data. When printing the nth line, a line period pulse is applied, and first the first
The light emitting operation is performed on the odd data of each field. At this time, the image forming position displacing means 13 is in a through state. The exposure dot corresponds to the light emitting element 1 on the photosensitive drum 14.
An image is formed at a position facing 1-1.

After the light emission for the odd number data of the first field is completed, a drive pulse waveform or a step waveform is applied to the ferroelectric liquid crystal element which is the polarization rotator element 13-2 in order to switch from the through state to the shift state. To be done. The imaging position displacing means 13 switches from the through state to the shift state in a time period until the emission of the odd data is completed and the emission of the even data in the second field is started.

Then, the light emitting operation is performed for the even data of the second field. At this time, the imaging position displacement means 13
Is the state of shift. The exposure dot is the photosensitive drum 14
An image is formed at a position displaced by a half pitch from the position facing the upper light emitting element 11-1. Then, the (n + 1) th line is printed. In the first field of the (n + 1) th line,
Even data is printed as in the second field of the nth line. Therefore, the image forming position displacing means 13 keeps the shifted state, and the exposure dot is imaged at a position displaced by a half pitch from the position facing the light emitting element 11-1 on the photosensitive drum 14.

After the light emission for the even data of the first field is completed, the ferroelectric liquid crystal element, which is the polarization rotator 13-2, is switched from the shift state to the through state. Is applied. The imaging position displacing means 13 switches from the shift state to the through state in a time period until the light emission for the even data in the first field is completed and the light emission for the odd data in the second field is started.

Then, the light emitting operation is performed on the odd data of the second field. At this time, the imaging position displacement means 13
Is a through state. The exposure dot is the photosensitive drum 14
An image is formed at a position facing the upper light emitting element 11-1. Then, the (n + 2) th line is printed. The n + 2nd line is printed in the same order as the printing of the nth line,
The n + 3rd line is printed in the same procedure as the n + 1th line.

According to the driving method of the present invention, the image forming position displacing means 13 is kept in the state of the second field of the previous line, and the second field side data (odd number or even number) of the previous line is stored. Try to print. Therefore, the (n-1) th line is even data → odd data, n
Since the 1st line is written in the order of odd data → even data, and the (n + 1) th line is written in the order of even data → odd data, even / odd data is not switched by line switching. That is, it is not necessary to switch the ferroelectric liquid crystal element by switching the line.

FIG. 6 is a diagram showing the response speed given to the ferroelectric liquid crystal element of the drive system in the conventional example and the drive system of the first embodiment of the present invention, in which the horizontal axis indicates the printing speed [ppm],
The vertical axis shows the FLC response time [μsec]. However, the light emission time of the light emitting element is 125 μsec and does not change. This figure shows the upper limit of the time allotted to the ferroelectric liquid crystal with respect to the time for one line determined by the printing speed. In the figure, a shows the response of the ferroelectric liquid crystal to the printing speed when the driving method of the present invention is used, and b shows the response of the ferroelectric liquid crystal to the printing speed when the conventional driving method is used.

According to the present invention, the speed of the ferroelectric liquid crystal may be slower than that of the conventional example in order to obtain the same printing speed.
A wide range of materials can be selected. Further, the response speed of the ferroelectric liquid crystal becomes faster if the magnitude of the electric field is increased, but if it is allowed to be slow, there is no need to increase the electric field and it is not necessary to attach a special circuit system to the device. become.

On the contrary, when the response speed of the ferroelectric liquid crystal is constant, the printing speed can be increased. As is clear from FIG. 6, for example, when the response speed of the ferroelectric liquid crystal (for example, CS-1024 manufactured by Chisso Petrochemical Co., Ltd. is suitable) is 78 μsec, in the conventional drive method b, While the printing speed was 8 ppm, according to the driving method a of the present invention, the printing speed of 10 ppm can be obtained, and the improvement effect of 25% can be obtained. In order to obtain 10 ppm with the conventional driving method, it is necessary to improve to 40 μsec. In that case,
With the same material, the driving voltage must be increased or the material must be changed. If you want to use different materials,
The choice of materials may be limited.

[0051]

Second Embodiment In this embodiment, an application example (1) of the present invention to an image pickup device will be described. FIG. 7 shows a second embodiment of the present invention.
FIG. 3 is a diagram showing an example of an image pickup apparatus including an incident image displacement unit that relatively displaces an incident image in accordance with an electric signal from the outside to form an image on an image sensor according to an embodiment.

The applicable range of the present invention is applied not only to the optical writing section of the light emitting element array printer but also to the image pickup apparatus. This image pickup device responds to an electric signal from the outside.
The image pickup apparatus is provided with an incident image displacing means for relatively displacing an incident image to form an image on an image pickup device. Since the solid-state image pickup elements are arranged in a two-dimensional matrix array, there are cases where the resolution is increased one-dimensionally in one direction and cases where the resolution is increased two-dimensionally by shifting in two directions. However, the driving method of the present invention is applied only to the one in which the resolution is increased one-dimensionally in one direction. Here, a case will be described in which the resolution is increased by shifting only one direction in the y-axis direction. In another example, in the case of shifting in one direction in the x-axis direction to increase the resolution, there is a case of shifting in the direction of 45 degrees from the x-axis to the y-axis by a distance of ½ of the array pitch. Since the configuration and operation are the same, the description is omitted.

The light 21 from the subject passes through an image forming optical system 22 such as a lens and an incident image displacing means 23 and is picked up by a solid-state image pickup device 24 arranged in a matrix. The incident image displacing means 23 causes the light from the subject 2
1 is converted into, for example, linearly polarized light having a vibrating surface in the yz plane. The polarization rotation element 23-2 is an element that rotates linearly polarized light through 90 ° and transmits it, or transmits it without rotating it according to an electric signal from the driving device 25. Here, a ferroelectric liquid crystal element is used as the polarization rotation element 23-2. The birefringent element 23-3 has a light incident surface set perpendicular to the light transmission direction (Z-axis direction), and its crystal axis is, for example, in the yz plane and set to a predetermined angle φ from the z-axis direction. , An optical uniaxial crystal.

When the incident linearly polarized light vibrates in the yz plane, it is transmitted (shifted) while being displaced by a predetermined distance,
When the linearly polarized light vibrates in the xz plane, it passes through without displacement. Therefore, the polarization rotation element 23-2 is changed to the birefringence element 23- by the electric signal from the driving device 25.
The polarization direction of the writing light incident on the light source 3 is controlled, the transmitted light is shifted, and the through light is transmitted.

As another example, when a liquid crystal element is used as the polarization rotation element 23-2, an antiferroelectric liquid crystal element, a smectic phase ferroelectric liquid crystal element which gives an electroclinic effect, or the like,
It is possible to use an element capable of rotating linearly polarized light by 90 ° or transmitting it as it is by electrical control. A polarization rotation element using another electro-optical effect may be used. In FIG. 7, reference numeral 26 is a signal processing device, and 27 is a synchronization signal generating device.

FIG. 8 is a diagram showing the principle of operation of an image pickup apparatus to which the present invention is applied. FIG. 8A shows an image through state in the image pickup apparatus, and FIG. 8B shows the image pickup apparatus. 3 is a diagram showing an image shift state in FIG. First, the operation when the incident image is not displaced will be described. FIG.
As shown in (a), the incident image displacement means 23 includes a polarizer 23.
By -1, the light 21 from the subject is converted into linearly polarized light having a vibrating surface on the yz plane.

An electric field having a polarity for rotating polarized light by 90 ° is applied to the ferroelectric liquid crystal element which is the polarization rotating element 23-2. In this case, the light incident on the birefringent element 23-3 vibrates in the xz plane, and therefore is transmitted (through) without being displaced. Next, the operation for displacing the incident image will be described. As shown in FIG. 8B, the polarization rotation element 2
An electric field having a polarity that does not rotate polarized light is applied to the ferroelectric liquid crystal element 3-2.

In this case, the light incident on the birefringent element 23-3 vibrates in the yz plane, so that the light is transmitted (shifted) while being displaced by a predetermined distance. By setting the incident image displacement distance to be half (= P / 2) of the array interval (= P) of the solid-state image sensor 24, the image of the subject is captured by an image relatively displaced by a half pitch between the image sensors. And sent to the signal processing system.

In the signal processing system, both images are combined to reconstruct an image of the subject. As a result, the resolution of the image of the subject is increased in the y-axis direction. In FIG. 8, reference numeral 22 is an image forming optical system such as a lens. FIG. 9 is a conceptual diagram showing a state in which the incident image showing the second embodiment of the present invention is displaced relatively to the image pickup device. Here, the case of one-dimensional displacement in which the displacement is performed in an oblique direction is shown. The solid-state image sensor 24 of the image pickup device is installed on a tile, and an incident image 28 is formed on the image pickup surface. The solid-state image sensor 2 that captured the image here
4 is hatched.

FIG. 9A shows a case where the incident image 28 is formed on the solid-state image pickup device 24 without being displaced in the first field. FIG. 9B shows a state in which, in the second field, the incident image displacement means 23 displaces the incident image 28 diagonally by a half pitch of the solid-state image sensor 24. FIG. 10 shows a second embodiment of the present invention, FIG.
6 is a conceptual diagram in which a captured image of a first field and a captured image of a second field in FIG. As shown in this figure, it is understood that the resolution is increased by the displacement of the incident image and the electrical synthesis between the captured images.

The operation when the driving method of the present invention shown in FIG. 5 is applied to such an image pickup apparatus will be described.
FIG. 11 is a drive timing chart when the drive timing of FIG. 5 is applied to drive the image pickup apparatus. FIG.
Half the frame period T shown in FIG.
In the field period F shown in (b), the image sensor captures an image formed without displacement for each field and an image relatively displaced. That is, an incident image that is not displaced as shown in FIG. 11C, an incident image that is displaced as shown in FIG. 11D, and a ferroelectric liquid crystal element drive pulse as shown in FIG. The waveform is the switching state of the ferroelectric liquid crystal element as shown in FIG.

When the nth frame is imaged, a frame cycle pulse is applied to first capture the imaged image of the first field. At this time, the incident image displacing means 23 is in a through state. The image of the subject is formed on the solid-state image sensor 24 without being displaced, and is imaged. After the imaging of the first field is completed, a drive pulse waveform or a step waveform is applied to the ferroelectric liquid crystal element, which is the polarization rotation element 23-2, in order to switch from the through state to the shift state. The incident image displacing means 23 is switched from the through state to the shifted state by the time until the image pickup is started.

Then, the second field is imaged. At this time, the incident image displacement means 23 is in a shifted state. The image of the subject is displaced by a distance that is half the array pitch of the solid-state image pickup element 24, forms an image on the solid-state image pickup element 24, and is picked up by the image pickup element. Then, the (n + 1) th frame is imaged.

In the first field of the (n + 1) th frame, the shifted incident image is picked up as in the second field of the nth frame. Therefore, the incident displacement means 23
Remains in the shifted state, and the image of the subject is displaced by a distance of half the array pitch of the solid-state image sensor 24 to form an image on the solid-state image sensor, and the image is captured by the image sensor. First
After capturing the image of the displaced object in the field, a drive pulse waveform or a step waveform of reverse polarity is applied to the ferroelectric liquid crystal element, which is the polarization rotation element 23-2, in order to switch from the shift state to the through state. To be done. The incident image displacement means 23 is switched from the shift state to the through state by the time until the imaging in the second field is started.

Subsequently, the second field is imaged. At this time, the incident image displacing means 23 is in a through state. Therefore, the incident image is formed on the image pickup element without being displaced and is picked up. Then, the (n + 2) th frame is imaged.
The n + 2 th frame is imaged in the same order as the n th frame is imaged, and the n + 3 th frame is imaged in the same procedure as the n + 1 th frame.

Even in such an image pickup apparatus for the purpose of increasing the resolution, the speed can be increased by applying the driving method of the present invention shown in FIG. For example,
This is effective when high-speed imaging is required, such as when the frame frequency is high and high image quality is desired.

[0067]

Third Embodiment Next, an application example (No. 2) of the present invention to an image pickup device will be described. FIG. 12 is a diagram showing an example of an image pickup apparatus provided with an incident image displacement means for relatively displacing an incident image to form an image on an image pickup element according to the third embodiment of the present invention. In the second embodiment, only the case where the resolution is increased one-dimensionally in one direction has been described, but in this embodiment, as shown in FIG. 12, a shift in the x-axis direction and a shift in the y-axis direction are combined. Therefore, it can be applied in some applications even when the resolution is increased in two dimensions.

That is, the shift in the x-axis direction and the shift in the y-axis direction are combined to increase the resolution two-dimensionally. Light (incident light) 31 from a subject passes through an image forming optical system 32 such as a lens and an incident image displacement means 33, and is imaged by a solid-state image sensor 34 arranged in a matrix.
The incident image displacement means 33 includes a polarizer 33-1, a first polarization rotation element 33-2, a first birefringence element 33-3, and a second polarization rotation element 33- in order from the traveling direction of the incident light 31.
4 and the second birefringent element 33-5. Light 31 (incident light) from the subject by the polarizer 33-1
Is converted into, for example, linearly polarized light having a vibration plane on the xz plane.
The first polarization rotation element 33-2 is an element that rotates linearly polarized light by 90 ° and transmits it, or transmits it without rotating it in accordance with an electric signal from the driving device 33-6.

The first birefringent element 33-3 shifts the incident light 31 in the y-axis direction, and sets the light incident surface perpendicular to the transmission direction (Z-axis direction) of the incident light 31. It is an optical uniaxial crystal having a crystal axis in the yz plane and set at a predetermined angle from the z-axis direction. The second polarization rotation element 33-4 has the same function as the first polarization rotation element 33-2.

The second birefringent element 33-5 receives the incident light 31
Is shifted in the x-axis direction, the incident surface of the incident light 31 is set perpendicularly to the transmission direction (Z-axis direction) of the incident light 31, and its crystal axis is in the xz plane and in the z-axis direction. Is an optical uniaxial crystal set at a predetermined angle from. When the incident linearly polarized light vibrates in the xz plane, it is transmitted (shifted) while being displaced by a predetermined distance in the x-axis direction, and the linearly polarized light is y.
When vibrating in the z-plane, it passes through without displacement. Therefore, the first polarization rotation element 33-2 controls the polarization direction of the writing light incident on the first birefringence element 33-3 by the electric signal from the first driving device 33-6, and the y-axis direction. The transmitted light is shifted to or transmitted through.

Further, the second polarization rotation element 33-4 controls the polarization direction of the writing light incident on the second birefringence element 33-5 by the electric signal from the second driving device 33-7, The transmitted light is shifted in the x-axis direction or passed through. Therefore, the incident image is displaced two-dimensionally by combining the shifts in the x-axis direction and the y-axis direction. For example, there is a solid-state image sensor on the image pickup surface.

FIG. 13 is a plan view showing one pixel of a solid-state image pickup device showing the third embodiment of the present invention. As shown in FIG. 13A, there are openings 36 and non-openings 37 such as wiring,
The aperture ratio is said to be 20% to 40%. Therefore, even if an image is formed by the image forming optical system, the image is discrete and the resolution is low. For example, in the case where the opening of the solid-state image sensor and the first imaging area (area that can be imaged without shifting) in the present imaging device are set as shown in FIG.
Therefore, the fourth imaging region 38 is blocked by the non-opening portion 37. Therefore, in the present imaging device, the displacement in the x-axis direction and the displacement in the y-axis direction are combined to combine the second to fourth imaging regions 3
8 can be imaged. The image obtained by this is
The signals are combined by the signal processing unit, and the resolution is improved twice in the vertical and horizontal directions.

The polarization rotator used here is the same as that used in the first and second embodiments, and therefore its explanation is omitted. Further, the incident image displacing means 33 does not have to be in the order of the above configuration, and the first birefringent element 33-3, the first polarization rotation element 33-2, the polarizer 33-1 and the second polarization rotation element are included. 33-4, the second birefringent element 33-5, or the like, which is not excluded from the scope of application of the present invention.
Although the first birefringent element 33-3 is displaced in the y-axis direction and the second birefringent element 33-5 is displaced in the x-axis direction, the displacement directions of the two may be reversed.

The image pickup apparatus having the above-described structure shown in FIG. 12 has a first polarization rotation element 33-2 and a second polarization rotation element 33-.
The incident image is displaced relative to the solid-state image sensor 34 due to the combination of polarization rotation in each of the four. Table 1 shows the regions where the image can be picked up per pixel by the combination of the polarization rotation states in the first and second polarization rotation elements and the shifts generated in the first and second birefringence elements. is there.

[0075]

[Table 1]

That is, one frame is composed of four fields and each field is imaged in each field. to this,
The drive system of the present invention is applied. FIG. 14 is a drive timing chart of the incident image displacing means of the present invention in an image pickup apparatus having a two-dimensional incident image displacing means according to the third embodiment of the present invention. FIG. 14
14B is a field period F, FIG. 14C is a drive pulse waveform of the first polarization rotation element, FIG. 14D is the state of the first polarization rotation element, and FIG. 14E is the second polarization. Drive pulse waveform of the rotating element, FIG. 14 (f) shows the state of the second polarization rotating element, FIG. 14 (g) shows the function of the first birefringent element, and FIG.
14 (h) shows the function of the second birefringent element, and FIG. 14 (i) shows the imaging region.

As shown in the figure, one frame is composed of four fields, and each field captures an image in each imaging region shown in FIG. 13B. The first in the nth frame
The polarization rotator 33-2 holds the state (for example, no rotation) of the fourth field of the previous frame, and the second polarization rotator 33-4 changes the state of the fourth field of the previous frame from the other. State (for example, 90 ° rotation). After the time for transition (response time), the incident image is shifted in the x-axis direction in the second birefringent element 33-5, and the second imaging region moves to the opening of the solid-state imaging element 34. , Imaged.

In the second field, the first polarization rotation element 33-2 shifts from the state of the first field to the other state (for example, 90 ° rotation), and the second polarization rotation element 33-4. Is the state of the first field (eg 9
0 ° rotation). After the transition time (response time), the incident image shifts in the y-axis direction at the first birefringent element 33-3 and shifts in the x-axis direction at the second birefringent element 33-5. To do. That is, the fourth imaging region moves to the opening of the solid-state imaging device 34 and is imaged.

In the third field, the first polarization rotation element 33-2 has the second field state (for example, 90 °).
Second polarization rotation element 33-4, which holds the
Shifts the state of the second field to the other state (for example, no rotation). After the time for transition (response time), the incident image shifts in the y-axis direction in the first birefringent element 33-3, and the third imaging region moves to the opening of the solid-state imaging element 34. , Imaged.

In the fourth field, the first polarization rotation element 33-2 shifts from the state of the third field to the other state (for example, no rotation), and the second polarization rotation element 33-4. Holds the state of the third field (for example, no rotation). After the time for transition (response time), the incident image does not shift, and the first imaging region is imaged by the solid-state imaging device 34. To be done.

In the next (n + 1) th frame, switching is performed at the same timing as the nth frame. With this configuration, according to this embodiment, each polarization rotation element only needs to perform switching once for every two fields to configure the state for four fields.

For example, if the frame cycle T is 60 Hz (1
6.7 msec), the time per field is 4.16 msec. By using the driving method of the present invention, it is possible to allow a margin for the switching time of the polarization rotation element. This also relaxes the time limitation when selecting the material of the polarization rotation element, for example. Further, when obtaining a smooth image such as a moving image, it is necessary to increase the frame frequency, which is also advantageous.

The present invention is not limited to the above embodiments, and various modifications can be made based on the spirit of the present invention, and these modifications are not excluded from the scope of the present invention.

[0084]

As described in detail above, according to the present invention, the following effects can be achieved. [1] According to the invention as set forth in claim 1, the emission speed can be improved without increasing the response speed of the ferroelectric liquid crystal or increasing the emission power of the light emitting element to shorten the emission time. A method for driving an optical writing device of an element array printer can be obtained.

[2] According to the second aspect of the present invention, it is possible to increase the speed even in the image pickup apparatus for the purpose of increasing the resolution. For example, it is effective when high-speed imaging is required, such as when the frame frequency becomes high and the image quality is improved. [3] According to the invention described in claim 3, in an image device intended for high resolution, it is possible to allow a switching time of the polarization rotator to have a margin, and a frame frequency is set when a smooth image such as a moving image is obtained. It needs to be high, which is also advantageous.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an optical writing unit of a light emitting element array printer to which the present invention is applied.

FIG. 2 is an enlarged view of an example of image forming position displacement means in an optical writing unit of a light emitting element array printer to which the present invention is applied.

[FIG. 3] Using calcite as a birefringent element, 21.15μ
FIG. 6 is a diagram showing a relationship between a crystal axis direction φ and a crystal thickness D for obtaining a displacement amount of m.

FIG. 4 is a diagram showing a principle operation of a light emitting element array printer to which the present invention is applied.

FIG. 5 is a drive time chart of the light emitting element array print head including the image forming position displacement means according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a response speed given to the ferroelectric liquid crystal element of the driving method in the conventional example and the driving method of the first embodiment of the present invention.

FIG. 7 is an example of an image pickup apparatus having an incident image displacement means for relatively displacing an incident image according to an electric signal from the outside to form an image on an image pickup element according to a second embodiment of the present invention. FIG.

FIG. 8 is a diagram showing a principle operation of an image pickup apparatus to which the present invention is applied.

FIG. 9 is a conceptual diagram showing a state in which an incident image showing a second embodiment of the present invention is relatively displaced with respect to an image pickup element.

FIG. 10 is a conceptual diagram showing a second embodiment of the present invention in which a captured image of the first field and a captured image of the second field in FIG. 9 are electrically combined to generate an image for one frame.

FIG. 11 is a drive timing chart when the drive timing of the light emitting element array print head according to the second embodiment of the present invention is applied to drive the image pickup apparatus.

FIG. 12 is a diagram showing an example of an image pickup apparatus provided with an incident image displacement means for relatively displacing an incident image to form an image on an image pickup element according to the third embodiment of the present invention.

FIG. 13 is a plan view showing one pixel of a solid-state image sensor showing a third embodiment of the present invention.

FIG. 14 is a drive timing chart of the incident image displacing unit in the image pickup apparatus including the two-dimensional incident image displacing unit according to the third embodiment of the present invention.

FIG. 15 is a diagram showing a light emitting element array printer including an image forming position displacing unit.

FIG. 16 is an enlarged view of image forming position displacement means of a conventional light emitting element array printer.

FIG. 17 is a diagram showing a principle operation of a light emitting element array printer including a conventional image forming position displacement means.

FIG. 18 is a time chart of driving the image-forming position displacement means in the conventional example.

[Explanation of symbols]

 11 Light-Emitting Element Array Print Head 11-1 Light-Emitting Element 11-2 Light-Emitting Element Array Chip 11-3 Substrate 12 Converging Rod Lens Array 13 Imaging Position Displacement Means 14 Photosensitive Drum 13-1, 23-1, 33-1 Polarized Light Child 13-2 Polarization rotating element by ferroelectric liquid crystal element 13-3 Birefringent element 13-4 Driving device 21, 31 Light from a subject (incident light) 22, 32 Imaging optical system 23, 33 Incident image displacement means 23 -2 polarization rotation element 23-3 birefringence element 24,34 solid-state image sensor 25 drive device 26 signal processing device 27 synchronization signal generator 28 incident image 33-2 first polarization rotation element 33-3 first birefringence element 33-4 2nd polarization rotation element 33-5 2nd birefringence element 33-6 1st drive device 33-7 2nd drive device 36 Opening 37 Non-opening of wiring etc. 38 second imaging region

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G03B 27/32 (72) Inventor Yukio Nakamura 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Within the corporation

Claims (3)

[Claims] 1. An image forming method in which a path of writing light is switched according to an electric signal from the outside, and an image forming position is displaced so that an exposing position is opposed to a light emitting element and an intermediate position therebetween is exposed. An optical writing device for a light emitting element array printer comprising position displacement means, wherein the image formation position displacement means is selected from a ferroelectric liquid crystal, a smectic liquid crystal exhibiting an electroclinic effect, and an antiferroelectric liquid crystal. A polarization rotator using at least one kind of liquid crystal or a polarization rotator using other electro-optic effect, a polarization separation element made of an optically transparent birefringent medium, and a polarizer for giving polarized light. The image forming position displacing means is driven by an electric signal from the outside, and the path of the writing light emitted according to the print data from the outside is changed to change the image forming position. In the driving method of forming an image without positioning, the print data for one line is divided into odd number data and even number data, and one line is temporally divided into the first field and the second field. ,
A method of printing even-numbered data, wherein when the n-th line is printed, the image-forming position displacement means is set to the (n-1) -th second
In the (n-1) th second field, the printed data is printed in the first field while the field state is maintained, and the imaging position displacement means is switched to the other state, and then the second field. 2. A method for driving an optical writing device of a light emitting element array printer, characterized in that the other data is printed. 2. An image pickup apparatus comprising an incident image displacement means for relatively displacing an incident image according to an electric signal from the outside to form an image on an image pickup element, wherein the incident image displacement means is , A polarization rotator using at least one kind of liquid crystal selected from a ferroelectric liquid crystal, a smectic liquid crystal exhibiting an electroclinic effect, and an antiferroelectric liquid crystal, or a polarization rotator using another electro-optical effect. And a polarization separation element made of an optically transparent birefringent medium, and a polarizer for giving polarized light. The incident image displacement means is driven by an electric signal from the outside, and an imaging element is formed by an imaging optical system. In the drive method of displacing the incident image incident on the image plane, changing the image formation position, or forming an image without displacing the image, the image data for one frame is composed of the first field data and the second field data. , After the displacement of the incident image and the non-displacement of the incident image in each field are taken, 1
A driving method of electrically synthesizing as image data of frames, wherein when the nth frame is imaged, the incident image displacement means holds the state of the (n-1) th second field, The method of driving an image pickup apparatus, wherein the data of the first field is fetched, the incident image displacement means is switched to the other state, and then the data of the second field is fetched. 3. An image pickup apparatus comprising an incident image displacement means for relatively displacing an incident image according to an electric signal from the outside to form an image on an image pickup element, wherein the incident image displacement means is , First incident image displacing means for displacing the incident image in the vertical direction with respect to the image pickup element, and second incident image displacing means for displacing the incident image in the horizontal direction. By the combination of displacement and non-displacement by image displacement means, vertical displacement, horizontal displacement,
The present invention is capable of realizing four displacement states of vertical and horizontal displacement and non-displacement, wherein the first incident image displacement means is a ferroelectric liquid crystal, a smectic liquid crystal exhibiting an electroclinic effect, and an antiferroelectric effect. A first polarization rotator using at least one kind of liquid crystal selected from dielectric liquid crystals or a first polarization rotator using other electro-optical effect, and an optically transparent birefringent medium. First
And a second polarization rotation element having the same function as that of the first polarization rotation element, and the first polarization rotation element having the same function as the first polarization rotation element.
And a second polarization separation element having a function similar to that of the polarization separation element, the polarizer for giving polarized light from the traveling direction of the light, the first polarization rotation element, and the first polarization separation element. , The second polarization rotation element and the second polarization separation element are arranged in this order, and the incident image displacement means is driven by an electric signal from the outside to displace the incident image incident on the image sensor by the imaging optical system. In the drive method of forming an image without changing the image forming position or displacing the image forming position as it is, the image data for one frame is composed of four pieces of first, second, third and fourth field data, and each field is formed. Is a driving method of performing vertical displacement, horizontal displacement, vertical horizontal displacement, and non-displacement of the incident image, and then electrically synthesizing as image data for one frame. , The first incident image displacement means is switched when switching from the first field to the second field and at the time when switching from the third field to the fourth field, and the second incident image displacement means is switched to the second field. From the third field to the third field and from the fourth field to the first field of the (n + 1) th frame, or when switching the second incident image displacement means from the first field to the second field, Switching is performed when switching from the third field to the fourth field, and the first incident image displacement means is switched from the second field to the third field, and from the fourth field to n + 1.
A method for driving an image pickup device, characterized in that switching is performed when switching to the first field of the No. frame, and an image is captured in each field.