GB2353368A - Optical printer head with multiple light sources - Google Patents

Abstract

An optical printer head has a plurality of light sources 1,2, each with luminous dots arranging an identical pattern. An optical element 12, preferably a half mirror, a half mirror prism, a dichroic mirror or a total reflection mirror, guides light from the light sources to a single equi-magnification image formation element 10 so that the lights form an image in the pattern whilst being rendered continuous with each other. The light sources may be fluorescent luminous tubes.

Description

2353368 OPTICAL PRINTER HEAD This invention relates to an optical printer

head, and more particularly to an optical printer head for recording an image or the like on a record medium by means of a plurality of luminous elements.

An optical printer head which has been conventionally known In the art is generally adapted to form an Image or latent image on either a photosensitive drum or a record medium such as a developing paper or the like by means of light energy. Such a conventional optical printer is typically constructed so as to arrange a number of luminous dots at predetermined pitches. For example, an optical printer head to which a principle of a fluorescent luminous tube is applied includes an envelope which Is evacuated at a high vacuum and of which a part Is constituted by a substrate. The substrate is formed on an Inner surface thereof with a number of luminous dots. The luminous dots each are formed into a predetermined configuration and arranged, for example, in a row at predetermined intervals.

The luminous dots each are constituted by an anode having a phosphor deposited thereon. The substrate is also provided thereon with a planar control electrode so as to surround each of the luminous dots. Above the control electrode and luminous dots are stretchedly arranged filamentary cathodes each acting as an electron source. The luminous dots each are selectively driven for luminescence by a drive signal applied to an anode conductor, resulting in dot-like light being outwardly emitted through the envelope.

In formation of a desired image or record on a record medium of a standard size by means of such an optical printer head as described above, a direction in which the luminous dots are arranged in a row or a longitudinal direction of the optical printer head and a width direction of the record medium are defined to be a main scanning direction and a direction perpendicular thereto Is defined to be a sub-scannIng direction. Thus, the formation is carried out by moving the optical printer head and record medium relatively to each other and in parallel I to each other in the sub-scanning direction.

For example, recording on a record medium of a size A3 is conventionally carried out by a first method using an optical printer head which is so constructed that a length thereof defined in the a scanning direction In which luminous dots are arranged in a row corresponds to a width of an image formation region of the size A3 record medium.

Alternatively, it may be carried out by a second method using two optical printer heads each of which is so constructed that a length thereof in a main scanning direction in which luminous dots are arranged in a row corresponds to a width of an image formation region of a s1ze A4 record medium smaller than a width of a size-A3 record medium. In the second method, the two optical printer heads are arranged so as to be spaced from each other at a predetermined interval in a sub-scannIng direction and without defining any interval therebetween in the main scanning direction or in a manner to overlap each other in the main scanning direction.

The optical printer head used in the first method described above is formed into a luminous width corresponding or conforming to a record width of the record medium. However, formation of the optical printer head into such an increased length actually leads to vibration of the filamentary cathodes in the envelope due to application of any external Impact thereto, to thereby cause a variation In amount of light emitted therefrom, resulting in substantially affecting quality of an image or record formed. Also, such vibration of the filamentary cathodes brings about contact of the filamentary cathodes with the anodes and/or control electrode, to thereby cause separation of the phosphor from the anode or breakage of the phosphor by electrical short-circuiting. In order to prevent vibration of the filamentary cathodes, It Is required to arrange vibration proofing members at predetermined positions in the envelope.

An increase in length of the optical printer head causes another disadvantage of rendering application of tension to the filamentary cathodes substantially difficult. Also, it leads to distortion of the substrate constituting a part of the envelope of the optical printer head.

2 In the second method using two optical printer heads, two optical systems are individually arranged for the two optical printer heads, respectively. Two such optical systems are manufactured according to the same specifications so as to exhibit the same performance. Nevertheless, actually they are caused to be delicately different in optical performance from each other. This results in misregistration, color shift and the like occurring between light illuminated on the record medium from one of the optical printer head and that from the other one, to thereby fail to form a single uniform and continuous row on the record medium, leading to a deterioration in quality of an image formed thereon.

The present invention has been made in view of the foregoing disadvantage of the prior art.

Accordingly, It is an object of the present invention to provide an optical printer head which is capable of being formed into an increased length without causing any misregistration and color shift.

In accordance with the present invention, an optical printer head is provided. The optical printer head includes a plurality of light sources each including a plurality of luminous dots arranged in an Identical pattern and acting as an anode, an element for equi-magnifIcation image formation (hereinafter referred to as "equi-magnification image formation element') arranged in a manner to be common to the light sources, and an optical element arranged in a manner to face the light sources and guiding lights emitted from the light sources to the equimagnification image formation element so as to permit the lights to form an image in the pattern while being rendered continuous with each other.

In a preferred embodiment of the present invention, the pattern is formed by arranging the luminous dots at predetermined pitches in at least one row. Lights emitted from the luminous dots are arranged In at least a row on a record medium while being continuous with each other at predetermined intervals.

In a preferred embodiment of the present invention, the luminous dots may be arranged either in a row or in an offset 3 manner.

In a preferred embodiment of the present invention. the optical element is selected from the group consisting of a half mirror, a half mirror prism, a dichroic mirror and a total reflection mirror. A half mirror and a half mirror prism each may be varied in reflectance and transmittance to a level between 100% and 90%. In this instance, when the reflectance is 50%, the transmittance is 50%, resulting in a sum of both being 100%. A dichroic mirror exhibits increased reflectance and transmittance with respect to a specific wavelength, resulting in having wavelength selecting characteristics, so that a necessity of arranging red (R), green (G) and blue (B) filter may be eliminated. A total reflection mirror carries out only reflection and keeps light from permeating therethrough.

These and other objects and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the accompanying drawings; wherein:

Fig. 1 is a sectional view showing a first embodiment of an optical printer head according to the present invention; Fig. 2 is a schematic perspective view showing an optical system and an optical path in the optical printer head of Fig. 1; Fig. 3 is a sectional view showing a second embodiment of an optical printer head according to the present invention; Fig. 4 is a sectional view showing a third embodiment of an optical printer head according to the present invention; Fig. 5 is a sectional view showing a fourth embodiment of an optical printer head according to the present invention; Fig. 6 is a sectional view showing a fifth embodiment of an optical printer head. according to the present invention; and Fig. 7 is a sectional view showing a sixth embodiment of an optical printer head according to the present invention.

Now, an optical printer head according to the present Invention will be described hereinafter with reference to the accompanying drawings.

An optical printer head according to the present 4 Invention Includes a plurality of light sources. The light sources each have luminous dots arranged in the same chain pattern. Also, in the present invention, a single (or a set of) lens array for equi- magnification image formation (selfoc lens array) is provided in common to the light sources for the Purpose of forming an image on a record medium. Incidence of light from each of the light sources on the common equi-magnification image formation lens array permits lights from the luminous dots of the light sources to form an image on the record medium In the continuous chain pattern described above. Thus, the chain pattern of the luminous dots of each of the light sources is arranged so as to be continuous with those of the remaining light sources, so that the chain patterns continuous with each other and extending over an increased distance may be defined in a main-scannIng direction of the record medium.

Referring first to Figs. 1 and 2, a first embodiment of an optical printer head according to the present invention is illustrated. An optical printer head of the illustrated embodiment Includes a first fluorescent luminous tube 1 acting as a first light source for emitting light in a lateral direction in Fig. I and a second fluorescent luminous tube 2 acting as a second light source for emitting light in a downward direction in Fig. I perpendicular to the direction in which the first fluorescent luminous tube I emits light. Two such fluorescent luminous tubes 1 and 2, as shown in Fig. 2, each include a luminous dot chain of the same size wherein luminous dots are arranged in a row at predetermined equal intervals. The fluorescent luminous tubes I and 2 are arranged at positions different from each other in a direction normal to the sheet of Fig. 1 or in the main scanning direction.

In the illustrated embodiment, the fluorescent luminous tubes 1 and 2 each include an envelope 5 constituted by an anode substrate 3 made of glass and a box-like casing 4 sealedly joined to the anode substrate 3. The anode substrate 3 is f ormed on a surface thereof positioned in the envelope 5 or an inner surface thereof with an anode 6, which includes a light-permeable anode conductor and a phosphor deposited on the anode conductor. The anode 6 is constituted by a number of luminous dots arranged in d row or a chain pattern such as an of f set pattern or the like at predetermined intervals in a direction normal to the sheet of Fig. 1. In the illustrated embodiment, the luminous dots are arranged in a single row or chain. The fluorescent luminous tubes I and 2 each have a main scanning direction def Ined in a direction in which the luminous dots are arranged. The fluorescent luminous tubes I and 2 and a record medium 7 are moved relatively to each other in a sub-scanning direction perpendicular to the main scanning direction.

The phosphor deposited on the anode conductor arranged on the anode substrate 3 of the envelope of each of the fluorescent luminous tubes I and 2 is constituted by a ZnO:Zn phosphor which is a zinc oxide containing phosphor. The phosphor is increased in width of an emission spectrum and exhibits a luminous color between a blue color region and a red color region.

The optical printer head also includes an equlmagnification image formation element 10 arranged so as to be common to both fluorescent luminous tubes 1 and 2. In the illustrated embodiment, the equimagnification image formation element 10 is positioned right below the second fluorescent luminous tube 2 and obliquely below the first fluorescent luminous tube 1. Also, the equl-magnification image formation element 10 has an optical axis defined in conformity to a direction in which the second fluorescent luminous tube 4 emits dot-like light. In the illustrated embodiment, the optical axis is defined so as to downwardly extend while being perpendicular to a plane of the record medium 7.

The equi-magnification image formation element 10 is provided on an incident side thereof with a filter 11. Above the filter 11 is arranged a half mirror 12 which acts as an optical element for introducing or guiding light emitted from each of the fluorescent luminous tubes 1 and 2 Into the equi-magnification image formation element 10. The half mirror 12 is so positioned that each of reflecting surfaces thereof is inclined by an angle of 45 degrees with respect to the direction in which each of the fluorescent luminous tube 1 and 2 emit light.

Dot-like light emitted from the first fluorescent luminous tube I is reflected by one of the reflecting surfaces of 6 the half mirror 12 which is a lower surface of the half mirror, to thereby be downwardly directed. Then, the light reaches the record medium 7 through the filter 11 and equi-magnIfication image formation element 10, to thereby form an Image on the record medium 7. Dot-like light emitted from the second fluorescent luminous tube 2 downwardly permeates through the half mirror 12 and then reaches the record medium 7 through the filter 11 and equi-magnification Image formation element 10 to form an image thereon.

Thus, dot-like lights emitted from the fluorescent luminous tubes 1 and 2, as shown in Fig. 2, f orm Images on the record medium 7 in the same pattern, which are arranged so as to be contiguous with each other to provide a dot-like image in a row in cooperation with each other. In the illustrated embodiment, luminous dots of the light are arranged in a row at predetermined intervals. More specifically, a chain of luminous dots of the first fluorescent luminous tube 1 and that of the second fluorescent luminous tube 2 are permitted to be arranged on the same line. Also, a last luminous dot at a terminal end of the luminous-dot chain of the first fluorescent luminous tube 1 and a f irst luminous dot at an initial end of the luminous dot chain of the second fluorescent luminous tube 2 are spaced f rom each other by a distance corresponding to one dot pitch.

The illustrated embodiment, as described above, is so constructed that the luminous dot chains of the first and second fluorescent luminous tubes 1 and 2 are continuous with each other on the record medium 7. Such construction may be ef f ectively applied to arrangement of three or more fluorescent luminous tubes.

Referring now to Fig. 3, a second embodiment of an optical printer head according to the present invention is illustrated. An optical printer head of the illustrated embodiment includes a half mirror prism 22 in place of the half mirror 12 incorporated in the f irst embodiment described above. The half mirror prism 22 is constituted of an optical device formed by a combination of four prism-shaped elements of the same configuration, wherein a contact surface or interface between each adjacent two of the prIsm-shaped elements constitutes a half 7 mirror plane. The remaining part of the illustrated embodiment including fluorescent luminous tubes 1 and 2, a filter 11, an equi-magnification image formation element 10, arrangement of luminous dots of the fluorescent luminous tubes, and the like may be constructed In substantially the same manner as the first embodiment described above.

In the second embodiment, the first and second fluorescent luminous tubes 1 and 2 may be arranged opposite to each other with the half mirror prism 22 being interposed therebetween, as shown in Fig. 3. Alternatively, the arrangement may be carried out as in Fig. 1. Thus, the illustrated embodiment permits a degree of freedom in design of the optical printer head to be significantly increased. However, the illustrated embodiment causes light to permeate through two of the prIsm-like elements of the half mirror prism 22, resulting in the light amount being reduced to 25%.

Referring now to Fig. 4, a third embodiment of an optical printer head according to the present invention is illustrated. An optical printer head of the illustrated embodiment includes two half mirrors 12 combined together so as to intersect each other at a right angle. First and second fluorescent luminous tubes 1 and 2 are arranged in a manner to f ace each other so that light emitted from each of the fluorescent luminous tubes may be incident on each of the half mirrors 12 at an angle of 45 degrees. The remaining part of the third embodiment may be constructed in substantially the same manner as the first embodiment described above. The illustrated embodiment causes the light amount to be reduced to 25% as in the second embodiment described above.

Referring now to Fig. 5, a fourth embodiment of an optical printer head according to the present invention is illustrated. An optical printer head of the illustrated embodiment is so constructed that three structure units each constituted by an optical printer head constructed as shown in Fig. 1 are arranged in a row in a sub-scanning direction. More particularly, the structure units each are constituted by a combination of first and second fluorescent luminous tubes 1 and 2, an equi- magnification image formation element 10 common to 8 both fluorescent luminous tubes.1 and 2, and a half mirror 12. The thus- constructed three structure units are provided with three kinds of red (R), green (G) and blue (B) filters 11R, 11G and 11B different In color, respectively, resulting in providing an RGB head module.

The RGB module head shown in Fig. 5 may be modified In various ways as desired. For example, the first and second fluorescent luminous tubes of the structure units may include color phosphors of R, G and B luminous colors, respectively. Thus, incorporation of the half mirror permits the flourescent luminous tubes of the same luminous color to be arranged in each of the structure units.

Alternatively, the module head of Fig. 5 may be modified in such a manner that a dIchroic mirror is substituted for the half mirror 12. In this Instance, such construction fails to permit plural fluorescent luminous tubes of the same color to be arranged in each structure unit.

This is for the reason that arrangement of two fluorescent luminous tubes of a red luminous color in one structure unit and use of a dichroic mirror reflecting red light as the optical element cause red light emitted from one of the fluorescent luminous tube to be reflected by the dichroic mirror, to thereby fail to permit the red color to be incident on the equi-magnification Image formation element 10 although it permits red color emitted from the other fluorescent luminous tube to be incident thereon after reflection thereof by the mirror.

Thus, arrangement of the dichroic mirror fails to permit two fluorescent luminous tubes of the same luminous color to be arranged in each of the structure units. Therefore, it is required that the fluorescent luminous tubes of the same luminous color are arranged separately from each other in two units in which dichroic mirrors different in reflecting color are arranged, respectively.

For example, in the structure unit in which the dichroic mirror reflecting light of a red color is arranged, one of the fluorescent luminous tubes of a red luminous color is arranged at a position at which the light is downwardly directed toward a record medium 7. Also, for example, in the structure unit In 9 which the dichroic mirror reflecting light of a green color is arranged, the other fluorescent luminous tube of a red luminous color is arranged at a position at which the light downwardly permeates therethrough toward the record medium 7. Thus, the first and second fluorescent luminous tubes I and 2 are arranged at positions different from each other based on the main scanning direction, so that exposure of the record medium 7 to the lights f rom the tubes at a suitable time interval permits formation of images on the record medium to be continuously carried out in the same pattern, resulting in red dot-like images being formed in a row. In the illustrated embodiment, the image formation is carried out in a row at predetermined pitches. The same is true of the fluorescent luminous tubes 1 and 2 of blue and green luminous colors as well.

Referring now to Fig. 6, a fifth embodiment of an optical printer head according to the present Invention is illustrated. An optical printer head of the illustrated embodiment is so constructed that a common equimagnif!cation image formation element 10 is mounted on a holder 30 and f irst and second fluorescent luminous tubes 1 and 2 are arranged so as to be perpendicular to an optical axis of the equi-magnif ication image formation element 10 and mounted on the holder 30 so as to face each other. The holder 30 is provided therein with a total reflection mirror 31. The total reflection mirror 31 functions to reflect light emitted from each of the fluorescent luminous tubes 1 and 2 by an angle of 90 degrees, to thereby guide It to the equi-magnification image formation element 10 common to the fluorescent luminous tubes 1 and 2 which is arranged below the total reflection mirror 31. Thus, lights emitted from the fluorescent luminous tubes I and 2 pass through filters 11 and then are reflected by the total reflection mirror 31, to thereby be guided to the equi-magnification image formation element 10, followed by irradiation on the record medium for formation of an Image thereon. The total reflection mirror 31 may be replaced with a dichroic mirror.

On the record medium 7, the dot chain of the f irst fluorescent luminous tube 1 and that of the second fluorescent luminous tube 2 are arranged at positions different from each other on the same line in the main scanning direction. Also, the dot chains of both fluorescent luminous tubes I and 2 are arranged at positions somewhat different from each other in the sub-scanning direction. Thus, In the illustrated embodiment, an optical axis of light from the first fluorescent luminous tube 1 and that from the second fluorescent luminous tube 2 are not rendered coincident with each other, however, a reduction in distance between optical paths of lights reflected by the total ref lectlon mirror 31 permits the dot chains to be substantially continuous with each other in the main scanning direction on the record medium 7 while being arranged in a row, so that operation as in Fig. 2 may be take place. It is a matter of course that driving of the first and. second fluorescent luminous tubes 1 and 2 and movement of the recording medium 7 relative to the head may be carried out in synchronism with each other, to thereby permit the two dot chains to be fully coincident with each other in the sub-scanning direction.

Referring now to Fig. 7, a sixth embodiment of an optical printer head according to the present invention is illustrated. An optical printer head of the Illustrated embodiment is so constructed that three structure units each constituted by an optical printer head constructed as in Fig. 6 are arranged in a row in a sub-scanning direction. The thus-constructed three structure units are provided with three kinds of red (R), green (G) and blue (B) filters 11R, 11G and 11B different In color, respectively, resulting in providing an RGB head module.

In each of the embodiments described above, the fluorescent luminous tube is used as a light source. However, it is a matter of course that any other suitable light source is effectively applied to the present invention.

In each of the embodiments described above, the luminous dot chain of each of the fluorescent luminous tubes has luminous dots of a rectangular shape arranged at predetermined intervals in a row. However, a pattern of the chain is not limited to a single row. For example, a plurality of luminous elements each having luminous dots of any desired shape arranged at predetermined intervals in an offset manner in the main scanning direction may be provided. In this instance, the luminous elements may be positionally varied in the main scanning direction so that lights of an offset pattern emitted from the luminous elements are rendered continuous with each other in the main scanning direction on the record medium through the equimagnification image formation element 10 common thereto.

As can be seen from the foregoing, the optical printer head of the present invention Is constructed so as to permit lights emitted from the plural light sources to form an image through the single equi- magnifIcation image formation element common to the light sources. Such co nstruction brings about small-sizIng of the optical printer head.

Also, such construction permits an image to be formed through the single equi-magnifIcation image formation element under the same optical conditions, to thereby prevent misregistratlon between the luminous dots due to any possible optical distortion of the equi-magnification image formation element, resulting In an image obtained being distinct.

Further, the optical prInter head of the present invention reduces a distance between the dot chains for the respective colors, to thereby minimize delayed processing of data and a space in which the head Is moved.

12 C104MS 1. An optical printer head comprising:

a plurality of light sources each including a plurality of luminous dots arranged In an identical pattern; a single equi-magnif ication image formation element arranged in a manner to be common to said light sources; and an optical element arranged in a manner to f ace said light sources and guiding lights emitted f rom said light sources to said equlmagnification image formation element so as to permit the lights to form an image in said pattern while being rendered continuous with each other.

2. An optical printer head as def ined in claim 1, wherein said pattern is formed by arranging said luminous dots at predetermined pitches in at least one row, wherein lights emitted f rom said luminous dots are arranged in at least a row on a record medium while being continuous with each other at predetermined Intervals.

3. An optical printer head as def ined in claim 2. wherein said luminous dots are arranged in a row.

4. An optical printer head as def ined in claim 2. wherein said luminous dots are arranged in an of f set manner.

5. An optical printer head as defined in any one of claims 1 to 4, wherein said optical element is selected from the group consisting of a half mirror, a half mirror prism, a dichroic mirror and a total reflection mirror.

6. An optical printer constructed and arranged substantially as hereinbefore specifically described with reference to and as shown in any of the accompanying drawings.

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