CA1084577A - Optical printer with character magnification - Google Patents
Optical printer with character magnificationInfo
- Publication number
- CA1084577A CA1084577A CA250,015A CA250015A CA1084577A CA 1084577 A CA1084577 A CA 1084577A CA 250015 A CA250015 A CA 250015A CA 1084577 A CA1084577 A CA 1084577A
- Authority
- CA
- Canada
- Prior art keywords
- character
- scanning
- auxiliary
- main
- printed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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- Mechanical Optical Scanning Systems (AREA)
- Fax Reproducing Arrangements (AREA)
- Facsimile Scanning Arrangements (AREA)
- Laser Beam Printer (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An optical printer comprises a mechanical scanner, which scans a modulated light beam across a recording medium in a main or horizontal direction at a fixed speed. An acousto-optic deflector performs auxiliary scanning of the beam in a vertical direction onto the mechanical scanner at a constant rate and is connected to a deflection signa? generator. The deflection signal generator adjusts the stroke length of auxiliary scan in accordance with the ma?nification ratio and simult?neously adjusts the frequency of aux???ary scanning by the reciprocal of the magnification rate of the character to be printed. Furthermore, optical density is maintained constant for various character sizes by providing auxiliary gate pulses proportional to the square of the relative character size, which are AND gated with a character information signal to effect a light modulation signal for modulating the beam.
An optical printer comprises a mechanical scanner, which scans a modulated light beam across a recording medium in a main or horizontal direction at a fixed speed. An acousto-optic deflector performs auxiliary scanning of the beam in a vertical direction onto the mechanical scanner at a constant rate and is connected to a deflection signa? generator. The deflection signal generator adjusts the stroke length of auxiliary scan in accordance with the ma?nification ratio and simult?neously adjusts the frequency of aux???ary scanning by the reciprocal of the magnification rate of the character to be printed. Furthermore, optical density is maintained constant for various character sizes by providing auxiliary gate pulses proportional to the square of the relative character size, which are AND gated with a character information signal to effect a light modulation signal for modulating the beam.
Description
10~4S'~'7 , DESCRIPTION OF THE INVENTION
The present inven ion relates to an optical printer capable of changing a character magnification ratio.
It is an object of an aspect of this invention to provide a scanning mechanism with a means for changing the magnification ratio of characters without changing the speed of the scanning mechanism.
It is an object of an aspect of this invention to change the magnification ratio of characters without changing the speed of the scanning mechanism while maintaining the optical density of the various size characters constant.
In accordance with this invention there is provided an optical printer comprising: an illumination source generating a beam of light, a recording medium, a main scanning member in the path of said beam for scanning said beam at a fixed speed in a main direction across said recording medium, an acousto-optic deflector located in the path of said beam between said main scanning member and said illumination source, said deflector scanning said beam onto said main scanning member in a direc:tion transverse to said main direction, a deflection signa] generator operatively connected to said deflector for adjusting the stroke length of auxiliary scanning in accordance with the magnification ratio of a character to be printed and for simultaneously adjusting the frequency of auxiliary scanning by the reciprocal of the magnification ratio of the character to be printed.
This invention will become apparent from the following description with reference to the drawings wherein:
Figure 1 illustrates a conventional optical printer;
Figure 2 illustrates a character composed of a dot matrix;
Figure 3 is a waveform chart showing the timing of main and auxiliary scanning in the printer of Figure l;
~ - 2 -Figure 4 is a waveform chart showing the timing of ~uxiliary scanning and light modulation in the printer of . Figure l;
' Figure 5 is a schematic illustration of an optical printer embodying the present inven~ion;
Figure 6 illustrates a printing pattern obtained by ' the printer of Figure 5; and Figure 7 is a waveform chart showing the timing of ' each operation in the printer of Figure 5.
With the recent trend toward attainment of high-speed ' printers for use in computer output units and other similar units, the optical printer based on the combination of an optical charac-~, ter generator and electrophotography has come to be employed.
Generally,,the optical printer is composed in such a m~ner as shown in Figure 1. A light beam emitted from a laser light source (1) ., i, - 2a -. , 0845'77 is modulated by a light modulator (2) in accordance with infor-mation. The light modulator (2) consists of, for example, a pockel-type cell which is made of potassium dehydrogen phosphate and serves to convert periodically a refractive index in propor-tion to the level of an applied voltage representing an electricsignal. After modulation, scanning in the column or vertical printing direction (hereinafter referred to as auxiliary scanning) is performed by a light deflector (3) consisting of an acousto- ;
optic element, and simultaneously scanning in the row or hori-zontal printing direction (hereinafter referred to as main scanning) is performed by a mechanical deflector (4) consisting of a rotary mirror or galvano-mirror. The light beam thus deflected is projected through a suitable optical system (5) onto a sensitive member (6), such as sensitive drum or photo-15 graphic plate of a printing mechanism based on electrostatic ~ `
photography, so that a character pattern is recorded. In the above-mentioned printer, when the height of auxiliary scanning is set to the height of a character to be printed, an optical image covering characters of one line is formed by one main 2Q scanning. For example, in case a character pattern consists of a K-row, L-column dot matrix as illustrated in Figure 2, when printing N characters per line, auxiliary scanning is executed L x N times during one main scanning. The relationship between main scanning and auxiliary scanning is shown in Figure 3.
In the meanwhile, the waveform modulated by the light modulator (2) is synchronized with the auxiliary scanning as plotted in Figure 4. With regard to a video clock signal serving as reference timing for modulation of the light beam, K pulses, equal in number to the horizontal rows of the matrix constituting 3a one character, are generated per auxiliary scanning so that the light beam is modulated dot by dot synchronously with the video - 10~4577 clock pulses, and one vertical column of the character is printed by the light beam modulation corresponding to K dots.
One character is printed by repeating this procedure L times (corresponding to the number of columns in the character matrix), and one-line printing is achieved by repeating the one-character printing N times. In the aforementioned optical printer, how-ever, it is extremely difficult to change the character size halfway through the line during printing for the following reasons. That is, the size of a character to be printed is changed generally by changing the main and auxiliary scanning speeds. However, changing the character size in this manner presents technica] difficulties in making a substantial change in the main scanning speed due to the inertia of the mechanical deflector.
The present invention accomplishes changing the cha-racter size by setting the main scanning speed of a mechanical deflector to a constant predetermined value and changing a printing magnification ratio through changes in the auxiliary scanning period and the auxiliary scanning stroke length, there-by providing an improved printer which is capable of changing the printing magnification ratio without undergoing any undesir-able effect from inertia of the mechanical deflector.
The present invention is described in detail with reference to an exemplary embodiment as shown in Figures 5 through 7. When characters to be printed and a printing magni-fication ratio are specified by a computer (not shown), a video clock generating circuit (7) generates video clock pulses of a period proportional to the magnification ratio in the auxiliary scanning direction for the characters to be printed. In Figure 6, the time from tl to t2 denotes normal-size printing; the time from t2 to t3 is a space period between characters for adjustment - - 108~57`7 of a printing interval; and the time from t3 to t4 shows the auxiliary scan length doubled wherein a character is magnified twice both vertically and horizontally as compared with the normal-size printing. In this case, the video clock period is ; 5 increased twofold in accordance with the printing magnification ratio for the character, which is doubled both vertically and horizontally. The main scanning speed of a mechanical deflec-tor (4) is maintained at a constant speed, and the auxiliary scanning speed of an acousto-optic deflector (3) also remains constant. Thus, the dot-to-dot interval in the auxiliary scanning direction (vertical) is increased to double the time required for the normal-size auxiliary scanning, thereby doubl-ing also the dot-to-dot interval in the main scanning direction (horizontal) to effect printing of a character, which is magni-fied twice both vertically and horizontally. The video clockpulses produced from the video clock generator (7) are applied to a dot matrix character information signal generator (8), and a modulator driving circuit (9) operates synchronously with the video clock pulses during a period of the presence of character information signals in accordance with the corresponding print-ing pattern so that the light beam emitted from the laser light source ~1) is modulated by the light modulator (2) connected to the modulator driving circuit (9).
In the meantime, the video clock pulses are applied also to a deflection signal generator (11), and the deflection signal therefrom is converted into a suitable frequency by a voltage-to-frequency converter (10) and then is applied to the acousto-optic deflector (3) so as to deflect the light beam in the auxiliary scanning direction (vertical).
When the printing magnification ratio is increased twice both vertically and horizontally, the character area - : . ~
multiplies substantially four times, but the optical density of the character is reduced to one half because the printing time per dot, which is proportional to the extended time in the column direction of one character, increases only twice. Even though a fixed optical density is retained in the individual dots printed, it is not desirable that the density of the charac-ter as a whole change with a change in the printing magnification ratio. Therefore, an auxiliary gate pulse generator (12) (see Figure 5) provides auxiliary gate pulses proportional to the -square of the relative character size (see Figure 7). A light modulation signal is projected according to the AND of the auxiliary gate pulse and the character information signal, and light modulation is executed in accordance with the light modu-lator signal thereby maintaining the apparent character density at a fixed value.
As described in detail above, the feature of changing a printing magnification ratio while holding the main scanning speed of the mechanical deflector constant renders the present invention capable of achieving a change of the character size 2Q anywhere on a line, which has been difficult heretofore due to overcoming the inertia of the mechanical deflector. Thus, the provision of, for example, an eight-point character font in the printer renders possible the printing of any desired character size such as 14-point, 16-point, etc.
Accordingly, the present invention facilitates reading of different character fonts and, furthermore, ensures high reliability of a printer since the component parts of a mechan-ical deflector including the rotary mirror are actuated at a fixed speed without being affected by jitter due to varying speeds.
It is to be understood that although the light modula-..... . . .
tor and the acousto-optic deflector employed in the foregoing embodiment are individual and independent of each other, the acousto-optic deflector may be so composed as to combine the function of the light modulator, and the light beam is not limited to laser light alone but may be any visible light as long as it is of a fixed wavelength.
.
The present inven ion relates to an optical printer capable of changing a character magnification ratio.
It is an object of an aspect of this invention to provide a scanning mechanism with a means for changing the magnification ratio of characters without changing the speed of the scanning mechanism.
It is an object of an aspect of this invention to change the magnification ratio of characters without changing the speed of the scanning mechanism while maintaining the optical density of the various size characters constant.
In accordance with this invention there is provided an optical printer comprising: an illumination source generating a beam of light, a recording medium, a main scanning member in the path of said beam for scanning said beam at a fixed speed in a main direction across said recording medium, an acousto-optic deflector located in the path of said beam between said main scanning member and said illumination source, said deflector scanning said beam onto said main scanning member in a direc:tion transverse to said main direction, a deflection signa] generator operatively connected to said deflector for adjusting the stroke length of auxiliary scanning in accordance with the magnification ratio of a character to be printed and for simultaneously adjusting the frequency of auxiliary scanning by the reciprocal of the magnification ratio of the character to be printed.
This invention will become apparent from the following description with reference to the drawings wherein:
Figure 1 illustrates a conventional optical printer;
Figure 2 illustrates a character composed of a dot matrix;
Figure 3 is a waveform chart showing the timing of main and auxiliary scanning in the printer of Figure l;
~ - 2 -Figure 4 is a waveform chart showing the timing of ~uxiliary scanning and light modulation in the printer of . Figure l;
' Figure 5 is a schematic illustration of an optical printer embodying the present inven~ion;
Figure 6 illustrates a printing pattern obtained by ' the printer of Figure 5; and Figure 7 is a waveform chart showing the timing of ' each operation in the printer of Figure 5.
With the recent trend toward attainment of high-speed ' printers for use in computer output units and other similar units, the optical printer based on the combination of an optical charac-~, ter generator and electrophotography has come to be employed.
Generally,,the optical printer is composed in such a m~ner as shown in Figure 1. A light beam emitted from a laser light source (1) ., i, - 2a -. , 0845'77 is modulated by a light modulator (2) in accordance with infor-mation. The light modulator (2) consists of, for example, a pockel-type cell which is made of potassium dehydrogen phosphate and serves to convert periodically a refractive index in propor-tion to the level of an applied voltage representing an electricsignal. After modulation, scanning in the column or vertical printing direction (hereinafter referred to as auxiliary scanning) is performed by a light deflector (3) consisting of an acousto- ;
optic element, and simultaneously scanning in the row or hori-zontal printing direction (hereinafter referred to as main scanning) is performed by a mechanical deflector (4) consisting of a rotary mirror or galvano-mirror. The light beam thus deflected is projected through a suitable optical system (5) onto a sensitive member (6), such as sensitive drum or photo-15 graphic plate of a printing mechanism based on electrostatic ~ `
photography, so that a character pattern is recorded. In the above-mentioned printer, when the height of auxiliary scanning is set to the height of a character to be printed, an optical image covering characters of one line is formed by one main 2Q scanning. For example, in case a character pattern consists of a K-row, L-column dot matrix as illustrated in Figure 2, when printing N characters per line, auxiliary scanning is executed L x N times during one main scanning. The relationship between main scanning and auxiliary scanning is shown in Figure 3.
In the meanwhile, the waveform modulated by the light modulator (2) is synchronized with the auxiliary scanning as plotted in Figure 4. With regard to a video clock signal serving as reference timing for modulation of the light beam, K pulses, equal in number to the horizontal rows of the matrix constituting 3a one character, are generated per auxiliary scanning so that the light beam is modulated dot by dot synchronously with the video - 10~4577 clock pulses, and one vertical column of the character is printed by the light beam modulation corresponding to K dots.
One character is printed by repeating this procedure L times (corresponding to the number of columns in the character matrix), and one-line printing is achieved by repeating the one-character printing N times. In the aforementioned optical printer, how-ever, it is extremely difficult to change the character size halfway through the line during printing for the following reasons. That is, the size of a character to be printed is changed generally by changing the main and auxiliary scanning speeds. However, changing the character size in this manner presents technica] difficulties in making a substantial change in the main scanning speed due to the inertia of the mechanical deflector.
The present invention accomplishes changing the cha-racter size by setting the main scanning speed of a mechanical deflector to a constant predetermined value and changing a printing magnification ratio through changes in the auxiliary scanning period and the auxiliary scanning stroke length, there-by providing an improved printer which is capable of changing the printing magnification ratio without undergoing any undesir-able effect from inertia of the mechanical deflector.
The present invention is described in detail with reference to an exemplary embodiment as shown in Figures 5 through 7. When characters to be printed and a printing magni-fication ratio are specified by a computer (not shown), a video clock generating circuit (7) generates video clock pulses of a period proportional to the magnification ratio in the auxiliary scanning direction for the characters to be printed. In Figure 6, the time from tl to t2 denotes normal-size printing; the time from t2 to t3 is a space period between characters for adjustment - - 108~57`7 of a printing interval; and the time from t3 to t4 shows the auxiliary scan length doubled wherein a character is magnified twice both vertically and horizontally as compared with the normal-size printing. In this case, the video clock period is ; 5 increased twofold in accordance with the printing magnification ratio for the character, which is doubled both vertically and horizontally. The main scanning speed of a mechanical deflec-tor (4) is maintained at a constant speed, and the auxiliary scanning speed of an acousto-optic deflector (3) also remains constant. Thus, the dot-to-dot interval in the auxiliary scanning direction (vertical) is increased to double the time required for the normal-size auxiliary scanning, thereby doubl-ing also the dot-to-dot interval in the main scanning direction (horizontal) to effect printing of a character, which is magni-fied twice both vertically and horizontally. The video clockpulses produced from the video clock generator (7) are applied to a dot matrix character information signal generator (8), and a modulator driving circuit (9) operates synchronously with the video clock pulses during a period of the presence of character information signals in accordance with the corresponding print-ing pattern so that the light beam emitted from the laser light source ~1) is modulated by the light modulator (2) connected to the modulator driving circuit (9).
In the meantime, the video clock pulses are applied also to a deflection signal generator (11), and the deflection signal therefrom is converted into a suitable frequency by a voltage-to-frequency converter (10) and then is applied to the acousto-optic deflector (3) so as to deflect the light beam in the auxiliary scanning direction (vertical).
When the printing magnification ratio is increased twice both vertically and horizontally, the character area - : . ~
multiplies substantially four times, but the optical density of the character is reduced to one half because the printing time per dot, which is proportional to the extended time in the column direction of one character, increases only twice. Even though a fixed optical density is retained in the individual dots printed, it is not desirable that the density of the charac-ter as a whole change with a change in the printing magnification ratio. Therefore, an auxiliary gate pulse generator (12) (see Figure 5) provides auxiliary gate pulses proportional to the -square of the relative character size (see Figure 7). A light modulation signal is projected according to the AND of the auxiliary gate pulse and the character information signal, and light modulation is executed in accordance with the light modu-lator signal thereby maintaining the apparent character density at a fixed value.
As described in detail above, the feature of changing a printing magnification ratio while holding the main scanning speed of the mechanical deflector constant renders the present invention capable of achieving a change of the character size 2Q anywhere on a line, which has been difficult heretofore due to overcoming the inertia of the mechanical deflector. Thus, the provision of, for example, an eight-point character font in the printer renders possible the printing of any desired character size such as 14-point, 16-point, etc.
Accordingly, the present invention facilitates reading of different character fonts and, furthermore, ensures high reliability of a printer since the component parts of a mechan-ical deflector including the rotary mirror are actuated at a fixed speed without being affected by jitter due to varying speeds.
It is to be understood that although the light modula-..... . . .
tor and the acousto-optic deflector employed in the foregoing embodiment are individual and independent of each other, the acousto-optic deflector may be so composed as to combine the function of the light modulator, and the light beam is not limited to laser light alone but may be any visible light as long as it is of a fixed wavelength.
.
Claims (2)
1. An optical printer comprising: an illumination source generating a beam of light, a recording medium, a main scanning member in the path of said beam for scanning said beam at a fixed speed in a main direction across said recording medium, an acousto-optic deflector located in the path of said beam between said main scanning member and said illumination source, said deflector scanning said beam onto said main scan-ning member in a direction transverse to said main direction, a deflection signal generator operatively connected to said deflec-tor for adjusting the stroke length of auxiliary scanning in accordance with the magnification ratio of a character to be printed and for simultaneously adjusting the frequency of auxiliary scanning by the reciprocal of the magnification ratio of the character to be printed.
2. An optical system as recited in Claim 1 further comprising a modulator for modulating said beam, means for pro-viding an auxiliary gate pulse proportional to the square of a relative character size, means for generating a character infor-mation signal, and means AND gating said gate pulse and said character information signal to provide a light modulation signal to said modulator to maintain the optical density of various size characters constant.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP50042778A JPS588628B2 (en) | 1975-04-10 | 1975-04-10 | Kogaku Teki Inji Souchi |
| JP50-042778 | 1975-04-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1084577A true CA1084577A (en) | 1980-08-26 |
Family
ID=12645412
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA250,015A Expired CA1084577A (en) | 1975-04-10 | 1976-04-12 | Optical printer with character magnification |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS588628B2 (en) |
| CA (1) | CA1084577A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5557479A (en) * | 1978-10-24 | 1980-04-28 | Fujitsu Ltd | Deformed letter producing method |
-
1975
- 1975-04-10 JP JP50042778A patent/JPS588628B2/en not_active Expired
-
1976
- 1976-04-12 CA CA250,015A patent/CA1084577A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS588628B2 (en) | 1983-02-16 |
| JPS51117827A (en) | 1976-10-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |