Improved method and apparatus for generating halftone images

Claim 2

An improved method for generating a half-tone having a desired screen angle and screen frequency using a recording means having a radiation beam, of variable intensity, aimed at a target spot on a recording medium, the target spot being moved relative to the recording medium in first and second directions defining a first coordinate system, wherein the recording medium is divided into a number of periodically repeating screen meshes forming a net on which locations are defined by a second coordinate system and wherein one of the coordinates of the second coordinate system is disposed at an angle β with respect to the first recording direction, wherein each of these screen meshes is divided into a number of microdots, and wherein the relative position of the target spot in any given mesh containing the spot is defined by relative second coordinates determined as a function of the spot's position in the coordinates of the first coordinate system wherein the improvement comprises: providing a lookup table that contains, at addressable locations, output data defining the desired intensity of the radiation beam as a function of input information, including the relative second coordinates and picture intensity data, such input information defining an address in the table, addressing the lookup table on the basis of such information, and using the output data of the lookup table to affect the intensity of the radiation beam.

Claim 3

A method according to claim 1, wherein the radiation beam is a laser beam, its intensity is controlled by a modulator, and the step of using the output data of the lookup data to affect the intensity of the recording beam includes supplying the output of the lookup table to the modulator.

Claim 4

A method according to claim 1, wherein the step of providing a lookup table includes providing a lookup table containing output data that defines the desired radiation beam intensity as one of at least three intensities.

Claim 5

A method according to claim 1, wherein the step of providing a lookup table includes providing such a table containing output data as a function of input information that further includes at least one of (a) a desired dot shape set and (b) a random number.

Claim 6

A method of according to claim 2, wherein the step of providing a lookup table includes providing such a table containing output data as a function of input information that further includes at least one of (a) a desired dot shape set and (b) a random number.

Claim 7

A method according to claim 3, wherein the step of providing a lookup table includes providing such a table containing output data as a function of input information that further includes at least one of (a) a desired dot shape set and (b) a random number.

Claim 8

An improved method for generating a half-tone having a desired screen angle and screen frequency using a recording means having a radiation beam, of variable intensity, aimed at a target spot on a recording medium, the target spot being moved relative to the recording medium in first and second directions, wherein the recording medium is divided into a number of periodically repeating screen portions, each portion including at least one mesh, forming a net of meshes, the meshes having an axis disposed at an angle β with respect to the first recording direction, wherein each of these portions is divided into a number of microdots accessed by a pair of portion coordinates, and wherein the relative position of the target spot in any given portion containing the spot is defined by relative portion coordinates, wherein the improvement comprises: providing a lookup table that contains, at addressable locations, output data defining the desired intensity of the radiation beam, as one of at least three intensities as a function of input information, including the relative portion coordinates and picture intensity data, such input information defining an address in the table, addressing the lookup table on the basis of such information, and using the output data of the lookup table to affect the intensity of the radiation beam.

Claim 9

An improved method for generating a half-tone having a desired screen angle and screen frequency using a recording means having a radiation beam, of variable intensity, aimed at a target spot on a recording medium, the target spot being moved relative to the recording medium in first and second directions, wherein the recording medium is divided into a number of periodically repeating screen portions, each portion including at least one mesh, forming a net of meshes, the meshes having an axis disposed at an angle β with respect to the first recording direction, wherein each of these portions is divided into a number of microdots accessed by a pair of portion coordinates, and wherein the relative position of the target spot in any given portion containing the spot is defined by relative portion coordinates, wherein the improvement comprises: providing a lookup table that contains, at addressable locations, output data defining the desired intensity of the radiation beam, as one of at least three intensities as a function of input information, including the relative portion coordinates and picture intensity data, such input information defining an address in the table, addressing the lookup table on the basis of such information, and using the output data of the lookup table to affect the intensity of the radiation beam.

Claim 10

A method according to claim 7, wherein the radiation beam is a laser beam, its intensity is controlled by a modulator, and the step of using the output data of the lookup data to affect the intensity of the recording beam includes supplying the output of the lookup table to the modulator.

Claim 11

A method according to claim 7, wherein β has a rational tangent.

Claim 12

A method according to claim 7, wherein the step of providing a lookup table includes providing such a table containing output data as a function of input information that further includes at least one of (a) a desired dot shape set and (b) a random number.

Claim 13

A method of according to claim 9, wherein the step of providing a lookup table includes providing such a table containing output data as a function of input information that further includes at least one of (a) a desired dot shape set and (b) a random number.

Claim 14

An improved apparatus for generating a half-tone having a desired screen angle and screen frequency using a recording means having a radiation beam, of variable intensity, aimed at a target spot on a recording medium, the target spot being moved relative to the recording medium in first and second directions defining a first coordinate system, wherein the recording medium is divided into a number of periodically repeating screen meshes forming a net on which locations are defined by a second coordinate system and wherein one of the coordinates of the second coordinate system is disposed at an angle β with respect to the first recording direction, wherein each of these screen meshes is divided into a number of microdots, and wherein the relative position of the target spot in any given mesh containing the spot is defined by relative second coordinates is determined as a function of its position in the coordinates of the first coordinate system, wherein the improvement comprises: storage means for storing, at addressable locations, output data defining the desired intensity of the radiation beam as a function of input information, including the second coordinates and picture intensity data, such input information defining an address in the storage means, address means for addressing the storage means on the basis of such information, and affect means, in communication with the storage means, for affecting the intensity of the radiation beam based on the output data of the storage means.

Claim 15

An improved apparatus for generating a half-tone having a desired screen angle and screen frequency using a recording means having a radiation beam, of variable intensity, aimed at a target spot on a recording medium, the target spot being moved relative to the recording medium in first and second directions defining a first coordinate system, wherein the recording medium is divided into a number of periodically repeating screen meshes forming a net on which locations are defined by a second coordinate system and wherein one of the coordinates of the second coordinate system is disposed at an angle β with respect to the first recording direction, wherein each of these screen meshes is divided into a number of microdots, and wherein the relative position of the target spot in any given mesh containing the spot is defined by relative second coordinates is determined as a function of its position in the coordinates of the first coordinate system, wherein the improvement comprises: storage means for storing, at addressable locations, output data defining the desired intensity of the radiation beam as a function of input information, including the second coordinates and picture intensity data, such input information defining an address in the storage means, address means for addressing the storage means on the basis of such information, and affect means, in communication with the storage means, for affecting the intensity of the radiation beam based on the output data of the storage means.

Claim 16

An apparatus according to claim 12, wherein the storage means includes means for storing output data that defines the desired radiation beam intensity as one of at least three intensities.

Claim 17

An apparatus according to claim 12, wherein the radiation beam is a laser beam, and the affect means includes a modulator for controlling the intensity of the laser beam.

Claim 18

An apparatus according to claim 12, wherein the storage means includes means for storing output data as a function of input information that further includes at least one of (a) a desired dot shape set and (b) a random number.

Claim 19

An apparatus according to claim 13, wherein the storage means includes means for storing output data as a function of input information that further includes at least one of (a) a desired dot shape set and (b) a random number.

Claim 20

An apparatus according to claim 14, wherein the storage means includes means for storing output data that defines the desired radiation beam intensity as one of at least three intensities.

Claim 21

An improved apparatus for generating a half-tone having a desired screen angle and screen frequency using a recording means having a radiation beam, of variable intensity, aimed at a target spot on a recording medium, the target spot being moved relative to the recording medium in first and second directions, wherein the recording medium is divided into a number of periodically repeating screen portions, each portion including at least one mesh forming a net of meshes, the meshes having an axis disposed at an angle β with respect to the first recording direction, wherein each of these portions is divided into a number of microdots, accessed by a pair of portion coordinates, and wherein the relative position of the target spot in any given portion containing the spot is defined by relative portion coordinates, wherein the improvement comprises: storage means for storing, at addressable locations, output data defining the desired intensity of the radiation beam, as one of at least three intensities, as a function of input information, including the relative portion coordinates and picture intensity data, such input information defining an address in the storage means, address means for addressing the storage means on the basis of such information, and affect means, in communication with the storage means, for affecting the intensity of the radiation beam based on the output data of the storage means.

Claim 22

An improved apparatus for generating a half-tone having a desired screen angle and screen frequency using a recording means having a radiation beam, of variable intensity, aimed at a target spot on a recording medium, the target spot being moved relative to the recording medium in first and second directions, wherein the recording medium is divided into a number of periodically repeating screen portions, each portion including at least one mesh forming a net of meshes, the meshes having an axis disposed at an angle β with respect to the first recording direction, wherein each of these portions is divided into a number of microdots, accessed by a pair of portion coordinates, and wherein the relative position of the target spot in any given portion containing the spot is defined by relative portion coordinates, wherein the improvement comprises: storage means for storing, at addressable locations, output data defining the desired intensity of the radiation beam, as one of at least three intensities, as a function of input information, including the relative portion coordinates and picture intensity data, such input information defining an address in the storage means, address means for addressing the storage means on the basis of such information, and affect means, in communication with the storage means, for affecting the intensity of the radiation beam based on the output data of the storage means.

Claim 23

An apparatus according to claim 18, wherein the radiation beam is a laser beam, and the affect means includes a modulator for controlling the intensity of the laser beam.

Claim 24

An apparatus according to claim 18, wherein β has a rational tangent.

Claim 25

An apparatus according to claim 18, wherein the storage means includes means for storing output data as a function of input information that further includes at least one of (a) a desired dot shape set and (b) a random number.

Claim 26

An apparatus according to claim 20, wherein the storage means includes means for storing output data as a function of input information that further includes at least one of (a) a desired dot shape set and (b) a random number.