| 摘要 |
1. An exposure apparatus comprising: a light-emitting element that emits light for exposure of a photosensitive sheet; a power control portion capable of controlling power to be supplied to said light-emitting element; a time control portion capable of controlling duration of exposure by said light-emitting element; wherein one of said power control portion and said time control portion enabling gradation expression of an image formed on a photosensitive sheet, and the other one enabling correction of an exposure condition in accordance with an environmental change at the time of exposure. 2. An exposure apparatus according to claim 1, wherein the gradation expression is enabled by said time control portion, and the correction of an exposure condition is enabled by said power control portion. 3. An exposure apparatus according to claim 2, further comprising: a temperature sensor that detects a temperature in the vicinity of said light-emitting element; a memory capable of storing data regarding a temperature and the value of current or voltage supplied to said light-emitting element when brightness of said light-emitting element is corrected; said set value control portion being capable of controlling the value of current or voltage to be supplied to said light-emitting element, on the basis of data in said memory and the temperature detected by said temperature sensor. 4. An exposure apparatus according to claim 2, further comprising: a set value control portion capable of changing a value of current or voltage to be supplied from said power control portion to said light-emitting element on the basis of the information regarding sensitivity of a photosensitive sheet; an input portion capable of inputting information regarding sensitivity of a photosensitive sheet. 5. An exposure apparatus according to claim 1, characterized by comprising: a plurality m of groups of said light-emitting elements; a gradation control portion capable of setting a gradation level for gradation expression using one of said power control portion and said time control portion; wherein said gradation control portion having a main gradation level control potion to which gradation information capable of instructing a gradation level whose maximum is an integer n is inputted; and a number of gradation level setting portions into which l number of gradation levels, wherein l is an integer equal to or greater than an integer obtained by dividing the integer n by the integer m, can be set with respect to each group of said light-emitting elements; said main gradation level control means setting a gradation level j + 1 which is higher by 1 than a gradation level j, into said gradation level setting portions pre-set within a kth position, and setting the gradation level j into the other said gradation level setting portions, wherein j is an integer obtained by division of a gradation level i of the gradation information by the integer m, and k is a remainder obtained by the same division. 6. An exposure apparatus according to claim 1, characterized by comprising: four groups of said light-emitting elements; a gradation control portion capable of setting a gradation level for gradation expression using one of said power control portion and said time control portion; wherein said gradation control portion having a main gradation level control portion to which 10-bit gradation information is inputted; and gradation level setting portions into which 8-bit gradation levels can be set with respect to each group of said light-emitting elements; said main gradation level control portion setting higher 8 bits of the gradation information into said gradation level setting portions, and adding 1 to said gradation level setting portion corresponding to the lower 2 bits of the gradation information. 7. An exposure apparatus according to claim 6, characterized in that said gradation control portion is capable of setting a gradation level for gradation expression into said time control portion and controlling the duty of said light-emitting elements. 8. An exposure method for forming an image by exposure of a photosensitive sheet using a light-emitting element, comprising: a first step of detecting a temperature in vicinity of said light-emitting element; a second step of comparing the temperature detected in said first step with a temperature at a time of correction of brightness of said light-emitting element, and setting a value of current or voltage to be supplied to said light-emitting element for exposure on the basis of a value of current or voltage supplied to said light-emitting element at the time of the correction; a third step of setting a duration of exposure by said light-emitting element on the basis of information regarding gradation of an image; and a fourth step of performing exposure by supplying said light-emitting element with the value of current or voltage set in said second step, for the duration of exposure set in said third step. 9. An exposure method according to claim 8, further comprising a step of correcting the value of current or voltage to be supplied to said light-emitting element on the basis of information regarding sensitivity of a photosensitive sheet, following said second step. 10. An exposure method according to claim 8, characterized in that in said third step, a duration of exposure corresponding to a gradation level j + 1 which is higher by 1 than a gradation level j, is set into groups of said light-emitting elements pre-set within a kth position among a plurality m of said light-emitting elements, and a duration of exposure corresponding to the gradation level j is set into the other groups of said light-emitting elements, wherein j is an integer obtained by division of a gradation level i of the gradation information by the integer m, and k is a remainder obtained by the same division. 11. An exposure method according to claim 8, characterized in that said third step comprises a step of setting higher 8 bits of a 10-bit gradation level included in information regarding gradation of an image, into 8-bit gradation level setting portions provided corresponding to four groups of light-emitting elements; and a step of adding 1 to said gradation level setting portion corresponding to the lower 2 bits of the 10-bit gradation level, and that, in said fourth step, the light-emitting elements are turned on at duties corresponding to the values in said gradation level setting portions. 12. A printing apparatus comprising an exposure apparatus as claimed in claim 1, and a conveying apparatus that conveys at least one of a photosensitive sheet and said exposure apparatus at a predetermined timing relative to each other. |
