| 摘要 |
PURPOSE:To perform diagnosis on all of the LED array elements at high speed by dividing a receiving part into a plurality, and selecting elements from every division one by one at the same time. CONSTITUTION:All of the LED elements are divided into a plurality of groups sequen tially, each group consists of (n) pieces of elements, while all of the groups count up (m). In the first process, (1,1), (2,1),..., (m,1) are selected, and each of these (m) pieces is made to illuminate simultaneously, while in the second scanning, (1,2), (2,2),..., (m,2) are selected, and are made to emit light for the diagnosis of all of the elements of the same group. The light-electricity conversion for a malfunctioning LED detector 4 results from this process; short-size photo-diodes 41, 42, 43, 4(m) are cascade-connected and constitution is formed in the manner that all over the whole length of the LED array, each element is provided with light receiving surface, and when any divided group is found to be non-conductive, its output terminals 41A and 41B do not generate electro-motive force because of the cascade connection. As for the timewise response of the photdiode, connection capacity of each short-sized photo-di ode is represented by C, it is reduced to C/n between the detection terminals 41A and 41B. Based upon this detected value change, a comparator 6 performs the judge ment whether the article is good or not. |
