Abstract: When one of first to third power supply circuits breaks down, a change-over switch performs switching of electrical connection such that drive voltage is allowed to be supplied from normal one of the first to third power supply circuits also to one of the inkjet heads connected to the breakdown power supply circuit. Consequently, the power supply circuits are partially sharable with a plurality of inkjet heads, causing no necessity of stopping the apparatus for replacing one breakdown power supply circuit. As a result, suppression in decrease of throughput of the apparatus is obtainable.

Abstract: When one of first to third power supply circuits breaks down, a change-over switch performs switching of electrical connection such that drive voltage is allowed to be supplied from normal one of the first to third power supply circuits also to one of the inkjet heads connected to the breakdown power supply circuit. Consequently, the power supply circuits are partially sharable with a plurality of inkjet heads, causing no necessity of stopping the apparatus for replacing one breakdown power supply circuit. As a result, suppression in decrease of throughput of the apparatus is obtainable.

Abstract: In an image recording apparatus, shift times for shifting switching timings of light modulator elements are obtained so that rise times (U1) after input of output start signals to driving elements connected to respective light modulator elements of a spatial light modulator and fall times (D1) after input of output stop signals become a constant target rise time (U2) and a constant target fall time (D2). This makes it possible to suppress unevenness of the rise times and the fall times after correction of light amounts even if light modulator elements where the rise times and the fall times change by correction of light amounts are used and consequently, an image can be appropriately recorded without a complicate apparatus.

Abstract: In an image recording apparatus, shift times for shifting switching timings of light modulator elements are obtained so that rise times (U1) after input of output start signals to driving elements connected to respective light modulator elements of a spatial light modulator and fall times (D1) after input of output stop signals become a constant target rise time (U2) and a constant target fall time (D2). This makes it possible to suppress unevenness of the rise times and the fall times after correction of light amounts even if light modulator elements where the rise times and the fall times change by correction of light amounts are used and consequently, an image can be appropriately recorded without a complicate apparatus.

Abstract: Halftone dots are formed on the basis of three sets of screen pattern data assigned to the to a same combined area, in which a plurality of halftone dots are to be formed. The three sets of screen pattern data have different threshold values assigned to respective pixels in the combined area, and are stored in SPM's (101-116). Eight SPM's (Screen Pattern memory units) store a first set of the screen pattern data, six SPM's store a second one, end two SPM's store a third one. One of the sixteen SPM's is randomly selected with respect to each pixel, whereby one of the threshold values (D.sub.s) stored in the selected SPM is compared with an iamge signal (V.sub.1). A dot signal indicating whether or not each pixel is solid is produced on the basis of the comparison. Accordingly, a grid-like pattern of halftone dots to be seen in a highlight area or a shadow area is prevented.