A protection member is arranged such that the distance from an opening plane of a reception guide to the center of the protection member is half of the distance from the opening plane of the reception guide to the surface of a reception vibration member. In other words, the arrangement position of the protection member is in the center between the opening plane of the reception guide and the surface of the reception vibration member. Accordingly, even if a protection member is arranged, a transmission coefficient is obtained that is equal to a transmission coefficient in the case where no protection member is present.

A protection member is arranged such that the distance from an opening plane of a reception guide to the center of the protection member is half of the distance from the opening plane of the reception guide to the surface of a reception vibration member. In other words, the arrangement position of the protection member is in the center between the opening plane of the reception guide and the surface of the reception vibration member. Accordingly, even if a protection member is arranged, a transmission coefficient is obtained that is equal to a transmission coefficient in the case where no protection member is present.

An image forming apparatus includes an accommodating portion, an image forming unit, a skew correcting portion, a conveyance unit, a detection unit, a re-conveyance unit, and a control unit. The control unit controls the re-conveyance unit such that the re-conveyance unit stops a sheet in the second conveyance path temporarily and starts to convey the sheet at a first timing after a second timing and before a third timing, where the second timing is a timing such that if the sheet is started to convey to the first conveyance path at the second timing, the conveyance unit decelerates the conveyance speed when the sheet reaches to the detection unit, and the third timing is a timing such that if the sheet is started to convey to the first conveyance path at the third timing, the conveyance unit decelerates the conveyance speed when the sheet reaches to the skew correcting portion.

A determination device includes a processor that is used for determining first paper having a surface on which an embossing process is performed and second paper having a surface on which the embossing process is not performed, a light source that irradiates a surface of paper with light, a light detector that receives the light transmitted through the paper and that detects a light transmittance, an ultrasonic transmitter that transmits an ultrasonic wave to the surface of the paper, and an ultrasonic receiver that receives the ultrasonic wave transmitted through the paper and that detects an ultrasonic transmittance, in which the processor is configured to: use an index that is stored in advance in a storage device and that indicates a correlation between the light transmittance and the ultrasonic transmittance in the second paper, and determine whether or not the paper is the first paper or the second paper according to whether or not the light transmittance and the ultrasonic transmittance, which are detected from the paper, are apart from the index by a predetermined threshold value or more.