Image reading device with light noise reduction characteristics

An image forming apparatus, comprising:

• a document feeder;
• a photoconductive drum;
• a developing device;
• a fixing device;
• an image reading device, comprising:
• a lens mirror array including a plurality of optical elements integrally arrayed in a first direction, each of the optical elements including, on a surface thereof, an incident-side lens surface that transmits and converges reflected light from a read surface, an upstream-side reflection surface that reflects light made incident via the incident-side lens surface, a downstream-side reflection surface that reflects the light reflected on the upstream-side reflection surface, an emission-side lens surface that transmits and converges the light reflected on the downstream-side reflection surface and images the light on an imaging surface, and a stray light reflection surface that is inclined with respect to an imaginary surface orthogonal to the first direction and disposed continuously to a peripheral edge of the upstream-side reflection surface and reflects, with respect to effective light from the read surface imaged on the imaging surface, wherein stray light constitutes noise within the effective light in a direction separating in a second direction orthogonal to the first direction;
• a photoelectric conversion section including the imaging surface and configured to
• receive, on the imaging surface, the reflected light from the read surface guided by the lens mirror array,
• photoelectrically convert the received reflected light, and
• output the reflected light as image information;
• and
• a diaphragm disposed between the read surface and the incident-side lens surface of the lens mirror array, including a slit-like opening section extending in the first direction that defines width in the second direction of the reflected light such that the reflected light from the read surface is made incident within a range of an effective width in the second direction of the incident-side lens surface, and including a surface that is in contact with the lens mirror array on both sides in the second direction of the opening section;
• and
• a paper discharge tray.