  Multiphoton-ionized electrons are born into a strong light field that will
determine their short-term future. By controlling the infrared beam, we enable
atoms or molecules to generate extreme ultraviolet (XUV) pulses and synthesize
attosecond pulses - the shortest controlled events ever produced. Here we show
that a weak obliquely incident beam imposes an optical grating on the
fundamental beam, resulting in a spatially modulated attosecond pulse. We
observe the modulation on a spectrally resolved near-field XUV image, encoding
all information of the spectral phase of the recollision electron and,
therefore, the attosecond pulse produced by structureless atoms. Near-field
imaging is an efficient method for measuring the duration of attosecond pulses,
especially important for soft X-ray pulses created in helium. For more complex
systems, it includes auto ionization and giant plasmon resonances.
