Electron tube, electron tube module, and optical device

An electron tube comprising:

• a vacuum container that includes a light transmitting substrate and forms a vacuum space;
• a photocathode provided on an inner surface of the light transmitting substrate facing the vacuum space and configured to emit photoelectrons into the vacuum space in response to light incident through the light transmitting substrate;
• an electron detector provided in the vacuum container and configured to detect electrons derived from the photoelectrons;
• and
• a prism bonded to an outer surface of the light transmitting substrate opposite to the inner surface,
• wherein the prism includes:
• a bottom surface bonded to the outer surface of the light transmitting substrate;
• a light incident surface having a light incident portion to which light is incident;
• and
• a light reflecting surface configured to further reflect light, which is incident to the light incident portion and reflected at an interface between the photocathode and the vacuum space, so that the light is incident to the photocathode again,
• the light reflecting surface has an outwardly convex curved surface shape,
• the light incident portion is located inward of an imaginary spherical surface that is along the light reflecting surface, and
• the curved surface shape of the light reflecting surface is a curved surface shape configured in a pseudo manner by a plurality of plane portions.

An electron tube comprising:

• a vacuum container that includes a light transmitting substrate and forms a vacuum space;
• a photocathode provided on an inner surface of the light transmitting substrate facing the vacuum space and configured to emit photoelectrons into the vacuum space in response to light incident through the light transmitting substrate;
• an electron detector provided in the vacuum container and configured to detect electrons derived from the photoelectrons;
• and
• a prism bonded to an outer surface of the light transmitting substrate opposite to the inner surface,
• wherein the prism includes:
• a bottom surface bonded to the outer surface of the light transmitting substrate;
• a light incident surface having a light incident portion to which light is incident;
• and
• a light reflecting surface configured to further reflect light, which is incident to the light incident portion and reflected at an interface between the photocathode and the vacuum space, so that the light is incident to the photocathode again,
• the light reflecting surface has an outwardly convex curved surface shape,
• the light incident portion is located inward of an imaginary spherical surface that is along the light reflecting surface, and
• the light incident portion has an outwardly convex curved surface shape.

An electron tube comprising:

• a vacuum container that includes a light transmitting substrate and forms a vacuum space;
• a photocathode provided on an inner surface of the light transmitting substrate facing the vacuum space and configured to emit photoelectrons into the vacuum space in response to light incident through the light transmitting substrate;
• an electron detector provided in the vacuum container and configured to detect electrons derived from the photoelectrons;
• and
• a prism bonded to an outer surface of the light transmitting substrate opposite to the inner surface,
• wherein the prism includes:
• a bottom surface bonded to the outer surface of the light transmitting substrate;
• a light incident surface having a light incident portion to which light is incident;
• and
• a light reflecting surface configured to further reflect light, which is incident to the light incident portion and reflected at an interface between the photocathode and the vacuum space, so that the light is incident to the photocathode again,
• the light reflecting surface has an outwardly convex curved surface shape,
• the light incident portion is located inward of an imaginary spherical surface that is along the light reflecting surface, and
• the light incident portion has an inwardly convex curved surface shape.

An electron tube comprising:

• a vacuum container that includes a light transmitting substrate and forms a vacuum space;
• a photocathode provided on an inner surface of the light transmitting substrate facing the vacuum space and configured to emit photoelectrons into the vacuum space in response to light incident through the light transmitting substrate;
• an electron detector provided in the vacuum container and configured to detect electrons derived from the photoelectrons;
• and
• a prism bonded to an outer surface of the light transmitting substrate opposite to the inner surface,
• wherein the prism includes:
• a bottom surface bonded to the outer surface of the light transmitting substrate;
• a light incident surface having a light incident portion to which light is incident;
• and
• a light reflecting surface configured to further reflect light, which is incident to the light incident portion and reflected at an interface between the photocathode and the vacuum space, so that the light is incident to the photocathode again,
• the light reflecting surface has an outwardly convex curved surface shape,
• the light incident portion is located inward of an imaginary spherical surface that is along the light reflecting surface, and
• the light incident portion is constituted by a concave portion opening to a portion of the light incident surface.