BACKGROUND

Radiation detectors may be devices used to measure the flux, spatial distribution, spectrum or other properties of radiations.

Radiation detectors may be used for many applications. One important application is imaging. Radiation imaging is a radiography technique and can be used to reveal the internal structure of a non-uniformly composed and opaque object such as the human body.

Early radiation detectors for imaging include photographic plates and photographic films. A photographic plate may be a glass plate with a coating of light-sensitive emulsion. Although photographic plates were replaced by photographic films, they may still be used in special situations due to the superior quality they offer and their extreme stability. A photographic film may be a plastic film (e.g., a strip or sheet) with a coating of light-sensitive emulsion.

In the 1980s, photostimulable phosphor plates (PSP plates) became available. A PSP plate may contain a phosphor material with color centers in its lattice. When the PSP plate is exposed to radiation, electrons excited by radiation are trapped in the color centers until they are stimulated by a laser beam scanning over the plate surface. As the plate is scanned by laser, trapped excited electrons give off light, which is collected by a photomultiplier tube. The collected light is converted into a digital image. In contrast to photographic plates and photographic films, PSP plates can be reused.

Another kind of radiation detectors are radiation image intensifiers. Components of a radiation image intensifier are usually sealed in a vacuum. In contrast to photographic plates, photographic films, and PSP plates, radiation image intensifiers may produce real-time images, i.e., do not require post-exposure processing to produce images. Radiation first hits an input phosphor (e.g., cesium iodide) and is converted to visible light. The visible light then hits a photocathode (e.g., a thin metal layer containing cesium and antimony compounds) and causes emission of electrons. The number of emitted electrons is proportional to the intensity of the incident radiation. The emitted electrons are projected, through electron optics, onto an output phosphor and cause the output phosphor to produce a visible-light image.

Scintillators operate somewhat similarly to radiation image intensifiers in that scintillators (e.g., sodium iodide) absorb radiation and emit visible light, which can then be detected by a suitable image sensor for visible light. In scintillators, the visible light spreads and scatters in all directions and thus reduces spatial resolution. Reducing the scintillator thickness helps to improve the spatial resolution but also reduces absorption of radiation. A scintillator thus has to strike a compromise between absorption efficiency and resolution.

Semiconductor radiation detectors largely overcome this problem by direct conversion of radiation into electric signals. A semiconductor radiation detector may include a semiconductor layer that absorbs radiation in wavelengths of interest. When a particle of radiation is absorbed in the semiconductor layer, multiple charge carriers (e.g., electrons and holes) are generated and swept under an electric field towards electrical contacts on the semiconductor layer.

SUMMARY

Disclosed herein is an image sensor comprising: a plurality of radiation detectors; a mask with a plurality of radiation transmitting zones and a radiation blocking zone; and an actuator configured to move the plurality of radiation detectors from a first position to a second position and to move the mask from a third position to a fourth position; wherein while the radiation detectors are at the first position and the mask is at the third position and while the radiation detectors are at the second position and the mask is at the fourth position, the radiation blocking zone blocks radiation from a radiation source that would otherwise incident on a dead zone of the image sensor and the radiation transmitting zones allow at least a portion of radiation from the radiation source that would incident on active areas of the image sensor to pass through.

According to an embodiment, the image sensor is configured to capture, by using the radiation detectors, an image of a first portion of a scene when the radiation detectors are at the first position and the image sensor is configure to capture, by using the radiation detectors, an image of a second portion of a scene when the radiation detectors are at the second position, wherein the image sensor is configured to form an image of the scene by stitching the image of the first portion and the image of the second portion.

According to an embodiment, the plurality of radiation detectors are spaced apart.

According to an embodiment, the image sensor further comprises a shutter configured to block the radiation from the radiation source during movement of the radiation detectors.

According to an embodiment, the actuator comprises a first linear motor and a second linear motor; wherein the first linear motor is configured to move the radiation detectors from the first position to the second position; wherein the second linear motor is configured to move the mask from the third position to the fourth position.

According to an embodiment, the actuator comprises a third linear motor and a linkage; wherein the third linear motor is configured to move radiation detectors from the first position to the second position; wherein the linkage couples the mask to the radiation detectors such that movement of the radiation detectors from the first position to the second position causes the mask to move from the third position to the fourth position.

According to an embodiment, the actuator comprises a third linear motor and a linkage; the third linear motor is configured to move the mask move from the third position to the fourth position; wherein the linkage couples the radiation detectors to the mask such that movement of the mask from the third position to the fourth position causes the radiation detectors to move from the first position to the second position.

According to an embodiment, the actuator comprises a third linear motor and a linkage; wherein the third linear motor is configured to drive the linkage; wherein the linkage causes the mask to move from the third position to the fourth position and causes the radiation detectors to move from the first position to the second position.

According to an embodiment, the actuator comprises a step motor and a transmission; wherein the step motor is configured to move radiation detectors from the first position to the second position and to drive the transmission; wherein the transmission is configured to move the mask from the third position to the fourth position.

According to an embodiment, at least some of the plurality of radiation detectors are arranged in staggered rows.

According to an embodiment, radiation detectors in a same row are uniform in size; wherein a distance between two neighboring radiation detectors in a same row is greater than a width of one radiation detector in the same row in an extending direction of the row and is less than twice that width.

According to an embodiment, active areas of the radiation detectors tessellate the scene at the positions.

According to an embodiment, at least some of the plurality of radiation detectors comprise multiple layers of detectors.

According to an embodiment, at least some of the plurality of radiation detectors are rectangular in shape.

According to an embodiment, at least some of the plurality of radiation detectors are hexagonal in shape.

According to an embodiment, at least one of the plurality of radiation detectors comprises a radiation absorption layer and an electronics layer; wherein the radiation absorption layer comprises an electrode; wherein the electronics layer comprises an electronics system; wherein the electronics system comprises: a first voltage comparator configured to compare a voltage of the electrode to a first threshold, a second voltage comparator configured to compare the voltage to a second threshold, a counter configured to register a number of particles of radiation reaching the radiation absorption layer, and a controller; wherein the controller is configured to start a time delay from a time at which the first voltage comparator determines that an absolute value of the voltage equals or exceeds an absolute value of the first threshold; wherein the controller is configured to activate the second voltage comparator during the time delay; wherein the controller is configured to cause the number registered by the counter to increase by one, if the second voltage comparator determines that an absolute value of the voltage equals or exceeds an absolute value of the second threshold.

According to an embodiment, the electronics system further comprises a capacitor module electrically connected to the electrode, wherein the capacitor module is configured to collect charge carriers from the electrode.

According to an embodiment, the controller is configured to activate the second voltage comparator at a beginning or expiration of the time delay.

According to an embodiment, the electronics system further comprises a voltmeter, wherein the controller is configured to cause the voltmeter to measure the voltage upon expiration of the time delay.

According to an embodiment, the controller is configured to determine energy of a particle of radiation based on a value of the voltage measured upon expiration of the time delay.

According to an embodiment, the controller is configured to connect the electrode to an electrical ground.

According to an embodiment, a rate of change of the voltage is substantially zero at expiration of the time delay.

According to an embodiment, a rate of change of the voltage is substantially non-zero at expiration of the time delay.

Disclosed herein is a system comprising the image sensor described herein and a radiation source, wherein the system is configured to perform radiography on human chest or abdomen.

Disclosed herein is a system comprising the image sensor described herein and a radiation source, wherein the system is configured to perform radiography on human mouth.

Disclosed herein is a cargo scanning or non-intrusive inspection (NII) system, comprising the image sensor described herein and a radiation source, wherein the cargo scanning or non-intrusive inspection (NII) system is configured to form an image using radiation transmitted through an object inspected.

Disclosed herein is a full-body scanner system comprising the image sensor described herein and a radiation source.

Disclosed herein is a radiation computed tomography (radiation CT) system comprising the image sensor described herein and a radiation source.

Disclosed herein is an electron microscope comprising the image sensor described herein, an electron source and an electronic optical system.

Disclosed herein is a system comprising the image sensor described herein, wherein the system is a radiation telescope, or a radiation microscopy, or wherein the system is configured to perform mammography, industrial defect detection, microradiography, casting inspection, weld inspection, or digital subtraction angiography.

