Bias lighting in a radiographic apparatus and method

A method of enhancing a video image of an x-ray shadowgraph of a subject in a radiographic apparatus, the method comprising:

• (a) illuminating the target of a television camera;
• (b) generating a first optional image of an x-ray shadowgraph of the subject and focusing the optical image on the target of the television camera;
• (c) ceasing the illumination of said target;
• and then
• (d) generating a video signal of the image focused on said target.

The method as set forth in claim 13 further comprising the steps of:

• (a) introducing a relatively small amount of an x-ray opaque contrast agent into the subject;
• (b) illuminating said target of the television camera;
• (c) generating an optical image of an x-ray shadowgraph through the subject and introduced x-ray opaque contrast agent and focusing the optical image on said target;
• then
• (d) ceasing the illumination of said target of the television camera;
• (e) generating a second video signal of the image focused on said target;
• (f) digitizing said second video signal;
• (g) storing said second digitized video signal in a second digital memory;
• and
• (h) subtractively combining said first and second stored, digitized video signals to produce a differential video signal.

A radiographic apparatus comprising:

• (a) a radiation source for irradiating an examined object with penetrating radiation such as x-radiation;
• (b) radiation converting means for converting the x-radiation into an optical image, said radiation converting means being disposed to receive from said radiation source x-radiation which has traversed the examined object;
• (c) a television camera optically connected with said radiation converting means for converting the optical image into a video signal, said television camera having a transient non-linear response in the absence of significant illumination of said television camera prior to receiving a first optical image;
• (d) bias lighting means for pre-illuminating the television camera prior to receiving said first optical image with a sufficient intensity of light to minimize substantially the transient non-linear portion of the response of said television camera;
• and
• (e) timing means for timing the operation of said bias lighting means, said timing means shutting off said bias lighting means as or before said television camera receives the first optical image which is to be converted to the video signal.

A radiographic apparatus comprising:

• (a) a radiation source for irradiating an examined object with penetrating radiation such as x-radiation;
• (b) radiation converting means for converting the x-radiation into an optical image, said radiation converting means being disposed to receive from said radiation source x-radiation which has traversed the examined object;
• (c) a television camera optically connected with said radiation converting means for converting the optical image into a video signal, said television camera having a transient non-linear response in the absence of significant illumination of said television camera prior to receiving a first optical image;
• (d) bias lighting means for pre-illuminating the television camera prior to receiving said first optical image with a sufficient intensity of light to minimize substantially the transient non-linear portion of the response of said television camera;
• and
• (e) means for adding an offset signal to said video signal which offset signal is related to the amplitude of the video signal generated when said television camera is illuminated by said bias lighting means.