OPTICS FOR HIGH SENSITIVITY COLOR TELEVISION CAMERA

• US 3,718,751 A
• Filed: 10/12/1970
• Issued: 02/27/1973
• Est. Priority Date: 10/12/1970
• Status: Expired due to Term

• Current Assignee: Donald D. Kline, John K. Landre, Marc W. Broemmelsiek
• Original Assignee: Donald D. Kline, John K. Landre, Marc W. Broemmelsiek
• Inventors: Landre, John K., Kline, Donald D., Broemmelsiek, Marc W.
• Primary Examiner(s): Richardson, Robert L.
• Application Number:
  US05/079,848
• Time in Patent Office: 869 Days
• Field of Search: 178/5.4C,5.4TC,5.4,7.86 350/166,169,171
• US Class Current: 348/339
• CPC Class Codes: H04N 23/16 Optical arrangements associated therewith, e.g. for beam-splitting or for colour correction

Abstract

An optical system for high sensitivity television cameras employing parallel blue, green and red television tubes with one of the tubes being aligned with an optical aperture of the camera. A trichroic filter splits off a green image portion of the image received from the aperture and directs it via a green mirror to the green television tube. The remainder of the received image is passed to a dichroic filter which has a transmission cutoff point in the light wave band reflected by the trichroic filter and which reflects the blue image portion via a trim mirror to the blue television tube and transmits the red image portion to the red television tube. The reflecting surfaces of the filters and the mirrors are disposed at 45* to the incident light and are constructed so that their spectral transmission-reflection characteristics are insensitive to light polarization. The tubes, filters, mirrors and other components of the optical system are mounted to a relatively massive optical bench preventing image distortions and movement of the components under temperature changes, vibration, shock and the like. Means are also provided to operate the camera aperture, neutral density and color filters that can be swung into the light path through the camera from an end of the camera remote from the aperture.

Claims

1. In a color television camera having a lens for forming an image, a first television tube for receiving a green image portion from the lens, a second television tube for receiving a red image portion from the lens and a third television tube for receiving a blue image portion from the lens, the improvement comprising:

a first dichroic filter placed in the optical path from the lens for separation of the green image portion from the lens image, the first dichroic filter having a reflecting surface oriented at an angle of about 45* with respect to incoming light, the first dichroic filter being constructed so that its spectral transmission and reflection characteristics remain substantially constant when incoming light of wavelengths in the neighborhood of the reflection cut off wavelength of the first dichroic filter is polarized, a second dichroic filter disposed optically downstream of the first dichroic filter and receiving a remainder of the lens image, the second dichroic filter separating the remainder into the blue and red image portions, and means transmitting the respective image portions to the corresponding tubes.

2. A television camera according to claim 1 wherein the the first and second dichroic filters are linearly aligned with the lens, wherein each filter reflects one image portion, and including reflecting means directing the reflected image in a direction parallel to the optical path, and means positioning the tubes parallel to the optical path to substantially uniformly subject the tubes to earth magnetism.

3. A television camera in accordance with claim 2 wherein the reflecting means for the green image portion comprises mirror means for deflecting the green image portion only disposed in the path of the green image portion reflected by the first dichroic filter to thereby eliminate ghost images resulting from the reflection of light other than green light by a surface of the first dichroic filter opposite a green reflecting surface of the first filter.

4. A television camera according to claim 1 wherein the second dichroic filter reflects the blue image portion and passes the red image portion, and including means for trimming a part of the blue image portion having a wavelength close to a wavelength of the green image portion reflected by the first dichroic filter.

5. A high sensitivity color television camera usable under low light intensity conditions for the production of color television signals from light of minimal polarization and with substantially no color signal imbalances due to the effects of relatively large magnetic fields acting on television tubes of the camera comprising:

a rigid optical bench, parallel image intensifying television tubes mounted to the bench for minimizing the greatest distance between the tubes and assuring uniform effects of large magnetic fields on tube output signals, means forming a magnetic shield about the tubes, optical aperture defining means carried by the bench for forming an image, means carried by the bench for the removal of light of the wave lengths other than wave lengths to be received by the tubes, first means optically downstream of the removal means for splitting off a first light image of a wave length intermediate the upper and lower wave lengths defined by the light removal means and directing the first split-off light image to the corresponding tube, second means optically downstream of the first means and splitting light waves received from the first means into light images having first trim edges defined by the upper and lower wave lengths passing the light removal means, having second trim edges defined by thE reflection characteristic of the first split-off means and directing the light images to second and third tubes, and means mounting the split-off means to the bench.

6. A color television camera according to claim 5 wherein at least the first split-off means comprises filter means having a reflective surface for the reflection of a color image with closely controlled trim edges, and wherein the reflective surface is constructed so that the spectral transmission and reflection characteristic of the split-off means is substantially insensitive to light polarization whereby the light wave band of the reflected and transmitted images is substantially unaffected when incoming light includes polarized light and the angle of incidence of the incoming light on the reflecting surface is about 45*.

7. A color television camera according to claim 6 including means eliminating a double reflection effect from at least one of the first and second split-off means to prevent the formation of ghost images in the tubes.

8. A color television camera in accordance with claim 5 wherein the television tubes are secondary electron conduction vidicon tubes.

9. A color television camera according to claim 5 including filter means and means for selectively passing the filter means into the optical path of the aperture defining means for filtering light of a predetermined wave length.

10. A color television camera according to claim 5 including reflectors between the first and second split-off means and at least some of the tubes for directing color light images to such tubes, and wherein the first and second split-off means comprises a filter reflecting light of a certain wave length and permitting the passage of other light, and wherein the reflecting surfaces of the filters and the reflectors are disposed at 45* to the incident light.

11. A color television camera comprising:

an optical bench, means mounted to the camera defining an optical camera aperture and an optical axis through the camera, a blue image receiving television tube, a green image receiving television tube and a red image receiving television tube, means mounting the tubes to the bench, orienting the tube axes parallel to each other and aligning one of the tubes with the camera axis, first and second light filter means reflecting light of a certain color band and passing light of another color band, the first and second filter means being spaced along the camera axis, means mounting the filter means to the bench and positioning the filter means for reflection of a light color band for one of the tubes and passage of a remainder of the image striking the filter, means positioned in an optical path of reflection from the filter means directing reflected light color bands to corresponding tubes, and means mounting the mirror means to the bench.

12. A color television camera according to claim 11 including magnetic shielding placed over the television tubes and secured to the bench.

13. A color television camera according to claim 11 including a band pass filter aligned with the camera axis, mounted to the bench and preventing the passage of ultraviolet and infrared light to the first and second filter means.

14. A color television camera according to claim 11 wherein the mirror means opposite at least one of the filter means comprises a reflector reflecting the respective incoming color image only to the corresponding color tube and thus eliminating the transmission to the tube of a ghost image reflected by the opposing filter means.

15. A color television camera according to claim 11 wherein one of the filter means reflects a light color band comprising the blue color image of the image projected by the optical camera aperture defining means, and wherein the mirror means includes means trimming a relatively long wavelength portion of the reflected blue image.

16. A color television camera according to claim 11 including neutral density filters mounted to a rotaTable support, means mounting the support to the optical bench so that the neutral density filters can be aligned with the camera axis optically upstream of the filter means, and means for operating the neutral density filter mounting means from adjacent an end of the optical bench opposite the end adjacent the aperture defining means.

17. A color television camera according to claim 16 including at least one color filter mounted to rotatable means, means securing the rotatable means to the bench optically upstream of the filter means so that the color filter can be aligned with the camera axis, and means coupled to the rotatable means for actuating the rotatable means from adjacent the bench end remote from the aperture defining means.

18. A color television camera in accordance with claim 17 including a fine adjustment lens disposed in the camera axis upstream of the filter means, means mounting the fine adjustment lens to the bench, and means for adjusting the fine adjustment lens from adjacent the optical bench end remote from the aperture defining means.