Method for automatically setting up a television camera

Method for automatically setting up a television camera by means of a microcomputer. The setup is effected in two separate steps, a test pattern being used in each step. An external test pattern is present on a test chart in front of the camera and an internal test pattern is present in the camera in the optical path between a camera lens system and a camera pickup arrangement. During the setup with the internal test pattern, the lens system is optically blocked and correction information is stored in a memory. During or after the setup with the external test pattern, the correction information associated with the internal test pattern is subtracted from the correction information associated with the external test pattern. The resulting correction difference information is lens correction information and is stored in a memory associated with the lens system. Now, the camera operator can prepare for scene recording without an external The internal test pattern in the camera memory and the lens memory together produce the correction for an optimum setup.

BACKGROUND OF THE INVENTION 
The invention relates to a method for automatically setting up a television 
camera by means of a test pattern. The optical information originating 
from the test pattern is converted by a pickup arrangement in the camera 
into electronic information. The electronic information is compared in at 
least one microcomputer with reference information to produce difference. 
information. The difference information is converted as an error 
information into correction information which is stored in a camera 
memory. The correction information is extracted from the camera memory and 
used to correct picture information supplied by the pickup arrangement, 
resulting in minimal information. The invention also relates to a 
television camera suitable for the method, to a suitable memory and lens 
system, and to a suitable memory. 
Such a method is disclosed in U.S. Pat. No. 4,285,004 (Morrison, et al), in 
which the test pattern present on a test chart is positioned in front of a 
color television camera. The optical information originating from the test 
chart is imaged via an optical path incorporating a lens system and a 
color splitting prism, onto the pickup arrangement which comprises three 
pickup devices. Each device produces a color video signal. After the 
setup, scan correction signals are applied to two of the pickup devices or 
to all three pickup devices. As a result, of an optimum raster 
registration is obtained in the television picture on display. In 
addition, during the setup shading errors at black level and the maximum 
video value are corrected and a gamma correction is obtained by applying 
correction signals to video signal processing circuits. 
In practice, setting up a television camera by means of a test chart which 
is to be positioned at some distance in front of the camera is very 
troublesome for the camera operator. Positioning the test chart, which 
must always be at hand, in the proper position and under the proper 
illumination is time-consuming and annoying for the camera operator. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide a camera setup method in which, 
in normal circumstances, the camera operator does not need to set up a 
test chart in front of the camera during the preparation for scene 
recording. 
According to the invention, a setup method which precedes the normal 
preparations for scene recording includes two separate steps in which an 
external and an internal test pattern are used separately. During the 
setup with the external test pattern, the external test pattern is present 
on a test chart in front of the camera. During the setup with the internal 
test pattern, the internal test pattern is present in the camera in the 
optical path between a lens system of the camera and the pickup 
arrangement. The separate setups with the external and internal test 
patterns are effected with a nonblocked optical path and a blocked optical 
path, respectively in which the lens system is incorporated. 
At least the correction information associated with the internal test 
pattern is stored in the camera memory. The correction information 
associated with the internal test pattern is substracted from the 
correction information associated with the external test pattern, and the 
resulting correction difference information (which relates to at least the 
lens system) is stored in a lens memory. The camera memory and lens memory 
together produce the correction information for correction with minimal 
error. 
In the described method the setup is effected in two steps. In normal 
circumstances, the camera operator needs to setup only the internal test 
pattern contained in the camera. This internal test pattern may be 
arranged in the optical path between the (optically blocked) lens system 
and the camera pickup arrangement in the form of a hingeable slide which 
is illuminated from a light source. Alternatively, this slide may be 
projected into the optical path by means of a mirror. 
Prior to the present invention each lens system for the camera required a 
separate setup by means of the external test pattern to be positioned in 
front of the camera. The difference between the correction information 
associated with the different lens systems and determined by means of the 
external test pattern, and the correction information associated with the 
internal test pattern is stored by the supplier in a like number of, for 
example, digital lens memories. As a result each lens system had its own 
lens memory with correction information. 
For setting up the camera during preparation for (i) to scene recording, 
the camera operator now only needs to place the lens memory associated 
with the lens system in the camera or to choose one of the incorporated 
memories, (ii) to block the optical path containing the lens system, and 
(iii) to position the test pattern present in the camera in the 
illuminated optical path, in order to make the automatic setup operative. 
When the setup is fully automatic, the camera operator needs only to 
operate one single knob at the camera. 
The described method accomplishes a separation of functions. For each lens 
system, a setup with the external and internal test patterns needs to be 
performed only once, and the associated lens memory is loaded with the 
correction difference information. Thereafter during use of the camera 
only the internal test pattern in the camera is required for setup. 
The loading of the memory associated with the lens system may be performed 
by the lens system supplier or by the camera operator himself. In 
addition, if so desired, the lens memory information may be refreshed at 
intervals so that ageing phenomena in the lens system is corrected. 
The lens memory may be, for example, a digital memory. To form the 
correction information associated with the lens system, the correction 
information associated with the external test pattern provided on the test 
chart may be temporarily stored in an auxiliary memory. This has the 
advantage that the loading of the lens memory need not to be performed 
simultaneously with the generation of the correction information 
associated with the test chart pattern. Because of the temporary storage 
the correction difference information can be formed at a desired, 
arbitrary moment by the microcomputer. Thereafter the auxiliary memory may 
be erased. 
In addition to the fact that in the described method the lens memory 
contains the correction information associated with the lens system, this 
memory may contain further correction information as regard errors in the 
blocked portion of the optical path in which the lens system is 
incorporated. 
The method according to the invention can be used with a television camera 
having a camera memory employed by the camera operator during the setup 
operation which is part of the preparation for scene recording. The camera 
also has a lens memory containing a correction information which is at 
least associated with the lens system used at that moment at the camera. 
When the camera is suitable for studio and outdoor recordings and the 
required lens systems have been supplied with the camera, the fact that a 
lens system with range extension features has a different characteristic 
than the same lens system without this feature is taken account of. It 
appears that eight lens memories for storing of the different items of 
correction information is sufficient. 
A memory and lens system based on the use of a method according to the 
invention can be supplied to the user of the camera. After the lens system 
has been arranged at the camera and the lens memory with the correction 
information associated with the lens system has been arranged at the 
microcomputer or a choice between the incorporated memories has been made, 
the camera operator can perform the setup with the internal test pattern. 
In practice, the related lens systems and lens memories with correction 
information will be provided with identification features, either 
electronic features or nonelectronic features. 
The method results in a memory containing correction information which fits 
in with the associated lens system for a color television camera. During 
recording, the color television camera operates, for example, with the 
green, red and blue light components of the light coming from a scene to 
be televised. The digital lens memory may contain correction information 
about, for example, geometry, registration or raster registration, shading 
distortion, optical focussing and the video signal. The geometry 
correction is either of the pincushion type or of the barrel type, and may 
be characterized by one single coefficient in the digital memory. The 
optical focussing correction may be written in the memory with three 
coefficients. When the registration error is expressed as a dimensional 
error in red and blue with respect to green, two coefficients are required 
for correction. The shading distortion can be corrected by means of, for 
example, a horizontal and vertical, parabolic and sawtooth-shaped 
correction in red, green and blue, so that twelve coefficients are 
required in the lens memory. Higher order corrections result in more 
coefficients. For the video signal correction, red and blue amplifying and 
black level corrections, which require four coefficients, may be used. 
With the described automatic setup by means of the external and internal 
test patterns, the external test chart pattern can be setup automatically 
or manually. The external and internal test patterns must be of identical 
construction. When a television camera user buys a memory and lens system 
in which the lens memory has already been loaded, a matching internal test 
pattern may be used in the setup by the camera operator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1 there is shown an external test pattern 1 present on a test chart 
which is positioned in front of a television camera 2. The optical 
information originating from the test chart is imaged on a pickup 
arrangement 5 via an optical path 3 incorporating a lens system 4. The 
pickup arrangement 5 converts the optical information into electronic 
information which is applied to video processing circuits 6. The 
conversion is effected under the control of scan circuits 7. An output of 
the video processing circuits 6 is connected to an output 8 of the camera 
2. 
For automatic setup of the camera 2, the output of the video processing 
circuits 6 is connected to a (+) input of a stage 9 having a (-) input to 
which reference information is applied. Stage 9 is combined with a 
microcomputer (.mu.C) 10. Output/input terminals of the microcomputer 10 
are denoted by T1, T2 to Tn. By means of the stage 9 and the microcomputer 
10 the difference information present between the (+) and (-) inputs is 
converted as error information into correction information at an output. 
The stage 9 applies the correction information to an input of a camera 
memory 11 through and on/off switch 12. The camera memory 11 has a control 
input/output connected to the terminal T1 of the microcomputer 10. A 
switching input of the switch 12 is connected to the output terminal T2 of 
the microcomputer 10. An output of the camera memory 11 conveying 
correction information is coupled to inputs of the video processing 
circuits 6 and the scan circuits 7. According to an aspect of the 
invention this coupling comprises an adding circuit 13. The adding circuit 
13 has two (+) inputs connected to the output of the camera memory 11 and 
a lens memory 14, respectively. 
The output of the stage 9 with the correction information is coupled to an 
input of the lens memory 14 through an on/off switch 15 and a subtracting 
circuit 16. The switch 15 has a switching input connected to the terminal 
T3. The lens memory 14 has a control input/output connected to the 
terminal T4. The substracting circuit 16 has a (+) input connected to the 
switch 15 and a (-) input connected to an output of the camera memory 11. 
As described, an auxiliary separate memory 17 may be provided between the 
output of the stage 9 and the (+) input of the subtracting circuit 16 
which has a control input/output connected to the terminal T5. 
In order to produce the correction difference information in that the 
subtracting circuit 16, an internal test pattern 18 and an optical path 
blocking means 19 are provided in the camera 2. A (mechanical) coupling 20 
is shown in the FIGURE. The internal test pattern 18 may be in the form of 
a hingeable slide which is illuminated from a light source 21. The 
blocking means 19 may alternatively be provided between the lens system 4 
and the hingeable slide. 
In FIG. 1 the switch 15 is shown in the closed state. During this state the 
information coming from the external test pattern 1 is processed in the 
camera 2 in the described way. Prior to this state the internal test 
pattern 18 was inserted in the optical path 3 behind the lens system 4, 
the optical path 3 being blocked by the optical path blocking means 19. In 
this prior state the switch 12 was closed. The result is that setup 
achieved in the described two steps.