Method and apparatus for determining focus direction and amount

• US 4,333,007 A
• Filed: 07/10/1980
• Issued: 06/01/1982
• Est. Priority Date: 07/10/1980
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Ogawa, Francis T., Wilwerding, Dennis J., Langlais, Richard A.
• Primary Examiner(s): Nelms, David C.
• Application Number:
  US06/168,225
• Time in Patent Office: 691 Days
• Field of Search: 250/201, 250/204, 250/209, 250/578, 354/25, 356/4, 356/141, 356/152
• US Class Current: 250/201.8
• CPC Class Codes: G02B 7/36 using image sharpness techniques , e.g. image processing techniques for generating autofocus signals image data processing per se G06T; in cameras having a solid state image sensor H04N23/67
• CPC Class Codes: G06F 17/15 Correlation function computation including computation of convolution operations arithmetic circuits for sum of products per se, e.g. multiply-accumulators G06F7/5443; digital filters, e.g. FIR, IIR, adaptive filters H03H17/00

Abstract

A system for determining the range to an object utilizing a plurality of radiation responsive detectors arranged in groupings wherein a first grouping of detectors receives radiation from the object in a first pattern and the second grouping of detectors receives radiation from the object in a second pattern. The patterns move with respect to one another as the distance between the object and the system changes. The range is determined from a determination of the relative position of the patterns by computing where the patterns will coincide if the focusing lens of the system is moved. The output is a signal having a characteristic indicative of the desired direction of motion of the lens and a characteristic indicative of the amount of such motion necessary to produce a proper focus condition.

Claims

1. Apparatus for use with an auto focus system which includes lens means that produces first and second radiation distribution patterns of a scene to be focussed upon, the patterns being similar and in a first relative position when the lens means is in a proper focus position with respect to the scene, the patterns moving away from the first relative position in a first relative direction as the relative position of the scene and the lens means changes from the proper focus position in one direction and the patterns moving away from the first relative position in a second relative direction as the relative position of the scene and the lens means changes from the proper focus position in a direction opposite to the one direction comprising, in combination:

a first plurality of radiation detectors positioned to receive the first radiation distribution pattern, each radiation detector in the first plurality of radiation detectors operable to produce an output indicative of the radiation received thereby;

a second plurality of radiation detectors positioned to receive the second radiation distribution pattern, each radiation detector in the second plurality of radiation detectors operable to produce an output indicative of the radiation received thereby, each radiation detector in the second plurality of radiation detectors having a positionally corresponding radiation detector in the first plurality of radiation detectors so that, when the lens means is in a proper focus position, the output of each radiation detector in the second plurality of radiation detectors is substantially equal to the output of its positionally corresponding radiation detector in the first plurality of radiation detectors;

shift register means connected to receive the outputs of the radiation detectors in the first and second plurality of radiation detectors and operable to shift the outputs of the radiation detectors in one of the plurality of radiation detectors with respect to the outputs of the positionally corresponding radiation detectors in the other of the plurality of radiation detectors;

signal receiving means connected to the shift register means to receive the outputs of the radiation detectors in the first and second plurality of radiation detectors and to produce a plurality of consecutive outputs, V_i, in accordance with the expression ##EQU9## where N is the number of radiation detectors in the first plurality of radiation detectors, n is any number of 1 to N, a represents the output of individual radiation detectors in the first plurality of radiation detectors, b represents the output of individual radiation detectors in the second plurality of radiation detectors and i represents the number of shifts of the shift register from -N/2 to +N/2;

difference means connected to the signal receiving means to receive each two consecutive values of V_i and to produce consecutive outputs, D_i, representative of the difference therebetween;

storage means connected to the difference means to receive and store the outputs D_i ;

comparator means connected to the storage means to receive the latest value of D_i and the largest D_i value previously stored in the storage means and to produce an output D_L representative of the largest D_i compared;

means connecting the comparator means to the storage means to substitute the D_L output for the largest D_i value previously stored in the storage means; and

signal processing means connected to the storage means to receive the largest D_L signal, D_m, when i=+N/2 and to produce an output, L.E., indicative of P(V_m /D_m +i_m) where P is a constant proportional to the distance between radiation detectors in the first and second plurality of radiation detectors, and V_m and i_m are the V_i and i values when the D_L value is equal to D_m.

2. Apparatus according to claim 1 wherein the storage means receives and stores the values V_i and i associated with each output D_i and, upon receipt of the output D_L from the comparator means, stores the V_i and i values (V_i and i_L) associated with D_L so that when i=+N/2 the signal processing means will also receive the V_i and i values (V_m and i_m) with which D_m is associated.

3. Apparatus according to claim 1, further including motive means connected to the signal responsive means and to the lens means and operable to move the lens means in accordance with the output L.E.

4. Apparatus according to claim 2, further including motive means connected to the signal responsive means and to the lens means and operable to move the lens means in accordance with the output L.E.

6. The method of claim 3 further including the following step:

Step 13--presenting the resulting signal L.E. to a motive device to position the lens of the camera in a first direction or a second direction in accordance with the sign of L.E. and by an amount dependent on the size of L.E. so that it occupies the proper focus position.

5. The method for determining the direction and amount of lens of a camera should be moved in order to achieve the proper focus position with respect to a remote object which camera includes lens means that produces first and second radiation distribution patterns of the scene, and a plurality N of positionally corresponding radiation detector pairs, a first detector in each pair being identified as an a detector and the second detector in each pair being identified as a b detector and the detector pairs being mounted to receive radiation from the remote scene with the a detectors receiving radiation in the first radiation distribution pattern and the b detectors receiving radiation in the second radiation distribution pattern comprising the following steps:

Step 1--presenting the outputs from all of the a and b detectors to a memory for storage;

Step 2--shifting the outputs of the b detectors a number of positions with respect to the a positionally corresponding detectors in a first direction;

Step 3--determining a value V_i from the shifted outputs of the b detectors and the outputs of the a detectors in accordance with the equation ##EQU10## where i represents the number of shifts of the b detector outputs with respect to the positionally corresponding a detector outputs;

Step 4--storing the value V_i and the i value with which it is associated;

Step 5--shifting the b outputs one position in a direction opposite to the first direction with respect to the positionally corresponding a outputs;

Step 6--determining a new V_i from the above equation (1) and storing the new V_i and i values;

Step 7--subtracting the first and second V_i values to obtain a first D_i value;

Step 8--storing the value D_i and the V_i and i values with which it is associated;

Step 9--repeating Steps 5 through 8 to obtain a new D_i value;

Step 10--comparing the old D_i and the new D_i value to determine which is largest and storing the largest D_i value and the corresponding V_i and i values with which it is associated;

Step 11--repeating Steps 5 through 10 until i=+N/2 at which time the largest D value, D_m, and the V_i and i values with which it is associated (V_m and i_m) are stored; and

Step 12--determining the lens extension value from the equation

space="preserve" listing-type="equation">L.E.=P(V.sub.m /D.sub.m +i.sub.m)

where P is a constant representing the lens extension per shift.

7. Apparatus for use in an auto focus system which includes first plurality, N, of radiation detectors A₁, A₂, A₃ . . . A_n mounted in a first array with each detector operable to produce an output a₁, a₂, a₃ . . . a_n representative of the radiation received thereby, a second plurality of radiation detectors B₁, B₂, B₃ . . . B_n mounted in a second array with each detector operable to produce an output b₁, b₂, b₃ . . . b_n representative of the radiation received thereby, radiation transmissive means for transmitting radiation from a remote object so as to produce first and second radiation patterns at the first and second arrays respectively, when said radiation transmission means is in a first position relative to the remote object the first and second patterns produce substantially equal radiation on detectors having the same subscripts in the first and second arrays, when said radiation transmission means is in a position other than the first position relative to the remote object the first and second patterns change so that the detectors with the same subscripts in the first and second arrays normally receive different radiation, the improvement comprising:

shifting means connected to receive the outputs a₁, a₂, a₃ . . . a_n and b₁, b₂, b₃ . . . b_n and operable to produce an output signal in which the outputs b₁, b₂, b₃ . . . b_n are shifted with respect to the outputs a₁, a₂, a₃ . . . a_n ;

signal producing means connected to the shifting means and operable to produce a signal, i, causing consecutive shifts of the outputs b₁, b₂, b₃ . . . b_n from a first position to a second position;

first computer means connected to the shift means and to the signal producing means to receive the outputs therefrom and operable to produce an output signal V_i for each value of i according to the equation ##EQU11## difference means connected to receive the output of the first computer means and operable to produce an output signal D_i indicative of the difference between successive V_i outputs from the computer means;

comparator means connected to the difference means to receive the D_i signal therefrom and operable to produce an output signal D_m indicative of the largest value of a D_i signal received from the difference means; and

second computer means connected to the comparator means to receive the D_m signal and to produce an output signal, L.E. according to the equation L.E.=P(V_m /D_m +i_m) where P is a constant and V_m and i_m are V_i and i values used in obtaining D_m.

8. Apparatus according to claim 7 wherein the first computer means produces a second output indicative of the value i associated with V_i, the difference means receives both V_i and i from the first computer means and produces second and third outputs V_i and i respectively associated with D_i, the comparator means received D_i, V_i and i from the difference means and produces second and third output signals V_m and i_m respectively and the second comparator means receives D_m, V_m and i_m from the comparator means.

9. Apparatus according to claim 7 further including motive means connected to the second computer means to receive the L.E. signal and operable to position the radiation transmissive means in accordance therewith.

10. Apparatus according to claim 8 further including motive means connected to the second comparator means to receive the L.E. signal and operable to position the radiation transmissive means in accordance therewith.