公开(公告)号：US4943716A

公开(公告)日：1990-07-24

申请号：US298430

申请日：1989-01-18

申请人： Souji Ichikawa ,  Hideki Oka ,  Naoyoshi Terao ,  Seiji Sakagami

发明人： Souji Ichikawa ,  Hideki Oka ,  Naoyoshi Terao ,  Seiji Sakagami

IPC分类号： G01D5/36

CPC分类号： G01D5/36

摘要： In a diffraction type optical displacement encoder using a diffractive light source and having a main scale grating and an index scale grating, a light-receiving element receives two rays satisfying a relationship concerning the lengths of light paths at the rays between the light source and the index scale grating, and the width of the light receiving element, wherein the difference between the path length of each ray is approximately equal to an integral multiple of the square of the pitch of the main scale grating divided by the wavelength of the light source, and the width of the light receiving element, measured as the distance between the impingement points of the two rays at the index scale, is integrally related to the difference in ray path lengths and the angle of the impinging rays due to an offsetting of the light-receiving element. In a second aspect of the invention, two light-receiving elements receive two rays satisfying a similar relationship, and a sum of outputs of the respective light-receiving elements is made to be a detection signal. Or, in an optical encoder using a collimated lighting system, an index scale is leaned (inclined) toward a main scale by a predetermined value. With any one of these arrangements, a component of variation in the detection signal due to a geometric image can be offset or integrated to be removed, whereby the dependence of an S/N ratio of the detection signal on the grating gap can be avoided. Furthermore, in a reflection type encoder using a diffusive light source, diffused rays from a point light source is focused by a condensing lens to produce a secondary point light source and this secondary point light source is positioned in a plane where second gratings corresponding to an index scale are formed. With this arrangement, a collimator lens can be dispensed with, so that the encoder can be rendered compact in size. Furthermore, the respective elements can be easily supported and positioned.

公开(公告)号：US4985623A

公开(公告)日：1991-01-15

申请号：US490389

申请日：1990-03-08

申请人： Souji Ichikawa ,  Hideki Oka ,  Naoyoshi Terao ,  Seiji Sakagami

发明人： Souji Ichikawa ,  Hideki Oka ,  Naoyoshi Terao ,  Seiji Sakagami

IPC分类号： G01D5/36

CPC分类号： G01D5/36

摘要： In an optical encoder using a collimated lighting system, an index scale is inclined toward a main scale by a predetermined value. With this arrangement, a component of variation in the detection signal due to variations in the grating gap can be offset or integrated to be removed from a geometric image of the first grating in the detection signal, whereby the dependence of an S/N ratio of the detection signal on the grating gap can be avoided.

公开(公告)号：US4983825A

公开(公告)日：1991-01-08

申请号：US490463

申请日：1990-03-08

申请人： Souji Ichikawa ,  Hideki Oka ,  Naoyoshi Terao ,  Seiji Sakagami

发明人： Souji Ichikawa ,  Hideki Oka ,  Naoyoshi Terao ,  Seiji Sakagami

IPC分类号： G01D5/36

CPC分类号： G01D5/36

摘要： In a reflection type encoder having a main scale and an index scale with first and second gratings, respectively, and using a diffusing light source, diffused rays from a point light source are focused by a condensing lens to produce a secondary point light source positioned on a plane defined by the second gratings of the index scale. With this arrangement, a collimator lens can be dispensed with, so that the encoder can be rendered compact in size. Furthermore, the respective elements can be easily supported and positioned.