An optical scanner includes a light source to emit irradiation light, a light deflector to scan the irradiation light emitted from the light source in a first scanning direction and in a second scanning direction intersecting with the first scanning direction, a photodetector to detect the irradiation light when the light deflector scans a detection field, and circuitry to turn on the light source in a first irradiation field scanned by the light deflector from the detection field to an end in the first scanning direction and turn on the light source in a second irradiation field scanned by the light deflector from the end in the first scanning direction towards the detection field, and cause an edge of the first irradiation field on the detection field side to move to get close to the detection field from a position away from the detection field.

An optical scanner includes a light source to emit irradiation light, a light deflector to scan the irradiation light emitted from the light source in a first scanning direction and in a second scanning direction intersecting with the first scanning direction, a photodetector to detect the irradiation light when the light deflector scans a detection field, and circuitry to turn on the light source in a first irradiation field scanned by the light deflector from the detection field to an end in the first scanning direction and turn on the light source in a second irradiation field scanned by the light deflector from the end in the first scanning direction towards the detection field, and cause an edge of the first irradiation field on the detection field side to move to get close to the detection field from a position away from the detection field.

A reading device includes a position reference member and a reader. The position reference member has a reference pattern that includes a line extending in a prescribed direction. The position reference member is configured to relatively move in a direction orthogonal to the prescribed direction. The reader includes a plurality of sensor chips, each of the sensor chips including a plurality of pixels. The reference pattern corresponds to each of the sensor chips of the reader.

A reading device includes a position reference member and a reader. The position reference member has a reference pattern that includes a line extending in a prescribed direction. The position reference member is configured to relatively move in a direction orthogonal to the prescribed direction. The reader includes a plurality of sensor chips, each of the sensor chips including a plurality of pixels. The reference pattern corresponds to each of the sensor chips of the reader.

An image reading apparatus that controls relative positions of a carriage and a document in a first direction using a motor, so as to read an image of the document on a line by line basis, the carriage being mounted with an image sensor and a light source. The image reading apparatus detects an amount of movement caused by the motor in the first direction and generates a first trigger signal in response to input of a synchronization signal generated in accordance with the detected amount of movement, the first trigger signal instructing to start accumulation of charge in the image sensor, and, after a predetermined amount of time since the synchronization signal used for generating the first trigger signal is input, generates a second trigger signal, the second trigger signal instructing to end accumulation of the charge being accumulated in the image sensor.

An image reading apparatus that controls relative positions of a carriage and a document in a first direction using a motor, so as to read an image of the document on a line by line basis, the carriage being mounted with an image sensor and a light source. The image reading apparatus detects an amount of movement caused by the motor in the first direction and generates a first trigger signal in response to input of a synchronization signal generated in accordance with the detected amount of movement, the first trigger signal instructing to start accumulation of charge in the image sensor, and, after a predetermined amount of time since the synchronization signal used for generating the first trigger signal is input, generates a second trigger signal, the second trigger signal instructing to end accumulation of the charge being accumulated in the image sensor.

A pixel clock generating device includes a high-frequency clock generator, a comparer, a pixel clock generator, and a value switcher. The high-frequency clock generator is configured to generate a high-frequency clock. The comparer is configured to measure a time interval between a leading-end synchronizing signal and a trailing-end synchronizing signal in a main scanning and calculate an error between the time interval and a target value. The pixel clock generator is configured to generate a pixel clock based on the high-frequency clock and a pixel clock frequency and correct the pixel clock based on the error. The value switcher, including a plurality of groups of values with which the pixel clock is generated, is configured to switch between the plurality of groups of values according to a switching signal after the trailing-end synchronizing signal is inputted, the comparer calculates the error, and the pixel clock generator corrects the pixel clock.

A pixel clock generating device includes a high-frequency clock generator, a comparer, a pixel clock generator, and a value switcher. The high-frequency clock generator is configured to generate a high-frequency clock. The comparer is configured to measure a time interval between a leading-end synchronizing signal and a trailing-end synchronizing signal in a main scanning and calculate an error between the time interval and a target value. The pixel clock generator is configured to generate a pixel clock based on the high-frequency clock and a pixel clock frequency and correct the pixel clock based on the error. The value switcher, including a plurality of groups of values with which the pixel clock is generated, is configured to switch between the plurality of groups of values according to a switching signal after the trailing-end synchronizing signal is inputted, the comparer calculates the error, and the pixel clock generator corrects the pixel clock.

An image processing method includes an image encoding step of encoding data in which one channel in each pixel of image data including a plurality of pixels is configured by 2 bits or more into data in which the one channel is configured by 1 bit, a transfer step of transferring the encoded data to a printing apparatus, and an image decoding step of decoding the encoded data using the printing apparatus, in which, in the image encoding step, flag information indicating whether the pixel is a character or a line image or a photograph is assigned, and in the image decoding step, decoding is performed by selecting a first decoding method or a second decoding method based on the flag information.

An image processing method includes an image encoding step of encoding data in which one channel in each pixel of image data including a plurality of pixels is configured by 2 bits or more into data in which the one channel is configured by 1 bit, a transfer step of transferring the encoded data to a printing apparatus, and an image decoding step of decoding the encoded data using the printing apparatus, in which, in the image encoding step, flag information indicating whether the pixel is a character or a line image or a photograph is assigned, and in the image decoding step, decoding is performed by selecting a first decoding method or a second decoding method based on the flag information.